6V6 - Best Distortion Ever ?

[alexc]

I've been playing around with a fender champ style circuit.

12AX7 to 6V6 single ended transformer to 8ohm speaker.
Mine uses a standard blackface treble/bass tonestack.

I generally use it on a hifi speaker. and with a Ross style compressor.

Always sounded great - typical heavy crunch at max volume,
mainly distorting on the low end with the mid and high not over the top.

All good - a 3W or so walk on the wild side , tamed by a hifi speaker.

Anyway, I added a couple of things

- a 'direct output' like typical fender circuits : 270R and 2K2 resistive divider off the
  speaker tap

- a tone stack defeat switch

- a pentode/triode mode switch

- a variable feedback network

MAN! This thing kicks ass in a whole bunch of new ways.

As a guitar amp, it's just unbelievable with the 'tone stack off',  'no feedback', 'pentode mode' and
a sensitive 12" guitar cab.

No way I imagined a single 6V6 could drive a 12" 50W speaker box like that. It really screams!
Like a Marshall with a giant roaring midrange.

The great thing is the sound translates thru the 'direct out'.
Recording with it basically captures that wild raging storm of sound.

The other modes give a range of tamer options and using a hifi speaker (less sensitive than a guitar cab)
tames it further.

Anyway, my point is this - I'm never going to bother with 12A_7 series type tubes for preamp distortion again.

The heavily driven 6V6 pushed thru an SE traffo then padded down to a direct out for recording literally
evacuates all over every other crunch/overdrive/distortion thing I've ever used.

My 'current' projects using this kind of thing are :

- a Redd47 preamp with a 6AS6 gain stage -> Angelfire EQ -> Poorman 660 limiter
  with a parallel feed to a pair of telefunken SE EL95 amps that have switchable speaker outs or dummy load
  and a resistive divider 'direct out'

- Fender preamp and EQ with 6AS6 gain stage -> AWA style limiter (loosely adapted!)
  with  a parallel feed to a Triode Electronics SE 6V6 amp with a switchable speaker output or dummy load
  and a resistive divider 'direct out'

Can't wait! These will also be capable of tamer settings with mic/line inputs as well as guitar/bass.


Anyway - for those looking for crunch and distortion, don't forget an overdriven 6V6 SE amp
with a direct out!  It 'rawks'. Especially with a compressor/limiter.

Cheers

 

[mulletchuck]

awesome!  post some soundbites of it!    and perhaps a schematic? 

 

[raysolinski]

Nice! That is what I am looking for...I breadboarded several Champ style low watt circuits and I really liked them...any chance you could post a schematic or layout? I suppose I could deduce what mods you made by your description but...just in case my super powers aren't functioning.... ;D

Ray

 

[maxwall]

Alexc ,

You can use a 6AQ5 the same way as a 6V6, not long ago I built a Dual 6X4 rectifier guitar amp with a Dual
6AQ5 push pull output using big cheap iron . output ungapped probably class A/B. This amp drove a 4x12 marshall
cabinet to my surprise . The output transformer in the amp had multiple taps 4, 8 ohms etc... for various speaker
experiments. I like the ruggedness of the 6v6 over the 6AQ5 and the fact that the 6v6 stays firmly in a octal socket
compared to the small socket of the 6AQ5. But the 6AQ5 has a sound I like. Volume level 1-4 clean , 5+ gave distortion quality that could not be matched by a pedal. The amp was very spanky 14-18watts.

Note : 6AQ5 is found in the LA2A , 6X4 rectifiers are found in pultec EQP1A

Short story is it was cheap to build and sounded very nice. I recall that SE amps , you must use a gapped
output transformer. The best sounds always came thru a Alnico type speakers.

Nicest caps for the tone circuits were always PIO , Silver mica, old beeswax caps.

I would be interested in seeing the a pentode -triode switching circuit example , I've been wanting to try this out.

I'm currently building a amp with some 697X ans EL84 tubes. But I always generally go for simple one knob
tone circuits or switched rotary tone circuits and let the tubes and speakers do the rest.

 

[alexc]

I'm not much for drawing schematics,  I'm afraid!

It's pretty straight forward - find the fender Champ AA764 schematic on the net.

- the pentode/triode switch is to add a 100R 5W resistor in series with the screen on the 6V6
  which goes to the centre terminal of a DPST switch.

  One pole goes to plate (triode mode). The other pole goes to the regular screen B+ (pentode)

  Use a robust switch because of the HV which will be on it.

