Trying to eliminate noise totally

[manisandher]

A quick update...

Right, just tried the Sanders Magtech and the Sauermann monos, and...

Run off house mains

Sanders power supply dead quiet (low bias class AB amp, with little load at idle). There's only the slightest bit of hiss coming from the horns, and absolutely no other noise of any character - with ear 1m or so from horn. My feeling is that a little hiss from 115dB horns at 1m is acceptable. (Perhaps Peter's/Bert's horns have this too, but they're both just too old to hear it!) RCA or XLR makes no difference.

Sauermann supply has slight hum when ear pressed against PS (class A mono amps, each PS drawing ~250W at idle). A little more hiss through speakers than Sanders amp, but maybe this is down to perhaps extra gain (not sure).

Run off dedicated hifi circuit

Exactly as above. Absolutely no difference whatsoever! Phew!

*************************

So, there maybe something up with my new amp and it'll be going back to its maker, Anthony Matthews, tomorrow. I say 'new' but it's actually 9 years old now. Apparently, it's been sitting in storage for most of these 9 years and perhaps some things are just resettling on its re-exposure to prolonged active service. Anthony will give it a thorough going over and we'll proceed from there (see next post).

Mani.

[manisandher]

I remember reading superb reviews of the Soul amplifier in HiFi+ a few years ago. Have to say I really liked the ideas behind the amp design, IIRC it has number of very high performance power supplies for vairious roles in the amp.

I really, really hope Anthony can find something amiss and get the Soul working acceptably with my horns. I have to say that hearing the Soul in my system, even with the noise issue (which quite frankly wouldn't be an issue at all on 99.9% of systems) I don't want to have any other amp in my system. Not the Sauermann, not the BD-Design, not the Sanders... OK, maybe the Berning if I had to (it comes pretty close). And this is absolutely no judgement on these other amps - they're all great. But to my ears, they don't have the 'magic' that the Soul (and to a lesser degree the Berning) has. For me, at least, it's going to be single-ended valve amps and horn speakers for ever from now on. If the Soul comes good, it may be a keeper for life. As for speakers... I'll definitely be buying a new pair next year.

Nick, if the Soul does come back 'fixed' (I hope and pray) you're welcome to take a listen. I think it'll be well worth your while. But maybe hold off until I get the new speakers sorted out. There are currently three on my radar - Bert's new Orelinos, the Tune Animas and a bespoke pair of horns (which I'd rather not disclose anything about right now). I'm taking a listen to the Animas tomorrow and have really high hopes - they're exactly the sort of design that sits well with me.

Mani.

[manisandher]

Probably all amps are dead silent with shorted inputs (nothing but the speakers connected) or do the powertransformers hum?

This PSU humming could very well be the cause of the groundloop noise since the left and right channels are likely to be connected together in the vicinity of the magnetic fields (either from the x-former or psu caps).

Yep, this may well be the issue. The thing is though that with the Berning there's also a similar noise profile coming from the speakers.. but of course no audible PSU noise, as it's an SMPS. Maybe they're two totally unrelated issues that just manifest themselves in similar symptoms?

Is your main rigs ring circuit braker connection ok?

Hmmm, I think so. If it weren't, wouldn't I expect more issues with my other big PSU amps like the Sauermanns? (Although of course these have totally separate PSUs.)

Mani.

[Scroobius]

Hey Mani - just managed to get a quiet few moments this morning to read about the Soul amp. I had not come across it before and I have to say it looks very interesting indeed. I hope the noise problem gets sorted I would be very interested to hear it sometime.

Cheers

Paul

[PeterSt]

Hi Mani,

In the other topic - the one where you put up a drawing from your mains situation and earthing - I asked you to measure the DC offset of (by now whatever) ring. I don't think you understood that (because as far as I am concerned I did not see you do that, although you sure measured "something".

Notice that because of your transformer situation you have "created" ground there, which btw should be absolute zero, but maybe is not. So, with this in mind, hold the one ring against the other for its PE. Use the one for reference against the other (which is which does not matter). At first you undoubtedly should see something, meaning : when devices are connected and on power. Or the other way around : when nothing is connected on either ring, you should see no offset. But if you do, your transformers do not create an absolute zero. Well, assumed you measure an earth pin situation against a transformer situation. The earth pin should show zero in "absolute" sense anyway. Remember, when nothing is connected.

One other thing not so obvious (but I think I mentioned that before too) : maybe switch off the BD30 amp in your Swings. This, with the notice that these speakers just emerged before I came up with my crazy ideas that such speakers - even with their 115dB - should be totally silent, while at that time nothing was silent in my own room, nor Bert's. It is about the latter of course, and how the BD30 performs or influences. We just didn't know and thus check at the time (which for Bert and me were times with a TVC passive preamp which actually produces unacceptable noise (at full volume).
So, just a thought on this latter.

