Custom Tube Amp, Transformer from Ampeg, Sunn, or Hiwatt??

[SpankyPants]

I'm trying to design a stereo tube amp, so I'll need two output transformers. My current AIMS amp only uses 2 KT-88's, and it's the loudest freakin' amp I've ever used... and I used to run a 1600w solid state rig. I literally never turn it up past Volume 1, and I usually play it with volume at .75. Seeing as this amp has always been more than loud enough for me, I figured I would use two transformers of about the same size/weight. I'm trying to decide between transformers of an Ampeg V4B, a Hiwatt DR103, or a Sunn 200s.

My current AIMS tube amp is very clean. I use it to play jazz/fusion, so having an "always dirty" rock sound is out of the question. I'm not saying that I'd never want it dirty, but I need to have enough headroom to run it clean when I'm not playing rock. You can read more about the tone of my current head in my thread here. You can hear my tone here or at our bandcamp.

One of the main considerations for me was the weight of the transformers, since I'll essentially be putting 2 amps into one box. The weights of each transformer are as follows:

Sunn 200s - 7 lbs
Hiwatt 100w - 6.5 lbs
Ampeg V4B - 10 lbs

I've heard that Sunn and Hiwatt are generally much cleaner, but since I'll be running stereo (or will usually be bridging the two output signals), I doubt either transformer will be pushing the tubes enough to distort. That being said, with the Hiwatt and Sunn being regarded as more transparent, I do love that Ampeg "spank." Unfortunately, I've never been able to try out any of these amps, so my question is this:

What are the objective tone differences/behaviors of the Ampeg V4B, Sunn 200s, and Hiwatt DR103?

I'm not looking for answers like, "I like my Ampeg cuz the sound rox!" If possible, I'd prefer something like, "I like brand X because it sounds more ____," or, "Such-and-such amp is built to distort at ____ levels," or, "_____ amp is known to have an eq form with a heavy boost in the mids."

Also, I've searched for answers, but I've run into some discrepancies, varied experiences, and not many direct comparisons. If possible, I'd like to have these accurately described in reference to each other.


Thank ya kindly!

[JGR]

This is a fairly ambitious project - have you ever built anything like this before? If not, you may want to reconsider. Plenty of good stereo power amps out there for guitar that would fit the bill.

[JimmyM]

Originally Posted by SpankyPants

I'm trying to design a stereo tube amp, so I'll need two output transformers. My current AIMS amp only uses 2 KT-88's, and it's the loudest freakin' amp I've ever used... and I used to run a 1600w solid state rig. I literally never turn it up past Volume 1, and I usually play it with volume at .75. Seeing as this amp has always been more than loud enough for me, I figured I would use two transformers of about the same size/weight. I'm trying to decide between transformers of an Ampeg V4B, a Hiwatt DR103, or a Sunn 200s.

My current AIMS tube amp is very clean. I use it to play jazz/fusion, so having an "always dirty" rock sound is out of the question. I'm not saying that I'd never want it dirty, but I need to have enough headroom to run it clean when I'm not playing rock. You can read more about the tone of my current head in my thread here. You can hear my tone here or at our bandcamp.

One of the main considerations for me was the weight of the transformers, since I'll essentially be putting 2 amps into one box. The weights of each transformer are as follows:

Sunn 200s - 7 lbs
Hiwatt 100w - 6.5 lbs
Ampeg V4B - 10 lbs

I've heard that Sunn and Hiwatt are generally much cleaner, but since I'll be running stereo (or will usually be bridging the two output signals), I doubt either transformer will be pushing the tubes enough to distort. That being said, with the Hiwatt and Sunn being regarded as more transparent, I do love that Ampeg "spank." Unfortunately, I've never been able to try out any of these amps, so my question is this:

What are the objective tone differences/behaviors of the Ampeg V4B, Sunn 200s, and Hiwatt DR103?

I'm not looking for answers like, "I like my Ampeg cuz the sound rox!" If possible, I'd prefer something like, "I like brand X because it sounds more ____," or, "Such-and-such amp is built to distort at ____ levels," or, "_____ amp is known to have an eq form with a heavy boost in the mids."

Also, I've searched for answers, but I've run into some discrepancies, varied experiences, and not many direct comparisons. If possible, I'd like to have these accurately described in reference to each other.


Thank ya kindly!

You sure ask a lot of questions for a zombie!

