JDS Atom as volume control for a power amp?

[SteveJ]

Hi,

Thanks to lurking here I've gone from playing my music through tiny computer speakers (chosen because they fit under my monitor stand) to listening with AKG K371 headphones connected to a Topping D10s DAC and JDS Atom headphone amp. As much as I like that setup, I don't want to listen using headphones all the time, so I've been looking at upgrading my speakers.

That's proven to be a much more difficult decision. I originally planned to simply upgrade my computer speakers and rearrange my desk to fit them in. Then I decided to rearrange my room instead, allowing the use of larger floor standing speakers. That just left me procrastinating about whether to get active speakers, e.g. well reviewed studio monitors, or passive speakers and a separate amp.

It's the latter option that I've finally decided on, mainly as I've seen a good deal on a pair of Revel Concerta2 M16 speakers, so that just leaves the amp.

The simplicity and money saving of a no-frills power amp is more appealing to me than an integrated amp with features and inputs I don't need. I'm in the UK and don't want to import, so I was thinking of something like a IOTAVX PA3, or maybe one of the Hypex NCore amps from Nord. Please feel free to tell me that this is a stupid idea if you think I'm making a mistake!

The main issue I can see with using these products is simply that there's no volume knob. My understanding is that the JDS Atom can act as a pre amp if I connect its RCA output to the power amp, allowing me to use it to control the volume. I know I'd have to unplug the headphones whenever I wanted to play through the speakers, but that doesn't really bother me.

Before I put in an order and potentially make a silly mistake, I thought I'd better check whether there's anything I'm missing?

 

[AnalogSteph]

Nope, seems basically sound. This is pretty much exactly what the preamp functionality on the Atom is there for. I'd say try it and see what kind of fine-tuning in terms of busting ground loops may still be required, if any.

 

[dwkdnvr]

Yeah, I used it as a preamp for a while and it was fine. The only thing that might be an issue is if you want to use it as both a headphone amp and a speaker preamp in the same system (not unusual in desktop setups, and pretty much the intended use of the Atom). The speaker/line outs are muted when headphones are plugged in which works well. If the 2 setups have dramatically different gain settings though, you have to be pretty careful to make sure you don't blast yourself.

 

[SteveJ]

Yeah, I used it as a preamp for a while and it was fine. The only thing that might be an issue is if you want to use it as both a headphone amp and a speaker preamp in the same system (not unusual in desktop setups, and pretty much the intended use of the Atom). The speaker/line outs are muted when headphones are plugged in which works well. If the 2 setups have dramatically different gain settings though, you have to be pretty careful to make sure you don't blast yourself.

Thanks for raising that point. Is there anything that would roughly indicate the Atom settings I'd need to get a normal listening volume from a particular power amp + speakers?

I'm leaning towards an Audiophonics MPA-S125NC amp, mainly because even with shipping from France to UK it's a cheap option. Unless I've misunderstood things quite badly, it looks like it should offer enough power for the speakers I've chosen.

I think I've seen it mentioned that the Atom should be used in low gain mode if it's acting as a pre amp. That's what I use for my headphones so hopefully I wouldn't have to worry about changing that every time.

 

[SteveJ]

I received my Audiophonics MPA-S125NC today. It works fine with the Atom. Normal to fairly loud listening volumes with my amp+speakers and headphones are quite similar: low gain, dial somewhere between 9 and 12 o'clock.

I did initially have a ground loop issue. I had my PC plugged into one socket and the Atom plugged into a power strip without any problem, but when I added the amp the same power strip as the Atom there was a hum from both of them. Putting the amp and PC on the same strip fixed it.

The only remaining problem is that the Audiophonics amp itself buzzes fairly loudly. It's audible at about 6' when music isn't playing and sitting on my desk it's quite annoying. Fortunately I bought an interconnect that's much longer than I needed, so I can put it further away if there's no way to fix the buzz.

