[Andrea]

I don't know, perhaps a strange moment, or maybe that I used an unfamiliar record...


Yesterday evening I had the impression that the Xtra with LM4562 was more transparent in that it had more "breath" in the mids, but now I think that the Xenos with LM4562 and AD9631 just sounds more coherent and full bodied. The Xtra had a bouncy bass that was enticing at first, but the Xenos's bass is truer, more realistic. What's for sure is that I've moved the Xenos to the HD485 setup, and the 'phones are sounding fantastic, better than they ever did...

And now that the Xenos isn't on top of the Pioneer integrated (which I must keep powered since I'm using its rec output) anymore, it looks like I overestimated the warming up, even.

 

[picklgreen]

You can get them directly from national semiconductors.

 

[Andrea]

These AD9631's are super, indeed. Lot of resolution and extension, without any harshness in the treble, lots of grip on the bass (wow!), and that lovely full bodied midrange that I just can't live without. These are for me

LM4562 and AD9631 could really be the ultimate setup for this amp.

 

[pddjsteve]

Quote:

Originally Posted by Andrea /img/forum/go_quote.gif These AD9631's are super, indeed. Lot of resolution and extension, without any harshness in the treble, lots of grip on the bass (wow!), and that lovely full bodied midrange that I just can't live without. These are for me LM4562 and AD9631 could really be the ultimate setup for this amp.

My LM4562 arrived on friday and I popped it in my Pimeta. Sounds good! I think I am going to pick up a 3rd AD9631 and see how they fare in the buffer positions.

 

[Andrea]

Quote:

Originally Posted by pddjsteve /img/forum/go_quote.gif My LM4562 arrived on friday and I popped it in my Pimeta. Sounds good! I think I am going to pick up a 3rd AD9631 and see how they fare in the buffer positions.

That'd be interesting. Note that in my Xenos here they're configured as unity gain followers, with a 1K feedback resistor with a capacitor of unknown value in parallel. Plus there are 6.8 ohm series output resistors, outside the feedback loop. This should optimise the transient response of the chip, and perhaps guarantee its stability driving reactive loads, as far as I understand. But it's not necessarily true that leaving out the R's and the C and just connecting the output to the inverting input would sound worse(?).

 

[Andrea]

Oh and the Xenos also has two dedicated .1uF (or so) bypass capacitors on the power lines of the buffers.

 

[pddjsteve]

Quote:

Originally Posted by Andrea /img/forum/go_quote.gif That'd be interesting. Note that in my Xenos here they're configured as unity gain followers, with a 1K feedback resistor with a capacitor of unknown value in parallel. Plus there are 6.8 ohm series output resistors, outside the feedback loop. This should optimise the transient response of the chip, and perhaps guarantee its stability driving reactive loads, as far as I understand. But it's not necessarily true that leaving out the R's and the C and just connecting the output to the inverting input would sound worse(?).

Well, I know the AD9631 works well in the unity gain ground channel position of the pimeta, but that was followed by the buffer and not directly by the load. I modified a couple of DIP sockets to connect pin 2 and 5 to make it unity gain (just like if I was going to use the opa551 instead of buf634), not sure if I'm going to need to swap the piece of resistor lead I soldered in with a small cap or not. The ground opamp has a 10pf cap between 2 and 5 fro bandwidth limiting. I do have a resistor in series outside the feedback loop, 75 ohms for a built-in ER4P->ER4S adapter.

If it doesn't end up working, I might just toss them on a single-to-dual browndog and see how I like having AD9631 in all 3 channels in the opamp position. All I've really done is modify a couple of sockets so far, so no GREAT loss if it doens't work. If it does, then whee.

Quote:

Originally Posted by Andrea /img/forum/go_quote.gif Oh and the Xenos also has two dedicated .1uF (or so) bypass capacitors on the power lines of the buffers.

Hmm. This might be the biggest problem I come up against. I'd have to mess with the board and not the sockets.

 

[Andrea]

It's a little risky to use the AD9631 for the preamplifier job in the L-R channels of the Pimeta, you'd surely get lots of DC offset unfortunately.

I wouldn't know if the AD9631 actually performs better than the BUF634 buffers in high bandwidth. Certainly it beat all the other op-amps I tried for output drivers in the Xenos amp!

 

[pddjsteve]

Quote:

Originally Posted by Andrea /img/forum/go_quote.gif It's a little risky to use the AD9631 for the preamplifier job in the L-R channels of the Pimeta, you'd surely get lots of DC offset unfortunately. I wouldn't know if the AD9631 actually performs better than the BUF634 buffers in high bandwidth. Certainly it beat all the other op-amps I tried for output drivers in the Xenos amp!

Yeah, I am not too sure about that either. I played with tangent's offset calculator after reading the cranky opamps article he has and got the AD8058 offset down really low, but I think I was having trouble getting the AD9631 to a decent value. Then again, the offset in practice with the 8058 was even lower than calculated, so I might give it a shot and just measure first, then test with cheap phones. If it turns out to be too high, I won't bother.

 

[Andrea]

And, out of curiosity, how did you like the AD8058?

 

[d-cee]

i tried ordering these through the samples program from national's website and they said they will review it within 24 hours and let me know

it's been more than 24 hours... how long did everyone else have to wait for theirs?

 

[pddjsteve]

Quote:

Originally Posted by Andrea /img/forum/go_quote.gif And, out of curiosity, how did you like the AD8058?

I had to toss the ad8058 back in to give it another listen. I can't decide whether I like the ad8058 or the lm4562 better. The immediate difference I could notice was the 8058 has a bit more bass. The detail seems to be about the same. I've noticed a bit more turn-0n thump with the 8058. Offset was between 10-12 mV at my normal listening levels, 15-17 at closer to full volume (I played with the multiloop resistors and am using lmh6321 in the pimeta buffer position). I don't know if I can get into more without further listening.

And yeah, blindly tossing the 9631 in the buffer position just resulted in warm buffers and a whole lot of DC offset.

Just for kicks, I left the same resistor values in as the 8058, and tossed the 9631 on a 2xsingle->dual browndog... cool to the touch, DC offset was less than 10mV, so I went for it - sounds GREAT at first listen.

Don't take my words as gospel, though - for all I know it's a fluke. I really don't COMPLETELY know what I'm doing

 

[izquierdaste]

FYI lme49710 is now available at digikey. It is the single version of this opamp. Other forums seem to be pretty excited about the lm4562, so it could be interesting for resolution lovers.

 

[ericj]

Quote:

Originally Posted by d-cee /img/forum/go_quote.gif i tried ordering these through the samples program from national's website and they said they will review it within 24 hours and let me know it's been more than 24 hours... how long did everyone else have to wait for theirs?

I paid $12 for my 'free' samples and was approved in seconds. got my samples a couple days ago, haven't tried them.

You might try again, and be prepared to shell out $12 for three of 'em - which is a good deal. Usually I'm against 'abusing' the free sample system, but you can't actually buy these anywhere yet.

 

[izquierdaste]

Both the single (lme49710) and dual (lm4562) are available at digikey for about $5 each. (Perhaps my last 2 posts make me sound like a digikey shill, but I'm not.) I just want to hear people's opinions on these.