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Woo Audio WA7 & WA7tp DAC and Headphone Amp Review

restorer-john

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#61
Was this sold for home or for use by dealers for equipment demos?
Supplied to the dealers for showrooms. We had Yamaha and Sansui ones which were very similar in our speaker rooms. The Yamaha one had a really cool large separate Nixie numerical display for the speaker number. Each speaker had a number tent stand on top.

This one we picked up years ago at a dealership auction. There were three- wish we'd bought them all now. They take a whole day to wire up- I know, I used to do it every time we re-arranged the shop...
 
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#62
While the test are different, they definitely show very similar deficiencies:



That would be SINAD of 40 dB. The test tone is lower frequency so exaggerating the problem even more than my 1 kHz test tone.

It is a shame that JA uses such diplomatic words to describe this poor performance:

View attachment 23619

As a result, probably most people didn't realize how poor the performance was as reading the graphs with no reference is hard.

Thank you for the feedback Amir and I agree completely. JA seems to adopt a very diplomatic concluding description despite the performance analysis. What is even more interesting, the product above was included in stereophile's recommended components for quite a while after the review.

Speaking from personal experience: I did own the WA3 and then the WA2 back in 2013. At the time I had no idea of anything audiophile and had no knowledge of anything related to audio equipment performance. I just loved the look of these devices (nice lights and industrial design) so I went for them. I was soon convinced to either return or sell. Some of the problems encountered: The transformer mechanical hum, the low level buzzing sound heard through the headphones and the wireless interference regularly picked up from various home devices.
 
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#63
I have almost bought this WooAudio amp many times. I have actually had it in the basket on the site but could never bring myself to hit order. I wonder how it measures in comparison?

https://wooaudio.com/amplifiers/wa6se
I'd love to see a WA6SE measured, but its a big beast so shipping would be prohibitive. Some while ago it was measured here, https://kenrockwell.com/audio/woo/wa6-se.htm#perf
and looks to do what is expected.

I must admit I have a WA6SE and like it (it does look great in black with the Sophia rectifier tube). I feed it from an RME ADI-2 DAC. I listen with HD800's and it drives them well. With the RME, when I need perfect sound I use the inbuilt headphone amp, when I feel like something subtly different I use the Woo. Plus a little EQ from the RME gives the HD800's just a little more low down oomph when needed.
 

amirm

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#64
I'd love to see a WA6SE measured, but its a big beast so shipping would be prohibitive. Some while ago it was measured here, https://kenrockwell.com/audio/woo/wa6-se.htm#perf
and looks to do what is expected.
I agree that series looks more beautiful than WA7. On Ken Rockwell, I read his review of WA7 and was shocked. Everything he measured was poor yet he went on and on about how great the product was. He never said where he got the WA7. I wonder if it was a loan from the company. Very disappointing.
 

daftcombo

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#65
No, I'm reasonably confident that it could easily be improved by circuit changes, but leaving the tubes in place. Of course it wouldn't be an effects box any more, which might turn off the target audience.
The expression "effects box" is clever. It's like the listener worked hand in hand with the sound engineer to make records sound "better" to his ears.
 

daftcombo

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#66
I agree that series looks more beautiful than WA7. On Ken Rockwell, I read his review of WA7 and was shocked. Everything he measured was poor yet he went on and on about how great the product was. He never said where he got the WA7. I wonder if it was a loan from the company. Very disappointing.
Have you read his article "Why tubes sound better"?
https://kenrockwell.com/audio/why-tubes-sound-better.htm .?

A good laugh...
 

SIY

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#68
Actually I find the article pretty accurate.
Sorry to disagree, but I disagree. I'll just start with the title: tube amps are either transparent, or they're effects boxes that can't be turned off. If the former, then the claim of "better sound" is, uhhh, hollow. If the latter is what someone wants, that's outside of high fidelity. I suspect that if the distortion is gross enough to be audible, or if the frequency response changes with high source impedance were significant, most listeners would not prefer it if tested ears-only.

Not a comprehensive critique, but some high points:

Tube amplifiers have much more distortion than solid-state amplifiers, but most of it is second-order, which is quite musical.

Errr, no. A well balanced push pull circuit will show very low second and higher even harmonics. A less well balanced one will still have second harmonic below any reasonably audible threshold. This is true regardless of whether the active device is a tube, a FET, or even a bipolar transistor. So this is dependent on topology, not device.

Not only is tube amplifier distortion harmonious, it increases as things get louder - exactly as they do in a musical performance.

Besides being a non sequitur, this is true of virtually any amplifier in existence.

The misleading graphs that follow speak for themselves, followed by the argument that you should listen to music with squashed dynamics.

No one needs or uses 300 WPC ...

Didn't Bernie Sanders say that?

The next section on capacitors is ludicrous to anyone who has ever understood the voltage divider equation. I think my measurements (here, here, here, and here) did a reasonable job of debunking these myths- and all they did was confirm what any competent engineer knows about "capacitors in the signal path."

The next section on feedback repeats a litany of common misconceptions. A few minutes reading a much better and just as accessible analysis of feedback from Bruno Putzeys will give you an accurate understanding instead of this mishmash of audio legend.

His next argument is higher output impedance? Sure, often true, but I point you toward some of Nelson Pass's solid state designs as well as the current source amps being touted in some circles. Either way, if that's the absolutely non-adjustable EQ curve you want for your speakers, you can buy a tube amp or you can buy a small power resistor to put in series (the Carver Challenge trick). Or do the EQ upstream, a much better solution for sound. And of course, this again has nothing to do with tubes per se, any desired output impedance can be designed into an amp using any choice of device types.

