Author Topic: Is there a simple way to fix impedance mismatch in pre/power?  (Read 9145 times)

Offline Doggie Howser

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So I like the Ayon CD5S.

And I like the Focal Solo 6 Be

But I encountered what I suspected was an impedance mismatch issue. There's like static in the sound. Very high hiss. But it's oddly enough an intermittent problem and wasn't obvious at first.

So I used the Bel Canto Pre3 in between and that fixed the problem.

Ayon CD5S specs:
Output impedance  Balanced-XLR
 ~  300 Ohms

Focal Solo6Be
Type/Impedance: symmetrical/10 kOhms

Is it likely that impedance mismatch to be the cause of the issue?

I don't really want another preamp in the loop. Is there a simple in-line solution to fix this?
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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #1 on: January 26, 2012, 14:37 »
Hmm.. looking at the Bel Canto Pre3 specs:
Input impedance: 20kOhms balanced
Output impedance: 500 Ohms Single Ended, 200 Ohms Balanced

Is that enough?
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Offline AndrewC

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #2 on: January 26, 2012, 17:21 »
IME impedance mismatch will manifest itself with the overall sound quality, like a missing bottom or rolled off top etc. It wouldn't be intermitten static (is it truly intermitten, or always as the same point in a musical piece?). The CD5S' tube output has no buffer stage, and that bass/midrange "150W rms, BASH® technology" on the Focal sounds freaky if you ask me ;D....

You tried tweaking the Focal's input sensitivity controls?
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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #3 on: January 26, 2012, 17:50 »
I've encountered this on and off with different tube preamps.

When I used the Schiit Lyr as a preamp to the Quad 606 power amp, I also encountered the same problem. Sam symptoms. Switching the Lyr out for a W4S DAC2 again fixed the problem.

The Focal uses a BASH amp for the woofer, but a Class AB for the tweeter. Overall, no complaints with the SQ.

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Offline AndrewC

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #4 on: January 26, 2012, 18:01 »
The only time I've encountered something similar in the past was when my VTL7.5 Pre was connected to my Kharma Class D monoblocks via MIT Oracle speaker cables... intermitten screeching. Changing to straight copper speaker cables solved the problem.... the Class D Amp didn't like the zobel network for whatever reason or something.

I'm guessing similarly in your case, it's probably not an impedance issue per se...
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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #5 on: January 26, 2012, 18:03 »
Nothing fancy. Just some Audioquest shielded interconnects.

No screeching. Just a very high hiss with no signals playing and when music is playing, it's like there's radio static overlaid.
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Offline pcking

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #6 on: January 26, 2012, 19:25 »
R u using Low or High Output setting on your CD5S ?

Don't think your problem is due to impedance mismatch.
« Last Edit: January 26, 2012, 19:26 by pcking »
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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #7 on: January 26, 2012, 19:29 »
I have tried both. Both have the same problem.

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Offline jimi

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #8 on: January 26, 2012, 20:47 »
My power amp have a low input impedance so a relative mismatch is easily done- but it's never resulted in hiss- a lethargic low on dynamics sound seems most prevalent. 

If the hiss is equal from both spkrs then it's likely to do with a gain mismatch and high sensitivity spkrs. So perhaps the CD5S gain alone is more than CD5s+pre3 gain?

If the hiss is not equal then there's something really wrong.

Though hiss is not supposed to be cable related my spkrs go dead quiet if I'm using balanced, even if i crank up the volume when no music is playing with my ear next to the tweeter (no helpful to u as ur already eliminated the cables).

Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #9 on: January 26, 2012, 21:34 »
I have used high and low gain, phase at 0 and 180. Both exhibited this problem.

I've also encountered something similar when I used another tube preamp (Schitt Lyr) with a Quad 606 power amp.

It's not a soft hiss, but something like radio static. Weird

Using BCD Pre in between fixes this.
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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #10 on: January 26, 2012, 21:43 »
Hmmm I was using the Quad 12L actives with the Ayon before this with no issue. And checking the specs, the input impedance is ALSO 10kohms.

