WolfX700 Measurement of Topping L30 Headphone Amp

[JohnYang1997]

Even -30db would be fine with me. But if it's anything I can beg for, is please, no scratchy pots. I have an old pair of nonsense $99 Bose desktop speakers hanging around for almost 8 years that has one of of those knobs that function like an on/off switch along with volume. Still butter smoothe and just my favorite one to use (great resistance and all that, with no scratch at all). Meanwhile my 789, scratchy after a few months. Drives me insane.

First pots, and now more recently Toslink input connectors. Seems many basics are being blundered industry-wide by OEM's of these specific parts. Just getting worse all over the industry, so even if you wanted to get a better part for your next devices as a manufacturer, you're shit out of luck it seems.

Btw John, just a quick question, what's been going on in the DAC/AMP segment. I wanted to get a DX7 Pro (can't tell you how impatiently I waited for that thing), but man was I bummed about the output impedance panic Topping had for a while. Is there any plans for a slight revision with this in mind? I really like that Topping chose the ESS chip for that device, and I feel it's a great all-in-one. Any whispers about any future DAC/AMPs in the works or a revision to any existing? Can't imagine how all the advances recently made would go real well with a DX7 Pro V2 for example (solving output impedance being awesome, and getting us that 105db 50mV insane spec, and JUST MAYBE Bluetooth 5.2). That would just have my wallet flying out of my pocket instantly.

For the combo. Trying to plan for that. Nothing in the near future. I may not even be designing by the time.
L30, A50s, pre90, (another dac), (another one or two headamps), (a portable amp or portable dac/amp), (another dac), (a speaker amp), (another two speaker amps)... We are really busy. And combos are harder to design, more efforts for less performance. And will sell cheaper than two individual devices. Very non-ideal. I'm thinking about one combo with hybrid volume control. But no plan really.

 

[Matias]

I think we are going to hand select pots before using them. There seems to be higher defects that what I initially thought. If everything goes perfectly, we will see every unit from a90, l30, a50s to have pot 0.5dB matched from 0db down to -40db

Yes, I was going to suggest that. Maybe program a test in AP with +/- 0.5dB? An employee plugs the pot, starts the AP test, turns the pot from minimum to maximum, ends the test. If AP shows green light, pot goes to approved bucket and goes to the board manufacturer. If AP shows red, pot goes to rejected bucket for complaining with the pot maker later.
If automated should be somewhat fast to test them by the hundreds/thousands.

 

[JohnYang1997]

Yes, I was going to suggest that. Maybe program a test in AP with +/- 0.5dB? An employee plugs the pot, starts the AP test, turns the pot from minimum to maximum, ends the test. If AP shows green light, pot goes to approved bucket and goes to the board manufacturer. If AP shows red, pot goes to rejected bucket for complaining with the pot maker later.
If automated should be somewhat fast to test them by the hundreds/thousands.

It will of course be much more efficient than that.

 

[mt196]

It will of course be much more efficient than that.

Sorry to bother here John, but I had a curiosity. Which is the correct procedure to talk with topping about test/review samples? Or are you guys sending them only to people able to measure them like amirm and Wolf?

 

[JohnYang1997]

Sorry to bother here John, but I had a curiosity. Which is the correct procedure to talk with topping about test/review samples? Or are you guys sending them only to people able to measure them like amirm and Wolf?

I will make a special purpose board and some mechanical tools for this purpose. And it will not occupy the AP(even though there are three).

EDIT:
Oh you were talking about review samples.
Short answer no. Longer answer, the reviewers sent by Topping itself will be very very limited. Maybe a handful that's it. However you can ask distributors like shenzhenaudio, Apos, hifigo etc They may want to send a few more samples.

 

[WolfX-700]

@WolfX-700 headphone output impedance?

And RCA output impedance?

headphone output impedance 0.1R On the first page, there is the last measurement chart

RCA？ 20

 

[WolfX-700]

Even -30db would be fine with me.

 

[confucius_zero]

not sure why @WolfX-700 measurements don't show up in the "reviews" page. Aren't they as reliable as @amirm 's

 

[JohnYang1997]

not sure why @WolfX-700 measurements don't show up in the "reviews" page. Aren't they as reliable as @amirm 's

In the very beginning, it's pinned in the review page. Some stupid prick from else where thought it was Amir's measurements hence attacking Amir. Then it's taken from the review page to avoid misunderstanding. Makes no sense but that's the story.

 

[Matias]

View attachment 70642

Is this a better "golden" sample or what they plan to offer as guaranteed specification (channel imbalance +/- 0.5 from 0 to -30dB)?

 

[WolfX-700]

Is this a better "golden" sample or what they plan to offer as guaranteed specification (channel imbalance +/- 0.5 from 0 to -30dB)?

This sample shows that they are trying (and capable) to solve the problem of channel balance. The situation of retail products should be considered by the manufacturer.
Communication with manufacturers shows that they want to reach -38 +/-0.7. Or close to +/-0.5 at -40. If they are selected according to this standard, then I think -30 +/-0.5 is guaranteed...

 

[odyo]

For the combo. Trying to plan for that. Nothing in the near future. I may not even be designing by the time.
L30, A50s, pre90, (another dac), (another one or two headamps), (a portable amp or portable dac/amp), (another dac), (a speaker amp), (another two speaker amps)... We are really busy. And combos are harder to design, more efforts for less performance. And will sell cheaper than two individual devices. Very non-ideal. I'm thinking about one combo with hybrid volume control. But no plan really.

Yeah i really really want a product with DX7 pro case, screen, knob but E30+L30 inside without any extra like balanced, bluetooth etc...

 

[Labjr]

I'm wondering where the volume pot is in the circuit? If it's at the input, perhaps people could add their own stepped attenuator externally?

 

[JohnYang1997]

I'm wondering where the volume pot is in the circuit? If it's at the input, perhaps people could add their own stepped attenuator externally?

You can always add your own steppes attenuator externally. They are likely to degrade performance tho.

 

[Labjr]

You can always add your own steppes attenuator externally. They are likely to degrade performance tho.

Where in the circuit is the internal pot?

 

[JohnYang1997]

Where in the circuit is the internal pot?

Doesn't matter.

 

[mt196]

Is it possible to see with a multimeter, at a given volume, if L and R preamp channel are outputting the same power? How can it be done?

 

[confucius_zero]

it's taken from the review page to avoid misunderstanding.

darn I'd have to fav @WolfX-700 's page now too XD

 

[wowothanks]

I have seen some measurements-I am shocked and unbelievable about the measurement results.

I can’t say too much...but the measurement results I see are a triumphant victory for AHB2 at low listening levels...

In exaggerated words... that amplifier VS AHB2 is similar to AHB2 vs other amplifiers.


THD is lower than L30...

狼哥辛苦了，看你说要休息两个月，好好休息啊
借个楼问下现在国产还没有仿制BENCHMARK AHB这个功放的吗？感觉没啥性能不错性价比又高的功放啊

 

[iamwhoiam]

@JohnYang1997 - any news on release? Presumably some small delay due to pot matching?