Geezer's TMB-trim boost relay

[adamG]

Hi Guys,

I am just assembling Greezer ver. Tweed BluezMeister...
Could anyone explain me the functionality of Trim Boost relay acc.to attached schematic?
Forgive a jerk question,but I do not understand how the circuit there functions.
Is it three connections options, where the middle one is a common and the top/bottom are output ones to pot?
Also, is the top directly connected to trim boost pot ,then the common conn.via cap to pot ,while the bottom to the ground?! 
Or better, could anyone be so generous and put on paper/jpg that relay layout?

Thanks in advance!

Regards,

Adam

[sluckey]

Just think of the relay as a SPDT switch. The center contact is common. In the down position the bottom end of the trim pot is connected directly to ground. In the up position the bottom end of the trim pot connects to ground through a 25K pot. This additional pot allows you to fine tune the amount of boost. The .68µF cap does nothing.

[tubenit]

Look at the OD "hi-cut" and then at the trim pot with the .68

Do you see some similarities? 

It's been a long time since we worked on the Tweed BluezMeister design, so I am not sure about that drawing?  I am thinking it may be drawn incorrectly?

With respect, Tubenit

[adamG]

Just think of the relay as a SPDT switch. The center contact is common. In the down position the bottom end of the trim pot is connected directly to ground. In the up position the bottom end of the trim pot connects to ground through a 25K pot. This additional pot allows you to fine tune the amount of boost. The .68µF cap does nothing.

So,does it mean trim boost pot is activated/disactivated by SPDT switch?
Acc.to above schematic ,it's not possible to ground trim pot while boost pot is still activated,right?

[tubenit]

Adam,

I'd just eliminate the .68 cap.  You don't need it, IMO.   Yes the spdt switches the boost pot in or out.

With boost pot out, the trim pot goes straight to ground.

With boost pot in, the trim pot goes thru boost pot to ground. One could have simply uses a fixed resistor there instead.

with respect, Tubenit

[adamG]

Look at the OD "hi-cut" and then at the trim pot with the .68

Yes,I do;)
So,the idea of this solution is put the signal through the cap to pot or directly ,then to the ground?
But,without the cap We would have two pots in series,right?
You worked on that design a couple years ago,but just now I continue my build of that famous amp,sorry;)
A year ago I got started my build.You know,I do not work in speed.I like to enjoy every little step of the amp voyage.So,it must take amount of time..

Thank you Tubenit and Sluckey.

Regards,

Adam.

[adamG]

Adam,

I'd just eliminate the .68 cap.  You don't need it, IMO.   Yes the spdt switches the boost pot in or out.

With boost pot out, the trim pot goes straight to ground.

With boost pot in, the trim pot goes thru boost pot to ground. One could have simply uses a fixed resistor there instead.

I see,but maybe does it make sense to change the sonic character of trim/boost pots with .68uF cap?
What influence do have two pots in series?

[tubenit]

Adam,

This is essentially what my Tweed BluezMeister is.  Note there are different values in places.  I love this amp and get many compliments on it's tone.

I prefer the PAB and midboost which can change both the clean channel and the OD tone also.  I have tried the trim OD boost idea and didn't
care for it.  I also strongly prefer separating the middle and bass pots from one another as shown in this attached schematic.

You can build a TBM like this still using Hoffman's board just fine.

With respect, Tubenit

[adamG]

I prefer the PAB and midboost which can change both the clean channel and the OD tone also.  I have tried the trim OD boost idea and didn't
care for it.  I also strongly prefer separating the middle and bass pots from one another as shown in this attached schematic.

The thing is I've already made chassis, gathered all elements, got started assembling and It'll be finished within 2-3 days.
Therefore, I must follow the schematic chosen mamy months ago...
There's a room for trim boost pot, also;)
Besides, I deeply like jazz/rock option. So, I'll stay with it.
I think, I'll follow your idea of midboost ,that means I'll change some components values.
Separation of bass and middle pots is possible, because those connections can be made on pots.
Main board is put inside the chassis.That's the reason.

Thank you very much.

