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HI ,so I've now got to the stage where I need to get my head round the reverb fit to my TC 15.

reading all the posts between Tubefiend and Kurtlives still have some questions


As I have VRM fitted I will need to take B+ from the standby switch so as to not scale the Reverb with the rest of the amp ?
This will need filtering , 22uf Cap same as other filter caps?

R10 and R7 will be fed from this secondary B+ supply and need to be sized to get the right voltage at the anodes/plates of the reverb tube. Any guide on where to start with those would be great,
Tubefiends voltages of 240 at plate of driver triode and 130 at plate of recovery triode are OK? What should the voltage be after R10 on the HT side of the reverb transformer?

Circuit diag. shows C4 as 500pf, posts refer to 680pf , which is right/better or what to pick for what reason?

Circuit diag. shows R4 as 820, is this 820k?

Circuit diag. shows C3 as 0,01uf, some posts refer to 0.022uf or choose to taste, whats the effect of higher or lower values here?

Point to feed reverb signal back into main signal chain is node of C7/R11/R9?
( diag attached)

Was more questions than I thought!
All help and suggestions gratefully received

I’m going to put the reverb components on a small extra eyelet board to try and keep better track of what I’m doing, will post schematic of this once I have sketched it .

OK to pull all the reverb earth points back to the preamp star ground?

You'll have to ask Tubefiend about if he scaled the reverb or not but I know I would not scale the reverb circuit.

Anyways so yes take the supply for the reverb off the B+ standby node. This will be at the 32uF-32uF cap. Connect a resistor there (probably 22K-100K, your going to have to experiment, I'd try 47K first) and then filter it. 22uF at 450V is good for a filtering cap. Make sense?

C4 is a signal cap. It just has to be the right size so that stage is stable and not getting DC on the grid. I use 680pF for a bit more mids and not some much high end hash in the reverb tone. Classic Fender value is 500pF. Experiment with this value if you want.

R4 is 820R which is 820 Ohms. On the internet the Ohm's unit (Omega) is often written as R as we don't easily have a symbol for Ohms.

C3 is again a signal cap. If you like a bit more neutral sounding reverb go with 0.022uF. If you want a bit of bite and more presence try 0.01uF. Both values will work perfectly fine.

Your diagram is correct!

Bring all reverb grounds back to the preamp ground.

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http://pdfelectronics.com

Hi, for R4 & R6 I used 1.5k, also R10 I settled for 10K (I used 2W metal film).
I didn't scale the B+ power to the reverb cct, I don't see any reason to.
I ran all grounds to the preamp ground bar the filter cap. It went to the transformer star. No noise, all good!

Thanks for the advice, I'm going to put the reverb components an an extra eyelet board - helps a mech. eng. keep better track of making the right connections!

have posted a pic of how i think it should go together , if anybody spots anything wrong or improvable with that would be great to hear from you.

thanks

Edit reverb board circuit diag corrected for wrong connections betwen R3 and VRa grid, R4 and VRa cathode

Also now I have another question on VRM to keep reverb circuit out of scaling but not feed less smooth DC to reverb

VRM Diagramm says take input to VRM board from Standby , in order to not scale Reverb with rest of Amp I need to take B+ for reverb before VRM i.e. at standby switch, but then I would be relying on one filter 22uf capacitor to smooth Reverb B+

So I 'm thinking hook up the VRM between 32/32uf Filter Cap and Node of 22k resistors R25-28&42, then I can take a B+ feed to the reverb circuit which has already been smoother by the 32/32uf Cap and a 22uf Filter cap for the reverb power supply will be OK ????

The reverb circuit doesn't need a ton of filtering. 16uF and above should be fine.

What series resistance is there before the reverb supply though. You cant feed the circuit with the actual B+, it's too high.

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http://pdfelectronics.com

IMHO the last thing an amp with as much chime as a TC-15 needs is reverb. And the reverb circuit itself will have some detrimental impact, however small, on the amp's tone.

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Great tones come in small glass jars!

Hi Kurtlives , thanks for the reply ,

As I'm using a choke I have to play around with the series resistance on the B+ in any case as the voltage drop across the choke will be much less than the 1k5 . I guess as a start I will need to use the 1k5 in series after the 32/32 cap - possibly higher with 240V will get more than nominal 580 V at rectifier for 234Vac. For Reverb B+ will need to increase the series resistance in B+ to get down to the right voltages for the reverb triodes, but can do this with R1 and R7 in the reverb circuits right ?

Any reason not to put the VRM between the output of C13 and node of the 22k filter resistors ?

thanks Phil

Hi Zaphod, you may well be right about the Reverb, but hey its as much about the fun of building the thing. I'll find out when I actually get to hear a TC15 in real life!
Originally I was going to add the Reverb afterwards , but got just so far into the build and realised that would be way more work!
Can always move the reverb over to my next build if it doesn't work out !!