I was using the Ayon CD5S as a preamp direct to power amps in my media room as well as a full output CDP to my preamp. The difference that I can tell is that I was using a PurePower to output 230V to the Ayon.

In my study the Ayon is plugged to an Essential Sound Reference distributor to the wall. Would that account for this problem?
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Offline vajrasattvasg

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #11 on: January 26, 2012, 23:26 »
Hmmm I was using the Quad 12L actives with the Ayon before this with no issue. And checking the specs, the input impedance is ALSO 10kohms.

I was using the Ayon CD5S as a preamp direct to power amps in my media room as well as a full output CDP to my preamp. The difference that I can tell is that I was using a PurePower to output 230V to the Ayon.

In my study the Ayon is plugged to an Essential Sound Reference distributor to the wall. Would that account for this problem?


two quick tests..

dont think its an impedance problem, you can drop in a passive pre-amp (just a potentiometer) like 50k or something in between just for experimental sake, that should drop the load seen by the cdp and see if the problem goes away

are the quad 12L grounded/earthed in anyway? i had a high pitch problem that existed due to poor grounding in the signal area.

maybe can try putting in the belcanto pre again, but use a 2 pin adapter on the powercord (so that any possible earth connection is not available) and see if problem persists. then can verify if its an "earth" problem or not.

else substitute a generic power bar in place of the previous distributor is also another experiment
maybe the human ear isn't good enough. we need measurements, figures, numbers, calculations to tell and convince us what good sound is. or do we have to satisfy an unspoken insecurity??

Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #12 on: January 26, 2012, 23:30 »
Ayon direct to Quad actives in SG no problem.

Ayon direct to Bel Canto REF1000M in Aus with PurePower no problem.

Ayon direct to Focal actives in Australia with 250-260V AC to ESP distributor. Problem.

Ayon line level to Bel Canto Pre to Focal actives in Australia wih 250-260V AC to ESP distributor. No problem.

See what I mean?

Cables are Audioquest active shielded XLRs.
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Offline vajrasattvasg

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #13 on: January 26, 2012, 23:53 »
Ayon direct to Quad actives in SG no problem.

Ayon direct to Bel Canto REF1000M in Aus with PurePower no problem.

Ayon direct to Focal actives in Australia with 250-260V AC to ESP distributor. Problem.

Ayon line level to Bel Canto Pre to Focal actives in Australia wih 250-260V AC to ESP distributor. No problem.

See what I mean?

Cables are Audioquest active shielded XLRs.

tricky. but i just have a hunch that it probably lies in the ground/earth, i.e. that the bel canto pre3 offers a "drainage" point  for the shielding on the XLR cabling.

not too sure how to explain it, but this site offers some possibilities http://www.rane.com/note110.html
maybe the human ear isn't good enough. we need measurements, figures, numbers, calculations to tell and convince us what good sound is. or do we have to satisfy an unspoken insecurity??

Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #14 on: January 27, 2012, 00:26 »
Weird. Maybe I'll bring the bring the SA conditioners next to test.
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Offline AndrewC

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #15 on: January 27, 2012, 18:21 »
Ayon direct to Quad actives in SG no problem.

Ayon direct to Bel Canto REF1000M in Aus with PurePower no problem.

Ayon direct to Focal actives in Australia with 250-260V AC to ESP distributor. Problem.

Ayon line level to Bel Canto Pre to Focal actives in Australia wih 250-260V AC to ESP distributor. No problem.

See what I mean?

Cables are Audioquest active shielded XLRs.

I still think it's something dodgy with your Solo 6 Be…  Took a while to figure out what BASH® technology was exactly. Coincidently, google ultimately pointed to the same site that vajrasattvasg pointed to; http://www.rane.com/par-b.html

BASH is Bridged Amplifier/Switching Hybrid; a standard Class AB amp but with Pulse-width modulated power-rails, apparently an OEM technology from (now defunct?) Indigo Manufacturing Inc. The Solo 6 BE probably uses something like the STA5150 BASH chip…

You have to wonder how sensitive this thing is to Power supply fluctuations and grounding issues… Try lifting the ground on your Solo 6 Be and see what happens… (Standard disclaimer: DON'T GET ELECTROCUTED or some sh*t ;D)
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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #16 on: January 27, 2012, 19:04 »
oookay. Is there a less intrusive way of lifting the ground?