This is more of a research project than I think a TB thread is equipped to handle. Maybe someone can help you out with it, but tone and personal likes are so subjective that I really don't think it'll help you all that much to make up your mind.

[projectMalamute]

I don't think you are going to find a lot of people who have had any way to compare these things outside of the surrounding circuit. All those amps sound very different from each other and the OT is just one of many, many reasons for that.

The Sunn is an ultra linear transformer, so that's a fundamental difference. The Hiwatt's had I think Partridge transformers and will probably be the most expensive to source.

Which brings me to my next point: you are really going to try and track down these transformers? They aren't magic you know, and companies like Mercury Magnetics or Hammond or any number of others can make you a very good transformer for much less money.

[SpankyPants]

Originally Posted by JGR

This is a fairly ambitious project - have you ever built anything like this before? If not, you may want to reconsider. Plenty of good stereo power amps out there for guitar that would fit the bill.

It is an ambitious project, but I'm an ambitious guy. I didn't know how to play bass before I taught myself. I didn't know how to build a guitar before I taught myself how to. I didn't know how to build a pedal before I taught myself how. Now it's safe to say that I haven't mastered any of these, but I have enough know-how to find/create/modify something that suits me. I've already spoken with a few people (technicians, boutique amp manufacturers, etc.), and they've helped me with some ideas. They let me know what's possible and what isn't (which is where some of my ideas end up dying ).

Right now, I don't know how to build an amp. Am I going to try to teach myself? Not quite. I plan on attending luthierie and tube-amp schools next year. But I have an idea of a build I'd like to try, and it takes time to design these things. So even if I can't build this now, I'll be able to work on it by this time next year. But in the meantime, I'm trying to figure out what I want and what it will take to get me there.

Originally Posted by JimmyM

You sure ask a lot of questions for a zombie!

This is more of a research project than I think a TB thread is equipped to handle. Maybe someone can help you out with it, but tone and personal likes are so subjective that I really don't think it'll help you all that much to make up your mind.

Someone always makes a comment like this... But I didn't ask for preferences; I asked for differences. Things that are objective and measurable, like "_____ is louder than _____," or, "______ is built to emphasize the mids instead of ______," or, "______ is meant to stay clean while _______ is made to have an earlier break-up."

I'm asking for people who have experienced one or more of these amplifiers to give me an objective comparison, not a subjective preference. I've searched TB and the interwebz, but I've still come up with inconclusive results. If I can get at least one or two people to compare these, that would help give me an idea of the differences.

Originally Posted by projectMalamute

I don't think you are going to find a lot of people who have had any way to compare these things outside of the surrounding circuit. All those amps sound very different from each other and the OT is just one of many, many reasons for that.

The Sunn is an ultra linear transformer, so that's a fundamental difference. The Hiwatt's had I think Partridge transformers and will probably be the most expensive to source.

Which brings me to my next point: you are really going to try and track down these transformers? They aren't magic you know, and companies like Mercury Magnetics or Hammond or any number of others can make you a very good transformer for much less money.

Mercury Magnetics actually sell all three of those. That's where the weights come from - they're all MM's specs. But are you suggesting that they could make a custom one for cheaper? Their prices are as follows: Ampeg $265, Hiwatt $285, Sunn $300.

I understand that the OT's are just one part of a complex piece of machinery, but in my current miniscule understanding of tube amps, transformers are important on how a tube is driven (right?). When it comes to tubes and caps, I'll go on personal preference, but I'm looking for info on these transformers the only way that I know how (and the only way that I think people could compare them). So while a transformer is just part of an amp's ultimate sound, it's still a part.

Otherwise, it seems that you're pretty knowledgeable about transformers. What is an ultra linear transformer, and how is it different from the other two? Any information at all would be greatly appreciated.

[seamonkey]

You can get the best and lightest transformers from Plitron. They will even custom wind one for lower prices and faster turnaround that you'd expect

Vacuum Tube Audio Output « Plitron

[wcriley]

Have you visited this forum?
Hoffman Amplifiers - Index

Lots of knowlegeable and helpful people when I was hanging out there.

[nashvillebill]

If you have never ever built an amp... please STOP. Or at least PAUSE.

At least with the bass amp idea for now. Build a simple SE guitar amp like a Champ clone to figure out what you are doing. There's a LOT to tube amp building, especially on high-power setups, a lot more than shoving some components in a box and connecting a few wires. Bear in mind these voltages and currents are LETHAL.

