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PostPosted: 12 Oct 2008, 07:38 
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Joined: 04 Jun 2008, 21:02
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Location: Philippines
I have been building DACs from kits and have been reading a lot about tweaking CD players, but I did not have the courage to butcher my CD players.

Early this year, I was able to buy a very decent, excellent sounding Denon CD player, it is so inexpensive that I felt so encourage to tweak it.

First thing that I did was replaced the PSU capacitors to Aerovox electrolytics, noticeable improvement on sound. Encouraged, I replaced the electrolytic output capacitor with a very inexpensive Wima MKP (polypropylene), and wow, better dynamics, bass improved. Next was the removal of muting transistors, with trembling hands, I removed the 4 muting capacitors (on hindsight, I should just have wired the output caps directly to the RCA sockets, simpler and safer!)

Encouraged again, I figure I will replace the opamp output stage with a tubed output stage. So I took note of the DAC of my vintage CD player, it is the Burr Brown PCM61P, 18-bit DA converter, 8X oversampling. This particular DAC (lucky for me) has both Io (current output) and Vo (voltage output), which means the opamp is built in into the DAC. Every DIYers on the net says that the best is to tap from the Io (current output) of the DAC, build an I/V (current to voltage converter) and feed the signal to the grid of the tube stage.

After a few weeks of research, I decided to use my favorite 9-pin tube, 6n1p (beside from being CHEAP, it sounds great).

According to the data sheet of the PCM61P, the Io is capable of 1V output, so I really don't need a lot of gain.

After wiring and soldering the tube stage, power up the CDP, it sounded so awful, no mids and no bass, just shrill noise. Back to the drawing board, after a couple of weeks of banging my head (this is my first SS into a tube stage project), I decided to isolate the current output of the DAC totally from the circuit and tied all the opamp input of the DAC to ground (reduce noise), voila, music! A lot better! After a week or so, I decided to tweak the I/V converter, and wow! Sound worth all the effort and time I put into it.

Here are some pictures:

Image
Now that only tweak I need to do is have the scratched chassis painted at my work (Nippon Paint), flat black, or maybe some nice Honda color.

Image


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PostPosted: 12 Oct 2008, 08:08 
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Joined: 06 Jun 2008, 20:12
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This is one of the coolest tweaks I have seen in quite a while. TUBES on a CD player. Crazy Alex :)
If you want some incredible sound try getting your hands on a Sony Playstation 1 with part number SCPH-1001. Tweak the heck out of it. I have not changed mine at all and it sounds fantastic but there are lots of tweaks and a tube tweak would be really neat to see.
Nice job :)
Do you plan anything further with it or is this complete?
Ri

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PostPosted: 12 Oct 2008, 09:55 
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Alex, that is great work! What is the model of that Denon CDP?

I like to remove the output capacitor altogether since I make sure that all my preamplifier and integrated amplifiers have an input capacitor. Also, I don't use a input capacitor on power amps since my preamps always have an output capacitor.

Another CDP tweak I have seen done before is stiffening the transport with epoxy and the addition of damping.

Cheers

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PostPosted: 15 Oct 2008, 03:32 
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I am planning to dampen the whole cabinet with roof flashing tapes (foil tapes with asphalt/tar material on it). I might also completely replace all the electrolytic caps on the PCB board.

The Denon is a CDP 590, it has a Burr Brown PCM61 DAC per channel. This DAC has a built-in op amp which I removed from the circuit and connected a 1K resistor to the opamp input and the other end to ground.

I find the 6n1p SRPP has too much gain, so I am thinking of using a 12b4a triode instead with a grounded cathode topology, this should give me a gain of around 4. The Iout of the DAC is rated at 1V and after the I/V stage, the gain of 4 from the 12b4a should be more than enough. The 6n1p SRPP stage has a gain of 30+.

Good thing about this CD player is the optical and pickup mechanism is a Sony 240S which is still available for US$25 each, I will be buying two for spares.

I will also look for another used Denon CDP that uses the same DAC and mechanism as a spare.

The sound of this tubed Denon CDP is quite close to those more expensive tubed CD player.


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PostPosted: 15 Oct 2008, 19:56 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Excellent. You have encouraged me to have a go.

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PostPosted: 18 Oct 2008, 04:47 
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mwhouston wrote:
Excellent. You have encouraged me to have a go.

You will not regret it.

I will try to draw the schematics for the 6n1p SRPP.


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PostPosted: 30 Oct 2008, 09:17 
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Joined: 02 Sep 2008, 14:34
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Location: Rochester, NY
I too have been studying tubes into a CD player. I found the following site to be very helpful. He has modified over 100 players and even some DAC units. There is a tremendous amount of information on the site, including A Good Player List where modifications are not required. Well worth the look even if you are not inclined to modify.

http://www.lampizator.eu/

I am actively looking for a cd player to experiment on. My current thought was to use a PS 1 Model SCPH 1001 as a place to start.

Alan

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Denon POA 2200 | Bottlehead Quickie with PJCCS | Integra CDC 3.1 | SOTA Sapphire-RG301-Grado Gold 1 | Soundwave Soliloquy Series I


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PostPosted: 30 Oct 2008, 11:32 
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Looks like the Cambridge Audio Azur 540C is a SUPER buy. If only I had the cash. Then to the lampization :)
What a great site you found.
By the way that CDP is on ebay right now for 250US after shipping.
Ri

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PostPosted: 30 Oct 2008, 13:06 
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And then check out this page. Looks like this could be a fine tweak to a Denon or any other CDP.
http://www.lampizator.eu/LAMPIZATOR/LAM ... zator.html
Ri

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PostPosted: 13 Jan 2009, 11:50 
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Joined: 03 Aug 2008, 20:22
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Location: Denver, Colorado
Alex, Nice work. I have an older Onkyo DX-120 from 1987 and I am looking at a tube out mod. Just a couple questions about your build.

Did you go with a cathode follower or with a totem topology? Can you share a schematic?

Are you running AC or DC heaters?

This one uses a Yamaha YM3020 16bit dac and I am 99% sure it is Vout as there are two pc4570 dual opamps (one each channel) with first opamp in a unity gain and the second in some sort of bandpass config. I do not have a schematic, going old school board tracing with a flashlight.

Thanks

Rogers


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