[MohawkUS]

I'm still trying to decide if I should get the HPA-01 or not. My Ultrasones have a very flat impedance graph,



It's not perfectly flat as planars, but better than most dynamics. Has anyone tried the Bakoons with low impedance/highly efficiant dynamics? Other than the Fostex as I have seen some people use that combination and report exaggerated bass because of the impedance curve.


I'm sold on getting a battery powered amplifier as I've had persistent problems with noise in my audio equipment as well as non-audio related problems with the power delivery. I'm just skeptical that it's the best move to buy an amplifier designed for planars for a dynamic.

 

[Hi-Head]

I'm just skeptical that it's the best move to buy an amplifier designed for planars for a dynamic.

Who says that the Bakoon headamps are designed for planars? As mentioned above the Bakoon HPA-21 drives my HD 800 so well - especially in current mode - I have no doubt it can be a good match for your Ultrasones as well. Find a dealer who will borrow it to you and give it a listen yourself. But be careful it might be mind blowing...!

 

[Soned]

I suppose if the HPA-21 has no trouble driving the HD800 it should have no issue driving the LCD-3 with its increased impedance.Has anyone listened to the pairing with the increased impedance?

 

[SilverEars]

I'm still trying to decide if I should get the HPA-01 or not. My Ultrasones have a very flat impedance graph,



It's not perfectly flat as planars, but better than most dynamics. Has anyone tried the Bakoons with low impedance/highly efficiant dynamics? Other than the Fostex as I have seen some people use that combination and report exaggerated bass because of the impedance curve.


I'm sold on getting a battery powered amplifier as I've had persistent problems with noise in my audio equipment as well as non-audio related problems with the power delivery. I'm just skeptical that it's the best move to buy an amplifier designed for planars for a dynamic.

Wow, this is quite remarkable, I have never seen a full-sized dynamic so flat!!  Not saying it sounds good as I haven't heard it, but it's quite unique.  

 

[Sonido]

Wow, this is quite remarkable, I have never seen a full-sized dynamic so flat!!  Not saying it sounds good as I haven't heard it, but it's quite unique.  :bigsmile_face:

Those are impedance graphs, not frequency response. A lot of low impedance dymanics have near flat impedances.

 

[SilverEars]

Those are impedance graphs, not frequency response. A lot of low impedance dymanics have near flat impedances.

Yes, I'm aware it is the impedance graph as I don't expect FR to be so flat.  I just haven't run into dynamics other than iems with such flat impedance characteristic.  I notice momentum is the same and like you say it's common for low impedances to have flat character.  The problem with momentum's FR is the drop at the treble range which should output a darker characteristic, but it's pretty linear until 11k and distortion isn't too bad either. I'm curious why the TOTL dynamics are curved like the HD800 for example at around 300 and peaking to 600.  Is there any dynamic that shows pretty linear compensated FR that has flat impedance characteristic with low distortion?

 

[MohawkUS]

Yes, I'm aware it is the impedance graph as I don't expect FR to be so flat.  I just haven't run into dynamics other than iems with such flat impedance characteristic.  I notice momentum is the same and like you say it's common for low impedances to have flat character.  The problem with momentum's FR is the drop at the treble range which should output a darker characteristic, but it's pretty linear until 11k and distortion isn't too bad either. I'm curious why the TOTL dynamics are curved like the HD800 for example at around 300 and peaking to 600.  Is there any dynamic that shows pretty linear compensated FR that has flat impedance characteristic with low distortion?

I believe Ultrasone may have put a good bit of effort into making the headphones have a flat impedance curve. It's kind of implied with the Edition series that they will sound good out of anything, and that has proven true with the remarkably cheap HP outs on my vintage equipment. The CD player I have here simply is just a single op-amp circuit. That's part of my hesitation, I've had some people note that the Editions don't benefit too much from amplification.

It's part of the reason I settled on them in the first place, an impedance mismatch can make good equipment unbearable. And it's not always easy to see where you may run into a problem.

 

[jacal01]

I personally haven't, the "secret" behind the Bakoon is its battery power supply and the current amplification whereas the Master 9 I think is a traditional class A voltage amplifier however very nicely put together from what I see at the Audio-gd website. The concepts in both amps target low to none distortion plus minimal negative feedback loop and a clean power distribution.

