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BJF Reverb

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moody
(@mastermoderator)
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Blev medlem: 3 år sedan
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We are about to finish the BJF Universal Reverb kit. A circuit to which you are able to connect any (almost) reverb tank unit to. So it is an analog reverb with two outputs and controls for dwell, mix and tone. The pcb can go in a 1590bb box but the external reverb is of course bigger. Enough to make a pedal board on its own:)  I hope we have the kit up by end of Feb. Questions about the pedal, welcome here!


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Scott
(@scott)
Medlem Admin
Blev medlem: 2 år sedan
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Hi Bjorn. Hope you are well. I wanted to ask you about this reverb. I have a BYOC Tweed Royal amp that I built. Live the amp but there is no reverb. Could use this reverb kit to add the reverb between the pre amp and the power stage?

Thanks,

Scott


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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 17
 

Hi Scott,

 

You can certainly add the reverb circuit to an amplifier. In fact I have three solid state amps that could do with an upgrade and that I am planning to install this circuit in.

Make sure that decoupling capacitors on powersupply are rated high enough so if you have 15V supply mount 25V decoupling capacitors

You can also increase the series resistans in the B-tree to drop Voltage to something suitable or mount a 78XX regulator from amplifier internal supply to

reverb ad on.

 

Have fun

BJ


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SenseDoor
(@sensedoor)
New Member
Blev medlem: 2 år sedan
Inlägg: 3
 

Hello Björn. I ordered the "Analog Reverb kit (incl. tank)" from Reverb.com and will be installing it in an amp case I'm building. I have a limited knowledge of electronics, but from the drawing in the manual it looks like the aluminum enclosure connects the grounds of the components. If I'm not putting it in the enclosure or using the jacks, do I connect the grounds from the pots and IN/OUT connections together? Is there anything else I should be concerned about if I build it without the enclosure and jacks? Thanks very much. Thanks for being multi-lingual also, as I don't know a word of Swedish (my loss)! 


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SenseDoor
(@sensedoor)
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Blev medlem: 2 år sedan
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I never got a response to this, so I had to build it as I saw fit. For the benefit of those with the same question, I had success building this in a wooden amp case, and connected the ground between all of the components. I put a switch on the 9v power instead of activating the power through the stereo jack.


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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 17
 

@sensedoor

 

Hi there,

 

 

Ok sorry about that due to technical problems and myself travelling reply has been slow

 

Yes chassis make ground. You will need to wire ground terminals of in-and outputjacks together and connect that with pcb ground and make sure all ground points go together.

 

Ground in this case is a floating potential  ( that will be connected to earth somewhere down the line)but also carries the reference fior the signal and circuit will not work without grounds wired together.

 

You can absolutely useca wooden box as long as you connect all grounds

At your service

BJ

Bjorn Juhl

 


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SenseDoor
(@sensedoor)
New Member
Blev medlem: 2 år sedan
Inlägg: 3
 

@bjf

 

Thanks, Bjorn. I got it assembled no problem. I put it in a completely battery powered full range speaker built from Parts Express items and it sounds great. I appreciate your response.

 

Mike

 


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bakelitetele
(@bakelitetele)
New Member
Blev medlem: 7 månader sedan
Inlägg: 3
 

I love the idea behind a universal reverb circuit. Do you think it is possible to add a tone control to the recovery circuit without modifying the pbc?


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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 17
 

Hi there

 

Oh tone control for reverb is definitely possible by just adding desired filter outboard inserted at Reverb level control.

 

I'll have a talk with Albin about making a tone control modification kit and getting schematics up for those that have parts lying about.

 

Worth mentioning is that the reverb effect from a typical tank has a fairly narrow bandwidth and low frequency reflections have tendency of causing mud whereas high frequency reflections a tendency of causing shimmer: therefore most effective would a treble control be and also limiting low frequency response to make effect appear more as shimmer

A difference between tanks is also how high up in frequency they go so it can be useful to have control for brightness.

Slight caution is again that tanks have limited bandwidth so boosting treble a lot after recovery can be just amplifying noise therefore

making a sort of bandpass boost can allow boosting the relatively important part of response i.e. highlighting where there is energy but not heating for the crows.

 

At your service

BJ

Bjorn Juhl


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bakelitetele
(@bakelitetele)
New Member
Blev medlem: 7 månader sedan
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Thank you Bjorn. Your response has given some good ideas to think about!


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Atomanth
(@atomanth)
Active Member
Blev medlem: 5 månader sedan
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Hi. I’m having trouble with my universal reverb. I’m not sure where I’m going wrong here. Using a scope, I can see that I have signal all the through the transformer out, into the recovery side, but then the signal just disappears after T6. I’ve checked all solder connections for bridging and everything looks fine. I even went so far as to rebuild the unit in a wooden enclosure so I could connect isolate and connect grounds manually to see if grounding was an issue. Power seems fine throughout, it’s just the signal that disappears. I noticed that my PCB is different from all the pictures I’ve seen, specifically there is no trace connection between R18 and R22? It seems like the tail end of R18 is connected to nothing at all? Any help would be much appreciated! My board version is 1.12. 


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renascent27
(@renascent27)
New Member
Blev medlem: 5 månader sedan
Inlägg: 2
 

@atomanth

I recently encountered this problem as well. My board is V1.12 and a portion of the signal trace is missing as you described. The solution is to solder a jumper wire between the R18 & R22 resistors, where the missing trace would have been. Without the R18 to R22 connection there is no voltage present at either the emitter or base of T6.


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Atomanth
(@atomanth)
Active Member
Blev medlem: 5 månader sedan
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@renascent27

 thanks for the help. I assumed that might be the case, but I was nervous that I might blow something up! I’ll give it a try today and let you know how it works out. 


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Atomanth
(@atomanth)
Active Member
Blev medlem: 5 månader sedan
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I jumpered the connection from r18 and r22. I now have output, insofar as I can slap the tank and hear it through the amp. If I crank the amp and the mix knob, I can hear the guitar signal faintly exciting the reverb, but in that case I have a really distorted guitar signal. It’s not really usable. I’m also getting almost 2 volts of DC on P1 potentiometer. What a mess. Not sure if that was an issue from the beginning or I messed something up disassembling and reassembling a few times trying to solve this problem. @bjf any suggestions?

This post was modified 5 månader sedan by Atomanth

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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 17
 

Hi There

 
 
Firstly 2V on Dwell pot is normal because one end of it connected to T1 source which should have about 2V resting voltage. The following stages are all AC coupled via C3,C5,C14
 
To fault find start at output and check T8. If you have a DVM can you please measure voltages at terminals of T8?
If you have a scope and signal generator you should be able to follow signal to point it disappears.
 
If you look at the schematic you’ll see T6 takes bias from T7 via voltage divider R18,R19 and R22 so yes a line missing here would lock the recovery amplifier
 
At your service
BJ

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