[mandrake50]

   
I don't think we have anything to worry about in the H10 application.  It is setup very similarly to the Violectric V200 and many have said, including Fried, the designer, that the opamp implementation is less critical than most.  The alleged persnickety character of the 797 is its stability in unity gain applications.  Most folks have found the 797 to be rock stable and have had zero issues when popping the AD797 into the V200. So far there have been no issues with using it in the H10.   The BRZ, besides being SOIC, has slightly different electrical parameters as compared to the ANZ. It is also a higher grade "B" batch, which means its parameters will not drift as much with changes in temperature and other environmental factors. The parameters are close enough that the BRZ can be substituted in any circuit where the ANZ is used.  I suspect that most people will hear no difference between the two, but at least on paper, the BRZ is the superior model.

I hear you, but gross problems like instability are one thing. Whether the chip is performing optimally in the circuit is a different question.
I looked at the spec sheet and agree with you. Around 90% of the specifications for the A and B parts are identical. From what I saw, the differences should not be significant for this application.

 

[jjkes]

 
Has anyone done any measurements with any of these opamps? I was just reading one of the designer threads on the AD797. These guys say that it is picky about implementation. Specific  resistance capacitance and board layout is required for optimum performance.
I just wonder how well they work when plugged into a board optimized for a different opamp. OTH, so far I like the sound, but it is difficult for me to really compare stock versus the new opamps as doing any sort of quick A/B tests is not possible. Obviously they work, but are they working and giving optimal results?
 
I guess we play it by ear, but the engineer in me wonders what we are really doing to the system from the electronics perspective.
 
Here is the thread: LINK
 
A member, Filburt, comments:
"I personally like the AD797, but my experience has been (and I'm told my knowledgeable engineers) that it is a somewhat difficult chip to use properly (for reference, I don't consider the AD8397 "difficult"). It cannot just be casually inserted into a circuit; you have to build around it (which means no using SOIC-to-DIP adaptors, especially Browndog!). The topology makes it very sensitive to a variety of environmental factors that you can be much more casual towards with many other chips. If it isn't used properly, you will get substantially rising harmonic distortion with frequency at the least, along with probably other distortion products."
 
More than likely the H10 was not designed in this way, but rather to make the stock opamps work the best that they can. And of course to get the BRZ, we are using adapters. People say they sound different than the ANZ, could it be because they are performing worse?

There might be something to FILBURT's comment.
Last weekend I replaced the AD797ANZ with a Browndog AD797BRZ. I initially could hear a distinct difference but realized after further listening that what I was hearing was distortion. The BRZ doesn't even sound close to the ANZ. The ANZ is far superior. It doesn't make sense to me. I thought maybe I received a faulty OPAMP. Couuld it be that the BRZ doesn't work in the H10 circuit?

 

[genclaymore]

The BRZ that I have I bought from audio_Jade or was it Audio_Cjn  I don't recall his exact name but i don't have any issues with it in my H10. I been using it for a couple of months now. Maybe you got a fake or a damaged one.
 
After a while the two pairs of LT1357's that I have in a dual to single op-amp adapter improved and work very well for me with the AD797BRZ's for me for now,While I didn't like the dual channel version, the LT1358. i originally tried Two pairs of LT1363's and I didn't like them one bit. I haven't tried Two pairs of LT1122 yet.

 

[jjkes]

Most unlikely that they are fakes. Browndog sources them from Mouser or Digikey. Could be damaged or defective but how would I know?

 

[Gibalok]

Guys, since you are deep inside Gustard h10, can you prove my thoughts that this amp is designed mostly for high impedance headphones?

Well it blows me away with He-560 but burn my brain with 25ohms TH900..

 

[DDDamian]

Guys, since you are deep inside Gustard h10, can you prove my thoughts that this amp is designed mostly for high impedance headphones?

Well it blows me away with He-560 but burn my brain with 25ohms TH900..

Hi Gibalok - we've been chatting on the Bryston thread
 
I'm not sure the H-10 was designed for high-impedance cans (usually taken to mean 150ohms+ like the higher-end Sennheisers, some Beyers at 250-600ohms, etc).
 
It is well-designed for phones requiring higher current or overall power. This tends to include planar phones like the Hifimans or Audeze lines, which are typically low-impedance (<100ohms) but need some current to drive them.
 
When you say it "burns your brain" with the TH900 do you mean too powerful (i.e. little usable range on the output dial) or something else? The gain is adjustable via DIP switches on the back of the amp for different loads.

 

[Gibalok]

  Hi Gibalok - we've been chatting on the Bryston thread
 
I'm not sure the H-10 was designed for high-impedance cans (usually taken to mean 150ohms+ like the higher-end Sennheisers, some Beyers at 250-600ohms, etc).
 
It is well-designed for phones requiring higher current or overall power. This tends to include planar phones like the Hifimans or Audeze lines, which are typically low-impedance (<100ohms) but need some current to drive them.
 
When you say it "burns your brain" with the TH900 do you mean too powerful (i.e. little usable range on the output dial) or something else? The gain is adjustable via DIP switches on the back of the amp for different loads.

 
I mean the highs are very bright.. 

