[Percival]

Well the Ivy III is the output stage I use, I don't think you can connect direct to the Buffalo PCB. The Ivy III certainly does work well as a HP amp, no need to add more stuff to the chain than necessary IMHO. The JT is an analogue attenuator and they're not on sale at the moment anyway. I would say go for the Volumite.
 
Quote:

 
That's great info, just what I was after thanks! Just how good is the Buffalo as a HP amp I wonder? If it is anywhere near as good a HP amp as it is a DAC then it must be an absolute bargain!
 
So it is just the volumite I need, and not the Joshua Tree as well? Sorry for the newbie questions, haven't ever used an attenuator, and as already stated I haven't properly begun to read up on the Buffalo yet. 
 
Cheers in advance
 

 

[Percival]

The Ivy III can run both with no modifications. As for balanced outs just for 'phones, that's just what I do. I bypassed the output resistors for some additional damping. It's all in the Ivy III manual anyway.
 
Enjoy.
Quote:

 
Anyone know if there are any considerations when using the Buffalo/IVY as a pre amp for a headphone amp, and a speaker power amp? Both these will be SE via RCA. The only time I will be using it balanced then is as we've just talked about to drive 'phones straight from it. By considerations, I mean things like any particular resistors or other components that need to be left off or anything like that?

 

[maruzen]

very interested in this dac from what i've read and reviewed...
 
sadly no one in my locale has this for audition. someone has to make the jump i guess...
 
that was one long backread though... and i'm still not done...
 
subscribed 

 

[chum_2000_uk]

Just a quick question for those who have built the B-II with IVY3... I am in the middle of building the IVY 3 and I want to use this to power 'phones in balanced mode and a power amp for my speakers. In the manual it says:
 
The IVY-III can easily drive most headphones (even down to 16Ω) when used as a balanced headphone driver along
with the Volumite or similar digital volume control. The SE outputs are not capable of as much power, but can still be
used for most headphones. It is recommended that if you wish to drive headphones you use jumpers for R25/R26
and/or R27-R30, which will allow for better damping factor. The OPA1632 can drive up to 150mA, giving you plenty
of power for almost any headphone listening situation. It is recommended when driving power amps to always use the
output resistors, especially with very capacitive cables.
 
So... for my setup where I want to be able to drive headphones and use the B-2 with a power amp, do I jumper R25-R30 or do I include them all?
 
Cheers guys

 

[FallenAngel]

Well, it's unlikely that you'll drive both at the same time, so you'll have a switch... just wire inline resistors on the rear outputs and leave them out for headphone output.

 

[jcx]

 
Quote:

Just a quick question for those who have built the B-II with IVY3... I am in the middle of building the IVY 3 and I want to use this to power 'phones in balanced mode and a power amp for my speakers. In the manual it says:
 
The IVY-III can easily drive most headphones (even down to 16Ω) when used as a balanced headphone driver along
with the Volumite or similar digital volume control. The SE outputs are not capable of as much power, but can still be
used for most headphones. It is recommended that if you wish to drive headphones you use jumpers for R25/R26
and/or R27-R30, which will allow for better damping factor. The OPA1632 can drive up to 150mA, giving you plenty
of power for almost any headphone listening situation. It is recommended when driving power amps to always use the
output resistors, especially with very capacitive cables.
 
So... for my setup where I want to be able to drive headphones and use the B-2 with a power amp, do I jumper R25-R30 or do I include them all?
 
Cheers guys

now I see where the misinformation is coming from - looks like Twisted Pear misread the OPA1632 datasheet
 
150 mA is not the op amp's current drive ability - it is a value beyond which the chip may be damaged

for usable output current a better place to look is the min short circuit current spec: +50/-60 mA - and that # is for no output V
 
then look at the output V vs load R plot (fig 9) to see that [size=12pt]~50-60 mA also [/size]seems to be the working current limit of the (hopefully "typical") device the plot was made with
 
gain resistors should be changed to get Vswing to match the headphone drive requirements (but the  fig 9 graph's peak current is going to be a limit, some higher Z headphones or higher sensitivity low Z iem could be driven "adequately")
 
 
the 22 Ohm R isolate the op amp output from cable Cload which can cause instability - reducing to 5-10 Ohms or replacing with properly (over) sized ferrite bead core inductors would be my recommendation for direct headphone output because headphone cables have capacitance too
 
 
overall a close reading of the OPA1632 datasheet doesn't make it look particularly good as a headphone amp - the output current ability makes it not much better than a "balanced" CMOY - I certainly wouldn't hang my K701 or any orthodynamic headphone from the OPA1632 output

 

[chum_2000_uk]

 
Quote:

 

now I see where the misinformation is coming from - looks like Twisted Pear misread the OPA1632 datasheet
 
