Anyone built a high-headroom low gain amp? Ideas?

[markmalin]

Hey guys!

I've always loved the tone of a Polytone Mini Brute for jazz. Warm, round, clean and tons of headroom with no breakup. I have this hairbrained idea to do something like a tube version of a Mini Brute. Just curious if anyone's done anything like this with any success. I figure 50'ish tube watts is fine, reverb necessary, but zero breakup even at high volumes.

Thoughts?

Humbly,
Mark.

[Smokebreak]

Check out the Standel stuff. I did one for Western swing recently, and it would not break up. I also tried Weber's version(can't remember what it was called right off) and though apparently it was more a "nod" to the Standels, it sounded really good too. Maybe more country clean than warm jazz, but interesting designs nonetheless that stay clean clean clean.

[potatofarmer]

Well, kind of. When I built a rocket-y amp, I used the extra triode for a single gain stage "normal channel". One gain stage, to volume control, to phase inverter. It still breaks up, of course, but quite later on its volume knob than the rocket channel.

If you're looking for zero breakup from the preamp, silverface Fenders are worth a look.

Ooh, or possibly look at some early Sunn schematics. A pair of tube-rectified ultralinear KT88s won't get you much more than 50W and will fight tooth and nail to not break up.

Pretty much any preamp topology will work, just keep it to under 3 gain stages (including the PI) or fewer. If you use an LTP for the PI, you can return the reverb to the second grid, which will lower the gain for the clean side as well as keep the reverb recovery gain stage out of the dry signal path.

Add a pair (or more) of extremely sensitive speakers like EVM12s and you're golden.

[markmalin]

Sounds like some interesting ideas. I'm not familiar with Standel...I'll have to look that up. So keeping the number of gain stages lower in the pre-amp sounds like a good start. Never used KT88's....interesting.....

[dartanion]

It's called a Hiwatt 😎

[markmalin]

It's called a Hiwatt 😎

Oh
I restored a 70's Hiwatt combo for a guy and was surprised how "jazzy" it sounded come to think of it

[rp]

I can just see the jazz guys faces when you show up with a Hiwatt.

Old Showman head comes to mind too as something less scary.

[markmalin]

I can just see the jazz guys faces when you show up with a Hiwatt.

Old Showman head comes to mind too as something less scary.

lol I think what I'd like to do is build something that "looks" like a Polytone - so the jazz guys will think they're playing something they should be playing. I have a line on a local Polytone Mini Brute for 200 bucks...I may pick that up and at least have something to compare with...then go from there.

[Gaz]

"Zero breakup even at high volumes." All this means is that the preamp is low enough gain to not be able to drive the power tubes or PI to clipping. There is nothing more to it than that. You can of increase the clean feel of the thing by using a ton of negative feedback, which of course has its pros and cons.

Even Hiwatts and Silverface Fender have good breakup when pushed to their limits. And this purely my opinion, but the whole charm and allure of tubes is their breakup characteristics. There's a reason the Polybrute exists, and a reason it's solid state (well two, it makes it light as well). And hey, I don't know what fuddy-duudy's you're hangin' with but jazz cats like some grit too!

[markmalin]

"Zero breakup even at high volumes." All this means is that the preamp is low enough gain to not be able to drive the power tubes or PI to clipping. There is nothing more to it than that. You can of increase the clean feel of the thing by using a ton of negative feedback, which of course has its pros and cons.

Even Hiwatts and Silverface Fender have good breakup when pushed to their limits. And this purely my opinion, but the whole charm and allure of tubes is their breakup characteristics. There's a reason the Polybrute exists, and a reason it's solid state (well two, it makes it light as well). And hey, I don't know what fuddy-duudy's you're hangin' with but jazz cats like some grit too!

lol. I don't know if I should admit it...but I like to play jazz and nothing sounds quite like a Polytone. It's just that I like tubes...a lot...

I realize it's probably a "solution waiting for a problem" but I always thought building a nice, compact tube jazz amp would go over well. I could be way out in left field, but I'd like to try.

[rp]

Build a Gibson EH-150, good enough for Charlie Christian w/ an orchestra to boot. It's certainly low gain, as for headroom only you know how much you need. Peeps here have built, do a search.

Instead of freakin' the jazz cats will all go oooo....

[Smokebreak]

The thing is, "jazz", and thus "jazz amp" is such a broad/vague term these days. I play some jazz, too, but my flavor is the crusty 40's circuits, because they're raunchy. Junior Barnard and those WS guys are my heroes for that stuff. The Standel was too clean for my jazz stuff, but great for country stuff. But my country stuff my be your jazz stuff
The EH-150 actually doesn't have a ton of headroom, and if you build up the mic channel, it's gnarly! One of my groups is a guitar trio, and the amp lineup lately has been a EH150 , a SF Princeton, and a Polytone. Go figure. Sometimes I think the jazz cats are more picky about their tone than the metal guys.

[Gaz]

"Zero breakup even at high volumes." All this means is that the preamp is low enough gain to not be able to drive the power tubes or PI to clipping. There is nothing more to it than that. You can of increase the clean feel of the thing by using a ton of negative feedback, which of course has its pros and cons.

Even Hiwatts and Silverface Fender have good breakup when pushed to their limits. And this purely my opinion, but the whole charm and allure of tubes is their breakup characteristics. There's a reason the Polybrute exists, and a reason it's solid state (well two, it makes it light as well). And hey, I don't know what fuddy-duudy's you're hangin' with but jazz cats like some grit too!

lol. I don't know if I should admit it...but I like to play jazz and nothing sounds quite like a Polytone. It's just that I like tubes...a lot...

I realize it's probably a "solution waiting for a problem" but I always thought building a nice, compact tube jazz amp would go over well. I could be way out in left field, but I'd like to try.

Totally, I was just trying to emphasize making a good clean amp is easy. Unfortunately to make it truly clean at stage volumes, in theory would need to match the clean rms power of the poly tone... and then you have a big heavy tube amp. Size and weight considerations aside, I think this amp will be ALL about tweaking the tonestack (or choosing a tone stack - FMV or James?), and the amount of NFB, if any.

Polytone to Jazz is Marshall to Rock and roll, and so I no one can blame you!

[matt h]

derp

[M Fowler]

I built an Ampeg B15N circuit recently with 6SL7 preamp tubes and 6550 output tubes with LTP-PI. That amp is loud and clean.