Topping PA5 II Stereo Amplifier Review

[VVR]

Received my Pa5 II plus version on Monday. So far made a little comparison with LA90 and can't hear any difference. No scientific test of any kind, can't dB match levels or make it a blind-test though..

Question: Does it accept 5v from Topping E70 DAC? Or will it clip?

Balanced input of PA5 II is 2.6V and 5V is about 6db in the red. But you can use the volume control on the E70... Just keep it always lower than -6db.

Not sure where the volume control of PA5 II is located. Maybe you can compensate with the volume control for the very strong input. Don't know for sure though. I suspect it's buffered and not placed right at the input. If they say 2.6V then it's safe to assume that more than that will clip the amplifier.

 

[antcollinet]

Balanced input of PA5 II is 2.6V and 5V is about 6db in the red. But you can use the volume control on the E70... Just keep it always lower than -6db.

Not sure where the volume control of PA5 II is located. Maybe you can compensate with the volume control for the very strong input. Don't know for sure though. I suspect it's buffered and not placed right at the input. If they say 2.6V then it's safe to assume that more than that will clip the amplifier.

Normally an amp volume control will simply attenuate the input signal. So a 5V input with the volume turned down should be fine.

On the other. hand I'd normally put a limit on the output of the DAC so that turning the amp up full won't overdrive the speakers.

 

[VVR]

Normally an amp volume control will simply attenuate the input signal. So a 5V input with the volume turned down should be fine.

On the other. hand I'd normally put a limit on the output of the DAC so that turning the amp up full won't overdrive the speakers.

I agree. That's how I think too. And 2.6V seems to be the output power limit. With 19.2db gain this is 140W/4R. Nobody would need more.

But there is also small chance that more than 2.6V clips the amp at the very input. In that case the volume control will control already clipped signal. We just don't know if the input has any headroom and where the volume pot is inserted. Most of times is as you described, but what if an opamp buffers the input before the volume pot and runs at +/-5V supply, for example? We simply don't know the input circuit. I wish we had input headroom data and gain structure info. I suspect many people may use fixed DAC outputs and the amp volume pot. Is that okay with DACs outputting 5V?

 

[rongon]

I suspect many people may use fixed DAC outputs and the amp volume pot. Is that okay with DACs outputting 5V?

If the volume control on the amp's input is a standard potentiometer (variable resistor) then it's a resistive voltage divider consisting of an Rseries and an Rshunt. The attenuated signal output is taken from the pot's wiper to ground ("Output" in the schematic below).

When you turn down the volume, you're increasing the value of the R in series with the signal and reducing the value or R in parallel (shunting) the signal.
Turning down the volume control reduces the level (amplitude) of signal voltage seen at the wiper of the pot.
Long story short, I can't see any reason why turning down the volume control would not work to reduce your 5V source voltage to a suitable voltage coming from the volume control (pot's) wiper. That's what the volume control is there for.

One problem could be that the taper of the control won't allow you to make fine adjustments in volume, since you'll always being used it down near the start of its rotation (between 7 o'clock and 10 o'clock on the dial). The control might get 'too loud' too quickly. The solution would be to be careful not to turn it up too much too quickly.

The problem I have is that I have several analog sources playing into my amplifier. I have the S/PDIF output from my TV going to a DAC with balanced outputs going into a 1:1 transformer to prevent ground loop hum. (Any electrically grounded signal from my TV causes a bad ground loop in my listening room.) I also have the unbalanced output from my Raspberry Pi's DAC and the output from my phono preamp, all going to an input selector switch/'passive preamp' (with autoformer volume control). The levels from these three sources vary wildly. The TV balanced DAC output is double the amplitude of the unbalanced DAC, and the output from the phono preamp is a little higher in amplitude than from the unbalanced DAC. I had to put a 'trim pot' on the output of the TV balanced DAC to bring it down to the levels from the unbalanced DAC and the phono preamp. Hopefully you're using your DAC as the input selector switch, so you won't have that particular problem with level matching.

Most professional amplifiers will have a 'sensitivity' rating, stating how many volts (or millivolts) of input signal it takes to drive the amp to clipping (max power) into a specified load (4 ohms, 8 ohms, etc.).

For example, the manual for the Hafler P1000:

The 'input sensitivity range' spec probably means sensitivity varying with setting of input level controls (one per channel). So with balanced input, that would mean 277mV to full power into a 4 ohm load from the balanced input. Would that mean twice that (554mV) to full power into 4 ohms from the unbalanced input? (I think so.)

Do these small class D amps not have that specification listed?

 

[Rottmannash]

If the volume control on the amp's input is a standard potentiometer (variable resistor) then it's a resistive voltage divider consisting of an Rseries and an Rshunt. The attenuated signal output is taken from the pot's wiper to ground ("Output" in the schematic below).

