[Ferrari]

Quote:

Originally Posted by pabbi1 /img/forum/go_quote.gif ... Also, did you air wire the tubes?

Yes, I air wired the tubes sockets.

(I see that runeight has answered your questions regarding heaters voltage and transformer).

 

[pabbi1]

Does anyone know Mouser part numbers for the header/jumpers?

 

[dBel84]

we thought a switch would be better ..dB

 

[mwofsi]

Can I ask a couple of power supply design questions (this isn't about the SOHA II, it's more to improve my comprehension) ?

What roll does the size of caps in the voltage doubler play? Presumably too small and they'd be fully charged before each phase change? Can they be too large? Do they also play a role in smoothing and ripple removal?

Also what are the advantages of using capacitance multipliers?

 

[pabbi1]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif Here are some photos of the prototype panels. I messed up the mounting holes in the corners and I had to countersink them with a drill bit. They are a bit ugly but won't be on a production panel. I've fixed the hole size and the countersink on the FPE drawings.

Can I get the FPE files, on the proviso that it is a truly one off? I am making but one of these, but since it is for my brother, I want it done as well as possible.

 

[runeight]

Quote:

Originally Posted by mwofsi /img/forum/go_quote.gif Can I ask a couple of power supply design questions (this isn't about the SOHA II, it's more to improve my comprehension) ? What roll does the size of caps in the voltage doubler play? Presumably too small and they'd be fully charged before each phase change? Can they be too large? Do they also play a role in smoothing and ripple removal? Also what are the advantages of using capacitance multipliers?

mwofsi, there is some new information on the Cavalli Audio website about voltage multipliers under the SOHA II design section.

The capacitors in the multiplier pass large current pulses as they charge and discharge. The larger the capacitor the less "resistance" it offers to these pulses. At some point the capacitor is "big enough" and further increases in size generate only small returns. The values in the SOHA II PS are chosen to balance capacitance value (bigger is better) vs. physical size (smaller is better).

In a full Cockroft Walton multiplier some of the capactors can play the role of reducing ripple, but this depends on how you set it up.

In the SOHA II multiplier only the last capacitor acts as a filter capacitor as well as a multiplier cap.

The advantage of a voltage multiplier is that you can get high voltages from a low voltage transformer. In the SOHA II we get 105V from the same transformer that generates the split 15V supply. This is pretty good work and permits us to stick to the SOHA design philosophy of using only one transfomer to power the hole amp.

 

[mwofsi]

Thankyou for explaining that.

Capacitance multipliers? Q1/Q2P, are they just about size constraints or do they improve the capacitors performance as well?

 

[runeight]

In this case they are the same result. A cap multiplier allows you to use a small capacitor that acts and performs like a much bigger capacitor. The capacitance value of the cap multiplier is approximately the value of the real capacitor multiplied by the hfe of the transistor.

There is a nice article at Wikipedia here:

Cap Multiplier

 

[holland]

I cased up my build this weekend. HV on a PC board, running @ 95V. It's feeding into the prior D9P and D10P using a 2 pin Molex connector.

I need a new knob, it's not big enough to cover the keyhole.

 

[holland]

Quote:

Originally Posted by uhcmos /img/forum/go_quote.gif SOHA II - Super SE Hybrid

err...yep, that's the name of the thread alright.

 

[dBel84]

been meaning to say I like this case - a very good hammond alternative.

What is the power switch you have used? I thought it was the momentary switxh for the e22, but it must be a regular type as I don't see anything else in there? ..dB

 

[holland]

Thanks dB. It's a Hammond 1402FV. The board fits in the side rails as well, but I wanted full internal mounting. It's more pricey than the typical aluminum and a bit bigger, and heavier since the top and bottom is pretty thick steel with nice front and back plates.

I was seriously going to go for the top mounting, but just couldn't make myself do it. The shades of yellow theme would play better in gradations of yellow/amber. I'm still keeping an eye out for a nice gold/amber 1/4" jack.

The power switch I got off e-bay from PartsPipe. It's a Bulgin imitation or copy, but it is the latching variety so the button depresses in and sticks. I have to hit it with my pinky, fat fingers apparently. I am using a wallwart and am using the DPDT switch to pull the 2 15V AC rails. There's no room in the case for a toroidal, after the PC board. It's illuminated as well, and takes a 12V input for the internal LED. I'm not sure if there's a current limiting resistor in it, there's no docs on this switch, but I had to use a 120 ohm resistor to get something that's at least visible in daylight so I presume there is. I didn't want to try a link, but I have a feeling it would work.

 

[dBel84]

Quote:

Originally Posted by holland /img/forum/go_quote.gif It's a Hammond 1402FV. ....

aaah , does it show that I have never explored hammond or most other commercial offerings.

Quote:

Originally Posted by holland /img/forum/go_quote.gif The power switch I got off e-bay from PartsPipe. It's a Bulgin imitation or copy, but it is the latching variety so the button depresses in and sticks

Oh thats great, thanks. He is the guy that does the heavy aluminium knobs..dB

 

[pabbi1]

Follow up, since you never explicitly said no...

Can I get the FPE files, on the proviso that it is a truly one off? I am making but one of these, but since it is for my brother, I want it done as well as possible.

Pretty please?

 

[pabbi1]

Well, all my parts arrived today for the SOHAII build (I am shocked - really)... and, though production boards are due this week, are there any spare pre-pro boards out there, that, maybe, someone didn't get around to building? If so, ping me...

Oh, and what fuses are you guys using? I have 1a and 3a slo-blo on hand.