Don't get me wrong--nothing wrong with ambition! But things like lead dress, proper power supply wiring, heater supplies, component location--they sound trivial but they are not. Look on the DIY amp building boards and see the frustrations folks have even with simple SE designs.

Start simple, learn, build small stuff and after a few successful projects then try the big rig. But to go straight for the big rig IMHO is a recipe for disaster.

(I know I'm a party pooper)

[projectMalamute]

Originally Posted by SpankyPants

Mercury Magnetics actually sell all three of those. That's where the weights come from - they're all MM's specs. But are you suggesting that they could make a custom one for cheaper? Their prices are as follows: Ampeg $265, Hiwatt $285, Sunn $300.

Mercury Magnetics make a replacement transformer for all of those. An actual V4B transformer was made (I think) by Electrical Windings Company, Hiwatt by Partridge, and I'm not sure about Sunn(I want to say it was the transformer used in some Dynaco hifi amps). How similar they are side by side with the real thing I have no idea.

Your post made it sound like you were trying to track down vintage parts. By all means go with Mercury or someone like that.

Originally Posted by SpankyPants

What is an ultra linear transformer, and how is it different from the other two? Any information at all would be greatly appreciated.

An ultralinear amplifier uses an extra tap on each side of the primary of the output transformer which is connected back to the screen grid. You can get lower distortion this way(apparently, my hands on knowledge of amps pretty much extends as far as hot rodding old Marshall-type designs and fixing stuff for friends).

This was common with hifi amps but is pretty rare with guitar amps. Sunns and the Bassman 70/135 are the only amps off the top of my head that work this way.

But again, I am by no means an expert. I got in to fiddling with guitar amps solely because I got sick of my guitar players showing up with Pod's. I don't even play a tube amp.

[JGR]

I have a fair amount of experience designing and building amps. I think you are barking up the wrong tree. Do some more reading so you can ask the right questions. Buy the London Power books and read them. Understand them. That will keep you busy for a couple of years. The Internet has a lot of great info and smart, helpful folks. Even more idiots and BS. You need to develop a solid foundation which comes from studying scholarly sources so that you can separate truth and fiction.

[SpankyPants]

Originally Posted by seamonkey

You can get the best and lightest transformers from Plitron. They will even custom wind one for lower prices and faster turnaround that you'd expect

Vacuum Tube Audio Output « Plitron

Originally Posted by wcriley

Have you visited this forum?
Hoffman Amplifiers - Index


Lots of knowlegeable and helpful people when I was hanging out there.

Thanks, guys. I'll check into that.

Originally Posted by nashvillebill

If you have never ever built an amp... please STOP. Or at least PAUSE.

At least with the bass amp idea for now. Build a simple SE guitar amp like a Champ clone to figure out what you are doing. There's a LOT to tube amp building, especially on high-power setups, a lot more than shoving some components in a box and connecting a few wires. Bear in mind these voltages and currents are LETHAL.

Don't get me wrong--nothing wrong with ambition! But things like lead dress, proper power supply wiring, heater supplies, component location--they sound trivial but they are not. Look on the DIY amp building boards and see the frustrations folks have even with simple SE designs.

Start simple, learn, build small stuff and after a few successful projects then try the big rig. But to go straight for the big rig IMHO is a recipe for disaster.

(I know I'm a party pooper)

Not a party pooper at all. I didn't say I'm building this amp. I'm still trying to design it. I know I'm not capable of a build at this point. I know that I don't have enough know-how or skill to really put this together. But like I said, I will be taking classes in amp building and repairs sometime next year. We'll be building simpler amps, likely out of kits. And every step of the way, I've been checking with amp technicians and manufacturers to make sure my theories (or hopes, I guess) are possible.

Right now I'm just trying to figure out which transformers I'll want to use for a hypothetical amp that I'd like to eventually try to build. Even if I build a simpler, mono amp instead, all I had asked of this thread is one question. Everyone has offered answers for a lot of other questions I haven't asked. I just wanted to know the differences between the transformers I mentioned. You can leave the rest up to me.

I'm trying to be ambitious, yes. I'm trying a build that doesn't exist to my knowledge (yet). That doesn't mean that my carriage is in front of my horse or that I'm deluded enough to think that I can do this myself. I don't plan on "going straight for the big rig." I just have an idea of what I want, and I'm trying to piece something together that I can eventually try to build. But aside from that, I had only asked one, simple question.

