6550 / KT88 ... pick me a set

[Korladis]

I've since sold the amp I started this thread over (I started it 6 years ago ). At that moment in time / production: The Sovtek KT88 and Tung Sol 6550 were the same exact tube and the EH 6550 and KT88 were the same exact tube. So picking a KT88 over a 6550 is a little more difficult since the line was crossed repeatedly.

As for the KT90 and KT100 tubes... in the years since this thread was started I have spent most of my free time studying tube theory. I've got a design ready for prototyping (being delayed with my moving... another few weeks to go) that should have some universal appeal between guitarists and bassists. I've got 3 power sections planned ranging from 50 to 150 watts. All using a single pair of output tubes. The biggest is based on a pair of Tung Sol KT120.

Oooh

 

[okcrum]

I've since sold the amp I started this thread over (I started it 6 years ago ). At that moment in time / production: The Sovtek KT88 and Tung Sol 6550 were the same exact tube and the EH 6550 and KT88 were the same exact tube. So picking a KT88 over a 6550 is a little more difficult since the line was crossed repeatedly.

As for the KT90 and KT100 tubes... in the years since this thread was started I have spent most of my free time studying tube theory. I've got a design ready for prototyping (being delayed with my moving... another few weeks to go) that should have some universal appeal between guitarists and bassists. I've got 3 power sections planned ranging from 50 to 150 watts. All using a single pair of output tubes. The biggest is based on a pair of Tung Sol KT120.

Well, I'll be ****ed. Good on ya, James. I've gotta look at the dates on these posts more.

I've wondered about doing something with somewhat larger tubes. The problems there tend to be getting the iron parts, and linearizing tubes that aren't necessarily intended for audio use. Plus, the cooling air on ceramic tubes tends to be harder to manage acoustically.

 

[iamdenialNJ]

i picked the eh kt88h because i've put them in an ampeg svt2 pro and an aguilar db359 and loved them. no experience with the others.

I have some EH KT88eh's coming in the mail. I was using JJ KT88's before this retube. How do you like them? Do you have any experience using other KT88 tubes?

 

[MAMMOTHvolume]

shuguang gec kt88!

 

[tombowlus]

As for the KT90 and KT100 tubes... in the years since this thread was started I have spent most of my free time studying tube theory. I've got a design ready for prototyping (being delayed with my moving... another few weeks to go) that should have some universal appeal between guitarists and bassists. I've got 3 power sections planned ranging from 50 to 150 watts. All using a single pair of output tubes. The biggest is based on a pair of Tung Sol KT120.

I'd be very interested to see what you come up with, James!

Regarding the KT120's, I've been working with Bill Jansen from Reeves Amplification on bench/gig testing four KT120's in my Custom 225, and IME/IMHO, they are a definite winner. We're only measuring about a 12% increase in total output, but the KT120's don't scoop the mids as much (with that amp), and you can really hear/feel the difference live.

Tom.

 

[okcrum]

Weird, if the EH 6550s and KT88s were the same tube, then one of them is not the tube it was supposed to be.

KT88 is a true pentode, and (at least originally) the 6550, like the 6L6, 6V6, and others, was a tetrode with beam forming electrodes, hence the name beam power tube. They are very different approaches.

 

[okcrum]

I'd be very interested to see what you come up with, James!

Regarding the KT120's, I've been working with Bill Jansen from Reeves Amplification on bench/gig testing four KT120's in my Custom 225, and IME/IMHO, they are a definite winner. We're only measuring about a 12% increase in total output, but the KT120's don't scoop the mids as much (with that amp), and you can really hear/feel the difference live.

Tom.

Yeah, all the KTxx(x) I've tried seem to have this over the beam power tubes. Does Bill think it's from the tubes being true pentodes?

 

[tombowlus]

Yeah, all the KTxx(x) I've tried seem to have this over the beam power tubes. Does Bill think it's from the tubes being true pentodes?

We didn't talk about that aspect of the KT's.

Bill felt that his transformers would be up to the challenge of driving KT120's, and thought that this might get his players a bit more power/headroom. He asked us to do some bench-testing and gig-testing to assess the ability of the C225 to drive KT120's, and I am pleased to say that the C225 seems quite happy pushing them. Those are some big, beefy transformers!

Tom.

 

[Jhtjon]

Use the Tung-Sols. I just finished building a Modified SUN 200s clone and could not be happier. I tried the EH's and Chinese 6550s before settling on the Tung-Sols. While they all sounded great in the amp the Tung-Sols had better note definition, smoother low end response and more punch than the others. I did notice a slightly scooped mid in these, this may or not be a problem for you, it wasn't a problem for me. A close second were the Chinese but for a totally different sound. They had a very cool grindy overdriven tone. Like most tubes from EH I found them to be very neutral and consistent. This is not a knock on them in the least.

Just my $0.02, take it for what you want.

 

[BassmanPaul]

Weird, if the EH 6550s and KT88s were the same tube, then one of them is not the tube it was supposed to be.

KT88 is a true pentode, and (at least originally) the 6550, like the 6L6, 6V6, and others, was a tetrode with beam forming electrodes, hence the name beam power tube. They are very different approaches.

The KT88 was never a pentode, it's a Kinkless Tetrode as was the KT66 before it. The Kt88 is similar to the beam tetrode 6550 as was the KT66 similar to the beam tetrode 6L6GC. They can exchange for each other but they are not the same tube.

Modern tube manufacturers are blurring the lines between the types which is why, IMO, that folk are having so many troubles with their amps.

