DirtBag v3205 distortion

[madbean]

See this thread first for newer modifications: http://www.madbeanpedals.com/forum/index.php?topic=3366.0

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Here is the solution (copied from the updated project doc) to eliminate the distortion issue with the v3205 version of the DirtBag. As promised, it's a super-easy fix!

REVISION (CRITICAL): Some builders of the v3205 version of this project have run into distorted repeats. There is a simple solution to this issue. Replace R21 (1k) with 100k and C14 (33n) with another 100k resistor. This forms a voltage divider which eliminates overloading the lower headroom of the v3205. The original 1k/33n forms a low pass filter with a corner frequency of about 4825 kHz. Even though this fix eliminates this filter, it seems that the low overhead of the v3205 does not impact the delay tone in a significant way. Further tests also found that R10 could be omitted from the compressor portion of the NE570, but this is not critical. As a reminder, you will want to use 47k for both R11&R12 when building the v3205 version.

The project document has been updated with the revision: http://www.madbeanpedals.com/projects/Dirtbag/DirtBagDeluxe.zip

I'm really sorry for those who felt frustrated over the past few days. But, I hope that frustration will quickly go away once you hear how much better your new delay is going to sound

[Mich P]

I think you mean C14 for the 33nF.

[madbean]

I think you mean C14 for the 33nF.

Thx.

[LaceSensor]

Thanks for the fix
Im in Denmark but will try this wednesday night
 Im a bit sad as I know that I tried in vain to remove c14 already.
Hopefully I wont mash my board getting it out.

[RonaldB]

THanks Madbean,
I will change this on my board and check my delay tonight.

RonaldB

[LaceSensor]

Didnt completely solve things for me.

[Scruffie]

Bean, did you see in the 'Dirtbag Troubles' thread the stuff I mentioned about the Compander voltages? It's set too hot at the moment, R11 & 12 should both be 24k, not 47k and we also need to change the other output, looking at some DMM voltages, while it should be about 1/2 supply, it's under that so i'd suggest rather than the 'correct' value of 24k for R42 we use a 33-47k there.

Then rather loosing a low pass filter, it may be preferable to change both R13 & 14 to 33k to reduce clipping, give that a whirl and see if it improves stuff.

[madbean]

Scruff,

Thanks, I've actually been tweaking with those values. I'll try the 33ks, too. It's getting closer....I have a few final ideas to try out today. I'm also comparing voltages to the AquaPuss on the compander, and just generally audio probing both circuits.

Interestingly, I was reading a little review by Culturejam yesterday complaining about the repeats on his EHX Memory Boy yesterday. Those use four 3208s. They are so cheap I might pick one up just as a reference point to improve the DirtBag.

[Scruffie]

Scruff,

Thanks, I've actually been tweaking with those values. I'll try the 33ks, too. It's getting closer....I have a few final ideas to try out today. I'm also comparing voltages to the AquaPuss on the compander, and just generally audio probing both circuits.

Interestingly, I was reading a little review by Culturejam yesterday complaining about the repeats on his EHX Memory Boy yesterday. Those use four 3208s. They are so cheap I might pick one up just as a reference point to improve the DirtBag.

I've got a Memory Toy, I think the repeats are fine! Then again I think culturejams admitted now he just doesn't like BBD Delay. Anyway, could be a good idea to grab one.

22/24k for R11 & 12 is fine, relatively, pin 7 is biased to around 7V on a normal Memory man (from the voltages I saw) so that's half the 15V supply, 22 or 24k in R11 & 12 got Lace Sensor 4.5Vish when I suggested he try it.

But on the other output of the Compander, on the Memory Man voltages I saw it was a lot lower than half supply (where it would normally be) so 33k should lower it down below half supply, as once again Lace Sensor got 4.5Vish when I told him to use 24k for R42.