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Opamp advice for a PCM1704 based DAC stage?

post #1 of 12
5/2/10 at 1:51pm
Thread Starter 
Can anyone familiar with opamp modding give me some advice please?

Ive never modded anything and so got lost in the 179 pages of the opamp thread as to what opamp options would be best for a Denon DVD-5000 which has:

Burr-Brown PCM1704J DACs are used, two per channel; μPC4570C's do the l/V conversion; Analog Devices OP-275 op-amps do the differential-to single-ended conversion. A GIC filter is built with the two opamp sections of an NE5532. Another OP-275 buffers the output and is coupled to the output with back-to-back electrolytics bypassed with a smaller film capacitor.

What opamp changes would you suggest to replace:

a. OP-275 for the differential-to single-ended conversion (one OP-275 per channel)

b. NE5532. as a GIC filter (built with the two opamp sections of a single NE5532)

c. OP-275 - another pair buffers the output
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post #2 of 12
5/2/10 at 3:19pm
I think you'd wanna try an adapter w/ two OPA627BP/OPA827/AD797BR/LT1028ACN8/ADA4627-1B
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post #3 of 12
5/2/10 at 8:04pm
Thread Starter 
Quote:
Originally Posted by leeperry View Post
I think you'd wanna try an adapter w/ two OPA627BP/OPA827/AD797BR/LT1028ACN8/ADA4627-1B
Thanks for that - any affordable adaptors you could recommend ( I will need five) and a source?

Like is this genuine:

Two 2x Mono to Dual OPAMP 2x OPA627 -> NE5532 OPA2604 - eBay (item 300423389790 end time May-31-10 14:39:16 PDT)
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post #4 of 12
5/2/10 at 8:58pm
that's OPA626AU, you want BP...B is higher grade than A

any of these two will do:
Single-to-dual Op-AMP Adapter - DIP version (p/n 021001)
Single-to-dual Op-Amp Adapter (p/n 020302)
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post #5 of 12
5/3/10 at 11:47am
Quote:
Originally Posted by Nada View Post
Can anyone familiar with opamp modding give me some advice please?

Ive never modded anything and so got lost in the 179 pages of the opamp thread as to what opamp options would be best for a Denon DVD-5000 which has:

Burr-Brown PCM1704J DACs are used, two per channel; μPC4570C's do the l/V conversion; Analog Devices OP-275 op-amps do the differential-to single-ended conversion. A GIC filter is built with the two opamp sections of an NE5532. Another OP-275 buffers the output and is coupled to the output with back-to-back electrolytics bypassed with a smaller film capacitor.

What opamp changes would you suggest to replace:

a. OP-275 for the differential-to single-ended conversion (one OP-275 per channel)

b. NE5532. as a GIC filter (built with the two opamp sections of a single NE5532)

c. OP-275 - another pair buffers the output
Check the opamps thread. Carful when people just recommend opamps with no understanding of your circuit....Opamps are not lego and they are not all just drop in replacments.
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post #6 of 12
5/3/10 at 5:25pm
you could also add AD845KN and LT1363CS8 if you're running out of ideas...the latter can really do wonders.
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post #7 of 12
5/3/10 at 6:03pm
OPA627's are about $25 from a legitimate source.
From my experiences, nearly all of the opa627's on ebay are counterfeit, especially the AP and even more so, the BPs.
2x opa627 for $30 from fleabay; sorry I'll pass

The BP has slightly higher DC specs than the AP which is meaningless in the audio band.
Almost every opinion I've heard comparing AP and BP translates to "don't bother".
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post #8 of 12
5/3/10 at 6:40pm
I've never got ripped off on AD797BR/BN from ebay, but indeed many ppl claim that the 627 often end up not being genuine...especially the SM for so cheap

yes, many ppl say that higher grade only means better DC specs, but most of the times it also translates into tighter AC specs...IME, and others anyway.
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post #9 of 12
5/3/10 at 9:05pm
Quote:
Originally Posted by Nada View Post
What opamp changes would you suggest to replace:

a. OP-275 for the differential-to single-ended conversion (one OP-275 per channel)

b. NE5532. as a GIC filter (built with the two opamp sections of a single NE5532)

c. OP-275 - another pair buffers the output
a. AD8065

b. AD8022

c. AD8065

these could do the job and sound very good.

btw. how much is the voltage? Rail voltage must not exceed 12V if those op amps are used. And they must be well bypassed.
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post #10 of 12
5/3/10 at 10:08pm
the I/V op amp is doing the hardest job, taking DAC glitch energy at the sampling frequency at its input

I'd replace the NEC part 1st - from the specs its nothing special by "audiophile" op amp standards

if you're willing to use smt adapters then most of the more recent (and cheaper) opa627 wannabe replacement op amps are probably an upgrade from the NEC part as long as the noise V is competitive

I didn't see AD8610/20 mentioned above - another run at the 627 market niche by AD


Class A output bias of the I/V op amp is another optimization I don't see recommended often enough - never on the manufacturer's app cirucits - even those with 5534 I/V where its practically mandatory - you can see the feedthru zero glitch on the 'scope without the bias
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post #11 of 12
5/4/10 at 3:40pm
Quote:
Originally Posted by Nada View Post
Can anyone familiar with opamp modding give me some advice please?

Ive never modded anything and so got lost in the 179 pages of the opamp thread as to what opamp options would be best for a Denon DVD-5000 which has:

Burr-Brown PCM1704J DACs are used, two per channel; μPC4570C's do the l/V conversion; Analog Devices OP-275 op-amps do the differential-to single-ended conversion. A GIC filter is built with the two opamp sections of an NE5532. Another OP-275 buffers the output and is coupled to the output with back-to-back electrolytics bypassed with a smaller film capacitor.

What opamp changes would you suggest to replace:

a. OP-275 for the differential-to single-ended conversion (one OP-275 per channel)

b. NE5532. as a GIC filter (built with the two opamp sections of a single NE5532)

c. OP-275 - another pair buffers the output

Your unit is using generic opamps and replacing them with some decent units will improve your sound quality. The OPA627 would make good I/V's but they can be pricey. You might look at the LME49720HA for that job also. The AD 8599's, AD8620/AD8610's AD797's. Have all been used by diy'ers with great success.
Of course you would have to do your homework to ensure they are acceptable for your circuit in terms of voltage..etc
You might also consider some discrete opamps as many I have tested offer a very analog flavor making your DAC warmer and removing the "digital edge" if you have that.

Considering your current opamps I think any higher grade unit should produce great results but you will have to put in the testing to find the best set for your DAC and gear/ears.
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post #12 of 12
5/6/10 at 10:53pm
Thread Starter 

Thanks for all the great suggestions.

 

Im planning to put in some socket adaptors so I can try out some different combinations of newer affordable Opamps. Im not sure what  voltage the DVD-5000 provides on the rails (whatever they are) but the OPA275 in there now is a dual opamp that takes Supply Voltage Range  ± 4.5 to  ± 22,  so I will make sure replacements can handle that.

 

ROSCIX - I do like the analogue flavor and wonder which discrete opamps you have heard your could recommend for a warm and detailed sound?

 


Edited by Nada - 5/7/10 at 4:06am
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