SVT100 - any info?

[barebones]

Alrighty then! Amp sounded very good at the gig. Big and round sounding. I have questions about how to get more mids out of it, perhaps by my tube choices, so I hope some of you guys can chime in on that subject.

Currently the tubes are 2 GE 6550s, 1 RCA 6550, one off-brand 6550, and 3 off-brand, made in India 12ax7s.

At first I was excited to see the U.S. made tubes in there, but they don't look like they've been treated all that well over the years. They've got loose, rattling metal collars (not sure if that's the right term) at the top, and they look like maybe they've been run pretty hot at some point. I could be wrong about that, but they've got some big, dark burned looking spots on the sides, so...

Anyway, more important than all that is the sound aspect I mentioned. I know a lot of people love a sort of "scooped" sound, and this tube arrangement certainly provides that, but I want more mids, more cut. Any suggestions regarding tube types that might be interchangeable with 6550s? Or perhaps another brand to look for?

Okay enough of that for now. For posterity's sake, here are some basic tech specs on this amp:

Sounds like it could be more than 100 watts, and the tube complement might suggest that as well, but with only the model number and no other power information on the chassis, I'll say it's one hundred watts until I have a tech run through it.

Made in? No manufacturer's information on the amp whatsoever. Chassis is stamped "JAPAN" inside, but I don't know if that means the whole amp was made in Japan or just the chassis. I'm sure you guys who know a lot about Ampeg's history could make an educated guess on this.

Dimensions are approximately 27" wide, 10" deep, and 11" high not including the added height from the feet on the bottom. Appears they used 1" plywood for the head cabinet, not 3/4".

Weight is about 53 lbs.

I have a bunch of pics of the head, but apparently my files are too large to post here. If anyone has any suggestions on how to get around this I'm all ears. Not much to look at, really. If you've seen any of the all-black Ampeg heads then you know what this looks like. Some of the internal pics I have, as well as pics of the transformers and such, may be of interests to the techs on this board. Just let me know if you want to see those and I can email them to you or something.

Matt

 

[Stubb]

At first I was excited to see the U.S. made tubes in there, but they don't look like they've been treated all that well over the years. They've got loose, rattling metal collars (not sure if that's the right term) at the top, and they look like maybe they've been run pretty hot at some point. I could be wrong about that, but they've got some big, dark burned looking spots on the sides, so...

Tubes usually have dark areas at the tip of them, and this usually extends to the starting of the cylinderical part of the tube. Your "burned looking spots" are on the sides though? That's bizarre.

Anyway, more important than all that is the sound aspect I mentioned. I know a lot of people love a sort of "scooped" sound, and this tube arrangement certainly provides that, but I want more mids, more cut. Any suggestions regarding tube types that might be interchangeable with 6550s? Or perhaps another brand to look for?

KT88s are interchangable with 6550s, but you'll always have to rebias your amp when you replaced power tubes. Lots of guys use GE 6550s in their Ampegs. I'd suggest getting a full set of either new GE 6550s or doing some research into KT88s.

Okay enough of that for now. For posterity's sake, here are some basic tech specs on this amp:

Sounds like it could be more than 100 watts, and the tube complement might suggest that as well, but with only the model number and no other power information on the chassis, I'll say it's one hundred watts until I have a tech run through it.

With that tube complement, I'd sure guess that it'd be 200 watts, or near it. You never know - maybe it was intended to run with 6L6 power tubes, thus putting out 100 watts, maybe a hair more. But I think some guys run their Ampeg V4B with 6550s, because I think the bias control allows for that difference, and the transformer can handle it.

 

[Moo]

Anyway, more important than all that is the sound aspect I mentioned. I know a lot of people love a sort of "scooped" sound, and this tube arrangement certainly provides that, but I want more mids, more cut. Any suggestions regarding tube types that might be interchangeable with 6550s? Or perhaps another brand to look for?

Huh, the one I played had tons of mids, what cabinet are you using? Have you played with the deep bass switch or whatever it's called?

And what did you end up paying for it?

 

[barebones]

Thanks for the info, Eric. I had read a little bit here on TB about the interchangeability of 6550s and KT88s. I seem to recall some somewhat conflicting information on whether the KT88s, in general, produce more bass, mids, both...? I think I may have also read that you could use 6L6s, but I don't recall what was said regarding the tone. Anyone else have any info on this?

