Playstation as CD-player

[Mick_F]

I dont think this is a problem of the line condition so a conditioner will not help. Looks as if the SMPS is kaputt.

Mick

[DustinEwan]

Dang, I can't even borrow the psu from my other (newer) playstation either

It's strange that it does that instantly though, because it's the first thing in the circuit. Oh well, I guess I won't know all the workings of these until I actually GRADUATE with my EE degree

[pozo1992]

Hi gents,

So far I`ve modified my PSX by shorting the coupling caps of the AV output and feeding it directly into an AC coupled preamp. Although I enjoy the sound of this solution there are two major drawbacks:
DC output bias causing “pops” and fairly high output impedance due to direct feed of DAC outputs to the preamp.
To overcome these, I decided to use below shown JFET source follower stage between the DAC`s outputs and the muting circuit. I have used the RCA outputs and kept the muting circuit, but removed the “strange little thing” (which is a common mode choke from MURATA) and also the SMD ferrite beads. Apart from the cap at the output of the muting circuit I have removed all other caps connected between the signal and ground in order to avoid further high frequency attenuation.
This “buffer – solution” leaves me with only one coupling cap per channel as I can use the DAC`s DC level for biasing the JFETs. The JFETs provide a high impedance seen by the DAC which is favourable. thus the DAC and the output are nicely decoupled.
You can of course use other JFETs than 2SK170, but you may need to adjust the circuit slightly.
Listening tests are ongoing so I´ll keep you informed.

[Mick_F]

Good idea.

Where do you get the 5V from?

Mick

[pozo1992]

Hi Mick,

the +5V is the supply of the opamp (pin 8).

Jürgen

[Mick_F]

I am looking forward to hear about your listening experience!

Mick

[pozo1992]

Hi Mick,

it will be quite exiting for me too. I have already done this kind of modifikation on a Pioneer DVD player (DV-343) and the result is very good, indeed better than my so far playstation. Now it will be fun to see if the playstation can pass my favorite again.
By the way: I took my idea from the decware web-site where Mr. Decker is modifying a DV-343 with a tube cathode follower stage. For me the tube stuff was to much effort, so I decided to go for the JFET.

So long,
Jürgen

[DragonMaster]

The 5v is coming from the 7805 on the motherboard, which is fed by the SMPS's 7.?V line

[Mick_F]

Just a side note, which may be interesting for those of you, who suffer from the low output voltage of the PS1:

The NJM2100 opamp is used with unity gain in the stock form, but it can be used with higher gain. Replacing the feedback R from 18k to 27k will increase the output signal voltage by about 50%. E.g. at 1 kHz there is an increase from 1.1V to 1.6V. The signal is still undistorted and there is no clipping.

Cheers,
Mick

[bzfcocon]

Originally posted by Mick_F
Just a side note, which may be interesting for those of you, who suffer from the low output voltage of the PS1:

T

But has anyone checked the voltage on the VREFH pin , that is supposed to control the output of the DAC ? I would have, but I couldn't get the datasheet for my DAC. I have a AKM DAC and only a datasheet for AK4309, which has fewer pins. So I couldn'T figure out which pin it is.

My supposition is that the low output comes from putting this pin to a lower voltage.