Originally Posted by projectMalamute

Mercury Magnetics make a replacement transformer for all of those. An actual V4B transformer was made (I think) by Electrical Windings Company, Hiwatt by Partridge, and I'm not sure about Sunn(I want to say it was the transformer used in some Dynaco hifi amps). How similar they are side by side with the real thing I have no idea.

Your post made it sound like you were trying to track down vintage parts. By all means go with Mercury or someone like that.



An ultralinear amplifier uses an extra tap on each side of the primary of the output transformer which is connected back to the screen grid. You can get lower distortion this way(apparently, my hands on knowledge of amps pretty much extends as far as hot rodding old Marshall-type designs and fixing stuff for friends).

This was common with hifi amps but is pretty rare with guitar amps. Sunns and the Bassman 70/135 are the only amps off the top of my head that work this way.

But again, I am by no means an expert. I got in to fiddling with guitar amps solely because I got sick of my guitar players showing up with Pod's. I don't even play a tube amp.

MM sells transformers made by other brands as well. The Hiwatt trasnformer that MM sells is actually made by Partridge, for example. (Maybe I'm just confused, and they're made according to a Partridge schematic or something like that. You can see the Partridge logo and other brand names on the left side of the listed products on their site.) I'm sorry for the confusion, but I'm not looking for a vintage tone. These are just the three transformers that most closely approximate the wattage-level I'm seeking. I'm just trying to figure out how they're different. You're the only person who has read the bold-typed question, it seems, to actually endeavor an answer.

Back on topic - So theoretically, the Sunn amp (being ultralinear) would have a cleaner sound? Is that in general or as the tubes get pushed at higher volumes?

Originally Posted by JGR

I have a fair amount of experience designing and building amps. I think you are barking up the wrong tree. Do some more reading so you can ask the right questions. Buy the London Power books and read them. Understand them. That will keep you busy for a couple of years. The Internet has a lot of great info and smart, helpful folks. Even more idiots and BS. You need to develop a solid foundation which comes from studying scholarly sources so that you can separate truth and fiction.

I appreciate your intentions, but I feel like this response is fairly condescending. Like I said, I'm not building this amp. I never said I was building an amp. In fact, I said I didn't know how to build an amp. I didn't ask for advice on building an amp. I didn't ask if I should build an amp or if I should reconsider and settle for something else. I didn't ask for someone to separate truth from fiction or for reading material. Instead of telling me that I need to ask the right question, why don't you read the question I've asked? Maybe you can answer that out of your fair amount of experience.

I said I'm trying to design an amp. I said that I plan on going to a vocational school for amp building in my original post. In fact, the word "build" isn't in my first post at all, and the only times I used it in my second post were either in reference to something other than tube amps or an admission that I didn't know how to build it... that I had something in mind to try in the future - after I learned more about it. I even said that I knew I wouldn't be able to teach myself how to build this. I said I had a design in mind. Everything I've had in mind so far, I've checked out with people who understand this much better than I do. Kevin O'Connor is actually the next person on my email list... after I've decided on the transformer. Which brings me back to my original question...

So please instead of telling me what tree I'm barking up or how many years it will take me to understand the inner-workings of tube amps, please just pay attention and answer the question I'm asking. I'm not a kid riding some whimsical delusion of grandeur. I'm not naive enough to think I'm going to be able to do this off the bat. I'm an adult. I'm educated and have reasonable expectations and boundaries. I understand what it will take to learn about this, and I respect the amount of knowledge and skill required to tackle something like this.

These kinds of answers are why I isolated the question and put it in bold letters. I knew that it would be a struggle for people to actually recognize where the question was... Even though it's followed by the only question mark in the entire post... Simple question, simple answer, right? Not looking to be told I should abandon an idea because I'm unable to grasp the immense underpinning of the internet and the implications therein. Just looking for a simple answer.

I'll go ahead and repeat it so you won't even have to scroll up:

What are the objective tonal/behavioral differences of the transformers in the Ampeg V4B, Sunn 200s, and Hiwatt DR103?

[N.F.A.]