  It makes a major reduction in power out, as expected, and so is very useful in taming the
  'no tone stack' mode. It is my favourite. Just sounds awesome.

- the tone stack bypass switch is to add a DPST switch with the centre terminal connected to the
  Volume pot input.

  One pole is connected to the output of the tone stack (treble pot wiper) for the regular tone stack in circuit
  The other pole is connected to a 0.22uF 600V capacitor with the other side of the cap connected to the
  AX7 first stage output on the plate.

  Switch can be a mini - there is no HV on it

- direct out is a standard resistive divider off the output transformer secondary 'hot'
  270ohms across the 'direct out jack' to ground, 2K2 from transformer secondary to jack

  You can see it on Fender schematics like Bassman 135, Concert, Super Twin etc

- feedback is just a 100K pot from output of transformer secondary to cathode of first stage AX7
  Just a regular pot and experiment

Electro, I may well try the 6AQ5 - I have a bunch of them and I have a liking for these small
high power pentodes. Robustness is not a problem, these are just for home use!

Have to look at a 697X - don't know that one. I luv EL84's though. Sound great, but quite
a heater current pig!

It's a lot of fun to experiment with all this stuff. My main SE amp build has 2 parallel 6550 finals
with russian 9pin input tubes, 6SL7+6SN7 around the tone stack. Into a self build 15" Jensen open cab.
It's in the early stage, but I have an inkling it will be LOUD!

All good. I especially like the small watt brutes though.
I use it a lot more than a BF Super I recently finished.

What's great is jamming with friends using one of these low watters and being able to
direct out to the DAW and capturing a good part of the magic. I never really successfully
did that before - always was splitting and going thru something else to daw.
Not the same.


 

 

[lassoharp]

As a guitar amp, it's just unbelievable with the 'tone stack off',  'no feedback', 'pentode mode' and
a sensitive 12" guitar cab.

Yep.  I prefer to leave tone stacks out altogether when possible.  I put a 4 position high pass filter on the input of an "18W" clone and it works great for removing boom from closed back cabs.  Highs are already there without tonestack.  Add maybe simple bright switch and you're good to go.

Try ef-86(or any suitable pentode)  > 12Au7 ( 2 stages) > SE 6BQ5 or 6V6.  =  The Beatles "Revolution" Intro sound. 

 

[CJ]

you can also try 6sn7 tubes in the pre amp.

octal sockets are easy to wire and the more big tubes on the chassis, the more impressive it looks to all the other amp geeks, 

 

[gemini86]

You can also find 12v6 on the cheap on ebay...

I'm plotting a mini 6sj7 into 6v6 (fender champ, any?). Just have to make the time...

 

[alexc]

Great to read the opinions of like minded types.  Thanks kindly for sharing 
Nothing makes me happier than guitar tube tweeking and vari mu tweeking.

>Try ef-86(or any suitable pentode)  > 12Au7 ( 2 stages) > SE 6BQ5 or 6V6.  =  The Beatles "Revolution" Intro sound. 
Yep something like that right now with a vari mu for good measure. a 3RU with 11 audio traffos and 10 tubes.
Why? Because I can!

> octal sockets are easy to wire and the more big tubes on the chassis, the more impressive it looks to all the other amp geeks
I'm using the 6SN7 and 6SL7 in all my  'premium' stuff now.
Since my first 6L6 + 6SL7 SE hifi amp, been hooked on the big fellas.
Just want to use them for everything  8)

I just did some hifi monoblocks
using Jensen input traffo -> 5687 tube (one stage only) -> 6SN7 PI -> EL34 PPs
Just starting to test now. I've got high hopes.
They are for my main studio monitors - need to swallow high level inputs.
Feeding some mid 70's Sansui 12" full range speakers around 92dB sensitivity

My current top of the line is 6550x2 SE with 6SN7 parallel'd halves as finals driver
and a 6SL7 as a gain stage +CF feeding a tone stack like a tweed high power twin.
Using a russian 9pin for input1 with the second half as an extra gain stage,
and another for inputs 3,4 done fender 'mixing stage' style.

6SJ7 I also would like to try. Something so sexy about it. (I think!)

12V6 is something I'd like to try on some channel strip things -
except I have done so many, I really should stop!

I keep saying ENOUGH! But then do another one.
My bank balance hates me.
Oh well, at least I stopped buying guitars!

This is DEFINATELY my last amp. :'(

I mean, DAMN. I have to finish some vari mus I have ready to go!

