reverb + tremelo - the fun way w/ 3 tubes.

[DummyLoad]

have this on the breadboard. meet the tremmeyverby a surprisingly pleasant tube effects unit, very quiet, even on the breadboard. test driving it with that hy-gain electar redux SE amp i built a while back. the pair are cranking out some killer tone.

the tremelo sounds very, very good, but i believe that it possibly might improve with the VTL5C3 part - have some on order. but won't arrive until next week. but damn! that siliconnix VTL5C1 sounds nice in this circuit.    

thank you steve L. for contributing your trem-o-nator.   

output jack is isolated. driving a NOS 8AB1 type accutronics tank. dick dale surf and then some, y'all

schematic with telemetry attached.


--pete

[DummyLoad]

gear porn.


link to breadboard pics.

https://www.dropbox.com/sh/sdxzt9l4vyq8q1o/AAB7mx4SXrwLKW9vHMuxrr_7a?dl=0


--pete

[sluckey]

Nice project. Looking forward to hear your opinion of the VTL5C3 v. VTL5C1.

[shooter]

You're on a tear! I like gear porn, That breadboard is one of the best druel'rs I've seen !

[DummyLoad]

Nice project. Looking forward to hear your opinion of the VTL5C3 v. VTL5C1.

may i ask what manufacturer of VTL5C3 that you're using? it would be cool if i could compare apples to apples as far that aspect is concerned. i ordered a small quantity of these to test with. there are some perkin-elmer NOS for 20 bux on fleabay, but i don't want to spend 20 on a part for an experiment that's no longer made and has become increasingly difficult to source for a reasonable price.

TIA,


--pete

[sluckey]

Never had a VTL5C3. This is the VTL5C1 I have...

     https://www.tubesandmore.com/products/optocoupler-vactec-vtl5c1-vactrol-new-old-stock

Man it's only been a few years ago when I bought 10 of these on eBay for $20. Some guy was clipping them off of circuit boards. I bought them to mod my Sunn because the original incandescent lamp/opticoupler had failed and they were extinct. Workrd very well in that ss trem circuit too.

[DummyLoad]

Never had a VTL5C3. This is the VTL5C1 I have...

     https://www.tubesandmore.com/products/optocoupler-vactec-vtl5c1-vactrol-new-old-stock

Man it's only been a few years ago when I bought 10 of these on eBay for $20. Some guy was clipping them off of circuit boards. I bought them to mod my Sunn because the original incandescent lamp/opticoupler had failed and they were extinct. Workrd very well in that ss trem circuit too.

those are the exact parts i ordered - only mine were from CE Distribution - same Co. Are yours impression labeled "SILONEX" on the bottom? when i bought the ones i have now in march 2019, they were $6.95 ea. Qty. 10 plus. price has jumped to 9.95 ea. with no qty. discount. gotta love that supply and demand.

--pete

[shooter]

fwiw;
bought mine same place Steve did, even spung for a pricey NOS.  The NOS died open on the R side.

the 2 regular ones were further apart in ohms than I expected, used the higher ohm one, works well

[Latole]

Great project, congrat,

I build my own opto-coupler for $2 with heat shrink tubing.  I fix fews amps with those.

That is what I bought at my electronic store. Many Photo- resistor value may work.

When finish with heat shrink tubing, it look like a real original Fender.

[sluckey]

Are yours impression labeled "SILONEX" on the bottom?

I don't think so. Can't find my spares. I know I put them in a logical place.   
But the top of mine look exactly like the ones in the link I posted.

[sluckey]

Great project, congrat,

I build my own opto-coupler for $2 with heat shrink tubing.  I fix fews amps with those.

That is what I bought at my electronic store. Many Photo- resistor value may work.

When finish with heat shrink tubing, it look like a real original Fender.

Your optocoupler is quite different from a VTL5C1 and will not work in the circuit being discussed.

[DummyLoad]

Great project, congrat,

I build my own opto-coupler for $2 with heat shrink tubing.  I fix fews amps with those.

That is what I bought at my electronic store. Many Photo- resistor value may work.

When finish with heat shrink tubing, it look like a real original Fender.

the vactrol are using LED lamps to modulate the LDR. yours is using a neon lamp. big difference.


--pete

[PRR]

But knowing his Neon from his LED, his same shop can surely sell a 25 cent LED.

