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The Stax Thread III
Apr 11, 2023 at 1:43 AM Post #23,491 of 25,602
Roukii said:
https://www.tpdz.net/productinfo/995112.html
their electrostatic amp specs are really impressive.
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I'd be a bit wary of trusting those measurements as representative of performance with actual electrostatic headphones. Electrostats are very different loads compared to regular headphones, and it looks like they just slapped a really large resistor in front of an APx unit to do the measurements. From the dashboard 1KHz measurement, it seems they're reducing the output voltage to 1/10th of actual before feeding it into the APx.

Also, we don't know its output current. Because electrostatic headphones have a very variable impedance curve that's high in the middle but low at the edges (sub-bass and upper treble), the amp needs enough current to ensure that it can sustain a given voltage swing not just at 1 KHz, but at 20 Hz and 20 KHz too. Does that FR graph take those impedance characteristics into account? No indication either way is given.

Finally, this is something we will need to open up the amp to check, but what are the safety features in the amp? Does it have measures to prevent damage to the headphones? I've seen mention that Stax Pro bias headphones can only go up to ~470 Vrms before the stators (or diaphragms) get damaged from the voltage. Given that the Topping L30 has killed headphones in the past, I think this is a valid concern. And with the very high voltages of electrostatic amps, this is also a human safety issue. I'm sure the Stax Mafia will have fun with the teardown.

All of these concerns aside, at $400, this amp basically wins the starter estat amp competition by default (as long as it doesn't kill headphones). No other in-production amp comes close to this price point. The only amps remotely close to this price point would have been the SRM-252 series, which is now discontinued. I hope this thing is good, because I've heard people say that the price of estat amps is the main barrier to them exploring this type of headphone.
 
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Apr 11, 2023 at 2:32 AM Post #23,492 of 25,602
399$? Why spending that much? I just got a Blue Hawaii for just 120 Baht :wink:

Btw, I tried hard, but even with this drink I could not find a new innovative amp design, lol

Greetings from Thailand :)

(Sorry for spamming, could not resist)
 

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Apr 11, 2023 at 3:59 AM Post #23,493 of 25,602
And now they're poking their claws into the estats territory. At $399 the pricing is worth an orgasm or two but given how most of their amps sound (compressed and lifeless, at least to me), I have my doubts.
 
Apr 11, 2023 at 7:58 AM Post #23,494 of 25,602
for those that don't already know, the topping amp is highly similar to the koss amp. opamp front end driving stacked transistors. low power class AB.
good deal for a cheap amp with a stax jack. no way to get those distortion numbers without oodles of open loop gain and lots of feedback.
 
Apr 11, 2023 at 9:54 AM Post #23,496 of 25,602
kevin gilmore said:
for those that don't already know, the topping amp is highly similar to the koss amp. opamp front end driving stacked transistors. low power class AB.
good deal for a cheap amp with a stax jack. no way to get those distortion numbers without oodles of open loop gain and lots of feedback.
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So you're saying I should get rid of my @kevin gilmore Grounded Grid and replace it with this???
 
Apr 11, 2023 at 10:44 AM Post #23,498 of 25,602
some sources said that topping electrostatic amp were opamp feeding step-up transformers. The official website does not specify the frequency of its maximum output. and we all know that when driving capacitive loads, the performance of most electrostatic amplifiers is suffered from the current limit of VAS at high frequency and very high voltage swing. so I very much hope that there will be more detailed test results from third party to allow those xtreme performance estat enthusiasts to evaluate the design.:muscle:
 
Apr 11, 2023 at 11:01 AM Post #23,499 of 25,602
srm212,252 etc are 6 volts 1 amp. So 6 watts
koss is 9 volts 1 amp. So 9 watts.
topping is 15 volts 1 amp. So 15 watts
.............
carbon cc is 125 watts
T2 is 225 watts
megatronxxl is 325 watts

no way an opamp driving transformers is going to be able to do .0008% thd

amir (incorrectly) measured koss at .01%
i (correctly) measured koss at .005% which is the limit of my equipment.
(i'm waiting on the new quantasylum qa404)

i do have a problem with the quoted noise figures. Likely they are measured with the attenuator in place.
That is clearly not correct.
 
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Apr 11, 2023 at 9:56 PM Post #23,501 of 25,602
kevin gilmore said:
srm212,252 etc are 6 volts 1 amp. So 6 watts
koss is 9 volts 1 amp. So 9 watts.
topping is 15 volts 1 amp. So 15 watts
.............
carbon cc is 125 watts
T2 is 225 watts
megatronxxl is 325 watts

no way an opamp driving transformers is going to be able to do .0008% thd

amir (incorrectly) measured koss at .01%
i (correctly) measured koss at .005% which is the limit of my equipment.
(i'm waiting on the new quantasylum qa404)

i do have a problem with the quoted noise figures. Likely they are measured with the attenuator in place.
That is clearly not correct.
Click to expand...
From topping's previous amplifier products, the EHA5 normal amplifier section is likely to be a composite amplifier, just like the amplifiers of jds atom and benchmark things. The common practice is to combine a precision opamp1 with a higher idle current opamp2 which has a specified closed-loop gain. opamp2 is placed inside the feedback loop of opamp1, which is the "feed forward technology" claimed by some manufacturers. In fact, it introduces a huge amount of feedback, the distortion test is usually lower than what the manufacturer's specs , but I don't know whether it can drive the transformer to output such low distortion though...never tried before :worried:
 
Apr 12, 2023 at 12:58 AM Post #23,502 of 25,602
kevin gilmore said:
srm212,252 etc are 6 volts 1 amp. So 6 watts
koss is 9 volts 1 amp. So 9 watts.
topping is 15 volts 1 amp. So 15 watts
.............
carbon cc is 125 watts
T2 is 225 watts
megatronxxl is 325 watts

no way an opamp driving transformers is going to be able to do .0008% thd

amir (incorrectly) measured koss at .01%
i (correctly) measured koss at .005% which is the limit of my equipment.
(i'm waiting on the new quantasylum qa404)

i do have a problem with the quoted noise figures. Likely they are measured with the attenuator in place.
That is clearly not correct.
Click to expand...
Megatron xxl ? Please tell us more …
 
Apr 12, 2023 at 2:06 AM Post #23,503 of 25,602
Apr 12, 2023 at 5:24 AM Post #23,505 of 25,602
nope, not a prank. will post much bigger picture later.

evidently confirmed elsewhere, the topping is the a90d circuit driving transformers.
 

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