In reality the regulation of the transformer and your local mains voltage compared to the primary voltage will probably make more difference than the 1V difference in the specified voltage... 21VAC will be fine.
IMHO R-Cores are best but a pair of good quality toroid from 160VA will do fine.
Feedback from previous builder would suggest use of 200VA as a minimum for best sound quality.
Is a 400VA dual secondary toroid okay or does having two toroids make a noticeable improvement?
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For best results two transformers should be used but a single 300VA toroid or R-Core worked fine for several builders.
I am not sure if i get this right, why would you recommend 120va rcore or 160va toroidal.
I think the 120 va rcore would work exactly like an 120va toroid ,
but with a little better efficiency , but they would both output the same power. How much juice the amp will suck from the wall is not discussed here at all.
If a transformer is rated 120va , then will output 120va, regardless if is rcore, toroid or e+i ....What is different is the efficiency , size, noise, temperature etc.....
I think we need at least 100va /channel, 120 would be great(but if you have space in your case, money in the pocket then you can go to 1kva transformer, I dont think will make any sonic difference) for an 60Watts amp, class ab amplifiers efficiency will go up to 66%, lets say 50% in the worst case scenario.
Let me know if you guys think differently.
I think the 120 va rcore would work exactly like an 120va toroid ,
but with a little better efficiency , but they would both output the same power. How much juice the amp will suck from the wall is not discussed here at all.
If a transformer is rated 120va , then will output 120va, regardless if is rcore, toroid or e+i ....What is different is the efficiency , size, noise, temperature etc.....
I think we need at least 100va /channel, 120 would be great(but if you have space in your case, money in the pocket then you can go to 1kva transformer, I dont think will make any sonic difference) for an 60Watts amp, class ab amplifiers efficiency will go up to 66%, lets say 50% in the worst case scenario.
Let me know if you guys think differently.
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Not in my experience, one single 120VA sounded fuller/louder than a single 225VA toroid powering two modules.
One measured difference was secondaries voltage under load, the r-core measured around 24V while the toroid around 22-23V.
When unloaded both measured around 27V.
The suggested general minimum rating is 160VA, r-cores will do at 120VA.
Yes , i do believe you are right about powering 2 amps from 1 transformer is not so good as using 1 transformer for each channel. I am using Antek transformer, they are bigger in size than most of other toroid brands transf for the same rated power , under load they sink around 1.5 volts max.
I have a pair of Antek 300 VA powering an early FE amp. Early on I tried powering both channels with one 300 VA, just to experiment. The original reason was to reduce the potential for hum. The good news was that there wasn't any measurable increase in hum. There are probably other reasons to prefer separate transformers, but I didn't try it long enough to say.
As for Antek's, they are a great deal, but one of these days, I've got try R-cores. Dario isn't alone in preferring the trade-offs of R-core.
I think we are all agreed that the least efficient is the EI. Ccore is possibly similar.
I think we are also all agreed that the continuous strip form of core is more efficient.
I doubt there is much difference in efficiency between Rcore and Toroid if they are of the same quality in manufacture and design.
I have a feeling that the Toroid is more efficient. I have a strong feeling that the extra core length of the Rcore will ensure that the Rcore cannot be more efficient.
But this is all guesswork, because few manufacturers make more than one type and few give us comparable efficiencies.
Many give transformer regulation values and these seem to indicate that Toroid drop less voltage when under load. To me that seems to indicate a higher efficiency.
Do you have some evidence to support Rcore efficiency?
That seems to me that they were built very differently.
3Vsag for a 120VA driving 1 power amp to full power (60W) seems likely.
but 5Vsag for a 225VA driving 2 power amps to full power (60+60W) seems to indicate some fault in the PSU.
The 40volts capacitors should be good since you should never go over 35v each rail. Most of us are using 22v transformers , after bridge rectifier we get around 28-30volts.
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With 24V secondaries you would have 36-37V on those caps and 40V rating would give you not enough margin, IMHO.
It could with 21V secondaries.
Use the BGs, KZs are worse.
I prefer Cerafines but you will be perfectly happy with Black Gates.
Black Gate Standard is warmer and a tiny bit less 'rich' than Cerafines.
Cerafines have an higher harmonic content and are a bit more neutral, so more open than Black Gates STD.
Don't bother with BG N or NX, IMHO they're too much colored.
I've been looking at my power supplies and wondering if they need snubbers or not.
Does anyone else run these on their transformers and do they improve any aspect?
Also, after looking back at the v1.5 plus boards schematic I noticed C103 and C203 100nF caps but I cannot find these on my boards (9th run). Are these recommended?
Does anyone else run these on their transformers and do they improve any aspect?
Also, after looking back at the v1.5 plus boards schematic I noticed C103 and C203 100nF caps but I cannot find these on my boards (9th run). Are these recommended?
My explanation could be not so precise but let's go:
Usually snubbers are usefull to damp the interaction of rectifiers with transformer.
Using soft recovery diodes their effectiveness is way less, and IMHO they're not needed here, otherwise how could THD+N be so low?
Absolutely not, those positions are there as an option and their use is discouraged in BOM.