[Zaubertuba]

Quote:

Originally Posted by leeperry /img/forum/go_quote.gif well, I read majkel saying that single op-amps usually yield better results than dual, simply because nothing's shared between the 2 channels?!...

Quote:

Originally Posted by Filburt /img/forum/go_quote.gif You're certainly welcome to try the single to dual route but I don't care for the layout on those adaptors. I'm not sure it would materially improve crosstalk, though. I don't know what majkel means by "nothing's shared"; if you're using a single to dual adaptor, you're still using the same source of power for both and issues such as common mode signals are still present....

Sorry to dredge up ancient postings, guys, but I'm interested in experimenting with rolling opamps on my balanced a47. I'm currently running OPA2134's in it at +-12.5v. I'm using a cheap switching computer power supply (it's variable from 9-25v) feeding a TLE2426/BUF634 rail-splitter. I actually like the warmth of the 2134's but have severe upgraditiss when greater detail can be had, and am really looking for a broader soundstage. Tangent posted this in a (much more ancient) thread:

Quote:

Originally Posted by tangent A big contributor to a wide soundstage is a high channel separation. There are a couple of things influencing channel separation, including: 1. The op-amp (single or dual) 2. Routing of wires on the board (do you have paralleled wires from different channels?) 3. Impedance of the ground path (alkalines vs. rechargeables, earth ground vs. virtual ground, various virtual ground strategies vs. each other...)

FWIR, it seems like the DIFET opamps that are so popular on here may be a good bet, but the price adds up really quickly when my circuit requires 4 duals (or 8 singles

). Where soundstage is concerned, could I get reasonable results "browndogging" or otherwise adapting my circuit for cheaper, but still well-regarded singles? Or would I be better off biting the bullet and getting 4 dual DIFETs?

 

[crapback]

In my zero, I get the best soundstage with AD797brz's in the dac and 2 LT1361's in the amp section. I've tried a number of opamps in the amp and the 1361's have by far the best stereo separation but that's just in my lowly zero.

 

[murrays]

Quote:

Originally Posted by Zaubertuba /img/forum/go_quote.gif Sorry to dredge up ancient postings, guys, but I'm interested in experimenting with rolling opamps on my balanced a47. I'm currently running OPA2134's in it at +-12.5v. I'm using a cheap switching computer power supply (it's variable from 9-25v) feeding a TLE2426/BUF634 rail-splitter. I actually like the warmth of the 2134's but have severe upgraditiss when greater detail can be had, and am really looking for a broader soundstage. Tangent posted this in a (much more ancient) thread: FWIR, it seems like the DIFET opamps that are so popular on here may be a good bet, but the price adds up really quickly when my circuit requires 4 duals (or 8 singles ). Where soundstage is concerned, could I get reasonable results "browndogging" or otherwise adapting my circuit for cheaper, but still well-regarded singles? Or would I be better off biting the bullet and getting 4 dual DIFETs?

There are more subtle issues than just the quoted "separation" of a dual device. (See if you can track down Walt Jung's articles on audio op-amps). There are many paths that act as inputs and can couple signals. The power supply is a common one. A dual device must share its power supply - that is one thing you cannot split. So you must do the best you can with regulation and bypassing. Any ripple or noise imposed on a power rail by one half can affect the other half. Another subtle coupling path is thermal effects. Also there is layout, as mentioned by Tangent.

If you decide to replace a dual device with two singles you will not reap full benefit unless you can also implement independent power supplies. That can be done with local regulators near each op amp. The best / most extreme separation is to go full "dual mono" - two independent mono amplifiers with nothing shared (well, maybe the transformer).

 

[majkel]

The dual op-amps have some common circuitry like current mirrors which may cause some crosstalk, and another source of crosstalk is proximity of the circuits in the silicon die. BTW, it's audible when you try 2x OPA228 against OPA2228. Also, some more sophisticated op-amps don't appear in dual packages due to power density, die dimensions or guaranteed parameters.
Dual op-amps are often intended as differential amplifiers of a single signal, and in those cases the crosstalk is something you don't care for. Only cheapest DACs and CD players make use of one dual op-amp for both channels, in normal cases it's a separate chip or chips for each channel.

 

[Cynips]

Just got my OPA1612AID's delivered (much to my surprise as I was told they were backordered to Sep 15), so now I need to set my soldering skills to the test. Anyone have a link to a good soldering guide for these things? Or maybe can give me a few pointers as to what to think about?

 

[leeperry]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif Only cheapest DACs and CD players make use of one dual op-amp for both channels, in normal cases it's a separate chip or chips for each channel.

I guess the I/V on the PCM1792 is not shared? one DIP8 chip/channel? only the buffer would?

and I need to document myself about the AK4396 buffers, there's 3 of them on my card...so the last one has to be shared.

