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Old 5th September 2007, 03:02 PM   #1
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Default NAIM CD5 - opamps

Hi

Has anyone had any joy changing the opamps in one of these players. I changed the final 2 from OPA604 to AD8610 (soic) and there were nice gains. But what about the other 4. Is it worth the hassle and if so what would you go for.
I was thinking of the LM4562 equiv in single form (LM49710NA).

Thanks
Brent
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Old 5th September 2007, 06:42 PM   #2
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The 49710 sounds awful here. Dull, dull, dull. I don't think it works very well in filters anyway, but I can specifically tell you it doesn't work in Naim's 3rd order bessel filter.

Fast FET input types do however. Take a good look at datasheets for output impedance - you want ths to be low, open loop (its often not given in datasheets though)for best effect in sallen-key filters.
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Old 5th September 2007, 07:12 PM   #3
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Thanks Martin.

I have them on sample order and thought they maybe ok.

I tried the 627 this afternoon in place of the AD8610 and think these were much more suited. Better bass and rhythem.

I'll check through the data sheets of what I have or could order.
What do you have in your 3.5?

Brent
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Old 5th September 2007, 07:35 PM   #4
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I had 627s. in all three positions. The output pair made the biggest difference by far. If using faster opamps, do add 27-47R in series at the final pair's output to decouple the interconnect capacitance.

AD8065s might be worth a try - haven't used them myself.

The 3.5 and 5 are virtually identical circuits BTW, so you'll find many of the mods common. Specifically, if you haven't already, do #7 (here: http://www.acoustica.org.uk/t/naim/35mods2.html) - it will make a much bigger difference than dicking with these extra four opamps.
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Old 5th September 2007, 07:50 PM   #5
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I noticed the pcb said 3-5 on it. It did make me wonder.

So far I have fitted a clock, bypassed the inverter chip (i don't like these). Fitted low noise regs on the dac and opamps today.
I changed the cap on the dac for the ripple current but need to experiment more here.

The difference is amazing, much more open and detailed, also the listenability is much better.

I'll take a look on the site see what other tweeks there are.

Thanks

Brent
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Old 6th September 2007, 07:34 AM   #6
lucpes is offline lucpes  Romania
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All opamps sound better with additional decoupling on-situ (right on top of the opamp). I use Rubycon ZA 220uf/35V soldered directly on the rail legs with great results (sense of power reserve, openness and so on).
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Old 6th September 2007, 07:55 AM   #7
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If you want to get really fancy for the outputs try the Walt Jung composite op-amp, better results than you could ever realistically obtain from a single op-amp, excellent current drive and superlative ease of sonics. If used in the I/v stage I have found the OPA627 to be pretty bad sounding when compared to the opa604, Ad823 is my favorite in this role, however it is a dual op-amp. The Opa627 has its own sort of rounded sonic flavour, best when biased into class-a with an active CCS. not a resistor and the AD744/ad811 combo is very neutral, some may call it clinical, mechanical so it really becomes the best of both worlds in some ways.


Colin
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Old 6th September 2007, 11:46 AM   #8
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Thanks guys

Martin I did the Analogue bias decoupling hack and it worked very well indeed, it improved pretty much everything but most noticably was the stereo seperation. The layout was different on this player but was easy to sort.

Thanks

Brent
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Old 6th September 2007, 12:50 PM   #9
oam is offline oam  Europe
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Quote:
Originally posted by lucpes
All opamps sound better with additional decoupling on-situ (right on top of the opamp). I use Rubycon ZA 220uf/35V soldered directly on the rail legs with great results (sense of power reserve, openness and so on).
More details please Would I be mad to try this on my Sony CD-player which just had new op-amps? And how could one determine the suitable cap? Thanks!
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Old 6th September 2007, 01:19 PM   #10
KP11520 is offline KP11520  United States
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Hi Colin,

Quote:
Originally posted by vynuhl.addict
If you want to get really fancy for the outputs try the Walt Jung composite op-amp, better results than you could ever realistically obtain from a single op-amp, excellent current drive and superlative ease of sonics. If used in the I/v stage I have found the OPA627 to be pretty bad sounding when compared to the opa604, Ad823 is my favorite in this role, however it is a dual op-amp. The Opa627 has its own sort of rounded sonic flavour, best when biased into class-a with an active CCS. not a resistor and the AD744/ad811 combo is very neutral, some may call it clinical, mechanical so it really becomes the best of both worlds in some ways.

Is there any place you can point us to, to find the best way to make an active CCS and employ it? Also, when you biased the OPA627, how many mA did the CCS bias the 627 for best results or did that not matter with an active CCS?

Thanks!

Regards//Keith
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