Author Topic: DBA Reverberation machine/PCB guitar mania Death By Reverb  (Read 305 times)

DBA Reverberation machine/PCB guitar mania Death By Reverb
« on: June 19, 2022, 03:15:53 PM »
So i built this thing and it just isnt near as exciting as the demo videos. is it possible the board isnt well done? or the videos are misleading? what a good opportunity to mod it and make it my own. Here are my questions and steps taken so far.

The variables:
The schematic calls for a TLC27M4AIN but i used the suggested TL074 because i was easier to get. Can that make a big difference? i read that the tl074 would be noisier but that doesnt bother me. thats what DBA is all about. In place of the lm7805 i used a 78L05. i thought it was the same thing but i could be very wrong.

Change made so far:
The suggested mod on the schematic wasnt very different sounding so i placed a 3.9M resistor in r20. and left c14 empty. this adds a lot of dirt to the sound and maybe lets the verb run a little wilder. Loving this.

The problem:
Both the light and dark modes on the toggle have TOO MUCH BASS. Can someone explain how to but bass and boost highs on the tone stack? I think its to the two paths chosen by the toggle.

Possibilities:
My other idea i havent tried yet is to tie the unused leg of the belton brick somewhere into the signal to add more verb/create feedback. i dont know what happens if i do that yet but ill soon learn. this is my first build with a belton.

THanks

 https://pcbguitarmania.com/wp-content/uploads/2019/08/Death-by-Reverb-2.1v-Building-Docs-1.pdf







Ripthorn

Re: DBA Reverberation machine/PCB guitar mania Death By Reverb
« Reply #1 on: June 19, 2022, 05:16:41 PM »
One thing to check is the voltages for the Belton. Depending on how voltages are distributed, a 78l05 might be on the edge of being able to source enough current. It's rated for 100ma and each pt2399 takes anywhere from 25-30, plus the Belton has a separate Schmitt trigger inside that needs some amount of current. Depending on conditions, things might be a little weird.
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ElectricDruid

Re: DBA Reverberation machine/PCB guitar mania Death By Reverb
« Reply #2 on: June 19, 2022, 06:59:50 PM »
+1 what Ripthorn said. 78L05 is a bit borderline for this job. They chose the 7805 because it can handle more current without any problems. The Belton Brick datasheet reckons drawing 60mA current is typical, but gives 100mA as the potential maximum. So using a 100mA regulator might mostly work, but doesn't leave you much margin for error. Does it get hot?

Re: DBA Reverberation machine/PCB guitar mania Death By Reverb
« Reply #3 on: June 19, 2022, 11:05:52 PM »
Thanks for the input. New voltage regulators will arrive Wednesdays and then we will see what happens.

anotherjim

Re: DBA Reverberation machine/PCB guitar mania Death By Reverb
« Reply #4 on: June 20, 2022, 05:51:24 AM »
+1 the regulator choice.

The intended schematic opamp TLC27 type is a different beast.

For one thing, you should not connect an input pin of a TL07x to 0v (the chip negative supply) as the design does for the unused opamp pin 5. This is ok for a TLC series opamp because these are CMOS based opamps while it's forbidden in the specifications of the JFET input TL series. However, the only penalty is likely to be a bit more supply current wasted. If they had tied pin5 to 5v it would be within spec for any type of opamp.

The CMOS TLC opamps do tend to clip more smoothly and musically when driven to distortion although they will produce more hiss noise than a TL series. This is probably the reason for choosing the rarer TLC27 although any TLC series quad opamp would probably be good for it. I'm aware that DBA go for trashy sound, but there are interesting or unlistenable varieties of trashy

As to tonal balance, the clean signal gets treble emphasis from R16//C13 (staring over 300Hz) while the reverb output does not. Then if the output booster gain is high, C14 cuts more highs (down near 300Hz at max gain) and you would expect it to dull the reverb. Changing C14 and C10 to smaller values and even shorting out R16/C13 altogether might get the sound to your taste.
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Re: DBA Reverberation machine/PCB guitar mania Death By Reverb
« Reply #5 on: June 27, 2022, 08:38:12 PM »


As to tonal balance, the clean signal gets treble emphasis from R16//C13 (staring over 300Hz) while the reverb output does not. Then if the output booster gain is high, C14 cuts more highs (down near 300Hz at max gain) and you would expect it to dull the reverb. Changing C14 and C10 to smaller values and even shorting out R16/C13 altogether might get the sound to your taste.

thanks. changing c10 to 4.7n was the key. i settled on 1.8m for r20.