WolfX700 Measurement of Topping A90 Headphone Amp

[Human Bass]

As explained earlier - D90 offers twice as much voltage via XLR out than RCA one and I do not want to have a possibility to kill my headphones by accidental switch to hi gain. I am looking for any hardware means of cutting down power output. One way is using SE instead of BAL headphone output. But I do not know what power difference is between them. Another idea is using RCA instead of XLR due to lower voltage. I do not think that XLR vs RCA matters in case of 0.5m connection. Provided that both are properly implemented and that was main goal of my original question. My current AMP offers 1W and this is fine for me. I would love to limit A90 to similar level. This way I would not need to worry about someone switching gain and I would have an AMP capable of driving harder headphones in case of future upgrade. I would love to know power output difference between SE and BAL. Also I would like to make sure if I am correct that halving input voltage leads to cutting down output power by 75% - not sure about it.

The amp wont suddenly become a driver exploder because its connected by xlr to the dac. Relax man.

 

[Yuno]

I think you skipped my first post about reason of this question. I know that nothing wrong happens when I listen to music at comfortable level. What I am concerned about are children. My headphone set is easily accessible on my desk and I want to cut power output down so that even if they switch gain to high and turn the volume to max, nothing wrong happens. Anyway, I think I will try with RCA and SE output and test it when A90 will be available.

If you want to lower the gain you can just do so on D90. Decrease volume of input and there you have it. Obviously if you are worried about kids messing with volume, they can just very well increase D90 volume back to it's max position. I don't think there is a perfect solution for this, child-proof audio devices are not really a thing.

 

[dmac6419]

If you want to lower the gain you can just do so on D90. Decrease volume of input and there you have it. Obviously if you are worried about kids messing with volume, they can just very well increase D90 volume back to it's max position. I don't think there is a perfect solution for this, child-proof audio devices are not really a thing.

child-proof audio devices are not really a thing,when i was growing up they were or you got a xxx whooping

 

[VeerK]

child-proof audio devices are not really a thing,when i was growing up they were or you got a xxx whooping

I have my own office, but if I didn’t and was worried about child-proofing my D90+A90, I’d invest in some kind of plexiglass around the stack.

 

[Sephula]

Bullet-proof glass, with lazers and body heat sensors, but an air vent directly above it.

 

[spiritofjerry]

My only complaint with these units is the inclusion of preamp controls but not a dedicated line out. Not everyone uses active desktop speakers. In fact, many of us use regular old speaker amplifiers feeding bookshelf speakers.

Is it that difficult to add the option for line or pre out?

 

[JohnYang1997]

My only complaint with these units is the inclusion of preamp controls but not a dedicated line out. Not everyone uses active desktop speakers. In fact, many of us use regular old speaker amplifiers feeding bookshelf speakers.

Is it that difficult to add the option for line or pre out?

What do you mean by that? Is line out just a pass through of DAC signal? Or do you want a buffered signal?

 

[LostOne___]

Well..

https://shenzhenaudio.com/collections/all/products/topping-a90-headpone-amplifier

(posting just for giggles...)

 

[Yuno]

What do you mean by that? Is line out just a pass through of DAC signal? Or do you want a buffered signal?

I'm pretty sure it's pass. My aune x1s does that, passes full volume signal by RCA at all times regardless of HP potentiometer position. Good if you want to send it to AMP where you control volume, useless if you use active speakers (requires pre-amp or control with speaker volume itself).
Side-note, I think this would make things much more complex to implement with device like this. If you added 3 lever position where one is HP, second pre and third is line-out then I can guarantee people would be upset that they accidentally switch to line out and blast their eardrums at full volume. That was the case with dx3 pro and in the end topping had to implement way around it that would be much harder to do with amp that is analogue controlled.

Unrelated but I'm curious - what is the difference between off switch on the front and the one on the back on A90? I think I asked this question long time ago and got no answer. Is front one just mute while back switch is full off?

 

[JohnYang1997]

I'm pretty sure it's pass. My aune x1s does that, passes full volume signal by RCA at all times regardless of HP potentiometer position. Good if you want to send it to AMP where you control volume, useless if you use active speakers (requires pre-amp or control with speaker volume itself).
Side-note, I think this would make things much more complex to implement with device like this. If you added 3 lever position where one is HP, second pre and third is line-out then I can guarantee people would be upset that they accidentally switch to line out and blast their ear-drums at full volume. That was the case with dx3 pro and in the end topping had to implement way around it that would be much harder to do with amp that is analogue controlled.

Unrelated but I'm curious - what is the difference between off switch on the front and the one on the back on A90? I think I asked this question long time ago and got no answer. Is front one just mute while back switch is full off?

Switching on off on the front allows safe on off sequence without any surge to the headphones. Switching on off the power on the back may damage the headphones. At least you may hear a thump. Plus it's way more convenient to be able to turn off at the front.

The pass through function is literally a switch. And I don't see any benefit over just maxing out the volume. If you really need it, just use a switch really. Or separated/second output from your DAC.

