Tonepad's MXR Envelope Filter report/question.

[jrc4558]

Hi everybody!
First of all - happy new year and all the best in 2005.
Second: I built MXR envelope filter from Tonepad on this layout:
http://www.tonepad.com/getFile.asp?id=5
I built it without any mods to it, just stock. However, I didn't have a 3k resistor for R1 / Vss, and used a 3.3k (i decided to go up on the value cuz i was concerned about possibility of frying the chips with higher voltage).
The cirquit works, but is sufficiently quieter than the bypassed signal. It's at approx. 3/4 volume from the strait guitar volume. Is this because I used a higher value R1?

Thanx.

[Paul Perry (Frostwave)]

Maybe, but I doubt I could hear the difference. You won't damage anything making it smaller.

[Mark Hammer]

I'm confused here.  The pdf file at Tonepad indicates R1 as being one of the output resistors, and as being 3k6.  If anything, replacing *that* R1 with a 3k3 unit would tend to increase output by reducing the attenuation that the R1/R2 network normally provides.

Your mention of Vss suggests to me that you mean R4, particularly since that one IS listed as being 3k.  That resistor simply limits supply current to the chips.  I don't know enough about CMOS chips to say, but I can't see that a *nominal* 10% difference in value between components that are normally 5% tolerance anyways would have that dramatic an impact, particularly since any 5% 3k resistor and 3k3 resistor plucked from their respective bins could be very similar in actual value.

The builder comments at Tonepad (ALWAYS a useful read.  Some folks who you never hear from on this site can have some truly insightful comments to make.) suggest that the R1/R2 network is where you want to strike to tackle the level-balance issue.  Bear in mind that the *apparent* level is a function of the bandwidth as well as any full-spectrum attenuation.  The ratio of R1 and R2 adjust full spectrum attenuation.  Making R1 smaller or R2 larger will increase output signal available at the jack.  C4 is intended to eliminate any audible HF clock noise and accumulated hiss from the output, however its' rolloff point will be set by the interaction of R1 and C4.  It is currently set to roll off starting around 442hz (lordy mama, that's low).  Dropping its value to .047 should let a little more midrange through and make the filter sound *seem* a bit louder.

[zeta55]

I did my build with some changes I picked up from the build reports from tonepad(as Mark mentioned). I was able to get the output level on the spot, also som changes with the output caps were made plus the reverse mod, thats a great one. Sorry I don't remember the exact changes as it was a year ago since i built it.

[jrc4558]

Thax a lot guys.
Now that I look at it, could i increase the gain by increasing r13? looks like it wouldn't affect the envelope extractor. Or am I wrong?
Have a happy new year, all of you!
Cheers.