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Russ White  
#1 Posted : Friday, June 27, 2008 7:43:46 PM(UTC)
Russ White

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ocean delivers
mystically, impassive cod
ponders, dumbfounded




OK, just kidding there.. :)

From time to time I like to shake it up and try something unconventional, at least for me.... Well this is one of those times.

As some of you know I have been working very hard on a discrete fully symmetrical current to voltage converter (I/V stage) for our DAC lineup.

Well this is not that circuit (don't worry it will still come), well not exactly anyway. OK you say, what is it?

Well this is a balanced I/V stage also... but with NO global feedback. It is not a discrete op amp at all.

It is basically a cascode of the DAC current with a CFP (Complimentary Feedback Pair) doing the cascoding and a constant current source. Seems incredibly simple right? Well it is. :)

It has a very desirable trait of being basically immune to the slewing effects that many op amps suffer when used as I/V stages. It also is inherently stable and very easy to configure for filtering the output signal. It does require some adjustments so you will need to read the manual. But it should not be very difficult to get up and running

It has a very low input impedance (less than 200-mOhm to 1mhz) and very low THD. I have tested the circuit but not measured it yet so I don't have any hard numbers. What I can say is it sounds great with the buffalo. :) The simulations show a THD of .0000124% at 20khz 10K load. You are not going to be able to drive headphones or anything low impedance like that with it. For that you will want to add a buffer or amplifier.

The project is called "Haiku" which is actually a great name since there are 3 basic transistor components (one being a parallel pair). As well as lots of other sets of three in the circuit. Brian came up with the name, Which is good because I am sure it's better than one I would have chosen. ;)

The boards are 3.3" x 2" to be the same size as Buffalo and COD. Each board has two channels for balanced operation. So for stereo balanced operation you will need two boards.

Yes, it can be configured for virtually any current output DAC. :)

The supply requirements are +15V and -5V(yes minus five). LCBPS will work just fine.

Well, here is the PCB design, and it will be available soon - probably with the next board order in a couple weeks.

UserPostedImage


Cheers!
Russ

Edited by user Saturday, June 28, 2008 5:11:23 AM(UTC)  | Reason: Not specified
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Brian Donegan  
#2 Posted : Friday, June 27, 2008 9:05:25 PM(UTC)
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Buffalo and COD
current to voltage needed...
Haiku I/V stage

Edited by user Friday, June 27, 2008 9:06:07 PM(UTC)  | Reason: Not specified
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MrMajestic  
#3 Posted : Sunday, June 29, 2008 3:04:42 PM(UTC)
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And I thought I had my future Buffalo configuration all planned. Then you go and release more stuff. My wallet salutes you :)

The Haiku looks really interesting, nice work.
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devodave  
#4 Posted : Sunday, June 29, 2008 3:53:46 PM(UTC)
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Just placed a pre-order for a Buffalo-Ivy combo, but would a Haiku make more sense for my Gainclone (BrianGT) project? A Squeezebox will be the only input.

Devodave
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AudioBear  
#5 Posted : Monday, June 30, 2008 12:01:06 AM(UTC)
AudioBear

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1. I'm in the same boat as devodave (great name) and was wondering where the Haiku fits into the Buffalo -> Ivy/Haiku/Discrete stages in terms of sound quality.

2. Also as I'm pretty much single ended kit, would I only require one board and which would be the best option given 3 below.

3. I also guess going into a TVC would be fine?

So many questions, but I may as well ask them for everyone ;-)

As ever keep up the enormous amount of good work you do, if you ever need a helping hand let me know.

Russ
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Beefy  
#6 Posted : Monday, June 30, 2008 3:51:58 PM(UTC)
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Haiku can be good
But are sometimes confusing
Refrigerator
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francolargo  
#7 Posted : Monday, June 30, 2008 9:01:33 PM(UTC)
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IVY or Haiku?
Amplified or cascoded -
Lucky Buffalo!
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Russ White  
#8 Posted : Tuesday, July 1, 2008 10:55:05 AM(UTC)
Russ White

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AudioBear wrote:
1. I'm in the same boat as devodave (great name) and was wondering where the Haiku fits into the Buffalo -> Ivy/Haiku/Discrete stages in terms of sound quality.

2. Also as I'm pretty much single ended kit, would I only require one board and which would be the best option given 3 below.

3. I also guess going into a TVC would be fine?

So many questions, but I may as well ask them for everyone ;-)

As ever keep up the enormous amount of good work you do, if you ever need a helping hand let me know.

Russ


Hi Russ, (ok that just feels wierd)

1) I am finding it to be a pleasure to listen to. It probably will not have the ultra low distortion figures of the IVY, but it should sound great.

2) In a pinch you could use the Haiku single ended output. You could actually use half the output of a Buffalo or COD into half a Haiku. The best solution would be two use two Haiku to get two balanced outputs, then configure an IVY for BAL/SE conversion only (omit IC1 and IC2 and all the front end parts leaving only the BAL/SE section) you would wire the IVY balanced outputs as inputs. Then you would get the summed signal from the Haiku. This will get you much better DNR and THD.

3) I would think so.

Cheers!
Russ
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Russ White  
#9 Posted : Tuesday, July 1, 2008 6:45:12 PM(UTC)
Russ White

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I updated the image to reflect the fact that I added an emitter follower (with CCS) output to bring the output Z very very low. :)

Cheers!
Russ
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mikelm  
#10 Posted : Sunday, August 17, 2008 2:35:57 PM(UTC)
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Russ White wrote:

ocean delivers
mystically, impassive cod
ponders, dumbfounded




Oh - how I long to be a dumbfounded impassive cod . . . hehehe

Edited by user Sunday, August 17, 2008 2:36:45 PM(UTC)  | Reason: Not specified
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