Cheers to you all

 

[baadc0de]

It's so hilarious that groupdiy.com places an amplitube ad below your post alexc got me cracking first thing in the morning lol

 

[alexc]

I use amplitube in my office! When I'm doing software development  ;D

It's pretty cool to write code, watch Futurama, Skype friends and Amplitube with a Jazzmaster all at once!

But when the serious musos visit, only the real deal will suffice.  8)

 

[alexc]

Lassoharp - I like your suggestions!

I'm going to try that soon.

 

[okgb]

Second the 6sn7 sounding good , but getting a direct gtr to be pleasing is a BIG task ,
often o.k. on distorted stuff , but reveals itself on cleaner gtrs .

It's a different vibe to drive it from the front but nothing quite gets that like a booster .
byoc has a circuit for a switchable Germanium / Si  / mosfet  , where it's not distorted
by itself but a little grit into some grit  get a 70's feel like the too much gain things now
just don't do .

try playing with different resistance to ground for the tone defeat and maybe some kind of treble bypass
if it gets too woofy ,  yep small single ended amps are fun !
Here in Winnipeg there was an amp build Gar Gilles who started the Garnett Co.
and made what was basically a champ with a load on it as an overdrive named
" the Herzog " in the late 60's  Used by Randy Bachman in the Guess Who for the song American Woman

 

[Matador]

A Champ circuit with a 6SN7 is a great piece of kit for the studio.  I built one several years back that I converted to a Baxandall tone stack.  I find that type of tone control works best as it much easier to get a true "mid boost" tone which mixes very easily.

I'm torn between the EL84 and 6V6 as the output stage though:  I built a version of each.  For the tight clean distortion tones (and higher volume) the EL84 in pentode wins.  For the raunchy SRV tone it's hard to beat the 6V6 in triode.

 

[alexc]

Hey Greg,

That's some interesting factoid, re American Woman. I really wuv the guitar in that!
I have to see if there's an old clip of it.

I can believe someone making a company on a 6v6 SE -> dummy load distortion box, like Mr Giles.
I have a lot of distortion boxes : SS, tube, digital and so on - some of them TRES expensive

(like the Roland VG8 - before there was Amplitube!)
(still does the best detuning and weirdo fx in the biz, tho')

All of them have their merits, but nothing does it for me like the 6V6 SE with direct out is doing.
At least for now!

Funnily enough, I find clean-ish to moderate crunch direct to daw fairly easy.
All those channel strip diys I've been doing.

Favs are one which is a fender style pre -> la2a
and and several with countryman DIs into a variety of neve-ish, 1176-ish and pultec-ish blocks

For me, the out and out distortion direct to daw has been the hard one.
Not any more!

Matador - I am also a big fan of the Baxandall circuit. Although lately I've been trying the Angelfire EQ circuit.
Pretty similar, I think. And I can understand the love for the EL84. I  think it's a fine tube and I'd like to
do more with it. It holds up to hifi PP duties brilliantly. My main 'test' amp is a 60s hifi PP el84. BIG sound.

But yeah - been on a Fender BF Super SRV, 6V6 SE, 6L6 PP, harmonic vibrato thing for a long time .
Tried out a fair few Fender tone stacks now.

Now branching out to some big parallel SE with 15" pine boxes!

And I think that will just about  do it    ;D

 

[CJ]

6sj7 is the same as ef86,

try one in grid leak for max compression and max s/n, but hey,
:

 

[alexc]

Thanx CJ

'grid leak compression'

I'll just do some learnin' on that and get back. 

 

[okgb]

Sounds like the pres / comps are helping you on the d.i. side
my best results have been with a palmer d.i. into a millenia STT-1 ,
I think the transformers help it feel better , but for me there can be
an edge of " uptight constipation  " feel to direct  , can't be afraid of liberal
amount of eq & compression , especially for headphones

Where's the easiest place to post audio files ?

 

[alexc]

I really hate that uptight constipated feeling  ;D  whether direct or otherwise

Certainly I like to use a whole lot of eq and compression and gates too!

One thing a digital desk is good for is handling a whole bunch of guitar effects feeds and cross feeds.
Cleans them up nicely with the gates and allows handy mixing to get an interesting daw feed.

Not sure where to post audio files sorry.

 

[okgb]

Something you might dig is switching bigger resisters into the cathode of the 6v6
I think i went up to 1.5k on a similar amp i have , it gets a little dirtier but in a loud amp way
resisters should be at least a couple of 5 watt to be safe

I'm not sure if others refer to this as power dumping but it's an idea that Gar gave me
[ he actually gave me the amp , probably tried everything at least once in all the years
he made amps , he was waay ahead of the 80's amp slaving ]