New Amp to Replace Topping Pa5

[Doodski]

I’m fairly certain if I’d been bitten by a faulty Topping product, I’d not be in any rush to replace it with another Topping option. Even though there is nothing to say that their other offerings have any issues. I’d personally choose Buckeye. The level of support he offers based on what I read on this site is commendable.

Me too as per choosing Bukecye Amps as the successor to the flaky Topping unit.

 

[mdsimon2]

OK, but how does a 2 channel preamp fix that problem?

It doesn't which is why I don't quite understand the preamp discussion unless the OP has an analog x-over downstream of the DAC, although that would somewhat defeat the purpose of having a 4 channel DAC.

The OP suggested the LA90 as a solution, but it doesn't have any line level output.

As the OP is starting from a 4 channel DAC any stereo amplifier will be fine, even if they do not have a line out.

The other thing I don't get here is the assumption that low gain at the power amp stage necessarily means low noise.

Idle noise is a function of the amp stage. Sticking a preamp or buffer to adjust signal level in front of the stage that creates the noise doesn't reduce it.

If inserting a -10 dB attenuator in front of the power amp decreases noise, then the noise is coming from the upstream device.

What am I missing here?

Assuming you care about total system noise gain absolutely matters as it determines how much the noise from the upstream device is multiplied. While the MOTU M4 is relatively low noise it is not SOTA so it makes sense to pay attention to gain. If you run the numbers with both the PA5 and NC252MP amplified DAC noise is the biggest contributor to system noise, this is why the comparison of amplifier residual noise that @NTK posted earlier doesn't tell the whole story.

Michael

 

[Talisman]

https://audiosciencereview.com/foru...phonics-da-s250nc-dac-power-amp-review.44379/
Recently tested, cheap, with an excellent hypex amplifier module, unfortunately it has no analog inputs but only digital inputs

 

[sejarzo]

It doesn't which is why I don't quite understand the preamp discussion unless the OP has an analog x-over downstream of the DAC, although that would somewhat defeat the purpose of having a 4 channel DAC.



As the OP is starting from a 4 channel DAC any stereo amplifier will be fine, even if they do not have a line out.



Assuming you care about total system noise gain absolutely matters as it determines how much the noise from the upstream device is multiplied. While the MOTU M4 is relatively low noise it is not SOTA so it makes sense to pay attention to gain. If you run the numbers with both the PA5 and NC252MP amplified DAC noise is the biggest contributor to system noise, this is why the comparison of amplifier residual noise that @NTK posted earlier doesn't tell the whole story.

Michael

So regarding the preamp, you have the same question I do. Unsure what that's supposed to do when there is more than enough gain in the system already.

My comment about the LA90 was with respect to interfacing with a sub and providing a single volume control, which as you noted, the M4 can't do. The description of the signal chain by the OP doesn't address how that is accomplished.

My experience has been that power amps have always been the source of more speaker hiss than any of the upstream components, at least for the past 20 years or so. Haven't found a noise-only spec for the M4, only that Motu specs THD+N on the balanced outputs at -111 dB which matches Amir's measured SINAD. I've run 3 different power amps between a Topping E30 with a similar SINAD and my speakers, and the tweeter hiss was minimal and no different than when I put shorting plugs on the input of the power amps.

 

[BoredErica]

The idle noise of PA5 from Topping's spec is 16 μV (A-weighted).


The idle noise from the Hypex NC252MP is 30 μV (unweighted, which will give a worse number than A-weighted). Its noise is therefore about 6 dB (worst case) higher than the PA5. The 6 dB number also corresponds to the double distance sound attenuation. Therefore, for example, if you can't hear noise from the PA5 at 4 inches, you shouldn't hear noise from the NC252MP at 8 inches.

Hi again!
Yes, this was my understanding. The final noise output should be approx 6db worse. Well, I got that number from looking at the gain. 25.5-19.1 = 6.4db. And if what Mdsimon said last time still holds true here (I think it does), the M4's noise after being mangified by 25.5db gain dominates the amp's own noise. And so increase in noise should in theory be approx 6.4db.

My best friend has a new pa5 w/ Kef R3 and says they can hear noise few inches away w/ Motu UL5! Not entirely sure if he's hearing ghosts or if his hearing is really that acute.

I would not service the unit for Topping either. Topping should service them and do it properly and no mickey mouse club stuff!

You are a wealth of info on most all days so don't go hard on yourself.

