I recently added a Parasound JC3 (original) to my collection. I also own phono stages from Micromega, Goldmund, and Ayre.
I'm using an Ortofon 2M Black in an SME 309 tonearm with original SME tonearm cable.
At preamp volume set to listening levels, but no record playing, I can hear a somewhat loud hiss from the JC3 and it's audible even if I'm 20 feet away. It's not a hum, or a buzz. Grounding is dead quiet. It's a white noise hiss coming from both channels. It's not very audible while music is playing, but I can still hear a global hash like sound over everything. This is on the rear switches set correctly to 47K MM for my cartridge.
Without changing anything, if I flip the switches to 100 Ohm MC position (no record playing), the hiss becomes significantly less, but still audible, even from a good distance.
If I flip both switches to 47K MC (no record playing), the hiss is extremely loud like in a wind storm.
All of my other phono preamps are silent. Any ideas on where I should start to fix the problem?
My other question is gain related. JC3 with 47dB of MM gain overloads an input on one of my other preamps. Is there a proper procedure to lower the gain to around 40dB? Does anybody know which resistor and to what value it needs to be replaced?
Thank you for all of your time, advice, and feedback.
I'm using an Ortofon 2M Black in an SME 309 tonearm with original SME tonearm cable.
At preamp volume set to listening levels, but no record playing, I can hear a somewhat loud hiss from the JC3 and it's audible even if I'm 20 feet away. It's not a hum, or a buzz. Grounding is dead quiet. It's a white noise hiss coming from both channels. It's not very audible while music is playing, but I can still hear a global hash like sound over everything. This is on the rear switches set correctly to 47K MM for my cartridge.
Without changing anything, if I flip the switches to 100 Ohm MC position (no record playing), the hiss becomes significantly less, but still audible, even from a good distance.
If I flip both switches to 47K MC (no record playing), the hiss is extremely loud like in a wind storm.
All of my other phono preamps are silent. Any ideas on where I should start to fix the problem?
My other question is gain related. JC3 with 47dB of MM gain overloads an input on one of my other preamps. Is there a proper procedure to lower the gain to around 40dB? Does anybody know which resistor and to what value it needs to be replaced?
Thank you for all of your time, advice, and feedback.
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Quick update: If I short the inputs, but leave the outputs connected and volume set to listening level on the preamp, the JC3 is dead silent.
As soon as I connect the tonearm cable to the inputs, hiss returns.
If I leave the inputs completely open, hiss is loud like a wind tunnel/ocean.
As soon as I connect the tonearm cable to the inputs, hiss returns.
If I leave the inputs completely open, hiss is loud like a wind tunnel/ocean.
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Could be some kind of RF pickup. Which tonearm and cable do you use?
Are you near a strong radio/TV station transmitter? Also, try turning off
all your electronic devices and lighting, in case you have your own noise source.
If both channels are affected, it's not likely to be a preamp malfunction.
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Not near a radio station. And it doesn't do it with any other phono stage, I have several on hand.
I was thinking it could be possible RF, or maybe it's oscillating. But can't seem to figure out the problem.
I was thinking it could be possible RF, or maybe it's oscillating. But can't seem to figure out the problem.
Check for your own noise sources, like light dimmers, LED lights, computers, etc.
Do the turntable RCAs fit tightly on the JC3 sockets?
Also, check for the noise at different times of day, in case the noise source varies.
Is the JC3 used? If so, maybe someone damaged the inputs, by wrongly connecting them.
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All checked, no change. RCA's fit snug. I've had the unit since yesterday. Noise did not change from daytime to evening.
Ok, then try the JC3 in a friend's or a dealer's system.
If the noise is still there, the JC3 input op amps must be damaged.
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Input IC is an LME49990, a bipolar part. It would be strange that both channels are damaged in the same way?
It would be unusual, but if the phono inputs were plugged into the output of a preamp, etc,
it's possible. Or, static electricity damage is possible. Also, sometimes there are bad batches
of parts due to process or handling problems.
Once I got a bad batch of Dale RN60 metal film resistors. After some hours of operation,
they became quite noisy. Of course, they were the plate load of the input tube in a phono preamp,
about the worst place for a noisy resistor. I built dozens of preamps with those parts before the
noise started. The mfr admitted the problem, and offered free replacements, as if that was a
significant part of the cost of the repairs.
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The IC used is extremely sensitive to RFI and there should be a small inductor or resistor filter on the input that solves the issue. But first I would check the switch settings and work them a bit to be sure they are clean.
Finally I would look inside to be sure no one has previously fixed or modified the unit.
Finally I would look inside to be sure no one has previously fixed or modified the unit.
Yes, you should still try the preamp in a different system in a different location.
It's fully soldered and on a DIP adaptor. I don't have any on hand. It's a discontinued part and no longer stocked at DigiKey, Mouser, etc. But plenty of fakes available from China on eBay!
This sucks. And it may not even be the culprit.
Try it elsewhere. If noise is not gone, get a factory repair. They'll have spare parts.
It's certainly worth repairing, and it may get worse with time if the ICs are damaged.
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I looked inside. It doesn't appear to have been touched. RFI is what I'm thinking, because shorting the inputs produces dead silence. But this thing is double and triple shielded. Circuit boards are housed in separate metal enclosures.
There what appears to be a 100pF capacitor on the input. The only resistor on the input is the load resistor, 47K on the MM switch position.
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The JC-3 should be OK, either you have a faulty input lead or you have not connected the cartridge. IF it is super quiet when shorted, then your problem is in the finite loading (greater than 100 ohms) of the cartridge. The MC gain is too high for a MM cartridge, but there will always be SOME added noise from the cartridge and the paralleled 50K load, as well as some added current noise present from the input transistors in the IC. It will NOT ever be as quiet, all else being equal, to a low noise jfet input op amp.
Hi John, thank you for your quick response. I want to first say that the actual sound the JC3 produces is absolutely fantastic. It's clear and it plays music with conviction. The bass is extended and clean and the soundstage is wide. There's a rendered three dimensionality and a very pleasant textured midrange. It really is as good as the best I've heard.
Having said that, the white noise/hiss I'm experiencing is unacceptable in my opinion. The cartridge I'm using is an MM Ortofon 2M Black. It's connected to the tonearm leads and has not been disconnected. The SME/van den Hul tonearm cable works as it should.
I have several other phono preamps and while they all have varying amount of noise, none of them are audible from the listening position, some 10-15 feet away.
The JC3 is set to MM 47K switch position, which is correct for Ortofon 2M Black. I listen to music pretty loud, but not loud enough to be uncomfortable. When the volume is open to this position on the preamplifier and no record is playing, I can still hear the hiss from another room in a quiet house. It's that loud. While with virtually all other phono preamplifiers I own I'd have to lean over to the speaker to hear anything.
If I listen long enough to this hiss, there's also what seems like an occasional brief random sputtering sound. With the inputs shorted, it's as quiet as any other phono preamplifier I own.
Thank you again for your time and help.
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My suggestion would be to take jc3 and perhaps one other preamp and visit a friend with good turntable setup. Swaping preamps should reveal if jc3 has the same hiss issue at diiferent place. If it does not, you need to modify your set up to prevent rfi or oscilation. Which can be difficult. If its noisy at other place, it may be defective.
In either case you can sell it.
In either case you can sell it.
With that barely adequate cartridge ( 😉 ) you should be using the low gain setting on the preamp. That should drop the noise by 20dB.
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