The offset claim is one of those "true-but" since the offset of any engineered solid state amp is near zero anyway, and of course, this is an argument for output transformers, not tubes. You can design a nice, albeit heavy and expensive solid state amp with OPTs if that (and speaker protection) are your worry. Nothing to do with tubes per se.

Microphonics are very real, and here's where I agree there can be audible difference peculiar to some tubes in some circuits. And "better" then becomes "effects box I can't turn off or adjust" once again.

If you match everything, they will sound the same, but in real life, things are never matched.

And then walks it all back, punctuated by a homily.
 

Krunok

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#69
Sorry to disagree, but I disagree. I'll just start with the title: tube amps are either transparent, or they're effects boxes that can't be turned off. If the former, then the claim of "better sound" is, uhhh, hollow. If the latter is what someone wants, that's outside of high fidelity. I suspect that if the distortion is gross enough to be audible, or if the frequency response changes with high source impedance were significant, most listeners would not prefer it if tested ears-only.

Not a comprehensive critique, but some high points:

Tube amplifiers have much more distortion than solid-state amplifiers, but most of it is second-order, which is quite musical.

Errr, no. A well balanced push pull circuit will show very low second and higher even harmonics. A less well balanced one will still have second harmonic below any reasonably audible threshold. This is true regardless of whether the active device is a tube, a FET, or even a bipolar transistor. So this is dependent on topology, not device.

Not only is tube amplifier distortion harmonious, it increases as things get louder - exactly as they do in a musical performance.

Besides being a non sequitur, this is true of virtually any amplifier in existence.

The misleading graphs that follow speak for themselves, followed by the argument that you should listen to music with squashed dynamics.

No one needs or uses 300 WPC ...

Didn't Bernie Sanders say that?

The next section on capacitors is ludicrous to anyone who has ever understood the voltage divider equation. I think my measurements (here, here, here, and here) did a reasonable job of debunking these myths- and all they did was confirm what any competent engineer knows about "capacitors in the signal path."

The next section on feedback repeats a litany of common misconceptions. A few minutes reading a much better and just as accessible analysis of feedback from Bruno Putzeys will give you an accurate understanding instead of this mishmash of audio legend.

His next argument is higher output impedance? Sure, often true, but I point you toward some of Nelson Pass's solid state designs as well as the current source amps being touted in some circles. Either way, if that's the absolutely non-adjustable EQ curve you want for your speakers, you can buy a tube amp or you can buy a small power resistor to put in series (the Carver Challenge trick). Or do the EQ upstream, a much better solution for sound. And of course, this again has nothing to do with tubes per se, any desired output impedance can be designed into an amp using any choice of device types.

The offset claim is one of those "true-but" since the offset of any engineered solid state amp is near zero anyway, and of course, this is an argument for output transformers, not tubes. You can design a nice, albeit heavy and expensive solid state amp with OPTs if that (and speaker protection) are your worry. Nothing to do with tubes per se.

Microphonics are very real, and here's where I agree there can be audible difference peculiar to some tubes in some circuits. And "better" then becomes "effects box I can't turn off or adjust" once again.

If you match everything, they will sound the same, but in real life, things are never matched.

And then walks it all back, punctuated by a homily.
Hahaha - I though you would react! :D

Ok, but still - some folks like the tube distortion and somehow 0.2% of amp distortion alwas sound a little bit "nicer" than with SSD.

AFAIK, soft clipping part is also true.

Right now I'm listening to my tube amp while enjoying 2nd glass of wine so I'm probably highly biased toward that nice orange glow! :D
 

SIY

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#70
Ok, but still - some folks like the tube distortion and somehow 0.2% of amp distortion alwas sound a little bit "nicer" than with SSD.

AFAIK, soft clipping part is also true.

Right now I'm listening to my tube amp while enjoying 2nd glass of wine so I'm probably highly biased toward that nice orange glow! :D
I'd love to see some data showing that 0.2% for an actual physical amp is audible. I'd guess no, but if someone has contradictory data...

The soft clipping part is also not really true- note what he had to do to "show" that (deliberately use badly matched and worn out tubes) and what distortion versus power curves look like for tube amps (see, for example figures 5 and 6 here) (or even better, figures 6, 7, and 8 here). And recovery from clipping is often considerably worse for a tube amp unless it's specifically designed to reduce blocking distortion, which most aren't.
 

Krunok

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#72
I'd love to see some data showing that 0.2% for an actual physical amp is audible. I'd guess no, but if someone has contradictory data...

The soft clipping part is also not really true- note what he had to do to "show" that (deliberately use badly matched and worn out tubes) and what distortion versus power curves look like for tube amps (see, for example figures 5 and 6 here) (or even better, figures 6, 7, and 8 here). And recovery from clipping is often considerably worse for a tube amp unless it's specifically designed to reduce blocking distortion, which most aren't.
Ok, ok, you got me there as well - can we at least settle that the orange glow is nice? :)
 

SIY

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#74
A bit early here for that, but tonight I think there will be something red, French, and well-aged.

I may even get a chance to fire up my Red Light District.
 
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#78
I’ve been very tempted by tube headphone amps, like the Woo Audio WA5 LE, but I admit it’s mostly because of the cool look. I’ve been thinking I could get the tube amp and hide my THX AAA 789 behind it, do some careful wiring and enjoy its great sound while bathing in the glow of the tubes.
 

Krunok

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#80
I’ve been very tempted by tube headphone amps, like the Woo Audio WA5 LE, but I admit it’s mostly because of the cool look. I’ve been thinking I could get the tube amp and hide my THX AAA 789 behind it, do some careful wiring and enjoy its great sound while bathing in the glow of the tubes.
Nope, no cheating - if you fire it you have to listen to it! :)
 

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