WDPHONO3 3.18uS - World-Designs-Forum

Dave Cawley · #1 8th March 2011, 01:26 PM

Guys

As a "retained" engineer of WD and currently still the owner of this forum, I have been approving the new phonostage which is the WDPHONO3 but with the improved S-XL PCB. It and the PSU will be in stock in about 2-3 weeks, the kits are actually made!

I am working with Hi Fi World and whilst chatting to Noel Keywood yesterday, the subject of the additional 3.18uS time constant was mentioned. Noel said no as most MC cartridges have a response that actually does this all by itself. Hi Fi Critic published response curves of some phonostages that had 3.18uS but their measurement reverse RIAA network did not. And this looked odd.

So I am considering removing the 3.18uS. What do forum member think?

Regards

Dave

Richard · #2 8th March 2011, 01:47 PM

Leave it as 3.18 Dave as it rolls off of its own accord, and will not follow 3.18 fully at the top anyway, but it helps. Check for yourself

Very few have the gear to set the trimmer so do not supply it. Instead, in place of C9/10 supply 190pF for use with ECC83 and 220pF for use with 5751 valves.

John Caswell · #3 8th March 2011, 03:07 PM

Hi Dave, Richard et al,
Well I come down in the other camp. I think that the 3.18µS mod/trimmer is very useful even if a good many people cannot set it correctly.
I originally suggested it due to a good many people saying that "valve rolling" often gave dim or bright results.

John

Dave Cawley · #4 8th March 2011, 08:14 PM

Has anyone actually measure the impedance ratio or the step up voltage ratio of the WD MC transformers ?

Thanks

Dave

Richard · #5 8th March 2011, 09:03 PM

No. mine didn't last long enough

John Caswell · #6 9th March 2011, 09:27 AM

Hi all,
Will do it later today,

John

Dave Cawley · #7 9th March 2011, 09:40 AM

Thanks, unloaded of course.

Dave

pre65 · #8 9th March 2011, 09:48 AM

From a kit builders perspective Richards solution would seem better as very few of us have the skill, or equipment to adjust the pot properly.

If I remember from my Phono 3s build instructions, the advice was to set the pot in the central position.

Dave Cawley · #9 9th March 2011, 10:06 AM

Hi Philip

OK, but as a feature, would you want 3.18uS ?

Regards

Dave

pre65 · #10 9th March 2011, 10:13 AM

I suppose in all honesty, if it was proved to be a benefit to the performance-yes.

At my age I'm not sure if I could hear any supposed benefit, but I'd still want it.

The Pre 3 range was (is) a superb product in performance and styling and the only thing I would add is that a remote control volume option might make them much more attractive to a wider audience.