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Old 7th May 2002, 06:24 AM   #1
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Question CS4397 and Zapfilter II

Hi,

I am having some problems using the Zapfilter II with my DAC. The DAC( Cirrus evaluation board) has the CS4397 chip and I connectd the analogue outputs to the Zapfilter II's inputs. I set the Zapfilter to accept voltage output from the CS4397. However, the output from the Zapfilter II is very low. I have to max the volume control in my pre to hear any output from my speakers. Any idea what could be wrong?

I have sent a few emails including the schematic of the DAC to LC Audio requesting for help. But so far no reply.

BTW, I took the CS4397 analogue outputs and connected these directly to my pre-amp. It sounds great!

Thanks,

N.S.
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Old 7th May 2002, 09:45 AM   #2
ghg is offline ghg  Austria
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Hi

How much did you shell out for the eval board ?

ciao

Gary
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Old 7th May 2002, 09:47 AM   #3
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Did you mean that you did not use the analog filter of the eval board? I have the same board and I am wondering if that can work...

PS.
What is a ZapfilterII

Greetings,

Thijs
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Old 8th May 2002, 03:29 AM   #4
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Quote:
Originally posted by ghg
Hi

How much did you shell out for the eval board ?

ciao

Gary
Hi,

I paid $150 for the eval board complete with a simple wall socket power supply. You can also purchase an upsampling board based on the CS8420 chip for $150 as well.

N.S.
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Old 8th May 2002, 04:04 AM   #5
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Quote:
Originally posted by tschrama
Did you mean that you did not use the analog filter of the eval board? I have the same board and I am wondering if that can work...

PS.
What is a ZapfilterII

Greetings,

Thijs
Hi,

I tapped the analog out signals from the inputs to the opamp. Pin 2 and 3 are the inputs to the opamp. I am using XLR connections. Since the opamps are socketed, they can be easily removed. At first I listened via my headphones. I could not detect any out of band ultrasonics or harmonics. Well, it sounded fine. When I played it through my amps and speakers, the sound was very neutral with very clean and extended treble. Then I decided to try another experiment. I tapped the analog signals directly from the output of the CS4397. Again, I did not hear any noise or distortion. Therefore, I am wondering if I need the analog filter stage? FYI, I am using a Sonic Frontier Line 2 pre-amp, a Marchand XM9 active crossover, a pair of Musical Fidelity F15 power amps driving a pair of Apogee Stage.

The Zapfilter is a high quality analog stage for CD player. I purchased this to replace the opamp output stage in my Sony cd player. I decided to use it with my eval board instead. Unfortunately, I am having some problems and my many emails went unanswered. See http://www.lcaudio.com/zapfilter.htm. BTW, do you have the CS8420 sample rate converter eval board?

N.S.
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Old 8th May 2002, 08:51 AM   #6
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Thanks for your reply.

I have the DAC eval board with the CS4397 chip etc. but no CS8420 sample rate converter eval board. I use it with my Philips coax digital out CD-player.

I have played around with both the Philips and the eval board opamp types. Changing to OPA134 made a difference and the DAC's now are more alike. Just a bit more bass definition from the eval board compared to the philips build in DAC.

The eval board is housed in a 19" chassis that also contains my MOSFET buffer pre-amp/headphone-amp. It's a complete digital/analog pre-amp system with headphone output and I like it!

I would like to try the output directly from the DAc chip but my stepped attenuator is a 10K Ohm type, so it might load the DAC chip down to much (?). Do I understand it corrected that it has a balanced output, (the DAC chip that is)?

Greetings,

Thijs
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Old 9th May 2002, 02:43 AM   #7
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Quote:
Originally posted by tschrama
Thanks for your reply.

I have the DAC eval board with the CS4397 chip etc. but no CS8420 sample rate converter eval board. I use it with my Philips coax digital out CD-player.

I have played around with both the Philips and the eval board opamp types. Changing to OPA134 made a difference and the DAC's now are more alike. Just a bit more bass definition from the eval board compared to the philips build in DAC.

The eval board is housed in a 19" chassis that also contains my MOSFET buffer pre-amp/headphone-amp. It's a complete digital/analog pre-amp system with headphone output and I like it!

I would like to try the output directly from the DAc chip but my stepped attenuator is a 10K Ohm type, so it might load the DAC chip down to much (?). Do I understand it corrected that it has a balanced output, (the DAC chip that is)?

Greetings,

Thijs
Hi,

The CS4397 has differential outputs. Pin 19 is right (-) analog out,
pin 20 is right (+) analog out, pin 23 is left (+) analog out and pin 24 is left (-) analog out. Pins 23,24 are analog grounds. The opamps actually convert the differential outputs to unbalanced signals.

N.S.
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Old 28th January 2008, 10:00 PM   #8
Jolojl is offline Jolojl  Sweden
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Hi!

I was browsing around to find some information about the CS4397 and I think I found what I was looking for in this thread, I just need to get it confirmed. I am really really new to DIY and electronics (actually made my first soldering yesterday ...). So please bear with stupid/ignorant questions ...

I just received a ready made kit with from eBay. It comes with a standard OP AMP but I have never planned to use the OP AMP, instead I was hoping a friend would build a tube output.

This is the kit.
Click the image to open in full size.

Looking around on the web I have seen people taking the signal straight from the TDA 1543 chip through a capacitor (since that chip has internal IV conversion). I was thinking why not try this with my the CS4397 since it also is a voltage output chip. Now I was adviced to check if it had enough current drive to make this possible. I haven't been able to find that info.

In this thread people seem to have connected the output of the DAC chip straight to their (pre-)amps.

1) Is this possible then?
2) Is it recommended?
3) Does anyone know what current drive the DAC chip has?

Thanks for any help!
Johan
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Old 29th January 2008, 12:43 AM   #9
tedr is offline tedr  United States
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Default current drive

if the DAC IC is voltage out, then it is expected you will connect it to a high impedance, 10kOhms or more. The current required is so small it is never specified. Sometimes with opamps you see a specification for minimum load impedance and current output capability, but that spec is not usually given for a DAC, it is assumed you will connect it to a preamp or amplifier having a high impedance input. You could chose 10kOhm load or something higher like 100kOhm load, it makes no difference to the DAC output signal which remains the same voltage amplitude. If you did something silly, like use 1kOhm or 100Ohm the output voltage would fall and probably there would be increased distortion!

Ted
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Old 29th January 2008, 06:33 PM   #10
Jolojl is offline Jolojl  Sweden
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Hi Ted!

Thanks for your input! I did the easy resoldering today and picked the same signal (it's a balanced output) on both sides just before the OP AMPs, and it works without problem. The voltage is lower than 2V, one has to put the volume up a bit, but the sound is very promising!

Thanks again!
Johan
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