And I'll definitely be getting this thing thoroughly checked and biased by Noel at Stubbyfex once I've gathered a little more info on tubes. He's in my area and has always done good work at a reasonable price for me. (Just an FYI for the other Denverites here.) I think Fat Willie,--a.k.a. Lord Valve--whom I'm sure you guys all know, has the better tube selection, though (another FYI) so I'll probably be needing to stop by his place as well. He's always been a great resource.

Oh, and as to whether this amp was designed originally to take 6L6s, I'm not sure. There is a tube diagram inside the cabinet showing 6550s, but I just can't find much history on these, as you know.

Matt

 

[barebones]

Huh, the one I played had tons of mids, what cabinet are you using? Have you played with the deep bass switch or whatever it's called?

And what did you end up paying for it?

Hey, Moo. I've tried it through two setups. One's a Big Ben 1x18. I know what you're saying: "Well, duh, there's your lowend!" But this cab has an EV replacement speaker that was there when I got the cab, and it typically has been anything but scooped sounding with other heads. I also ran the head through a couple of homemade 1x15 cabs I keep at the house here, which are typically very strong in the mids. Still pretty scoopy, even with a lot of bass rolled off and the deep switch disengaged. Maybe I just need to fiddle with it some more... I certainly can't say I'm well acquainted with it yet. If I can find a setting on it that's more or less "flat" then of course I can go from there.

I got the head for $300, which seemed like a fair deal. My ideal was to have something with two channels, but tube head prices have been taking a jump lately online, and I just couldn't afford most of what I was looking at--Bassman 100s... a V4Bs... old Traynors... Everything I was looking at was going for around $400 plus shipping. I do think I'll be satisfied with this head, though, once I get things dialed in where I want them.

Matt

 

[Moo]

Yeah, sounds like it's not the cab

$300!!! Sweet.

 

[barebones]

Yeah, sounds like it's not the cab

$300!!! Sweet.

In all seriousness I tell you I am dying to run this amp through is a nice 4x12 for bass. I dare say it would be virtually unstoppable!

Matt

 

[barebones]

Well, I it appears the tonal issues I mentioned before were as simple to remedy as changing out the old preamp tubes. I did a little experimenting today, and the old tubes were just plain mushy sounding compared with some NOS Tungsram ECC83s and a Tung-Sol 12AX7A I had in the parts drawer. I'll probably still be looking for some new power tubes, as I'm starting to suspect someone stuck their raunchiest old tubes in this baby before I got to it. But the preamp tubes alone have made quite a difference.

We'll see how it sounds now at tonight's gig. Of course I'll be on a different stage, so all aspects of a controlled scientific method are out the window here. Not that they were ever in place to start with, but you know...

Matt

 

[Psycho Bass Guy]

At first I was excited to see the U.S. made tubes in there, but they don't look like they've been treated all that well over the years. They've got loose, rattling metal collars (not sure if that's the right term) at the top, and they look like maybe they've been run pretty hot at some point. I could be wrong about that, but they've got some big, dark burned looking spots on the sides, so...

The metal structures are collars, but they're at the bottom, not top. The SVT 100 runs them upside-down. The "burned spots" are getter flash, and if theyr'e brown, the tubes are near death, either from age or being underbiased, and in either case need replacing.

Anyway, more important than all that is the sound aspect I mentioned. I know a lot of people love a sort of "scooped" sound, and this tube arrangement certainly provides that, but I want more mids, more cut. Any suggestions regarding tube types that might be interchangeable with 6550s? Or perhaps another brand to look for?

Get a matched set of the same kind of 6550's before you write the type off. GE 6550A's are famous for midrange, and while they may be expensive NOS, there is a Chinese copy distributed by Ruby that is made on the same machines as old GE tubes and it's cheap.

Sounds like it could be more than 100 watts, and the tube complement might suggest that as well, but with only the model number and no other power information on the chassis, I'll say it's one hundred watts until I have a tech run through it.

Four 6550's CAN be capable of 200 watts (or even 300 in the Fender 300PS). The limiting factor is the power supply, but I'm willing to bet that since the amp is called the SVT "100" it's a 100 watt amplifier.

