#124 Questions

[Bombacaototal]

Further attempts to debug the start up issue. I checked and re-soldered the soldering of the PT star grounding and the artificial CT. All good


I decided to remove the tonestack from the audio path and leaving only the PI and there are no issues at start up. It is then fair to assume there os something going on at the Tonestack (and probably unrelated to its supply caps). I replaced the 12AX7 but didn’t notice any difference. At some point I had no audio and after re-soldering the pins of the stack and poking the socket the sound came back and I never had issues since, but I am wondering if there may be an issue with the socket itself

[pompeiisneaks]

I've had a brand new socket 'go bad' from me resoldering it over and over, I pulled it, replaced it and it fixed the issue, I actually got it happy again by removing tons of excess solder that had flowed upwards, possibly just making the pins have poor contact due to flux etc, reused it later as a test and it worked fine.

So it's possible.

You could also have a bad cap that's microphonic, have you chopsticked all those components int he tone stack and their leads to make sure they're not making noise?

~Phil

[xtian]

I suppose that delayed "click" could be a heat-related intermittent connection. But you should be able to reproduce the issue by chopsticking the connections, I'd imagine.

[Bombacaototal]

Thanks a lot Phil and Xtian. I will try the chopsticks tomorrow and report back

[Bombacaototal]

I am wondering what is the smallest relay transformer I could get to fit my donour Fender Deluxe Reverb chassis. The relay will only be used for switching the Overdrive ON/OFF. As I have space constraints (attached is what I am dealing with) I am hoping to find a viable option. Also I am trying to find a small relay supply board to fit sideways on the chassis side (standing like HAD did) but the Fender chassis are much shorter than the Dumble ones. It might not be possible to add it due to the space I have, but happy for suggestions

I came across this suggestion on an older post. I am running my amp at 240V (UK)
https://www.mouser.co.uk/ProductDetail/ ... OWNNnyo%3D

Lastly, does the footswitch jack need to be isolated for relays?

[erwin_ve]

Maybe take some measurements first on available space in the chassis? How much voltage and current do you need? That does make it a lot easier to find the right one.
Print transformers 9 or 12 v are possibly the smallest, downside is you need a pcb.

[Bombacaototal]

Maybe take some measurements first on available space in the chassis? How much voltage and current do you need? That does make it a lot easier to find the right one.
Print transformers 9 or 12 v are possibly the smallest, downside is you need a pcb.

Thanks for the reply Erwin.

I was thinking of using this DPDT https://modulusamplification.com/Relay- ... 32336.aspx and this board https://modulusamplification.com/Single ... 59290.aspx which would then be 12V, 3A. But of course happy to search more for whatever would meet the smallest available size transformer. This would be a 12V, 2A option https://modulusamplification.com/Relay- ... 32335.aspx

I still haven't found a source for the relay supply board.

I will measure everything up when I am back in London.

[erwin_ve]

Maybe take some measurements first on available space in the chassis? How much voltage and current do you need? That does make it a lot easier to find the right one.
Print transformers 9 or 12 v are possibly the smallest, downside is you need a pcb.

Thanks for the reply Erwin.

I was thinking of using this DPDT https://modulusamplification.com/Relay- ... 32336.aspx and this board https://modulusamplification.com/Single ... 59290.aspx which would then be 12V, 3A. But of course happy to search more for whatever would meet the smallest available size transformer. This would be a 12V, 2A option https://modulusamplification.com/Relay- ... 32335.aspx

I still haven't found a source for the relay supply board.

I will measure everything up when I am back in London.

The 2A and 3A versions for the relay, is how much current it can handle going through the dpdt switch(contact limiting current), the actual switch power consumption is 150mW. 0.15W/12V= 0.012A (12mA), The led function for the footswitch also around 12mA-20mA Depending on the LED and resistor used. . There is also a loss for the voltage regulator estimated around 12mA. 44mA total. Make it 100mA to be on the very safe side. So you need 12v/100mA on the secondaries.

As for the relay supply board; I have some left: they are 68x48mm. PM me if you're interested.

[dorrisant]

Can you pull your relay voltage from an existing AC tap? Filaments?

[pompeiisneaks]

I think that depends on how much extra capacity the 6.3V winding has for you. They're often pretty heavily used by the tubes. I also wonder if the relays may inject some switching noise if they're on the same circuit as the tubes.

I'm not 100% sure though, just a guess.

I would wager that the reason dumble used a separate transformer was to isolate them sonically from the audio path, but again, it's an educated guess.

~Phil

[erwin_ve]

Can you pull your relay voltage from an existing AC tap? Filaments?

I remember reading on early attempts resulted in hum.

[Bombacaototal]

Thanks Phil, Dorrisant and Erwin for the suggestions

@Erwin, I will start hunting for a transformer with the specs mentioned. As soon as I am back in London I will try to measure everything up and if your board fits I am in!

[dorrisant]

I understand going with an separate TX for peace of mind, but I have used the filament supply too many times to even count. I can assure you that it can be done with absolutely no noise. I have done several Hotel Hog type builds with absolutely no problems whatsoever. The relays themselves draw so little power that they hardly matter. The one thing that can cause problems is the grounding scheme for the relay power supply. Keep in mind that the relays dont need a conventional chassis ground, they can float.

That said, look at the Silver Jubilee and take notice of relay PS. That's one example, right under your nose.

You certainly dont have to do it this way but it has been done quietly in production amps... for years. Just sayin'.

[Bombacaototal]

That is very interesting Dorrisant. Did you notice any tonal, gain or voltage change by going to the mentioned approach on a Hotel Hog amp?

I am interested in giving a try, would you mind sharing more details on how you executed it? Many thanks

[norburybrook]

That is very interesting Dorrisant. Did you notice any tonal, gain or voltage change by going to the mentioned approach on a Hotel Hog amp?

I am interested in giving a try, would you mind sharing more details on how you executed it? Many thanks

Raphael, I would imagine you just need to rectify and filter it then send it through a voltage regulator.

Use a 5v regulator and relay, or use a voltage doubler like the regular dumble board and a 12v relay if you like...Or use the regular voltage doubler board and a 5v relay and regulator as those regulators will take up to 30V IIRC.


M