I told my mom what happened and she tells me never to buy Topping ever again and sprint for another brand lol. To me there is some difference between LA90 and PA7 though. LA90 has been out for over a year now with no angry thread of people. It's the LA90 Discrete now though and there isn't good visibility on what happens after the first year or two. But yes, the idea of getting another Topping amp in particular is not that appealing. To me, the horrendous customer support ended up being worse than the defect itself. If I got a partial refund (which I might've if I harrassed Hifigo when warranty claim was still on them TBF) I might feel differently but I didn't.

OK, but how does a 2 channel preamp fix that problem?

The OP suggested the LA90 as a solution, but it doesn't have any line level output.

So regarding the preamp, you have the same question I do. Unsure what that's supposed to do when there is more than enough gain in the system already.

My comment about the LA90 was with respect to interfacing with a sub and providing a single volume control, which as you noted, the M4 can't do. The description of the signal chain by the OP doesn't address how that is accomplished.

My experience has been that power amps have always been the source of more speaker hiss than any of the upstream components, at least for the past 20 years or so. Haven't found a noise-only spec for the M4, only that Motu specs THD+N on the balanced outputs at -111 dB which matches Amir's measured SINAD. I've run 3 different power amps between a Topping E30 with a similar SINAD and my speakers, and the tweeter hiss was minimal and no different than when I put shorting plugs on the input of the power amps.

Thanks to Mdsimon for explaining everything while I was away better than I can. My understanding is based on this post:

The rule of thumb is to put a much of the gain as possible to the front of the chain, and therefore as little gain as possible in the speaker amp (just enough to reach your desired listening level).

You can solve the problem by placing an analog volume control (can be a passive "pre-amp" or one of the headphone/pre amps) between the speaker amp and source. The combination effectively gives you adjustable gain for the speaker amp, so you don't have to run it at full gain all the time.

I thought that I could just use a 2 channel preamp that reduces the level going from M4 -> Amp and fix the noise that could only be heard from mains rather than the sub. So I turn the preamp knob down some and would have to turn the volume on back of my sub some as well to compensate. Am I totally wrong here? Preamps weren't discussed in depth last time so I don't know as much. If my power amp only operates at high gain, then I get around this with an amp with adjustable gain or get a preamp. And an amp with adjustable gain is hard to find especially ignoring Topping.

I think it is highly unlikely that you have audible hiss with a NC252MP. I'd get a Buckeye or Audiophonics NC252MP and see how it goes. If it is too noisy get a 10 dB XLR attenuator. That will give noise performance slightly better than the PA5 and you will still be able to drive the NC252MP to full power.

Michael

Never heard of XLR attenuators. Do I just look em' up on Amazon? They say stuff like "-20dB at 300ohm" and I dunno how to relate that to a speaker which aren't 300ohm.

Sounds like you have a preferred budget of < 500$ USD? Any other preference, like small form?
How does something like the Sabaj A20a fit?
Newer designs like these don't have much track record yet (doesn't mean there will be problems) so your 10yr trouble-free wish is tricky to fulfill.
Plenty of 'traditional' integrated amps but they are less likely to offer balanced inputs.
Do you need the Motu ... the AUDIOPHONICS DA-S125NC measures pretty well (also new though)

https://audiosciencereview.com/foru...phonics-da-s250nc-dac-power-amp-review.44379/
Recently tested, cheap, with an excellent hypex amplifier module, unfortunately it has no analog inputs but only digital inputs

Thanks for the suggestions. TBH, I'm not sure what digital input means. There's just some cables that go out of the M4 dac and goes into the amp. I assume that's analog as most as in this case?

===
The reason why I didn't list the new Ncx Buckeyes was because the Purifi stuff have been out for far longer and measurements don't show some big lead the Ncx has above the Purifi. Pricing are identical. Features look the same.

 

[mdsimon2]

So regarding the preamp, you have the same question I do. Unsure what that's supposed to do when there is more than enough gain in the system already.

My comment about the LA90 was with respect to interfacing with a sub and providing a single volume control, which as you noted, the M4 can't do. The description of the signal chain by the OP doesn't address how that is accomplished.

My experience has been that power amps have always been the source of more speaker hiss than any of the upstream components, at least for the past 20 years or so. Haven't found a noise-only spec for the M4, only that Motu specs THD+N on the balanced outputs at -111 dB which matches Amir's measured SINAD. I've run 3 different power amps between a Topping E30 with a similar SINAD and my speakers, and the tweeter hiss was minimal and no different than when I put shorting plugs on the input of the power amps.