Here is one thought. Hiwatts used Partridge transformer, which were and still are coveted. If you want to know more about that one at least, perhaps an email to Mr. Janssen at Reeves amps. They are Hiwatt specialists. Another good resource might be Paul Tribe from Two Tribes music in the UK. John Chambers of Champ Electronics is truly an amp master. He is also based in the UK, but was very friendly to me in our dealings. Try him too. Those three guys know tons about what you're asking about.
Links...
http://www.chambonino.com/
http://www.twotribesmusic.co.uk/
http://www.reevesamps.com/

[JimmyM]

Slight correction...Dave Reeves was the head of Hiwatt, not Reeves, and is long dead.

[N.F.A.]

Thanks and fixed, I think that is his name.

[MAMMOTHvolume]

personally i'd get some wound to the partridge spec. Generally bigger core = better frequency response and lower distortion.

Also you wont be able to bridge two valve amps, transformers don't follow normal rules for impedance etc. when places in series / parallel

[BogeyBass]

Originally Posted by SpankyPants

One of the main considerations for me was the weight of the transformers, since I'll essentially be putting 2 amps into one box. The weights of each transformer are as follows:

Sunn 200s - 7 lbs
Hiwatt 100w - 6.5 lbs
Ampeg V4B - 10 lbs

When we start talking a straight forward approach to getting good power out of a tube amp for bass.

Not many tubes to give a krap about except the 6L6GC and the 6550A
aside from the KT88 which is just the British name for the 6550

If you read those data sheets RCA and General Electric figured out how to use those tubes effectively....many many many years ago.
Those data sheets all give good examples of push pull class AB1 amplifiers. and will tell you exactly how much plate voltage and load resistance you will need.

Then you can try all day long to reinvent the wheel....or you can look at amps made by some well known company's, and save yourself alot of pain.

So a quad of 6L6 for 100 to 130 watts
or a Quad of 6550 for 150 to 200 watts

No need to reinvent the wheel...trust me..you wont

For 6L6 your looking at a Fender Bassman 100 and the later Ultra Linear version the Bassman 135 or your looking at the Ampeg V4B. Those are the kings of 6L6 tone

For 6550 your looking at The Sunn 200S which is a pair of tubes.
or your looking at the Sunn 2000S which is a Quad. Then your looking at the Sunn Model T. Which is pretty much the 2000s with a Bassman preamp. Those are the Kings of the 6550, and all of those are Ultra Linear amps.

thats it... build a copy of any of those amps and your on your way.

If you want to go stereo i would go with 2 separate 100 watt amps, no need to kill yourself with Weight in a single unit. To much iron...to heavy.

Their is plenty of iron to be found, you could make a 100watt amp using plenty of cheapo Chinese transformers that floats around. Weber has all that china junk plus a million other fly by night internet company's.

if you want easily accessible decent iron, Hammond has plenty of nice ultra linear transformers so you could make your own version of the Bassman 135 or a Sunn 200s or a 2000s.
Heck even PartsExpress has transformers and Tubes
better deals can be found..if you look

[MAMMOTHvolume]

Originally Posted by BogeyBass

When we start talking a straight forward approach to getting good power out of a tube amp for bass.

Not many tubes to give a krap about except the 6L6GC and the 6550A
aside from the KT88 which is just the British name for the 6550

If you read those data sheets RCA and General Electric figured out how to use those tubes effectively....many many many years ago.
Those data sheets all give good examples of push pull class AB1 amplifiers. and will tell you exactly how much plate voltage and load resistance you will need.

Then you can try all day long to reinvent the wheel....or you can look at amps made by some well known company's, and save yourself alot of pain.

So a quad of 6L6 for 100 to 130 watts
or a Quad of 6550 for 150 to 200 watts

No need to reinvent the wheel...trust me..you wont

For 6L6 your looking at a Fender Bassman 100 and the later Ultra Linear version the Bassman 135 or your looking at the Ampeg V4B. Those are the kings of 6L6 tone

For 6550 your looking at The Sunn 200S which is a pair of tubes.
or your looking at the Sunn 2000S which is a Quad. Then your looking at the Sunn Model T. Which is pretty much the 2000s with a Bassman preamp. Those are the Kings of the 6550, and all of those are Ultra Linear amps.

thats it... build a copy of any of those amps and your on your way.

If you want to go stereo i would go with 2 separate 100 watt amps, no need to kill yourself with Weight in a single unit. To much iron...to heavy.

