TDA 1540 - LESS is MORE

[phimor]

and nothing succeeds like exess...

Having owned a Meridian MCD for some time has given me considerable respect for the potential sound quality of the TDA 1540. I have consistently found I was ‘enjoying’ the music more with the MCD than with my Meridian 206 DS. It was not as detailed, but certainly more fun.

I also successfully repaired a Philips CD 200, and through that experience I was impressed by the simplicity of the electronics and the reasonably high specification of these first generation machines:

1- relays rather than transistors for muting
2- regulated supply for ALL voltage rails
3- Two mono DACs, unlike the ‘time share’ arrangement by BB
4- Solid metal chassis (6 to 8Kg’s worth)
5- Exquisite CDM0 or CDM1 transport
6- Plays CD-R

Which struck me as a great base for modding.


The sound of the MCD is much better than the CD200, yet the electronics are the same…except for the I/V stage, and a few bigger caps. So having a taste of what the TDA could do, I thought; what’s the best that can reasonably expected from these old machines.

The idea was to mod a CD200 to achieve best performance, but the mods needed to be kept in proportion with the cost/value of the original. That is: quite modest.

In the end I ended up with a player that is better than either of my Meridians (Yes, better – as accurate and detailed than the 206, yet retaining the musicality of the CDM). Best of both…

This is what I did:

Replaced all electrolytic capacitors. This is for reliability more than improvement.
Increased electrolylic’s on the op amp power rails to 460uf.
Added a 200nf cap between the +ve and –ve rails on each op amp.

Then I started op amp ‘rolling’…;-)

OPA 2134 - brighter and more detail than the stock ne5532, some what similar to the twin ne5534 of the MCD. However the bass is not as nice, being a bit too obvious.

OPA 2604 – I could not tell the difference with the 2134, except it’s more expensive.

OPA2227 – clear and detailed, without an overwhelming base, quite good..but..

LM6172, this is a great upgrade. Very good detail, yet smooth, plenty of bass without ever sounding ‘bloated’. Really revealing of subtle variations in timbre, voice. Only trouble you need to be careful with the de-coupling. This is the main reason I added the 200nf between power rails. Also, on some of the variants of the Philips players, the 22nf on the left channel –ve rail is missing!
This is without a doubt the ‘value’ upgrade for these players.

Then I tried to see just how good it get and ended up with:

AD 843 with a BUF 634 on a browndog adaptor. This is the bee’s knees. I had to re-audition most of my disc collection, as the articulation of the instrument was such I could hear things I never heard before. The subtle decays of cymbals, people talking in the background, stuff like that and more. The TDA is capable of great things.

However this is not really cost effective, at roughly AU$45 a side, compared to the $12 for the LM6172 that gives you at least 90% of the same job.

Anyway, here is some food for thought for fans of these old players..

Cheers

Philippe

[phimor]

Excess,

Can the moderators edit the title please......

thanks

Philippe

[poynton]

Excellent description of mods.

I have one of these.

I may now start to play !

Andy

[mrskinny]

Here's something else to try- the picture below shows a portion of the decoder board from a CD204. The large capacitor that is circled has a stock value of 22uf. I replaced mine with a 1000uf low esr type (what I had on hand), though I'm sure the larger value shown in the photo wouldn't hurt. This capacitor is for the power supply to the crystal, and gives a big improvement in the overall sound quality of the player- I'd say as much as changing the op-amps.

[robo]

I like TDA1540D more than TDA1541AS1

[phimor]

Here is my CD200 "convertible".

[phimor]

Thanks Andy and Mrskinny for the words of encouragement.

I'll try the 'fat' cap on the saa7030.


This also shows one of the other mods I forgot to mention:

The rubber band around the x-tal, and the 'wire wrap' ic sockets, to get the clearance for the browndog..

Cheers

Philippe

[robo]

to use TDA1540 with SAA7210?

thanks .

robo

[pinkmouse]

Originally posted by phimor
Can the moderators edit the title please...

Done. I would be interested in any advice on tweaking this chip as I have a Marantz CD45 that uses two of them in my bits pile.

[poynton]

Originally posted by pinkmouse


Done. I would be interested in any advice on tweaking this chip as I have a Marantz CD45 that uses two of them in my bits pile.

Hi.

There is the thread below which deals with the CD104.
It has some ideas for modding the earlier Philips etc. players with the TDA1540.

Philips CD104 tweaks

Andy