Regards,

Adam

[tubenit]

Adam,

Sure it makes sense to use the components that you have. That's understandable.

IF you find that you want more bass and want to boost the mids some more, then I'd recommend these small changes.

IF you don't have a 100ka pot, then I'd try a 22k or 27k resistor to ground under the 25k mid pot.

This is a really fun amp to play!  Hope you enjoy it!

With respect, Tubenit

[adamG]

Tubenit,

Thank you very ,very much:)

Do you think it is worth to provide bright switch also?
If so, then shall I put it on volume pot without grid resistor/cap going into 2nd triode or add them anyway?

Regards,

Adam

[tubenit]

Do you think it is worth to provide bright switch also?

I don't think having a bright switch is that useful.

With respect, Tubenit

[adamG]

IF you don't have a 100ka pot, then I'd try a 22k or 27k resistor to ground under the 25k mid pot.

Tubenit,

You suggested to replace trim,drive,ratio pots.
May I stay with 250k for them with resistors before, wchich is 110k(trim),68k(drive),133k(ratio)?
It might be similiar to mid pot in series with 22/27k resistor,right?
Of course, I can change the pots for 100k and keep ones of 250k for future needs,but this time I'd have change pots together with resistors?
It is a king of my own silly approach, but in this way ,changing those elements within OD stage, I'd ruin what I heard in Geezer's samples.
I really like mids, that sonic character I heard there.

Thank you in advance, very much!

Regards,

Adam

[tubenit]

Adam,

I am suggesting to only replace ONE pot.  And that is the mid pot on the tone stack in the clean channel.  Replace the 25k pot with a 100ka pot if you are separating the mid pot from the bass pot.

Look at reply #9 schematic.  Only one pot is circled in red.  That is the only pot that I am suggesting to replace. Build all the rest of the
entire amp exactly like Geezer suggested and see if you like it.

IF you can not replace it, then simply add a 22k or 27k resistor to ground.

With respect, Tubenit

[adamG]

I am suggesting to only replace ONE pot.  And that is the mid pot on the tone stack in the clean channel.  Replace the 25k pot with a 100ka pot if you are separating the mid pot from the bass pot.

Look at reply #9 schematic.  Only one pot is circled in red.  That is the only pot that I am suggesting to replace. Build all the rest of the
entire amp exactly like Geezer suggested and see if you like it.

IF you can not replace it, then simply add a 22k or 27k resistor to ground.

Tubenit,

Yes,yes.
The small misunderstanding became ,because We can see two different schematics:)
In the very begining of my topic I've published the schematic with three pots of 250k...
Anyway, if I am succesfull with the whole amp and notice that something should be changed ,I'll be doing that and asking for assistance;)

Thank you very ,very much!

Regards,

Adam

[adamG]

Tubenit,

Once more, my I ask for your assistance?
Today I fired up the amp.
I applied 5U4G rectifier. After that I've got 393VDC. I intend to stay with this voltage. I do not need the amp power beyond that voltage.
Second thing is next nodes voltages, which  are nod C approx.348V, nod D(after swapping res.for 1K) 345V and nod E 343V.
Then I have approx.197V on OD stage after the plates resistors and approx.135V pin 1 and 190V pin 6 on V1.
Do you thing I could stay with them or shall I change/lower the nod C resistor to increase voltage on the next ones?
The next issue is I think I should replace the OD pots of 250K for lower ones as you seggested.
At least Ratio pot supposed to be swapped.
What do you think about it?

Thank you in advance,

Regards,

Adam

[tubenit]

I don't pay a lot of attention to the voltages on the plates of 12AX7's.  I want them somewhere between 160v and 200v overall.  I want higher voltages for a clean tone on V1.

To me the issue is how does the amp sound?  Do you like the tone?   If so, leave it alone.

I'd change trim pot to 100ka and leave the others as you have and play it for a while like 2 weeks and then see if you want to change anything.

