The AD-744 when used with a Buffer and only when the Compensation pin is used to drive the Buffer dose the AD-744 sound great. in this instamce i like it Better than the OPA-627 since some small sonic issues with the OPA-627 can call attention to it. these issues are not great and only on some Music will this be noticed on the OPA-627. The AD-744 when operated as above is smoother and slightly more musical. On it's own and or going through its own output stage the AD-744 looses most of its charm.
Regarding the AD-711 & AD-712. these were great in the 1980 and like the OPA-2107 were great upgrades to the standard BI-Fet (tm) like the TLO-82. i have not compaired these to newer ones in a long time. However i do still have these installed in an Active filter i use for my Vented Loudspeakers.(2ed order Butterworth with a user controlable Peak) and i at the Moment do not recall anything bad about them (711 & 712). this type of Filtering is what was recomended in A.N. Thiele's (Loudspeakers in Vented Boxes J.A.E.S. 1971) but Thiele's notation discribed modifying the Feedback loop of the Power Amp for this. I used the AD-712 Dual Op Amp for this task. Electrovoice and B & W have also used this type of filter But maby a Different semiconductor complement.
I have some AD-712 Duals still new and unused in the TO-99 Metal can i will try that in the socket of My pocket headphone Amp and compare it to the AD-8620 sometime. the SMT AD-8620 i soldered into a Dip socket so as to adapt it into this amp that was using the AD-823. the AD-8620 is alot better than the AD-823 and I used to think the AD-823 was great. But in comparison to the 8620 the 823 has alot of grain that is totaly absent on the 8620. Moreover the Dual AD-8620 sounds almost as good as it's single counterpart the AD-8610, This is also somthing most duals do not do as the Singel versions of most Op Amps are more stable and sound Better. with the AD8610/20 I really cant tell the Difference when Both are on the Same power supply and Decoupling network. But if separate decoupling networks are used for each opamp then the singel is notably Better in Air and Depth of the Musical image. By Decoupling networks i am refering to the Bypass capacitors from the Power supply pins to gnd and a 10-100 ohm series resistor from this to the Power supply rail.
One note on Buffering, in addition to the LT-1010 several alternatives are available like the Bur Brown BUF-634 and the OPA-633. the Intersil HA-5002 and HA-5033 are Also nice but have no output protection, But some or shall i say alot of people do not like Output current limiting anyway.
I hope you can make sence out of this.
Regarding the AD-711 & AD-712. these were great in the 1980 and like the OPA-2107 were great upgrades to the standard BI-Fet (tm) like the TLO-82. i have not compaired these to newer ones in a long time. However i do still have these installed in an Active filter i use for my Vented Loudspeakers.(2ed order Butterworth with a user controlable Peak) and i at the Moment do not recall anything bad about them (711 & 712). this type of Filtering is what was recomended in A.N. Thiele's (Loudspeakers in Vented Boxes J.A.E.S. 1971) but Thiele's notation discribed modifying the Feedback loop of the Power Amp for this. I used the AD-712 Dual Op Amp for this task. Electrovoice and B & W have also used this type of filter But maby a Different semiconductor complement.
I have some AD-712 Duals still new and unused in the TO-99 Metal can i will try that in the socket of My pocket headphone Amp and compare it to the AD-8620 sometime. the SMT AD-8620 i soldered into a Dip socket so as to adapt it into this amp that was using the AD-823. the AD-8620 is alot better than the AD-823 and I used to think the AD-823 was great. But in comparison to the 8620 the 823 has alot of grain that is totaly absent on the 8620. Moreover the Dual AD-8620 sounds almost as good as it's single counterpart the AD-8610, This is also somthing most duals do not do as the Singel versions of most Op Amps are more stable and sound Better. with the AD8610/20 I really cant tell the Difference when Both are on the Same power supply and Decoupling network. But if separate decoupling networks are used for each opamp then the singel is notably Better in Air and Depth of the Musical image. By Decoupling networks i am refering to the Bypass capacitors from the Power supply pins to gnd and a 10-100 ohm series resistor from this to the Power supply rail.
One note on Buffering, in addition to the LT-1010 several alternatives are available like the Bur Brown BUF-634 and the OPA-633. the Intersil HA-5002 and HA-5033 are Also nice but have no output protection, But some or shall i say alot of people do not like Output current limiting anyway.
I hope you can make sence out of this.
