[LobalWarming]

Taking a popular RCA 6AS7G as an example, it has a transconductance of 7000 µmhos, plate resistance of 280 ohm and amplification factor 2. Output impedance will then roughly be 1/0.007 + 280/(1+2) = 236 ohm. You will also see calculations without the plate resistance which brings it down to 143 ohm, but I believe that’s the case for grid-loaded topologies and I don’t think the H5 is. So 236 ohm it should be I think.

Should be.... in theory... and in theory there's no difference between theory and practice.

Without a curve tracer to plot the exact gm and other parameters of a specific tube, the initial 'datasheet' inputs for the calculation will be... ummm... suspect. However, we can be assured 99% of the time measured values will be worse. Probably only by 5-10% on a good tube, but still...

And for the great unknown... feedback is used in the output stage in most OTLs which reduces output impedance dramatically. I can't recall atm what W told me about the output impedance value of the H5 with a 6AS7, but around 100 ohms wouldn't be far off. I'll ask him again, once he's answered my latest round of 20 inane questions.

 

[roderickvd]

I’ll be interested to hear, I believe he likes zero-feedback designs although my 200+ ohm estimate does seem rather high compared to the 50 ohm minimum headphone impedance he’s specified.

 

[LobalWarming]

W likes zero global feedback... as do most of our ears... local feedback in small doses is not nearly as terrible and offers benefits - such as stability and lower output impedance.

 

[carballada]

Dear all, I really enjoy my Hifiman Arya Stealth on solid state amps.

What was my surprise when I read really good reviews with this headphone and the Feliks echo 2, a couple of places recommend exactly this combination (not with other Hifiman planar, seems only works exceptionally with the Stealth magnets versions)

After these readings and evaluating seriously the Feliks, I started this search for a tube OTL match with my Arya Stealth (not only Feliks) and of course, I landed here.

After reading almost this thread fully I want to ask you if any of you has direct experience driving an Arya Stealth with any H5, H7 or any variant.... (sorry I am nor really convince on the H32).

Thank you so much, any feedback will be welcome.

 

[LobalWarming]

Dear all, I really enjoy my Hifiman Arya Stealth on solid state amps.

What was my surprise when I read really good reviews with this headphone and the Feliks echo 2, a couple of places recommend exactly this combination (not with other Hifiman planar, seems only works exceptionally with the Stealth magnets versions)

After these readings and evaluating seriously the Feliks, I started this search for a tube OTL match with my Arya Stealth (not only Feliks) and of course, I landed here.

After reading almost this thread fully I want to ask you if any of you has direct experience driving an Arya Stealth with any H5, H7 or any variant.... (sorry I am nor really convince on the H32).

Thank you so much, any feedback will be welcome.

A current H5 owner, @mvneufeld, and former Arya owner could best answer that question.

However, the Arya has a very low impedance - not a great match for almost any OTL. H5 with a 7236 or pair of ED8000s might drive it decently, but not loudly. You might be better served with a transformer-coupled tube amp. W could certainly build one for you. Or other trafo-coupled amp like the Icon Audio HP8 or McChanson series.

Also, perhaps ask @andrewchoppa - planar magnet (like an oil magnet, but richer) about his fancy Eufonika hybrid prototype.

 

[roderickvd]

Funny, Feliks recommends 80 - 600 ohm headphones for its Echo 2 and Wieslaw 50 - 600 ohm for his Eufonika H5.
I agree though that objectively it won't be a great match. Bass would probably sound bloomy and not in a good way.
But hey, if it works on the Feliks then why not on the Eufonika? Bring a beer and you're welcome to try
Other than that fully agree with the above.

 

[carballada]

A current H5 owner, @mvneufeld, and former Arya owner could best answer that question.

However, the Arya has a very low impedance - not a great match for almost any OTL. H5 with a 7236 or pair of ED8000s might drive it decently, but not loudly. You might be better served with a transformer-coupled tube amp. W could certainly build one for you. Or other trafo-coupled amp like the Icon Audio HP8 or McChanson series.

Also, perhaps ask @andrewchoppa - planar magnet (like an oil magnet, but richer) about his fancy Eufonika hybrid prototype.

Thank you so much for your recommendations, but an OTC could be out of my scope (I could buy a H5 and HD650 for less )
My surprise was to read about my planar and the Feliks (https://english.achoreviews.com/2022/08/review-feliks-audio-echo-mkii.html)
Also I will contact @mvneufeld for sure, thank you!!

 

[carballada]

Funny, Feliks recommends 80 - 600 ohm headphones for its Echo 2 and Wieslaw 50 - 600 ohm for his Eufonika H5.
I agree though that objectively it won't be a great match. Bass would probably sound bloomy and not in a good way.
But hey, if it works on the Feliks then why not on the Eufonika? Bring a beer and you're welcome to try
Other than that fully agree with the above.

Exactly that's the point, next week I will try a Feliks on a local store with my headphones and I will see... and probably H5 could do the job in that case,right? no magic behind or maybe a different match could ruin everything!!!

I sent an email to Wieslaw some minutes ago, maybe he has more direct feedback.

But that's the point, try and enjoy

 

[andrewchoppa]

A current H5 owner, @mvneufeld, and former Arya owner could best answer that question.

However, the Arya has a very low impedance - not a great match for almost any OTL. H5 with a 7236 or pair of ED8000s might drive it decently, but not loudly. You might be better served with a transformer-coupled tube amp. W could certainly build one for you. Or other trafo-coupled amp like the Icon Audio HP8 or McChanson series.