 
Speculation on my part, but considering how gd-audio seems to "piggyback" off of the Krell products, I would tend to believe that the Master 9 uses current loop amplication much like the Krell amps.  We do know that at least the M9 output is current driven, as evidenced by its ACSS compatibility with the Krell CAST and Bakoon SATRI.

 

[Hi-Head]

Speculation on my part, but considering how gd-audio seems to "piggyback" off of the Krell products, I would tend to believe that the Master 9 uses current loop amplication much like the Krell amps.  We do know that at least the M9 output is current driven, as evidenced by its ACSS compatibility with the Krell CAST and Bakoon SATRI.

My understanding of the ACSS circuit in the Master 9 as described on the Audio-gd website is that it does not use OPAs for amplification but only at the output stage whereas the HPA-21 uses OPAs for amplification after conversion of the voltage input signal by the input resistor (and if not connected to a Satri type sourc which would make such conversion unnecessary). The Master 9 outputs indeed a current signal useable by a main amplifier but NOT an amplified current signal converted into voltage useable by a headphone. This is at least how I read and interpret the released information on the Audio-gd website.

 

[jacal01]

Per the gd-audio website M9 technology description, "All signal gain is in current, all transistors work in pure class A mode."  My speculation is that the M9 uses the current loop gain topology much as implemented in the Krell amps.  You're right tho in that any voltage driven input or output (e.g. HP) would need conversion to/from the current driven amplification stage.
 
I don't quite follow your opamp vs. discrete transistor contrasting argument, however. Considering that most opamp chip designs employ a voltage controlled signal gain circuit, that is not especially a distinguishing characteristic between current driven amplification topologies. Or are you saying that the HPA-21 uses a voltage driven amplification stage?
 
Still there are some current controlled (transconductance) signal opamps, so I would be interested to know if those are used in the HPA-21 amp.  Is there a reference describing its gain circuitry?  

 

[Hi-Head]

Bakoon on their Facebook page have a teaser for new product.  In the comments they say it will be "wonderful for IEM users" but will not be a DAP.  Maybe an AMP/DAC?

When I took delivery of my HPA-21 my Bakoon dealer told me they are preparing the launch of their long awaited battery powered DAC with Satri link output. I am sure I won't resist to get my hands on such type of product and am surprisingly only aware of one other DAC - the M2Tech Vaughan - which uses a battery power supply.

 

[Hi-Head]

I don't quite follow your opamp vs. discrete transistor contrasting argument, however. Considering that most opamp chip designs employ a voltage controlled signal gain circuit, that is not especially a distinguishing characteristic between current driven amplification topologies. Or are you saying that the HPA-21 uses a voltage driven amplification stage?

Still there are some current controlled (transconductance) signal opamps, so I would be interested to know if those are used in the HPA-21 amp.  Is there a reference describing its gain circuitry?  

Yes, the HPA-21 definitely uses current amps in the signal path amplification loop and NOT ONLY voltage controlled opamps. My understanding in fact is that the HPA-21 contains both types of opamps as referenced in a review of the HPA-21 in a German Hifi-Magazine.

 

[jacal01]

So the review explicitly states that the HPA-21 implements opamps for signal gain and not BJTs or other type discrete transistors?

 

[Hi-Head]

So the review explicitly states that the HPA-21 implements opamps for signal gain and not BJTs or other type discrete transistors?

The review states the signal is being amplified using current amps ('Strom-Amps' in German native language) without giving further details as to the exact type of hardware used in the Satri IC. The sound of the HPA-21 was so convincing it made it to the top of the list of headamps this magazine had tested before and is now used as their new reference amp by quite a margin.

 

[jacal01]

"Strom-Amps" sounds almost simplistic, like "current driven amplfication".  Doesn't necessarily imply opamp chips, like trans-impedance or the sort.  Not sure I have anything against an opamp chip gain stage, per se, but it seems to me that their main advantage is in small size for portable amp products and such, with their down side in circuit inflexibility for signal control and/or conditioning, as opposed to discrete components which can be varied and positioned to optimize that particular signal gain circuitry.
 
Of course you can have a combination of onboard (chip) and off board circuits, but I would think a product of this caliber would be comprised of mostly discrete components,especially in the gain stage, and except for perhaps some auxiliary function chip modules doing straight-forward signal processing or conversion and the like.  The flip side of that is that you can bring a whole lot of transistors to bear using chip technology, like a bank of opamps for amplification control.
 
It's gratifying that they're duly impressed with the HPA-21, tho.