Dlx Rvrb, 360v vs 450v plates

[sonofmickel]

In a quandary...
I have been an amp "hobbyist" for 12 years now, just saying I'm not a pro.

My Weber build 6a20 Deluxe Reverb Power tranny has Red/Red 680V, Red/White 540V taps.
I am using the Weber Copper Cap in place of a GZ34, that is how the kit comes.

My choice is 450v on the plates or 360v.
It's a Deluxe Reverb, it is supposed to run 6V6 tubes but

PT is Weber W025130, 540v/680v 150ma
OT is Weber W041318, 6600 ohm, 8ohm tap, 25 watt

So...
360v, 6v6 and redo the power string to get 170v on the preamps
450v, 6l6gc and make it into a Super Reverb with undersized OT, redo power string to get 270v on the preamps.
450v, 6l6gc, power string Dlx 170v on preamp tubes.

The Weber Copper Cap supposedly produces LESS voltage than the GZ34
I swapped in the GZ34 for the Copper Cap, voltages go up about 5v, 455v or 365v depending on Transformer taps used.

[Stevem]

How do you want / need the amp to sound?

When do you want / need the amp to clip?

170 volts to the preamp section will be duller on the top end and of course have less gain along with the output stage being looser on the bottom end once that stage starts to clip due to the lower voltage it’s getting to it.

[sonofmickel]

Well, I like the Super Reverb best.

Will JJ 6V6 hold up to 450+ volts?
Will the PT hold up to 6l6GC at 150ma?

My main concern is the power section.

[Roe]

Well, I like the Super Reverb best.

Will JJ 6V6 hold up to 450+ volts?
Will the PT hold up to 6l6GC at 150ma?

My main concern is the power section.

JJs tend to handle 450v yes. the PT may not handle 6L6s with hot bias and a ss rectifier

[sonofmickel]

Found another potential problem.
Because of the high 450v B+ the Vibrato tube V5, pin1 is seeing 438v directly off the choke through the 220k resistor.
Is this too much?

Is lower voltage rated PT the ultimate fix?

[sonofmickel]

How about a rectifier that drops more voltage like a 5R4 GYA/GYB?
A GZ34 drops 30 volts giving me the 455v B+, a 5R4 drops 60-67 volts as per the Rectifier Summary cheat sheet found online.

If the ratio is correct the 5R4 should put me at 455 - 5R4 30 volts = 425v

Please correct me if I am mistaken.

It would be well worth the $20 if this would work.

Cr@p, I just measured the heaters at 6.8 volts. Variac for all my amps?

[pdf64]

A GZ34 drops 30 volts giving me the 455v B+, a 5R4 drops 60-67 volts as per the Rectifier Summary cheat sheet found online.
...
Cr@p, I just measured the heaters at 6.8 volts. Variac for all my amps?

The info in the valve rectifier comparison table found online is widely misinterpreted / misunderstood.
The voltage drops apply at the noted current, as loading esses off, voltage of all will increase.

So what's your measured wall voltage?

[lonote]

So what's your measured wall voltage?

Right ^^^

Maybe something like either of these would help:

Sluckey's Buckaroo https://sluckeyamps.com/misc/Amp_Scrapbook.pdf

RobRob's BuckMinster https://robrobinette.com/5e3_Modificati ... ransformer (wonky link, go almost to the bottom of the page)

[sonofmickel]

Thanks for the help,
Measured wall voltage this morning is 119.3v ac

Stumbled onto something. PT windings ratios...I wish the PT had a primary 130/140v tap.
The PT was hooked up to the 120v primary.
Swapped the primary to the 125v lead and ALL voltages in the amp came down?
125v primary = 433v plates, 6.5 heaters.
120v primary = 450v plates, 6.8 heaters.

I will look at the links provided.

[martin manning]

Swapped the primary to the 125v lead and ALL voltages in the amp came down?

Of course: 120/125 = 0.96, 450 x 0.96 = 432. The 125V primary has a larger ratio of primary/secondary turns for all secondaries.

[dorrisant]

I hate to sound like a broken record, but have you considered the MOSFET B+ Reducer?

https://ampgarage.com/forum/viewtopic.php?t=27035

This is exactly when/where I would use one. It is adjustable by changing one value and could be put on a switch, SPST, DPST or rotary, for whatever value of B+ you'd need.

If you're in the USA, PM me with your address. I will send you a board for free.

That way you could use the larger voltage and cater it to what your ears want. Just sayin'.

[sonofmickel]

B+ Mosfet reducer sounds amazing...yes!
Me likey!

[pdf64]

I hate to sound like a broken record, but have you considered the MOSFET B+ Reducer?
...

Unfortunately that'd do nothing for excessive heater voltages.

[dorrisant]

I hate to sound like a broken record, but have you considered the MOSFET B+ Reducer?
...

Unfortunately that'd do nothing for excessive heater voltages.

6.5vac with the 125v primary tap as opposed to 6.3vac... I would not call that excessive. Would you really worry about it?

[pdf64]

Ah, right, that should be fine, I was going off the previous 6.8V AC.