6SJ7 Pentode 18 watt Lite...Formerly the ABSOLUTE Minimum

StarGeezers · Post by **StarGeezers** » Sun 11/28/10 5:45 pm

Insane , we've not tried BBs one knob TCs , I didn't think he liked any of them after trying , and the existing Tweed TC really sounds great now !!! TTC is really lossy ... would be a great alternative if you had excess gain to throw away ... The mid sweep effect is Great for dialing in a certain tone ... I hear if we upped the R values to 350K , it might be less lossy .... haven't tried that yet ...
I'm really Happy with it being back to the way it was before ... Really LOUD !!!

Dustpuppy · Post by **Dustpuppy** » Mon 11/29/10 9:34 am

Does anyone have a schematic for That Tone Control?

bigbeck · Post by **bigbeck** » Mon 11/29/10 10:59 am

It's just a mid control from a Matchless amp. I think it was copied from an old (50's maybe) Gibson amp.

Here's a couple of others to try. I tried all of them and i think they work better than THAT.

Gibson 'Gold Tone' GA-15RV This is like a TMB but mounted on a single dual ganged pot. I liked this one

Framus Cobra - Mid control. I liked this one too.

Matchless Cheiftain Mid control - an improvement over THAT

Epiphone EA-12RVT - didn't like it at all

Make sure you install/remove a coupling cap preceding the tone control as per the schematic. Otherwise,they will not work properly. It's an easy mistake to make when testing tone controls.

R .Fay posted a single knob tone control on this board in 2007. It was a Marshall TMB on a single pot. I installed it in my 5E3 and it works very well for me. The Framus Mid control also found a permanent home in my SE KT-88 build.

The trouble with tone controls is that they sound different in different amps - just like speakers.

Edit: The R. Fay tone control was posted on AX84

StarGeezers · Post by **StarGeezers** » Mon 11/29/10 12:15 pm

Dust , http://www.wattkins.com/files/wattkins/ABMin+BTC_1.jpg Shows THAT in the AB Min .

Big , Thanks !!! ... was kinda' wondering about what you found out ...

StarGeezers · Post by **StarGeezers** » Wed 12/01/10 4:02 pm

Guys , finding the amp a bit bassy , not flabby ,just a strong bass, I swapped the first .022uf coupling cap for a Russian KY PIO .015 uf , and ran a 230pf treble cap across the volume pot .... Much better now !!!

Rock Mumbles suggestion ...

Just FYI!!!

Dustpuppy · Post by **Dustpuppy** » Wed 12/01/10 5:39 pm

I added That Tone Control to my 2 6sj7 amp last night and it did work to tame some of the distortion making it much more usable. The board was built and installed already so I added the components P2P on the pots. The one thing I notice is that all of my treble is cut by about 3 o'clock and all I'm left with is bass. It's possible that it's wired incorrectly but I did follow the schematic that Geez posted. Any comment?

StarGeezers · Post by **StarGeezers** » Wed 12/01/10 6:10 pm

DP, That TC is kinda' weird like that .... That's why I got rid of it ... The new changes make it sound much better now , without THAT TC ...

You may want to check your wiring ??? MY TTC sounds good unless you go to the extremes on the pot ... either way ...

insanecopilot · Post by **insanecopilot** » Wed 12/01/10 10:50 pm

StarGeezers wrote:Guys , finding the amp a bit bassy , not flabby ,just a strong bass, I swapped the first .022uf coupling cap for a Russian KY PIO .015 uf , and ran a 230pf treble cap across the volume pot .... Much better now !!!
Rock Mumbles suggestion ...
Just FYI!!!

SG i used a .0047 coupling in mine along with a 22uf cathode bypass cap on the 6sj7 which seems to work for me. The 22uf gives it full range while the .0047 cuts the mud. I really like the sound of the 6sh7 in this amp too.

insanecopilot · Post by **insanecopilot** » Wed 12/01/10 10:52 pm

Never liked caps on pots myself, I try to find other ways to tone shape.

StarGeezers · Post by **StarGeezers** » Thu 12/02/10 7:02 am

Insane , it was all I had at the time ...

I do need to order yet More parts ...

It is working/sounding good now !!!

