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Old 14th July 2012, 11:33 PM   #1
Autotat is offline Autotat  United Kingdom
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Default Digital Pre-Amp Build Help Request

Hello Folks,

I have been bimbling around on here asking inane questions for about a week now but I think I am now ready for my first proper thought out request. This will look very familiar to those who helped me in my very similar previous thread. I have started this new thread as I think I now have a better idea of what I would like to end up with.

I no longer have any analogue components to plug into my pre-amp as all my music has been transferred to a networked external hard drive accessed via a Media Centre PC that I recently assembled. This feeds its digital signal to a Yamaha DSP E800 AV Processor that does the converting and sends the analogue signal to the power-amps.


The Plan

I want to build a high quality DAC pre-amp using my old Cambridge Audio C500 as a basis. What I would like to have is:

1) Highest quality DAC I can afford to build (don't we all).
2) Selectable multiple inputs including USB, Toslink, Coaxial, 3.5mm Jack (just in case).
3) An optical and/or Coaxial pass through for forwarding the digital signal to other devices (just in case).
4) Preferably powered by existing on-board toroidal power supply.
5) I would like to utilise the existing input selector to switch between the inputs.

Here again are a couple of pics to show what I have to play with:

Click the image to open in full size.

Click the image to open in full size.


Initial Progress

First of all, after spending the last week re-assessing my Hi-Fi and doing some re-plumbing, I have finally decided what I want to do as outlined above. Until, that is, you lot tell me I'm dreaming!

As the C500 is currently redundant, I'm happy to have a serious go at DIY and make something myself.

I have already received these two recommendations:

DAC 2496 (AK4393) DAC KIT With CS8416+AK4393+5532 (thanks boblamont)

MUSE Mini 24Bit 192Khz Coaxial Optical USB Input DAC Headphone Out,66*60mm | eBay (thanks Pano)

and also the ODAC (thanks orpheus) but as stated above, I have decided I want to try DIY. (I'd also like to thank qusp for his input in the previous thread, it all helps un-muddy the water).


Next Step

More information gathering and recommended products.

So does my wish list look achievable?

Are there any other DAC kits out there to consider? If there are any that perform outstanding results after a few choice mods, I'd like to build those mods in from the start as I doubt I'll have the chance to do too much experimenting.

As for budget, over a period of time I would like to keep the cost below 100 but if this causes too much of a restriction I would rather go over budget a bit and get a better quality result. The kits I've seen so far all seem to be around the 30 mark which considering how much a commercially built digital amp sells for, seems rather cheap!

Finally, many CD players now come with multiple DACs. Is this a direction worth pursuing? I haven't seen much mention of it on here.

I'm no electrical engineer and am woefully unfamiliar with many of the terms used on here. But I am handy with a soldering iron, can follow instructions, have access through work to some decent kit and have access to a number of electricians who are willing to help.

Many thanks for any help and guidance, I have already had my eyes opened in the past week on here.

Cheers,

Simon.
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Old 16th July 2012, 06:13 PM   #2
Autotat is offline Autotat  United Kingdom
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I have found the below DAC that has multiple inputs and includes a switching device to select them. Does anyone have any experience of these? I'm not too fussed about the remote or the display, especially if I can substitute the existing input selector on the pre-amp in place of this boards selector.

Dual CS4398 CS8416 24Bit/192KHZ DAC+ VFD Display+Remote | eBay

Or would I be able to incorporate the input selector into the wiring of the other two DAC boards easily enough?
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Old 19th July 2012, 10:27 PM   #3
YohY is offline YohY  United Kingdom
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Default CS4398 Dual Dac kit

Quote:
Originally Posted by Autotat View Post
I have found the below DAC that has multiple inputs and includes a switching device to select them. Does anyone have any experience of these? I'm not too fussed about the remote or the display, especially if I can substitute the existing input selector on the pre-amp in place of this boards selector.

