Best method for I to V?

[fierce_freak]

I got my Buffalo DAC yesterday. I'm having a few problems with the IVY stage, but when I've had it working correctly it sounds flippin' sweet. I do wonder, though, if I can do better for an output stage. Of course, there's the zapfilter, but I imagine using some nice transformers for the I/V conversion or maybe some autoformers would be pretty tops.

Anyone have any experience on best sounding method for I/V conversion? Tubes? Opamps? Transformers? Simple resistor (and differences between resistor brands)?

[grawk]

I got my Buffalo DAC yesterday. I'm having a few problems with the IVY stage, but when I've had it working correctly it sounds flippin' sweet. I do wonder, though, if I can do better for an output stage. Of course, there's the zapfilter, but I imagine using some nice transformers for the I/V conversion or maybe some autoformers would be pretty tops.

Anyone have any experience on best sounding method for I/V conversion? Tubes? Opamps? Transformers? Simple resistor (and differences between resistor brands)?

Colin recently designed an I/V stage. I'll let you know how it sounds when I get it.

[naamanf]

What problems are you having with the IVY?

[fierce_freak]

Here's a copy/paste of an email I sent to the TPA guys:

I received the Buffalo today and saw your email, so I switched stuff around in the IVY as you suggested. I already had everything else for the buffalo setup ready, so all I had to do was drop it in and test. I'm getting some odd results.

When I first turned the DAC on, I initially thought I was only getting a signal out from one channel (the right one). I pulled out the connection between the right output and my amp and noticed I was getting a signal from the left output, but at a much lower volume. I connected the amp to the right output again and just sat there for a few minutes while thinking about possible problems, and the left output popped up to the same level as the right out of nowhere. I listened for 5 minutes and was thoroughly impressed.

I decided to turn the DAC off and back on to make sure things were OK, and I experienced the really low volume on the left output again. I reset the DAC, and now only listening for 5 minutes or so, I only get sound out of the right output, but it's now at the level the left was previously at when it was really low. I don't hear the left channel no matter how loud I turn it.

That was last night. Today I took it all apart and reflowed all the solder on the IVY. After I put it back together, it just burns up the fuse when I power on. I haven't had time to look any further than that as I had to get to work. I'll figure it out, but I'm in no rush (not like I have time to do anything, anyways ).

I'm not asking about I/V options due to those problems, though. I'm just interested to see how other stuff might compare. I'll look forward to your impressions, grawk.

[swt61]

From what I've read Jim, the IVY is a pretty nice solution.

[fierce_freak]

Oh, I don't doubt it at all. I think it will actually perform really, really well. It's just the curiosity in me wanting to see what I could realistically improve.

[luvdunhill]

Simple resistor (and differences between resistor brands)?

I'm planning on trying DIY resistors... Manganin, Copper, Silver... sky's the limit. I'll report back once I get the kids trained on winding this stuff.

My plan is to calculate the length needed to achieve a certain resistor value plus some, fold wire in half, hand drill to twist (or get blackmail material on swt61 and farm it out to him), release tension, wind on former, shorten and dial in exact value, and voila a non-inductive resistor. I'm looking at 2 x 17 meters of wire to get 2 x 39R resistor "center tapped".

yes, I'm serious.

[fierce_freak]

You know what's funny...I was thinking about doing just that last night while I was laying in bed O.o

-edit- of course, in their IVY stage they've recommended using 178R for the actual I/V resistors. might have to use a less conductive metal for resistors that big

[swt61]

(or get blackmail material on swt61 and farm it out to him)

That may prove tough, as I'm usually the first to draw attention to my freaky sexual practices and immoral behavior.

[grawk]

if you're enough of a freak, you HAVE to advertise. don't ask why i know that

That may prove tough, as I'm usually the first to draw attention to my freaky sexual practices and immoral behavior.

[Looser101]

That may prove tough, as I'm usually the first to draw attention to my freaky sexual practices and immoral behavior.

Vids will be fine too.

On topic: How about something like the RAKK Dac passive output stage?

[fierce_freak]

Renato, that's more along the lines of what I was thinking. My first thought was more or less that exact output stage, followed by thoughts of premium resistors (even roll your own) then things like the zapfilter.