Their is plenty of iron to be found, you could make a 100watt amp using plenty of cheapo Chinese transformers that floats around. Weber has all that china junk plus a million other fly by night internet company's.

if you want easily accessible decent iron, Hammond has plenty of nice ultra linear transformers so you could make your own version of the Bassman 135 or a Sunn 200s or a 2000s.
Heck even PartsExpress has transformers and Tubes
better deals can be found..if you look

6550's and kt88's are different valves, they do a similar power but they aren't the same valve in the same sense a el34 isn't a 6l6.

Saying all power amps are the same is a bit of a sweeping statement, the transformer and power amp valve set up might not wildly change but theres alot of different ways to drive the power valves that sound different.

[nashvillebill]

BogeyBass is offering good advice. If you want to design your own amp totally from scratch, you're going to need a few decades worth of math, electrical theory, and experience...after which you will most likely wind up with something exactly like the designs that already exist.

Or you look at what already has been proven to work and duplicate one of those designs, which is what BogeyBass is suggesting. After all, tube amps have been around for 100 years and they have been exhaustively studied, designed, and perfected by some of the best minds (an largest labs) in the business.

I notice one or two components are missing from the discussion so far. The focus so far has been on output transformers (OT). But you've got to have a power transformer too, which will be just as heavy if not more than the OT (gotta have current for filament heaters).

What plate (and screen) voltages will you run? (I've seen amp forums come to verbal blows over the plate ratings for KT88 versus 6550--"it's the same tube" "no it's not"!!) Are you going to have a very stiff power supply or do you want some sag? How about the bias circuit, how will that be derived? This is not something that can be just guessed at. Plate voltages may run 600 volts or more. Power supply can make or break an amp.

And what about the preamp design?

The assumption that was being made was that the three amps in question had a sound due to their OT. I respectfully submit that the OT actually only contributes a tiny fraction to each amp's "sound". (advertisements for Mercury Magnetics, and Internet guitar amp lore, to the contrary). The power supply design itself makes a difference. The power amp design itself matters even more IMHO. The voicing of the preamp, where the tone stack lies in the gain stages, the circuit topology used (for the tone stack as well as the preamp itself), is perhaps an even bigger part of the equation. Read "Designing Tube Preamps for Guitar and Bass" by Merlin Blencowe. If you don't know what a load line is, this is where to start.

When I say "design" I mean circuit design, but an additional huge factor in an amp's success is the implementation of the design. How the amp is wired. Where components are placed. This isn't intuitively obvious, there's a lot to it that I sure don't know.

Again, we are not trying to be killjoys, or condescending, but rather trying to interject a reality check here. Building your own stuff can be a lot of fun and highly educational, so it's to be encouraged. However, building a high-powered amp isn't something to be taken lightly. Debating which OT is getting the cart before the horse, so to speak.

[SpankyPants]

Originally Posted by N.F.A.

Here is one thought. Hiwatts used Partridge transformer, which were and still are coveted. If you want to know more about that one at least, perhaps an email to Mr. Janssen at Reeves amps. They are Hiwatt specialists. Another good resource might be Paul Tribe from Two Tribes music in the UK. John Chambers of Champ Electronics is truly an amp master. He is also based in the UK, but was very friendly to me in our dealings. Try him too. Those three guys know tons about what you're asking about.
Links...
Champ Electronics - Vintage Amp Repairs
TwoTribesMusic
Welcome to Reeves Amplification

Thanks, I'll send 'em an email.

Originally Posted by MAMMOTHvolume

personally i'd get some wound to the partridge spec. Generally bigger core = better frequency response and lower distortion.

Also you wont be able to bridge two valve amps, transformers don't follow normal rules for impedance etc. when places in series / parallel

Thanks, this is the kind of answer I'm looking for. And in talking with an amp builder, he explained how to wire mono output signals in parallel and how it would change the impedance. Plus, there are transformers out there that are capable of switching impedances, which is another thing I need to consider.

Originally Posted by BogeyBass

When we start talking a straight forward approach to getting good power out of a tube amp for bass.

Not many tubes to give a krap about except the 6L6GC and the 6550A
aside from the KT88 which is just the British name for the 6550

If you read those data sheets RCA and General Electric figured out how to use those tubes effectively....many many many years ago.
Those data sheets all give good examples of push pull class AB1 amplifiers. and will tell you exactly how much plate voltage and load resistance you will need.

Then you can try all day long to reinvent the wheel....or you can look at amps made by some well known company's, and save yourself alot of pain.

