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Old 17th April 2009, 07:55 PM   #1
jkeny is offline jkeny  Ireland
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Default Buffalo Tweaking

I don't see anybody here investigating mods to the Buffalo Sabre DAC from Twisted Pear. Is there any interest in pooling here such info and peoples experiences?

Has anybody tried a different IV stage?
Has anybody tried some different PS supply configurations?

I have reason for asking this as I'm trying to help a friend realise a John Swenson IV stage (based on Gary Pimm's CCS) for the Dac. He has an IVY & Counterpoint & I thought that this IV stage might make a good comparison.

I'm OK with the JS IV stage as he has given lots of detailed info on it's workings & paramters (schematic attached). Will not be using the follower stage.

I'm looking for help with the following questions:
1.The current output of the buffalo is a high16mA, I think - if operating in SE output is this reduced to 8mA?
2 Do the IVY & Counterpoint use a resistor for converting I to V?
3. What's the best way of getting SE output from the Buffalo?


Any & all help appreciated!
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File Type: gif ccs iv stage compressed.gif (25.4 KB, 3169 views)
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Old 20th April 2009, 02:29 AM   #2
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I too was skeptical about the IVY output for my TP Buffalo. Spent a bunch of time isolating power on the dac board for the Saber chip and clock with limited success before I started playing with PS's for the IVY. Ended up switching the ALWSR's I was using to feed the IVY, for Teddy regs. I love those things, it was a big improvement. I had also built a C multiplier circuit suggested by Rod Elliot that is supposed to be used for Class A amps, but tried it in front of the teddy reg. Another audible improvement. In my system the Buffalo is now a monster, I really enjoy listening to it. Waiting now for Teddy Pardo's Super Teddy reg pcb's.
I would be interested to hear some ideas specifically for discrete Buffalo output stage also.
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Old 20th April 2009, 03:07 AM   #3
dviswa is offline dviswa  United States
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Hi compressit,

Can you post a schematic of what you have done?

Thx
Dinesh
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Old 20th April 2009, 07:46 AM   #4
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I will soon be replacing LCBPS/LCDPS with sigma11s for the Buffalo board and a sigma22 for the Counterpoints.
Haven't decided yet if I'll build two sigma11s to power the 6 and 6.6v rails of the Buffalo board or if it's too much of an overkill and I could just build one sigma11 for the analog rail (and power the digital rail with just the LCDPS).

In any case, I'll report back with my findings.
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Old 20th April 2009, 10:36 AM   #5
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dviswa,

C multiplier is here http://sound.westhost.com/project15.htm

Teddy reg attached. This is the original version. I do not use the accelerator. Lots more info on Pink Fish about these.
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Old 20th April 2009, 10:44 AM   #6
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Whoops, Teddy reg not attached.
Try this http://www.teddypardo.com
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Old 21st April 2009, 01:01 PM   #7
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Ross.

Great approach. Lots of good stuff is hidden in the endless threads about Buffalo and Sabre.

I just initialized a Wiki to bring it all together:

http://http//www.diyaudio.com/wiki/i...ification Wiki

I filled in some basic stuff already.

Lets hope that this is good approach.

Guys - feel free to add your stuff.

Cheers
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Old 21st April 2009, 01:59 PM   #8
jkeny is offline jkeny  Ireland
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Diagram of PS mods points:Click the image to open in full size.

I would suggest one other hugely important mod - feed the clock with a very low noise separate 3.3V supply - I don't know if anybody has done this & can report?
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Old 21st April 2009, 02:06 PM   #9
jkeny is offline jkeny  Ireland
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Leo, over on Art of sound forum, has replaced nearly all the PS supplies with Paul Hynes shunt regs:
1 x Z1A-3v3 positive shunt regulator set to 250mA which supplies main 3.3v and onboard Crystek 80mhz XO
1 x PR3G-1v2 positive series regulator supplying Sabres core and VDD1.2v
2 x Z1703v3 50mA positive shunt regulator supplying the Sabres left and right AVCC (VREF)
1 x Z1A-15 150mA positive shunt regulator set to 150mA supplying the +15v of the IVY I/V stage
1 x Z1N-15 150mA negative shunt regulator set to 150mA supplying the -15v of the IVY I/V stage

and he found:
Quote:
After powering up and having a quick sound check revealed much more detail, it sounded a little light though so I resisted temptation to listen too much at this early stage so left it alone to burn in, a few hours later the sound was far better, bass had much more depth but most of all was the improvement in the midrange !!!
Over the next few days it continued to improve to a point I was struggling to pull my self away from it, focus,detail with extremely clean and clear highs, unlike a lot of digital sources I've heard ,this unit had a total lack of HF distortion and sibilance, no grain!
The biggest plus for me was now the midrange purity which I felt was originally lacking with the standard Sabre, its actually infront of my TDA1541 dac at the moment
For anybody looking to experiment with PS these seem to be the current requirements:
Quote:
I have measured the current on the outputs of the 6.5v external regulated supplys
153.6mA's for the 3.3v LDO reg (VD)
61.3mA for the 1.2v LDO reg(VA)
35mA for the +/- 15v IVY (+v side measured)
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Old 21st April 2009, 03:04 PM   #10
jkeny is offline jkeny  Ireland
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Here's the PS schematic:

Click the image to open in full size.

Too much mixing of power supplies, I reckon.

The Va supply powering the LM4562, not surprisingly, has a big influence, as this op-amp acts as a voltage buffer for the left & right channel ref pins. The PS to these pins should also be as clean & low noise as possible. Is the op-amp a good idea?

The clock is supplied by a spur off the 3.3V main supply & should be separate & a much better regulator than a LDO
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