Amir got 118 dB DR at 5.25 V for the M4. This is 5.25 x 10^(-118/20) = 6.6 uV residual noise. I've measured my M4 with a Cosmos ADC and got 6.2 uV.



Multiplying that 6.2 uV by 25.6 dB gain for the NC252MP gives 6.2 x 10^(25.6/20) = 118 uV. Although the residual noise of the NC252MP is spec'd at 30 uV real world 5 W in 4 ohm DR is typically around 100 dB which is 45 uV, so even then the amplified DAC noise governs system noise.

As the OP is starting from a computer I assume they are using software volume control.

Michael

 

[sejarzo]

Welp, that last post from the OP leaves me even more confused about how the system is set up.

The gain of a power amp is fixed--it's not variable.

@BoredErica...do you adjust your listening volume solely with software on the computer?

 

[mdsimon2]

Never heard of XLR attenuators. Do I just look em' up on Amazon? They say stuff like "-20dB at 300ohm" and I dunno how to relate that to a speaker which aren't 300ohm.

This is what I had in mind -> https://www.parts-express.com/Inline-XLR-Attenuator-Pad-10dB-240-412?quantity=1. I have the 20 dB version that I use to make lower power amplifier measurements and it works well. The idea behind the XLR attenuator is that it will reduce both signal and noise equally, unlike digital volume control which will reduce only signal level and not noise. You can somewhat think of it like lowering amplifier gain by 10 dB.

Michael

 

[Timcognito]

How about 120 w/channel, Dirac DSP, Roon endpoint, Sub out, Streaming, Chromecast built-in, Apple AirPlay, headphone output, parametric equalization, adjustable high-pass/low-pass crossover filters. Volumio music player, and internet radio. Plus great specs and test results linked at the top. $1500

SoundStage! Hi-Fi | SoundStageHiFi.com - miniDSP SHD Power Integrated Amplifier-DAC

www.soundstagehifi.com

 

[BoredErica]

Welp, that last post from the OP leaves me even more confused about how the system is set up.

The gain of a power amp is fixed--it's not variable.

@BoredErica...do you adjust your listening volume solely with software on the computer?

Yes, gain of power amp is fixed. If I want 20db gain for example and I have power amp w/ 25db gain, I thought I could insert a preamp in between dac and amp and attenuate the signal so after 25db gain, it's as if I had 20db gain without preamp. So in practice it's as if I had an amp with gain settings. Am I hallucinating here? lol

For adjusting listening volume, either by dragging a slider on my computer or hooking up USB volume knob one day that also controls volume digitally. It should be like dragging a slider but better tactile experience, methinks. I will try to clarify in OP in just a second.

This is what I had in mind -> https://www.parts-express.com/Inline-XLR-Attenuator-Pad-10dB-240-412?quantity=1. I have the 20 dB version that I use to make lower power amplifier measurements and it works well. The idea behind the XLR attenuator is that it will reduce both signal and noise equally, unlike digital volume control which will reduce only signal level and not noise. You can somewhat think of it like lowering amplifier gain by 10 dB.

This feels like a cheaper solution to a preamp. It loses ability to change attenuation on the fly and adds bulk going into the amp but in exchange is far cheaper and is hard to fail. How long is it? The specs give no indication of length. I guess it just attenuates and there are no weird side effects. (FR change?) I would need new cables since mine are TRS for Pa5 or TRS->XLR converter. Kind of leaning towards the cables since with the converter I'd have 2 things sticking out behind the amp.

Cost is $31 shipped.

How about 120 w/channel, Dirac DSP, Roon endpoint, Sub out, Streaming, Chromecast built-in, Apple AirPlay, headphone output, parametric equalization, adjustable high-pass/low-pass crossover filters. Volumio music player, and internet radio. Plus great specs and test results linked at the top. $1500

SoundStage! Hi-Fi | SoundStageHiFi.com - miniDSP SHD Power Integrated Amplifier-DAC

www.soundstagehifi.com

Cool option, but I don't need those features currently I think. $1500 is more expensive than Purifi.

 

[mdsimon2]

The specs give no indication of length. I guess it just attenuates and there are no weird side effects. (FR change?) I would need new cables since mine are TRS for Pa5 or TRS->XLR converter. Kind of leaning towards the cables since with the converter I'd have 2 things sticking out behind the amp.

