Discrete output stage for Sony c222?

[rfbrw]

Originally posted by Extreme_Boky

Try reading again - it'll come to'ya...

To quote the graffiti on a wall in New Zealand
" you can always tell an Australian, but you can't tell'em much"

[Extreme_Boky]

????I'm Serbian!!!!

[rfbrw]

But you've gone native

[Sheldon]

Originally posted by Extreme_Boky
Transformers do I to V conversion, natural aliasing filtration, gain and impedance matching, but I question a good impedance matching!!!. Check this site re transformers:
http://www.lundahl.se/

I like higher voltages because i prefer true-to-life sound, a bit like studio monitoring. Higher voltages almost always produce higher slew rates / faster settling times.

However, lower voltages give that warm sound that many people prefer.... not for me.

Power supply is 60 - 70% of global sound quality, yet it's quite often neglected. Try good quality transformer, soft switching fast recovery diodes (RURP3060), Black Gates FK for main storage + storage after voltage regulators. I do not like to bypass these caps with lower value (0.1uF) film types. High frequency decoupling should be done only as close to ICs (transistors) as possible and for this I use 0.1uF / 50V NX Black Gates, again, without any caps in parallel. This is possible due to very high quality of both of these capacitors’ types. Experiment a lot and see for yourself....

AD 8066 is outstanding amplifier and it should work no problems with + and -10V DC. I use them as I to V converters in dual differential PCM1704 configuration, with + and - 12V DC with addition of little heat sinks on top of them, to keep input bias current / conversion error to min. They tend to run hot as you increase voltage to their maximum of 24V DC.

You can try discrete anti aliasing (analogue) filters and see if you like them....

Many people report very good results with simple resistor as I/V converter and discrete amplification with passive filtration, or transformers.

Cheers,
Extreme_Boky

Thanks for taking the time to respond. On the transformers, I was curious if they were sometimes used in applications like this, not for impedence matching, but for coupling instead.

I have some questions about the filtering. It would be helpful if I were to describe what is present. I haven't yet mastered any of the schematic drawing programs, so here is a description of the present analog filter system:

In order, after the DAC output to the non-inverting input: 47uf, 10k to ground, 6.8k, 680p to ground, 5.1k, 330p bypassing op-amp, 5.1k, 47pf to ground, then to the input.

From the output: 10K to inverting (with 6.2k to ground for the feedback loop), 47uf (bypassed with 15n), then two 330ohm and one 100 ohm resistors to the output, with muting transistors to ground between the resistors.

Given that background, if I make a discreet stage, any recommendations on filtering? I would probably leave the present output intact and make separate outputs for the new stage.


Cheers and Merry Christmas to some, Happy Holidays to all,

Sheldon

[Extreme_Boky]

From what I could see, it looks like that first stage is a filter and second low gain amplifier. There are many things I don't like about this, mainly two coupling caps (47uF), 680pF cap loading DAC output to ground, and muting. This is very simple way of getting rid of high frequency rubbish in "one go".

There are many ways of improving the analogue stage, which I described above in my replies. SONY likes to implement high over sampling, but uses pretty good digital filters as well. One of Lundhal transformers (with an addition of AD8066 as a buffer, maybe...) might work fine with your CD player.

As I mentioned before, you have to try as many options as you can get your hands on, and then decide... Good analogue CRO is very handy when experimenting with different options.

Another thing: AD8066 might be too fast and accurate for some systems. If you find this was true, try OP275.

Extreme_Boky

[Sheldon]

Thanks,

On the specifics side, any examples of filter arrangements/values that anyone can site as examples. I'll dig around the site and the web, but if you've got one you can point to and help direct my search, I'd much appreciate it. This is all new ground for me.

Sheldon

[Extreme_Boky]

Do a search on web:
second order analogue filters
first order analogue filters
butterworth low pass filters
chebyshev low pass filters
bassel low pass filters
or
go to a local library - there are full of info on analogue filters.
Cheers,
Extreme_Boky

[Sheldon]

Originally posted by Extreme_Boky
Do a search on web:
second order analogue filters
first order analogue filters
butterworth low pass filters
chebyshev low pass filters
bassel low pass filters
or
go to a local library - there are full of info on analogue filters.
Cheers,
Extreme_Boky

Thanks, I know the general filter stuff and have cook bood articles on filter design. From those , I can concoct a basic filter and buffer. What I don't know is the noise profile from this type of output. So I apologise for making the question too general. Maybe I should have framed the it this way; for this specific application, what is a typical filter type, order and corner frequency for a good starting point? Or, what are the frequencies to worry about here, and at what level do they occur? I'd like the LP filter to have as high a corner frequency as practicable, and as low in order as practicable, but still good enough to do the job. I can take a guess or I could base it on what Sony has in place. Maybe someone has a better recommendation, though? I don't mind looking on my own, but if someone has a good example or a good site to start with, even better.


Sheldon