Cheap trick
The AD8610 / 8620 are wonderfully stable, and for audio can be soldered (if you're good with a soldering iron) to a standard DIP header or even an 8 pin DIP socket.
I solder some fine wire (component leg offcuts) into the socket holes, then bend the wire to form a platform for the SMD device to sit on.
It takes skill, but is easy after a while and you only need to solder the used pins - if interested I can post a pic, but even in this less-than-ideal mounting method they will sound much better than most alternatives.
Andy.
The AD8610 / 8620 are wonderfully stable, and for audio can be soldered (if you're good with a soldering iron) to a standard DIP header or even an 8 pin DIP socket.
I solder some fine wire (component leg offcuts) into the socket holes, then bend the wire to form a platform for the SMD device to sit on.
It takes skill, but is easy after a while and you only need to solder the used pins - if interested I can post a pic, but even in this less-than-ideal mounting method they will sound much better than most alternatives.
Andy.
AD744
ppl,
thanks for relating your experiences - I'm about to build the Jung AD744 / AD811 line stage, primarily out of curiosity, it will be interesting to hear the results using the multiple feedback approach used on this stage.
AD811's are only readily available in SMD packages now, but the AD744 is still available, and that comp. pin is so useful....
Andy.
ppl,
thanks for relating your experiences - I'm about to build the Jung AD744 / AD811 line stage, primarily out of curiosity, it will be interesting to hear the results using the multiple feedback approach used on this stage.
AD811's are only readily available in SMD packages now, but the AD744 is still available, and that comp. pin is so useful....
Andy.
ALW> as you may recall from my headwize posts that one of my First Portable Headphone Amps used the AD-744 with the Comp pin driving the BUF-634. This was using Walt's Multi-Loop Technique. His method is about the Best configuation yet for Obtaining The best sound an Op Amp Based Design can offer.
As for great sounding Op-Amps that can be used as stand alone gain stages for Line Level use and also are available in DIP's are the OPA-627, AD-845, AD843, LT-1122. For closed loop gains of 10 or greator than the OPA-637 is real nice and offers slight improvements in transparency over the OPA-627.
However the New AD-8610/20 are sonicaly about the Best available but are only SMT. The AD-843 is one op amp to look into if Dynamics as well as Microdynamic performance is required in a DIP package. Also consider the Intersil HA-5221 if Bipolar rather than FET inputs are needed. this Op Amp has low input Bias currents so will work with the High Source resistor values typical of Audio use. The Dual version of this the HA-5222 is not well mannered and can become unstable if not treated just right. The Single version is quite easy to apply if minimum amount of care in layout and bypassing are used. this devices 50 mA of available output current also lend itself to stand alone unbuffered applications.
As for great sounding Op-Amps that can be used as stand alone gain stages for Line Level use and also are available in DIP's are the OPA-627, AD-845, AD843, LT-1122. For closed loop gains of 10 or greator than the OPA-637 is real nice and offers slight improvements in transparency over the OPA-627.
However the New AD-8610/20 are sonicaly about the Best available but are only SMT. The AD-843 is one op amp to look into if Dynamics as well as Microdynamic performance is required in a DIP package. Also consider the Intersil HA-5221 if Bipolar rather than FET inputs are needed. this Op Amp has low input Bias currents so will work with the High Source resistor values typical of Audio use. The Dual version of this the HA-5222 is not well mannered and can become unstable if not treated just right. The Single version is quite easy to apply if minimum amount of care in layout and bypassing are used. this devices 50 mA of available output current also lend itself to stand alone unbuffered applications.
I was digging through one of my op-amp drawers the other night (next to my socks! just kidding), and came across some chips that I held in high regard about 10-15 years ago, made by a company in AZ called Analog Systems.
I grabbed a AS336 dual "quiet-fet" chip in TO-99 steel can, and proceeded to replace the output/filter chip in a technics cd player in my bedroom system (i think an slp-170?). The D/A I to V chip is an AD826, and the output was a Burr Brown OP2604. (I had also added a +15 -15 supply separate from the internal supply a couple of years ago.)
Holy Hanna!!
The swap made that old p.o.s. cd player sound absolutely incredible. Sounded even better tonight! Incredible and deep low end, very realistic vocals, detailed but very smooth high end, precise imaging, 3d; all of the usual mega hi-fi stuff. I was so astonished, I put the OP2604 back in...blah. I put an Op2134 in...a little better, but still blah. An OP275..AD712..NE5532....then back to the AS336...