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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #17 on: January 27, 2012, 19:08 »
Something like the Entreq box they were talking about in another thread?

http://www.xtremeplace.com/yabbse/index.php?topic=107061.msg744796#msg744796

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Offline vajrasattvasg

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #18 on: January 27, 2012, 19:31 »
oookay. Is there a less intrusive way of lifting the ground?



least intrusive is just a 3pin to 2 pin adapter on the powercord of the solo6 perhaps
maybe the human ear isn't good enough. we need measurements, figures, numbers, calculations to tell and convince us what good sound is. or do we have to satisfy an unspoken insecurity??

Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #19 on: January 27, 2012, 19:43 »
No excuse to buy the Entreq then :)
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Offline jimi

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #20 on: January 27, 2012, 22:09 »
No excuse to buy the Entreq then :)

You can still buy one... For me ;)

Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #21 on: February 11, 2012, 08:28 »
OK an update:

The Focal Solo6Be does seem noisier than say the Quad 12L actives that I use in another room. There's a bit of a hiss when my ears are about an inch from the tweeter when nothing's hooked up. More than the Quads but I'd say not objectionable when I sit about 1.5m away.

But this isn't the problem I am facing when the Focals and Ayon are hooked up directly. What I get is like FM static noise/buzz that's quite loud and it goes louder and softer... even when no music is playing. That's noticeable even when I am 1.5m away. Maybe I ought to take a video.

Anyway, I decided to put the SA RLS240 to see if that fixed the problem.

Nope. Noise/white noise buzz seemed softer than before but no dice.

Then I moved the gear to the main living room and experimented the Ayon and the Focal with other pieces of gear to see if I could find the source of the problem.

First up: same combo as before, i.e. Ayon into Focals but via the PurePower regenerator. Seemed a bit softer again but still discernible from the listening position.

Next, Ayon direct to the Bel Canto REF1000Ms driving my main speakers. No issue. Dead quiet when I paused the CD.

Then it was the XDS1 to the ARC Reference 5SE to the Focals. Not dead quiet but same as the Focals without anything plugged in.

So it looks like somehow the Ayon and the Focals just don't play nice.

Dammit.

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Offline Quest

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #22 on: February 11, 2012, 08:58 »
First up: same combo as before, i.e. Ayon into Focals but via the PurePower regenerator. Seemed a bit softer again but still discernible from the listening position.
Can you try disconnecting the purepower from the wall at this stage to see if the sound still prevails?
i assume both are connected to purepower, and also that nothing else is connected to the ayon.
« Last Edit: February 11, 2012, 09:00 by Quest »

Offline Doggie Howser

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Is there a simple way to fix impedance mismatch in pre/power?
« Reply #23 on: February 11, 2012, 09:11 »
Yeah the Ayon is plugged directly to the Focals powered by PP for all 3 devices.

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Offline Quest

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #24 on: February 11, 2012, 09:21 »
Yeah the Ayon is plugged directly to the Focals powered by PP for all 3 devices.
can try disconnecting purepower from wall (run only on battery) for a short while, to see if any sound?

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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #26 on: February 25, 2012, 12:24 »
OK just an update.

I got a PM from another Ayon CD5S owner and he's had the same problem. He's using the Ayon CD5S direct to his Modwright power amp (KWA150).

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Offline Doggie Howser

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Is there a simple way to fix impedance mismatch in pre/power?
« Reply #27 on: February 26, 2012, 20:38 »
This is apparently in the Ayon manual.