May have to use this one for the recording session Sat. ... and then again , it may be TOO LOUD !!!

StarGeezers · Post by **StarGeezers** » Wed 12/08/10 8:28 am

Although I brought the Ab Min to the recording session , plugged right into the board ... Big Mistake !!!

Didn't have My Tone, buggered the solos (distracted by the board monitors "crappy" tone) ... grrrr!!! Going back , with the amp, to "touch Up" the leads ..

Dustpuppy · Post by **Dustpuppy** » Sun 12/12/10 3:11 pm

I think you've created a monster! I just finished building an AbMin with tweed tone control using EL34's in the output section. This amp sounds pretty good but bassy. I think I'm going to try adjustingthe coupling caps and see if I can balance out the tone a bit.

What's next? I'm going to try building this with a quad of 6v6's.

insanecopilot · Post by **insanecopilot** » Sun 12/12/10 3:55 pm

Dustpuppy wrote:I think you've created a monster! I just finished building an AbMin with tweed tone control using EL34's in the output section. This amp sounds pretty good but bassy. I think I'm going to try adjustingthe coupling caps and see if I can balance out the tone a bit.

What's next? I'm going to try building this with a quad of 6v6's.

What are your values for all your caps? On my single ended double 6sj7 i use only 1uf on my cathode bypass caps, .022 coupling caps, and 1000uf cathode bypass cap on the 6v6. It is fine. I have a 220k/ 470k voltage divider between gain stages to control gain. What are you using?

Dustpuppy · Post by **Dustpuppy** » Sun 12/12/10 8:18 pm

I switched the coupling cap in the pre to an .0047. and I'm using a .68u as a bypass on the poweramp.

insanecopilot · Post by **insanecopilot** » Sun 12/12/10 8:56 pm

Dustpuppy wrote:I switched the coupling cap in the pre to an .0047. and I'm using a .68u as a bypass on the poweramp.

.68 on the power tube cathodes? Never heard of that. 50uf or 1000uf anything in the middle makes it boomy.

StarGeezers · Post by **StarGeezers** » Mon 12/13/10 8:12 am

Well I ordered some .0047uf caps , just to try out ... Got a 2.2uf on the 6SJ7 cathode + the Jedi cap ... 220Uf on the power tubes cathode ... May have to do some changes there ... Thinking of just cutting out the 2.2 uf on the 6SJ7 and reducing the 220Uf to something more reasonable ... The amp sounds Good now , but still a little bit on the bassy (Not flabby)side ... especially through closed back speakers... so either I fix this or join a Metal band ...

Whoa !!! Noticed all the pics and schematics have disappeared...

WTF???

Post by **zaphod_phil** » Mon 12/13/10 11:52 am

Flabby bass in the power section will need a pretty big change in value of the "Jedi cap". Either go low, down to 50uF or less or else go high, to 1000uF and above. 220uF is neither here nor there.

However, if the bassiness is really coming from the preamp, then you may need to work on that a little further.

Noticed all the pics and schematics have disappeared... WTF???

You may have noticed that the site is in a damaged state at the moment, while we embark on a total rebuild.

Dustpuppy · Post by **Dustpuppy** » Mon 12/13/10 11:55 am

.68 on the power tube cathodes? Never heard of that. 50uf or 1000uf anything in the middle makes it boomy.

I was working on the theory of " Let's try this and see if it breaks...." Not sure if it was a success but, it doesn't sound bad now. I'll have to swap it with a 220u and see if it sounds different.

Does anyone have an idea for an upper mid boost?

Brett

StarGeezers · Post by **StarGeezers** » Mon 12/13/10 5:01 pm

ZP , will do !!! Good Luck on the re-build !!!!!

DP, How about a 1000pf parallel to an R after the coupling cap ...???

Tweaking sure is FUN , and the more we tweak , the Better it sounds ...

Dustpuppy · Post by **Dustpuppy** » Mon 12/13/10 7:06 pm

DP, How about a 1000pf parallel to an R after the coupling cap ...???

Tweaking sure is FUN , and the more we tweak , the Better it sounds ...

Here's a silly question, would that be before or after the volume pot?

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6SJ7 Pentode 18 watt Lite...Formerly the ABSOLUTE Minimum