Paradise Builders

[Simon1972]

Or, float the input and output sockets on the paradise, so signal gnd has no chassis bond. And run the chassis back to mains 0v via a DDRC.

If there's continuity between gyrodeck chassis and tonearm you don't need another gnd just that 3rd wire in the arm.

 

[metallicus69]

I tried to search without success through all the threads. Is it possible to decrease the gain of this preamplifier? I use a cartridge with 0,5mV nominal and the output is still undistorted, but the value is quite high. I cannot use the whole range of the volume control of the next stage. Thanks in advance!

 

[as_audio]

It is possible to reply if we know which schematic you use.

 

[metallicus69]

Thanks! I use the first schematic, I built the preamplifier in 2013, without the Calvin buffer

 

[as_audio]

I can not help you without a link or picture of the schematic.

 

[Simon1972]

The circuit and components have remained unchanged since rev1

 

[as_audio]

I will not do the work of this gentleman and search myself.

 

[metallicus69]

Fair enough. Post #13 documentation
This is the schematic I used.

 

[as_audio]

With this schematic you can not change the gain easily.
RIAA network is the load and determines gain.

 

[metallicus69]

So let's say I want to reduce the gain by 3 times, I would then need to reduce the network impedance by 3, keeping the RxC product the same:
73.5kΩ will become 24.5kΩ; 9.1kΩ + 33.3nF will become 3.0kΩ + 11.1nF and 220Ω + 11nF will become 73Ω + 3.7nF
Is this approach correct or I am completely wrong?

 

[as_audio]

Yes, scale all values by a factor of three (this will be about 10 dB), but this means increasing the capacitances accordingly.

 

[metallicus69]

Yes, you are absolutely right, to preserve the time constants I need to increase the capacitors, not decrease them (my bad)
So

• branch 2: to keep 9.1k⋅33.3n=3.03k⋅C ⇒ C=100nF
• branch 3: 220⋅11n=73.3⋅C ⇒ C=33nF
  I should try these values

 

[as_audio]

You do not need all these parallel elements if you can find convenient standard values.

 

[Simon1972]

Just have TX components make you two pairs of naked foils at the exact values, it'll cost you $80 but no approximation or paralleling.

 

[hesener]

Back in the old days we had a (small) group buy of VHV teflon-copper capacitors in just the right values for Paradise, those came in at $280 if I remember correctly 😀

(was it worth it? sure 😀)

 

[Simon1972]

But are they really any better than big fat styrene caps? 😉

 

[hesener]

It ain't over til the fat cap sings 😀

My own, limited, biased, totally personal and subjective opinion on this is that the thicker the dielectric, and less Absorption, the better - but the longer it takes to break in.... have you tried PPS2 caps?