[ppl]

has any body tried the New Analog devices Dual Opamp AD-8512? I was thinking about using this as an alternative To the AD-823 (whitch i think has way too mutch grain. in My Pocket Amp since a dual version of the AD-1610 (AD-8620) Is not as of yet available. The AD-8512 is as close as i can come to the 8610. The 8512 has Slew rate and bandwidth similar to the OPA-134 However I do not like the sound of the 134 and it draws alot more Current than the 8512 4 Ma vs 1.5.

 

[morsel]

Hi PPL, I have a couple of AD8512 opamps on order, hopefully they will be showing up next week. They are dual so8, I will need to get some BrownDog so8 to dip adapters for them. Why don't you install a couple of AD8610 opamps on the new BrownDog opamp adapter? I mostly ordered the 8512 out of curiosity, I don't expect it to be better than the 8610. I'm going to compare the 8610, 825, 826, 823, and 8512 in basic CMoy configuration and in the META42 when it comes out. BTW, the 8620 is still vaporware. Even if it does come out it will have diminished specs.

 

[ppl]

Morsel:
Thanks for your reply. What attracted me to this Opamp is reasonable specs at only about 1.5 Ma of supply current Per Opamp. This way less than the 8610 and the 823. Since my Pocket Amp is powered by 9 Volt Ni-Mh every ma Counts. Some where in the data sheet on the 8512 is a comparrison to the OPA-2132. This Opamp had better sound alot better than the 2132 for use in my Pocket Amp. My Ears are overly sensitive to Solid state Grain and trace amounts of it Bother me alot. This is why i generly favor discreet transistor Circuits. However My need to have High Quality Audio away from Home has led me into investigating the finner sonic points of Quality opamps as a serious Gain Block. The AD-8610 is so far the most grain free and natural sounding Opamp i have heared so far. With the right Buffer Other Opamps can be great also but in othern areas. The AD-825 for Digging down into the Micro-details of the Source and recording. Now it is true there are some sounds that should be at the noise level and should not be heared. It is nice to know that if one wants to hear these things it is just a simple matter of equipment and or parts selection. The 823 dual is the best bang for the Ma. It sounds gutsy and dynamic. however it's grain is not what i wish to put up with. The Others you mentioned have there own merits but as is the case with Life the virtues are not without a cost and not just the Price paid.

That all sed and done the reason i did not use the adaptor is that the parts are packed on the board in the Pocket amp, this will not allow any overhang beyond the dimensions of the socket. details like caps are butted up against IC sockets and things, make this look like the transistor radios of Old regarding parts packing.

Please keep us posted regarding your Opamp Findings and thanks for your prompt reply.

 

[morsel]

Hi PPL

"the reason i did not use the adapter is that the parts are packed on the board in the pocket amp, this will not allow any overhang beyond the dimensions of the socket"

One of the major design considerations for the adapter was to make it the same size as a dip socket so you would not have that problem. The specified dimensions are 450 mils square, but measuring actual adapters they are closer to 430 mils square. This should be small enough to fit anywhere a dip would fit.

If your dip socket is exactly 400 mils and you can't have 15 mils of overhang, put some fine sandpaper on a flat surface such as a tabletop and rub each edge of the adapter on the sandpaper to trim it down a bit. There is a beveled border around the edge that is probably an artifact of the process used to cut the boards apart. It is not needed, and you can easily get the adapter below 400 mils square that way. The only trace that comes near the edge is along the bottom of the board. This trace is visible in the photograph under the part number on the top surface. You can also "candle" the adapter to make sure you are not encroaching on the trace by holding it up to a light and looking through it. Having said all that, I would be surprised if you had to trim it down at all.

According to the spec sheets, the quiescent currents are 2.5mA for the 8610 and 1.8mA for the 8512, both per amp. That is not a huge difference, to be able to use your beloved 8610. Still, it will be interesting to compare them. BTW, my 8610 chips came today.

 

[ppl]

Morsel;
Thanks for the reply. i was looking at that Photo more deeper and it might work since my space issue is on the ends of the opamp not the sides. the bypass caps are on the Ends and butted up against the socket. Thay are the Wima box type and as sutch do not move as another type of cap would. But ya i am going to get some and try it.

BTW let us know what you think of the AD-8610 also.

 

[morsel]

The standard SO8 to DIP BrownDog adapters arrived today. I just mounted an AD8512, it is ready for testing. I am good at soldering S08 surface mount chips now, heehee!

I will try to find some time to try the AD8512 in between working on the META42 and all the other stuff. It is hard for me to assess the subtle differences of high end opamps using my aging CD player. I need to upgrade it, I know, it's just that the META42 project is more than a full time job for me. Eventually it will happen.

 

[ppl]

Morsel; thanks please keep me posted. BTW my latest version of my Pocket Amp that i now call The Companion Personal headphone Amplifire is do ne i spent the afternoon Drilling the case and mounting the board. unlake my Previous version everything is on the PC board Including the batteries and holders (2) 9 volts. The sound is slightly cleaner than the early versions maby the Component matching, maby the ground plane or maby all the cabeling going from the board to the Jacks have been replaced by Board foils under gnd plane. all that is left is to cut a frount pannel out of the Old Aluminium Skylight frame i have been using for this porpose. I like the sound of the new unit better and Others love the sound. Next is a AD-823/BUF634 version, constructed the same way.