150 mA is not the op amp's current drive ability - it is a value beyond which the chip may be damaged

for usable output current a better place to look is the min short circuit current spec: +50/-60 mA - and that # is for no output V

Are you sure you are correct? I don't personally know enough about any of this to pass comment, most of what you have said goes straight over my head tbh. I'm therefore not arguing with you here, but Brian and Russ seem pretty damn switched on regarding their product. This seems like it would be a fairly considerable oversight on their part, and mine and other people's results when driving headphones from the IVY-III would indicate that it actually does it well. I'm pretty sure that the results are better than a "Balanced" CMOY. Not that I've heard one

 

[jcx]

the apparent current limit from the data sheet is ~1.5-2x better than many op amps that have been used in CMOYs but not really high enough for low sensitivity, low impedance cans if you want to reach the higher dynamic peak SPL of some real world acoustic music performances
 
I don't have the chips to measure but I have read datasheets and specified op amps for precision industrial/scientific instrumentation for several decades now
 
the OPA1632 appears from the datasheet to best match moderate sensitivity, higher impedance headphone's drive requirements; some high sensitivity, low impedance cans could also be driven adequately

 

[chum_2000_uk]

So you are saying it would likely drive HD650's better than AKG K702's?
 
Quote:

the apparent current limit from the data sheet is ~1.5-2x better than many op amps that have been used in CMOYs but not really high enough for low sensitivity, low impedance cans if you want to reach the higher dynamic peak SPL of some real world acoustic music performances
 
I don't have the chips to measure but I have read datasheets and specified op amps for precision industrial/scientific instrumentation for several decades now
 
the OPA1632 appears from the datasheet to best match moderate sensitivity, higher impedance headphone's drive requirements; some high sensitivity, low impedance cans could also be driven adequately

 

[jcx]

you should understand that I'm really talking about the extreme margins of performance - trying to recreate real world SPL of Orchestral or Big Band Jazz, sitting close to hard hit snare drums, cymbals
 
at "polite" or "background" listening levels that are safe for all day, every day exposure or dynamic range compressed pop music the extra 12 dB headroom you would have with the OPA1632 driving HD6xx vs K70x would never come into play

 

[beerguy0]

Quote:

 

now I see where the misinformation is coming from - looks like Twisted Pear misread the OPA1632 datasheet
 
150 mA is not the op amp's current drive ability - it is a value beyond which the chip may be damaged

for usable output current a better place to look is the min short circuit current spec: +50/-60 mA - and that # is for no output V
 
then look at the output V vs load R plot (fig 9) to see that [size=12pt]~50-60 mA also [/size]seems to be the working current limit of the (hopefully "typical") device the plot was made with
 
gain resistors should be changed to get Vswing to match the headphone drive requirements (but the  fig 9 graph's peak current is going to be a limit, some higher Z headphones or higher sensitivity low Z iem could be driven "adequately")
 
 
the 22 Ohm R isolate the op amp output from cable Cload which can cause instability - reducing to 5-10 Ohms or replacing with properly (over) sized ferrite bead core inductors would be my recommendation for direct headphone output because headphone cables have capacitance too
 
 
overall a close reading of the OPA1632 datasheet doesn't make it look particularly good as a headphone amp - the output current ability makes it not much better than a "balanced" CMOY - I certainly wouldn't hang my K701 or any orthodynamic headphone from the OPA1632 output

I'm kind of surprised to see them make a claim of 150mA of current drive. I read the datasheet, and just as jcx pointed out, 150mA is the chips "don't do this to me" limit. The 50-60mA spec is the minimum current into a short circuit (0V output). The typical value is 85mA, and you could reasonably expect the average part to be pretty close to that. I usually interpret the minimum values as the guaranteed performance over temperature, voltage, etc.

 

[Percival]

Regarding the OP1632, you may wish to read what Russ has to say on the subject.
 
http://www.diyaudio.com/forums/twisted-pear/160782-buffalo-ii-75.html#post2288682

 

[chum_2000_uk]

Great info - thanks Percival
 
Quote:

Regarding the OP1632, you may wish to read what Russ has to say on the subject.
 
http://www.diyaudio.com/forums/twisted-pear/160782-buffalo-ii-75.html#post2288682

 

[maruzen]

enjoying this DAC immensely with my entry level monitors, the Samson MediaOne 4a. recently hooked them with the stax lambda pro and the srm-1/mk-2 and even if I love the sound of the speakers better, there's no denying how good this DAC just is. my music just sounds so different, like more alive it seems. even the stuff I don't listen to have become enjoyable to listen to. amazing piece of technology. thanks to you guys over at Twsited Pear Audio! had a local DIY guru build it and he has done a masterful job too.

 

[alexk400]

Can someone post me their DAC installation images. Buffallo III
I want the PSU, DAC, USB INPUT boards.
 
It seems like many buying and building. Any images i can see?
 
thanks.
alexk