boobtube twin revisited

[thomasha]

Building a smps to deliver two different tensions is  more difficult than a single one. The noise from one side could affect the other.

You will definitely need a flyback transformer with some odd taps,  which would be difficult to find, or costly.

It ends up being a really complicated design when compared to a single SMPS. Take a look at your PC'S power supply for a better idea.

A simpler approach is using odd tube heaters, which already work at higher voltages like 25v and add them in series. Using a 24v transformer with center tap you can have 48v for heaters and with a quintupler circuit achieve almost 250v.

[sonolink]

Would something like this do?

[sonolink]

Bumpety bump!

[juansolo]

Quite simply because I run my pedals from a 9v DC centre negative PSU. Having multiple psu's is a ball-ache

Also, adding a transformer in there would be a significant bump in cost and parts to fit inside. Finally it's really easy to get the 190v from a charge pump as it's low current. The high current feed is the 6.3v or 12v for the heaters (depending on how you run them). So it makes sense to regulate a 9v supply to 6v for those. Or if you set the whole thing to run at 12v it makes it even simpler. It wouldn't really change what the SMPS delivers to the HV side either as 190v is about what it's nice and stable at.

If you want to go to the trouble/risks of dealing with mains voltages in a pedal, you may as well just build an amp, as that's what you're doing at that point.

[sonolink]

Right you are. I won't go that way. It was just curiosity
Thanks
Sono

[sonolink]

Hi again

Sorry for the delay but I got busy with other stuff. I picked up this project again and built the PSU. I use a 1 Spot 9v PSU connected to "9V" and "G" pins of the schem. When I juice it up I read 9v everywhere (Test, HV and 6V terminals).
I've checked the board several times but everything seems correct. Any ideas on what I could be doing wrong?

Thanks in advance for your time and help
Sono

[sonolink]

Update: the NE555 went up in smoke
Any help troubleshooting very much appreciated. Thanks

Cheers
Sono

[juansolo]

If you're in the uk you could send it over and we'll take a look at it.

[sonolink]

Hi Juan

I sincerely appreciate your kind offer. I live in Spain and it would probably be the easiest thing to do, but with all due respect, I'd like to fight this one myself (with some support and guidance of course)...I like this beast so much I want to make it mine if you know what I mean

So I went back to square one, back to strip board and back to Cleggs design, only adding a diode that is on GrindFX schem, one that bridges 9V to ground right at the start. I'm not sure "bridges" is the correct term but I think you get what I'm saying...excuse my language barrier

So I put it together this evening and fired it up and get to read 30V. I tweaked the voltage adjuster and POP went the 2.2uF electrolytic (it was the wrong way around). I replaced it and made sure it was the right way now. Fired it up again and now I get 300V!!

The thing is, when I tweak the pot it won't do much. It stays around 300-350V...of course I don't know if it's because something was blown together with the cap or because I placed something wrong...I guess anything is possible. If there's nothing obvious you can think of, I'll check the resistors, unsolder caps, diodes and ICs, check them and try again tomorrow and report back.

Thanks again for everything
Cheers
Sono

[sonolink]

UPDATE: It works now!!
There was a bad connection to the Vol. Adj. Once fixed the PSU seems to be now running smooth and I could adjust it to 190V

Cheers
Sono

[sonolink]

One more question please:

I am joining the Clegg PSU to 3 Optotrons on a vero. Both circuits original schems have a diode between 9V and GND. I guess I should put only one diode for the whole thing right? Or should I put one diode for each circuit?
Not sure this makes sense....

[juansolo]

Yeah you only need one.

[sonolink]

Excellent. Thanks Juan!!!

[sonolink]

Another couple of questions please:

1-The negative terminal of the DC connector would be the final GND terminal (like the green cable to chassis on an amp)?

2-On GrindFX schem "VA" and "VB" (connected to plate resistors) are connected to B+ (190V) right?

3-I've added True Bypass Switch and Clean/Crunch/Lead Channels to the circuit.
Here's the GrindFX schem:


Here's the same schem with the switches:


2-should C13 (right after the Master pot) go after SW2.B? SW4 is supposed to allow the player to choose to place the preamp in front of an amp (through 100k pot) or in its FX loop (through Presence circuit and 1M pot)

3-I just realized I won't be able to use the Opto to switch from Clean to "Dirty", right?
If so will a regular Stomp DPDT switch make noise when switching and is there a fix for that?

I really appreciate some input on these questions please
Thanks in advance for your time and help!!
Cheers
Sono

[sonolink]

Hello again,

A question about the PSU, please. If I want to use only one HV terminal (HVBA), can I just delete C7, R5, HVB1 and HVB2 from the schematic?

Thanks!