[amdan]

I just received a power conditioner - PS Audio PPP (sorry James. I would have liked to get the Torus but there was too much against it - price & outlet type). The 14 B ST hums when plugged into the power conditioner. The manufacturer says that there is probably a little DC going into the amp which is causing the problem.

The hum does NOT trouble me in itself. I can't hear it from the listening position when the music is on. However, I was wondering if the DC into the amp will compromise the amp's performance.

[James Tanner]

I just received a power conditioner - PS Audio PPP (sorry James. I would have liked to get the Torus but there was too much against it - price & outlet type). The 14 B ST hums when plugged into the power conditioner. The manufacturer says that there is probably a little DC going into the amp which is causing the problem.

The hum does NOT trouble me in itself. I can't hear it from the listening position when the music is on. However, I was wondering if the DC into the amp will compromise the amp's performance.

I would assume DC into the amp would be an issue as the amp can pass on the DC to the speaker.
I will check with engineering.

james

[eico1]

I'd suggest you do not want a power conditioner that passes dc to your amp or one that makes your amp hum.

Those are the things the extra component should eliminate.

Besides, dc is dc and hum is hum, so it sounds like PSA is giving you the cust serv run-around!

just another thought...

steve

[James Tanner]

I just received a power conditioner - PS Audio PPP (sorry James. I would have liked to get the Torus but there was too much against it - price & outlet type). The 14 B ST hums when plugged into the power conditioner. The manufacturer says that there is probably a little DC going into the amp which is causing the problem.

The hum does NOT trouble me in itself. I can't hear it from the listening position when the music is on. However, I was wondering if the DC into the amp will compromise the amp's performance.

Hi amdan,

Any particular reason you chose a power regenerator (PSAudio) instead of a power isolation unit?

james

[brucek]

I would assume DC into the amp would be an issue as the amp can pass on the DC to the speaker.

If the hum is a result of an asymmetrical AC line (DC components present), then the noise would be a mechanical one sourced from the 14B's toroidal transformer and wouldn't be the typical sixty cycle hum from the speakers.

Because of the low impedance of toroids (regarding DCR), and the smaller cores compared with conventional El laminate transformers of the same power handling and regulation, they're more susceptible to humming from DC flux offset.

The solution  is usually a DC blocker circuit (not very elegant) or an isolation transformer placed outside the listening area.

My understanding was that Bryston hand rotates every transformer in their power amps during final production to find the quietest operation. Perhaps that's a wives tale. Either way, even a small positional change can quiet a noisy transformer.

If the hum is in fact emitting from the systems speakers, I can assure you it isn't a result of DC on the AC line. The toroid in the 14B would block it completely.

brucek

[James Tanner]

Hi Bruce,

Yes we do rotate the transformers (and adjust the power transformers wiring) in order to attain maximum performance from noise and distortion during final checkout.

It is Thanksgiving in Canada today so I can not ask engineering about what might cause the PS Audio to have DC at it's output. I also agree that an isolation transformer (Torus) would stop any DC. I do not think DC at the power supply input will cause any harm (other than annoyance) to the amplifier but I just want to be sure.


james

[amdan]

I just received a power conditioner - PS Audio PPP (sorry James. I would have liked to get the Torus but there was too much against it - price & outlet type). The 14 B ST hums when plugged into the power conditioner. The manufacturer says that there is probably a little DC going into the amp which is causing the problem.

The hum does NOT trouble me in itself. I can't hear it from the listening position when the music is on. However, I was wondering if the DC into the amp will compromise the amp's performance.

Hi amdan,

Any particular reason you chose a power regenerator (PSAudio) instead of a power isolation unit?

james

Hi James,

In terms of technology the power regeneration story made sense to my layman's mind. I don't understand power isolation. However that did not really matter. If you remember there were many posts here regarding the Torus and I was happy to take your word that it worked and worked well.

In fact, I was keen on getting a Torus and spoke to your Australian distributor about it. Firstly, it was expensive. The unit I was looking at cost about AUD 6000. This was more than I wanted to pay but I would have bought it if it made AUD 6000 worth of difference. However, your distributor did not and would not have a demo model and hence I was not able to find out what sort of difference it would make. This was show stopper #1. The other problem was that the 'universal' outlets used in the Torus. Audiophiles in Australia use American power chords. These power cords would be useless with the Torus. Furthermore, the required power cords (jumper cables) were not even available at the time. This was show stopper #2.

Another point not in favour of the Torus is the lack of isolation between sockets. This wouldn't have been a show stopper but it was a point worth considering.

The PS Audio costs $4500 RRP. I was able to get a great discount which helped heaps but the crucial difference for me was that the distributor lent me a demo to take home and try out. Even though that particular unit was faulty it gave me enough comfort that the unit would make a worthwhile difference. The PS Audio also has American outlets.

I hope the above helps.

[James Tanner]

Hi amdan,

Thanks for the update.

I was aware of the issues with the plugs but as I said earlier USA plugs are not electrically certified for 230 volts so it is a serious offence not to mention a safety hazard.

What I was more interested to know about though was why you did not buy another manufacturers (less expensive) isolation transformer?  Power line regeneration is really not an issue these days with most gear.  Any well designed linear power supply will not have much of an issue with powerline fluctuations and the latest switching power supplies could care less what the voltage is.

I should be able to get back to you tomorrow on the DC issue.

james

[amdan]

Hi James,

The voltage regulation wasn't a big issue in my mind. I thought the regeneration would effectively get rid of distortion. I didn't analyse the options based on technology (I don't understand it) but more on reputation and reviews. On that basis the Torus was my first choice. However, that didn't work out for me.

[James Tanner]

I just received a power conditioner - PS Audio PPP (sorry James. I would have liked to get the Torus but there was too much against it - price & outlet type). The 14 B ST hums when plugged into the power conditioner. The manufacturer says that there is probably a little DC going into the amp which is causing the problem.

The hum does NOT trouble me in itself. I can't hear it from the listening position when the music is on. However, I was wondering if the DC into the amp will compromise the amp's performance.

I would assume DC into the amp would be an issue as the amp can pass on the DC to the speaker.
I will check with engineering.

james

Hi,

OK answer from Bryston engineering:

Bryston's engineers agree the cause of transformer hum could be DC leakage from the power conditioner.  If that's the case, however, it would likely have to be more than a trivial amount of DC leakage.  Bryston amplifiers contain a power-line DC filter that blocks up to 1.2 Volts of DC, so it would need to be even higher, and that would be a considerable amount.
 
Another possibility is relatively severe distortion, (several percent), on the 50Hz waveform from the power conditioner.  In either case, I would suspect a malfunction in the power conditioner, since the obvious purpose in a power conditioner is to reduce problems in the power-line, not increase them.  I suggest having the power conditioner checked for service or possible replacement."


james

[amdan]

James - Thanks very much for checking up on this. I will contact the manufacturer.

[amdan]

James,

Does this condition (humming) affect the quality of sound produced by the 14 B ST? Bear in mind that the hum itself does not bother me.

Thanks,

[James Tanner]

James,

Does this condition (humming) affect the quality of sound produced by the 14 B ST? Bear in mind that the hum itself does not bother me.

Thanks,

Hi amdan,

It should not affect the sound or hurt the amplifier.

james

[amdan]

Thanks. Glad to hear it.