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Old 2nd December 2007, 07:51 PM   #1
LNeilB2 is offline LNeilB2  United States
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Default Opamp Comparisons

Hello all,

I picked up a link DACIII on the cheap. Sounds ok, midrange seems slightly hard and glassy. I'm planning to pick up the powerbase to see if that helps, but I also figured an opamp swap might be in order.

Many reference the LT 1364, but I've seen comments that this sounds a bit lean, which is the opposite of what I'm looking for. That said, any opinions on the AD or BB options? I'd be happier with warm, or even bloated sounding opamps (as opposed to the current sound I'm getting).

Thanks in advance,

Neil
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Old 2nd December 2007, 08:32 PM   #2
gootee is offline gootee  United States
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Please remember that the circuitry around the opamp (and before and after it) is often at least as important as the opamp itself, and is often tailored, by the original designer, for a specific opamp. So it often wouldn't make sense to just blindly substitute another opamp. Similarly, judging the sound of such a circuit when a different opamp is substituted is not a valid test of the opamp. Having said that, if you can find another opamp that sounds better to you, and can operate within its specifications in your circuit, then go for it.

- Tom Gootee

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Old 2nd December 2007, 11:17 PM   #3
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Default Re: Opamp Comparisons

Quote:
Originally posted by LNeilB2
Hello all,

I picked up a link DACIII on the cheap. Sounds ok, midrange seems slightly hard and glassy. I'm planning to pick up the powerbase to see if that helps, but I also figured an opamp swap might be in order.

Many reference the LT 1364, but I've seen comments that this sounds a bit lean, which is the opposite of what I'm looking for. That said, any opinions on the AD or BB options? I'd be happier with warm, or even bloated sounding opamps (as opposed to the current sound I'm getting).

Thanks in advance,

Neil
I too thought the LT1364 lean and hard, in the DACIII, you will love the Analog Devices OP275 very smooth big and generous, sort of like a good tube amp. And the DAC3 needs an opamp like that because with any of the super dynamic up front opamps it will sound fatiguing, even with better power supplies or as I did total battery power.
Also the OP275 has almost zero dc offset which aloud me to cut out the dc servo from the output stage, and keep it dc coupled, which maybe helped the sound a little more as well I think. (somebody once said dc servo can sound bad) anyway I was able to cut it out by using the OP275.

Cheers George
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Old 2nd December 2007, 11:26 PM   #4
LNeilB2 is offline LNeilB2  United States
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Default Re: Re: Opamp Comparisons

Quote:
Originally posted by georgehifi


I too thought the LT1364 lean and hard, in the DACIII, you will love the Analog Devices OP275 very smooth big and generous, sort of like a good tube amp. And the DAC3 needs an opamp like that because with any of the super dynamic up front opamps it will sound fatiguing, even with better power supplies or as I did total battery power.
Also the OP275 has almost zero dc offset which aloud me to cut out the dc servo from the output stage, and keep it dc coupled, which maybe helped the sound a little more as well I think. (somebody once said dc servo can sound bad) anyway I was able to cut it out by using the OP275.

Cheers George

Now this sounds like a plan! Did you have to mod the opamp circuits in order to accomplish the above?

Thank you very much for your reply!

Neil
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Old 3rd December 2007, 12:55 AM   #5
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Default Re: Re: Re: Opamp Comparisons

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Originally posted by LNeilB2



Now this sounds like a plan! Did you have to mod the opamp circuits in order to accomplish the above?

Thank you very much for your reply!

Neil
Not at all, but you will need the circuit diagram to do it, and here it is.
And if you want something more dynamic and detailed and more etched than the OP275 use the AD825 on brown dog boards.

I did this (below) over 3 years ago .

Note: one half of the opamp is the dc servo, just cut it out and set up what's left, +input (pin 3) to deck (earth)
I think for memory that's all I had to do to get rid of the dc servo, but just to be safe for now, just change out the opamp you have for the OP275 or the AD825's on brown dogs and listen with the dc servo.


Cheers George
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Old 21st January 2008, 07:32 AM   #6
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Default musical fidelity A3 24 DAC

Sorry for interjecting off-topic. Wanted to get feedback (or up-date) from Georgehifi regarding latest mod recommendations for the MF A3 24: Op amps, clock etc. I have just seen his postings on subject from a couple of years ago and I was wondering if he still owns that unit and has continued modifying it. I would have send him a PM but I just registered and the system does not allow me to do that until I have made several postings. Perhaps some one can forward this query to him on my behalf (will be most appreciated).

Munosmario
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Old 21st January 2008, 09:06 AM   #7
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Munosmario hi, the MF A3.24 was almost maxed out with these mods
http://www.diyaudio.com/forums/showt...154#post649154
and should get a better again with the Tent XO2 @ 45.1584 MHz + Tent XO power supply
http://www.diyaudio.com/forums/showt...95#post1186195

I have since then found a cheap ($499aud) Harman Kardon HD970 cd player (AD1955 dac chip), which can also be used as a separate dac.
It moded with a discrete Transimpedance I/V stage and discrete class A output stage, beat the A3.24 handily, the A3.24 would still be with me though if not for this stunning HK HD970.

Then I made up an AD1955 Eval board it too is there with the HD970 but a little more laid back
http://www.diyaudio.com/forums/showt...60#post1297060

Cheers George
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Old 22nd January 2008, 07:36 AM   #8
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Georgehifi, many thanks. From your reply and your other posts it appears that you did not get to implement the clock (and its PSU) upgrade in your MF A3 24 (you don’t mention at all having done it and/or evaluated it). So, all the mods you actually implemented (and stayed with until you encounter the HK HD970) were the direct coupling and the replacement of the NE 5532’s with the AD825’s mounted on Brown dogs. Accordingly, a direct aural experience with a Tent’s clock moded MF A3 24 is actually an unknown commodity to you—your know about its sonic effect mainly by reference from Guido Tent who has done it for a client. Is my understanding correct? In any event (putting aside the temptation to somehow get my hands on a HK HD970, not available in the US) I am contemplating carrying your suggested mods all the way including upgrading the clock. However, I am thinking more towards using the Audiocom Superclock IV (not the Tent’s clock set you mention). It appears to work very well in applications where the AD 825’s are present (including several of the recent MF players and DACs). Any words of wisdom?

As you experiment with boards, rather than putting them in metal cases, perhaps, you may be interested on the way Altmann of Altmann Micro Machines mounts his Kilo-Euro creations on slabs of lacquered white spruce (legs are just little wood knobs). Mother-of-tone is his theme and the domain for his website…interesting stuff there.

http://www.mother-of-tone.com/creation.htm

Cheers……Munosmario
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Old 22nd January 2008, 07:51 AM   #9
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If I kept the A3.24 I would of ended up instaling a Tent XODAC and power supply, and slaving the transport to the dac, even better than just re-clocking the dac with an XO2.

http://www.tentlabs.com/Products/DAC...DAC/index.html

Cheers George
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Old 22nd January 2008, 02:46 PM   #10
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Thanks, Georgehifi. Question, does the TentsLink mode described in the Tent's site accomplishes the same as the slave/master mod you suggest?

http://www.tentlabs.com/InfoSupport/page25/page25.html

Cheers....Munosmario
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