[DarthVader92]

Probably a dumb question here, so you can all laugh at me if you want but if I wanted to keep my Topping a90d for some other uses....could I also use it as a pre-amp to say the Beyerdynamic A 20? Or is that not possible or just not needed?

Fyi, my DAC source is a Fiio K9 Pro AKM 4499 (in DAC mode obviously) I had the K9 before I got the a90d

 

[DarthVader92]

Thanks! I just always worry when I use words I don't know the meaning for

Anyway...high output impedance is what ti look for. Usually it means an OTL amp (the Bottlehead Crack has about a 120 ohm output impedance for example), which has a high IO out of necessity, but occasionally it'll happen in a solid state amp as well, by design.

What does OTL stand for?

 

[DarthVader92]

Like most things generalizations only get you so far. Just remember that a transducer works both ways. If you feed it electricity, it will move. And if it’s moving, it’s generating electricity. Sound can make it move. The diaphragm being stretched from its resting position acts like a spring to pull it back. The interaction between amplifier and speaker goes both ways. Sealed or open enclosures and their sizes and restrictions to air movement also can change things. It can get complicated, but listening is more important than figuring out all the equations of motion.
As long as the amp impedance is a few multiples smaller it’ll probably be ok. Having the amp impedance larger than the transducer sounds wonky. Small SET amps with efficient speakers, low impedance IEMs, and some high impedance headphones might get by with 3:1. I enjoy 6 ohm IEMs and 300 ohm ZMFs from a Nitsch PMax with a 1.5 ohm output impedance. From the 100 ohm A20 only one of those sounds good.
Personal preference comes into play. And expectations. Try everything. Try some of it more than once at different times. Your mood or the type of music may call for a high damping factor. Under other conditions you might want it to be looser.
Just become an amp hoarder. If you leave them all connected, it’s probably quicker and much less hassle than changing pads.

Excellent explanation thank you!! I am super picky with the sound and I know what I want. So I am really intrigued by finally really jumping into the amp world now that I’ve found headphones that I know are for me ie ZMF.

I’m also a musician and band director so my ears are well trained you could say. They’re sensitive so it’s a blessing and a curse. I’m more of a fan of quicker decay, a bit drier so I guess I would prefer slightly higher damping factor?

 

[jonathan c]

I’m also a musician and band director so my ears are well trained you could say. They’re sensitive so it’s a blessing and a curse. I’m more of a fan of quicker decay, a bit drier so I guess I would prefer slightly higher damping factor?

Yes.

 

[bokononista]

What does OTL stand for?

OTL stands for "output transformerless". These tube amplifiers do not have output transformers, so they have high output impedance. Its a natural great choice for high impedance dynamic headphones like ZMF, not much for others. Because of lack of OT, its cheaper, because good OT are costly.

 

[spittis]

Probably a dumb question here, so you can all laugh at me if you want but if I wanted to keep my Topping a90d for some other uses....could I also use it as a pre-amp to say the Beyerdynamic A 20? Or is that not possible or just not needed?

Fyi, my DAC source is a Fiio K9 Pro AKM 4499 (in DAC mode obviously) I had the K9 before I got the a90d

You can use the Topping as a pre-amp before the A20 if you want, I don't think there's much benefit in doing that though, unless you want to use the Toppings remote.

 

[drbusner]

That gives you a high 'damping factor' (load impedance source impedance). This is a measure of amplifier control over a transducer (headphone, loudspeaker). To some listeners (including me) a moderate DF permits fine sound; a very high DF (50x ?) robs the sound of 'blossoming', of airy expansion. In the end, preference will rule.

It appears that the damping factor of the amp that you recommend is actually quite high (listed as 100 balanced, 200 unbalanced in the documentation) since the output impedance is very low: .5 ohm balanced, .25 unbalanced. So that amp is quite transparent and shouldn't be changing the FR due to impedance.
My impression is that actual high output impedance amps (OTLs) with their low damping factors (3-4 when used with 300 ohm HPs) are introducing audible distortions in FR that many users find pleasing. To be clear, I'm not arguing that these are not pleasant listening experiences, but I wonder why the same changes to FR can't be implemented using EQ or pad rolling, etc.
Given all of this, I would say that the Topping amp would work well with Aeolus.

