Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Madison on August 19, 2011, 07:28:41 pm

Title: VVR. Entire amp or power section?
Post by: Madison on August 19, 2011, 07:28:41 pm

Which is your preference?
Looks like just the power section is less work and parts?
This for an SE EL34 amp.

Title: Re: VVR. Entire amp or power section?
Post by: Boots Deville on August 20, 2011, 02:08:19 am

I built a tweed style SE EL34 amp where I scaled just the EL34 plate and screen, and am happy with the result.

I added an additional PS node for the preamp to give it some additional filtering since it was getting "cheated" out of the filtering for the place and screen due to the VVR.  If its a new build, no problem.  In an existing build it might be a hassle.

Title: Re: VVR. Entire amp or power section?
Post by: jojokeo on August 21, 2011, 01:58:39 am

I did the same thing as Boots suggests and love it. I don't turn the VVR down as much as I thought I would before I built it but it's there if you want it and it works and really soungs great. I've got about 265v to the preamp load resistors w/ the VVR up and it raises to 300v when it's fully turned down due to less loading. I use the VVR as the Master Vol and it's all you need. I couldn't imagine needing or wanting a regular MV and the VVR for this type of amp. I hear it's good w/ a PP amp w/ more power but for only SE there really is no point IME. I just posted a pic here of it after swapping my PT. http://www.el34world.com/Forum/index.php?topic=12160.msg112890#new (http://www.el34world.com/Forum/index.php?topic=12160.msg112890#new)

Title: Re: VVR. Entire amp or power section?
Post by: Madison on August 21, 2011, 11:38:13 pm

Great info.
I'll see how it goes.
Thanks a lot!

Title: Re: VVR. Entire amp or power section?
Post by: LooseChange on August 22, 2011, 06:19:49 am

Done many amps with just the plates and screens regulated. I like this way the best.
I agree with jojokeo, once you get over the cool bedroom levels, turning it down just a bit to get the grind you want at any volume is the way I use it too.

Title: Re: VVR. Entire amp or power section?
Post by: Madison on August 22, 2011, 07:49:50 am

Ok,I am sold.
I will ace the existing 250K MV on this amp, replace with a resistor, and have that hole the VVR.
Anything to worry about running wires under the board for interferences?
No shielded wire necessary?

This actually helps my a lot with the cabinet.
I have a hole drilled in the rear of the chassis for the VVR pot, I guess I can cover it up with that back panel.

>>PS node for the preamp
PS?
What is it?
(I am going to kick myself when you guys tell me)

Thanks!

Title: Re: VVR. Entire amp or power section?
Post by: Boots Deville on August 22, 2011, 08:33:21 am

sorry.  PS node is "Power Supply Node".  An extra dropping resistor and filter cap in the power supply to filter the DC to the preamp.  The preamp won't benefit from the filtering for the plate and screen, so I've had to install more filtering for the preamp in a few VVR installations.  You may not need to, but if it's a scratch build, might as well leave room for it, if you have the space.

Title: Re: VVR. Entire amp or power section?
Post by: Madison on August 27, 2011, 08:49:24 am

This works really well!
Thanks guys.
BTW, Boots, I definitely needed the P.S.!
On an SE amp it works very well, can't wait to try it on a 50 watter.

Onward!

Title: Re: VVR. Entire amp or power section?
Post by: harryk on August 27, 2011, 12:35:02 pm

Quote from: Madison on August 27, 2011, 08:49:24 am

This works really well!
Thanks guys.
BTW, Boots, I definitely needed the P.S.!
On an SE amp it works very well, can't wait to try it on a 50 watter.

Onward!

Hi Madison! Did you scale the whole amp or only PA or PI+PA?

Title: Re: VVR. Entire amp or power section?
Post by: Madison on August 28, 2011, 12:33:45 am

>>Did you scale the whole amp

Only the power tube.