Also, perhaps ask @andrewchoppa - planar magnet (like an oil magnet, but richer) about his fancy Eufonika hybrid prototype.

Haha-damn straight brother!!!!!!
My HE1000 stealths sound amazing with my new “prototype” Output-transformer-coupled tube amp from Wieslaw!!!. I was calling it a hybrid but was picked up because it isn’t a ss as well as a tube-it’s all Greek to me!!
But with all seriousness, that amp makes the hek’s sing!! Punchy, bass slam, plenty of power (I listen to rock/metal loud and I haven’t been able to go past 11 on the dial!!)
I also have a sparkos Aries and that pairing is literally sublime (perfect in fact). But the tube amp is honestly not far behind in enjoyablility!!! It’s completely different to the sparkos but both are magnificent!!!!!!

 

[andrewchoppa]

Thank you so much for your recommendations, but an OTC could be out of my scope (I could buy a H5 and HD650 for less )
My surprise was to read about my planar and the Feliks (https://english.achoreviews.com/2022/08/review-feliks-audio-echo-mkii.html)
Also I will contact @mvneufeld for sure, thank you!!

Just fyi - My eufonika otc was $899 aud. A bargain and cheaper than the echo otl.

 

[mvneufeld]

Sent this in a PM to carballada, but I may as well post it here, too. It basically repeats what Lobal and others have said:
I had an Arya when I bought my H5, but unfortunately it was not a good pairing - the Ayra sounded anemic and thin. I wound up selling my beloved Ayra (I still miss it) and got a ZMF Atrium. OTL tube amps like H5 sound best with high impedence headphones (250 ohms or higher) like many Beyerdynamics, Sennheisers and ZMFs. OTL amps don't play well with planar magnetic headphones like the Arya. If you want tubey goodness with your Arya, you'll want to get a hybrid tube amp like the Feliks Echo Mk2, or if you want to try rolling various tubes without spending tons of money, get the Schiit Lyr 3.

 

[carballada]

Sent this in a PM to carballada, but I may as well post it here, too. It basically repeats what Lobal and others have said:
I had an Arya when I bought my H5, but unfortunately it was not a good pairing - the Ayra sounded anemic and thin. I wound up selling my beloved Ayra (I still miss it) and got a ZMF Atrium. OTL tube amps like H5 sound best with high impedence headphones (250 ohms or higher) like many Beyerdynamics, Sennheisers and ZMFs. OTL amps don't play well with planar magnetic headphones like the Arya. If you want tubey goodness with your Arya, you'll want to get a hybrid tube amp like the Feliks Echo Mk2, or if you want to try rolling various tubes without spending tons of money, get the Schiit Lyr 3.

Thank you so much for that input!! your Arya was a v2? not Stealth magnets?
I think is not simple like that seems the one with Stealth magnets version is the version who works really well with OTC (at least confirmed with Feliks echo mk2, and if I am not wrong it's a pure OTL anyway)

Just fyi - My eufonika otc was $899 aud. A bargain and cheaper than the echo otl.

That sounds great to my pocket but maybe I am wrong but your version is a real hybrid, not powered from tubes and a SS on the last part... I thought that an OTC is using power tubes anyway and a transformer to allow low impedances....

 

[mvneufeld]

I actually had two Ayras - v1 and then v2. I haven't had chance to try the Stealth. I'm seriously tempted to get an Arya Organic to use with my little hybrid tube amp (a Garage1217 Solstice).
I got it wrong - the Feliks echo mk2 is indeed an OTL, as is the Eufonika H5. As far as I know, the general consensus is that planar headphones aren't a good match for OTL amps, but there may be exceptions. In my case, the Arya did work with my H5, it just sounded thin and performed much better with my hybrid amp.

 

[carballada]

I actually had two Ayras - v1 and then v2. I haven't had chance to try the Stealth. I'm seriously tempted to get an Arya Organic to use with my little hybrid tube amp (a Garage1217 Solstice).
I got it wrong - the Feliks echo mk2 is indeed an OTL, as is the Eufonika H5. As far as I know, the general consensus is that planar headphones aren't a good match for OTL amps, but there may be exceptions. In my case, the Arya did work with my H5, it just sounded thin and performed much better with my hybrid amp.

Thank you!!! this is very valuable information for me, thank you very much again. I will come back with any info about this topic, the Arya Organic is using also the Steath magnets... will see

 

[jwwillia]

Sent this in a PM to carballada, but I may as well post it here, too. It basically repeats what Lobal and others have said:
I had an Arya when I bought my H5, but unfortunately it was not a good pairing - the Ayra sounded anemic and thin. I wound up selling my beloved Ayra (I still miss it) and got a ZMF Atrium. OTL tube amps like H5 sound best with high impedence headphones (250 ohms or higher) like many Beyerdynamics, Sennheisers and ZMFs. OTL amps don't play well with planar magnetic headphones like the Arya. If you want tubey goodness with your Arya, you'll want to get a hybrid tube amp like the Feliks Echo Mk2, or if you want to try rolling various tubes without spending tons of money, get the Schiit Lyr 3.

Could you use the pre-outs on an Eufonika OTL into a solid state amp and then run the Arya from there? Should impart some of that tube flavor without the need for an OTC amp. I haven’t tried this with low-impedance planars (currently don’t own any) But I’ve done this with IEMs and it works well.