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Old 10th April 2012, 06:56 AM   #131
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cheers!

I've noticed one small issue or better to say a feature that has appeared after my small upgrade (I replaced all fake resistors to Dales, psu caps to BC, added 2x9 vac 2x300mA transformer) - I've got a real profusion of bass then before that sometimes makes me feel uncomfortable, especially when I'm using headphone preamp (based on two LME49710HA) inside the dac. This is not the case of preamp as I've checked and is not the input issue (it happens when connected either to usb or coax input).
It's great when I'm watching movies as I really don't need any sub, my monitors produce more bass than any floorstanding speakers I guess. However when using the dac with computer and headphones, it's quite an issue...

What could be wrong? I've checked and resoldered all the joints on pcb. I've got ~2mv and 8mv (left, right channels) DC offset from the dac if that helps.
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Old 11th April 2012, 06:42 AM   #132
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any advice?
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Old 1st May 2012, 05:16 AM   #133
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Just got the kit. I might have more questions later, but the first is about the pots. How do I set them and what are they for? They don't show up on the schematic I have. Working with V1.5 boards if it matter. Thanks in advance for the help.
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Old 15th May 2012, 04:16 PM   #134
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I have spent a couple of weeks listening to the Version 2.0 of this DAC, which I acquired from Zoe Tsang and installed in late April in a case with power transformers (separate dual 15 V and 9 V torodial transformers from Antek). It is a stock unit which I ordered assembled.

I am very impressed with the musicality and level of resolution of the unit. My prior DAC was one with four NOS TDA1543's. The Dual WM8740's equal the prior unit in musicality but exceed it substantially in resolution. For less than $100, including the Antek transformers, I believe it is a very good purchase.

With regard to maynard999's question. I have noticed from pictures of this DAC that certain versions have two trim pots. It is possible that this is attributable to those versions using an LM317 positive regulator and an LM337 negative regulator instead of the LM7815 and LM7915 which other versions use for the regulated audio power supply (in fact, although my version uses the LM7815 and LM7915, the printing on the board indicates LM317 and LM337). If that is the situation, then the trim pots probably simply set the regulated +/- 15 volt DC power supplies. Referring to the data sheets for the LM317 and LM337 regulators ought to provide insight on how to trim each of the pots to achieve +/- 15V out of the regulators (note the pins are different on the positive LM317 and the negative LM337. I believe you simply set the volt meter between the out pin of each regulator and ground and adjust the appropriate pot to as closely to 15 volts as possible.

Last edited by senordilys3542; 15th May 2012 at 04:23 PM.
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Old 15th May 2012, 05:01 PM   #135
gfiandy is offline gfiandy  United Kingdom
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TheGimp, I think you may have misinterpreted what the clock on the DIR9001 does. It is not used to reconstruct the received clock from the SPDIF signal; it is just used to calculate what the in coming clock rate is so the DIR9001 can configure the PLL to best recover the clock or in a system (such as an AV amp) to run the ADC when there is no in comming digital signal to lock to.

The clock that is passed to the DAC is recovered from the SPDIF data by the PLL. If you want a SPDIF receiver that uses a crystal to reduce jitter you either need to use the WM8805; which uses a very clever digital circuit to re-time from a crystal. Or you need to post filter the clock recovered by the SPDIF receiver (DIR9001) using a PLL that uses a crystal and bends its frequency to achieve lock. I have done this by using varicap diode loads on crystals and adjusting the cap load till the PLL achieves lock with the in coming recovered clock but it is difficult and wont always lock to poor sources.

The other option is to have the clock free running and use a FIFO to take up any variation between the source clock and the local DAC clock. This works well but eventually the FIFO will run out and a sample has to be repeated or lost (This can be a once a day event if the FIFO is large enough though.

For information on the PLL See Page 16 of the DIR9001 datasheet where it says:-

The DIR9001 requires an XTI source for following purposes:
The measurement reference clock of actual-sampling-frequency calculator
The clock source for the XTI source mode (CKSEL = H setting)
(That is, the DIR9001 does not require an XTI source if it is only decoding the biphase input signal.)

http://www.ti.com/lit/ds/sles198/sles198.pdf

Regards,
Andrew
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Old 3rd June 2012, 08:37 PM   #136
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Just finished, I replaced all the components except the SMD. All the 47uf and 10uf electrolytics are Sanyo OS-CON, the red caps are all WIMA. I'm using two NE5534, but I'm planning to swap them with some JFET op-amp. The resistors are 1% metal film.

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Old 4th June 2012, 09:17 AM   #137
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Default nice set up

so how does it sound?
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Old 4th June 2012, 01:15 PM   #138
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Very Good, compared to the internal DAC of my NAD 545BEE the entire bandwidth is wider and more detailed. The medium band is really wonderful, I was listening to a Kurt Ellings HD flac and I had the feeling to have him just in front of me.
Now, considering the good result, I'm plunning to change the OP-AMP with a JFET model and a lower noise and buy it a more fashionable dress
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Old 26th June 2012, 02:01 PM   #139
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Anyone know more about the update to wm8741? I have not quite clear. On the website of the 8740/8741/8742 Wolfson are pin-compatible. But then I found this:

Wolfson WM8741 Stereo Audio DAC


The WM8741 is a replacement for the WM8740 near - which has since Been Around, I believe, 2004. Not a direct replacement Different Because It is operationally in allowable voltage rails: the WM8740 analog allowed the rail to be Between 3.0 V and 5.5 V. With the WM8741 the range is 4.5 V to 5.5 V. On the digital interface Allows the WM8740 from 3.0 V to 5.5 V while the WM8741 tightens it to 3.0 V to 3.6 V. Also, if your application use the WM8740 current mode you can not replace the multiplexers With The newer part one, Because the muxes are not there.[/I]

Anyway, this DAC ebay, I want to upgrade to wm8741 but idk if I'm going to have problems. The wm8741 is not cheap.


Another theme for your interest. Is that the power of this DAC is bad, like all DAC kits ebay. The 7808 is a regulator that produces a lot of noise, the better an LM317 for example. I'm using this:

TeddyPardo


Click the image to open in full size.

(These are for pcb WM8740, analog and digital)

a low noise regulator for DAC. It's an interesting idea if you want to improve the sound of your DAC.
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Old 27th June 2012, 01:55 AM   #140
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So, how great is it? What's the PSU noise?
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