[boodi]

HI .
I'm thinking about the upgrade on my s100mkII .

I'd like to know the main sound / technical differences among the three so that I'm able to do the best good choice.

Thanks a lot .

 

[flecom]

the 627's are unity gain stable and the 637's dont work well with a gain less than 10...

the BP vs AP, i dont remember which one was which but the more expensive ones have better DC charactaristics... so in theory there should be no difference in audio applications...

i like the sound of the 637's a lot more than the 627's IMO, but YMMV

 

[boodi]

If I'd have to get 637 in my shanling s100mkII for modding purpose , how could i know if it's possible to do ?

 

[JohnFerrier]

Datasheet:
http://focus.ti.com/lit/ds/symlink/opa627.pdf



JF

 

[thrice]

Tangent has a great article regarding these opamps here. He discussed the OPA627s and the 637s.

You could also check out the datasheets for them. Just search for OPA627 on digikey's site and follow the links for the datasheet, or go to Texas Instrument's site and look them up there. If I remember correctly the 627s and 637s are on the same datasheet.

 

[flecom]

Quote:

Originally Posted by boodi If I'd have to get 637 in my shanling s100mkII for modding purpose , how could i know if it's possible to do ?

its probably running the opamps at unity or very low gain so i would go for 627's if i were you to be safe

 

[TrevorNetwork]

I have compared the 627ap and 637bp and it seemed I preferred the sound of the 637bp. I believe the 627ap seemed slightly harsh in the treble, and the midrange was not as smooth and detailed as the 637bp. This was not double blind though, and could be the placebo effect.

 

[boodi]

Quote:

Originally Posted by flecom its probably running the opamps at unity or very low gain so i would go for 627's if i were you to be safe

I'd go for the 637 if i could get it in the circuit safely and have it fully functional .

anyway..the shanling s100 mkII mounts four opa604ap in line , and 1 opa2604ap ( detached from the four 604 )
Do I have to replace the 5 chips getting off the 604s and getting in the 627bp or am i supposed to pair two 627 so to have 8x627 in place of 4x604 ?
.. moreover asking just for curiosity ( I'm not doing it because i understand it's very unlikely the s100mkII -as a source- have a gain of 5 on circuit points where are opa placed in) what if i try the 637 in , is it dangerous to have a not stable opa637 in a circuit or not

thanks again for answering for clearing my dubts.

I wonder also how the 627au differs sonically speaking from both the ap and the bp

 

[JJ3810]

I'm in the minority here & against all data and reason but I have both the 627bp and the 637 bp and I prefer the 627 bp using Grado 225s. The treble seems smoother and there's plenty of detail. My PPA is set for a gain of 7.8 so I wasn't sure if the 637s would be stable at that low of a setting anyway.

 

[Earwax]

Quote:

Originally Posted by boodi I'd go for the 637 if i could get it in the circuit safely and have it fully functional . anyway..the shanling s100 mkII mounts four opa604ap in line , and 1 opa2604ap ( detached from the four 604 ) Do I have to replace the 5 chips getting off the 604s and getting in the 627bp or am i supposed to pair two 627 so to have 8x627 in place of 4x604 ? .. moreover asking just for curiosity ( I'm not doing it because i understand it's very unlikely the s100mkII -as a source- have a gain of 5 on circuit points where are opa placed in) what if i try the 637 in , is it dangerous to have a not stable opa637 in a circuit or not thanks again for answering for clearing my dubts. I wonder also how the 627au differs sonically speaking from both the ap and the bp

The opa604 is a single channel chip and can be replaced by the opa627, the opa2604 is a dual channel chip and would need to be replaced by 2 of the 627s in an adapter or some other dual channel chip. the 'u' chip is a smaller surface mount part, the 'p' chips are the 8-pin ones that mount in a socket.

According to Tangent's site there's no audible difference between the a and b parts, I've never had both available at the same time to compare them myself.

 

[doobooloo]

Although there is no audible difference between the a and b parts, I always use the b parts for my PPAs with bass boost because it will boost DC offset significantly and the insignificant difference without BB will become more significant.

 

[guzzler]

To summarise doo, the only difference between A/B versions is the DC accuracy. Ie, the B version will have a lower offset than the A.

g

 

[JohnFerrier]

As I learned from PPL, DC offset is distortion at 0hz...


JF

 

[boodi]

so , as i probably understand , the ap will likely sound equal to the bp version in a let's call it "standard" cd player circuit
?am i right

 

[qwerty870]

Quote:

Originally Posted by boodi so , as i probably understand , the ap will likely sound equal to the bp version in a let's call it "standard" cd player circuit ?am i right

Yes. (Well that has been my experience.)