BJF Reverb

Hej Björn (and others on the forum too)!

I had an attempt at building the Universal Reverb kit a while back, but have issues with the 8 ohm output that I'd like to sort out. I have the v 1.3 PCB running into a brand new TAD 9AB3C1B reverb tank (has the 8 ohm input). 

Most parts of the circuit seem to be working. The input and output stages seem to be passing the dry signal through just fine. C- out is driving the tank (not very optimally of course) to a degree, and this is picked up by the recovery stage. Shaking the tank also produces a very strong signal at the recovery.

It's the 8ohm/transformer- output that is not working at all. If I don't have the tank connected to the 8ohm output and TR1 is not fully clockwise, there is a fairly strong signal at the 8ohm pin. However, as soon as I connect the tank the signal goes completely silent at the 8ohm pin. I'm also not able to pick up any reverb from the tank, either using the recovery stage or with an external mixer. This is independent of the Dwell 1 setting.

One weird effect I'm getting is that that whenever TR1 is not fully clockwise, I get a little bit of treble-heavy dry signal at the reverb return. This happens whether the tank is connected or not. However, if I connect the tank to the 8ohm output (leaving the return unconnected), this trebly signal becomes louder. This trebly signal at the return also gets louder as Dwell 1 is increased.

Any ideas on where to start troubleshooting? Any voltages etc. that should be checked? I don't have a particularly deep understanding of electronics, but I but have access to a DVM and using an audio probe to trace the signal. This seems to be a really cool device and would like to hear it working properly.

I would really appreciate any ideas 🙂

Best,

Oliver

@bjf

Hi Bjorn,

Thanks for your previous instructions.  I made the modifications you recommended: R4 to 2k2, R7 to 110k, R8 to 47k, C5 to 15n, C3 to 470nF.  The one instruction I need clarification on is where to put the 1K5 resist0r between Dwell 1 and C3.  Should it go to Dwell 1 a or Dwell 1 b?  From the + of C3?

This fixed the volume drop that was happening previously, but now the reverb tank isn't getting signal from the guitar.  I can hear the reverb tank when I touch the springs, so the return is working. The guitar signal sounds normal (no volume loss), but there is no reverb on it. 

To be doubly sure, I purchased the same kit again and rebuilt it meticulously, triple checking all instructions, and scrutinising all joints along the way.  The new kit I built ended up having the same issue as the first--volume loss when Dwell 1 is turned up past 3 o'clock.  

Sorry to trouble you with all this, but it's definitely frustrating for me.   

- Firstly, can you please tell me where to correctly connect the 1k5 resistor between Dwell 1 and C3?  

- Secondly, any thoughts on why signal isn't getting to the reverb tank?

- Thirdly, with the new build, I don't understand how I could have gotten the same result of the volume loss on 2 separate builds.  Any ideas?  If that's not normal, is there a way I can moody sounds build me one that functions correctly?  I'd love to have a fully functioning pedal. 🙂

Thanks,

Mike

Hi there gents

Hej Björn (and others on the forum too)!

I had an attempt at building the Universal Reverb kit a while back, but have issues with the 8 ohm output that I'd like to sort out. I have the v 1.3 PCB running into a brand new TAD 9AB3C1B reverb tank (has the 8 ohm input). 

Most parts of the circuit seem to be working. The input and output stages seem to be passing the dry signal through just fine. C- out is driving the tank (not very optimally of course) to a degree, and this is picked up by the recovery stage. Shaking the tank also produces a very strong signal at the recovery.

It's the 8ohm/transformer- output that is not working at all. If I don't have the tank connected to the 8ohm output and TR1 is not fully clockwise, there is a fairly strong signal at the 8ohm pin. However, as soon as I connect the tank the signal goes completely silent at the 8ohm pin. I'm also not able to pick up any reverb from the tank, either using the recovery stage or with an external mixer. This is independent of the Dwell 1 setting.

One weird effect I'm getting is that that whenever TR1 is not fully clockwise, I get a little bit of treble-heavy dry signal at the reverb return. This happens whether the tank is connected or not. However, if I connect the tank to the 8ohm output (leaving the return unconnected), this trebly signal becomes louder. This trebly signal at the return also gets louder as Dwell 1 is increased.

Any ideas on where to start troubleshooting? Any voltages etc. that should be checked? I don't have a particularly deep understanding of electronics, but I but have access to a DVM and using an audio probe to trace the signal. This seems to be a really cool device and would like to hear it working properly.

I would really appreciate any ideas 🙂

Best,

Oliver

@bjf

Hey Bjorn, 

Thanks for your response.  To clarify, you said 'the 1K5 resistor goes from DW1 to terminal 2 on Dwell pot ( that is middle terminal and also the viper inside) and so this resistor replaces the wire from Dw 1 to dwell pot and then run a wire from treminal 3 ( this is the terminal that viper connects to when potentiometer is turned fully clockwise)'

Where does the wire from terminal 3 connect to?

Thanks,

Mike

Hi there

I'm working on the Universal Reverb kit and was planning on mounting it together with the reverb tank in larger rack style enclosure. I was thinking it would save a bit of space inside if I wired RCA cables directly to the pcb, and was hoping someone on here had some insight about how I'd do that (or if that's even possible). When I opened up the cables, I realized I know basically nothing about how RCA works...from what I gather the inner cable is the signal, and the surrounding wire is ground. This may be a stupid question, but could I just solder the inner cables to "c" and "return" on the pcb and gather the outer threads and solder to one of the extra ground holes?

Thanks!

@mbeach I'm interested in hearing your thoughts on these mods once you get it up and running.  I have everything built and am having similar issues; volume drop with Dwell 1 maxed, etc.

@cmchaney06 I'll keep you in the loop with the mods.  When I did the first build, I thought that volume drop was an error on my part.  I think it was part of the original design....it makes sense, as the added reverb helps balance out the volume.  I've got parts on the way to build another one though, so I'll let you know how it turns out.  

Hello, we have found a simple mod to improve the sound when the dwelll1 knob is turned to max. The resistor in the first buffer stage has too high value (10k) in the versions before v.133. When dwell 1 is turned to max, the following stages loads down the first stage too much and that is the reason for the sound quality going down. You can change the 10k at the source of T1 to a 2k2 and it will get a better. There are other modifications that can be done if you are having problems with a volume drop, but I recommend the 10k->2k2 to start with. Here is a list of mods to versions before v1.33

@busterjbrown82 Hi yes that sounds like a way to go. I would say you can skip the jacks a wire the tank directly to the board. There are extra holes for ground on the top left corner of the board the you can use for the tank ground.