When you turn down the volume, you're increasing the value of the R in series with the signal and reducing the value or R in parallel (shunting) the signal.
Turning down the volume control reduces the level (amplitude) of signal voltage seen at the wiper of the pot.
Long story short, I can't see any reason why turning down the volume control would not work to reduce your 5V source voltage to a suitable voltage coming from the volume control (pot's) wiper. That's what the volume control is there for.

One problem could be that the taper of the control won't allow you to make fine adjustments in volume, since you'll always being used it down near the start of its rotation (between 7 o'clock and 10 o'clock on the dial). The control might get 'too loud' too quickly. The solution would be to be careful not to turn it up too much too quickly.

The problem I have is that I have several analog sources playing into my amplifier. I have the S/PDIF output from my TV going to a DAC with balanced outputs going into a 1:1 transformer to prevent ground loop hum. (Any electrically grounded signal from my TV causes a bad ground loop in my listening room.) I also have the unbalanced output from my Raspberry Pi's DAC and the output from my phono preamp, all going to an input selector switch/'passive preamp' (with autoformer volume control). The levels from these three sources vary wildly. The TV balanced DAC output is double the amplitude of the unbalanced DAC, and the output from the phono preamp is a little higher in amplitude than from the unbalanced DAC. I had to put a 'trim pot' on the output of the TV balanced DAC to bring it down to the levels from the unbalanced DAC and the phono preamp. Hopefully you're using your DAC as the input selector switch, so you won't have that particular problem with level matching.

Most professional amplifiers will have a 'sensitivity' rating, stating how many volts (or millivolts) of input signal it takes to drive the amp to clipping (max power) into a specified load (4 ohms, 8 ohms, etc.).

For example, the manual for the Hafler P1000:
View attachment 312006

The 'input sensitivity range' spec probably means sensitivity varying with setting of input level controls (one per channel). So with balanced input, that would mean 277mV to full power into a 4 ohm load from the balanced input. Would that mean twice that (554mV) to full power into 4 ohms from the unbalanced input? (I think so.)

Do these small class D amps not have that specification listed?

Totally OT but related-when I listen to music in my cars with the 9038D dongle it causes distortion at any volume in one car and in the other no problem. I assumed one of the head units could accept a higher signal than the other. Am I crazy? I have to attenuate the 9038D on one car sometimes up to 10 dB to stop the distortion.

 

[rongon]

what if an opamp buffers the input before the volume pot and runs at +/-5V supply, for example?

Yes, that's spot on. Exactly.

If there's an input buffer circuit running with a 5V (DC) power supply rail, it might not be able to handle an unattenuated 5V input signal (AC). It could clip off the extra signal that it can't pass.

However, if the input buffer achieves unity gain through parallel negative feedback, that 5V AC signal input will be attenuated by the feedback ratio before it reaches the physical input terminal of the amplifier device. So in that case it will be able to handle a 5V output from the DAC, and provide 5V output.

Negative feedback is wacky stuff.

 

[antcollinet]

Yes, that's spot on. Exactly.

If there's an input buffer circuit running with a 5V (DC) power supply rail, it might not be able to handle an unattenuated 5V input signal (AC). It could clip off the extra signal that it can't pass.

However, if the input buffer achieves unity gain through parallel negative feedback, that 5V AC signal input will be attenuated by the feedback ratio before it reaches the physical input terminal of the amplifier device. So in that case it will be able to handle a 5V output from the DAC, and provide 5V output.

Negative feedback is wacky stuff.

I've never heard of an amp that runs input buffering on such a low power supply - do you know of one?

 

[VVR]

I've never heard of an amp that runs input buffering on such a low power supply - do you know of one?

Neither have I. But I also don't know how Topping did it. I'm too lazy to open the box again just to measure the opamps power pins voltages.
What I know for sure is that this S/N ratio can't be achieved with simple volume pot at the input. It must be some active form of volume control.
Too bad that E50 outputs 4V balanced and is supposed to work with its mate PA5 with 2.6V input. Not a match made in heaven but I understand why they did it.
On the other hand E70 has 4V and 5V output option to work with its mate PA7 that takes 4V. Seems better, although I don't get the 5V option. Why? Is it that much better dynamically vs 4V?

 

[Bleib]

Balanced input of PA5 II is 2.6V and 5V is about 6db in the red. But you can use the volume control on the E70... Just keep it always lower than -6db.

Not sure where the volume control of PA5 II is located. Maybe you can compensate with the volume control for the very strong input. Don't know for sure though. I suspect it's buffered and not placed right at the input. If they say 2.6V then it's safe to assume that more than that will clip the amplifier.

Might as well use it at 4v, as Topping themselves recommends d10 balanced which outputs 4.2v

 

[nagster]

I don't have a PA5II, but here is the input level vs. THD+N of the PA5.

Poll for Topping PA5 owners only please.