Regards,
Peter

[PeterSt]

One more thing but probably worth nothing much :

I have been looking at the specs of your latest new/old amplifier, but I was not impressed by anything but the fairly good (commercial) outlay of the "design". Well, maybe I could have written it, because in the end it says nothing much but good spirit from the designer with further no guarantee. Example : Today's amplifiers quote 'better than 0.3% THD" (I do this by heart now, maybe it was even 3%). This as an indirect reference to the sh*t out there back at the time, while NO specs are presented from the amp itself. Strange ...
The only thing which kept me up was the "in the microvolts" noise. Still it slipped my mind that this can also be 900uV, right ? If so, that's 42dB more noise than your NOS1 shows (7-8uV).
Notice that I made up the 900uV ad it can well be less, but this happens when the specs concerned just are not there (plus my notice that a heading "Specs" for sure is there).

Of course I don't want to debunk you precious new child, but I thought a small warning was in place. It is by now not the most modern, not saying that it can't be good. But I do say that while we today try to utilize the best SQ from the lowest noise, this design doesn't tell anywhere that it suits that.
Of course I heard you say that without interlinks it is dead quiet, but that doesn't tell all. Example : I create my own ground reference which is way off (what about a few Volts). Without connection it can be "inherently" quiet. But now connect it to something with a normal 0V reference and your interlinks will sparkle. See ?

Another serious hint : please don't like sound of which it is clear to you that it's driven by noise. You will be lost forever.
Oh, of course you are allowed to like it (forever) but now don't try to remove that noise. I mean, I hope it is clear to you that this noise "makes" the sound. So, remove that and you will put the amp to eBay again (the charme of it will be gone).

Still hope this helps and that you won't shoot me !
Peter

[PeterSt]

I have another hopefully more constructive tip, but it is a (very) long shot (and doesn't fit much in the complete picture, but alas) :

The other day I ran (pretty sure it was by private mail) into another person who couldn't solve his hum/noise;
In the end he solved that by replacing the tubes (don't ask me whether recitifiers or main).

I don't know how this works but I have the hunch that Coen will be able to work out something about this. Anyway for me it will be interesting to learn how old(er) tubes can imply something like a groundloop (which sure is how it came to me in that particular stuation). Is something half-shortcutting or so ?

Peter

[CoenP]

Could very well be.

Tube noise problems are usually related to emmission and oscillation. The latter can couple into any suitable wire and cause hiss or pfff into a circuit.

I also had AM radio in my circuit once. This was the result of a breadboard layout (acting as antenna) and dirty tube pins/socket that act as a rectifier. Connecting -unshielded and ungrounded wires to an amp is like introducing antennas feeding the circuit.

Especially triodes with their inherent feedback and large grid capacitances are prone to oscillation (in fact many triodes are designed for hf oscillation pruposes). This varies with age, contact condition, circuitlayout etc. No simple answer available.

Regards, Coen

[manisandher]

Of course I don't want to debunk you precious new child, but I thought a small warning was in place. It is by now not the most modern, not saying that it can't be good. But I do say that while we today try to utilize the best SQ from the lowest noise, this design doesn't tell anywhere that it suits that.

Hey Peter, debunk away!

Another serious hint : please don't like sound of which it is clear to you that it's driven by noise. You will be lost forever.
Oh, of course you are allowed to like it (forever) but now don't try to remove that noise. I mean, I hope it is clear to you that this noise "makes" the sound. So, remove that and you will put the amp to eBay again (the charme of it will be gone).

I totally accept this. There is a certain 'characteristic sound' to all the single-ended amps (valve and solid-state) that I've owned - a deep & resonating bass, a sweet, if somewhat recessed, top end and overall a very laid-back sound. Maybe my calling this 'magic' is a bit OTT. But certainly, they sound very different to regular push-pull amps. Is this down to noise? Maybe. In which case, the noise has a nice effect on the sound.

BUT... there's no way I would be happy with this. I want a nice, natural sound WITHOUT noise. To this end, the Soul has gone back to its creator. He will have a look at it. If he can reduce the noise significantly, I'll take it back. If not, he'll return my money and we'll move on.

Thanks for the advice Peter... as always.

Mani.

[manisandher]

No simple answer available.

Thanks for your thoughts Coen.

It presents a bit of a dilemma I think. Single-ended valve amps tend to be low-powered, so need high efficiency speakers. But these are ruthless with noise, as I'm finding. So the only way to go is to switch to push-pull... which kind of defeats the purpose IMO.

Mani.

[Gerard]

he'll return my money.

I know who  you again. 

[manisandher]

I'm not sure I know who you mean Gerard. I know my wife would be interested though...

Mani

[manisandher]

I'm trying to eliminate the noise 'totally'. But how totally is 'totally'?

I've got a 1KHz track recorded at 0dB FS. With the Sauermann monos I can still hear this track over the amp's (white) noise with XX set to -120dB! OK, that's with my ears right next to the 115dB horn.

So, are the Sauermann monos quiet enough, or do I need to work on getting their noise down further???

Mani.

[AlainGr]

he'll return my money.

I know who  you again. 

Hi Gerard,

It's been a long time !

Alain

[Gerard]

he'll return my money.

I know who  you again. 

Hi Gerard,

It's been a long time !

Alain

@ Mani

my wife is ecstatic

 

@ Alain You are right.... Sorry...