Opinions on Redd47 P2P Layout please

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sonolink

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Feb 15, 2010
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Location
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So I've been drawing this Redd47 P2P Layout based on the Hinson schem and Guitarmaker's drawings and would appreciate the more experienced EEs and builders to take a peak at it please :)

I've added an input to Hinson's schem for phantom, LF cut and Pad based on a schem I found time ago that I merged with Volker's slow phantom start schem. There are 4 zeners that I'm not sure I really need but left them in. Maybe someone can advise on that?

The PSU I intend to use is the schem attached on the next post. It's a universal Tube PSU sold by Diy-Tubes.com (http://diy-tubes.com/index.php?route=product/product&product_id=119).

If it's noisy or anything I'll build the one on the Hinson schem.
I will probably implement a stepped gain switch discussed on another thread when I get this baby rolling. For now I would really appreciate any opinions, advice, feedback, or mistakes spotted.

Thanks a lot for your help and time :)
Sono
 
Rochey said:
aren't you trying to use an NPN as a high side switch there?

Hi Dafydd :)
I'm not sure I understand what "high side switch" means.
What I did was to use Volker's Mic In/Out circuit to provide a slow start phantom to my mic input. This is Volker's circuit:
http://www.silentarts.de/Techtalk-Laden/MIO_rev01-Doku.pdf

I hope he can chime in...

 
Andy Peters said:
T1, the TIP121, is being used as pass element, not a switch.

I might be wrong but I think Dafydd was talking about the BC550 in Volker's slow start phantom circuit, Andy
Cheers
Sono

 
sonolink said:
The PSU I intend to use is the schem attached on the next post. It's a universal Tube PSU sold by Diy-Tubes.com (http://diy-tubes.com/index.php?route=product/product&product_id=119).
Do you know that, the way it's connected, the heaters voltage has 12Vac superimposed? So the advantage of DC heaters is neutralized... that is, assuming the heaters 0v is separate from the phantom's 0v.
In case they were connected, you'd just blow up the xfmr.
Check on the original schemo how the heaters and phantom circuits use two separate windings.
Now I find veeeery strange the jumper JP2, that allows to inject 12Vac into the regulator, without prior rectification...
 
Excellent  :)

Concerning the PSU, the schem I on my 2nd post IS the original one downloaded from Tubes-Diy.com.
I don't understand what you mean by "superimposed". I had the impression JP1 was there to select 6.3 OR 12.6vac but I'm not an EE, just a self thought enthusiast tube amp builder and can't really deeply understand schemos the way you or many others do here. So after reading your post I tried to do my deciphering homework and my guess is that C1-C4 are part of a rectifier and thus there should be DC instead of AC at the terminals marked 6.3/12.6. If so how can there be 12VAC superimposed on the 6vdc heaters voltage? Could you please explain what you meant? I'm a bit confused but eager to learn more :)

Regarding the secondary windings, from the PSU schem it looks like 0v is the same for both phantom and heaters  ???
If that's going to blow any of my transformers I'm a bit puzzled since this is a product sold on a webpage (belonging to a forum member btw) so I assumed it would work ok without harming my components. My worry was if it would be noisy rather than dangerous :)
So you would advise me to go a different route PSU wise? If so, any suggestions on any circuit? The reason I didn't follow Hinson's idea was obviously to try to spare some money but maybe it's worth not sparing money on that one after all...

I found JP2 strange too but I didn't bother with it much since I would use only 48v. Maybe some test point?

On the other hand, Rochey has rised an interesting point regarding using a BC550 for the slow start phantom. Any comments on that?

Thanks a lot for your input and help Abbey :)
Cheers
Sono
 
At some point the three 0V will be connected together. The heater 0V has to be connected to HT 0V. THe phantom 0V would normally be connected to chassis but then at some point the chassis will be connected to the safety earth and the HT 0V will need to be connected to the same point.

The shorting together of the phantom and heater 0V will cause a problem.

Cheers

Ian
 
The input tube's plate resistor (100k) should be connected to B2 (after 51k resistor).
Capacitor 220n should be 22n.
 
Moamps thanks for spotting those mistakes :)
Cap value corrected

moamps said:
The input tube's plate resistor (100k) should be connected to B2 (after 51k resistor).
Sorry I don't understand what you mean with "B2"

 
ruffrecords said:
At some point the three 0V will be connected together. The heater 0V has to be connected to HT 0V. THe phantom 0V would normally be connected to chassis but then at some point the chassis will be connected to the safety earth and the HT 0V will need to be connected to the same point.
The shorting together of the phantom and heater 0V will cause a problem.

Cheers
Ian

Ian, thanks for chiming in :)
Ok so if this PSU is no good any recommendation/suggestion for another one?
Thanks a lot
Cheers
Sono
 

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