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Old 12th January 2010, 08:34 PM   #11
Ivey is offline Ivey  United States
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Default Bypass Cap.

At the time of operational testing, it showed that it was not required. In the early days of LP cartridges, some outputs ran high and others low. And the impedance on other were not so good.

But yes, you could bypass it. Yet the 680 ohm and the 47uf/50 does double duty for you in that area.

Check it out please.

I will dia. it for you stand by.



Take Care.

Ivey
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Old 12th January 2010, 08:52 PM   #12
sonidos is offline sonidos  United States
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Hello Mr. Ivey! Thanks for the contribution. I apologize if you have answered this, but how clean of a psu do I need for your 2n2222a version? Is this circuit very sensitive to ripple? I certainly would like to try it.
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Old 12th January 2010, 09:12 PM   #13
Ivey is offline Ivey  United States
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Default Dia.

Look at this



ivey
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Old 12th January 2010, 09:19 PM   #14
sonidos is offline sonidos  United States
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Ahhhh, thank you! I have a LFD Mistral, which uses an 8 legged op amp DIP for gain. This circuit should be interesting and fun!
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Old 12th January 2010, 09:47 PM   #15
Ivey is offline Ivey  United States
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Default I have a good PSU for the 2N2222A

Allow me a few minutes to draw it up and I'll post it.

But here the scoop on it.

This circuit is good for low voltage and high current with very low ripple.

You can get everything you need at your local Mall Radio Shack.

I came across this circuit when I was building Class A's. It turned out to be pretty good. No dips when heavy current is called for.

This circuit may be used where high current is required, with a low ripple. The value of C2 smoothness , is about 48,000uf, base on the gain of Q1 and Q2 in their Darlington setting..

Take Care

Ivey
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Last edited by Ivey; 12th January 2010 at 09:50 PM. Reason: grammar
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Old 12th January 2010, 10:48 PM   #16
Ivey is offline Ivey  United States
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Default A PSU for 2N2222A

I used this circuit many a time. See if it is useful to you

Take Care

Ivey
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Old 12th January 2010, 10:59 PM   #17
mlloyd1 is offline mlloyd1  United States
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ivey,

thanks for your contributions.
does you circuit count on q2's base current leakage to bias the zener or is a resistor missing?

mlloyd1
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Old 12th January 2010, 11:22 PM   #18
sonidos is offline sonidos  United States
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Thanks again, Ivey. I'm starting out on the ground floor on these things, but is this not a cap multiplier? I had been wanting to try one and now I have a good excuse. It looks like I can find those parts w/o even breaking a sweat. Nice!!!
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Old 13th January 2010, 02:38 AM   #19
Ivey is offline Ivey  United States
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Default Mr MLLoyd1

No Sir, the 82k provides base bias for Q2, throught the feedback loop. The 680 ohm resistor, 1k resistor, the 47uf/50 provides reference for the zener.

the zener is used to provide reference to Q2's gain section, because you have two feedback loops to that section. The RIAA and the negative feedback loop of the 82k resistor.

If the reference voltage is lost, the unit could go into oscillation. When current demands are present.

I have played the phono amp without the zener, and it sounds muddy. With it, it is sweet and warm for a ss unit.

Take Care

Ivey
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Old 14th January 2010, 11:02 AM   #20
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If i understood correctly, i should use the power supply on the picture and that phono stage and that's it? It's writen that power supply output voltage is 35 VDC. But input voltage for phono is 30 VDC. What kind of transformator to use? Secondary winding of transformer should have 24 V probably? How strong transformer to use?

greetings
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