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The Opamp thread - Page 276

post #4126 of 4738
Quote:
Originally Posted by WiR3D View Post

Its probably my fault are you using the AD797, it just sounds so good, but don't be surprised when they break from all the oscillation. :p

I have said before for my STX the following are on my list:

  • LME49990
  • OPA1612
  • HA5002
  • AD8599

I ordered a 10 pack of soldered AD797BRs, so I still have 7 spare ones to use as replacements.

post #4127 of 4738
Quote:
Originally Posted by PurpleAngel View Post

I ordered a 10 pack of soldered AD797BRs, so I still have 7 spare ones to use as replacements.

Now that is planning

post #4128 of 4738
Quote:
Originally Posted by WiR3D View Post

Its probably my fault are you using the AD797, it just sounds so good, but don't be surprised when they break from all the oscillation. :p

I have said before for my STX the following are on my list:

  • LME49990
  • OPA1612
  • HA5002
  • AD8599

 

 

For the HA5002 to be used as a buffer in STX, should it be obtained as a dual or a single? (if theres even a dual)


Edited by harryyeo - 7/19/12 at 9:17am
post #4129 of 4738

Don't think you can get it as a dual. Only ever seen it as a single and the adapter is not standard either as the bottom of the PCB has specific smd resistors in place. Got 8 of them off HiFlight (Ron Kerlin - Opamp Guru) :)

post #4130 of 4738
Quote:
Originally Posted by SpudHarris View Post

Don't think you can get it as a dual. Only ever seen it as a single and the adapter is not standard either as the bottom of the PCB has specific smd resistors in place. Got 8 of them off HiFlight (Ron Kerlin - Opamp Guru) :)

 

 

I see.

So I'll have to ask HiFlight about the making and shipping of it.

Will be getting more than 1 as it won't make sense getting a busy man to make just a single piece and ship it over to Southeast Asia. redface.gif

post #4131 of 4738

Any of you guys know of a dual channel op-amp that is Transparent, have a wide sound stage/sound imaging while being neutral or if I even wording it correctly, I mention dual as I can't Fit Two dual to single dip-8 adapters in the I/V at the same time.

post #4132 of 4738
Quote:
Originally Posted by genclaymore View Post

Any of you guys know of a dual channel op-amp that is Transparent, have a wide sound stage/sound imaging while being neutral or if I even wording it correctly, I mention dual as I can't Fit Two dual to single dip-8 adapters in the I/V at the same time.

THS4032

or 2x SOIC LME49990

post #4133 of 4738
Quote:
Originally Posted by WiR3D View Post

Its probably my fault are you using the AD797, it just sounds so good, but don't be surprised when they break from all the oscillation. :p

 

Note that the oscillation (if any) might also be amplified and output by the TPA6120. I am not sure if there is any lowpass filtering between the I/V stage and the headphone output, but it may very well be that there is none, and the TPA6120 has very high bandwidth. Simplified (incomplete) schematics of how I think one channel of the analog outputs of the Xonar STX is implemented:

 

1000

The graphs at this thread do confirm that the line output indeed has more high frequency roll-off (due to the ~190 kHz lowpass filter in the buffer stage). Interestingly, the headphone output is fully DC coupled, so it is possible for (buggy?) software to output DC to the headphones.


Edited by stv014 - 7/28/12 at 11:32am
post #4134 of 4738
Quote:
Originally Posted by stv014 View Post

 

Note that the oscillation (if any) might also be amplified and output by the TPA6120. I am not sure if there is any lowpass filtering between the I/V stage and the headphone output, but it may very well be that there is none, and the TPA6120 has very high bandwidth. Simplified (incomplete) schematics of how I think one channel of the analog outputs of the Xonar STX is implemented:

 

1000

The graphs at this thread do confirm that the line output indeed has more high frequency roll-off (due to the ~190 kHz lowpass filter in the buffer stage). Interestingly, the headphone output is fully DC coupled, so it is possible for (buggy?) software to output DC to the headphones.

Now that is not good news....

post #4135 of 4738
Quote:
Originally Posted by WiR3D View Post

Now that is not good news....

