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FDP Forum / Amp Mods, Repairs, and Projects / Power Scaling

quindecima

U.S A.

May 10th, 2017 10:19 AM   Edit   Profile   Print Topic   Search Topic

Anybody have a good power scale for the USA blues deluxe?

Peegoo
Contributing Member
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I've got my own

double-cross to bear
May 10th, 2017 03:29 PM   Edit   Profile   Print Topic   Search Topic

If it were me, I'd get a pair of Yellow Jacket tube adapters and install two EL84s. That will cut the amp's output power by about half.

Peegoo
Contributing Member
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I've got my own

double-cross to bear
May 10th, 2017 03:30 PM   Edit   Profile   Print Topic   Search Topic

Looky

here

quindecima

U.S A.

May 10th, 2017 11:04 PM   Edit   Profile   Print Topic   Search Topic

That is not what I wish to do. I want to scale back the volume to a "practice in the house" level and still have the grit that high volume gives it.

Hammond101
Contributing Member
**********

So. Cal. USA

May 11th, 2017 10:08 AM   Edit   Profile   Print Topic   Search Topic

Try the volume pot in the FX loop thing. Forum member Steve Dallman has a schematic of how to put one together in his profile.

The grit you hear is mostly preamp tube breakup. The power section is pretty clean all the way up. The volume pot box works well.

Note it will never be like an amp turned up to the hairy spot just do to what the volume does to your ears.

Peegoo
Contributing Member
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I've got my own

double-cross to bear
May 11th, 2017 02:24 PM   Edit   Profile   Print Topic   Search Topic

This

circuit.

Hammond101
Contributing Member
**********

So. Cal. USA

May 11th, 2017 02:40 PM   Edit   Profile   Print Topic   Search Topic

A new name for that device....Chooch box!

quindecima

U.S A.

May 11th, 2017 06:32 PM   Edit   Profile   Print Topic   Search Topic

My first choice was going to be this http://www.londonpower.com/power-scaling-kit-fixed-bias

But I think I will try the gizmo that PeeGoo sent me

pdf64

UK

May 16th, 2017 04:58 AM   Edit   Profile   Print Topic   Search Topic

For the purpose of getting pre-amp overdrive, I don't perceive the benefit of putting a volume control in the fx loop in this amp, see linked schematic?
As it already has a master volume right before the loop, ie R21.

An additional master volume between the phase splitter and power tube grids would be a lot simpler and cheaper than power scaling, whilst having most of the benefits.
Search for the LarMar master volume.
Bear in mind that nothing is going to sound as good as the amp / speaker actually being loud.
The closest I've found is a FluxTone speaker, but that's $$$ these days!

External link

(This message was last edited by pdf64 at 07:09 AM, May 16th, 2017)

Steve Dallman
Contributing Member
**********

Merrill, Wisconsin

Age is just a number...mine is big
May 16th, 2017 07:58 AM   Edit   Profile   Print Topic   Search Topic

A leveling controlling device in the loop allows turning up the clean channel and gets the controls of both channels off their touchy low settings. Decent distortion can be had from the clean channel.

I had a Blues Deluxe (orignal) and did a lot of experimenting and modding on it. At church, volume was an issue, but the thing sounded so good turned up. The BD has a rather weak drive channel, which was designed to be more of a louder version of the clean channel rather than a distortion channel. (Fender answered complaints about that by issuing the Hot Rod series.)

I got the amp to where both channels sounded great, but at very high volumes, then tried patching a pedal into the loop to drop the volume. I used a bass compressor pedal, but with the compression turned down all the way, just using the level control to bring down the volume at the loop.

To my surprise, the amp sounded the same, just at lower volume. The clean channel was breaking up marvelously and the drive channel was fierce.

Just using R21 does neither.

I do love post PI masters, especially a stacked pot with the two added blocking caps and have been putting them in amps since 1980. I've used a lot of cross line masters in smaller amps.

The disadvantage to a post PI master is as you turn it down, the presence control becomes ineffective. For me, this wasn't a problem as the quality of the distortion was so good.

Most think of "power tube distortion" as superior to preamp tube distortion. But much of what we think of a power tube distortion is just the PI distorting and the power tubes amplifying that. A post PI master brings the PI into the distortion picture.

I put a lot of post PI masters into Marshall heads in the 80's...sometimes replacing the pre PI master in those heads that had them. Many of the players were using attenuators which at that time were Scholtz Power Soaks or Altairs.

ALL preferred the post PI master to the sound of the Power Soaks.

pdf64

UK

May 19th, 2017 05:41 AM   Edit   Profile   Print Topic   Search Topic

Thanks for your 1st hand user experience there Steve!

quindecima

U.S A.

May 21st, 2017 09:11 AM   Edit   Profile   Print Topic   Search Topic

Steve,

Do you have a schematic for the Post PI mod on the USA Blues Deluxe?

FDP Forum / Amp Mods, Repairs, and Projects / Power Scaling




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