Tube phono preamp distortion - help


Hi everyone,

Having some very frustrating distortion issues with my new Jolida JD9 Mk2, and I have tried everything I can think of. My rig was working without issue with the following setup:

Project Debut Carbon w/Otorfon 3M Blue
Vincent PHO-8 Phono Stage
Simaudio i-1 integrated
Tekton M-Lore speakers
Silnote IC, phono cable, and power cables
Clear Day double shotgun speaker cables

So, the only change I made was to remove the Vincent and hook up the Jolida. The Jolida has several settings that need to be chosen:

A. Three voltage gain switches: I set this to low (for MM cartridge, as recommended). The medium setting was unlistenable, and I didn't bother trying the high setting.

B. Eight impedance switches (100, 300, 1000, 47000 ohm, and 47, ,100, 150, and 220 Pico Fared). I set this at the recommended 47k ohm for the Otorfon Blue. I tried the other settings out of curiosity, but none sounded as good at the recommended setting.

C. Two RCA outs: High (1.8 volts for an integrated or line stage) and low (500 millivolts for high gain preamp separates). I connected from the High out to my Simaudio integrated.

This combination of settings is by far the best sounding. However, I get terrible distortion in the higher frequency ranges - upper keys on the piano, female vocals, etc. The low and midrange are fantastic, but the higher range just degrades into a static-like warbling sound (as if it's being overdriven) in both channels with each rise in a singer's voice or striking of the piano keys. It happens on every record and in both channels. As soon as I put my Vincent phono stage back in, everything returns to normal.

I have tried everything I can think of:

-Placing the phono amp further away from my gear
-Trying different inputs on the Simaudio integrated
-Using every possible combination of the switch settings and the RCA outs.

I'm relatively new to vinyl, and I see why some people say it's too much trouble. However, I'd like to find a way to make this work.

I'm open to any suggestions - ready to experiment! Thanks for any ideas!

Best,
Scott
smrex13
Are the right tubes installed?
Here's 2 things you should try.

"C. Two RCA outs: High (1.8 volts for an integrated or line stage) and low (500 millivolts for high gain preamp separates). I connected from the High out to my Simaudio integrated."

First, try the low setting instead of the high. If that doesn't fix the problem, try listening with headphones. I believe your Sim has a headphone jack. If that sounds OK, then you're issue is most likely a mismatch between your phono stage and your speakers. To confirm this, try some speakers that are less efficient than your current ones. If that's what the problem turns out to be, you'll either need to get new speakers or a new phono preamp.
Looking at specs, the JD9, through the MM input has 70db of gain. Add the 37db of gain that the i-1 has and you have a total of 107db! That's about double what you really need.

I agree with Zd542, try the low output. That will reduce the gain by a little over half. Much closer to what you need.

Not sure why Jolida provides such a huge amount of gain, but hey, if you need it it's wonderful, if not, overload city.
The fact that the problem only occurs in the treble region would seem to suggest that it is arising in circuitry within the JD9 that is "ahead" of its RIAA equalization function, or that perhaps involves the RIAA equalization function itself. That function attenuates the treble content of the signal provided by the cartridge, the amount of attenuation increasing as frequency increases, compensating for a boost that is introduced in the recording process.

If you don't have any spare 12AX7's to try in the JD9, it might be worthwile to simply try interchanging the two 12AX7's between the two sockets. Even if that doesn't fix the problem, if it results in a significant difference of any kind it would suggest the possibility of a bad tube.

Also, you might try working each of the six gain select switches back and forth a couple of times (while the system is turned off!), in case there is some marginal defect in them that might be causing one of the MC gain settings to be inadvertently selected.

Also, consistent with some of the comments by ZD and Mofi I'm surprised that you have found the high output jacks to be preferable to the low output jacks, given the relatively high output of your cartridge (5.5 mv under the standard test conditions, assuming that the cartridge is a 2M Blue, not a 3M Blue as stated), and given the unusually high gain of the JD9 MkII (60 db in the MM position, which I presume applies to the high output jacks, and if so would correspond to about 49 db at the low output jacks, which is still very high). (The original version of the JD9, btw, was spec'd as having even higher gain, 70db for MM's as Mofi noted).

Finally, I see that your integrated amp has an input sensitivity spec of "370 mv to 3.0 volts rms." That would seem to imply that its sensitivity can be adjusted, although the manual doesn't refer to any such adjustments. If it is in fact adjustable, however, and it is presently set to the lower (more sensitive) part of that range, and its volume control is not located at the very front end of its internal signal path, it is certainly conceivable that the high gain of the JD9 coupled with the relatively high output of the Ortofon would overload whatever circuitry in the amp is "ahead" of the volume control. You might want to contact Simaudio and ask about the meaning of that spec, and if input sensitivity is internally adjustable.

Just some thoughts; hope they help. Regards,
-- Al
Al...thanks for the correction on the output spec of the JD9MKII. I was indeed looking at the original unit, (I missed the MK2 notation).
Try these settings for your cartridge: Use low output jacks (the ones further away from the power cord) and all gain settings (1/2/3) the bank by themselves to the right to off or down on both channels. On the (2) rows of (8) switches turn them all off or down except # 4 & 7, turn them on or up
THANK YOU! I appreciate all of the suggestions. I tried a few different things, and it turns out that Dill was spot on. I turned all the gain switches off and ended up turning on #4 and #8, which gave me the best sound. I still far prefer the high output RCA connections as the low output seems to give a somewhat muted sound with rolled of bass.

In any event, it looks like I'm good to go! I do wish that the instructions with the Jolida were clearer. And they suggest starting with the med gain switch turned on - WAY too much.

Thanks again, now back to the music…

Best, Scott
Great!

Regarding the sonic differences you described between the high level and low level outputs, that is most likely resulting from differences in impedance interactions between the phono stage and your integrated amp. I see that the i-1's input impedance is spec'd at a somewhat low 11K, and was measured by John Atkinson as being "11.3k ohms at bass and midrange frequencies, dropping to 7k ohms at the top of the audioband." The output impedance of the JD9 MkII is spec'd at 600 ohms, but the design most likely uses an output coupling capacitor which will result in the output impedance rising to considerably higher values than that at deep bass frequencies, perhaps several thousand ohms at 20 Hz. The interaction of those two impedance characteristics is very consistent with your observations of "a somewhat muted sound with rolled off bass."

And it seems very conceivable that the output impedance of the JD9's high level output is significantly lower than that of the low level output, causing those effects to be minimized or eliminated when the high level output is used.

So as long as using the high level output doesn't result in anything being overdriven and audibly distorted, and doesn't result in your having to use the volume control undesirably close to the bottom of its range, you are good to go. Enjoy!

Regards,
-- Al
Hello everyone,

I apologize for resurrecting this old thread, but I’m having the same types of issues as the original post with my current setup with distortion in the higher frequency ranges using the following setup:

Audio Research LP1 Phono Preamp
Denon DL-103R
Bob’s Devices 1131 SUT (distortion occurs at both 1:20 and 1:40 settings)
Rotel RSP-1572 Line Preamp
Rotel RB 1090 Power amp
B&W 804s Speakers

I was able to get rid of the distortion by swapping out the Bob’s Devices 1131 SUT with the Denon AU-320 using the 40 ohm setting, but loved the sound from the 1131 SUT when it wasn’t distorting at the higher frequency ranges, so I would prefer to use the 1131 SUT if the distortion can be fixed.

Any suggestions or recommendations to help solve the distortion issues would be greatly appreciated. Thanks in advance for your time and help.




-Ray