Simplistic NJFET RIAA

[Salas]

What it gives with 470R dummies?

 

[AndrewT]

Now is the time to find the worst case PSU voltage and to use the Mains Bulb Tester to prove your Transformer and PSU wiring is correct.

 

[nezbleu]

or you disconnect one amplifier and test the other one.

How is that relevant with dual transformers? The only thing the 2 channels share is the power cord (and presumably mains fuse and power switch).

 

[stajo]

What it gives with 470R dummies?

Approx 50,5 VDC

Btw Im in your hoods now. Just killed a z-foil. By heat while removal.

 

[Salas]

OK, beside the easy Z-kill which is grr@#%, while having 470R hooked as dummies try some RD value for 47-48VDC raw. It will do good to EMI and will keep calm VDC during a high mains plateau if ever. Bring up the Duncan PSU software and use 100mA as end load to gauge the about RD value. Resides between bridge and filter cap. But use crocks to confirm before installing. 2W-3W-5W should fit and suffice.

 

[stajo]

I trialed and errored the trafo resistance in PSUD until I got matching figures in pic one. 10 ohm seems to fit in pic 2.

 

[Salas]

Sounds like a logical RD value. Try in practice if you got any proper parts.

 

[stajo]

My 10ers was to big so I tried a 12R 6W. It read 1,3 v over it and it read 47,5 at the dummy!?! DVM reading ripple strange? Something there will be ok anyways. Thanks. Ill tweak it from there when its live.

 

[Salas]

Its the charging cycle dynamics and averages. There should be 100-200mV pk-pk ripple that you can see across the dummies on the scope too. Its named raw DC for a reason. But at the Rail+ after the integrated reg you should see a continuous line.

 

[stajo]

I was not worried about the ripple, rather confused about that the drop over the RD was 1,3 VDC when it dropped some 3 volts in total. But Im with you now, the C doesnt get the same camelbacks as without the RD. PSUD says 3,86 V pk-pk ripple over RD. 1,76 RMS.

Edit: You said dummies, I thought RD. My fault.

 

[Salas]

With just link, ripple is pointy zigzag but with RD its rounding off. You can see all that live on the scope if you will probe around the raw DC board when running on dummies even.

 

[Salas]

I was not worried about the ripple, rather confused about that the drop over the RD was 1,3 VDC when it dropped some 3 volts in total. But Im with you now, the C doesnt get the same camelbacks as without the RD. PSUD says 3,86 V pk-pk ripple over RD. 1,76 RMS.

Edit: You said dummies, I thought RD. My fault.

1.364 RMS. Given the ambiguity on real internal resistance of your Tx, I think that you did pretty well on theory vs practice results.

 

[stajo]

PSUD shows only slightly broader tops of the camelbacks with RD. Maybe more visible on scope. Kiddo goodnight time now tho. Later maybe.

 

[stajo]

1.364 RMS. Given the ambiguity on real internal resistance of your Tx, I think that you did pretty well on theory vs practice results.

Yes PSUD is remarcable if just inserting the right values. Trafo resistance is often the hardest imo, and affects big time.

 

[Salas]

PSUD shows only slightly broader tops of the camelbacks with RD. Maybe more visible on scope. Kiddo goodnight time now tho. Later maybe.

When able probe across the dummies on AC coupling and look on the scope with a crock bypassing RD and without.

 

[stajo]

He didnt want to go to bed. Here u go

 

[Salas]

One is acute the other is rounded off and smaller. There it cuts some charging cycle EMI too.

 

[stajo]

Maybe some nF to ground before RD wouldnt hurt either.

 

[Salas]

Some guys put across the secondary. Further patches and filters up to you, as they have various subjective impact and there are "schools". Listen in simple mode first to have a base. No pressing issues.

 

[stajo]

Smaller values looked peculiar but at 1 uF it starts looking round and nice. Did you have time to look at http://www.diyaudio.com/forums/analogue-source/129126-simplistic-njfet-riaa-1316.html#post4019478?