Made in? No manufacturer's information on the amp whatsoever. Chassis is stamped "JAPAN" inside, but I don't know if that means the whole amp was made in Japan or just the chassis. I'm sure you guys who know a lot about Ampeg's history could make an educated guess on this.

MTI Ampeg amps were all made in Japan, but if yours was made after SLM bought Ampeg from MTI like Jerrold said, it could have been assembled in the US from old Japanese parts stock. At any rate, the MTI amps are fine and tales of them being poorly built are music store BS, IME.

 

[barebones]

The "burned spots" are getter flash, and if theyr'e brown, the tubes are near death, either from age or being underbiased, and in either case need replacing.

As always, thanks for the insight, PBG. I do suspect I have some near death tubes here. But then I knew that almost anything I would be buying in my price range would require retubing and biasing, so I'm prepared to deal with it.

Get a matched set of the same kind of 6550's before you write the type off. GE 6550A's are famous for midrange, and while they may be expensive NOS, there is a Chinese copy distributed by Ruby that is made on the same machines as old GE tubes and it's cheap.

Thanks for the tip. I seriously doubt I can afford NOS GEs right now, so I'll give the cheapies a try. I think I may even have seen the ones you're talking about on Ebay.

Four 6550's CAN be capable of 200 watts (or even 300 in the Fender 300PS). The limiting factor is the power supply, but I'm willing to bet that since the amp is called the SVT "100" it's a 100 watt amplifier.

That's what I've been assuming as well. I have learned from you and others here that tubes are only part of the equation when it comes to power. Oh, and yes, my assumption was also based on the "100" in the model number. I'm quite the genius in that way!

MTI Ampeg amps were all made in Japan, but if yours was made after SLM bought Ampeg from MTI like Jerrold said, it could have been assembled in the US from old Japanese parts stock. At any rate, the MTI amps are fine and tales of them being poorly built are music store BS, IME.

Yeah, my untrained eye tells me there's nothing overtly weak looking in terms of assembly or parts here. (Other than the tubes.) We'll see what my tech says when he opens it up. I don't really care if it was built in the U.S. or Japan as long as it works and sounds good. I definitely found it curious, though, that there just aren't any other indications of where the amp was built or by whom, other than the stamp I mentioned on the chassis.

I might also note that the transformers look--again, with my untrained eye--different from what I'm used to seeing in other tube amps I've checked out. I mean, I don't think I'd know a Hammond from a what-have-you out there, but my gut reaction when I saw them was, "Hmm... Wonder where THOSE were made... Perhaps Japan as well?" They look solid and all--just a little different.

Matt

 

[barebones]

Okay, I hope you all aren't getting completely sick of this thread, because I have kind of a weird question now. I was killing time today and popped into a shop that has a small selection of tubes. When I asked if they carried any 6550s and described the amp I would be putting them in I was told, "Nah. But you could just use some 6L6s..."

Now, I didn't jump at this idea, because this guy hardly seemed like an amp tech to me (in fact, my suspicious nature told me he simply was trying to get rid of some tubes), but it did get me wondering if this is feasible. For example, if you were in a pinch could you use 6L6s in and amp that's designed to take 6550s? They certainly seem to be more plentiful around here. And what might the effect of doing so be? Seems everything I've read on this is people trying to get away from their 6L6s to use 6550s instead, but the non-chalant way this guy brought this up just made me curious.

Anyway, haven't had a chance to get the amp into my amp guy yet, so I wondered what some of you here would think of this idea. Is this guy just crazy?

Matt

 

[Psycho Bass Guy]

I was killing time today and popped into a shop that has a small selection of tubes. When I asked if they carried any 6550s and described the amp I would be putting them in I was told, "Nah. But you could just use some 6L6s..."

