My Bad Luck With Phono Preamps

[Jim Creek]

My Schiit Mani 2 phono preamp developed a problem after 1.5 years, still under warranty. The left channel became dominant while the right channel became very weak. Of course this shifted the soundstage way to the left. I tried numerous configurations with cables, cartridges headphones, etc. I came to the conclusion it was the phono preamp.

I sent it back for repairs under warranty. It came back after three weeks. The invoice said both left and right op amps were replaced. I tried it out and it had the same problem, left channel still too dominant.

Rather than send the Man 2 back a second time I bought an Art Precision phono preamp to make a comparison, $79 on Amazon. The Art played perfectly, left and right channel balanced, with great acoustics…...at first listen.

Then I noticed a soft noise in the Art. It was a rapid ‘putt…putt…putt’ noise coming from the Art. Turning up the Gain on the Art or turning up the volume on my Topping Pre90 preamp increased the noise.

This Art Pre is the newest version with the 12v DC power supply. I tried it using a MC cart Denon DL103 and MM cart AT95ML. The noise was there with both carts. I sent the Art Precision back to Amazon. They're going to replace it with another Art Precision at no charge.

I don’t know what to do with the Mani 2. The invoice had a bunch of tests with check boxes marked off. The Schiit tech thinks it’s good. Will Schiit believe it’s still defective? Is it worth spending another $15 to send it back? I don’t know

 

[AnalogSteph]

The ART may be prone to RF interference, which can happen in phono preamps that are not taking adequate precautions against RF ingress. Do you have any WiFi router or cordless phone base station nearby?

I don’t know what to do with the Mani 2. The invoice had a bunch of tests with check boxes marked off. The Schiit tech thinks it’s good. Will Schiit believe it’s still defective? Is it worth spending another $15 to send it back? I don’t know

Could you cobble together a loopback measurement setup? Ideally stereo, but mono with two measurement runs to show the difference in level would also work (then you could make of the Macbook headset jack). You basically just need a frequency response measurement for both channels with the same settings, the difference in level should not be subtle. If there is a random old PC still floating around that's got onboard audio and can run RMAA or REW, that would also work.

 

[Jim Creek]

The ART may be prone to RF interference, which can happen in phono preamps that are not taking adequate precautions against RF ingress. Do you have any WiFi router or cordless phone base station nearby?

YES, you nailed it. I experimented by moving the Art as far away from the wireless router as possible. The “putt…putt….putt” diminished the further away from the router. I found the cause on my own but you just confirmed my finding.

The noise is still there if I max out the Art gain, the headphone amp and the Topping preamp. That is an over the top scenario though. Under normal loud listening levels the Art is dead silent.

Question: Is there any type of shielding that can block RF?

 

[computer-audiophile]

Question: Is there any type of shielding that can block RF?

In the simplest case, you can use an aluminium foil that is earthed via a cable and encloses the device. A static screen. However, you cannot simply wrap every appliance in it, as heat could build up inside.

 

[LTig]

YES, you nailed it. I experimented by moving the Art as far away from the wireless router as possible. The “putt…putt….putt” diminished the further away from the router. I found the cause on my own but you just confirmed my finding.

The noise is still there if I max out the Art gain, the headphone amp and the Topping preamp. That is an over the top scenario though. Under normal loud listening levels the Art is dead silent.

Try to find out how RF enters the Art. Do this and note any changes in noise

1. Disconnect the cable from the input
2. Short cut the input
3. move the PS close to the router

Question: Is there any type of shielding that can block RF?

One could wind the cable which transmisses RF through a coil core. Or add an inductivity in series to the life wire of the input connection (that has worked here) if tbe input is the culprit.

 

[DVDdoug]

My Schiit Mani 2 phono preamp developed a problem after 1.5 years, still under warranty. The left channel became dominant while the right channel became very weak. Of course this shifted the soundstage way to the left. I tried numerous configurations with cables, cartridges headphones, etc. I came to the conclusion it was the phono preamp.

Did you try swapping the left & right inputs? It might be a bad connection somewhere in the turntable between the cartridge and preamp.

The invoice said both left and right op amps were replaced. I tried it out and it had the same problem, left channel still too dominant.

Yeah... Op-amps don't normally fail that way. They could die completely or become noisy, or something, but the gain is determined by passive components in the feedback loop (resistors and then usually there are capacitors and that's where the RIAA EQ is done). And those passive components are normally stable.

Possibly it's intermittent. It's super-common for something to work perfectly when in the repair shop. Sometimes maybe vibrations or shocks during transportation "fix" or "break" a flaky internal connection or solder joint. Or maybe it's just a variation of Murphy's Law.


...I so glad I gave-up analog decades ago!

 

[Godataloss]

YES, you nailed it. I experimented by moving the Art as far away from the wireless router as possible. The “putt…putt….putt” diminished the further away from the router. I found the cause on my own but you just confirmed my finding.

The noise is still there if I max out the Art gain, the headphone amp and the Topping preamp. That is an over the top scenario though. Under normal loud listening levels the Art is dead silent.

Question: Is there any type of shielding that can block RF?

Is the preamp itself grounded? Maybe try different ground scenarios. I'll get the 'put, put' noise in my system if my cellphone is in my pocket and I'm standing at my turntable. It goes away after a couple feet.

