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sureshm  
#1 Posted : Monday, November 5, 2012 8:46:48 PM(UTC)
sureshm

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After 3 years of compiling parts and waiting for the spare time, I have finally put together my DAC. Design and photo of the build is attached. I still have to case it up and move it to my main listening system. So far it works :) It sounds very good and well worth the time invested in the project. More comments on how it sounds after I hook it up to my main speakers. Comments on design and layout welcome. Thanks.
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Adastra  
#2 Posted : Monday, November 12, 2012 3:13:08 AM(UTC)
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Can you explain your output stages? Looks like a IVY to Cinemag tranformer feeding something... Just curious and always interested.
Thanks!

Edit: Oops, missed that second attachement. Can I ask why you are running the Jensens and line amps rather than just outputting the Ivy straight out?

Edited by user Monday, November 12, 2012 3:26:45 AM(UTC)  | Reason: Not specified

sureshm  
#3 Posted : Monday, November 12, 2012 10:46:41 PM(UTC)
sureshm

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The first attachment is not displayed properly so I think most people have missed it.

I am actually using a legato. I originally bought some transformers because I was curious to hear how it sounds after reading about other people trying it. I liked the sound of the transformer output directly from the Buffalo, but after I connect the Legato in between the two it sound much more dynamic. The difference being that the Buffalo is running in current mode with the Legato vs voltage mode with the transformers connected directly to it.

With a transformer, you need to keep the wire length of the output very short. I also wanted to power my headphones directly. Therefore the line stage I already had spare came in to the design. The Ventus would also be an excellent choice. I now have a DAC that had a great headphone amp and could also handle exotic high capacitance long interconnects.

In my own mind I justified having the transformer in the middle. It does the SE conversion (no opamp or nasty caps), has high CMRR (higher than a opamp?) which is important to make better use of a balanced DAC output, provides high frequency filtering as it can not pass through frequencies higher than say 200khz, lastly it provides ground isolation (the DAC + legato has a different ground to the linestage).

Someone with more audio knowledge than me would probably say that the marginal audio gains are not worth the extra costs. But it is DIY and I just want to have something different :)
gwikse  
#4 Posted : Monday, November 12, 2012 10:52:35 PM(UTC)
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Looks like it should be very good. I take it that you use the Balanced outputs from the Legato to the Lundahl`s in order to avoid using op-amps?

Have you considered running the Legato from the Sigma22? I was playing around with a simular consept for a friend of mine. He ended up with a complete Pre-amp using the Delta1+2 and Alpha20`s and B2 with Ivy. However we ended up using the Sigma22 for both the Alpha20`s and the Ivy. His was set to 15V though. I plan to do the same (with my COD`s), but I will use newclassD regulators to lower the voltage from the sigma from 18V down to 15V for the Ivy.
sureshm  
#5 Posted : Monday, November 12, 2012 11:31:28 PM(UTC)
sureshm

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Yes the balanced output of the legato go to the Jensen transformer.

Originally I had the Sigma22 powering both the Alpha20 and Legato. I then bought the Placid HD to have them powered separately but then also get ground separation. I picked the Placid because it was easily available in stock and I just wanted to try out Russ' new design.
Russ White  
#6 Posted : Thursday, November 15, 2012 11:07:55 PM(UTC)
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Nice work! Glad your enjoying it.
barrows  
#7 Posted : Saturday, November 24, 2012 4:35:16 PM(UTC)
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sureshm: nice work. I am interested in transformer coupling the output of the Legato III as well, as this would eliminate the DC issue, and create a nice RF filter as well. I am interested in which model of Jensen you chose, and what are feelings as to whether the output impedance of the Legato (around 150 ohms perphase stock, mine is around 180 ohms) is low enough to drive the Jensen for low distortion, as my understanding is thta transformers need to be driven from a low impedance to achieve good perfrormance. I am also going to ask this question of the Jensen folks, and Lundahl distributors.
I run short cables, so no need for me to buffer the output after the transformer, but I ma wondering if I need to buffer it before the transformer. I also run balanced only, so no need ot do any converting to SE... just considering the transfomrer to get rid of the DC to G, and entirely block RF on the output.
I actually suspect that some of the "magic" heard from some tube gear, is actually a result of transformer coupling and not the tubes themselves: RF seems to have a way of contaminating signals in a subtle but annoying fashion...
sureshm  
#8 Posted : Saturday, November 24, 2012 6:54:06 PM(UTC)
sureshm

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My buffalo is now in a case (although a very boring one). Also upgraded to AVCC v2.1.

I am using it with NAKSA 70 amp and PMC Fact 8 Speakers. The buffalo just sounds amazing. I almost feel like giving up on further tweaking and just enjoy the music. My previous source was a modified squeezebox so this was always going to sound better.
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sureshm  
#9 Posted : Saturday, November 24, 2012 7:06:02 PM(UTC)
sureshm

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Barrows: I chose the JT-11P-1 which is a 1:1 10k transformer. Since the impedance the legato sees is 10k I think it powers it easily. With a 600ohm transformer it would struggle. I have seen some designs with a buffer before the transformer to lower the impedance but my main concern was my interconnects being about 1m and Jensen advice to keep it below 45cm for optimum performance. Plus I get a headphone amp as a bonus.

I agree that some of the magic of tubes could be the transformer. I just liked the idea because I thought it might take the “digital edge” off and also breaks any feedback in the loop (although the legato is a no feedback design).
barrows  
#10 Posted : Sunday, November 25, 2012 8:17:04 PM(UTC)
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sureshm: thanks for the details. I see you used an input transformer, so it makes perfect sense that you would want the buffer after the transformer. I am glad that you are enjoying the sound.
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