Beginner PPA builder's questions. (What opamp, etc.)

[steinba]

While I wait for my PCBs to arrive, I could use to get a few things straight.

*Choosing the right opamp: I'm not sure whether OPA627 or AD8610 will be best for me. I'm leaning towards OPA627 because of Tangent's descriptions of it's sound, the fact that I can get it in a DIP-8 configuration and a little because I've heard that it has a slightly exxagerated midrange that I think will complement my Senn 650's slightly withdrawn midrange. I also understand from what I'm reading that it might be a bit more analytical than the AD8610, and that might be good, to counteract the Sennheisers' warm sound/boomy bass and reserved treble a bit. Also: The AD8610's SOIC configuration which requires a "Brown dog" adapter into a DIP-8 socket must make the signal paths sligthly longer than an OPA627 into a DIP-8 socket, right? (Aren't there SO-8 sockets that can replace the DIP-8 socket?) ...But in the end, I guess the differences are really only nuances. Am I right?

*Adjusting the gain to compensate for a modified linkwitz crossfeed filter: I assume this is a non-problem, but still: I read that when using the crossfeed, the gain should be 2-3 times higher than when not. (And is a gain of 11x sufficient for driving the 300 Ohm 650s?). Are the opamps fine with a 22-33x gain?

*Rail capacitance: As I've said in another thread, I've been told from trusted sources that I really should stay between 1000 and 2000 uF. Why is this? Why wouldn't 4000uF be better if the quality of the caps stayed the same?

Any tips and opinions will be greatly appreciated.

I'm looking forward to getting started on this. (But I better hurry up and do my "training projects" first. I've never set foot in a soldering iron before)

TIA!

 

[Jazper]

I heard a ppa with the 627s in it, found it quite boring to listen to.

I say try the AD8610 or maybe the AD8065.

 

[bg4533]

A gain of 11 with the crossfeed should be fine. I think a gain of 3-4 is fine for the HD650 without the crossfeed.

As for capacitors...There are a few different things going on here. When using large amounts of rail caps the in rush current these draw can blow up regulators on PSUs like the steps and tread. Some people have reported that sound increases up to a certain capacitance and then tends to get a bit lazy sounding. The best thing you can do is experiment and find out. Higher quality caps tend to be physically larger. On the PPA you might be able to fit 220uF Blackgates in each spot or 1500uF Panasonic FCs. You will need to decide for yourself which you like best.

 

[steinba]

Thanks.

 

[steinba]

Doesn't anyone have any opinions on which of the two opamps would sound best with the Senn 650s?

Are there others who also think that the 627 is boring sounding compared to the 8610?

 

[Kippei]

Quote:

Originally Posted by steinba Doesn't anyone have any opinions on which of the two opamps would sound best with the Senn 650s? Are there others who also think that the 627 is boring sounding compared to the 8610?

OPA627 works fine with MS-1 but not AD8610. For 650s, AD8610 are the ones to go for.

 

[steinba]

Quote:

Originally Posted by Kippei OPA627 works fine with MS-1 but not AD8610. For 650s, AD8610 are the ones to go for.

Thanks. Care to elaborate? What aspects of the sound are "better" with 8610 than with 627 through HD650s?

 

[Kippei]

Quote:

Originally Posted by steinba Thanks. Care to elaborate? What aspects of the sound are "better" with 8610 than with 627 through HD650s?

MS-1 are bright phoneys. AD8610 are bright opamps. Bright + bright = extra bright = painful ears. From my view, the AD8610 compensate the dark nature of 650s, making more of a balance.

 

[chesebert]

to give you some idea of the effect of 8610 vs 627..not going into warm/cold/bright..all those technical.non descriptive words...LOL

8610 simply gives me more ambience or cues of live recording than 627 when using HD600. Each instrument seem to seperate better and you are placed in a live performance, the bass is tight, the high is just right and each instrument gives out enough vibration to sound real. Nevertheless, I use 627 since I also use HF1 which sounds beautiful with 627.

 

[MN Ham Phones]

Quote:

Originally Posted by steinba (But I better hurry up and do my "training projects" first. I've never set foot in a soldering iron before) TIA!

This part of your training won't take long.
You will learn *very* quickly not to get your feet near the soldering iron...especially if they are bare feet.

 

[steinba]

I'm no closer to choosing than before. I've read Tangent's comments on the AD8610 and the OPA627, and searched the forums both here and on headwize for "opa627 ad8610", and it seems like there's no canonical answer (Not that I'd expected one). It seems that I'll just have to buy both chips and listen to them for myself.

...But of course: More tips/hints/experiences will be appreciated. Maybethere's someone aound with both a PPA and 650s that can share some more insights?

....Allright! I'll try to stop nagging now.