---------- Forwarded message ----------
> Below is a note from the CD-5s owner's manual when you connect the CD-5s
> directly via XLR to a solid state amp.
>
>
> Exceptions for the „direct“ connection of the CD-Player with solid-state
> power amplifiers or active loudspeakers:
>   
> There are some solid-state power amplifiers or active loudspeakers, with
> which you rather should not use the symmetrical connection, or where, as the
> case may be, a loud hum modulation, high-frequency interference signals or a
> so-called “oscillation” can occur.
>
> The Ayon 6H30-tube output stage is designed extremely puristical and
> “short”; i.e. absolutely no negative feedback, no correcting or compensating
> devices and no filter in the circuit. (See also the note about the special
> properties of the 6H30 tube).
> But “pure tube” design also means a big and difficult challenge in
> realization for our engineers; and also e.g. we would respect some
> non-important measuring data to a much lesser extent. All these puristical
> sound-techniques require that the electrical interface parameters of the
> subsequent power amplifiers should match the ones of the CD-Player in
> accordance with the standards.
>
> Typically the input impedance of power amplifiers is 47k or above. However,
> there are solid-state power amplifiers with a lower value (down to only
> 1.8k). I.e., there is a significant matching problem between the CD-Player
> and the solid-state power amplifier (impedance, capacity, phase rotation
> etc.; in special cases there may also be a problem of a difference in the
> grounding-potential of the connection). Furthermore some solid-state power
> amplifiers possess not too big an input override rigidity (but paradoxically
> in addition a high input sensitivity); therefore additionally they quickly
> are overcharged by the “strong puristic” symmetrical output stage of the
> CD-Player.
>
> Therefore, in case of symmetrical input values below 47k we strongly
> recommend to use the asymmetric RCA/cinch connection or a classic separate
> preamplifier.
>
> Note: in case you really wish to use the symmetric “direct” connection, we
> can adapt the CD-Player to the special electric properties (power amplifier
> or active speaker) to a large extent at your costs. Please note that then
> the CD-Player can only be operated at optimal conditions with this
> particular solid-state power amplifier or another with very similar
> electrical input parameters.
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Offline jigster

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #28 on: February 27, 2012, 09:54 »
I had the same problem with my horn speakers with an Accuphase integrated but not with my set amp. I realised that it was interference coming from my computer. No noise when my pc is off. The pc was about 1 metre away from the amp & in-between the speakers

Offline Doggie Howser

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Is there a simple way to fix impedance mismatch in pre/power?
« Reply #29 on: February 27, 2012, 09:59 »
Anyway. The issue had nothing to do with PCs. As Ayon explained, the Ayon doesn't use negative feedback and it seems like the impedance mismatch in combination causes this problem on balanced connections. Using RCA fixes the problem.

Hope I have better luck with a Plinius that has a 47kOhm input impedance.
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Offline Leicachamp

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #30 on: March 23, 2012, 06:19 »
Hey Doggie

This is Petng. Did you give up on the Ayon completely? FYI in my system going to the preamp, I much preferred the RCA outs to the XLR. Never could make the Ayon work into the modwright even with RCA . Sounded ok but not as good as going through a pre.

Offline Doggie Howser

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Is there a simple way to fix impedance mismatch in pre/power?
« Reply #31 on: March 23, 2012, 10:26 »
Which preamp are you using?

I am currently out of the country so have not had a chance to test the changes yet.

I do plan on using the Bel Canto combo (DAC3.5VB mkII, CD2, VBS, Pre3) with the Focal and use the Ayon with a new setup partnering with a Plinius power amp that has 47kOhm input impedance.
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Offline Leicachamp

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Offline Doggie Howser

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #33 on: March 23, 2012, 13:19 »
The Prelude looks nice.

I suspect the impedance mismatch may still be an issue even with RCA direct.
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Offline vajrasattvasg

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Re: Is there a simple way to fix impedance mismatch in pre/power?
« Reply #34 on: April 14, 2012, 01:35 »
is this a hum solution with balanced setups??

http://www.lundahl.se/probsolv.html
maybe the human ear isn't good enough. we need measurements, figures, numbers, calculations to tell and convince us what good sound is. or do we have to satisfy an unspoken insecurity??

 

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