Puresound P10 RIAA

Status
Not open for further replies.
Jump to Latest
#41
With the new data, the initial circuit seems quite good but IMO the most important part is the 500.5Hz pole (zero).

Disregard all previous recomendations.

As your real parts values are not exactly as Puresound schematic I suggest only:

R17 38K9 CADDOCK TF020R
Should be R17 = 38k9 // 2M62 = 38331r
C7 .006 paralleled .0022 = 8,2nF
Should be C7 = 6nF // 2.2nF // 0.1nF = 8.3nF
This way you preserve the 500.5 pole because 38331 x 0.0083 = 318.15 (almost 318)

I would also place a 7M paralelled to R1 but as SY noted, this is dependent of the tube used and also on the system... It should be ear tuned.

Lowering this R1 resistor (bypassing it with a larger one) produces a lift in the power zone.
 
#45
It won't be less noise- the lower resistor also reduces gain. No free lunch.

One could design a preamp from scratch to run off 150V, but if you're going to build one that needs 240V, give it 240V. It's not like a raw supply is that difficult or expensive.
 
#46
Hi Merlin

If you must use 150v PSU, maybe you could build this one.

It is well tuned and very similar to the Puresound.

Anyway, if you choose to start from scratch, you must consider the Itch.

I heard fran´s unit and even in the internet it sounds wonderfull.
 

Attachments

  • PH102.gif
    PH102.gif
    49.2 KB · Views: 317
#52
merlin el mago said:
Just received Guy answer:

"The internal resistance of an 83 is about 70Kohm which is in parallel with the 120K load resistor giving 44Kohm. This is added to the 330K and the result works in parallel with the 1M0 to ground giving 272K which is the net value used in the Eq calculation. The Miller capacitance of the 88 is 40pF which must be added to the 2n2 and 560pF to get the eq calculation spot on.

rgs

Guy"
Click to expand...
Hi Merlin

Please forward my thanks to Guy

I used his input to finalize my riaa simulator.

Guy´s values confirm mine in all respects. 🙂
 
#53
RCruz said:
With the new data, the initial circuit seems quite good but IMO the most important part is the 500.5Hz pole (zero).

Disregard all previous recomendations.

As your real parts values are not exactly as Puresound schematic I suggest only:

R17 38K9 CADDOCK TF020R
Should be R17 = 38k9 // 2M62 = 38331r
C7 .006 paralleled .0022 = 8,2nF
Should be C7 = 6nF // 2.2nF // 0.1nF = 8.3nF
This way you preserve the 500.5 pole because 38331 x 0.0083 = 318.15 (almost 318)

I would also place a 7M paralelled to R1 but as SY noted, this is dependent of the tube used and also on the system... It should be ear tuned.

Lowering this R1 resistor (bypassing it with a larger one) produces a lift in the power zone.
Click to expand...

RCruz said:
Hi Merlin

Please forward my thanks to Guy

I used his input to finalize my riaa simulator.

Guy´s values confirm mine in all respects. 🙂
Click to expand...

I forwarded your thanks to Mr. Guy, I'm a little bit confused:

C7 8.2nF or 8.3nF?

C8+C9 2.760pF or 2.2806pF or 2.986pF? (all + 40pF Miller)

R17 = 38k9 // 2M62 = 38331r

R1 = 329K // 1M optional fine ear tuned
 
#56
Did you decide about the PSU ?

For this design you should really use the 220v 260v otherwise you must recalculate R22 / R28 and R2 / R3 ratios.

These ratios work with the spec voltages and define the gain in both stages.
 
Status
Not open for further replies.
Top Bottom