Abucktwoeighty, do you have a Digital Volmeter (DVM)? If so you might want to measure the voltage at the output of the Jolida with the volume turned down. If its anything other than 0volts, you have a problem that should be fixed.
If the preamp employs paper and oil coupling caps, they can sometimes develop electrical leakage, resulting in a slight DC voltage at the output of the preamp. This would cause the behavior you have described. I have no doubt that the insertion of a passive control or an attenuator is degrading the sound; IOW its worth pursuing this. |
This is a follow-up. I received the Rothwell attenuators. I removed the passive volume control and placed the Rothwells in place. There was a one time driver excursion outwards along with a small popping sound. Then all was well. With the passive volume control there is no excursion. I am going to leave the passive volume control in place as this is doing a better job than the Rothwells. |
I'm very happy with the Jolida in the system. I'm waiting for a set of Rothwells to replace the passive volume control. I also bought some different 12ax7's to try out. The ones supplied with the pre-amp roll off the upper end. It's quite a difference having it in the system. Imaging is amazing and the soundstage has widened. Now I just need the correct flavor of tubes and I'll be set.
As far as the problem is concerned, I'm very happy with the current remedy. |
Thanks Al. I can't explain why I missed that in very first sentence. Silly me. |
Unsound, note my earlier statement: Basically, the very high input impedance of the DNA-1 may be bringing out a design issue in the preamp. The Marantz presumably has a much lower input impedance, perhaps 47K or less, which does not bring out the issue. The very extended low frequency bandwidth of the DNA-1 (specified as 0.5 Hz) is presumably also a factor that contributes to bringing out the issue, as explained in Ralph's (Atmasphere's) posts. The problem is with the Jolida, but if there are means by which the Jolida and the DNA-1 can be made work together, and which produce results that 280 finds to be sonically satisfactory, there is no need to replace it. Best regards, -- Al |
Am I the only one that thinks that the problem is with the Jolida? |
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. |
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? |
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. |
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 |
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. |
Another possibility, which would be consistent with the fact that there is no problem when the preamp is used with the Marantz amp, is the scenario described by Atmasphere in his two posts dated 8-3-12 in this thread. Basically, the very high input impedance of the DNA-1 may be bringing out a design issue in the preamp. The Marantz presumably has a much lower input impedance, perhaps 47K or less, which does not bring out the issue. The very extended low frequency bandwidth of the DNA-1 (specified as 0.5 Hz) is presumably also a factor that contributes to bringing out the issue, as explained in Ralph's (Atmasphere's) posts. If that is what is occurring, and I suspect that it is, a readily practicable solution would be to insert a pair of 10 db Rothwell attenuators at the inputs of the DNA-1. That would result in the preamp seeing a load impedance of something like 33K. Doing that would cause you to operate your volume control at settings that are 10 db higher than those you would otherwise be using. But given the relatively high gain and sensitivity of the DNA-1, as noted in the Stereophile measurements that Unsound referred to, I doubt that would be a problem. It might even be beneficial. Best regards, -- Al |
Output caps are leaking DC if they pop when connected to SS amp.
Change them out with high voltage rated ones like mundorf and you will have no problem. |
The McCormack amps input impedance shouldn't be an issue. When Stereophile originally measured the McCormack its input sensitivity was greater than specified, which could be problematic with some tube pres typically high output, but this should typically only reduce the usability range of the volume control.
Just to rule out possible problems I'd try different interconnects (not for flavor, but for integrity). Just a hunch, but I'd hazard a guess that the Jolida is misbehaving. |
Sorry about the double post. I posted this one last night and didn't see it so I figured it wasn't going to be. Anyways...
When the Jolida is connected, it will only extend the drivers out, like they're getting DC. Then there will be a "pop" and this will repeat. I put an old set of speakers from the basement in the system when trying this.
The pre-amp was sent to Jolida where they repaired the voltage regulator and was given a clean bill of health. It was returned to me and after I put it in the system, it did what I described above. I then contacted both Jolida and SM to discuss various remedies and found that what we were doing should have worked just fine. The amp works fine with my other pre-amp, so the amp is working correctly. The Jolida works fine with the old Marantz I have, so it, too, is working correctly, just not compatible with with each other.
As stated above, this all does seem odd. |
When you say it wouldn't work, can you be more specific? I agree with Zd, I would have thought it would "work" with just about anything. Now I can imagine that it might not be an ideal match with this or that preamp, but to not "work" at all seems odd. |
I think I just answered your other post. Basically, I asked you for more info on your system. I see that you provide it here.
The DNA 1 is a pretty straightforward amp. It should work with just about anything out there. If you have a preamp that is not comparable with the DNA, I suggest that you get a different preamp. Its a very popular amp; I had one myself. I tried tube, solid state, passive, balanced, single ended preamps and all worked OK.
Try a different preamp with it just to be sure that there is nothing wrong. Use the pre outs on a cheap receiver, if you have one. Unless something is broken, it should work OK. |
