[GT Audio Works]

Latest news is Melody is still making Mystere products.

As to the back order, I didn't ask since it's none of my business.

I sent them 2 emails..no response yet

[Hugh]

Correction.
30K Ohm is RCA's.

Just got the answer.
It is 30K Ohm.

[shahed]

Correction.
30K Ohm is RCA's.

Thats a lot! If the amp has to have 20X more input impedance than the preamp (going by the general guideline), my amp needs to have 600K input impedance.

[rollo]

Greg if I were you I would get my money back. Just too long a wait IMO. The Dodd pre  and the amps you heard were quite impressive with your speakers. You can borrow the Dodd and see how it goes with the Bryston. I would suggest a Melody pre to try as well. Oh Hugh help the man out.
   Try all you can. No matter what preamp you choose the Amp IMO is the culprit. I think you are barking up the wrong tree.


charles
   
     

[nickd]

I don't think the "20x input impedance rule" is a correct guideline. Impedance matching is relatively new to audio but is a reference connection in a few of the ultra high end company's. Krell, PBN and Dartzeel all use impedance matched connections from pre to amp with matching cables.

The preamp just has to have the current capability to drive the amplifier load. the latest thoughts are that reflections come back from a load resistance that is too high and cause audible distortions. The standard for pro gear is 600 ohms balanced. If the Mystere will drive a 30k load or something close I would think you should look for an amp with a regular 47K input impedance on the RCA jack (or something close to that).

I auditioned a Mystere integrated a couple of years back at home. To say I was impressed would be an understatement. It sounded amazing! I might be concerned about service if I were buying one however. Imports with limited distribution and no factory support have always been a problem in the US.

[Hugh]

That's RCA's.
I sent another email to ask about XLR's.

Thats a lot! If the amp has to have 20X more input impedance than the preamp (going by the general guideline), my amp needs to have 600K input impedance.

[Hugh]

Greg,

Did you order from the US distributor or...?

We can talk offline if you prefer and I'll do all I can to help.

I sent them 2 emails..no response yet

[Hugh]

I'll try my best Charles.

Greg if I were you I would get my money back. Just too long a wait IMO. The Dodd pre  and the amps you heard were quite impressive with your speakers. You can borrow the Dodd and see how it goes with the Bryston. I would suggest a Melody pre to try as well. Oh Hugh help the man out.
   Try all you can. No matter what preamp you choose the Amp IMO is the culprit. I think you are barking up the wrong tree.


charles
   
   

[Gopher]

I would suggest a Melody pre to try as well. Oh Hugh help the man out.

The price points are different, but it doesn't seem like that is relevant due to the fact that the Mystere CA21 is NOT being delivered on, so I second this suggestion.  The Pure Black 101 is sublime!  Your tube budget for it would probably be very similar too as it isn't really necessary to roll the 101D tubes...  I recommend a Shuguang 274B preferred series tube (~$25) for the 5u4 position.

[roscoeiii]

the latest thoughts are that reflections come back from a load resistance that is too high and cause audible distortions.

Can you post a link to these "latest thoughts"?

I have seen it recommended again and again (and by forum members whose knowledge I very much respect) that an amp have an input impedance at least 10x the output impedance of the preamp, across the entire audio spectrum. The rec of 20x is made just to be safe, especially since amp manufacturers do not often provide graphs of input impedance vs frequency.

Anyway, that preamp's output impedance of 30k via RCA would give me pause. Using either the 10x or 20x rule of thumb would exclude a number of amps, including my Rogue Stereo 90 (200k input impedance). 

[Hugh]

Just got a response back from Melody.
XLR's is 600 Ohms.
Hope this helps.

Thats a lot! If the amp has to have 20X more input impedance than the preamp (going by the general guideline), my amp needs to have 600K input impedance.

[Berto]

I strongly doubt the Mystere is 30k on the RCA. A buddy of mine owned one and it mated well with Conrad Johnson amp that was 100k and it mated fine. 600 for XLR is industry standard and I bet the RCA impedance is also in line with real world specs.

[roscoeiii]

I strongly doubt the Mystere is 30k on the RCA. A buddy of mine owned one and it mated well with Conrad Johnson amp that was 100k and it mated fine. 600 for XLR is industry standard and I bet the RCA impedance is also in line with real world specs.

Yeah, that does seem mighty high.

