What DIY amp with 75V PS?

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#23
Agreed, the Wolverine looks incredibly promising, and it would suit the 55+55V rails that JMFahey derives above. I (being of an open-source kind of attitude - I publish my PCBs on github) would very much like to see the design formally released, though I do understand that they are fundraising for the forum or something and it would suck for the authors if there are bad clones in the market.

I mean, I'd buy a pair except I have a stack of like 20 other amps sitting here in the cupboard waiting to be assembled 🙂
 
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#24
jwilhelm said:
The 70V supply thing doesn't make sense for a Rotel RB-2000. It's a 120W amp so voltage is likely closer to +/-50 for the output stage. The schematic I was able to find show +/- 70V for the input stage but I wasn't able to find a voltage spec for the output stage (separate transformer winding).
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Actually this is a really good point. Some amps use a second pair of regulated rails at about 10V above the main supply rails, to run the Vas and driver stages, which means you can swing the output much closer to the main rails and therefore make some non-trivial thermal and noise savings.

For example, the Silicon Chip 100W "ultra low distortion" is one that I've built (a pair are currently running woofers in my loungeroom stereo). It uses two toroids, each with 2 separate windings that are all stacked up in series: 9+35+35+9V. The 35V windings are 300VA and the 9V (IIRC) are like 20VA.
 
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#25
laplace said:
Some amps use a second pair of regulated rails at about 10V above the main supply rails, to run the Vas and driver stages, which means you can swing the output much closer to the main rails and therefore make some non-trivial thermal and noise savings.

For example, the Silicon Chip 100W "ultra low distortion" is one that I've built (a pair are currently running woofers in my loungeroom stereo). It uses two toroids, each with 2 separate windings that are all stacked up in series: 9+35+35+9V. The 35V windings are 300VA and the 9V (IIRC) are like 20VA.
Click to expand...
here is a cheesy design VOX Q Series Guitar power amp, doing that with no need for an extra transformer, just a 6-8Vextra winding made out of fine wire (hint: cheap and easy)
Main centertapped winding feeds the main amp rails through a bridge; the extra winding creates ~extra 8-10Vdc floating on main rails.
* no need to regulate them IF anyway main rails will ripple and drop with load.

* they use just one extra winding and 2 diodes, used as half wave rectifiers to provide extra voltage.

They can get away with it because driver power consumption is minuscule, and in any case, main rails ripple is the enemy, not he tiny extra one.

VOX Q100 extra drive rails.gif


EDIT: corrected small mistake in schematic labelling.
 
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