XDA-1 -- A symmetrical power amp utilizing LM4702

[Russ White]

Hey guys I do not have much time to write this up, but I thought I would share my latest design.

I have been toying with the LM4702 for quite some time, but I have since been very into super symmetry ala Nelson Pass and have worked out several SuSy designs.

Here is my latest:

It needs a little tweeking and has not yet been tested, but I am very confident about it as it is not much different from SuSy designs I have currently working.

Enjoy!

Cheers!
Russ

[reever]

Don't you ever sleep????

There is gonna be a few folks here drooling all over this one, based on the other active 4702 threads.....

Watching patiently myself

-reever

[zuus]

Hi Russ,

Well I have just read the data sheets and demo application sheet, this project could be truly quite special if it's as good as they say.

I imagine this would be one amp in particular where an oversized PSU could be a justifiable must to obtain the absolute best.

What power do you envisage aiming for, the opportunity in headroom overkill is very possible with this, aka naim style.

On a seperate note when you talk about sound quality do you consider all of:

1. Pace rhythm and timing
2. Staging
3. Emotional communication (female voice delicacy if you will).

Regards,

Mark

[lgreen]

Russ, are you full time DIY now or just 1000 times more productive than everyone else? No more Eagle? Looks very professional, I may have to give this one a try.

Can you get it up to 200WPC or is it more like 100WPC?

[Russ White]

Mark,

Hi and thanks.

I have not heard this amp yet so I have not idea how it will sound, but my first goal in designing things is accuracy. I think all the attributes you meantuned naturally follow that if they are captured in the source you are listening to.

I am aiming for 200+ watts into 8ohms.

You should easily be able to get that with this amp.

Also you could easily parallel darlingtons on the output stage and get much much more especially into 2-4ohm loads(in the 500W territory).

Cheers!
Russ

[Russ White]

Hi Reever and LGreen,

I swear I do this stuff in my sleep. Just seems to be a particular passion of mine lately. This amp has actually come to me during a particularly busy time for me as I move my household!

But in some ways the time I spend doing stuff like this really recharges my batteries, so I love it.


LGreen,

200WPC into 8ohms or so should be no problem with this amp. You could do ~30-75V rails, and parallel output devices for even more current.

P.S. I am still using eagle, just getting better at it.

Cheers!
Russ

[agent.5]

200WPC into 8ohms or so should be no problem with this amp. You could do ~30-75V rails, and parallel output devices for even more current.

If you do 60V rails, you can just use 2:1 isolation/control transformers, good and cheap on Ebay.

[billdinva]

What is a PD VOCM? Do you have a link to a datasheet or suitable part numbers? Thanks.

[Russ White]

PD is the power down PIN, which is not used.

OCM is output common mode, which ties to GND.

The datasheet is available from TI.

THS4131.

[rtarbell]

Howdy sir!

I just wanted to point out, that in your attached PDF document of your circuit, it looks like your emitter degeneration resistors for your output pairs are shorted out by your feedback.

==> What kind of servo opamp is your fully differential one? Is it from Texas Instruments?