[Berto]

Specs from a USA dealers site:

Specifications:
Freq. Response: 8Hz - 200kHz @ 47k Ohms
Noise: 104dB A-weighted
Gain: 19dB
Distortion: 0.05% @ 100mV, 0.12% @ 1V
Input Impedance: 150k Ohms
Output Impedance: 592 Ohms
Inputs: 4 pair RCA
Outputs: 1 pair RCA
Tube Compliment: 4 - 6SN7 & 1 - 5AR4
Weight: 45 lb (20 kg)
Dimensions: 16.9" x 7.9" x 16.4" (wxhxd

[nickd]

http://www.breem.nl/fldtechniek/pgtransmlin.htm

The link takes you to an on going debate regarding impedance matching. the discussion here is related to standard audio cables and terminations. I could not find the original 2001 Stereophile article.

Herve Deletraz authored the first Stereophile article in November 2001 with his thoughts. Peter Noerbaek was designing along the same lines with his balanced 75 ohm impedance matching circut. Krell (Dan Dagostino and team) was also developing their CAST system around the same time.

I have heard the PBN demo where he switches from $10,000 cables to the Impedance matched circut. The difference is always noticeable, regardless of cable design, cost or brand.

System balancing is a bit of a black art. I think a lot of things like impedance mismatch can affect the system synergy. Just my $.02

[Hugh]

Agreed 100%.

Synergy is the key.

System balancing is a bit of a black art. I think a lot of things like impedance mismatch can affect the system synergy. Just my $.02

[roscoeiii]

http://www.breem.nl/fldtechniek/pgtransmlin.htm



System balancing is a bit of a black art. I think a lot of things like impedance mismatch can affect the system synergy. Just my $.02

Unless I am missing something, this seems to be only about cable-related impedance, as opposed to components' input and output impedances. It is the input and output impedances that need to be attended to for proper component matching. Synergy can be a bit of a black art, but potential input and output impedance matching problems are an easy to spot potential synergy problem, since those specs are frequently given.

One reason that active preamps and buffer-based passive preamps (and maybe transformer based too?) contribute to better sound is that they often deliver lower impedance output than a source provides. Nelson Pass's decription of his B1 buffer covers this nicely on "Side A" (And who am I to argue with Nelson Pass?):

http://www.enjoythemusic.com/diy/0708/first_watt_b1_preamplifier.htm

[shahed]

I think this is a common sense to have high ratio of amp input impedance to preamp output impedance to be beneficial (or at least not a bottleneck as oppose to low ratio). All the readings I've done regarding this topic, give me the impression that this is not a black art rather a clear cut fact.

I had a Aesthetix Callypso preamp which have a high output impedance ( the actual impedance was way higher than manufactured published spec esp at low frequency). My amp input impedance is around 20K ohm. And there was definitely a bass roll off. No question about. A vincet SA-T8 preamp sounded way better in my system (which has a low output impedance).

And also, usually, a single number of output/input impedance is not nearly good enough. Manufacturer should specify the max output impedance and min input impedance as they vary along the frequency.

I'm excerpting from John Atkinsons measurement of Cary SLP-05 from stereophile as an example:

"The SLP 05's output impedance is specified as a usefully low 400 ohms. However, I got significantly higher values for the unbalanced output of 1500–1600 ohms in the midrange and treble, rising to 3400 ohms at 20Hz, with similar if slightly lower figures for the balanced output. The Cary preamp needs to be used with power amplifiers having input impedances of 10k ohms or greater if the bass is not to sound a little lean."

http://www.stereophile.com/content/cary-audio-design-slp-05-preamplifier-measurements

[woofersus]

I don't suppose it's possible Melody gave you max impedance instead of average on the RCA's?  I believe that's how the original question to us was phrased.  30kohms does seem high, but we've paired it with a bunch of different amps and never found it to be finicky.  Also, when Ron Nagle reviewed it for Enjoy The Music he paired it with a Roger Sanders ESL power amp, which according to their website has an input impedance of only 50kohms, and he gushed about the sound.

[Gopher]

They have been on back order for quite a while.
I have been waiting since January.

I don't have any affiliation with the seller, but if it were me I would cancel that order--6 months is way too long and just pick this one up:  http://app.audiogon.com/listings/tube-mystere-ca21-tube-preamp-with-tas-recommended-tubes-2013-06-07-preamplifiers-92840-garden-grove-ca