Hi all, I hope I've come to the right place for this...
I'm adding a solid state reverb to my Mojotone Studio One. So far, I've added a small 36V transformer and a power supply for +/-16V for the op amp. I have a 8EB2C1B tank, compatible with the Fender Blues Junior, so I'm trying to copy the reverb section of the Fender schematic (https://www.thetubestore.com/lib/thetub ... ematic.pdf) onto a small board. I've built the circuit three times, but all I get is fuzz. I also built a reverb circuit (by Rob Robinette) (https://robrobinette.com/Compact_Reverb ... ing_Reverb), which seems to work, but is designed to drive a bigger tank with slightly lower impedances. Can someone help me lay out a circuit like Rob's (it includes a single wet/dry pot), but with the right values for the Junior tank? I hope it's a simple ask for someone who knows their stuff... thanks in advance.
I have, yes, but it's over my head, I'm afraid. I already have the layout built in DIYLC, just need some help plugging in the right values: https://imgur.com/qlwxDG2
townville wrote: ↑Fri Jan 21, 2022 2:17 am
I also built a reverb circuit (by Rob Robinette) (https://robrobinette.com/Compact_Reverb ... ing_Reverb), which seems to work, but is designed to drive a bigger tank with slightly lower impedances. Can someone help me lay out a circuit like Rob's (it includes a single wet/dry pot), but with the right values for the Junior tank? I hope it's a simple ask for someone who knows their stuff... thanks in advance.
4E is 600R 8E is 800R. to me that's essentially the same number for this application. if it works (as you said it does) let it fly. you're going up in input impedance so there should be less strain on the op amp
as a lot of cases, if it sounds good it is good
it should be noted: i am not an electrical engineer (in college i was a lot less practical and studied mathematical sciences because calculus courses were like solving fun puzzles), i am a hack who collects organ (solid state and tube) parts and attempts (generally successfully) to make guitar amps and pedals from em.
PRR wrote:
Plotting loadlines is only for the truly desperate, or terminally bored.
I failed to mention, Rob's circuit doesn't work very well in this case. It's noisy and the reverb seems weakly-driven. It lacks "punch". I'm hoping that a few resistors and caps can be swapped for better values, but I don't understand the circuit well enough to know what I'm affecting or how!
thetragichero wrote: ↑Fri Jan 21, 2022 1:36 pm
4E is 600R 8E is 800R. to me that's essentially the same number for this application. if it works (as you said it does) let it fly. you're going up in input impedance so there should be less strain on the op amp
as a lot of cases, if it sounds good it is good
it should be noted: i am not an electrical engineer (in college i was a lot less practical and studied mathematical sciences because calculus courses were like solving fun puzzles), i am a hack who collects organ (solid state and tube) parts and attempts (generally successfully) to make guitar amps and pedals from em.
I'll take a look at it tonight and think about it. The general consensus I've seen online is that a single half of a TL072 doesn't quite have the current output capability to drive a tank well and most people think it sounds week. The Rod Elliot circuit and others reccomend using a higher current output opamp (like a NE5532) and running both halfs in parallel for greater current output. I have a small PCB I did a few years copying Rod's design and I think it works really well.
Stevem wrote: ↑Fri Jan 21, 2022 10:10 pm
I would move over to one of the Accutronics Belton solid state reverb bricks .
These can be powered off of the filiment once you rectify it.
That sounds really cool. Would love to know more... any links handy? Have you done this? It sounds like a better idea. Also this might be exactly what I need: https://luigiretro.com/LRC-DR-2_digital_reverb_board
Last edited by townville on Sat Jan 22, 2022 12:08 am, edited 1 time in total.
imjonwain wrote: ↑Fri Jan 21, 2022 9:21 pm
The general consensus I've seen online is that a single half of a TL072 doesn't quite have the current output capability to drive a tank well and most people think it sounds week. The Rod Elliot circuit and others reccomend using a higher current output opamp (like a NE5532) and running both halfs in parallel for greater current output. I have a small PCB I did a few years copying Rod's design and I think it works really well.
Yeah, I'm considering this but I don't quite have the chops to engineer the circuit myself. I might be better off rectifying the filament supply and powering a Belton brick as SteveM suggested.
There's lots of guitar pedals based around Belton brick circuits and I've seen a few people use them in tube amps. It's mostly making sure you don't clip the input with too large a signal since the supply is only ~5V. You could adapt most simple belton reverb PCBs to work in an amp.
I have a spare PCB from the spring reverb board I did. It might be too big for your setup as it has a buffered effects loop and some other whistles on it though? https://tfrelectronics.com/Buffered-Eff ... op-Reverb/
