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johnm 27th February 2007 09:08 AM

Survey: SMPS with or without stiffener cap?

Been reading alot about people using their SMPS power supplies with Tripath amps and preferring them without any stiffener cap. Thought I'd start a little survey just to see what people's experiences have been.

For my part I use an Amp6 Basic (totally stock apart from Black Gate N 4.7uF input caps, but I also have some 2.2uF obligatto's which I shall try soon), with a Skynet 8080 SMPS bought from NuuK. I have tried it with a 10,000uF Elna cerafine on the output, a Nichicon Power 20,000uF capacitor, and just a 1200uF Panasonic FC, and without any stiffener capacitor at all. To my ears I prefer the sound without a stiffener cap - it just seems more natural, and less murky sounding. The sound of strings on classical are alot smoother and sweeter, more delicate than with the stiffener cap. Detail seems better as well. Rock is perhaps not QUITE as ballsy, but there's hardly anything in it, and the extra detail and crispness is worth the trade off. My speakers are Mission M72s, 8 Ohms and an 89db sensitivity.


- John

Pano 28th February 2007 04:59 AM

For me the stiffener cap has always sounded better, therefore I always use them.

But I just got a Skynet 8080 today, so will be able to listen to how it works with and without tank cap. Maybe it doesn't like the xtra cap?

For me the stiffener cap does several things:
  • Wider soundstage. I suppose this comes from lower crosstalk via the PSU.
  • More stable image.
  • Better dynamics because of less supply sag.
  • More headroom.
  • Tigher, more solid bass.
  • A tonal shift into the low mids. Sounds more natural, fuller - to me.

Of course this will depend on your system and your power supply. For me the stiffener cap has always sounded better. But some people don't like them.

johnm 28th February 2007 09:32 AM

I'll be very interested to find out your experiences with/without the stiffener cap in the 8080.

I just found that the amplifier sounded 'correct' without it. Just a gut feeling that everything is sounding as it should? At the end of the day this amplifier doesn't have huge power demands so perhaps this is a case of less is more? I know those with Gainclones gerenally prefer a lower capacitance than has traditionally been the case with solid-state, so perhaps the Tripath chips are similar in this respect.

I should add at this point that using the adjustment pot on the 8080 I gently increased supply to 13.5v DC - a worthwhile and free tweak.

I think - also - it's probably greatly affected by the interface between amp and speakers. Those with less efficient speakers may well find they need the stiffener cap there?

- John

P.S. Just been playing some Grateful Dead through the Amp6 - definately no loss of dynamics or curtailed bass here.

GJF 28th February 2007 09:39 AM

Until fairly recently I'd preferred a bog standard linear psu over the SMPS I'd tried including the Skynets.
Skynet with/without extra caps, it just sounded shrill to these old ears.
I even rebuilt a Skynet with Nichicon Muse and Elna Silmics, different balance of sound but shrillness still there.

Then one day I chanced upon an industrial SMPS rated at 5 amps and tried that expecting to hear pretty much of the same.
How wrong can you be, its absolutely glorious.
Deep firm bass, crystal clear and detailed mid and clear non edgy treble.
Little bit dry sounding but very pleasent on female voices and blues. Driving bass on rock.

Results are consistant across both my Amp 3 and Amp 6 and I find that a very large tank cap is not required to hear the effects of this psu in use.
My Amp 6 now sounds slighly better overall than the Amp 3 and only has 1800uf of extra tank cap on board. The Amp 3 has 18000uf of tank cap.

The downside is that to buy new these SMPS's run out at something like 70 GBP!

Hope this helps.

johnm 28th February 2007 10:00 AM

I noticed the shrillness at first, but attributed that to the burn-in time of the chip? I've had the same thing with all three of my Ta2020 chip amps. They all sounded Ok for an hour or so, then sounded quite harsh for 5 days or so then suddenly come on song.

I guess alot of it is to do with synergy as well, partnering equipmemt etc etc.

Which industrial SMPS did you use by the way?

- J

GJF 28th February 2007 05:16 PM

The model in question is a DPS53 made by Astec, in China of course!

Seems I gave everyone a bum steer with the price;

RS Stock no. 513-1317, 48.00 each.

Note a mains lead is extra.

Which makes them slightly better value but no where near as cheap as the Skynets although with them you need to add the cost of a case, connectors and a load resistor etc, not to mention the time element.

I have noticed that when power is switched off at the mains the Astec remains alive for more than a brief moment suggesting there may be some capacitance inside.
The output lead is fitted with a 2.5 mm plug, centre positive and is screened to boot!

All in all a neat, tidy and good performing SMPS that happens to power my Amps exceedingly well.
Certainly the best psu I've had yet and I now am perfectly happy with how things sound and have no wish to change.

johnm 28th February 2007 07:32 PM

Thanks for the link - I'll have a look on RS for that PSU.

BTW (and slightly off-topic) have you tried changing the polarity of the + and - speaker connections? According to Tripath's datasheet for the TA2020 chip it is an inverting design.

I'm listeing to it (re)inverted today - can't honestly say if I prefer it this way or not - seems to be a little thinner sounding? Perhaps I should just leave it as it was. It's worth a try though as it's free and easy tweak to try out.


- John

Code 2nd March 2007 11:50 AM


Originally posted by johnm

I should add at this point that using the adjustment pot on the 8080 I gently increased supply to 13.5v DC - a worthwhile and free tweak.

is that measured with or without the amp connected?

johnm 2nd March 2007 12:51 PM


indoubt 2nd March 2007 01:05 PM

I use a toshiba smps (laptop) and have a 4700uF panasonic FC cap close to the AMP3.

It sounded better with the cap.

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