Yes, I was expecting to see the mains transformer between the two output transformers as is common on many other stereo valve amps. I e-mailed the seller about this and they said that it has a toroidal transformer hidden underneath. I have not come across that before with a valve amp, hence wondering whether it would be OK.
Since you will be using them with a DAC, you should bypass the first tube stage (arrange the NFB to the 2nd stage), give them a little TLC on wiring and powersupply components, and they go silent, no big'e!
My clone of HFA12 was so noisy, the guy sold it as "for parts only" - now if you put your ear right to the speaker, in a quiet room, you might hear a little hum, if you concentrate hard!
at 4 inches away, nothing!
BTW I have 20-20 hearing
(though my mum always said I don't listen)
Well not necessarily just a DAC. I would like to run my Thorens turntable through it via a phono preamp. I might also run my Satellit radio through it. It does a very good job with FM. But yes, I might also connect a CD player, tablet or other digital kit to it so I might have to plan a way to cater for both possibilities.
Agreed. One of the thinga that struck me about the Hammonds was that they appear to have pretty hefty transformers. I do have a 110v 1A transformer for my Eddystone radio, but I do not believe it will support two of these amps simultaneously. The seller suggests the amps can be wired in series which means they will still end up being slightly overrun on 230v. I don't know how safe or advisable it is to run two amps in series like that?
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I was referring to the mains transformer, not the output ones.
Toroidal is good.
I acquired a Cambridge Audio 640p some time ago and upgraded the op amps which made a big difference to the output. Some have said that replacing the capacitors makes a difference as well. There is also a mod that removes the first transistor stage. I decided to leave that alone though. There obviously are much better pre-stages out there, but this was sufficient for my budget. Thank for confirming that the toroidal power transformer should be OK.
I see your point. I can see why interleaving would add to the cost. So how do you know whether a transformer is interleaved? Did they do this on vintage equipment or is this a relatively modern development?
Good vintage like the one I mentioned would have used more than average to obtain it's sonic quality. I believe from reading Dynaco used 4 and maybe more on the Z565 and the lower end was towards guitar output trans which probably had none. There are are at least 3 clone makers of popular Dynaco Iron in NA anyway.
It is a secret on most new production and from lots of reading the high end ones new or old can go to 11 or 12.
There is a really nice helpful Australian fellow now retired from winding Output Trans with lot's of info on his site. Patrick Turners site:
for-sale-3-output-transformer-notes
The Peerless line from Altec Lansing must have used many layer back in the 50 into the 60's when they made theirs as they are highly regarded for their sonics now.
Sowter in the UK a well regarded firm does give specs. They talk about 14 interleaved layers, but it may be 7-8 layers the way others like Patrick above or a former designer of Dynaco mentioned they started with 4 with a parallel winding method.
SOWTER PUSH-PULL OUTPUT TRANSFORMERS
Edcor in the US offers very affordable SE & PP , and there seem to be some complaints on their PP , but really none with there SE. Someone on one of the forms from living in the EU unwound a PP as he wasn't happy with it a few years ago and found only 3 interleavings. Maybe they do more on some or for sure on the SE? But what do you expect at their very nice prices! Out of country shipping is may be very high though.
Hammond is a very old CDN maker of affordable ones whom have some being well liked also.
If you do lot's of reading C core's seem to be popular now on the high end and bigger makers like Hashimoto (mostly) and Lundal (all) use them nowdays unlike the vintage which were mostly IE. Lundahl (Sweden) offers a Hi End core material for a big price increase that many seem to really like on the forums. Macintosh wound their own type of C core I believe even back in the day. There are a few Toroid Output Transformer Makers out there with a big price range like Piltron (they may be only Hi End) from Canada. They are harder to get right and maybe very circuit dependent from what i've read.
http://www.diyaudio.com/forums/tubes-valves/162679-transformer-maker-list.html
TransformerSuppliers - diyAudio
This company could be added to the list as they now make an affordable Hi-Fi PP Output Trans with a useful primary K range.
40-18080
There is also another new maker in the last year or so from the EU mentioned on this forum for their SE Hi end and coming PP Output trans , but they used exotic materials and hopefully windings, & so are quite expensive.
It is a secret on most new production and from lots of reading the high end ones new or old can go to 11 or 12.
There is a really nice helpful Australian fellow now retired from winding Output Trans with lot's of info on his site. Patrick Turners site:
for-sale-3-output-transformer-notes
The Peerless line from Altec Lansing must have used many layer back in the 50 into the 60's when they made theirs as they are highly regarded for their sonics now.
Sowter in the UK a well regarded firm does give specs. They talk about 14 interleaved layers, but it may be 7-8 layers the way others like Patrick above or a former designer of Dynaco mentioned they started with 4 with a parallel winding method.
SOWTER PUSH-PULL OUTPUT TRANSFORMERS
Edcor in the US offers very affordable SE & PP , and there seem to be some complaints on their PP , but really none with there SE. Someone on one of the forms from living in the EU unwound a PP as he wasn't happy with it a few years ago and found only 3 interleavings. Maybe they do more on some or for sure on the SE? But what do you expect at their very nice prices! Out of country shipping is may be very high though.
Hammond is a very old CDN maker of affordable ones whom have some being well liked also.
If you do lot's of reading C core's seem to be popular now on the high end and bigger makers like Hashimoto (mostly) and Lundal (all) use them nowdays unlike the vintage which were mostly IE. Lundahl (Sweden) offers a Hi End core material for a big price increase that many seem to really like on the forums. Macintosh wound their own type of C core I believe even back in the day. There are a few Toroid Output Transformer Makers out there with a big price range like Piltron (they may be only Hi End) from Canada. They are harder to get right and maybe very circuit dependent from what i've read.
http://www.diyaudio.com/forums/tubes-valves/162679-transformer-maker-list.html
TransformerSuppliers - diyAudio
This company could be added to the list as they now make an affordable Hi-Fi PP Output Trans with a useful primary K range.
40-18080
There is also another new maker in the last year or so from the EU mentioned on this forum for their SE Hi end and coming PP Output trans , but they used exotic materials and hopefully windings, & so are quite expensive.
rmyauck, thanks for all of that information! The information on Partick Turner is very useful indeed. The list of suppliers is also helpful. Lots to consider! I notice in the small print at Sowters that these prices are ex VAT so another 20% would need to be added! It doesn't say whether the price is for a matched pair as per from Turners or for a single transformer but no wonder this is the most expensive part of the amp!
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Thanks! Glad to help!
I found Transcendar now sells copies of well regarded output transformers from Fisher & HH Scott (E-Bay Links- but you can probably direct order) from back in the day and they are nicely affordable.
AudioKarma has had a number of recent (last few years) builds with improvements for those with schematics shown.
Push-Pull Transformers - Transcendar Audio Transformers
I found Transcendar now sells copies of well regarded output transformers from Fisher & HH Scott (E-Bay Links- but you can probably direct order) from back in the day and they are nicely affordable.
AudioKarma has had a number of recent (last few years) builds with improvements for those with schematics shown.
Push-Pull Transformers - Transcendar Audio Transformers
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