PS: I'm glad to read that the AK4396 has a fixed 128X oversampling rate...it's 64X by default on the PCM1792, it can be raised to 128X for <96KHz but most implementations don't seem to bother(Asus included).

 

[SpudHarris]

Well I spent an evening in the company of 2 # LT1677's last night and again today but not so critically. I have to say of the LT OpAmps I've sampled I like this one the most. It's very detailed but not harsh or fatiguing, well suited to the Psy/Electronic Genre (Shpongle, Flooting Grooves, Dymons, Bluetech, Kaya Project etc...). Not overly expensive either (£5 each) for what they are. Veeeeeery Nice

 

[ROBSCIX]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif The dual op-amps have some common circuitry like current mirrors which may cause some crosstalk, and another source of crosstalk is proximity of the circuits in the silicon die. BTW, it's audible when you try 2x OPA228 against OPA2228. Also, some more sophisticated op-amps don't appear in dual packages due to power density, die dimensions or guaranteed parameters. Dual op-amps are often intended as differential amplifiers of a single signal, and in those cases the crosstalk is something you don't care for. Only cheapest DACs and CD players make use of one dual op-amp for both channels, in normal cases it's a separate chip or chips for each channel.

I have found the same based on my testing and others I have spoke with on the subject. Single channel units used in a dual channel configuration for instance will sound better then it's dual channel brother. As you said though many of the higher grade opamps dsigned or meant for audio only come in single channel versions.

 

[ecclesand]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif I have found the same based on my testing and others I have spoke with on the subject. Single channel units used in a dual channel configuration for instance will sound better then it's dual channel brother. As you said though many of the higher grade opamps dsigned or meant for audio only come in single channel versions.

Interesting. Does anyone know what the single version of the LT1057 is? Is it the LT1007? I want to buy some of the single channel equivalents of the LT1057 and LT1678 since they sound the best to my ears.

 

[Cynips]

Quote:

Originally Posted by Cynips /img/forum/go_quote.gif Anyone have a link to a good soldering guide for these things? Or maybe can give me a few pointers as to what to think about?

Did some research, so in case someone is interested here's what I found with a link to a bunch of video tutorials even

 

[ROBSCIX]

Quote:

Originally Posted by Cynips /img/forum/go_quote.gif Just got my OPA1612AID's delivered (much to my surprise as I was told they were backordered to Sep 15), so now I need to set my soldering skills to the test. Anyone have a link to a good soldering guide for these things? Or maybe can give me a few pointers as to what to think about?

Soldering SOIC are pretty easy once you get a good technique going.

I usually use a touch of Quad Eucetic solder to the one corner pad on the adapter..just a bit.
Then put the opamp in position. Touch the pad with the solder, this should tack the opamps down.
If it doesn't line up properly, heat and move the opamp into proper position.
Proceed to go to the other side, criss, crossing the corners, then solder down the rest.

I prefer Cardas solder for these as it has a very low melting point and you can get good joints very fast.
Also seems to work the best for my needs anyway.
Heat the joint the touch quickly with the solder -a dab will do you. Simple once you get the idea and the movement down.
Poeple have different methods but it is usually a revamp on the above technique.

Make sure you keep pin one oriented properly and inspect your work afterwards for solder bridges or other poor joints. If everything looks good then test the unit out.

I can solder a SOIC unit in under a minute. I have had lots of practice with the iron though. I think some other will also offer you pointers.

 

[Cynips]

Thanks for the input ROB. Helpful as always!

The guy in that video tutorial I linked to is actually doing a SOIC8 opamp amongst other things, so I recognize some of what you're describing. I'll take the solder make suggestions into consideration and do a trip downtown tomorrow since I need to pick up a few other things anyway.

 

[ROBSCIX]

Everybody who solders seem to have their favorite brands. I use Cardas Quad Eucetic for my audo circuits. Mainly because for me, it is so easy to work with and melts at very low temp compared to others making it great for these smaller circuits.
However, use whatever works for you.

 

[Robin W.]

My opinion of LT1057...
Quite detailed, but VERY relaxed/laid back sound using HD650's. I fell asleep.
More engaging but remaining smooth with HF2's.
Not really my taste overall, however I imagine this could provide an amazing synergy with the right 'phones.

 

[ecclesand]

Quote:

Originally Posted by rwaudio /img/forum/go_quote.gif My opinion of LT1057... Quite detailed, but VERY relaxed/laid back sound using HD650's. I fell asleep. More engaging but remaining smooth with HF2's. Not really my taste overall, however I imagine this could provide an amazing synergy with the right 'phones.

It sounds fantastic with the RS2.