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The common assumption is that one PSU per channel is superior to both channels sharing a single PSU. But I've heard other arguments that a single PSU sounds better. I've also heard arguments that it's more important to have a PSU for each stage rather than each channel. So what are your reasons for preferring:
1) One PSU for a whole stereo amp
2) Two PSUs, one per channel
3) Two PSUs - one for the outputs and one for input and driver
4) Other
Follow Ups:
I am by no means one to say which is better in all applications but I built a pair of mono amps each on their own chassis using a single huge power supply(on its own chassis) as an experiment and AB'd it against each mono having its own power supply and I liked the way it sounded much better using a single power supply for both amps. Bye the way! Each mono when it has its own power supplies was a way over built design as well.
I am not all that technical when it comes to this stuff but all I can say is that I know what I like to hear.
If I am not mistaken Tre' built his amp with a separate power supply for the front end and another separate power supply for power section of his amp. He would be able to tell you the "why's and why not's" about doing something like that.
Hi!
Such a comparison is meaningless without details of each supply.
It is a common mistake to listen to two amps and then attribute the sound difference just to a single aspect of the amps.
Just 'way over built' says nothing. Actually way over building can be counterproductive and yield lesser results if done wrongly.
Best regards
Thomas
Is this a SE or PP design? The demands on the power supply are much greater in a SE design. My PP 300B amp is fully differential, including (the two) input stages. A nice design, lifted from Kevin Kennedy (with modifications). Worth considering ...
Option 3; and it works well if you can manage with 2 stages rather than 3.
Reasons:
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?
WRONG !
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?
Hi Andy,
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.
Best regards
Thomas
Hi Thomas,
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.
Andy
Hi Andy,
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 ;-)
Best regards
Thomas
Hi Andy,
this is a question which cannot be generally answered since many factors play a role. Different circuit topologies which are fed by the PSU will respond differently.
Also important how the channels and different stages are decoupled.
IME if there is sufficient decoupling between channels and stages, separate supplies bring little benefit.
Here are my preferences:
If space and budget is limited, use a single PSU for both channels and all stages. Ensure good decoupling, ideally separate LC stages for each channel and stage.
If more budget is available and also the required space, implement separate PSUs for driver and output stage.
Still more budget available, then go for all separate PSUs.
Also note that a single PSU, with top quality power transformer, properly designed and well decoupled will be superior to separate PSUs with low quality.
Best regards
Thomas
I am with Thomas as that is exactly how I build a stereo amp less the option of seperate PS for different stages. Best is seperate PS with monblocks. But more going on with monoblocks than seperate power supplies. I use a brute force power transformer with low DCR tube rectifier.
Excellent post.
I agree about the different topologies; even so, I'll just add this. In the example quoted in my above post, the cct driven by the cLCLC psu is a mu stage which has very high PSRR so, in theory, the PSU should have little effect on the circuit. That my be so on paper, but my ears can clearly hear differences between rectifiers ... no, I can't explain it. Punch line: even with a topology giving high PSRR, PSU differences are clearly audible.
I agree absolutely about the top quality mains transformer!
I use Sowter (I'm in the UK) and I over spec it massively; expensive, but so well worth it in my limited experience.
Regards
Mike
Hi!
There is much more to power transformer design than oversizing!
I had used Sowter power transformers in the past and honestly was not so impressed. But that was many years ago.
I'd be suspicious if rectifiers make such a difference. I would not want my amps to react like that to tiny changes.
best regards
Thomas
My vote would be for 3 first then 1. It seems to produce a more musical result to me however ...
2 produces "more hifi" and so for some it could be the winner.
cheers,
Stephen
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