As I only have a limited number of these, and some of their other chips I quickly checked the web for a site....none so far, but I did find a web site that had their address. I'll try and get some more info.
Has anyone any experience with these chips? They also had a 332, 334, and a couple of other interesting FET and Bilpolar input chips, all high quality low noise.
I grabbed a AS336 dual "quiet-fet" chip in TO-99 steel can, and proceeded to replace the output/filter chip in a technics cd player in my bedroom system (i think an slp-170?). The D/A I to V chip is an AD826, and the output was a Burr Brown OP2604. (I had also added a +15 -15 supply separate from the internal supply a couple of years ago.)
Holy Hanna!!
The swap made that old p.o.s. cd player sound absolutely incredible. Sounded even better tonight! Incredible and deep low end, very realistic vocals, detailed but very smooth high end, precise imaging, 3d; all of the usual mega hi-fi stuff. I was so astonished, I put the OP2604 back in...blah. I put an Op2134 in...a little better, but still blah. An OP275..AD712..NE5532....then back to the AS336...
As I only have a limited number of these, and some of their other chips I quickly checked the web for a site....none so far, but I did find a web site that had their address. I'll try and get some more info.
Has anyone any experience with these chips? They also had a 332, 334, and a couple of other interesting FET and Bilpolar input chips, all high quality low noise.
Re: AD744
Try the LM6181 then, National's
equivalent for the AD811, with the benefit of a lower supply current and, maybe just in my imagination, better-behaved overall.
My own present linestage is a 100k Panasonic pot feeding an AD744/LM6181 combo with - 3 - feedback loops. Sounds very sweet and smooth.
(The alternative path in the same box is
a 389-based FET buffer).
ALW said:
Try the LM6181 then, National's
equivalent for the AD811, with the benefit of a lower supply current and, maybe just in my imagination, better-behaved overall.
My own present linestage is a 100k Panasonic pot feeding an AD744/LM6181 combo with - 3 - feedback loops. Sounds very sweet and smooth.
(The alternative path in the same box is
a 389-based FET buffer).
Attachments
The BUF-634/AD-744 is only on hard copy However i have posted a newer Headphone Amp Based upon Walt Jungs Multi-Loop Feedback articals in 1998 EDN" Walt's Tools and Tips"
this version is Based upon a pair of Gutsy and extreamly articulate sounding Buffer that some have called Too Hot in the High End. However this quality is perfect for the normaly Dark sounding Portable Devices it is used with. However on Quality Cleen recorded SACD's and DVD's the involvement is captivating and Draws about 27 MA of Quesent Current. However I can't stand this amp un My computors MP3's via a Audigy with AD-8620 opamps replacing the 4558 types installed from the Factory. In this case the less Hot sounding BUF-634 sounds better in this Amp than the HA-5002 But if a cleen and potent High end that seems to extend forever beyound what Humans can hear and the Ability to resolve the last Bit of imfromation from High resolution Sources then the HA-5002 is my choice. Eather way the same Topology works with eather.
Sonicaly the AD-8610/20 are Better than the AD-744 evean using the comp pin. the resolution is improved over the 744 with the 8610 and the Dual AD-8620 is alot better sounding that the Dual AD-744 the AD746. With the 746 lacking the ability to use the comp pin since that is unavailable on the Dual. Plus the 8620 runs on about 2/3 the current of the Older Analog devices part.
this version is Based upon a pair of Gutsy and extreamly articulate sounding Buffer that some have called Too Hot in the High End. However this quality is perfect for the normaly Dark sounding Portable Devices it is used with. However on Quality Cleen recorded SACD's and DVD's the involvement is captivating and Draws about 27 MA of Quesent Current. However I can't stand this amp un My computors MP3's via a Audigy with AD-8620 opamps replacing the 4558 types installed from the Factory. In this case the less Hot sounding BUF-634 sounds better in this Amp than the HA-5002 But if a cleen and potent High end that seems to extend forever beyound what Humans can hear and the Ability to resolve the last Bit of imfromation from High resolution Sources then the HA-5002 is my choice. Eather way the same Topology works with eather.
