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In Reply to: RE: Single PSU or dual mono best in amps?? posted by andy evans on June 18, 2012 at 09:42:03
Option 3; and it works well if you can manage with 2 stages rather than 3.
The perceived result (noted and commented on by knowledgeable friends) is that it gives fast, clean 'leading edges'; even my low power SETs do not sound in the least slow or lazy!
Remember that Naim use the same principle of splitting PSUs by stage rather than by channel, again getting good leading edges.
More generally, look at things this way. The output stage PSU current is heavily modulated, and if this modulation gets to the driver stage PSU it will corrupt the signal. If the driver stage PSU is taken from the output stage PSU, a carefully chosen decoupling stage (usually a simple RC) is added to the driver PSU. OK so far, it works ...
But I question how well this can work, for this reason.
My 300B SET (with separate PSUs for the stages) uses a GZ34 rectifier for the driver stage PSU. This is followed by a cLCLC filter, which models well in PSUD and is extremely quiet. So any audible effect due to the rectifier valve isn't going to be heard through that filter is it?
The differences between metal base GZ34, black base GZ34 and 5U4GB are clearly audible.
So ... if cLCLC can't isolate a rectifer valve, what chance is there of a simple RC isolating the driver PSU from the major modulations in the output PSU?
All personal experience and opinions, others opinions will no doubt differ! :-)
Assuming three stages in an amp, and splitting the PSU between stages - if you use two PSUs, do you have:
1) One PSU for output and another for input and driver
2) One PSU for output and drivers and another for input
Could do it either way - what do you think?
a good choice is only possible in the context of the design.
This is like asking which are the best tires for a 4 door car ;-)
Depending how sensitive the stages are against interaction either of the choices can be better. Fotr example this can depend on teh amount of voltage amplification in a stage and wether it flips phase or not.
As regards design. My regular design is all-DHT, in fact I only use DHTs unless customers want something else like 6SN7 into 807.
I've buit 300B SETs with 26-46-300b
Currently PP 26-4P1L-2a3
First two stages are usually direct coupled.
now we know your car has 4 doors and a naturally aspirated engine ;-)
The funny thing is, if you would ask such a question on a car forum, you will most likely get responses with specific recommendations and how they will impact the driving of your car ;-)
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