High Frequency noise through tweeter

[sometimesuk]

Hi,

I am using a Musical Fidelity A1 FBP preamplifier and two Musical Fidelity 550k monoblocks.
Ever since I've had the speakers when no music is playing, if I put my ear to the tweeter I can hear static/ high frequency noise. This does not really get louder when I turn the volume up but remains constant.

I have has all the units "upgraded" or refurbished through a popular electronics engineer that works on Musical Fidelity equipment and the issue is same, albeit less than before.

Even though this is never an issue when listening to music, I do wonder if an amplifier with a lower noise floor would sound better.

When I look at the technical specifications of the mono blocks, they have a signal to noise ratio of 120db Vs the preamplifier at 96db.

Would trying a preamplifier with a lower designed noise floor resolve this issue, or is something else going on? If it is the preamplifier, are there any well regarded products to audition?

Thank you.

 

[Chrispy]

Sounds like typical amp hiss. If it is just audible when your ear is up against the speaker just relax and enjoy the music....

 

[MaxwellsEq]

If you can make up some input shorting plugs and connect them to the inputs of the power amplifiers, you will be able to identify if the noise is coming from the power amplifiers.

All amplifiers have "self noise". If you can only just hear it in a quiet room with your ear to the tweeter, you can be pretty confident it's not a problem.

 

[sometimesuk]

The mono blocks only have one input, which I'm using. I've already put shorting plugs on the unused preamp inputs... I can just about hear the noise with my ear right next to the speaker, certainly less than years ago, though this is probably more to do with me getting older (40) than any upgrades done to the amp.

When you read about a black background / lower noise floor, that is the technical factor that determines that? Is there one?

 

[Zek]

he mono blocks only have one input,

make up some input shorting plug and connect them to the input of the power amplifiers

Try this first and see if there is a hiss from the power amp (each mono block individually).

 

[sometimesuk]

So results are...

Amp and preamp, connected and both units switched on - faint buzzing

Amp and preamp, connected but preamp switched off, but still connected - 80/90% reduction in buzz.

Amp with shorting plug - buzzing noise so low, almost non detectable. Very very faint with ear right next to the tweeter.

 

[Hayabusa]

Hi,

I am using a Musical Fidelity A1 FBP preamplifier and two Musical Fidelity 550k monoblocks.
Ever since I've had the speakers when no music is playing, if I put my ear to the tweeter I can hear static/ high frequency noise. This does not really get louder when I turn the volume up but remains constant.

I have has all the units "upgraded" or refurbished through a popular electronics engineer that works on Musical Fidelity equipment and the issue is same, albeit less than before.

Even though this is never an issue when listening to music, I do wonder if an amplifier with a lower noise floor would sound better.

When I look at the technical specifications of the mono blocks, they have a signal to noise ratio of 120db Vs the preamplifier at 96db.

Would trying a preamplifier with a lower designed noise floor resolve this issue, or is something else going on? If it is the preamplifier, are there any well regarded products to audition?

Thank you.

putting your ear on the tweeter easily is gain of 40dB compared to 1 meter distance.. So that's why 96dB is audible, but assume not at 1 meter anymore?

 

[AnalogSteph]

So results are...

Amp and preamp, connected and both units switched on - faint buzzing

Amp and preamp, connected but preamp switched off, but still connected - 80/90% reduction in buzz.

Amp with shorting plug - buzzing noise so low, almost non detectable. Very very faint with ear right next to the tweeter.

That gives us some good clues, thanks. Definitely seems to have a fair bit to do with the preamp.

Could you try one more - source removed from preamp and shorting plug fitted on preamp input instead?

If you have a multimeter handy - which I hope you do - please measure the resistance between RCA input shell and IEC power connector ground pin on the 550K monoblock. I hope the amp designer was smart enough and you'll be seeing 10-100 ohms there at least, rather than a direct short.

Do you have the preamp and its power supply stacked right on top of each other? If there are any ground loops involved in the setup, the transformer's magnetic field could be coupling into them. Try physically separating the two parts.

I found this news item:

Home

This is the new Musical Fidelity A1 FBP – a fully balanced preamplifier designed to be used with the company's 550K and 750K Superchargers, which are also designed to function as conventional powe

www.whathifi.com

This is the new Musical Fidelity A1 FBP – a fully balanced preamplifier designed to be used with the company's 550K and 750K Superchargers, which are also designed to function as conventional power amplifiers.

