Philips LHH2000's secret output (versus CD100 & others with TDA1540)

[flavio81]

Of interest to people with TDA1540 CD players!!

Hi,

As some of you already know, the Philips LHH2000 professional CD player is a highly valued beast; some reviewer said the sound was identical to a SACD player (?) and there is one currently at ebay for like $14000 dollars (!).

I am in possession of a humble Marantz CD63 (1982, 1st gen), which has the same circuitry than the Philips CD-100, and Magnavox FD-1000. Those players have a good reputation, but not cult status as the LHH200.

The thing is, they all use the same chips: SAA7030 (4x oversampler), 2x TDA1540 (14-bit dac)... so in theory they should sound the same. But of course there should be a difference between the LHH2000 and others.

So i dug out the schematics for both. The differences are in BLUE on the attached image.

I'm not an electronics engineer but as far as i can see, the main difference is a transformer XLR output; before the two opamps that make the XLR output there are no big differences except for (1) using two decoupling caps in non-polarized configuration [in LHH2000] instead of one, (2) more decoupling caps or higher-valued decoupling caps, (3) using one chip per opamp instead of 2-opamps-on-a-chip.

The TDA1540 on both schematics was wired practically the same. Again, the 1540 got higher value decouling caps,

I don't know where exactly the I/V conversion is done in both schematics, i'm assuming it's done at the transformer on the LHH2000 and done at the 3579 and 3580 resistors on the CD100.

So where is the reportedly big difference in sound?

[flavio81]

Note: The image is big, expand it so you can see the component numbers better.

Also, a question for the electronics experts: What kind of transformer can be used in that XLR output stage (number of windings, number of turns, in/out impedance etc...)?

[Steerpike]

Interesting!
I have a Grundig, same circuitry, but it is reported to sound better than the Philips, apparently becase of better circuit board layout, and better power supplies.
The LHH may have similar issues. It may have much to do with the quality of the capacitors, etc, and not so much their values.
The NE5534 as superficially the same as the NE5532-dual, but you can buy 'selected' 5534's that are picked for superior perfomance.

Output transformers like that are usually 1:1 or low ratios, designed for impedances of 600R. They may have been made by Studer - who collaborated strongly with Philips on matters CD. Generally transformers don't improve the sound, and the very costly ones (which professional types ARE) are intended to degrade the sound as little as possible. In Peru, I cannot help out, but RS-Components of the UK sell 600-600 audio transformers.

Another notable difference is the muting and deemphasis on the LHH are switched by FETS, on the CD100 by relays.

[le´flu]

Hi Steerpike,
which Grundig do you have?

Thanks and greetings Ulf

[Steerpike]

@Ulf

Originally Posted by le´flu

which Grundig do you have?

The CD7500 in silver.

http://web.eject.co.za/s8nspawn/hifi/ak/#cd7500

[poynton]

Originally Posted by flavio81

Of interest to people with TDA1540 CD players!!



I don't know where exactly the I/V conversion is done in both schematics, i'm assuming it's done at the transformer on the LHH2000 and done at the 3579 and 3580 resistors on the CD100.

So where is the reportedly big difference in sound?

The i/v is performed by the first opamp after the TDA1540 chip in both cases.

Andy

[flavio81]

Originally Posted by poynton

The i/v is performed by the first opamp after the TDA1540 chip in both cases.

Oh!! Hmm... so then the difference in audio is just better (& more) capacitors? Interesting. Note also that the resistors on the LHH2000 are precision resistors. For example "1.78K" instead of "1.8K" in the CD100.

Originally Posted by Steerpike

Interesting!
Generally transformers don't improve the sound, and the very costly ones (which professional types ARE) are intended to degrade the sound as little as possible.

Exactly, that's why i was wondering if there was some coloration induced by the transformer that could alter the sound in a nice way.

Originally Posted by Steerpike

Another notable difference is the muting and deemphasis on the LHH are switched by FETS, on the CD100 by relays.

Yes, but i don't think that would make such a big difference in the sound.

[poynton]

Originally Posted by Steerpike

Interesting!


Another notable difference is the muting and deemphasis on the LHH are switched by FETS, on the CD100 by relays.

Originally Posted by flavio81

Yes, but i don't think that would make such a big difference in the sound.

In most modern CD players, switching is usually done by transistors ( generally bipolar rather than fet )

One of the more popular upgrades is to remove these transistors as they are acknowledged to have a detrimental effect on the sound - leakage, capacitance etc..

Relay switching is usually the better option and indeed is another tweek - replace the muting transistors with relays.

I always remove the relays when I have to scrap an old CDP.



Andy

[Zoran]

IV is performed with 1st op amp,
transformer at the end (and last dual op) is just for single-end to ballanced line out...
in the middle is reconstruction filter,
which can be override, because I dubt the transformer have high bandwith up to 44.1K
so You already have a filter?
cheers

[flavio81]

Originally Posted by poynton

In most modern CD players, switching is usually done by transistors ( generally bipolar rather than fet )

One of the more popular upgrades is to remove these transistors as they are acknowledged to have a detrimental effect on the sound - leakage, capacitance etc..

Relay switching is usually the better option and indeed is another tweek - replace the muting transistors with relays.

I always remove the relays when I have to scrap an old CDP.

Exactly. But the CD-100 already uses relays, that's why i said i don't think using MOSFETs [like the LHH2000 does] would make a difference in sound.