Help with Deluxe lite TMB Tone stack problem or something else..

[alfa75ba]

Hi,
I am an amateur who enjoys building amplifiers, for me and my friends.
Been frequent on this Forum (as a lurker), and been gratefull for all the help, advice and experience you guys have been giving and sharing here.
Up to now, I have built a few amps and pedals, two channel ( EF86 and Top boost) AC-15  ( one with diode and one witz EZ81 rectifier), a few Hi octanes conversions, one 18 Watt lite ( Sluckeys design but without AC-15 channel), one Tubenits TOS, one Smallbox 50 (Friedman inspired) with all the bells and whistles...
It`s been fun, and I learned a lot. With all my builds I was pretty lucky though, especially with conversions and using old tube equipment, they all turned OK, once or twice I had small error here and there, but nothing serious. Reversed OT leads , unsoldered conection, etc. Got zapped only once :-)
But for the life of mine I cannot make this Fender TMB tone stack to work properly.
It is Deluxe light inspired build, (thanks to Sluckey), with added switchable fixed/cathode bias, and 12DW7 one tube capacitor coupled reverb.
Amp works great electrically, it is loud, no hum, no buzz, all voltages seem corect, biased 95% cathode, 65% fixed.

Problem:
Amp is too bassy, bass control going from strong bass to rattling windows bass, except at zero setting. Low E string seems louder than other strings.
Treble is strong, but the Treble pot seem acting funny,it is adding treble normally from 12 o`clock to ice picking max, but turning it down towards minimum it does not only cuts treble, it takes clarity away and brings bass and mud with little volume boost. Like putting severals blankets over speaker and adding a little volume to this muffled sound. It does almost the same even with bass knob at 0.
Mid control works ok, but only with 10K pot.  25K mid pot when maxed brings also that muffled bass/mud. Same thing when I tried RAW switch ( ground lift).
Same thing when I bypassed tone stack completely ( desoldered wires) and only left volume pot between first and second triode, with 0.02 coupling cap of course.
I replaced all pots and all capacitors several times, tried different values, played with Duncans Tone stack software for months now. Tried lower value cathode bias caps ( 2.2uF first and 0.68 second) and I hear differences, less bass, more highs, at different pot settings but treble control still seems to be controling to much of everything.
Separated circuit after 0.01 capacitor (after second triode) to test the Power Amp only, plugged guitar through Timmy pedal and amp sounded very clear and trebley ( albeit not very loud) that I put back 0.047 power tube coupling caps back ( had put 0.022 before).
So, obviously I wired something wrong between V1a and V1b.  But there is almost nothing there except tone stack. Something in B+ line, filtering ?
I am using pine 1x12" open box, with Celestion Gold speaker, guitar Strat plus with Lace pickups.
When I use my AC-15 clone, Top Boost channel,  Bass knob at 10 o`clock, Treble at 14 o`clock, sound is perfectly clean and balanced. Same box, same guitar.
I would appreciate any help and advice , I am lacking experience and knowledge, obviously, to solve this puzzle alone.
...and sorry for the long post...

[jjasilli]

Are you sure the NFB is connected to the 8 Ohm tap?


Too much bass in both cathode bias & in fixed bias?

[sluckey]

I suspect a wiring error. Compare your schematic, layout, and actual wiring.

[alfa75ba]

Hi, I actually have three position feedback switch ( as per Robrob site), with 820 ohm- none- 1k5 setting. So I can test it without NFB when in doubt. It works fine.
And yes, the amp behaves the same way regardless of bias. The amp actually was cathode biased at the beginning, but I added fixed bias in hope to clean and tighten the sound , but no big difference 

Also, this amp had only tone and volume control ( a la 5E3), and sounded great with both tone and volume at noon. But a friend of mine wanted less gain and  more tonal control, so I added TMB. First wired it on pots, did not work well- just like I described. Then rewired it on terminal strip, new pots and capacitors,the same. Then I gutted everything and made new turretboard per Sluckeys Deluxe lite layout. Again new pots, caps, colorful wires not to mix what goes where and...- the same tone stack behaviour! 
But now it would be easier to troubleshoot I hope, as it is not rat nest - terminal stripes style anymore.
Will check everything again tomorrow, maybe will try again one knob tone control and will post some pictures. I do not trust my eyes anymore.

[sluckey]

Then I gutted everything and made new turretboard per Sluckeys Deluxe lite layout.

I have two layouts for Deluxe Lite. Which did you use? Post a link please. Also, post some hi-rez pics of your build.