Not sure about this whole "designed for" thing.

Would trying a preamplifier with a lower designed noise floor resolve this issue, or is something else going on? If it is the preamplifier, are there any well regarded products to audition?

If you have but a single source, and I have a hunch it's not going to be the vinyl spinning kind then - have you considered a DAC that can serve as a preamp? There should be some decent choice around 300 quid already if I have my exchange rates right, and more than enough up to twice that. (You can go cheaper but eventually would have to contend with volume control via a remote only. As a budget option, you could still consider a DAC and headphone amp plus a stereo 1/4" TRS to 2x RCA adapter cable, say a Topping DX1 or something. Going to this inexpensive little thing from a once £1499 2-box preamp monstrosity seems hilarious, but I mean if it works, it works...)

 

[sometimesuk]

I don't have a multi meter, but I unplugged my source and inserted the shorting plugs and it was absolutely silent, nothing whatsoever.

Trying another input, was the same if not worse..

The power section of the amplifier is alongside the other box. I'm not sure about buying another DAC, at least for a while... I'm using a naim Dac with an external power supply, fed by the digital output of an Eversolo A6 ME.

 

[AnalogSteph]

I don't have a multi meter, but I unplugged my source and inserted the shorting plugs and it was absolutely silent, nothing whatsoever.

OK, so it looks like we've got a ground loop running through the preamp then.

Multimeters are quite handy to have around and not expensive (a half-decent basic one might be 20-30 quid or something, doesn't have to be a Fluke), well worth picking one up on the next trip to a DIY store.

I'm using a naim Dac with an external power supply, fed by the digital output of an Eversolo A6 ME.

The first thing I'd try then is plugging the cables from the monoblocks into the A6's ANALOG OUT, making sure its volume is turned down of course. You don't even need to buy a preamp-grade DAC, you've already got one right there!

If that improves the issue (or at least doesn't make it worse), great, you've got a bunch of stuff to get rid of. It's a good time for spring cleaning anyway.

If some buzz still remains then, I guess you'd be looking for some ground loop isolators to go at each monoblock input. As anything involving transformers, good ones will cost a bit of money but it shouldn't be outrageous. I would also make sure that these relatively lengthy cables are of decent construction, e.g. using RG-59 coax or something.

 

[sometimesuk]

The Naim Dac is definitely staying..the eversolo in comparison sounds less refined and more coarse l.

The Naim Dac does have a switch to toggle between chassis / floating... No idea what the difference is.. Maybe I'll experiment with that... But I'm sure the Preamp always used to have this hiss before I had the Dac and in my old house.

 

[AnalogSteph]

So did you try what I suggested, and if so, what were the results?

The Naim Dac is definitely staying..the eversolo in comparison sounds less refined and more coarse l.

These subjective differences tend to miraculously evaporate into thin air in a properly level-matched (ideally to <0.1 dB) blind test - unless one of the DACs is really bad, that is, which is rare. Level matching is another opportunity for a multimeter to come in handy, though it needs to be fancy enough to have a mV AC range (TrueRMS to several kHz recommended).

DACs are technically interesting but definitely overrated in audiophile circles. Definitely not something to spend a ton of money on unless you get some special party tricks like DSP functionality, or you're a Hollywood studio and absolutely need +24 dBu output levels. Otherwise they're generally the last thing to make any sonic difference whatsoever. And don't even get me started on the UK hype rags that kept propping up mediocre products from homegrown brands as the best things since sliced bread... just an unbelievable amount of hot air. It's an entire industry that's kept up by little more than belief.

BTW, Amir noted that the Fast Linear digital filter setting gave the best overall performance, so I would use that:

Eversolo DMP-A6 Streamer Review

This is a review and detailed measurements of the Eversolo DMP-A6 Streamer and balanced DAC. It was sent to me by the company. I don't have the price but see it on sale for US $850. The DMP-A6 design is absolutely gorgeous. A large, high contrast LCD allows it to show realistic visualizations...

www.audiosciencereview.com

This used to be the traditional default for a reason.

 

[sometimesuk]

The difference were more than just volume. Also isn't it a bit simplistic to say that all DACs sound the same, what about the differences between the analogue outputs stages, or power supplies. I'm using a external power supply with the DAC and it made an immediate noticeable uplift in sound quality.