 

Well, I am not sure if oscillation in the I/V stage is dangerous to the headphone amplifier, and there are some unmarked passive components between the 10 Ω output resistors and the output jack (see picture here) for RF filtering, so I do not know what load impedance the TPA6120 sees in the MHz range. But it is possible.

post #4136 of 4738
Quote:
Originally Posted by stv014 View Post

Well, I am not sure if oscillation in the I/V stage is dangerous to the headphone amplifier, and there are some unmarked passive components between the 10 Ω output resistors and the output jack (see picture here) for RF filtering, so I do not know what load impedance the TPA6120 sees in the MHz range. But it is possible.

Just adds more variables into my equation to determine what killed TPA6120 the thanks for the information as always. 

post #4137 of 4738
Quote:
Originally Posted by formula1 View Post

Do you guys notice the difference between A and B track? 

http://bursonaudioblog.blogspot.com/2012/02/marantz-cd72-hd-opamp-mod-with-sample.html

 

Been considering to mod my CDP with their opamps. 

Thanks. 

 

Can someone give me a detailed explanation what to listen for? I've been going over and over and can't hear a single bit of difference. Maybe I'm just untrained, deaf or then the opamp differences are so small I couldn't care less.

post #4138 of 4738
Quote:
Originally Posted by hekeli View Post

 

 Maybe I'm just untrained, deaf or then the opamp differences are so small I couldn't care less.

I couldn't care less .

IMO, IF you can hear a difference ( and sometimes you can ),

it's because the circuit-design isn't suitable for the op-amp in question (or vice-versa) .

 

EDIT : Or it could be REALLY OLD op-amps, from the 1960's/70's ..

Some of them where absolutely horrible !


Edited by AKG240mkII - 8/1/12 at 7:28am
post #4139 of 4738
Quote:
Originally Posted by hekeli View Post

can someone give me a detailed explanation what to listen for? I've been going over and over and can't hear a single bit of difference. Maybe I'm just untrained, deaf or then the opamp differences are so small I couldn't care less.

Same here... i couldnt hear any significant difference. And when i mean significant i mean significant. 

post #4140 of 4738
Quote:
Originally Posted by stv014 View Post

 

Note that the oscillation (if any) might also be amplified and output by the TPA6120. I am not sure if there is any lowpass filtering between the I/V stage and the headphone output, but it may very well be that there is none, and the TPA6120 has very high bandwidth. Simplified (incomplete) schematics of how I think one channel of the analog outputs of the Xonar STX is implemented:

 

1000

The graphs at this thread do confirm that the line output indeed has more high frequency roll-off (due to the ~190 kHz lowpass filter in the buffer stage). Interestingly, the headphone output is fully DC coupled, so it is possible for (buggy?) software to output DC to the headphones.

do you know how to read schematics? above, there is a low pass RC filter in the negative feedback loop of the NJM which are the IV stage and there is a further low pass in the line out, neither are anywhere near anything that could be defined as a high frequency rolloff. 190khz is far above anything any speaker, headphone or ear is going to process, there is no signal to roll off, just the intended RF filter. there is not even any content up there, its just to prevent RFI and aliasing (artifacts from the oversampling filter) or glitch energy from the dac or environment from getting through and exciting HF oscillation. the software will not have anything to do with it, the use of improperly implemented AD797 will.

 

apologies if i've missed posts that explain/recognize the above. you can indeed kill the buffers with oscillation, perhaps if they arent heatsinked enough to cope with exceeding the SOA with amplified DC. DC can build up on the gates until it is higher than the max voltage. seen it, done it. I was using an instrumentation amp I cobbled together with 3 opamps to measure and amplify the difference in voltage of an AC sinewave between the gate and source of some mosfets I was matching; to increase the accuracy of the reading on my meter by allowing measuring a few Volts, rather than a few mV. this was matching for transconductance for my IV stage

 

the AC signal I was measuring was riding on DC, in a perfect world the DC would have cancelled out as it was the same on both inputs, but as we know its not a perfect world and it built up on the gates. luckily they were just some old LT1028 dip8 spares


Edited by qusp - 8/1/12 at 10:17am
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