cool reverb apart from switch spdt 'pop' issue

[samhay]

If you are using a TL074 in the reverb then the max input impedance is ~690k (1M || 2.2M), so this should be OK. You could increase the pulldown resistor to e.g. 10M, which will bump it up to 900k.
I might be barking up the wrong tree, but looking at the distortion schematic, the first thing I noticed was that the volume pot seems quite small considering it has quite a lot of passive tone shaping behind it. Can you try a 100k+ pot here and see if that helps.

[deadastronaut]

hi sam , ive just tried my ax1500g pedalboard into it and its the same massive vol drop too...when turning on reverb....hmmmmm...


edit:  i'll record a loop on my pedalboard and pump it in there, whilst adjusting the input R/C ....


edit:.. ok, i swapped the 33k, 4.7n for 220r/1nf...much better with distortion.....still a little tweaking to do though...but much better level/tone unity now...not perfect, but better...

[samhay]

I should have suggested that as the easy option, but I guess you worked out you had a 10k/33k ish voltage divider problem.
You will probably get more output from your distortion with a bigger vol pot, but that is probably a discussion for a different thread. Is the reverb now good to build.?

[deadastronaut]

hi sam, cheers man,

i would say almost ready....i'll have it nailed tonight/tomorrow hopefully...i think.

sounds right with my pedalboard....i'll re-try it with seperates..

re the distortion pot: i only need it on 9 oclock to be unity...may have to revisit/mod that. cheers..rob.

[samhay]

re the distortion pot: i only need it on 9 oclock to be unity...may have to revisit/mod that. cheers..rob.

Fair enough - sounds like it is doing the trick.

Whereabouts did you get the Belton brick from? I have seen that das musikding have them, but am wondering if there is a UK source.

[deadastronaut]

hi sam: yep i got mine from musikding too.


seems lke you may be right on that pot lark...

the pedalboard was fine...korg ax1500g

then i tried my dr boogie and that was fine too...so the spitfire seems to be the culprit. i'll swap that 10k pot out and try it...

i also took out the reverb input R/C too...report back tomorrow.

[deadastronaut]

update:

in the cold light of day..and further tinkering.....there is still a problem with this.

it seems near impossible to get it to be happy with  clean+distorted without a massive change in vol and tone....

when i leave out the input RC its pretty much bang on with distortion (dr boogie) ...fine.  = ...only a slight tonal change....

but then when distortion is off , there is a massive difference between reverb on /bypass....which then needs input R/C to be more like e.g. 33k/4.7n...

this is all tested with reverb level minimum/off .....short of having a switching input R/C for dist/clean, which would be a nightmare...i'm at a loss.

i'd like to hear from anyone thats built these reverbs , and what their findings are with other pedals in front.....comparing tone/level etc....

@#$%ing reverb ..

[R O Tiree]

There's a lot of passive tone/vol control circuitry at the end of that Spitfire circuit, which might mean that its output impedance is higher than we're used to in these circuits.  Try putting a buffered pedal in between them (any Boss pedal would do, as they're always buffered whether the effect is on or off) and see what happens. If it works, just make a little buffer to go on the end of the Spitfire.

[deadastronaut]

hi mike, its the same if i use my dr boogie too though...

i'll whack my old boss ce2 in between and see what happens...cheers.

[slacker]

Hope this doesn't sound like I'm taking the piss, but are you sure what you have on the breadboard matches your schematic?
With the reverb turned all the way down and output on full, the output should be at least as loud as bypass, there's nothing in the dry path that can cause a volume drop.

[deadastronaut]

@ian: stop taking the piss   schemo/bread the same man...

@mike:  voila', i put the dr boogie> boss ce2> reverb ....(no r/c on input...

much better now  on distortion and clean....yay!!!!...

tried spitfire > boss ce2> reverb....voila' again...(no r/c on input..

so its definately a buffer issue.

sooooo......can i just add a buffer to the reverb, rather than butchering the dr boogie+spitfire...make sense?

the reverb will be at the end of my chain anyway...

[slacker]

If you ditch the 33k/4n7 does the volume loss problem go away? Without them the first stage is a buffer so if you still get weirdness, I'd start thinking it might be a bad opamp, or a dodgy or wrong value cap or resistor.

