Arcam Alpha 5 upgrade help

[AndrewGM]

Here's a collection of Gems I could find written by the people who know about Alpha 5 CD players. :

cut the track between Pins 2 and 4 of the TDA1541a chip - WHY ?

SAA 7220 removed altogether then connect 1 to 18 2 to 16 3 to 15 and a wire link between pins 9 and 11 - Is this OK and does this complete NON OS conversion - is there anything else that needs doing ?.


I use Black gate n series non polar for the output couplers and take the output direct from the output of the opamps to the phono sockets bypassing all those nasty muting transistors etc - Can I really do this without bypass caps and is it safe this way ?


I think it is still active when using the isolate pins 1 23 of DAC and linking 123 of filter to it.......Digital out socket - Is it still active or not ?

de-emphasis cd mode is hardly used on modern cd format, why not remove the transistors that perform this function - no one actually answered this point and wonder if this is OK to do ?

The opamp feedback resistor type has a big influence on the sound, it might be an idea to start here. Try 0.5W carbon from farnell or Audio Note tantalums. You can solder them directly onto the opamp pins to preserve the PCB tracks - The man who suggested this did not mention which resistors they are, not helpful to learners like me - does he mean R11 ?
Which pins of the op amp does he mean please ?

Any explanation welcome and indeed any useful advice too.
I've trawled this site and can only find these items on this subject.

Thanks

Andrew

[poynton]

Originally Posted by AndrewGM

cut the track between Pins 2 and 4 of the TDA1541a chip - WHY ?

Read up on the difference between the TDA1541 and TDA1541A. It's to do with the chip clocking.

SAA 7220 removed altogether then connect 1 to 18 2 to 16 3 to 15 and a wire link between pins 9 and 11 - Is this OK and does this complete NON OS conversion - is there anything else that needs doing ?.

Yes. There is a lot written on Non-OS conversions for the TDA1541A. diagrams etc.

I use Black gate n series non polar for the output couplers and take the output direct from the output of the opamps to the phono sockets bypassing all those nasty muting transistors etc - Can I really do this without bypass caps and is it safe this way ?

Absolutely safe. you may have some small clicks between tracks.

I think it is still active when using the isolate pins 1 23 of DAC and linking 123 of filter to it.......Digital out socket - Is it still active or not ?

The digital filter does not work in NOS mode so neither does the digital out.

de-emphasis cd mode is hardly used on modern cd format, why not remove the transistors that perform this function - no one actually answered this point and wonder if this is OK to do ?

Yes. its OK to do.

The opamp feedback resistor type has a big influence on the sound, it might be an idea to start here. Try 0.5W carbon from farnell or Audio Note tantalums. You can solder them directly onto the opamp pins to preserve the PCB tracks - The man who suggested this did not mention which resistors they are, not helpful to learners like me - does he mean R11 ?
Which pins of the op amp does he mean please ?

There are other things eg power supply which would have a greater effect than the feedback resistors . I would not bother.


Andy


.

[AndrewGM]

Andy Hi

Hallelulah - a response - really grateful !

I was beginning to think I'd written another boring post - it happens all the time.
I have absolutely no luck whether on the chip amps section or this one.
I'm so disillusioned with this place.
So many people sign up to this, post things and then get no replies.
Then you get the members who think they know but who give unintelligable answers.
It's not for learners at all.
Rant over

Thanks for reading and for the tips.

Point taken, more reading and trawling to do.
I'll do the op amp direct mod and ignore any clicks - it's a cleaner route, I like that.
Digi out - understood - I won't need off board dac if I do it right first time.
De- emphasis - great thank you.
Feedback resistors - that's what I need - straight talking.

How very refreshing - just what I wanted

Many thanks

Andrew

[Chivvyp]

Originally Posted by poynton

Absolutely safe. you may have some small clicks between tracks.

Performing the NOS mod on the SAA7220 and removing the muting transistors brings its own problems in the form of pops and clicks when idle and also track noise whilst "next-ing" or "previous-ing" or pausing. The answer here is to connect pin 23 (MUSB) of the SAA7220 to pin 18 (MUTE) of the SAA7310. This restores the player to its previous set-up, but mutes the player in the decoder rather than discretely using the transistors.

Regards

Pete

[AndrewGM]

Ah great -thank you Chiivvyp.

And that means ( I think ) connecting pin 23 of the SAA7220 to the 7310 on the underside of the main board with a wire or is there a better way ?

I would prefer to use your suggestion to eliminate the click and pops
in some way.

Thanks for your time on this

Andrew

[Chivvyp]

Yes, just solder a wire link between the two.

Pete

[amc184]

The Arcam Alpha 5 is a nice player, I'd get one if it came up for sale at the right price. I've got an Alpha and an Alpha Plus, which are a very similar circuit, but with totally different PCBs.

I've trawled this site and can only find these items on this subject.

This player is very similar to many others that use the same decoder, digital filter and DAC as this one, so you should broaden your search. Many modifications that have been done to players like the Philips CD650 and Marantz CD40 / CD50 / CD60 will apply to your Arcam.

A few things I would look into:

- Installing a DEM reclocking circuit
- Installing a low jitter clock
- Replacing the output stage (discrete solid state or tubes), or improving the one it already has (better opamps, coupling capacitors, decoupling capacitors etc.)

My only reservation about the 'NOS' mod (removing the SAA7220 digital filter) is that it will drastically increase the amount of high frequency noise the player output. You may not hear this directly, but you may cause problems in components downstream. Some amps will burn a heap of power (even to the point of destruction in very rare cases) trying as hard as they can to amplify that noise. Slew rate limiting sounds nasty.

In my opinion, a lot of the benefits of the above mod comes from removing the SAA7220 from the +5V power supply rail. It's a power hungry IC, and tends to propagate a lot of noise back into the power supply, to the detriment of the rest of the player. Consider building it it's own regulator circuit and replacing its decoupling capacitor with an ultra low impedance type (like an OS-CON).

Food for thought.

[amc184]

Oh, and something else I remembered:

I use Black gate n series non polar for the output couplers and take the output direct from the output of the opamps to the phono sockets bypassing all those nasty muting transistors etc - Can I really do this without bypass caps and is it safe this way ?

I'd leave the resistors between the opamp's output and the output connectors in place (R13 and R113). These isolate the opamp from output capacitance, without them the opamps could oscillate if you connect a pair of very capacitive interconnects. Do try removing the output shorting transistors though (Q2 and Q102), but be aware that you probably get a turn on crack and a turn off thump (that's what the transistors are there to mask).

[AndrewGM]

Many thanks

I'll do the Q2 and Q102 plus the e emphasis mod and install the Audio GD discrete output stages that I have lying around.
Do the clock and investigate the power supplies.
Anyone know where the clock attaches and which parts are to come out ?

I have an old Alpha CD player and absolutely love it - problem is the now very noisy transformer which drives me nuts.
I was told to put new cable ties around it to tighten up the wafers but it didn't work. (the small traffo to the DAC board)

Hey guys, thanks for helping me out

Plenty to be thinking about

Regards

Andrew

[Chivvyp]

Originally Posted by AndrewGM

I have an old Alpha CD player and absolutely love it - problem is the now very noisy transformer which drives me nuts.
I was told to put new cable ties around it to tighten up the wafers but it didn't work. (the small traffo to the DAC board)

I would have thought it was easy to replace this transformer with a new one or similar. It's only a single +- voltage isn't it?

Pete