[alfa75ba]

Guys, thank you for your posts, and trying for help, I appreciate it.


Today I jammed a little with smaller cathode resistors in V1a and V1b , 2.2uF and 0.68uF respectively,  and noticed that the sound somehow was more balanced, less boom and smaller difference in volume between uper and lower strings.

Now it seems to me that the whole problem lays actually in treble pot function. Rotating treble pot to the right brings highs but also cuts lows. And to the left, cuts highs and brings lows. But not in a subtle way but like having tandem pot and having treble and bass control with one knob.   Could the culprit be that 0.1 bass capacitor ?  Gonna replace it tomorrow.

Anyway, here are the pictures. It is still very messy build, actually this project started as an atom space sound :-) replica, hence the funny layout, but was rewired several times. Once we get it working right, gonna get new chassis and do it properly. I promise :-)

Sluckey, the board is ver.1, the longer one. In these pictures the reverb was not implemented yet, so no tube in V2 position, and loose wires are for reverb and harmless, no worry.
 

[alfa75ba]

Another question,

a friend of mine has this Brunetti Singleman amp, which by the way is really great sounding amp, and is sort of Deluxe lite circuit, one preamp tube, one phase inverter tube and 2x 6V6. Silicon reverb :-)  Cathode bias, with only 300V on plates ( my build has around 380 on cathode bias).
Its sound is very balanced, with all settings at noon sounds great. Bass, treble, just right measure. Once, when was working on it, I tried to trace tone stack layout, and I am not 100% sure, because of double layer PCB, but it is pretty close to this:

It has separated bass and mid control, and 50k bass potentiometer maybe.( I could not read the values on the pots cause soldered to PCB) but tried measuring.
Makes any sense?

[sluckey]

I suggest leave the Brunetti alone. The Fender tonestack works very well when properly wired.

[brewdude]

Are the pots oriented v, t, m, b left to right from the input jack?

Is the yellow wire connected to the treble pot?  Should it be connected to the Bass or mid pot?

[alfa75ba]

I suggest leave the Brunetti alone. The Fender tonestack works very well when properly wired.

That is what I wanted to hear.   In despair, I wired it few times like that, also tried 50kA bass pot in Fender tone stack, but gonna give that up now and stick to proven design. And hopefully make it work...

Are the pots oriented v, t, m, b left to right from the input jack?

Is the yellow wire connected to the treble pot?  Should it be connected to the Bass or mid pot?

yes, it is V-T-M-B, just like in this layout only from left to right.  Treble pot is connected to Bass pot so I choose shorter path. But, trust me, I am not sure of anything anymore 

[sluckey]

Tone stack caps... What is the value and voltage rating of the yellow cap? What is the value and voltage rating of the orange cap?

[alfa75ba]

Tone stack caps... What is the value and voltage rating of the yellow cap? What is the value and voltage rating of the orange cap?

Yellow cap 0.1uF ( 104J 630V) , orange cap 0.022 ( 223J 600V).  I put 0.022 yesterday, until yesterday there was 0.047 ( 473J 600V). Mica is 250 pF 500V. Tone stack wired as that Brunetti TS with 50K Bass pot. Gonna revert that to Fender spec and replace that Yellow 0.1 cap ASAP. Duncan TS Calculator showed real bass shaving with that 50k, I thought I might as well try.

I also put one 0.68uF 630V cap yesterday, between V1a pin 1 and tone stack. Wanted to try scoping signal through tone stack (I have that simple handheld scope with 10:1 probes) , if it makes any sense?

[alfa75ba]

OK, put tone stack values back per schematics - 0.1uF bass cap, 0.022uF mid cap, 250pF treble , pots:  250kB treble, 25kA mid, 250kB bass.

Put new 0.1uF bass cap ( old measured 99 nF, but maybe something else was wrong with it  ) , moved that red wire to the bass pot from the mid pot (although electrically connected), touched all conections with soldering iron.

I don`t know, maybe I got used to this sound now, but I think this is as good as it gets. Tone control improved, I was able to play it even with all controls around 12 o`clock settings( speaking of OCD  ). Except volume, of course :-) This thing is LOUD!

Still cannot imagine putting 25uF bypass capacitors on V1a and V1b, but this could be Output transformer-Speaker-Cab related.
Now even with 2.2uF and 0.68uF ( which I am gonna solder now for good) it has plenty of bass, but under control :-)

 Time to tidy things up and take it to my friend`s studio to test it at full volume

Thank you very much for your help and patience

Current pictures: