Looking for suggestions for a low noise (hiss) practice amp

[JWK]

I'm trying to come up with the outline of my practice amp I want to build. The goal is to come up with an amp with the lowest amount of noise as possible (especially that hiss) while still staying alive with some harmonic distortion. The ideal would be for the output tubes to just start breaking up at full volume with typical Fender type single coils. No MV, no reverb.

Methinks the most difficult challenge will be for it to be harmonically interesting while still remaining quiet.

I think I will stick with pentode mode. I thought of using UL, but I think I will have more control over harmonic distortion using pentode mode. I can use a pot for the NFB resistor to take me anywhere from typical Fender to nothing (so I can still rock out a bit). Bring in the feedback to practice in your bedroom at night, take it out to get a little rowdy (and noisier).

I'm leaning toward a typical 40 watt 6L6 or EL34 amp, plate voltage 430 - 440. I prefer SS rectification. Fixed bias, of course.

Gain stages:
I'm not sure where to go with this. Right now I'm thinking of a parallel 12ax7 for the input stage to a 12au7 to a 12au7 concertina splitter. I think the concertina will have enough signal swing for my purpose, but I admit I don't know how to calculate that.
So for the 12au7 gain stage, I could cascade them into each other (probably too much gain that way) or parellel that tube also. I guess if I don't have enough gain I could add a direct coupled gain stage to the splitter like on a Williamson. Otherwise, the splitter will also be in parellel.

Tone Control:
I'm trying to keep this very simple. I would like one bass cut control and one treble cut control. No mid scoop required. I know - everyone likes the mid scoop, but I don't. Whenever I end up with a Fender amp I always end up diming the mid control and just barely bring the bass and treble into play. Anyway, I'm thinking of putting a bass cut right after the parallel 12au7 to take advantage of the lower Z, and put a cut control after the splitter a la AC30.

Now I know this will all work, but I'm afraid only two stages of gain that are both parallel tubes going into a concertina might end up sounding pretty sterile or hi fi.

If anyone has any suggestions for getting a nice interesting clean sound with depth, without sounding flat and transistor-like, I'm all ears.

[martin manning]

This may not be exactly where you're headed, but have you played a 5E3 Deluxe?

[diagrammatiks]

are you really going to be able to run a 50-100 watt practice amp?

it doesn't seem like you are looking for bedroom levels then?

[brewdude]

I don't know if this is helpful or not, but I had been working on a new amp using a parallel input 12AX7 into a 5693 Pentode with variable screen voltage into a parallel 12AU7 cathodyne PI into a cathode biased pair of 6V6's. I used an unconventional layout to make it fit in the recycled donor chassis.

It works good at many volumes, including bedroom level. It seems to be mostly clean with the ability to hit some good overdriven tones, but it isn't really suited for heavy distortion--at least as is. However, by manipulating the gain, volume, and VVR's you can find spots to emphasize overdrive at different stages to suit different volume levels. There are some triodes that are running parallel now, but could be used to add more gain stages if desired.

I have not had a lot of chances to put it to a true test with a live band. I expect that it could be tweaked some to suit your taste. As of yet, I do not have any demo recordings. I will have to enlist the help of one of my buddies with recording gear to help me make a demo.

[Jana]

6L6 or El34 in ultralinear mode, no master volume, pushing it to breakup volumes, practicing in the bedroom at night?

http://www.roland.com/products/en/Micro-CUBE/

[Big Jim]

This may not be exactly where you're headed, but have you played a 5E3 Deluxe?

You took the words right out of my mouth.

[Reeltarded]

6L6 or El34 in ultralinear mode, no master volume, pushing it to breakup volumes, practicing in the bedroom at night?

http://www.roland.com/products/en/Micro-CUBE/

Lol. Jana is a Roland rep.

[Jana]

Lol, I know--twice in one evening I posted the link.

[Reeltarded]

And I agreed both times. Life is good!

[Structo]

Yeah, I think that some kind of power scaling is needed here.

Check out the cathode bias VVR at

http://www.hallamplification.com/main.html?src=%2F#2,2

[JWK]

This may not be exactly where you're headed, but have you played a 5E3 Deluxe?

Yes I have. Love 'em. For this purpose, they do not have enough clean headroom. I've considered going the fixed bias 6V6 route, but it's just as easy to make a 40 watt 6L6 amp. Not much difference in clean *volume*, but a more full sound IMO.

[JWK]

are you really going to be able to run a 50-100 watt practice amp?

it doesn't seem like you are looking for bedroom levels then?

I can run anything I want, but I have no intention on building a 50 - 100 watt practice amp. I don't know where you got that.

Bedroom levels? Once in a while I need to practice in an upstairs room quietly, but most of the time I can play any volume I wish. I actually never play in my bedroom. That is only a phrase of speach I used (and apparently should not have) in reference to adjustable NFB. In context, I thought what I was trying to communicate was clear; that one of my high priorities for this amp is to eliminate as much "hiss" noise as possible.

[M Fowler]

What you described in your opening post is a Rocket with octal power section either 6L6, KT66 or EL34's.

The amp is pedal friendly, no hiss, super quiet operation, plenty of push when needed, can deliver Fender clean or let the power amp push a little. I add a DPDT bright switch for 100pf and 500pf. You could go with a PPIMV if you wish. To keep the amp even cleaner I change out the 220k plate of V1 to 100k or 120k.


Mark

[JWK]

6L6 or El34 in ultralinear mode, no master volume, pushing it to breakup volumes, practicing in the bedroom at night?

http://www.roland.com/products/en/Micro-CUBE/

Thanks for the Rolling Eyes. Thanks for the help. Oh, wait... that's right, you didn't.

I went back and rewrote a little bit of that paragraph so that (hopefully) it couldn't be twisted. It seems to me you took things out of context so that you could be snarky. If not, please tell me the purpose of your post in my thread.

[Doctordog]

I'm sure I have far less experience/knowledge than most here, but from my studies, to remove the noise depends much more on layout, spacing, and grounding methods than the actual circuit used.

JB