 

[DDDamian]

   
I mean the highs are very bright.. 

I see. I have this combo for op-amps in right now: two OPA2604 and two AD797AN. I've found this combo quite warm yet still detailed. Too warm for the HD-650 yet perfect for the HD-800, so maybe a good match for your TH900's. For a while that was about the only way I could listen to the HD-800, and early on I still had to EQ the treble down a bit. Now that I've become more accustomed to them I don't have to EQ them with the H-10 and the combo above. Makes me that much more a believer in brain burn-in, as I had come from warmer headphones and the HD-800's nearly pierced my eardrums at first.
 
If you're adverse to op-amp swaps (swabs here lol) then I'm thinking the TH900's may not be the right sound-signature for you. The above combo is the warmest I've ever heard from any amp, although my tube amps have lots of options that way. Just things to consider.

 

[Gibalok]

  I see. I have this combo for op-amps in right now: two OPA2604 and two AD797AN. I've found this combo quite warm yet still detailed. Too warm for the HD-650 yet perfect for the HD-800, so maybe a good match for your TH900's. For a while that was about the only way I could listen to the HD-800, and early on I still had to EQ the treble down a bit. Now that I've become more accustomed to them I don't have to EQ them with the H-10 and the combo above. Makes me that much more a believer in brain burn-in, as I had come from warmer headphones and the HD-800's nearly pierced my eardrums at first.
 
If you're adverse to op-amp swaps (swabs here lol) then I'm thinking the TH900's may not be the right sound-signature for you. The above combo is the warmest I've ever heard from any amp, although my tube amps have lots of options that way. Just things to consider.

 
DDDamian, thank you
 
But more likely i will swap H10 to BHA-1 and pick some tube one ^)

 

[DDDamian]

   
DDDamian, thank you
 
But more likely i will swap H10 to BHA-1 and pick some tube one ^)

My pleasure Gibalok Honestly, that would be a great move. The BHA-1 will be fine for your HE-560's (balanced). For your Fostex TH900's go for a warmer SET-tube design.
 
Good luck!

 

[tretneo]

 
I may do that, but I find that when it takes minutes to make a change it becomes difficult for me to detect differences, unless it is a glaring difference.
Once my hand heals, I will pop the Burson cards in and give it a listen.
Thanks for the impressions!

 
Have you had a chance to pop those Bursons in yet? I'm curious to hear some more impressions.

 

[mandrake50]

   
Have you had a chance to pop those Bursons in yet? I'm curious to hear some more impressions.

Not yet. I may do that over next weekend.

 

[tretneo]

 
Not yet. I may do that over next weekend.

 
Nice, let us know how it goes. I haven't done any other opamp rolling so I only have the stock and Bursons to go by. The heat difference once I installed the Bursons was pretty drastic so don't be alarmed and keep good airflow around the amp.

 

[Jozurr]

  I see. I have this combo for op-amps in right now: two OPA2604 and two AD797AN. I've found this combo quite warm yet still detailed. Too warm for the HD-650 yet perfect for the HD-800, so maybe a good match for your TH900's. For a while that was about the only way I could listen to the HD-800, and early on I still had to EQ the treble down a bit. Now that I've become more accustomed to them I don't have to EQ them with the H-10 and the combo above. Makes me that much more a believer in brain burn-in, as I had come from warmer headphones and the HD-800's nearly pierced my eardrums at first.
 
If you're adverse to op-amp swaps (swabs here lol) then I'm thinking the TH900's may not be the right sound-signature for you. The above combo is the warmest I've ever heard from any amp, although my tube amps have lots of options that way. Just things to consider.

 
You're using the AD797 instead of OPA134 and the OPA2604 instead of the NE5532 yes? Can you please post links as to which chips did you buy exactly? 
 
Also, instead of OPA2604, have you tried other opamps?
 
Im really interested in getting the warmest sound and hardest bass out of the H10 without sacrificing on much detail or clarity. However, reading reviews of the OPA2604, it seems like it isn't much different than the NE5532, and a better choice is maybe the OPA627.

 

[DDDamian]

   
You're using the AD797 instead of OPA134 and the OPA2604 instead of the NE5532 yes? Can you please post links as to which chips did you buy exactly? 
 
Also, instead of OPA2604, have you tried other opamps?
 
Im really interested in getting the warmest sound and hardest bass out of the H10 without sacrificing on much detail or clarity. However, reading reviews of the OPA2604, it seems like it isn't much different than the NE5532, and a better choice is maybe the OPA627.

Hi, that's correct but as to links I can't help. I bought the amp with those chips installed and the original stock chips on the side in some anti-static foam.
 
I can only give you the overall impression of those, which by the sounds of it would suit your needs in terms of warmth, bass extension and detail. If I had a complaint with the pairing it is too warm for already-warm cans like the 650, but does wonders for brighter cans like the HD-800/HE-400 in my kit.
 
If it was my only amp I'd be looking for a more even FR to balance it out. Instead I find it useful as-is to tame those brighter cans or for incredible depths with the LCD2.2. Now that I have the brighter Bryston BHA-1 I'm unlikely to mess with it. If it was my only amp or I had only warmer cans I'd be after a more neutral chipset for sure.