[Pars]

I personally prefer the no feedback discrete current conveyor type I/V stage (ala Jocko and variants... rbroer, cetoole's is one as well and looks good). To be honest, I haven't tried passive mainly because it sucks, at least with a TDA1541a which doesn't have the current to really drive a resistor. Iout on a DAC really wants to see a dead short, and any resistor, particularly one large enough to give you the output voltage needed isn't going to be close to that.

I have also not tried transformers, as they are quite expensive. I think you can build a better discrete stage than a zapfilter as well. I have done quite a bit of opamp rolling, and other than the THS4031/4032 which I never got around to trying, I would not consider going back to them... discrete just kicks them too badly.

Is the IVY a discrete stage or is this the one using a THS4031? Or another really high speed chip?

[fierce_freak]

THS4131.

I'll have to take a look into those you mention, Pars. Do you have any links?

[Pars]

which ones?

[fierce_freak]

For any of the discrete current conveyor types or any other stage you believe may be better than zapfilter.

[naamanf]

I am also interested in a discrete I/V stage for the Buffalo. I have a IVY and a Zapfilter but would like a circuit I could lay down on my own board.

[fierce_freak]

Where do you get your boards made, naamanf?

[Pars]

Jocko's (incomplete... for ideas only, but will work)

http://www.diyaudio.com/forums/showthread.php?s=&threadid=6121&highlight=

interesting thread... Nicke is one who supposedly figured Jocko's stage out, and has a stage posted on diyaudio IIRC:

http://www.diyhifi.org/forums/viewtopic.php?p=3712&highlight=simple#3712

rbroer's less simple TDA1541a stage (this is the one I am using minus the PSU emitter follower stuff)

http://www.diyaudio.com/forums/showthread.php?s=&threadid=22542

rbroer also has a simple 1541a stage, as well as one or two 1543/1545 stages, one of which is what is used for the monica dac. Search diyaudio if you are interested in these. The one above is probably the best model for adapting to other DACs.

ANd another thread, some on the rbroer as well as others:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=54608&highlight=

[naamanf]

I have used Advanced Circuits a couple times here in Colorado. I also have some boards I ordered from Futurlec waiting back in Iraq. They seem to be the way to go if you want a lot of little boards made up and are not in a hurry.

[Pars]

I've used Olimex once for some boards and they were fine as well. Not as good of quality as Imagineering, etc., but much better than I expected... and much cheaper.

[Looser101]

Jocko's (incomplete... for ideas only, but will work)

http://www.diyaudio.com/forums/showthread.php?s=&threadid=6121&highlight=

interesting thread... Nicke is one who supposedly figured Jocko's stage out, and has a stage posted on diyaudio IIRC:

http://www.diyhifi.org/forums/viewtopic.php?p=3712&highlight=simple#3712

rbroer's less simple TDA1541a stage (this is the one I am using minus the PSU emitter follower stuff)

http://www.diyaudio.com/forums/showthread.php?s=&threadid=22542

rbroer also has a simple 1541a stage, as well as one or two 1543/1545 stages, one of which is what is used for the monica dac. Search diyaudio if you are interested in these. The one above is probably the best model for adapting to other DACs.

ANd another thread, some on the rbroer as well as others:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=54608&highlight=

What was your opinion of this one?

http://www.head-fi.org/forums/f6/neverending-quest-balanced-i-v-stage-326087/

[Pars]

I've been playing around with an earlier version of Christian's (Cauthemoc on hf) designs. This one is a real current conveyor (ala Hawksford) design. It is somewhat more complicated (more parts), but should sound good. I would like to at least breadboard this one up some time. This one has extremely low input impedance (0.3 ohm) according to Christian... I can't calculate that and don't run simulations (which is how he calculated it IIRC). He is an engineering student in Switzerland, and seems to know what he is doing...

[fierce_freak]

Thanks for the further info guys. I just say that Jay now has a cd player with transformers on the output and likes it pretty well, but I'd love to hear any impressions on comparisons anyone else has done between different I/V solutions like discrete vs. opamp vs. transformer/passive.

On a side note: the Buffalo DAC, even with no I/V stage (it can operate as voltage out with decreased specs) sounds really incredible. Really, really nice. Did I mention that the sound is killer?

[fierce_freak]

Colin recently designed an I/V stage. I'll let you know how it sounds when I get it.

Grawk, did you ever receive this? Just curious

ot: Have you ever compared your balanced m3 to a balanced b22? thoughts?