If I understand what Susan wrote on her website, the output transformer she used in her 35W Zeus had both 2:1 and 4:1 windings:
Zeus Amp - Original with IRFP150 mosfets - inc FFT tests
My speakers are 8ohms, so I'm wondering if I can use the 3:1 windings of the output trafos?
The Input trafo seems simple enough, I could use a mains trafo that has a pair of 120v primary windings and a pair of 12v secondary windings, wired up the 'wrong' way round that would give the 1:10 Susan used for her 35W Zeus. I think I happen to have a couple of 12v output toroidals that would do the job, I shall go dig in my box of bits and see if the pile of toroidals in there contains anything suitable.
Probably the hardest bit is going to be obtaining matched pairs of power MOSFETs. I read the page on Susan's website about how to match them, seems straightforward enough, but I am thinking I would need a batch of 20 in order to be able to find two suitably matched pairs and buying 20 power MOSFETs isn't cheap. I do have two different MOSFETs (IRFR214PBF & FDD8447L) in quantities of 50, but they are both in the to-252 packaging and probably don't have sufficient power handling for this application. I also have 14 IRF820s but they are TO-220 and also probably won't be upto the job. I probably need TO-3P power MOSFETs and buying 20 of those is quite an expense.
Zeus Amp - Original with IRFP150 mosfets - inc FFT tests
I think the output trafos in this amp I have have both 2:1 and 3:1 windings - the 2:1 producing the 70V line output and the 3:1 producing the 100V line output.
My speakers are 8ohms, so I'm wondering if I can use the 3:1 windings of the output trafos?
The Input trafo seems simple enough, I could use a mains trafo that has a pair of 120v primary windings and a pair of 12v secondary windings, wired up the 'wrong' way round that would give the 1:10 Susan used for her 35W Zeus. I think I happen to have a couple of 12v output toroidals that would do the job, I shall go dig in my box of bits and see if the pile of toroidals in there contains anything suitable.
Probably the hardest bit is going to be obtaining matched pairs of power MOSFETs. I read the page on Susan's website about how to match them, seems straightforward enough, but I am thinking I would need a batch of 20 in order to be able to find two suitably matched pairs and buying 20 power MOSFETs isn't cheap. I do have two different MOSFETs (IRFR214PBF & FDD8447L) in quantities of 50, but they are both in the to-252 packaging and probably don't have sufficient power handling for this application. I also have 14 IRF820s but they are TO-220 and also probably won't be upto the job. I probably need TO-3P power MOSFETs and buying 20 of those is quite an expense.
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I note that Susan has also built a version using triode valves instead of MOSFETs:
Zeus 6C33C-B Triode Tube Line Driver
Susan used the Russian 6C33C which cost over 30ukp each, but I'm thinking I could build a lower powered version using cheaper tubes such as the Russian 6P1P as you can buy matched pairs and quads of those cheap, which gets around the issue of buying a batch of MOSFETs and matching them.
4pcs ( MATCHED QUAD ) 6P1P-EV (6P1, 6П1П-ЕВ) VACUUM PENTODE TUBES, USSR / NEW | eBay
Zeus 6C33C-B Triode Tube Line Driver
Susan used the Russian 6C33C which cost over 30ukp each, but I'm thinking I could build a lower powered version using cheaper tubes such as the Russian 6P1P as you can buy matched pairs and quads of those cheap, which gets around the issue of buying a batch of MOSFETs and matching them.
4pcs ( MATCHED QUAD ) 6P1P-EV (6P1, 6П1П-ЕВ) VACUUM PENTODE TUBES, USSR / NEW | eBay
Ian-- if you are thinking of using the existing output transformers ,while they may cover the audio band are they up to a high standard of fidelity as regards leakage ,inductance across the full audio frequency band etc.
Yes they look high quality but transformers designed for factory/office transmission of information (announcements ) to those working in various parts of the building/factory aren't always to the same standard .
What information is printed on the output transformers ?
Yes they look high quality but transformers designed for factory/office transmission of information (announcements ) to those working in various parts of the building/factory aren't always to the same standard .
What information is printed on the output transformers ?
Sensible questions Duncan. I think the transformers aren't absolutely critical, as Susan has posted experiments using normal power toroidals and says the results are more than adequate:
Zeus Amp - Toroid Transformer Version
I had a root in my box and was able to find three matching pairs of toroidal trafos, one doesn't have the ratings printed on, but the other two might be suitable:
Primary: 2x115v, Secondary: 2x25V @ 1A
Primary: 1x240v, Secondary: 2x24V @ 0.52A
I also have a set of four huge toroidals, Lintron part number 26282/2:
Prim 0-215-225-245 Volt
Sec 0-24-28,5 Volt/ 6A
0-28,5 Volt/6A
0-14 volt/6A
These big Lintrons could probably be used as output trafos according to what Susan wrote on the page I linked.
Zeus Amp - Toroid Transformer Version
I had a root in my box and was able to find three matching pairs of toroidal trafos, one doesn't have the ratings printed on, but the other two might be suitable:
Primary: 2x115v, Secondary: 2x25V @ 1A
Primary: 1x240v, Secondary: 2x24V @ 0.52A
I also have a set of four huge toroidals, Lintron part number 26282/2:
Prim 0-215-225-245 Volt
Sec 0-24-28,5 Volt/ 6A
0-28,5 Volt/6A
0-14 volt/6A
These big Lintrons could probably be used as output trafos according to what Susan wrote on the page I linked.
Okay Ian its always down to each person and as you have quoted in bold type and are happy with that okay , I just wanted to make sure it was your own decision and knew the audio position.
Oh, I very much appreciate you pointing it out.
I fully acknowledge that I'm not using the ideal trafos, and am taking the approach of 'let's try it and see how well it works' with full realisation that it might not sound as good as it might with more ideal parts.
I fully acknowledge that I'm not using the ideal trafos, and am taking the approach of 'let's try it and see how well it works' with full realisation that it might not sound as good as it might with more ideal parts.