 

[spiritofjerry]

Switching on off on the front allows safe on off sequence without any surge to the headphones. Switching on off the power on the back may damage the headphones. At least you may hear a thump. Plus it's way more convenient to be able to turn off at the front.

The pass through function is literally a switch. And I don't see any benefit over just maxing out the volume. If you really need it, just use a switch really. Or separated/second output from your DAC.

Pass through is indeed what I meant. THX 789 does this. The problem with just maxing the volume is that if you forget to lower it before switching back to headphone out, you risk blowing your drivers.

AudioGD products got this one implement right. The ability to switch between pre and line is hard to find outside more expensive units. Frankly, line has always been the industry standard for output. It's these little desktop units that assume everyone uses active monitors that has negated that standard.

 

[JohnYang1997]

Pass through is indeed what I meant. THX 789 does this. The problem with just maxing the volume is that if you forget to lower it before switching back to headphone out, you risk blowing your drivers.

AudioGD products got this one implement right. The ability to switch between pre and line is hard to find outside more expensive units. Frankly, line has always been the industry standard for output. It's these little desktop units that assume everyone uses active monitors that has negated that standard.

Just get a switch bro...

 

[mt196]

Exectly, just get a switch and you will solve your problem. I feel that having a pass through is something less than having a true preamp in products, so I totally agree with topping choice, if you don't want to control the volume, just use a switch

 

[spiritofjerry]

Just get a switch bro...

That's exactly what I've been asking for, eh Just add it to the product, bro.

Thing is, when you introduce an analog pot into the signal as pre, you are already adding imbalance to the signal prior to sending to another potentiometer.

 

[JohnYang1997]

Way to wave off my point. I could say the same to people using active monitors. "Just get a potentiometer bro."

Thing is, when you introduce an analog pot into the signal as pre, you are already adding imbalance to the signal prior to sending to another potentiometer.

That's very different. A simple potentiometer is not going to have the performance of A90. Not even close. You get a trade off between, channel imbalance, channel crosstalk, output impedance, input impedance (loading previous stage). Operation is very different too. You can get a dedicated preamp that's for sure. But it's nothing like a pot.
Similarly, when I mean switch I didn't mean a component switch but an actual switcher with chassis and everything. It's way cheaper than A90 and does the job. You can get some of those like A B switch, splitter. They are designed to do the very same thing. There's no meaningful measurable difference between switches. But preamps can be very different.
Plus you can use the preamp to control the volume regardless of whether the following stage having volume control or not. It's a much superior preamp is majority of preamps on the market.

 

[spiritofjerry]

That's very different. A simple potentiometer is not going to have the performance of A90. Not even close. You get a trade off between, channel imbalance, channel crosstalk, output impedance, input impedance (loading previous stage). Operation is very different too. You can get a dedicated preamp that's for sure. But it's nothing like a pot.
Similarly, when I mean switch I didn't mean a component switch but an actual switcher with chassis and everything. It's way cheaper than A90 and does the job. You can get some of those like A B switch, splitter. They are designed to do the very same thing. There's no meaningful measurable difference between switches. But preamps can be very different.
Plus you can use the preamp to control the volume regardless of whether the following stage having volume control or not. It's a much superior preamp is majority of preamps on the market.

Again, I don't see a need to go out and buy (or let's be real, make) a switch when it could be easily integrated from the unit.

I'm not knocking the preamp in any way, just showing that a simple line pass through is indeed wanted by some members of the community, and the pre function actually gets in the way

 

[JohnYang1997]

Again, I don't see a need to go out and buy (or let's be real, make) a switch when it could be easily integrated from the unit.

I'm not knocking the preamp in any way, just showing that a simple line pass through is indeed wanted by some members of the community, and the pre function actually gets in the way

I can see that this is important for some people. And yes it will be considered in the future. Like l30 the switch between headphone out and preamo is changed from plug and unplug the headphone to a simple toggle switch.

 

[mt196]

Again, I don't see a need to go out and buy (or let's be real, make) a switch when it could be easily integrated from the unit.

I'm not knocking the preamp in any way, just showing that a simple line pass-through is indeed wanted by some members of the community, and the pre-function actually gets in the way

I think that the pass-through can be easily achieved putting the volume to max, what cannot be easily achieved is the preamp function, so if I must choose between the two I prefer a product with preamp function and then arrange it someway if I just need a passthrough.

Ideally a product should have the two features together, but if I must choose, I really much prefer to have a built-in preamp than a passthrough (since passthrough is easier to achieve in other ways)

 

[JohnYang1997]

I can definitely see it being implemented in the future so no hard feelings.

 

[Veri]

I think that the pass-through can be easily achieved putting the volume to max, what cannot be easily achieved is the preamp function, so if I must choose between the two I prefer a product with preamp function and then arrange it someway if I just need a passthrough.

Ideally a product should have the two features together, but if I must choose, I really much prefer to have a built-in preamp than a passthrough (since passthrough is easier to achieve in other ways)

Max volume pre-amp should be totally transparent on this amp in any case. I don't see the problem here.