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I have a Jolida 3502 integrated. When in bypass, that is "amp" mode, it makes a rather loud buzz louder in the left channel, but both. The noise comes over all drivers including tweeters and is the same with or without the preamp hooked up.
I've tried the usual preliminary troubleshooting, such as a cheater plug, swapping tubes, cleaning the ground post where the third prong, chassis and signal ground meet, checked wall polarity, and the internal wiring is nicely separated with power on one side, signal on the other.
Does this sound like a power supply issue, like a cap or something?
I don't see a typical diode bridge in the power supply area, so maybe the parts are discreet.
If so, why would the noise be louder in one channel?
Don't have a scope & I can't seem to find a schematic...This is driving me nuts as It would be a great amp minus the noise, especially with the KT150s. EH EL34s were boomy,
thanks for any ideas
Edits: 08/31/16 08/31/16Follow Ups:
Have you tried plugging into another outlet? One with little or no other appliance attached. Just to rule-out low AC voltage issues?
A buzzing sound may also indicate that a transformer is going bad. If the amp was not meant to output as much current that the kt150 need it may have stressed your trannys. Maybe the insulation has developed a bad spot and has developed a short. Taking some resistance readings might show this up , but sometimes the problem won't show until your amp is energized.
Edits: 08/31/16
I put the EL34s back in to see if it was the new KT150 tubes.
Nope, same noise with the EL34s
Did the manufacturer of your amp tell you that it was safe to use in your amp. If it is still under warranty you might be able to sneak it by the store you bought it from. If its mail order, good luck.
Yes, that's it in the link. It has a switch on the back for EL34/6550, to get it in the family range, then you adjust the bias screws.
The manufacturer didn't tell me directly it could use those tube, just somewhere on the forum, and I think in a Jolida ad it said you could use them. Minimal hours on it with KT150s. I plugged them in because the Electro Harmonix EL34s were useless
Edits: 08/31/16 08/31/16
I guess it is all water under the bridge as that trite saying goes. Hopefully it is not something major that is wrong. If your amp started making the odd buzzing after you put in the 150s then those tubes in all likelihood caused the odd noise. And since reverting to the el34 did not change things you must now do some serious checking. When a transformer is buzzing that causes a vibration so if it is a trans then you should feel the buzzing vibration of the offending tranny.
Well there was some mechanical noise from the tranny even though the power is run through a DC blocker. I was able to snug the bolts and the mechanical buzz is quieter.
now to just figure out this signal loop...
Ok, here's a new symptom. When the preamp is off but still connected to the jolida there is the noise. When I unplug the left intercon the noise mostly goes away! so it looks like a ground loop, but not in the AC, in the signal cable. now is it the amp or the modwright 36.5 pre?
To go from el34 to kt150 is a pretty big leap in current requirement both in the filaments and the high voltage current.
If the amp has no issues in its full operation position as an amp and its own existing preamp,there is no problem with the amp's power supply.You probably have a dirty switch that switches it to an independent amp or a bad cable somewhere.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
The problem is still there in amp+preamp mode, just the noise is quieter.
I looked at the input wires and check continuity, all looks good..
That would be a filter cap..The Jolidas are an easy amp to change the power supply caps in as all you do is unplug the board and take out about six or eight screws and it drops right out.Can you pop the bottom off and post a photo? How old is this particular amp?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
I'm not sure when it was made exactly, but i understand this model is fairly recent, 3502rc.
I've had the bottom off as like I said, I checked a few things already.
Maybe I can post a picture tonight. You think its the big filter caps?
It's been suggested that it wouldn't be power supply as it doesn't happen as much with the preamp portion engaged. The factory has said KT 150s would work in this amp, they are biased at 500mV as are the 6550s.
Edits: 08/31/16 08/31/16 08/31/16
Push on the board of the amp in different places while it is turned on and hooked up so you can hear the hum..You can even push on the filter caps..If it the hum clears up,you may just have a bad solder connection or you may need to tight the screws on the board..Is this your amp in this link?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
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