Realistic (Radio Shack) Electronic Reverb

[Hedgehog]

I had one of these as a teen, and i loved the abrasive Big Black/Steve Albini sound it could give a massively distorted guitar. I was never a "keeper" of cheap old gear like this, so it's long gone, but I've been reminiscing about it and considering designing a layout to replicate it.

I would want to do it as a standard pedal (regular pots instead of faders) and probably not stereo.

What would you guys recommend for equivalent parts?

The AN6552 was a dual op amp. A TL072 or something different?
Small bear is out of stock on MN3207.
Would a 3007 replace the 3102?
The 2sc828 seems replaceable with a number of easily found current parts.

Has someone already made a layout for this that i don't know about?

Thanks!

[Mark Hammer]

The AN6552 is essentially a SIP replacement for a 4558 DIP.

The 3102 is a clock generator for the MN32xx series of delay chips (like the MN3207).  The MN3101 is the equivalent clock generator for the MN30xx series (like the MN3007).  The two clock generators perform an equivalent function, but are NOT pin-for-pin replaceable for each other.

Pretty much any medium-gain NPN transistor can substitute for the 2SC828.  Just be aware of the pinout differences between the Japanese 828 and the more common 2N.... types.

The radio Shack unit , as shown here, has an interesting arrangement.  It is common for such BBD-based circuits to have several poles of lowpass filtering ahead of the BBD to prevent aliasing, with several additional poles of lowpass filtering after the BBD to reduce clock noise and artifacts.  In this instance, there is very little lowpass filtering applied before the BBD, and 8 poles of lowpass filtering after the BBD.  The feedback/Repeat signal is tapped after 4 of them with 2 more poles of LPF applied in the feedback loop.  So, in effect, there is LESS filtering applied to the feedback signal than to the overall delay output.

The drawing doesn't show how the audio signal from the two input stages gets to IC1-B.

[ElectricDruid]

The drawing doesn't show how the audio signal from the two input stages gets to IC1-B.

Pffft, details, schmeetails..

[mozz]

If this is the model I am thinking of, i have 2 here if you need anything looked at. 1 I bought in the early 80s and found out I could plug my guitar into, other I picked up at a yard sale.

[Hedgehog]

Cool, thanks. It's just a thought for now. I have to decide if it would be fun to try to build one of these or shell out $100 on Reverb.

[anotherjim]

IC1b is also setting the DC bias of the BBD signal input, so there are more schmeetails missing.

[Axldeziak]

Here's a couple of threads with some good info about this device, including a decent schematic, some info about the missing connections at IC1-B, and some mods.

https://www.diystompboxes.com/smfforum/index.php?topic=1198.0

https://www.  the other pedal forum  /viewtopic.php?t=16073

and this page has some info about "circuit-bending" one of them.
http://www.intelligentmachinery.net/?page_id=416

[anotherjim]

Interesting protection diode. It's in series, but with the negative of the DC supply jack so avoids the diode drop when battery fed.

So, to save anyone some time, the schematic has a missing dot joining the opamps +input with the junction of R12 & R14.