What was the output mod for Profex 2?

Ken Fox · Post by **Ken Fox** » 28 Oct 2002 3:18 pm

I can't find my old notes on this one. I remember there was a mod to the left and right opamp feedback resistors, I think, to increase the available output of these units.

Smiley Roberts · Post by **Smiley Roberts** » 28 Oct 2002 9:42 pm

Randy Beavers did mine for me. You can reach him at PulltightB@aol.com (I think that's still a working addy.)

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Mike Brown · Post by **Mike Brown** » 29 Oct 2002 6:08 am

Smiley, it's a real simple mod. Add two 10K 1/4watt resistors in parallel to R910 and R922, which are also 10K 1/4watt resistors.

If you have any further questions, contact us here at Peavey and we'll be glad to assist.

Mike Brown
Peavey Electronics Corporation

David Decker · Post by **David Decker** » 29 Oct 2002 6:04 pm

Can you do this to the original Pro Fex also?

Bill Crook · Post by **Bill Crook** » 30 Oct 2002 5:44 am

Hey,Mike Brown......

Add two 10K 1/4watt resistors in parallel to R910 and R922, which are also 10K 1/4watt resistors.

I need a little feedback here....
DO you really mean:

1) Just add a (one) 10k resistor across R910 to make an effective value of 5k ??? (doing the same for R922)

or

2) add 2(two) 10k resistors across R910 to make an effective value of 3.33k for R910 and 922 respectively.

Also, What advantage is this mod to the output signal? All I see here is an elevated ampitude level to U903. As my profex II has more than enough signal to drive a "CS-800", into cut-off, does this mod do anything for the tone of the output ??

The reason I ask these questions is :

Overall,I am most happy with my "Profex II",but I do have a bit of a problem with the sound being just a bit "muddled". That is,the high's arn't too good. In general it sounds too bassy. I use a EQ unit between the Profex II and the CS-800 to inprove the highs.

Will this mod inprove the overall feq responce of the Profex II or just raise the amptitude of the output signal ??

[This message was edited by Bill Crook on 30 October 2002 at 06:10 AM.]

David Decker · Post by **David Decker** » 4 Nov 2002 9:19 am

Mike Brown, Maybe you can answer the last two questions. Thanks

Mike Brown · Post by **Mike Brown** » 5 Nov 2002 6:29 am

Yes, sorry for the confusion. Add one 10K in parallel with R910 and one 10K in parallel with R922 which will increase the output level to approximately 2 to 3 volts, which is enough signal to drive any power amp.

Without trying an output mod out on the original Profex, its hard to verify if a mod on this unit will not result in undesirable side effects after completion. Therefore, a mod would have to be proven, and we haven't done this on the early Profex unit. Both are no exactly the same.

The output mod was just for raising the output level so that a tube power amp could be driven with a bit more signal. Tube power amps generally take 2 to 3 volts to drive for full power.

Mike Sweeney · Post by **Mike Sweeney** » 5 Nov 2002 9:00 am

Mike,
My question is how much more headroom[gain]does this give the unit? All I use mine for is direct recording and I run into the problem of not enough gain without cranking it almost wide open.
I also heard it makes the effects sound more crystal clear. Mike