So a quad of 6L6 for 100 to 130 watts
or a Quad of 6550 for 150 to 200 watts

No need to reinvent the wheel...trust me..you wont

For 6L6 your looking at a Fender Bassman 100 and the later Ultra Linear version the Bassman 135 or your looking at the Ampeg V4B. Those are the kings of 6L6 tone

For 6550 your looking at The Sunn 200S which is a pair of tubes.
or your looking at the Sunn 2000S which is a Quad. Then your looking at the Sunn Model T. Which is pretty much the 2000s with a Bassman preamp. Those are the Kings of the 6550, and all of those are Ultra Linear amps.

thats it... build a copy of any of those amps and your on your way.

If you want to go stereo i would go with 2 separate 100 watt amps, no need to kill yourself with Weight in a single unit. To much iron...to heavy.

Their is plenty of iron to be found, you could make a 100watt amp using plenty of cheapo Chinese transformers that floats around. Weber has all that china junk plus a million other fly by night internet company's.

if you want easily accessible decent iron, Hammond has plenty of nice ultra linear transformers so you could make your own version of the Bassman 135 or a Sunn 200s or a 2000s.
Heck even PartsExpress has transformers and Tubes
better deals can be found..if you look

I'm not sure I understand your first sentence.

I plan on using KT88's. And I'm not trying to reinvent the wheel, just rearrange familiar and well-known designs into one unit. That's why I'm asking about already manufactured and readily available amps and parts. I plan on using two of the same power section in parallel, essentially 2 copies. I was already leaning toward the Sunn, since it will weigh 6 lbs less than the Ampeg V4B. And those would be easier to work with, since they already run on KT88's. However, I'm still not quite sure on which would better suit this project otherwise, as the Partridge transformers do seem to be getting some support.

I have a different idea in mind for the preamp(s), though. Like I've said, I'm not designing these ideas on my own. I'm receiving help from people who understand this better than me. As I learn more about these amps, I'm sure my plans will be tweaked a bit, and that's fine. I'm just trying to get what parameters I understand at least set up in theory.

And if a stereo tube amp is too heavy, why do they already exist? It will be heavy, yes, but tube amps are heavy. What is too heavy?

Thanks for the links to the other transformers. I'll check those out.

Originally Posted by nashvillebill

BogeyBass is offering good advice. If you want to design your own amp totally from scratch, you're going to need a few decades worth of math, electrical theory, and experience...after which you will most likely wind up with something exactly like the designs that already exist.

Or you look at what already has been proven to work and duplicate one of those designs, which is what BogeyBass is suggesting. After all, tube amps have been around for 100 years and they have been exhaustively studied, designed, and perfected by some of the best minds (an largest labs) in the business.

I notice one or two components are missing from the discussion so far. The focus so far has been on output transformers (OT). But you've got to have a power transformer too, which will be just as heavy if not more than the OT (gotta have current for filament heaters).

What plate (and screen) voltages will you run? (I've seen amp forums come to verbal blows over the plate ratings for KT88 versus 6550--"it's the same tube" "no it's not"!!) Are you going to have a very stiff power supply or do you want some sag? How about the bias circuit, how will that be derived? This is not something that can be just guessed at. Plate voltages may run 600 volts or more. Power supply can make or break an amp.

And what about the preamp design?

The assumption that was being made was that the three amps in question had a sound due to their OT. I respectfully submit that the OT actually only contributes a tiny fraction to each amp's "sound". (advertisements for Mercury Magnetics, and Internet guitar amp lore, to the contrary). The power supply design itself makes a difference. The power amp design itself matters even more IMHO. The voicing of the preamp, where the tone stack lies in the gain stages, the circuit topology used (for the tone stack as well as the preamp itself), is perhaps an even bigger part of the equation. Read "Designing Tube Preamps for Guitar and Bass" by Merlin Blencowe. If you don't know what a load line is, this is where to start.

When I say "design" I mean circuit design, but an additional huge factor in an amp's success is the implementation of the design. How the amp is wired. Where components are placed. This isn't intuitively obvious, there's a lot to it that I sure don't know.

Again, we are not trying to be killjoys, or condescending, but rather trying to interject a reality check here. Building your own stuff can be a lot of fun and highly educational, so it's to be encouraged. However, building a high-powered amp isn't something to be taken lightly. Debating which OT is getting the cart before the horse, so to speak.