 

[cursive]

I received my Audiophonics MPA-S125NC today. It works fine with the Atom. Normal to fairly loud listening volumes with my amp+speakers and headphones are quite similar: low gain, dial somewhere between 9 and 12 o'clock.

I did initially have a ground loop issue. I had my PC plugged into one socket and the Atom plugged into a power strip without any problem, but when I added the amp the same power strip as the Atom there was a hum from both of them. Putting the amp and PC on the same strip fixed it.

The only remaining problem is that the Audiophonics amp itself buzzes fairly loudly. It's audible at about 6' when music isn't playing and sitting on my desk it's quite annoying. Fortunately I bought an interconnect that's much longer than I needed, so I can put it further away if there's no way to fix the buzz.

Glad you got your setup going! I used the atom with a VTV hypex amp for awhile myself, and it made a perfectly fine preamp.

Your description of the buzzing does sound concerning though, and you might want to check with audiophonics on that. I've definitely never heard a buzzing from my hypex amp, especially not at 6ft away, that seems like a pretty loud buzzing to be audible at that distance. Does it buzz with no interconnects connected at all, like just plugged into power? And you're saying the buzzing is comingi from the amplifier itself, not the speakers? If so, there may be a component inside that isn't functioning properly.

I'd definitely get it checked out vs just moving it further away if it buzzes with nothing plugged in at all.

 

[SteveJ]

Glad you got your setup going! I used the atom with a VTV hypex amp for awhile myself, and it made a perfectly fine preamp.

Your description of the buzzing does sound concerning though, and you might want to check with audiophonics on that. I've definitely never heard a buzzing from my hypex amp, especially not at 6ft away, that seems like a pretty loud buzzing to be audible at that distance.

Looking online, I do see some reviews and comments mentioning buzzing from these amps. I'm not sure if mine is particularly loud. At 6ft I have to actually listen for it, but it's louder than a quiet PC (6x 120mm Noctua fans at low speed) running in the same room.

Does it buzz with no interconnects connected at all, like just plugged into power? And you're saying the buzzing is comingi from the amplifier itself, not the speakers? If so, there may be a component inside that isn't functioning properly.

The speakers are near silent after fixing the ground loop issue and the amp buzzes with just the power cable attached.

It's definitely mechanical noise coming from the amp. If I push down on the top of the case then the tone changes and it gets quieter.

 

[cursive]

Looking online, I do see some reviews and comments mentioning buzzing from these amps. I'm not sure if mine is particularly loud. At 6ft I have to actually listen for it, but it's louder than a quiet PC (6x 120mm Noctua fans at low speed) running in the same room.



The speakers are near silent after fixing the ground loop issue and the amp buzzes with just the power cable attached.

It's definitely mechanical noise coming from the amp. If I push down on the top of the case then the tone changes and it gets quieter.

The main thing I would think could buzz would be the transformer on the power supply. I don't know enough to say it's bad, but perhaps it's not properly secured to the board/case, or is there some sort of damping that's missing?

There's a pretty good thread here on ASR about similar issue, not sure there's a definitive answer, but some of the others also seem to be audiophonics builds. https://www.audiosciencereview.com/forum/index.php?threads/do-ncore-have-buzzing-noise.9287/

My VTV has a ghent audio case, so perhaps it's less prone to vibration, or the buzzing issue, I'll have to listen to mine closely when I get home.
Obviously only you can decide whether it's worth the hassle of swapping it for a new one, but if it can be heard from listening position during a quiet part of a song, that would definitely bug me.

 

[SteveJ]

The main thing I would think could buzz would be the transformer on the power supply. I don't know enough to say it's bad, but perhaps it's not properly secured to the board/case, or is there some sort of damping that's missing?

I'm tempted to open it up and have a look, but I'm reluctant to risk invalidating the warranty.

There's a pretty good thread here on ASR about similar issue, not sure there's a definitive answer, but some of the others also seem to be audiophonics builds. https://www.audiosciencereview.com/forum/index.php?threads/do-ncore-have-buzzing-noise.9287/

I might bump that thread to add my own experience and see if anyone came up with a fix.