Dual CS4398 CS8416 24Bit/192KHZ DAC+ VFD Display+Remote | eBay

Or would I be able to incorporate the input selector into the wiring of the other two DAC boards easily enough?
Simon -

Just seen your thread about conversion of your preamp..

With the above dac, it takes full control of the media center (via USB), so becomes it's own multiple input switching / track selection (skip Forward or Reverse), AND controls it's volume output - All via the supplied remote control ! It's totally cool

Also, you can configure your laptop to use 'Advanced Touchpad' and control mouse functions via your smart phone - OR - use 'Unified Remote' to turn said smart phone into a wifi remote control which will again give you track selection/volume command from any room in your property (or as far as your wifi allows).

Hope this helps - let us know how you get on with your project !

-Andy-
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Old 20th July 2012, 10:46 AM   #4
Autotat is offline Autotat  United Kingdom
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Wow, it sounds like quite a piece of kit! I'll have to be carefull however as my media centre PC also operates via a media remote.

Click the image to open in full size.

Could you please confirm that it does have both optical and coaxial digital inputs?

I might end up bypassing even more of the existing pre-amps circuitry with this board. If the volume control has the range, I won't need to risk muddying the signal by sending it through the Pre-amps rotary analogue volume control and the tone controls are set to bypass anyway (though this again means sending the signal through the potentialy dirty contacts of a mechanical sliding selector). In fact all that may remain of the original at this rate is the case and possibly the power supply!

It would be nice to retain one analogue input just in case as I do still own a ver nice Yamaha KX580SE tape deck but it has been boxed up for a while now.

Thanks for the reply.

Simon.
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Old 20th July 2012, 01:13 PM   #5
Autotat is offline Autotat  United Kingdom
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Right, I have finaly managed to measure the output voltage of the toroidal transformer in the pre-amp.

29.78V D.C. (2. off) Regulated

35v D.C. (1. off) Unregulated

So it doesn't look like it is going to be suitable for any of the DAC's I've seen so far.

That kind of knocks that idea on the head then. Oh well, I'll just have to start from scratch.
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Old 20th July 2012, 05:17 PM   #6
YohY is offline YohY  United Kingdom
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Default stay focused glasshopper...

Quote:
Originally Posted by Autotat View Post
That kind of knocks that idea on the head then. Oh well, I'll just have to start from scratch.

No it doesn't - you have the power, all you need is to reduce it !

Take a look at these :-

DC Buck Converter Power Supply 4.5-35V to 1.25-30V 3A Stepdown Voltage Regulator | eBay

As you mentioned, you haven't much electronic experience, but like all of us you have to start somewhere

The dac has regulation onboard (that's why it requires the A.C input power feeds), but this doesn't matter as you
already have D.C power already available.. Happy days !
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Old 20th July 2012, 05:27 PM   #7
YohY is offline YohY  United Kingdom
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Si,

The electrical digital inputs on the board (spdif/I2S) are solder pad connections (unterminated), that's why you can't see any connectors for them..
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Old 20th July 2012, 05:30 PM   #8
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What Amplification you gonna use for this new media center setup ?
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Old 20th July 2012, 06:07 PM   #9
Autotat is offline Autotat  United Kingdom
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Ooh this is looking good again! Thanks for that!

Will this give a clean power source still or is it liable to induce noise?

Thanks also for confirming the presence of the electrical digital inputs.

ApogeeLover, I am hoping to use the above converted Pre-amp to feed my pair of long serving Cambridge Audio P500 power-amps that are Bi-Amping a pair of Mission 734i Speakers.

Thanks very much for the help, Time to start doing some serious saving. I feel an eBay purge coming on! Anyone want any old VW Campervan bits?
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Old 20th July 2012, 09:58 PM   #10
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Hi Autotat,

Are you aware that your media center is probably and rather nastily upsampling everything it sends over "Digital" to 48000 Hz?

Configuring MPD for Bit Perfect Playback with an external DAC Init

I use MPD on a Linux media center bypassing the software mixer and my DAC says 44100 Hz when I play some of my ripped flacs. I don't know if your Yamaha tells you the sampling rate or not.
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