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Old 23rd April 2008, 03:01 PM   #581
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I am feeling quite at home with 392 and 93 . Now ... ist is time for some component upgrade .
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Old 23rd April 2008, 03:23 PM   #582
johnm is offline johnm  United Kingdom
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You must be using a 32 then? I'm using the 31.

OneyedK wrote:

"RCEZ32 and RCEZ31 have different output ports, RCEZ32 is capable of more output current and has less internal resistance.
So i'd say;
RCEZ32: 392 / 93.1 Ohm
RCEZ31: 291 / 100 Ohm (rated output current is 12mA)

Bad impedance matching or overloading the output will induce jitter and heavily influence the sound."

Which upgrades do you plan on doing first?
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Old 23rd April 2008, 03:39 PM   #583
kevinkr is offline kevinkr  United States
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Quote:
Originally posted by johnm
You must be using a 32 then? I'm using the 31.

OneyedK wrote:

"RCEZ32 and RCEZ31 have different output ports, RCEZ32 is capable of more output current and has less internal resistance.
So i'd say;
RCEZ32: 392 / 93.1 Ohm
RCEZ31: 291 / 100 Ohm (rated output current is 12mA)

Bad impedance matching or overloading the output will induce jitter and heavily influence the sound."

Which upgrades do you plan on doing first?
Looking at the specs for the LA9241 and LA9242 I see no difference in how the dout port is specified so I would assume the same for both. Based on accepted practice that would typically be 390 and 93 ohms or thereabout. The key is a thevenin source impedance of 75 ohms to the cable, and not to significantly exceed 12mA current from the Dout port of the DSP.
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Old 23rd April 2008, 03:39 PM   #584
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Yes I know about the( presumed) differences between the 31 and 32 output ,but yesterday I tried the 392 / 93 and I am very very iinterested with the sound .In a relaxed way . So I will listen for a week or so like that and then will try again the 291/100. And I am quite amazed hearing such differences .
Ok my dac uses CS8416 at 3,3 supply and from the datasheet the inputs accepts very little currents . I mean at this little levels I have the suspect that it can be done even better on power supply and caps . Now I am using 1% metal film resistors for the divider , and I am planning to find some carbon .

I have some specific idea for supporting frame and when realized will let you know ( and see maybe ehehe )
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Old 23rd April 2008, 03:39 PM   #585
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sorry for the delay. Yes, the visions.ca units are legit. Also, Best Buy (Canada) has these in stock from time-to-time. I was able to get one from both sources. Looks like the stock from both vendors is well into the 100s of units.

As for a group buy... IMHO, the only way to do this would be someone in Canada to organize the whole shebang, or ship the disassembled units in a single shipment to someone who would then organize the group buy.

If we did do a group buy, I'd recommend having a parts option as well, as I ended up ordering all the parts from 3 separate vendors. This option would be for those who don't really have a large stock of parts to tweak with, or just want to go with Peter's recommendations.

On another note, I recently ordered a custom R-Core 2x10 VAC 50VA transformer that I'll be able to compare to the Hammond EI that Peter recommends. It won't be here for a month or so.
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Old 23rd April 2008, 04:42 PM   #586
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Quote:
Originally posted by Gopher
Does anyone have any ideas WHY this el cheapo boombox transport should apparently outperform massively engineered super transports?

I'm sure they just built it to a price with absolutely no consideration given to it's audiophile qualities?

Pure luck?
I'm not trying too be flattering here.......but Peter has alot to do with it. He has a proven track record when it comes to design and getting great results from minimal equipment. In a recent 6moons of Pass Labs XA30.5, Peter's Patek once again garnered some very positive comments when being compared to products two to four times it's cost.

As another illustration of this point. I have two NOS DACs. One is a TDA1541A and the other is Peter's TDA1543. For the cost Peter's TDA1543 does very well. I had to spend alot more money to better it.

Regards,
Dan
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Old 23rd April 2008, 05:21 PM   #587
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Default RC-EZ31 availability in Canada

First, a big thanks to Peter for sharing with us this
wonderful find and his modifications.

I just checked the bestbuy.ca site and it looks like the
RC-EZ31 is available again. You may be able to find it in you
local Best Buy stores as well. (The Toronto area stores
seem to have them.)

Dennis
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Old 23rd April 2008, 05:27 PM   #588
johnm is offline johnm  United Kingdom
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Could someone please tell me - in layman's terms if possible - why it's important to set up the digital output to support a 75 ohm impedence, when it's accepted that a phono socket is not 75 ohms (even if the cable might well be)? Shouldn't it take into account the two phono connectors?

I guess the easy way out of this is to use a BNC? (which I shall experiment with when I get around to building a Shigaclone DAC).

Cheers,

- John

P.S. Just added (as I had it lying around) an Elna Silmic ARS 470uF / 63V to the C952 position, and it seems to have resulted in extra 'punch', and - interestingly - more delicacy on female vocals in particular. I know Peter left this position blank, but using the Elna seems to have resulted in an improvement.
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Old 23rd April 2008, 05:47 PM   #589
kevinkr is offline kevinkr  United States
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Quote:
Originally posted by johnm
Could someone please tell me - in layman's terms if possible - why it's important to set up the digital output to support a 75 ohm impedence, when it's accepted that a phono socket is not 75 ohms (even if the cable might well be)? Shouldn't it take into account the two phono connectors?

I guess the easy way out of this is to use a BNC? (which I shall experiment with when I get around to building a Shigaclone DAC).

Cheers,

- John

P.S. Just added (as I had it lying around) an Elna Silmic ARS 470uF / 63V to the C952 position, and it seems to have resulted in extra 'punch', and - interestingly - more delicacy on female vocals in particular. I know Peter left this position blank, but using the Elna seems to have resulted in an improvement.

Hi John,
C952 (470uF) in the RCEZ31 is the same location as C950 (1000uF) in the RCEZ32. I removed C950 which to my surprise resulted in quite a loss in performance. I then installed a 100uF Silmic and noted that it seemed much as before - perhaps even a bit better.

The board I am currently using has the stock for RCEZ32 1000uF cap. I will try a much better cap in this location when I have some time to listen critically again.

I have not yet started to mess with the tracking servo cap that everyone is wrestling with. I might leave it alone on this board.

On the spdif matching the idea is minimize impedance mismatches and the reflections they cause. Unfortunately RCA jacks and plugs do cause a mismatch - some are worse than others apparently, but without a TDR it is hard to tell. I have been evaluating the change with an actual 75 ohm bnc as opposed to the 50 ohm ones I've been using. Matching to the cable prevents signal fidelity issues that would otherwise occur - unmatched the cable looks like a lumped LC network which has an effect on bandwidth and group delay. I think it is pretty critical and I am trying to stick to the technically correct approach and figure out the interactions where possible and eliminate as many of them as I can. (FWIW I use all bnc on all of my homebrew digital gear, regrettably until recently I was having trouble sourcing 75 ohm hardware so some of it is still 50 ohm.)
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Old 23rd April 2008, 06:09 PM   #590
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Quote:
Originally posted by johnm
You must be using a 32 then? I'm using the 31.
I am using the 31 also .
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