Help connecting preamp to amp.

aperayil

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Apr 30, 2021
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Hello Everyone,

I am just venturing into the audio DIY world, looks like its an amazing ride.
Seems I have hit my first issue already - cant seem to get my preamp and amp to work from the same power source.

Preamp - XH-A901 - NE5532 (with a rectifier at power supply) - https://www.amazon.in/InkOcean-XH-A...hild=1&keywords=ne5532&qid=1628521380&sr=8-16
Amplifier - XH-M510 - TDA7498 - https://www.amazon.in/Triupy-XH-M510-TDA7498-Digital-Amplifier/dp/B07RCHC6ZL
SMPS - LRS-200-24 - https://www.amazon.in/Meanwell-Switching-Supply-LRS-200-24-Transformer/dp/B00YMA7I7C

Setup - audio source > XH-A901 > XH-M510 > Speakers
The setup works only if the preamp is powered separately, with another SMPS.

Tried bypassing the rectifier on preamp, since it was receiving DC already, but no luck.
Should I have a common ground for both boards or something on those lines?

Pretty sure I might have got something basic wrong in here, hope you guys can point me at the right fix?

Thanks in advance!

Also happen to have a 6J1 tube preamp (AC 12v) https://www.amazon.in/preamp-amplifier-Pre-amp-Headphone-buffer/dp/B06X9T3SRS, was planning to put this in to the above setup as an optional preamp - like switch between the 6J1 and NE5532 preamp with a rotary selector.
 
If it's hum or buzz you are encountering when connecting the preamp to amp ,then it's a ground loop issue .
 
I have a hybrid tube preamp connecting to a poweramp single ended. I hear crackling or static noise only when volume pod is rotated. Once volume is settled no hum or static is heard after that. Can anyone throw some light on what could be the reason? I have 3 sets of tubes to roll... The behavior is pretty consistent.
 
Thanks for the feedback adas and spirovious and sorry for my late response.

adas, its not hum or buzz, no sound at all.
spirovious, i tried swapping the SMPS to no avail.

Trying to clarify the setup and some observations made -
Amp - A
Preamp - P
SMPS - S1, S2

A on S1 & P on S2 - works - multimeter shows NO connectivity between preamp's source/output signal ground with supply ground
A on S2 & P on S1 - works - multimeter shows NO connectivity between preamp's source/output signal ground with supply ground
A & P on S1 - doesn't work - multimeter shows connectivity between preamp's source/output signal ground with supply ground
A & P on S2 - doesn't work - multimeter shows connectivity between preamp's source/output signal ground with supply ground

The setup works only if pre-amp supply ground is isolated from the amp & signal ground.

That leads to my next question, apologies if its stupid -
is there a way to decouple/isolate ground between the preamp and amp even if they are on the same power source?
like a DC/DC isolator on the pre-amp supply?
 
SMPS actually may not be a good choice for preamp. Leaner PSU is better way. Exact issue I may not be able to figure out but since its SMPS, it may have noise unless its designed better way.
 
Thanks spirovious, I will go ahead with a liner power supply source for the pre amp, have a spare 12v 1A transformer.

Just in case it interests you, the setup works if the signal ground between pre-amp and amp is left open, but it brings in a nasty hum/buzz which increases with volume, maybe the ground-loop that adas mentioned earlier.
 
I have a hybrid tube preamp connecting to a poweramp single ended. I hear crackling or static noise only when volume pod is rotated. Once volume is settled no hum or static is heard after that. Can anyone throw some light on what could be the reason? I have 3 sets of tubes to roll... The behavior is pretty consistent.
Solved it by cranking the volume knob several times back n forth forcefully . Apparently it's carbon deposits that create the noise.
 
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