Analog Delays Clipping Overload Repeats w/ Preamp Boost Pedals

[rrm152]

Greetings, first time posting, sorry if I'm not doing this correctly.

I have built three Madbean Analog Delays (The Aquababy, Aquaboy dlx, and the Man O'War). They all sound great except I have the same problem with all of them. If I have a boost, preamp, compressor, or certain drive pedals in front of any of them I get what I'd call a loud bump/thump/overload/clipping in the first couple repeats...

I own a couple commercial analog delays (Boss Waza, and Ibanez mini) and they don't seem to behave this way. 

Is there an adjustment I can make to these pedals to resolve this? thanks very much -R

[thomasha]

That is interesting.

A video or audio would definitely help, to give a better idea of what is going on.
To better answer your question more information is needed, because there are several variables that can make a BBD based circuit sound bad. Did you use the exact parts in the build doc.?

Which BBD chips did you use vs. which chip the waza uses?
MN3005 and V3205 have different requirements.

Did you use the NE570 or the NE571? I never can find the NE570 where I live, and always used the 571, although the datasheet says it is worse (?) aspect wise.

Did you power it with 9V or 18V? How are the chips biased?
Biasing can make your BBDs sound better.

I hope someone with more experience than me shines on, and maybe already has the answer.
I would definitely investigate things closer to find an answer.

[Bio77]

Someone more experience than you, thomasha?    Your builds make my brain hurt.

My vote is for biasing.  Did you use a scope? If you don't have a scope, I would recommend re-biasing by ear, but run your boost in front (I've never tried this, though).

[jimilee]

All of the listed pedals are buffered? I don't know if that matters.


Sent from my iPhone using Tapatalk

[rrm152]

thanks for replies! Okay so on the man o' war, I used the mn3005, mn3101, v571d, and jrc4558. I used an audio probe to calibrate and followed the instructions. The delays all sound great except when i run certain pedals in front (FA-1 clone, byoc 5 knob compressor, and Nocturne Brain Dyna Brain). Now this morning I tried A buffer before everything and also a buffered Klon Klone which completely eliminated the issue. Should I rebias with one of the preamp pedals infront or just use a buffer before the Delay? No room in the box to add a buffer in the pedal itself. I should also note when the buffer was between the two it still misbehaved. Only when it came first did it solve the issue.

Attached is a pic of my build of the Man O' War

[rrm152]

I'm running Man O'War at 12V per the instructions.

[madbean]

thanks for replies! Okay so on the man o' war, I used the mn3005, mn3101, v571d, and jrc4558. I used an audio probe to calibrate and followed the instructions. The delays all sound great except when i run certain pedals in front (FA-1 clone, byoc 5 knob compressor, and Nocturne Brain Dyna Brain). Now this morning I tried A buffer before everything and also a buffered Klon Klone which completely eliminated the issue. Should I rebias with one of the preamp pedals infront or just use a buffer before the Delay? No room in the box to add a buffer in the pedal itself. I should also note when the buffer was between the two it still misbehaved. Only when it came first did it solve the issue.

Attached is a pic of my build of the Man O' War

Not too sure why the buffer in front fixed the problem (considering the MoW and Aquaboys all have buffers right at the circuit input). Most active effects you put in front of the delay will already have a very low output impedance just as a buffer would.

In my experience, most issues of thumpiness or low end distortion start at the compressor portion of the compander. The 570/571 have very slow response times to high amplitude and low frequencies signals. Here's a bit from the datasheet:

The speed with which gain changes to follow changes in input signal levels is determined by the rectifier filter capacitor. A small capacitor will yield rapid response but will not fully filter low frequency signals. Any ripple on the gain control signal will modulate the signal passing through the variable gain cell. In an expander or compressor application, this would lead to third harmonic distortion, so there is a trade−off to be made between fast attack and decay times and distortion.

IOW, it's a balancing act of values for the RECT and THD Trim caps - pins 1 and 8. The AD-900 uses the same value as a DM-2 which are 220n and 100pF resp. You could try changing the value on the 220n cap to 330n give you better performance on the low frequency distortion. A different approach would be to try some signal limiting to the input (pin6). Like a 100k resistor b/w C10 and pin6.

[rrm152]

Thanks very much Brian, the buffered pedal (klon) didn't actually eliminate the issue i was wrong there. I went back in and rebiased first just to be sure (also did it with the "problem" preamp pedals in front). That didn't change anything. I then socketed the compander cap and tried several values...330n and 470n made it worse...as I went lower it improved so I ended up at a 82n which totally removed the issue...100n was close; the thumping was still there slightly. It sounds great now. I'll have to apply the same mod to my aquaboy dlx and dual-aquababy (put two in one box). Oh I also built the Current Lover recently and it sounds amazing! Getting geared up for the Total Recall soon. Thanks for your brilliant work!

[rrm152]

Need help identifying the corresponding 220N cap on the Aquaboy and Aquababy boards. I appreciate it!

[Zerro]

Maybe you need to consider the power supply, if it is sufficient about the current consumption of these vehements you built. There are then some questions about biasing too, as mentioned someone before. Especially if they are in row, more pedals.