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Tube pre, SS amp incompatibility, which amp 2 use?

I wanted to see how a tubed pre-amp would sound in my system so I purchased a Jolida Music Envoy pre-amp to mate with my McCormack DNA-1 amplifier. When I put the pre-amp in the system it would not work. After talking to Jolida, where Jerred helped me try various things, we came to the conclusion that they were just not compatible, since the Jolida works just fine with an old Marantz I have. The Jolida has in output impedance of 600 ohms. The McCormack has an input impedance of 100K ohms.

Next I emailed Steve McCormack asking his opinion, and he also gave various reasons for the failure, but after letting him know what was done in an attempt at making them work together, he also stated it may just be a compatibility issue.

Now I would like to get a different amp to try with the Jolida, but am a little weary of purchasing another just to find out that for one reason or another it will not work.

Since this is just to see if I would like what I hear, I don't want to put a lot of money into it. My speakers are 6 ohm Gershman Acoustics Sonograms and are 89db efficient, so I'm looking at an SS amp with good power for less than $1K.
Does anyone know of any amps I can look into that DO work with the Jolida, knowing for sure, that they will be compatible?
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abucktwoeighty's avatar
abucktwoeighty OP
1,079 posts
 
I thank everybody for your input.

Almarg, I do have a CI Audio VPC-1 that I can insert between the units. I'll give that a try to see what happens. I don't believe the output caps are leaking as suggested by Johnsonwu since the pre-amp was just given a going over by Jolida.

I'll post results shortly.
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almarg
9,670 posts
 
It appears that the VPC-1 has a total resistance of 10K. I suspect that the problem will not occur with that in place, which would help to confirm the diagnosis I proposed.

However I suspect that 10K is too low a value to be a permanent solution. Interaction of the 10K load with the rise in the preamp's output impedance that most likely occurs at deep bass frequencies, as a result of the coupling capacitor it probably uses at its output, will probably result in perceptible rolloff of the deep bass.

I don't think that would occur with the approximately 33K input impedance of the 10 db Rothwell attenuator (as measured by me, using a not particularly accurate analog multimeter).

Also, since the Rothwells would be inserted directly into the input jacks of the power amp, with no intervening cable, the possibility of sonic effects resulting from interaction of the VPC-1's output impedance with the capacitance of the cable connecting it to the amp would be eliminated.

Best regards,
-- Al
abucktwoeighty's avatar
abucktwoeighty OP
1,079 posts
 
Almarg, your diagnosis was spot-on. Inserting the passive volume control between the pre and the amp fixed the problem. You also saved me from spending money on an amplifier I didn't need, and for that I thank you so much.
I'll be sure to let Steve and Jerred know about this. I'm so pleased. Thanks again.
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atmasphere
11,784 posts
 
Abucktwoeighty There may be other ways to sort this out too. How are your power cords set up? Are they both running off of the same power strip?
abucktwoeighty's avatar
abucktwoeighty OP
1,079 posts
 
Yes, the pre-amp and the amp are plugged into a Monster HTS5000 Power Center. I found there is less noise when I have the amp plugged into it instead of directly into an outlet.
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