Dac-ah / Tda1543 - Cs8414 - Opa602 - diyAudio
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Old 23rd February 2005, 10:24 PM   #1
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Join Date: May 2004
Location: Sydney
Default Dac-ah / Tda1543 - Cs8414 - Opa602

Hi,

After reading so much info on this forum with regards to the non OS TDA1543 dac, I was keen to build it. While I was looking for a kit / schematic, I found that getting the completed product actually worked out cheaper. So I bought one directly from the manufacturer in China and it arrived last night. Here is a description:

Using CS8414 as digital input receiver, 8 pcs of TDA1543 in parallel (matched).
OPA602 OPAMP, On board with three separate rectifier and regulators provide power to digital and analogue circuit...


Here are my questions:

1. I opened the box and found the specification of the transformer:

I/P 40VA 0-115V 0-115V 50-60Hz-SCN
O/P 10V-0-10V 0.2A, 0-9.5V 0.7A, 0-10.5V 2.5A

My problem is that 230V is used in China, while 240V is used here in Australia. I have not turned it on yet until I am 100% sure (sorry I can't tell you how it sounds yet). My initial thought was that I would replace the transformer but now realised that there won't be such a transformer anywhere and the only way to get it is by placing a special order to a manufacturer which can be expensive. I have briefly inspected the board last night and found there are some reserves in the capacitor rating (like 30V filter caps used for the 18V-0-18V). The rectifiers are PEC 0483 GBU 4K. I can't see the regulator code for the 18V-0-18V, but for the rest LM7808CT is used.

Do you think it is OK not to worry about the difference between 230V and 240V? I guess I can but not 100% sure.


2. There are 2 OPA602 located near the output so I guess that they must be used as output buffers. I am a bit disappointed by that - but then with the cheap price I paid, what do I expect? I am worried that the sound wouldn't be truly high-end. I have a plenty of OPA2134 on hands but first I don't know if it is better or not, and secondly I don't find the OPA2134 good enough anyway. Can I replace it with OPA627? I kept hearing people saying it is good but have never listened to it. I heard that OPA627 is only available as single opamp but I guess OPA602 may be single opamp as well, otherwise why 2 are used on the board! By the way, anyone knows where I can get OPA627 in OZ? Farnell has run out of stock. Another thought is that if I build the DAC into my preamp then I can possibly be able to remove the output buffer. Unfortunately, I don't have the schematic because I bought it as a completed product, not a kit.


3. The purpose of buying the kit is also for playing and tweaking it. If you have any suggestions or good links, please throw them in.

Thanks and regards,
Bill
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Old 23rd February 2005, 11:02 PM   #2
vmac011 is offline vmac011  Serbia
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Join Date: Aug 2004
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I guess we both have same DAC. I've ordered mine from DIY Fidelity here in Oz. Here is the link

http://www.diyfidelity.com.au/index....2c9355b73f7307

I replaced output caps (22uf electolytic) with 3u9 poly which resulted in slightly better detail in mid/upper range. Now I'm contemplating reclocking it with Guido Tent's 12Mhz oscilator.

Don't worry about slightly higher AC from the toroid; regulators will take care of it. OPA602 is pin compatible with OPA627. I recomend you to keep OPA602 if you going to use longer cables to your amp (say, over 0.5m). If you intend to put your DAC close to amp (perhaps in the same box), then OPA627 sounds marginally clearer for pitchless instruments such as snare drums, cymbals, triangles etc. The difference is so insignificant that it's not worth 5 minutes of work with soldering iron.
Cheers
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Old 23rd February 2005, 11:08 PM   #3
vmac011 is offline vmac011  Serbia
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BTW,

try to order free samples of OPA627 directly from the Texas Instruments. http://focus.ti.com/docs/prod/folders/print/opa627.html
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Old 23rd February 2005, 11:34 PM   #4
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vmac011,

Thanks for your tips. Any more tips are welcome. Please post your result of the reclocking under this thread in the future.

I am surprised that electrolytic caps are used in output. In my case the output of the DAC goes to a valve preamp (I am building) so I think I will just shut it with a wire.

My only headache is that I will have to removed almost everything before I can get the PCB out of the box. Something I have to do when I have time.

Regards,
Bill
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Old 23rd February 2005, 11:55 PM   #5
vmac011 is offline vmac011  Serbia
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Did you mentioned VALVES? I am salivating - pass me a towel!

Listen, I have few spare OPA627. They are yours if you need them urgently.
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Old 24th February 2005, 12:05 AM   #6
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Thank you for your offer and I will certainly keep that in mind.

I have an active XO - LR4. The board is from Rod's / ESP. There is nothing wrong with Rod's design, and indeed, I don't think anybody can improve it. However, I just found that when using ICs the sound stage can get veiled a bit. I used OPA2134 in all of the stages including the output buffer. The HP output buffer is only unity gain buffer so I am not sure if OPA627 / OPA637 can really improve the sound. The LP output buffer has a gain less than 2. I don't know if it is worth the upgrade. If it is, I will face another problem - how can I replace a dual opamp with 2 single ones? Farnell may or may not have the adaptors, and Rod's board is tiny and space may be a problem. I am also thinking about building the active XO with tubes.

As for whether I will replace the OPA602 with OPA627 on the DAC-AH, I will have to listen to the DAC first. That is going to be tonight.

How do you like that sound of your DAC-AH? Where are you in OZ? I live in Sydney.

Regards,
Bill
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Old 24th February 2005, 02:56 AM   #7
vmac011 is offline vmac011  Serbia
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DAC sound really sweet. Its well suited for my kind of music (Rippingrtons, 4play, Lee Ritenour). The sound of piano and Jazz guitar is extremely well reproduced. Vocals as well. I have mixed feelings about hard rock. It sound a little too sharp. Most amazing thing that I never heard before was whilst listening Acouctic Alchemy (album Positive thinking) where I coud hear fingers sliding up the guitars fingrboard. Awesome, especially on el-cheapo full range JVC speakers loosely mounted in the shoebox

Cheers,

Vladimir
Sydney - BRW 2081
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