Sonicaly the AD-8610/20 are Better than the AD-744 evean using the comp pin. the resolution is improved over the 744 with the 8610 and the Dual AD-8620 is alot better sounding that the Dual AD-744 the AD746. With the 746 lacking the ability to use the comp pin since that is unavailable on the Dual. Plus the 8620 runs on about 2/3 the current of the Older Analog devices part.
Attachments
What it Looks Like
This is what the Innered's of the Amp based Upon the Previous Schematic looks like.
This Amp Has and AD-8620 soldered into a DIP socket and then pluged into another Dip socket upon the Board. The Volume control is the 9 mm Bourns 51 series conductive plastic, Generic Low Z Electrolytic's. and Wima MPK-10 Polypropylene Bypasses.
This is what the Innered's of the Amp based Upon the Previous Schematic looks like.
This Amp Has and AD-8620 soldered into a DIP socket and then pluged into another Dip socket upon the Board. The Volume control is the 9 mm Bourns 51 series conductive plastic, Generic Low Z Electrolytic's. and Wima MPK-10 Polypropylene Bypasses.
Attachments
Try discrete
I have given up on opamps....I know that maybe with the right current feedback op amp, etc. that I might get great sound, but I have yet to hear it from an op amp. Over 25 years of listening including just about every one mentioned in this thread (8610 most recently). The 8610 as I-V converter still sounds solid state. slightly hard and emphasizing the transient over the decay.....A very simple discrete all fet stage sounds more purely detailed, palpable and real.....no question.... and this has been my experience for years.....I was hoping that the 8610 would be killer, but returning to a discrete super simple all fet single ended class A stage makes me grin.....sounds like real music again. Oh well. What is interesting is that this kind of stage does not cost much more than an op amp.....The transistors are cheap, just the very very few Vishay and Caddocks make it slightly pricey. My circuit it proprietary, but you can make fairly simple discrete op amp circuits by looking at the Pass labs DIY site and downloading the article on discrete op amps.....Have fun.....
Ric Schultz
I have given up on opamps....I know that maybe with the right current feedback op amp, etc. that I might get great sound, but I have yet to hear it from an op amp. Over 25 years of listening including just about every one mentioned in this thread (8610 most recently). The 8610 as I-V converter still sounds solid state. slightly hard and emphasizing the transient over the decay.....A very simple discrete all fet stage sounds more purely detailed, palpable and real.....no question.... and this has been my experience for years.....I was hoping that the 8610 would be killer, but returning to a discrete super simple all fet single ended class A stage makes me grin.....sounds like real music again. Oh well. What is interesting is that this kind of stage does not cost much more than an op amp.....The transistors are cheap, just the very very few Vishay and Caddocks make it slightly pricey. My circuit it proprietary, but you can make fairly simple discrete op amp circuits by looking at the Pass labs DIY site and downloading the article on discrete op amps.....Have fun.....
Ric Schultz
Oh, yes...
I have given up too.
Given up on dome tweeters and ribbon tweeters.
All crap.
Sounds like a whole cannery.
Plazma makes the world go round.
And its such a big improvement that the OP hunting gets senseless waste of time.
Hey, did You know that ceramic packages sound better ?
Bernhard
Although I agree with Ric Schultz that a discrete circuit _can_ultimately_ sound better than monolithic opamps, I find that the board layout and physical construction issues make a huge difference to how any circuit sounds, and this includes discrete semiconductors, tubes and opamps.
An opamp-based circuit with a good power supply, good board layout and good physical construction will sound more "analog-like" than an indifferent tube design - including some commercial high-end products. You don't need audio-grade components to accomplish this - intelligently chosen industrial and mil-spec components are quite sufficient.
OTOH, I find that without exception, the more effort I put into the board layout and physical construction issues, the better the results. And this is not only my opinion - Keith Herron told me that for some of his products, he has spent over a year designing and iteratively testing the board and construction aspects.
jonathan carr
PS. good to see you back, Bernhard!
An opamp-based circuit with a good power supply, good board layout and good physical construction will sound more "analog-like" than an indifferent tube design - including some commercial high-end products. You don't need audio-grade components to accomplish this - intelligently chosen industrial and mil-spec components are quite sufficient.
OTOH, I find that without exception, the more effort I put into the board layout and physical construction issues, the better the results. And this is not only my opinion - Keith Herron told me that for some of his products, he has spent over a year designing and iteratively testing the board and construction aspects.
jonathan carr
PS. good to see you back, Bernhard!
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