[Latole]

DummyLoad you are absolutely right and PRR is indeed achievable.
I took advantage of the subject (rare about a reverb) to address how I build a photcell

[DummyLoad]

DummyLoad you are absolutely right and PRR is indeed achievable.
I took advantage of the subject (rare about a reverb) to address how I build a photcell

i have done the same for a crestline series epiphone futura RVT that had a dead trem optocoupler. i cannot seem to source a photocell with a high enough resistance with a dynamic range and response time to be useable for this amp's application. gave up and bought a fliptops optocoupler for an ampeg - it works, not as good as it should, but well enough for me to flip the damn thing. the fender optocoupler did not work at all.   


--pete

[DummyLoad]

some more extensive use revealed a flaw in this plan.


if the mix control is set fully CCW for all dry signal, the output impedance of the cathode driver would load the trem oscillator to the point of not working. OK so now, you ask yourself, why would anyone plug into a reverb effect and want to turn the effect all the way off? wouldn't you just use the footswitch or a front panel switch? 

i patched it with a part change and part add. it's still not "perfect" but it is very useable. i added a 56K R from the cathode of the dry signal driver to the mix pot. i changed the plate load resistor of the trem oscillator from 470K to 270K - that upped the vactrol drive to where it's almost annoying in strength at full intensity, so turn it down if you don't like crimson and clover trem. the minor flaw: with the mix control fully CCW for dry only signal, there is still a hint of reverb signal leaking through. if that doesn't suit you, then use the damn footswitch! :p

this effect IS all about the reverb, so if the trem is not what's desired or, deemed undesirable as-is, the unused triode could be used as a plate follower for lo-Z output driving a plate to 600/150Ω transformer. 

revised schema attached. 


--pete

[shooter]

the output impedance of the cathode driver would load the trem oscillator to the point of not working.

thought about the "loading" factor last night as I was drifting off 

[DummyLoad]

received the VTL5C3 order today and tested one of the parts. i have mixed feelings on the results. the VTL5C3 have a faster response time so the trem slope becomes choppy very quickly when the oscillators signal intensity is increased. need to experiment more to tame it.

for now the VTL5C1 is the go-to, so in the meantime, i'm going to update the schematic to reflect use of the VTL5C1.



--pete

[DummyLoad]

ok, so some saddle time on the breadboard. about 20 minutes and a couple of part changes later, we have a winner. the VTL5C3 to me is more appealing tonally. i swapped the cathode R from 10K to 4.7K and that tamed the VTL5C3 in this circuit.

updated schema rev. level > 2.1 and updated telemetry to reflect changes. updated notes in schema to state use guide for either vactrol type.


--pete

EDIT: fixed anode R value - overlooked update from previous revision. 

EDIT: &^%$*! the intensity pot is 100KL NOT 250K - my apologies. i sat down to drive it few minutes ago and stared at the pot for a few seconds, then the lights came on! aw man! the damn schema is wrong. again!

[kagliostro]

Ciao Pete

There is way to avoid the use of the 3MRA pot in favor of an easier one to be find ?

Thanks

Franco

[sluckey]

The reverse audio taper spreads the speed change per degree of knob rotation more evenly, but any 3M to 5M pot will work.

[PRR]

Use a forward audio-taper and turn it backward. The electrons don't know the difference. When the user gets annoyed, order a box of 3M RA pots. Most tube trems use something like that.

[kagliostro]

Thanks Steve & PRR

....order a box of 3M RA pots...

That seems a good council 👍

Thanks

Franco

[DummyLoad]

quarantine + boredom productivity. uses belton PCB sockets and chinese ceramic PCB octal.

the rest of the connectors are molex .156 ctr. may suffer from molexia eventually, possibly, definitely maybe.   



--pete

[DummyLoad]

some more tinkering. it was bugging me that the last plan had to leak some wet signal for the term to work as good i wanted, so i came up the attached. it works with better overall for trem effect with mix control either full dry or mostly wet - can't use full wet without nasty echo artfacts (like the original 6G15) but that's the just way things work.

the useable range to on the wiper sweep to engage the trem effect was improved by using a reverse audio pot. bootstrap sees a 250KΩ resistor in place of the 1MΩ. works very well with all dry signal dialed in with the mix control.

on a footnote, i did some more experimentation with some different tank types that i have in inventory and i came to the following conclusions: a) i prefer the long 2 spring 4 series tanks overall, b) the 8 series 3 spring are only available with long decay in the AB impedance and sound kind of tinny in the upper registers. a while back i got lucky and found a source for NOS USA made accutronics 4 series AB type and i bought a small lot of them. so i had the opportunity to compare a vintage and current production parts. IMO, the NOS accutronics seem to sound better on the lower register, otherwise, the belton/accutronics 4 series are equal in all other aspects.

steve, going to try the VTL5C1 again to compare with this reconfiguration.

--pete