 

[okcrum]

The KT88 was never a pentode, it's a Kinkless Tetrode as was the KT66 before it. The Kt88 is similar to the beam tetrode 6550 as was the KT66 similar to the beam tetrode 6L6GC. They can exchange for each other but they are not the same tube.

Modern tube manufacturers are blurring the lines between the types which is why, IMO, that folk are having so many troubles with their amps.

Ah OK, I sit corrected. For some reason I always thought those were pentodes. So the (electron) beam management is the big difference, then?

 

[James Hart]

I'd be very interested to see what you come up with, James!

Once I prove my design... I'll have to send one your way Since the original Hiwatt and current Reeves stuff are just about the top of all things guitar/bass tube amp wise to my ears and brain, they are going to be a hard act for me to follow.

Just as a teaser: blended parallel preamps of EF806 and 6SL7 each with it's own unique tone stack mated to a 2 tube output section in a small footprint chassis. I'm planning 2xKT66, 2x6550 and 2xKT120 (sourcing and specing all Tung Sol reissue tubes) for approximately 50, 100 or 150 watts.

Regarding the KT120's, I've been working with Bill Jansen from Reeves Amplification on bench/gig testing four KT120's in my Custom 225, and IME/IMHO, they are a definite winner. We're only measuring about a 12% increase in total output, but the KT120's don't scoop the mids as much (with that amp), and you can really hear/feel the difference live.

I really like what I've read on them and I've yet to see any real world applications yet. It's good to know that you and Bill are giving them the nod. Beyond tone, my goal is to get as many watts for us bassists out of a small footprint since a lot of us have moved to small, modern and lightweight cabinets. The KT120 seems to be the ideal tube for my need.

Weird, if the EH 6550s and KT88s were the same tube, then one of them is not the tube it was supposed to be.

that's the point I was getting at... Paul already beat me to the explanation...

The KT88 was never a pentode, it's a Kinkless Tetrode as was the KT66 before it. The Kt88 is similar to the beam tetrode 6550 as was the KT66 similar to the beam tetrode 6L6GC. They can exchange for each other but they are not the same tube.

Modern tube manufacturers are blurring the lines between the types which is why, IMO, that folk are having so many troubles with their amps.

thanks again for your knowledge Paul... you are always a big help.

 

[okcrum]

Ah OK, I sit corrected. For some reason I always thought those were pentodes. So the (electron) beam management is the big difference, then?

Ah nm, Paul. Kinkless = beam tetrode. And the KT66 was basically the 1937 Marconi version of the 1936 RCA 6L6, developed to get around the patents Philips held on power pentodes.

 

[okcrum]

James, check this out:

http://www.chambonino.com/construct/const9.html

uses 813s.

 

[iamdenialNJ]

That transformer is HUGE! Bigger is better!!!!!!!!!

 

[James Hart]

James, check this out:

http://www.chambonino.com/construct/const9.html

uses 813s.

I've actually looked at that before Since the amp I started this thread about used 8xKT88 and ended up being WAY too much amp for me... I am looking to not quite go THAT high

 

[Korladis]

I would very much like to see a more finished version of that monster.

 

[tombowlus]

Just as a teaser: blended parallel preamps of EF806 and 6SL7 each with it's own unique tone stack mated to a 2 tube output section in a small footprint chassis. I'm planning 2xKT66, 2x6550 and 2xKT120 (sourcing and specing all Tung Sol reissue tubes) for approximately 50, 100 or 150 watts.

You, sir, have my full attention! Very nice!

 

[edbass]

Just as a teaser: blended parallel preamps of EF806 and 6SL7 each with it's own unique tone stack mated to a 2 tube output section in a small footprint chassis. I'm planning 2xKT66, 2x6550 and 2xKT120 (sourcing and specing all Tung Sol reissue tubes) for approximately 50, 100 or 150 watts.

Kudos James, those are some pretty ambitious specifications, especially for a first build! Who's building your transformers?

 

[okcrum]

I've actually looked at that before Since the amp I started this thread about used 8xKT88 and ended up being WAY too much amp for me... I am looking to not quite go THAT high

I understand. The first limit you hit with an amp like your older one or Chambers' is portability. It would be necessary to build it as a power amp only, on a wheeled enclosure, and use a separate preamp. That 1 kw amp probably weighs 175-225 lb. which is borderline portable. Going much past that, you or your roadies had better have a forklift handy.

Then there's the question of primary power. That monster will draw somewhere around 20 amps at 120 volts, so you couldn't just plug it into any old outlet at the club. Going to 240 volt mains means you'd halve the current draw, but could play only venues with that power available.

It seems the practical limit would be a 500 watt version of Chambers' amp.

<fantasy>
If one idly speculates about Disaster Area ("not only the loudest rock band in the Galaxy, but in fact the loudest noise of any kind at all" - Douglas Adams) class amplifiers, one could be done, with primary power supply, if you had oh, say, 6 flatbeds, a couple of semis, a box truck or two, a bus for the amp crew, a tanker (for the pair of gas turbine generators) and some serious cash. Use a pair of 8973s for the output stage and you could get a megawatt or so. Then you'd still need transport for the speakers.
</fantasy>

The craziest thing is, there are bands that already have transport logistics for something like that. U2 comes to mind. And a 1/2 megawatt audio amp was built as early as the mid-1930s as the modulator for the then-epic Invalid Link Removed.

Still, I wouldn't want to haul one to the gig.

Your amp design sounds real fine. There used to be some good transformer builders right in Trenton, too. Not sure if they're still there, though I'd doubt it.