Fender Powerhouse Strat Boost - Been reverse engineering...

[Craig V]

This circuit is from the Deluxe Powerhouse strat, a 12dB midboost, in the same vein as the Clapton 25dB booster.  Here are my findings:

-The circuit is 95% the same as a Clapton circuit

-One of the 10uf voltage filter caps that the Clapton has isn't present in the Powerhouse circuit.

-After the last resistor, there is a 1nf cap to ground present on the PH circuit not on the Clapton circuit.

-Lug 1 of the mid pot has a 24k resistor soldered to the back of the pot (ground) on the PH, not present on the Clapton

-Lug 3 of the mid pot has a 47k resistor soldered to the back of the pot (ground) not present on the Clapton circuit.

That is it.  Would these account for the 12dB vs the 25dB in these two circuits?

[sir_modulus]

maybe the last two might. This (i'm guessing) might take away some of the signal, thereby reducing the boost. The first is a P.S. filter, for a cleaner supply, and the second is a small filter to filter some freq's out.

[cd]

This circuit is from the Deluxe Powerhouse strat, a 12dB midboost, in the same vein as the Clapton 25dB booster.  Here are my findings:

-The circuit is 95% the same as a Clapton circuit

-One of the 10uf voltage filter caps that the Clapton has isn't present in the Powerhouse circuit.

-After the last resistor, there is a 1nf cap to ground present on the PH circuit not on the Clapton circuit.

-Lug 1 of the mid pot has a 24k resistor soldered to the back of the pot (ground) on the PH, not present on the Clapton

-Lug 3 of the mid pot has a 47k resistor soldered to the back of the pot (ground) not present on the Clapton circuit.

That is it.  Would these account for the 12dB vs the 25dB in these two circuits?

Filter cap doesn't affect anything much.  1nf cap to ground is on the EC factory schem which kills harsh highs around 3khz, no big change there.  Those midpot resistors would account for the difference, one cuts the output from the midboost circuit, the other changes the taper of the volume pot slightly.

[Craig V]

1nf cap to ground is on the EC factory schem which kills harsh highs around 3khz, no big change there.

cd, I've looked at all the Clapton schematics and haven't seen that cap.  On the clapton I count 10 caps, PH has 11 (ignoring the PS caps).  But, on the "Clapton_Layout_fact" this cap is accounted for.  I might be getting confused.  

Another wierd thing is there is no R12 or C12 on the factory board.  Looks like the person who makes these might have something against the number 12  :shock:  :wink:

[cd]

I'm looking at this schem:

http://www.blueguitar.org/new/schem/_gtr/ec_schem_fact.jpg

It's C13 on the very right, before the mid pot.  It forms a low-pass filter with R20.

[Craig V]

Yes, I see it there.  My mistake, it's not on any of the other versions that I see.   :oops:

The transistors on the Powerhouse are MSPA18 and 2n5087.


Did you notice there is no 12?  

[Gilles C]

Thanks for your work. I'm always interesting to know these details about different versions of the same circuit.

I wonder what difference it makes in the sound, beside the signal level.

I'll have to try that, both versions with the same guitar.

Gilles

[Craig V]

I removed both resistors, and cd was right.

The 24k off of lug 1 changes the taper.  With it removed it can't go as clean either.

The 47k changes how overdrive it will get.  

It would be easy to make it switchable between 12dB/25dB modes.

Let me know how it sounds.