 

[EdW]

In the simplest case, you can use an aluminium foil that is earthed via a cable and encloses the device. A static screen. However, you cannot simply wrap every appliance in it, as heat could build up inside.

But the real problem lies at the design stage. The product should NEVER have been released without RFI susceptibility issues being identified and addressed. Many engineers on ASR would probably agree here!

 

[LTig]

But the real problem lies at the design stage. The product should NEVER have been released without RFI susceptibility issues being identified and addressed. Many engineers on ASR would probably agree here!

I do but e.g placing my smartphone right beside my MC pickup might be too much if it connects to a base station far away.

 

[ta240]

But the real problem lies at the design stage. The product should NEVER have been released without RFI susceptibility issues being identified and addressed. Many engineers on ASR would probably agree here!

It shouldn't be, but at $80 retail they have to stop development somewhere.

This is a good example of things that aren't tested for that can really affect an items performance. It got a pretty decent review and mostly favorable votes on here. Yet this issue could render it pretty much unusable for many.

 

[computer-audiophile]

But the real problem lies at the design stage. The product should NEVER have been released without RFI susceptibility issues being identified and addressed. Many engineers on ASR would probably agree here!

Possibly (more likely!) the devices mentioned fulfil the legal requirements regarding CE and electromagnetic compatibility. We do not know the problem precisely enough to criticise the manufacturer.

 

[Jim Creek]

This is my second Art Phono Pre. I sent the first one back thinking it was defective. Since it's prone to RF interference I guess it does have a design flaw, but I’m going to keep it. Truth be told, I rather like the ease of switching between MM and MC. I like the gain control. All in all it sounds decent.

Vinyl is not my main media choice. Rather than give away my record collection I choose to own a decent phono setup. Relocating the Art made a big difference. It’s good enough.

Regarding the Mani 2, I’ll have to send Schiit another email.

Thanks to all for your input.

 

[EdW]

This is my second Art Phono Pre. I sent the first one back thinking it was defective. Since it's prone to RF interference I guess it does have a design flaw, but I’m going to keep it. Truth be told, I rather like the ease of switching between MM and MC. I like the gain control. All in all it sounds decent.

Vinyl is not my main media choice. Rather than give away my record collection I choose to own a decent phono setup. Relocating the Art made a big difference. It’s good enough.

Regarding the Mani 2, I’ll have to send Schiit another email.

Thanks to all for your input.

Great that you’ve got a workaround to the interference problem. Enjoy your listening!

 

[computer-audiophile]

Since it's prone to RF interference I guess it does have a design flaw

I would not assume that. Is there any proof of this? I would be cautious with such attributions.
This particular phono pre is in mass use. I know people who have one myself, without any problems.

 

[Jim Creek]

I would not assume that. Is there any proof of this? I would be cautious with such attributions.
This particular phono pre is in mass use. I know people who have one myself, without any problems.

The evidence for RFI is somewhat conclusive. Both Art units had the same problem with RFI. The further from the wireless router the more diminished the noise. My Mani 2 did not have any problem with RFI. What would you conclude from that?

 

[computer-audiophile]

What would you conclude from that?

I have other questions.

Why don't other users of this widely used phono preamp report such problems? Or do you know of such reports? That would confirm your assumption.

Perhaps you have something in your environment that causes severe interference and does not comply with the relevant standards.

Unfortunately, I don't know the ART circuit. Normally there is an R-L-C filter in the input of such a phono preamp that suppresses RF specifically. I am pretty sure that this is also the case with the ART phono. These circuits are not very special.

 

[Jim Creek]

I have other questions.

Why don't other users of this widely used phono preamp report such problems? Or do you know of such reports? That would confirm your assumption.

Perhaps you have something in your environment that causes severe interference and does not comply with the relevant standards.

Unfortunately, I don't know the ART circuit. Normally there is an R-L-C filter in the input of such a phono preamp that suppresses RF specifically. I am pretty sure that this is also the case with the ART phono. These circuits are not very special.

Skepticism can be a good thing.

All I can say is I’m dealing with the problem as an RFI issue and have been successful in reducing the noise to near imperceptible by strategic placement of the Art. Under normal listening the RFI is a non-issue now.

 

[computer-audiophile]

Sorry - I did not want to appear too critical. Sometimes I even enjoy tricky troubleshooting.

When I looked at your profile, I saw that you have some nice devices that I would also like. For example, the Pioneer PL-41, which is a very solid classic turntable, and I also think the PLX 1000 is pretty good. And I have also used the DL103 as my house standard cartridge for decades.

That's just by the way.

 

[Blumlein 88]

Someone else mentioned some grounded foil. I've used that successfully a couple times. Just a cardboard panel wrapped in foil and grounded. In one case a Mac Mini was causing noise. Put the foil between the two and it went away. Later moved the TT and phono several feet away. Another time put the foil on the underside of the shelf above the phono pre and it got rid of RFI from a DAC.

 

[mhardy6647]

As I recall, the onus is on the RFI "emitter" not to interfere -- at least under US regulations, and the last time I looked

All those concerns pretty much went out the window, though, as our bright digital future dawned.