 

[morsel]

Cool beans, PPL! Show us some pictures or schematics if you can. My AD826 chips finally arrived this morning, but I was up all night getting your cascode circuit on the META42 board and not having room for C5 anymore, so I probably won't get to the opamps today.

 

[ppl]

Ill Will try and have photo's when i can get to someone with a digital camera. Schematic Hum.... maby Well see.

Now What about those AD-8512's From the data sheet it looks like a mixed bag like unless it's a misprint 25Pf of input capacitence will not allow the high Value Input and feedback resistors i like to use but maby thay ment 2.5 Pf. the AD823 has only 1.6pF I should just mount them and see but nowdays i haven't the time.

 

[morsel]

I listened to the AD8512 and it sounded good, perhaps it was a tiny bit brighter than the AD8610, although I can't be sure. I hesitate to say more than that, because I don't have any buffers (yet) and thus am driving my 600 ohm beyerdynamic DT990 headphones directly.

I also tried both AD826 chips in the same circuit I have been using for all the opamps (modified cmoy with TLE rail splitter and film caps close to the opamp power leads). They were unusable due to the 7 Volts DC

at the outputs, so I did not plug in my headphones. I am not sure why the offset is so bad, aside from the fact that the AD826 is a bipolar gravy sucking pig, but I will not be spending any more time investigating this chip until after the META42 is done. It should be a far better test platform.

 

[ppl]

Morsel:
You are trying to do what the person with the LM_xxxx Opamps was trying to do use the wrong device for the job. High input Bias current opamps will not work in a direct Coupled High Impedance Amp.

AD-8512 sounding bright This i like since for some reason my New layout and component Preperation has resulted in an overly warm borderline dark sound quality in stark contrast to my AD8610/EL2008 amp that seems to have alotbetter performance at the frequency Extremes. so I'am looking for Bright But not thin. Gess ill just have to try this, Oh BTW is it cleen?

 

[morsel]

Well I expected problems with the AD826, just not quite so bad. I wanted to dispell the frequent suggestions that it is equivalent to a dual AD825. My test amp is capacitively coupled, not direct coupled, but no matter.

Regarding the AD8512, it is hard for me to say how clean it is because my CD player is not in the best shape and in need of an overhaul, plus, I have no output buffers as I mentioned before, however, my best guess is that it is reasonably close to the AD8610 and worth your time to get some BrownDog adapters and try it out. You can also mount up some of the S08 single opamps on the opamp adapter so you can easily compare all your opamps in one standard test bed. Eventually I will get around to upgrading my CD player output and power supply so I can have a better source to listen to and test with.

Also, the new FastFET™ AD8065 is out now! The dual version AD8066 is scheduled to be out in July. This is a low cost rail to rail opamp so it may not be better than our current favorites, but it is interesting enough to check out.

150MHz BW, 180V/µs slew rate, 7nV/rtHz noise, 5-24V supply range, 6.5mA quiescent current, 30mA output current, rail to rail output, -90dB @1MHz distortion SFDR, PSRR 120 dB, settling time not listed, the pdf is still a preliminary.

http://www.analog.com/productSelecti...8065_6_prk.pdf

 

[PhopsonNY]

Hi there,

Sorry to intrude on your conversation, but I am very interested inthis exchange esp with respect to the Ad8512 and the ad8610.

As I have repeorted in other forums, I have been trying to upgrade my cd player's I/V conversion chips from their original opa 2604s.

At your recommendation from diyaudio, I tried the ad8610. This sounded wonderful, but unfortunately, my voltage rails are at 16.6v and soon the ad8610s burnt out

.
I am currently trying out the ad825s which do sound quite good, but not as sweet as the ad8610s.

I am wondering if in your opinions, the the ad8512s are even worth trying out as being closer to the ad8610s?

would the new range of fastfets such as the 8065s you mention be worth checking out?

any ideas are appreciated.

thanks

 

[morsel]

Hi Phopson,

Sorry about your opamps burning out. I did post a warning about the low max voltage on the 8610 somewhere, but there are so many threads it is hard to keep track of them all.

The AD8512 is rated for ±15V, with ±18 absolute maximum rating, so it should work. I wonder why your CD player rails are so high. At any rate, yes, do try the AD8512 and let us know what you think. If they don't work out you can always fall back on the AD825. I have not tried the new FastFET series opamps yet, although I plan to. If you have the time and inclination, go for it!

 

[PhopsonNY]

Hi and thanks much for the encouragement.

I am currently testing out the ad825 as a replacement for the 8610s. In the meantime, I am tackling another issue.
I know this is not the best way to do this, but I wmay not have time to get to this for a while.

My big question is this...

The basic description of the Sony's audio circuit as it now stands is;

AD825s as i/v >> opa 2132 as mix (balanced to unbalaced) >>
ad712 as buffer/servo.

Research suggests that the ad712s might be a weak link and I suspect a significant factor in the sonic signature of the unit.

One half fo the ics act as the output buffer and final gain stage and the other half of each chip acts as the dc servo.

The chips are implemented as so8s so I am limited to a dual so8 as a replacement.

The two choices I have limited the replacements to are
the opa2604...reportedly very musical and
the ad8512...new kid on the block...better electronic specs if ad8610 is anything to go by, then very good sounding.

Please suggest the best one to try.

Any suggestions would be appreciated.

TIA