Tremolo TMB Reverb with 6AQ5 tubes

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Bieworm
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Tremolo TMB Reverb with 6AQ5 tubes

Post by Bieworm »

Howdie!

Yesterday I was experimenting with 6AQ5 tubes in the power section of my recent Tremolo TMB Ironside amp. I must say I was very impressed with the sound. There seemed to be more OD on tap and a little less headroom and overall volume. I liked the way they both thickened the sound and gave it a very sweet high end.
Because the 6AQ5 require a max anode voltage of 250V I had to use the 0-190V tap on my PT. (275-190-0 secondary). I landed on Va 206V Vk 6V and Rk 56R, which gave me about 80% dissipation and a very nice and sweet growl.

When I was about to wrap things up I thought of trying the tremolo first.. bummer! There was nearly no tremolo at all!

So, by means of the experiment... what if I split the B+ after the rectifier, using a string of 5W zeners to scale down the B+ for the power tubes and the PI AND a separate branch with all filter caps for the preamp. Do I use another can cap 32+32uf 500V to filter the juice for the preamp? Or is using only 1x 47uf 500V + 2x 22uf for nodes D and E plenty enough filtering?

Or is there a better way to tweak the extra voltage I'm lacking for V1?

EDIT: Since I've still got some slack on the B+ I am gonna try to set the voltage with the 0-275V secondary.. zener it down until I have Va around 250V and see if that voltage is ok for the tremolo to work as intended.
Tremolo TMB schematic Ironside mod 6AQ5 version.png
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by Bieworm »

Well I experimented with it some more by adding zener diodes in the B+ line after the rectifier. But when I put 250V on the anode (6P1P-EV spec max Va) there is still too weak tremolo for my taste.
But we run 300V max spec'd EL84 often in the 350V area.. in that regard, would it hurt to run the 6P1P-EV ( =C= Svetlana ) around 300V Va? They are supposedly very sturdy tubes with military specs...
Should I give it a go and remove some zeners to raise the B+? I will watch out for the event that those tubes fail on me...
Or do you say NO!!!! DON'T DO THAT!!??
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by JMPGuitars »

It's probably a bad idea. Best case is they might sound good for a little bit, and die early. However, they're really cheap tubes, so if you don't mind losing the $4.00 you spent on them...
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by Bieworm »

JMPGuitars wrote:
Tue 02/21/23 9:04 am
It's probably a bad idea. Best case is they might sound good for a little bit, and die early. However, they're really cheap tubes, so if you don't mind losing the $4.00 you spent on them...
Lol! I will keep an extra pair in the combo just in case
I’m going to tweak the B+ in steps of 10V up and see where that leads
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by Bieworm »

Ok… it’s fixed. I set the plate voltage at 283V and biased the tubes at 80%. Trem works nice and strong. OMG these tubes sound really nice!
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by chaliapin »

Did you drop the b plus for the whole amp in the end? Do they have the same pin connections as el84?
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by Bieworm »

chaliapin wrote:
Tue 02/21/23 1:17 pm
Did you drop the b plus for the whole amp in the end? Do they have the same pin connections as el84?
Yes.. after the rectifier i have 345V.. then an bunch of 5W zener diodes dropping the B+ to 295V at the 1st filter cap.
The 6AQ5 has a different pinout because it’s a 7 pin tube.. though I used the Russian equivalent 6P1P-EV, which is also a 9 pin tube like an EL84, they don’t share the same pinout.
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by JMPGuitars »

You don't need more than 160V to run the tremolo. So start thinking differently. What's the B+ source voltage before the anode resistors for your preamp?
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Re: Tremolo TMB Reverb with 6AQ5 tubes

Post by Bieworm »

This is where I landed..
A49E2784-1B46-4431-8788-BDBCBA2F20A9.jpeg
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