My VTV has a ghent audio case, so perhaps it's less prone to vibration, or the buzzing issue, I'll have to listen to mine closely when I get home.
Obviously only you can decide whether it's worth the hassle of swapping it for a new one, but if it can be heard from listening position during a quiet part of a song, that would definitely bug me.

It definitely isn't acceptable where it's currently situated, but the 2m interconnect between it and the Atom allows some flexibility. I don't think I'd notice it so much if it was on the floor behind my desk. It should also fit inside a desk drawer if I cut some holes for cables, but I guess heat might be an issue in such an enclosed space.

 

[cursive]

I'm tempted to open it up and have a look, but I'm reluctant to risk invalidating the warranty.



I might bump that thread to add my own experience and see if anyone came up with a fix.



It definitely isn't acceptable where it's currently situated, but the 2m interconnect between it and the Atom allows some flexibility. I don't think I'd notice it so much if it was on the floor behind my desk. It should also fit inside a desk drawer if I cut some holes for cables, but I guess heat might be an issue in such an enclosed space.

If you do open it, just be careful, mains power of course! I opened my VTV just out of curiosity, and luckily there were no warranty seal stickers or anything like that. I would think you could open it, listen for which component it is, or which area at least, and then close it back up with no one ever knowing, these cases are made to be taken apart for assembly. If it's just the case ringing from vibration or something, maybe you could dampen it somehow, but of course audiophonics should be doing this, or make changes if it's truly an issue.

These amps don't put out tons of heat, most of it is dissipated into the case itself, especially on the bottom, but do be careful about sticking it in a totally closed drawer. Some airflow/room around it on all sides is probably best. If you do find the source, or a solution, keep us posted!

 

[SteveJ]

If you do open it, just be careful, mains power of course! I opened my VTV just out of curiosity, and luckily there were no warranty seal stickers or anything like that. I would think you could open it, listen for which component it is, or which area at least, and then close it back up with no one ever knowing, these cases are made to be taken apart for assembly.

I've just had a look and there doesn't seem to be a sticker. As long as I don't break anything it shouldn't be a problem if I open it up and take a look.

If it's just the case ringing from vibration or something, maybe you could dampen it somehow, but of course audiophonics should be doing this, or make changes if it's truly an issue.

The sound only changes a little when I push down on it so I don't think it's just vibration through the case. I doubt that adding dampening would make much difference, especially without blocking the vents.

These amps don't put out tons of heat, most of it is dissipated into the case itself, especially on the bottom, but do be careful about sticking it in a totally closed drawer. Some airflow/room around it on all sides is probably best. If you do find the source, or a solution, keep us posted!

It looks like my desk drawer is too small for it anyway. Placed behind my desk, on the other side of my PC, it's much more tolerable. It's still audible while it's quiet and there's nothing playing, but of course at the moment I'm listening out for it rather than letting it fade into the background.

I have a cabinet that should silence it completely while leaving it some room to breathe. I'd need to get 4m or so long RCA cables to route them around the room to it. I don't know if that might introduce other problems, especially if I don't spend much on the cable?

 

[SteveJ]

It looks like I was completely wrong about case vibration not being the main issue. As soon as I popped the top cover up at the front of the case the noise pretty much disappeared. If I hold my ear close to it with the case open then I can just about hear a buzz, but it's virtually silent compared with how loud it gets once the case snaps back into place.

Some of the internal wiring was sticking up and touching the top of the case, so I've used a little electrical tape to hold it down. That didn't make much difference. Adding some more tape where the two halves of the case fit together improved things more. It's still audible sitting on my desk with the case back on, but from 3-4ft away I can't hear it.

I notice that the top shell of the case really rings and resonates if I flick it with a fingernail, so I think dampening it might make a difference after all. I'll have a play around and see if I can get it as quiet with the case on as it is when it's off.