[samhay]

I'm with Slacker - you have a perfectly good input buffer with a low-pass filter in front of it. What happened when you tried the 220R/1nF RC filter?
Are you using a TL074 like the schematic says? If so, I always get the pinout confused on those bad boys. Any chance I am not alone (and/or the IC is toast)?.

[deadastronaut]

 ok..heres a clip of whats going on.   i ve checked over the breadboard, swapped 074 for new one...same thing.

spitfire>reverb.

1st clip clean,.... 2nd clip reverb on,..... 3rd clip dist on, reverb off, .......4th clip dist on,  reverb on....

no r/c on input....just a 33k on the out to keep level unity-ish for now...

note the tone difference on clean bypass compared to reverb on......then massive vol loss when reverb with distortion...

https://dl.dropbox.com/u/7464107/bastard%20reverb.mp3


edit:  heres a clip with a boss ce2 too..

spitfire>boss>reverb

1st clip clean,.... 2nd clip reverb on,..... 3rd clip dist on, reverb off, .......4th clip dist on,  reverb on....

https://dl.dropbox.com/u/7464107/bastardreverb2buffer.mp3

so something is amiss...as it behaves nicely with the boss(buffer)..hmmm...


now here is a clip of the spitfire>reverb  with no 33k on end for unity...just straight out from the 1uf.

1st clip clean,.... 2nd clip reverb on,..... 3rd clip dist on, reverb off, .......4th clip dist on,  reverb on....

https://dl.dropbox.com/u/7464107/bastrev3.mp3

see my dilemma?

[slacker]

What are you plugging into for those clips? The difference in tone on the cleans in the first clip could be whatever you're plugging into tonesucking your guitar and the reverb then buffers it adding brightness. Also worth noting the bright switch will affect the dry sound as well as the wet so that would add treble if it's switched on.

That doesn't explain the volume drop with dirt though.

If you stick the boss after the reverb does that cure the problem?

[samhay]

I got more confused and started looking at your verb schematic for any other/obvious problems. I had 2 thoughts; take them with a pinch of salt.

1. I am lost as to whether the RC filter is causing your volume drop/tone problems or not, but why not move it after the input buffer. You already have 10k resistors to the wet and dry sides of the circuit. You could then use 15n caps to Vb to get you a similar roll-off. I would use a smaller cap for the dry signal though so it is a bit more unadulterated (1kHz seems a bit low).

2. Ditch R11. As it stands you have a 33k bias resistor to a low impedance ground (Vb) and another 10k/33k voltage divider problem, which means you will not get unity volume out of your dry signal. I don't see any reason for the bias resistor as IC1b and IC2d are DC-coupled (no cap between them). If you find you need the bias resistor, increase it to >>10k (i.e. 1M).

[deadastronaut]

@ian:  i'm just using my usual setup that i use everyday..  guitar, ibanez rg470>spitfire>breadboard with reverb on it(true bypass breadboard btw) > mixer>amp.

bright switch is off...

just tried the boss pedal AFTER the dist/reverb...perfect!!! unity level, unity tone too..much much better......(btw , thats with no volume control on reverb at all, just straight out of the 1uf..)

so i  need a buffer on the end of the verb yeah!!!!..can you recommend a suitable buffer?.

@sam: i'll try a buffer , and if that don't quite work out i'll give that a go man..

cheers guys...getting there.

[samhay]

Sounds like you are making progress. Without the volume pot (which is probably not necessary for a unity gain pedal), you already have a pretty good output buffer in terms of low output impedance. Did you always have the vol pot missing?

[deadastronaut]

hi sam, no, but i had the volume set to unity, and there was still enough left for a boost too..

which i quite liked for volume swell type stuff etc...and was handy to just make up the level when the reverb was on max..

i pulled it out for the above final clips though...

i'll have a poke around and see if i can find a 'close' to boss buffer and try it out...


edit:

i tried the first fet buffer on the reverb out  here, which was perfect with distortion/reverb on/off , but still had the massive difference in levels issue on clean...hmmm...
http://www.muzique.com/lab/buffers.htm

[R O Tiree]

Put the FET buffer in front, Rob