[krisno]

OK. I am very sorry... you are right as always I guess.

You didn't swap out those resistors did you? ...

K

 

[krisno]

Does a high quality USB cable to the valab vs a cheaper one change the sound audibly to the better? anyone tried?

I need to fix this 'shrilling' and sharpness in the treble. It's strange I can only hear it on higher volumes, no matter what amp I use.

Can anyone confirm if the USB is directly converted to I2S and then send directly to the DAC chips without going through the DIR9001 as SPDIF?

Kris

 

[tubes]

Hey everyone, my nursery duties are over and it's time to get started on my basically stock dac. Looks like I have a bit of reading to catch up with all thats gone on in the last 2 months.

 

[dannie01]

Welcome back tubes. We want more input of this DAC.

 

[Ranchu]

Just a heads up, looks like the latest iteration of this dac is up on ebay, "gigalab".

It has two PS filter caps and philips coupling caps, all the clocks, looks good.

I ordered one, joining the club.

 

[Trapper32]

That gigalab looks nice...Sorely tempted to hit the BIN button...

 

[PatOMalley]

So I got my DEXA regulator in today and could not get it to work. All I got was a nice buzz sound. So I pulled it and went to put in a spare LT1084 I had on hand.

But when I fetched it it turned out to be a LT1085. What I read is that the 84 is 5v and the 85 is 3v. So it works in that space.

Weird thing is that I think it sounds better. Better bass. More body and heft. Why this is, if I am not kidding myself that is, I do not know. I do not think I am kidding myself. I was listening to Shubert's Trout which seemed gentle before the regulator fiasco. It now seems heftier and all that.

I still have the DEXA which has it's pins messed up from my fooling with it but it is still usable. Meaning that if anyone wants to have it free just ping me back. Jump Ball!

 

[Ranchu]

Amps!

Lol, you worried me, Pat, looks like the voltage setting resistors for the 317 and the 1085 are compatible, though (I checked

).

Enjoy.

 

[Ranchu]

Btw, I found some interesting information about that lm334 current source on the newer boards, and another interesting idea, seperate vref resistors for each chip.

From a very smart guy -ecdesigns- over at diya..

"Instead of using a resistor (Rv_ref), it's also possible to use a constant current source instead. This will prevent ground noise being dumped on the Vref input (and on the internal current reference source). Any HF interference on the Vref pin(s) will find it's way to the DAC outputs.

When connecting multiple Vref pins directly together, while there is the slightest voltage drop between the TDA1543 chips, crosstalk between the DAC chips will occur, this could result in a muddy sound as the internal current reference sources no longer provide a clean output current. An easy solution is to use a separate Rv_ref resistor for each chip, and solder it directly to the TDA1543 GND pin. The value of each separate Rv_ref resistor is the measured value (potentiometer) multiplied by the number of DAC chips.

Riv should be a single low noise resistor, if you use multiple resistors here, crosstalk will occur (voltage drop between the 16 DAC chips)."

diyAudio Forums Archive - Building the ultimate NOS DAC using TDA1541A

about a quarter of the way down the page, 30th post or around, lost count.

Most of it's way over my head, heh.

 

[r8833]

Quote:

Originally Posted by r8833 /img/forum/go_quote.gif Hi Bill, Would you think this mod would work with our DACs. diyAudio Forums and post#8 for explanation on mod diyAudio Forums - Diy-dac 1543 - Page 1 Rich

Ranchu,

I asked about this mod a few pages back, wondering if it would work with our dac..also a little over my head

Rich

 

[tubes]

I've had 4 of these dacs since buying the first one back in October 2008, the first dac came equipped with 2 x 1084 Vregs, later dacs have 1 x 1084 and 1 x LM317. I've always thought that first dac with 2 x 1084 had more slam and drive.

Question for Pat, do you use both the .22uf and .015uf caps for bypassing the output caps? I installed the .015uf caps and a 220uf cap on the Vreg which made for a huge sounstage and improvements in just about all areas but is also more vivid and steely, the steeliness might be from the 220uf Rubycon ZL cap.

 

[PatOMalley]

Hey Tubes,

The DAC had a 1084 stock in the 317 spot. After my attemtp to get the DEXA to work I replaced with a 1085 ... which is only a 3v reg. Is it possible that the 3v now allows the 5v to do a better job? Who knows?

I use both a .22uF an a .015 on top of that. There are three caps at output for each channel on my DAC. A BG 4.7uF bypassed /w a .22uF foil bypassed /w a .015 teflon.


Quote:

Originally Posted by tubes /img/forum/go_quote.gif I've had 4 of these dacs since buying the first one back in October 2008, the first dac came equipped with 2 x 1084 Vregs, later dacs have 1 x 1084 and 1 x LM317. I've always thought that first dac with 2 x 1084 had more slam and drive. Question for Pat, do you use both the .22uf and .015uf caps for bypassing the output caps? I installed the .015uf caps and a 220uf cap on the Vreg which made for a huge sounstage and improvements in just about all areas but is also more vivid and steely, the steeliness might be from the 220uf Rubycon ZL cap.

 

[Ranchu]

I did a lot of research on these NOS DACs before ordering, so I can share some of what I found..

General observations for mods, with views on cap types for the regs for Tubes (4!, the veteran!), and good info all around.

DIY - Summary of observations on non-oversampling dacs - pink fish media

For Rich, the current source mod looks simple, just a matter of figuring out which pins of it go where, but I think the vref blue potentioneter would have to be retuned again for low distortion afterward. I can take some close up pics of mine when it gets here, and help work it out if you like. Do you have a lot of rf noise on output? I think the 340 ohm from 390 ohm resistor change might have more to do with curing the clipping than the current source, but I'm guessing, really.

Kenwood BASIC M1

Pat, (another veteran!), I have to clarify, the differences in your old and new regs are their current ratings, 3A vs 5A, rather than volts, the voltage is set by two resistors R1 and R2, as here.

"Output voltage is set by two resistors R1 and R2 connected as shown below. The voltage across R1 is a constant 1.25 volts and the adjustment terminal current is less than 100uA. The output voltage can be closely approximated from Vout=1.25 * (1+(R2/R1)) which ignores the adjustment terminal current but will be close if the current through R1 and R2 is many times greater. A minimum load of about 10mA is required, so the value for R1 can be selected to drop 1.25 volts at 10mA or 120 ohms. Something less than 120 ohms can be used to insure the minimum current is greater than 10mA."

http://ourworld.compuserve.com/homep...den/page12.htm

I found this info after much wondering about how those resistors worked, the 1084 shares the same pinout and 1.25v value as the 317, good to know. Also, the 1084 regs are "low dropout voltage" regs, they only drop 1V between input and output, while the 317's drop 2V, this may account for the sonic differences Tubes mentioned...

Peace, all.

 

[tubes]

I just got done with the 9001 mod, jeez I feel like a neurosurgeon except my soldering iron was wagging around like I was in sword fight. Well, it worked and the steeliness I mentioned in my last post is gone, very nice improvement, Thanks Bill for coming up with this one. Next up is to wire the caps to the RCA's.

 

[krisno]

A huge letdown ?

I just bypassed my 4.7uf obbligato's with Ampohm 0.22uf paper in wax. It's only been running for 5 minutes, but it sounds almost distorted I feel. Much less clean sound or whatever.

I thought this was going to be good. Maybe bypassing is not for me, and just do myself a favour and use just 1 mundorf supreme .... hmm. I thought that it would become more realistic with this paper in wax. But well... break-in time?

It sound's much more unfocused and flatter..... i thought it would be just more vibrant and 'fatter' voices etc. hehe...