Now, I didn't jump at this idea, because this guy hardly seemed like an amp tech to me (in fact, my suspicious nature told me he simply was trying to get rid of some tubes),

Bingo. Tech tip: most music store guys know even less about amps than they do women. Don't waste your time on people like that. There are far too many good tube dealers online who will give you correct advice and get you what you need, not what they're trying to get rid of. And while I'm at it, those tubes need to be replaced by a TECH. There are lots of things that can go wrong with a perfectly good set of tubes in a perfectly fine amp that can destroy them both. Power tubes are NOT user serviceable.

but it did get me wondering if this is feasible. For example, if you were in a pinch could you use 6L6s in and amp that's designed to take 6550s? They certainly seem to be more plentiful around here. And what might the effect of doing so be?

No. The 6550 is pretty much an uprated 6L6GC, which means that if a 6L6GC would work, it would be in there. Amps that run 6550's stock will have plate and screen voltages far above what a 6L6GC can handle. Unless you like watching a set of 6L6GC plates turn cherry red and burn up, probably doing some serious damage to the rest of the amp in the process, don't listen to that idiot.

Is this guy just crazy?

No, just full of it.

 

[barebones]

Tech tip: most music store guys know even less about amps than they do women.

Youch! Funny, though...

And while I'm at it, those tubes need to be replaced by a TECH.

While I do a lot of work on my own basses, I've always left amp work to the amp guys. If the fear of electrocution doesn't keep me away, the possibility of destroying my amp certainly does.

The 6550 is pretty much an uprated 6L6GC, which means that if a 6L6GC would work, it would be in there. Amps that run 6550's stock will have plate and screen voltages far above what a 6L6GC can handle.

Thanks for reiterating this point. I thought I had read something to that effect, but most of what I was running across in other threads dealt specifically with going from 6L6s to 6550s. Although logic certainly suggested that the opposite change would create certain problems as well--specifically the screen voltage issue--I know so little about the technical aspects of this stuff that I tend to second guess myself if some yahoo says, "Aw yeah, man, it's NO PROBLEM! Really..."

Thanks for the sound (pun intended) advice.

Matt

 

[Corwin81]

I restored a SVT-100 from a chassis I got on Ebay that was missing the PT, tubes, and a couple components. Got the schematic from Ampeg and looking at the voltages and circuit layout, it's identical to a Marshall JCM800 2203 except for where the low gain input is and tweaked for bass. I used a JCM800 power transformer and got the same voltages that the schematic specified. The V5 had component values closer to the Marshall, so theoretically, you could tweak it into a high gain metal guitar amp, or convert it to a SuperBass, but it is a PCB amp, so it would be a little harder, but there's a lot of room inside the chassis. came with 50uF can caps(Nichicon or something). Had to get new retainer clips and use JJ filters(100uF for the first one and 50uF for the remainder) and rewired the preamp tube filaments with twisted pair wires to cut down on some of the hum. I'd probably gig with it if I can find a suitable head case that could fit the damned thing

 

[ismordagore]

Just surfing around trying to find some info on the SVT100. I've owned one for about a year now and have done quite a bit of tracking with it. I think it sounds great. I picked it up for 350 bucks. I know this is an old thread but thought someone surfing through might want to hear one in the context a song. I use it on all of my songs. My usual signal chain: Fender Jazz Deluxe, Direct box, Bassman 2x15 cab (silverface front loaded version), Shure Beta 57, Shure SM58, Presonus firestudio tube into Logic 8. The direct signal and mics are mixed to taste. The amp is cranked to make it dirty and rattle the walls a bit. Oh yeah, I'm running Sovtek 6550's in the power section.

Give it a listen: http://www.facebook.com/snakeskineagle

 

[patch12173]

I have one of these and love it! I never had a problem with the volume at any gig. I run a 73 v4b cab with the SVT100 both 100watts and its killer tone. Ill always have the one that will never get sold.

 

[rodl2005]

I wonder if one could up the power supply & get close to 200w outta these?

 

[deanamite]

i know this thread is old but i wanted to add that the SVT 100 was basically the V5 guitar amp, just marketed for bass. the v5 had the svt pre amp and 4x 6550s as power tubes.
they pretty much just took the old MTI V5s and put them in a new case and called it svt 100

 

[JimmyM]

Yep, the rap on the V5 was it was a terrible guitar amp but sounded pretty good with a bass, so SLM went with it and made the SVT 100 out of them. Only 100 or thereabouts were made but it put SLM on the right track.

 

[Chris 'Wighat' Jordan]

Have there been any SVT-100 sightings lately?