They are kind of long. The one I have is about 4". I don't think I've actually measured frequency response with it as I've typically just run FFTs, but I can do that. In general I have not observed any frequency response changes when using voltage dividers which is basically what the XLR attenuator is.

I agree that using a TRS to XLR cable is a better solution than the a TRS to XLR converter.

Michael

 

[sejarzo]

A preamp, historically speaking in consumer audio, was used to provide additional gain between low level analog sources and power amps. The term "preamp" always implied an active preamp, not a "passive preamp" which is essentially just a variable attenuator and no active gain stages. Those only came into fashion when consumer CD players and DACs effectively standardized on 2Vrms output for a 0 dBFS digital input, which meant virtually any consumer (unbalanced) power amp could be driven into clipping without any added gain.

Why would you want to change attenuation on the fly between the M4 and a power amp? You want to set that and leave it if you are going to do all your volume control on the computer.

 

[BoredErica]

They are kind of long. The one I have is about 4". I don't think I've actually measured frequency response with it as I've typically just run FFTs, but I can do that. In general I have not observed any frequency response changes when using voltage dividers which is basically what the XLR attenuator is.

I agree that using a TRS to XLR cable is a better solution than the a TRS to XLR converter.

I think it is highly unlikely that you have audible hiss with a NC252MP. I'd get a Buckeye or Audiophonics NC252MP and see how it goes. If it is too noisy get a 10 dB XLR attenuator. That will give noise performance slightly better than the PA5 and you will still be able to drive the NC252MP to full power.

Ok, thanks for the suggestion. I overspent on $45 for 2 1 foot long custom TRS->TRS cables with the right length, color, connectors I wanted that I might want to replace with the same specs except w/ XLR on one end. But that is my fault. As for measuring the attenuators, I don't want to trouble you further especially since it's not a given the nc252mp will even need the attenuators in the first place. Maybe if it comes to it and you're willing we can have that conversation.

I think the main benefit of Purifi would be that it has the least amount of bulk. No chance of 4in attenuators behind amp, no extra preamp. It's clean. But it's also $500 more. xD And if nc252mp actually ends up not needing attenuation then it's the same thing but cheaper.

When you said you find it highly unlikely that I will have audible hiss w/ NC252mp, do you mean at listening position or ear next to tweeter? I read posts where people say there's no noise ear to tweeter for their nc252mp, 1 person who said they can definitely hear noise even bit further away, and some random posts saying hearing noise ear at tweeter is almost inevitable, and one person saying that's not true.

A preamp, historically speaking in consumer audio, was used to provide additional gain between low level analog sources and power amps. The term "preamp" always implied an active preamp, not a "passive preamp" which is essentially just a variable attenuator and no active gain stages. Those only came into fashion when consumer CD players and DACs effectively standardized on 2Vrms output for a 0 dBFS digital input, which meant virtually any consumer (unbalanced) power amp could be driven into clipping without any added gain.

Why would you want to change attenuation on the fly between the M4 and a power amp? You want to set that and leave it if you are going to do all your volume control on the computer.

I don't intend to change attenuation on the fly between M4 and power amp. I meant that with a preamp I'm not limited to -10db attenuation. If I decide -15db is even better, I can do that and stick with it. With XLR attenuator, I pick attenuation amount ahead of time. It's not a huge difference on that front as -10db attenuation ought to be more than enough.

In practice the main upside of preamp I can think of right now is it's not as bulky behind the amp.

 

[sejarzo]

I don't intend to change attenuation on the fly between M4 and power amp. I meant that with a preamp I'm not limited to -10db attenuation. If I decide -15db is even better, I can do that and stick with it. With XLR attenuator, I pick attenuation amount ahead of time. It's not a huge difference on that front as -10db attenuation ought to be more than enough.

In practice the main upside of preamp I can think of right now is it's not as bulky behind the amp.

An active preamp has gain stages, and gain stages always add some noise. If your concern is absolute minimization of noise, then you don't want to use an active preamp if you are only going to attenuate the signal from the M4. An active preamp makes sense only if you have to drive long lines and avoid signal loss.

The attenuators are simple voltage dividers. They don't add noise other than the extremely small thermal noise of the resistors. The principle is just like a volume pot on the input of an integrated amp, other than the voltage division is fixed at the point between the fixed resistor values, rather than variable was the wiper in a pot moves along the resistive element.

https://www.electronics-tutorials.ws/attenuators/attenuator.html

Is your concern re noise simply that you don't want to hear hiss from the speakers when no music is playing?