Well, it's possible to be constructive without being condescending. I feel like most posts (regardless of whether or not they even come remotely close to answering my question) have achieved that.

Like I've said several times before, all I asked about was the transformers. I acknowledge that the sound of an amp comes from many factors, OT's just being one of them. However, I'm only asking about the OT's. I have an idea in mind for the preamp, like I've already said. When I choose which OT's I want, then I can match them to a power transformer. Or maybe I'll do the reverse. Or maybe I'll do it all at once. But I'm not asking about power transformers yet. I'm asking about output transformers. Because that's the part of the design that I'm looking at.

I'm not taking this lightly, nor am I separated from the reality of this task. I just asked a question. A least a couple people have tried to answer it. I'm not finalizing anything, I was just looking for information. I'm not going to try to build anything without being completely sure of its inner workings. All that I wanted was a bit more information about these output transformers. That's it. That's all I was asking. That's all I'm still asking. It's pretty simple. Maybe I'll favor one type now and change my mind. Maybe I'll favor one type now and stick to it. Maybe I won't favor any of them until I do more research. But these are the kinds of things that many of you seem to be assuming. I've said over and over again, I'm just looking for more information on the output transformers. Not theory. Not build plans. Nothing but information on the output transformers. No one knows what I have in mind other than me, but that hasn't stopped people from assuming. I've tried to phrase my questions in ways that would hopefully minimize the amount of assuming someone could do, so someone could just answer my question. It seems that nothing will stop people from assuming what they want, and that's fine. Except for the fact that it has impeded my search for one thing: information on the aforementioned output transformers. Because that's all I'm asking about. That's all I'm looking for. The reality is that's all I've asked about.

No one knows anything else about what I want from this amp. No one knows anything else about how I plan on getting there. No one knows this amp from a hole in the ground. The only thing I've even mentioned about the amp is that I'd like to try a stereo setup, and I need something that can remain relatively clean at higher volumes. Neither of those are set in stone. Nothing is set in stone. I never said that this is what I've decided and no one can tell me otherwise. I said I'm trying to design something. I'm taking one step at a time. I've already said that I know it will be years before I could even bother attempting a build like this, which everyone seems to be repeating back to me. I've repeated over and over again that this is a hypothetical design right now. Novel designs rarely ever remain the same as they progress, and that holds true for almost any field. I am aware of this. I've encountered this in other projects. But that doesn't change how irrelevant all of that is.

Because all I've asked is for more information about three output transformers, namely their differences.

Again, I appreciate the concern that I'm missing the forest for the trees. I'm not. I just wanted more info on a specific part. Maybe this will help guide my design, maybe it won't. Like I said, leave that up to me. This is something I'm working on. No one even really knows how much I've planned out or the extent of my understanding of tube amps. That hasn't stopped people from assuming... All I want is more information on this one part. That's all. That's it. That's what I'm asking. The rest isn't important. Because I've asked a simple question - something that should be easy to answer objectively if you have any understanding or experience of the models I mentioned.

It's not that I don't appreciate your input, but the extent of your answer that was actually relevant to the question I ask is essentially the sentence in bold. You spent a while trying to tell me what I've assumed, that I've jumped the gun. I'm trying to say that's exactly what is happening when someone is assuming the implications of my question.

Again, output transformers. What are the differences of the three I mentioned?

[nashvillebill]

Maybe somebody on here could give you some detailed specs on those particular transformers--but I doubt it. I suspect only Mercury and maybe a couple other custom transformer folks would have the basic parameters of input impedances and number of turns for those specific OT's, much less the details of the interleaving or exact type of laminations.

Here's why we're trying to be polite and slow you down a bit:

You don't even know ultralinear mode is. That's a very basic transformer concept, as is the concept of output impedance switching--engaging different taps on the secondary. That's not bridging mono outputs, totally different concept. It's obvious from your posts you don't know these basic concepts. Getting fixated on the OT's at this point seems a little...odd.

May I suggest a couple of books? These are found for free downloading on the 'net, most of them are here Technical books online :

"An Approach to Audio Frequency Amplfier Design" by GEC Valve, around 1957.

"Electric Guitar Amplifier Handbook", Jack Darr

"Acrosound Transformer Catalog" 1955?

"Amplifiers, the Technique of Sound Reproduction, Theory and Practice ", York