With respect, tubenit

[adamG]

Yes,that's the main thing the sound.
I do not like the OD sound.It is fuzzy therefore funny.
The Ratio pot must stay on very low position to keep resonable amp volume balance between clean and OD stages.But then satisfactory gain is missing.
I feel that all of the three pots trim-drive-ratio must operate on same volume.Can you agree?
To increase V1 voltages, I'll swap its plates resistors.Is it a proper solution?

Thank you!

Adam

[adamG]

I also applied DPDT switch for Full/Half output power.
I've noticed hum on Half position. Fortunately,on Full position it is gone.
What would be the reason?
Maybe with cathode biasing it is not applicable?!

[tubenit]

OK, I checked my Tweed BluezMeister.  I have around 180-190v range on preamp plates using 12AX7 tubes.  Using 5751 or 12AY7 tubes will give you much lower plate voltages.   Other then changing your trim pot to a 100ka, I think it's fine leaving the other pots alone.

Regarding getting a smooth OD tone.  Try a 12AY7 (or 5751) in V1 position which will allow for a nice clean tone and help cut down "grit/fuzz" on the OD channel.   Of course the type of caps you're using and the speaker make a difference also.  Lots of factors involved in getting a smooth overdrive.  The smoothing caps on the OD channel are important. 

Be sure to use the "enhance cap" across the entrance plate on the LTPI. It helps a lot in cutting out the high end harshness and smoothing the high frequency without losing the high frequency.  (see the schematic I posted earlier of my TBM)

Most of the time I have a 12AY7 in V1 and a 5751 in V2 overdrive.  I have a 12AX7 in the LTPI and usually use 6L6's but also 6V6's.

With respect, Tubenit

[adamG]

The caps are Orange Drop 715. On PS I put F&T electrolytic ones, also a very good quality. Plate resistors Metalfilm RN65D, the others Carbon Film Oxyde. So, it seems the decent components have been applied.
The speaker I used for yesterday's testing was Celestion G12-65 Heritage, but normally I prefere Eminance Guitar Legend, that will be connected to this amp when finished.
I just followed schematics and put 12AY7 as V1, but for V2 there was a 12AX7. Today, I'll swap it.
Also, I intend to provide 100KA for Trim pot and enhance cap. Am I see correctlly, is it Silver Mica 150p? across 100k plate resistor conn.to nod C?

Once more, thank you very much!

Regards,

Adam

[adamG]

...I separated Bass and Mid pots as you sugested but kept 0,022 caps there. I'm pleassed with that seperation and the clean sound. All of the TMB pots response properly to my ears. SPDT switching withing preamp sonically work ok. So, It seems that clean channel is ok.   
All above with 12AY7.

Regards,

Adam

[adamG]

Hi guys,

I returned to this thread after several month, because as Tubenit said:"leave this amp for a couple weeks"
So ,I did it for more than half of the year.
Today I know this amp ,with some tweaks meanwhile, is fucking great 
I really do not know what happened to my ears previously ,but the amp is a kind of desire of every guitar player.
Thank you Geezer, thank you Tubenit!!!

Regards,

Adam

[tubenit]

adamG,

You did a FANTASTIC job with that amp!  What a beautiful build and waaaayyyyy neater then mine.  I am glad you are enjoying it.

 

This is the only amp I've ever built that has gone yrs with NO tweaking at all.  I can't think of anything that I want changed on mine?

I appreciate your sharing the photos and giving us an update.  Very nice of you to do that!

With respect, Tubenit

[sluckey]

Nice looking amp!

[adamG]

You know I really like this forum. It is not as big ,famous as ampgarage, but I feel this place as my hobby home;)
With this amp I can put it on every speaker cabinet with proud.
I am proud ,because I made just everything, which is chassis, boards, tranies, cabinet, etc. Finally, It works fine. Usually, men judge that transformers must be made by profesional producers. I think ,they must not. Those two, November and Bluezmeister might be the evidence:)
Sluckey, you may believe me that this amp is not only nice looking amp, if so. It is great sounding one.
You remember, I built November 18 acc.to your schematic and layout. That amp is also great.
I think to myself, maybe I reap the fruits of labor ?! Anyway, things get better;)
Tubenit, that amp is also your share within.

Thank you very much!

Regards,

Adam