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Old 2nd November 2006, 04:15 AM   #1
hifive is offline hifive  Malaysia
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Default OPA604 to OPA627..some problems

I've changed my Naim CD5 OPA 604 to OPA 627 and the improvements was good. But the only issue is in the vocal "ssss" too sharp. How should I rectify that...


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Old 2nd November 2006, 04:59 AM   #2
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Default Re: OPA604 to OPA627..some problems

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Originally posted by hifive
I've changed my Naim CD5 OPA 604 to OPA 627 and the improvements was good. But the only issue is in the vocal "ssss" too sharp. How should I rectify that...


Thanks
You can try decoupling from V+ to V- with npo 0.1 u ceramic and or decoupling to 0 rail. I personally don't like the dry character of the 627 and prefer class A bias on AD825 or heavilly dceoupled LM6171.

You should not always believe what you read about the 627


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Old 2nd November 2006, 06:33 AM   #3
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Default Re: Re: OPA604 to OPA627..some problems

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Originally posted by fmak


You can try decoupling from V+ to V- with npo 0.1 u ceramic and or decoupling to 0 rail. I personally don't like the dry character of the 627 and prefer class A bias on AD825 or heavilly dceoupled LM6171.

You should not always believe what you read about the 627



With you there, the AD825 has killer transients and powerful tight bass, yet remains smooth as silk because it runs stinking hot in a lot of Class A, wish they made small SMD heatsinks for these. they really need them.

Cheers George
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Old 2nd November 2006, 10:01 AM   #4
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Default Re: Re: Re: OPA604 to OPA627..some problems

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Originally posted by georgehifi



With you there, the AD825 has killer transients and powerful tight bass, yet remains smooth as silk because it runs stinking hot in a lot of Class A, wish they made small SMD heatsinks for these. they really need them.

Cheers George
How did you bias the AD825 to class A ??

For heatsinks, use u-shaped alloy channel available from hardware shops epoxyed to the chip. It overlaps a little but you can still solder. Brass channel is also available from model shops.

Andy
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Old 2nd November 2006, 11:44 AM   #5
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Default Re: Re: Re: Re: OPA604 to OPA627..some problems

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Originally posted by poynton


How did you bias the AD825 to class A ??

For heatsinks, use u-shaped alloy channel available from hardware shops epoxyed to the chip. It overlaps a little but you can still solder. Brass channel is also available from model shops.

Andy
Running at -15 +15 they run quite hot to the touch, (and no, they're not oscillating) to the point of wanting to cool them with a heat sink. OPA134,OPA2134 & OPA4134's SMD's, run this hot and also sound great, but the AD825's have better slam.

Cheers George
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Old 3rd November 2006, 04:50 AM   #6
banana is offline banana  Hong Kong
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Cooler Master have a small self adhesive heatsink that fits well on DIP-8 opamp.

http://www.coolermaster.com/index.ph...ipset%20Cooler
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Old 3rd November 2006, 07:05 AM   #7
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Quote:
Originally posted by banana
Cooler Master have a small self adhesive heatsink that fits well on DIP-8 opamp.

http://www.coolermaster.com/index.ph...ipset%20Cooler

Yeah, but wot's needed is one for SMD size chips, 2 banger and 4 banger.

Cheers George
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Old 3rd November 2006, 07:35 AM   #8
hifive is offline hifive  Malaysia
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Naim CD5 has 6 opamp and what I did is use 2 non polar black gate 0.47uf at pin 4 & pin 7 on each opamp. Now waiting for them to settle down before any serious listening session.
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Old 7th November 2006, 12:40 AM   #9
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I would check for any ringing (CRO)... maybe your PS bypass isn't working as it should...

0.1uF / 50V NP Black Gates are MUCH better...

Try AD826 (bipolar input) - it's good.

Boky
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Old 7th November 2006, 04:10 AM   #10
hifive is offline hifive  Malaysia
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Thanks everyone for your kind replies...

I also have OPA134, someone told me that OPA604 is better than 134. What do you think of 134 vs 627 in sound quality wise.

I'm getting 637BP next week!
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