Currently suffering from a similar problem, sound on the right speaker cuts out sometimes, and i get random plopping sounds on occasion, i just switched the cables.( Left/Right).. Lets see what happcheck the transport units first. Yeh definitely check cables or if streaming see if it’s router...

www.audiosciencereview.com

If your PA5II has a similar configuration, I think you should be fine just turning the volume knob down so the PA5II's output doesn't clip.

 

[jmillar]

These fit into European wall power plugs. Rumour has it there is a 60Hz test tone at full power in there.

50 Hz. But it will overdrive your inputs. ;-)

 

[Eldus]

Totally OT but related-when I listen to music in my cars with the 9038D dongle it causes distortion at any volume in one car and in the other no problem. I assumed one of the head units could accept a higher signal than the other. Am I crazy? I have to attenuate the 9038D on one car sometimes up to 10 dB to stop the distortion.

Most cars have an ADC to apply panning, crossover and such. You probably are hitting the max volume of the converter.

 

[Rottmannash]

Most cars have an ADC to apply panning, crossover and such. You probably are hitting the max volume of the converter.

Ok. Thanks.

 

[john11]

Are there any feelings about changing the power supply for a higher voltage or higher current. Is the power supply low noise, is 4 amps enough or is more current going to give better sound. Is a higher or lower voltage going to make a difference

 

[antcollinet]

Are there any feelings about changing the power supply for a higher voltage or higher current. Is the power supply low noise, is 4 amps enough or is more current going to give better sound. Is a higher or lower voltage going to make a difference

The amp has been designed around the supplied PSU, and gives exceptionally good performance. Quite apart from the fact that more volts or current won't normally improve the sound unless the amp is being driven into clipping - a different supply may actually make things worse. Or higher volts or available amps may even damage it.

 

[daniboun]

Are there any feelings about changing the power supply for a higher voltage or higher current. Is the power supply low noise, is 4 amps enough or is more current going to give better sound. Is a higher or lower voltage going to make a difference

I disassembled the stock power PSU and it has a PFC circuit. It is of good quality, nothing to complain about there. I tried replacing it with a Connex LLC 36V/6.5A and another Morsun PFC. In the end, there is no difference perceptible to the ear. I didn't measure it though...
antcollinet is absolutely right, I think Topping designed the PA5 around the PSU and probably other key components

 

[Bleib]

Are there any feelings about changing the power supply for a higher voltage or higher current. Is the power supply low noise, is 4 amps enough or is more current going to give better sound. Is a higher or lower voltage going to make a difference

Likely the plus version is as good as it will get. It should be vastly better than human hearing so not much to be worried about here
Speakers, room, placement and recording quality will set the limitations, and well, your ears

 

[john11]

My PA5 II only came with a 3.2 amp psu not 4 amp as i thought it was going to.
Listening to it the PA5 sounds okay. I compared it against a class-A amp that i built myself, the class-A sounds better, more high frequency extension, more detailed, all round better in all respects. Only cost me about £40 to build, and has defeated amps many times its price, goes to show that the amp manufacturers out there are overcharging for their products which has been mentioned earlier in this thread. Topping is levelling the playing field, along with some of the hypex modules

 

[daniboun]

My PA5 II only came with a 3.2 amp psu not 4 amp as i thought it was going to.
Listening to it the PA5 sounds okay. I compared it against a class-A amp that i built myself, the class-A sounds better, more high frequency extension, more detailed, all round better in all respects. Only cost me about £40 to build, and has defeated amps many times its price, goes to show that the amp manufacturers out there are overcharging for their products which has been mentioned earlier in this thread. Topping is levelling the playing field, along with some of the hypex modules

Many users coming from Class A world think the same without considering any measurements.
I personnaly dont know a Class A amp into the top 10 ASR amps. Unless you have some measurements about your DIY Class A amp > I would say your ears are playing tricks on you

 

[Roland68]

My PA5 II only came with a 3.2 amp psu not 4 amp as i thought it was going to.
Listening to it the PA5 sounds okay. I compared it against a class-A amp that i built myself, the class-A sounds better, more high frequency extension, more detailed, all round better in all respects. Only cost me about £40 to build, and has defeated amps many times its price, goes to show that the amp manufacturers out there are overcharging for their products which has been mentioned earlier in this thread. Topping is levelling the playing field, along with some of the hypex modules

It would be nice if you let us know what kind of amplifier it is (kit, DIY publication, circuit diagram) and post a few pictures of the interior.
However, I strongly doubt the price quoted, for that you don't even get a transformer for a Class A amplifier, plus the costs for heat sinks, housing, power supply with rectifier and filter capacitors, power transistors, components and circuit boards, cabling, connections, etc. On top of that one should not forget the considerable time investment.

Maybe you can find one or more members in your area with whom you can do a simple blind test, that would definitely be interesting.

The 4 amp power supply is included with the Plus version, but for the price difference you can buy a good SMPS and wire it yourself.