All my parts are winging their way to me as they speak...I suppose that is progress.
I've gone with 2 x 400VA transformers, Cree SiC schottky's and the ridiculously expensive 33,000uF Mundorf electrolytics in the power supply.
For the amp I plan to forego the input cap...my entire system is DC coupled. I always use VAR resistors at the input and this amp will be no different.
Pretty sure that I will build my own case rather than get a chassis from somewhere online. That way it ends up exactly as I need it to be. Am looking forward to the build...it should be fun.
I've gone with 2 x 400VA transformers, Cree SiC schottky's and the ridiculously expensive 33,000uF Mundorf electrolytics in the power supply.
For the amp I plan to forego the input cap...my entire system is DC coupled. I always use VAR resistors at the input and this amp will be no different.
Pretty sure that I will build my own case rather than get a chassis from somewhere online. That way it ends up exactly as I need it to be. Am looking forward to the build...it should be fun.
Toroidy are winding my transformers as well. I've never used them before and do have a strong preference for big EI power transformers (better mains filters and they will also handle DC on the mains), but I'm not sure I will have room for them in the case because they need a fair bit of room around them so they don't couple with stuff magnetically. That, and the guy that normally winds them for me is very busy and I probably would not see them for at least a few months. I talked to Toroidy and the two audio grades they produce are identical transformers apart from one being potted in a stainless steel can. I'll provide my own magnetic shielding so I went with the less expensive tx.
Do, did you happen to test your psu with normal caps (such as Nippon Chemicon) before you went to the Mundorf exotics? I was very hesitant to go straight to the Mundorfs but the 25% off pcX sale and the 6mR ESR certainly helped sway me.
I was thinking that in the PSU I would not install the bleeder but would perhaps try a low value film cap in that position, say 1-3uF. Another option would be a third large electro but if that happens I'll need to leave some room off board.
Anthony
Do, did you happen to test your psu with normal caps (such as Nippon Chemicon) before you went to the Mundorf exotics? I was very hesitant to go straight to the Mundorfs but the 25% off pcX sale and the 6mR ESR certainly helped sway me.
I was thinking that in the PSU I would not install the bleeder but would perhaps try a low value film cap in that position, say 1-3uF. Another option would be a third large electro but if that happens I'll need to leave some room off board.
Anthony
Anthony,
Shipping must be crazy to Oz, as it is crazy to the USA as well. Both the audio grades that Toroidy offers are electrostatically shielded and have magnetic shielding too. The higher priced one “looks” better and is potted. That being said for a Class A amplifier I would exercise some caution if you are thinking about potting due to heat issues. And I would go with the larger sizes or dual mono. Vertical mounting will also help with cooling.
Best,
Anand.
Shipping must be crazy to Oz, as it is crazy to the USA as well. Both the audio grades that Toroidy offers are electrostatically shielded and have magnetic shielding too. The higher priced one “looks” better and is potted. That being said for a Class A amplifier I would exercise some caution if you are thinking about potting due to heat issues. And I would go with the larger sizes or dual mono. Vertical mounting will also help with cooling.
Best,
Anand.
Hi Anand,
Yes, shipping to oz is nasty, but that is the price we pay for being able to live in isolation down here. For the USSA-5 build I have three shipments from Europe, two from Canada and three from the US. Some of the parts can be had locally but not many.
The voltage regulation on the power transformers is about 4% which is about as good as it gets. This tells me they use a large core which tells me that it should be able to disperse the heat reasonably efficiently. Toroids are so efficient too, so there is not as much heat as with other transformer types in the first place. I just hope they don't hum...that would be very annoying.
Cheers,
Anthony
Yes, shipping to oz is nasty, but that is the price we pay for being able to live in isolation down here. For the USSA-5 build I have three shipments from Europe, two from Canada and three from the US. Some of the parts can be had locally but not many.
The voltage regulation on the power transformers is about 4% which is about as good as it gets. This tells me they use a large core which tells me that it should be able to disperse the heat reasonably efficiently. Toroids are so efficient too, so there is not as much heat as with other transformer types in the first place. I just hope they don't hum...that would be very annoying.
Cheers,
Anthony
Yeah, I'll also need a soft start for those transformers. I was just going to use a simple circuit but I found this online and thought it looked really good and would be very useful to handle not only the soft start, but also the mains switching, 12V trigger, fuse et cetera. Just put a low voltage push button on the front panel, an IEC socket on the back and the job is done. I do really like captive mains leads so I might even forego the IEC socket entirely.
I finally got the 1.5K 3w meal film resistors a few days back, Everything was going as in the manual, got 0.3Vdc in chapter 8.14. until I got the laterals installed, I connected the board to intended power supply, connected both PGND and GND as described in 8.17.1, but the reading between both TP4 and V- and TP2 and V+ on both boards are zero, I checked the schematic and is n't TP4 and TP2 connected to to rails via R16 and R15 ? 
what am I doing wrong here ?
what am I doing wrong here ?Attachments
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Fab has set 0.3Vdc in chapter 8.14 to have these 0V before setting the BIAS to avoid problems.
Now you have to set the BIAS (50 mV) and I invite you to proceed as follows:
USSA-5 Build with Review
Now you have to set the BIAS (50 mV) and I invite you to proceed as follows:
USSA-5 Build with Review
Thanks. Almost ... Just calculated and ordered the RV resistors.
yeah I also like to see how it went, not sure if the PS he had was sufficient enough for this amp (2x2.5A for each channel). I do have the transformer, but I may give it a try with the SMPS I have for my Alpha20 (2x9.5A in parallel per channel), just outta curiosity.
yeah I also like to see how it went, not sure if the PS he had was sufficient enough for this amp (2x2.5A for each channel). I do have the transformer, but I may give it a try with the SMPS I have for my Alpha20 (2x9.5A in parallel per channel), just outta curiosity.