 

[BoredErica]

An active preamp has gain stages, and gain stages always add some noise. If your concern is absolute minimization of noise, then you don't want to use an active preamp if you are only going to attenuate the signal from the M4. An active preamp makes sense only if you have to drive long lines and avoid signal loss.

The attenuators are simple voltage dividers. They don't add noise other than the extremely small thermal noise of the resistors. The principle is just like a volume pot on the input of an integrated amp, other than the voltage division is fixed at the point between the fixed resistor values, rather than variable was the wiper in a pot moves along the resistive element.

https://www.electronics-tutorials.ws/attenuators/attenuator.html

Is your concern re noise simply that you don't want to hear hiss from the speakers when no music is playing?

Yes. There are times when I work in silence in a silent room in front of my computer and I get really upset if I can hear noise, including from my speakers. I spent a ton of money on a water cooling loop for my computer to silence it.

 

[pjug]

Amir got 118 dB DR at 5.25 V for the M4. This is 5.25 x 10^(-118/20) = 6.6 uV residual noise. I've measured my M4 with a Cosmos ADC and got 6.2 uV.

View attachment 283949

Multiplying that 6.2 uV by 25.6 dB gain for the NC252MP gives 6.2 x 10^(25.6/20) = 118 uV. Although the residual noise of the NC252MP is spec'd at 30 uV real world 5 W in 4 ohm DR is typically around 100 dB which is 45 uV, so even then the amplified DAC noise governs system noise.

As the OP is starting from a computer I assume they are using software volume control.

Michael

I would just get the amp you want and not worry too much about noise from too much gain, until you try it. Really I wouldn't expect <150uV noise to be a problem with 83dB speakers. If you find noise does bother you can get something for attenuation later.

 

[JeremyFife]

Yes. There are times when I work in silence in a silent room in front of my computer and I get really upset if I can hear noise, including from my speakers. I spent a ton of money on a water cooling loop for my computer to silence it.

Some people are extremely sensitive to noise, I get that - simplest solution would be to turn your amp off when you need silence... cheapest too ...

 

[BoredErica]

Alright, my current plan is Buckeye nc252mp. But have to decide if I want it in white powder coat.

 

[Doodski]

Alright, my current plan is Buckeye nc252mp. But have to decide if I want it in white powder coat.

Anodized platinum green is a beautiful finish. I've had platinum green stereo gear before and it's a real conversation piece. Hmmz... It seems the platinum green anodizing is not available today. Good choice of the selection of a amp.

Buckeye Amps

Buckeye Amps utilizes the most advanced audio amplifier technologies available. Authorized seller for Hypex and Purifi Class D amplifiers. Based in the US. Free shipping and worldwide service!

www.buckeyeamp.com

 

[BoredErica]

Anodized platinum green is a beautiful finish. I've had platinum green stereo gear before and it's a real conversation piece. Hmmz... It seems the platinum green anodizing is not available today. Good choice of the selection of a amp.

Buckeye Amps

Buckeye Amps utilizes the most advanced audio amplifier technologies available. Authorized seller for Hypex and Purifi Class D amplifiers. Based in the US. Free shipping and worldwide service!

www.buckeyeamp.com

I'm thinking of white. Currently, amp and dac get put away on a shelf where they won't be visible. Slowly over a good number of years, I'd like to transform computer room into a white and pink room with some copper accents. Rose gold is my favorite color and that's not an option, but that's not a surprise. I think copper anodizing is cool too.

I'm assuming it would be a bad idea for Buckeye nc252mp to be put in a close cabinet due to lack of airflow/heat? Trying to think if there's a practical way to keep the amp out of sight in a TV stand or shelf. If it's visible I think looks matter more and I'm more willing to pay for powder coat. Then I start thinking, if I procrastinate overhauling the room too much, looks of the case won't matter since they'll remain on this shelf where I can't see it. What if by the time I get a TV stand and reorganize my room the Buckeye is already through half its lifespan and I'm paying for powder coat I'd only see for the latter half of its lifespan? Do I get TRS->XLR converter or do I get new cables?

oh god I am overthinking this again.

From what I have seen, sales on Buckeye amps have been for more expensive amps than 2ch nc252mp, so based on the past, I doubt there will be much in it for waiting unless I'm praying for PA5 II lol. But I've already suffered long enough. Don't want to wait another 6 months.