Pearl Two

[bnorrish]

Here are my measurements against Wayne's.

 

[buzzforb]

Jfet idss are too high, robbing folded cascode net of available current? Just guessing though.

 

[6L6]

Which Jfets? The paralleled inputs or the Differential pair?

 

[bnorrish]

As note, the working channel measurements are very similar except I can adjust to 0 at the output.

 

[buzzforb]

Input Jfets, but I am sorta guessing and very new to folded designs. ZM will be along.

 

[buzzforb]

As note, the working channel measurements are very similar except I can adjust to 0 at the output.

Im out then

 

[bnorrish]

I am guessing Q5 is bad.

 

[buzzforb]

I am interested to see this answer. You have 1.5V across R6?

 

[bnorrish]

Close. 1.6-1.7 if remember correctly.

 

[buzzforb]

I have guess, but nothing more. As I said, i want to see the answer ont his one. It will be learning experience for me as well. sorry I couldnt help.

 

[Salas]

Close. 1.6-1.7 if remember correctly.

Try 1K trimmer connected as rheostat instead of R28 and trim for 1.5V across R6 first. Then see again with P1. Your LED is higher than 1.7V Vf most probably.
Q3 is squashed for Vce in your annotated schematic measurements. Try 15-22 Ohm R21-24 to give it breath. Your input quartet IDSS is probably higher than in the original.

 

[Salas]

Jfet idss are too high, robbing folded cascode net of available current? Just guessing though.

Buzz stop seeing folds everywhere. Its a classic telescopic. Therefore the local capacitance multiplier aid bcs of low PSRR.

 

[Wellerman]

To get Vc > Vb > Ve around Q3 you can experiment with lowering R10. Try 6k8 or 4k7. My quad probably also has higher Idss than the original, I had to lower R10 to 4k7.

 

[Salas]

That's adapting to another bias point on the fets curve and to another gm total than original though.

 

[Siberia]

Why not burn a cdr on your computer instead and replay it through your hifi's cdp maybe? Should be more standard to compare since those source files are wav even. Burn at relatively low write speed.

Burned and listened. I just knew what cartridge was on the first track. So a blind test. Almost.

The absolute price and performance winner after summing up all notes was a Dl103. I could also live with DL110, DL304 and Boboli on some material. Dynavector and Goldring 1012 were no slouch as well.

It actualy quite differs depending on material. Could it also be because of the pressings and cartridge suitability?

 

[Salas]

You saw why DL-103R is so popular. I have one, I own the Dyna X and the Goldring too. Used to have a DL-160, a Dyna 17R and a Stanton 881S also. Based on experience with that lot I would rather lean to its mostly a matter of arm and phono stage suitability than the pressings themselves.

 

[Siberia]

I'm assembling a new TT and when it's finished, I'm going to give a 103R a try on the RB300 arm. I think that means adding a SUT to my system too.

 

[buzzforb]

Buzz stop seeing folds everywhere. Its a classic telescopic. Therefore the local capacitance multiplier aid bcs of low PSRR.

After looking at Wayne's simplified version, I knew i was wrong, thats why i shut up. Now i have to go look up telescopic vs folded. I love being dumb.

 

[Salas]

Folding the cascode its used in low PSU voltage capability op amps mainly for saving yet another junction threshold across.

 

[Zen Mod]

and for few other things

which I don't know , at least not before first coffee

up to that task