*This gets into the damping factor math in (excrutiating) detail if desired: https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor

 

[Pharmaboy]

I just always worry when I use words I don't know the meaning for

(Pharmaboy gazes at the monitor in puzzlement)

 

[Pharmaboy]

Just become an amp hoarder. If you leave them all connected, it’s probably quicker and much less hassle than changing pads.

It's scary just how observant this comment is.

I've been an amp 'ho for years, and this certainly rings true to me.

 

[jonathan c]

It appears that the damping factor of the amp that you recommend is actually quite high (listed as 100 balanced, 200 unbalanced in the documentation) since the output impedance is very low: .5 ohm balanced, .25 unbalanced. So that amp is quite transparent and shouldn't be changing the FR due to impedance.
My impression is that actual high output impedance amps (OTLs) with their low damping factors (3-4 when used with 300 ohm HPs) are introducing audible distortions in FR that many users find pleasing. To be clear, I'm not arguing that these are not pleasant listening experiences, but I wonder why the same changes to FR can't be implemented using EQ or pad rolling, etc.
Given all of this, I would say that the Topping amp would work well with Aeolus.

*This gets into the damping factor math in (excrutiating) detail if desired: https://benchmarkmedia.com/blogs/application_notes/audio-myth-damping-factor-isnt-much-of-a-factor

I recommend Violectric V281 specifically, V2XX 'series' in general, for high impedance headphones primarily because those h/p/a deliver more voltage as the headphone impedance rises. Topping delivers less mW and V as headphone impedance rises.

 

[drbusner]

The Topping a90d provides more than enough voltage for high impedance HPs to reach unlistenable volume levels without distortion setting in.
https://www.audiosciencereview.com/...0-discrete-review-headphone-amp-preamp.35114/

 

[jonathan c]

OTL stands for "output transformerless". These tube amplifiers do not have output transformers, so they have high output impedance. Its a natural great choice for high impedance dynamic headphones like ZMF, not much for others. Because of lack of OT, its cheaper, because good OT are costly.

The tradeoff for not having an output transformer is having an output capacitor in its stead. Why? In part, to protect the headphone from Volts of direct current (0 Hz) - which would be . Here too, output capacitor prices go up with quality - but not to the extent of output transformers.

 

[DarthVader92]

Alright I pulled the plug on one of them fancy high output impedance high voltage amp things.

Qobuz - Fiio K9 Pro AKM 4499 - Pietus Maximus - ZMF Aeolus African Blackwood with OG Aeolus lambskin pads = oh my!!

Thank you to those in here that pushed me to getting this amp. The presentation is better, mid bass and upper mids along with presence and depth/weight is just wonderful. I don’t know how to describe it right now. But my Aeolus have “come alive”…..very very cool. Thanks guys

 

[Pharmaboy]

Alright I pulled the plug on one of them fancy high output impedance high voltage amp things.

Qobuz - Fiio K9 Pro AKM 4499 - Pietus Maximus - ZMF Aeolus African Blackwood with OG Aeolus lambskin pads = oh my!!

Thank you to those in here that pushed me to getting this amp. The presentation is better, mid bass and upper mids along with presence and depth/weight is just wonderful. I don’t know how to describe it right now. But my Aeolus have “come alive”…..very very cool. Thanks guys

That is a beautiful headphone!

 

[jonathan c]

Alright I pulled the plug on one of them fancy high output impedance high voltage amp things.

Qobuz - Fiio K9 Pro AKM 4499 - Pietus Maximus - ZMF Aeolus African Blackwood with OG Aeolus lambskin pads = oh my!!

Thank you to those in here that pushed me to getting this amp. The presentation is better, mid bass and upper mids along with presence and depth/weight is just wonderful. I don’t know how to describe it right now. But my Aeolus have “come alive”…..very very cool. Thanks guys

... when it comes to Aeolus, only Aeolus OG lambskin earpads will do. "You've heard the rest, stay with the best".