Angelo power supply  is build using a nice and interesting tube: PY82.
 I happened to have a bunch for very little money so I used it extensively in this project.
Beside its price, there's another  nice thing about this tube: it's indirected heated and so can be used to build Graetz bridges very easily.

This is quite interesting feature:  if you're ready to accept a little reduction in plate voltage,  you can substitute solid rectifiers without changing power supply  trasformers and experiment the sonic difference between SS and Vacuum tubes rectifier.
You have to consider that Voltage drop can be 20volts or more (depending on the current you're dealing with), instead of the 0,7V of a SS diode so bias point can be noticeabliy  different.

you  also have to build a PS for the heater of PY82, but you are already guessing to try this,  this not a problem.  ;)..
 
 

• PY82's Maximum Ratings

1)Try to guess how much your circuit needs.
Remeber that PY82 can bear currents not exceeding  150ma-180ma , but to keep voltage drop low  I suggest you to keep  under 100ma.  If you're planning higher currents put two graetz bridges  in parallel. ( Or better build two PS!)

2)There's also a costraint in the value of the first cap: 70-100uf.  Actually this is not a problem as you can pospone the microfarads exceeding this value after the first coil. So check the caps in your circuit.

3)The last costrain is about rectified voltage: theoretically you couldn't go beyond 250V DC .  But looking at the specs, this tube can bear 700V reverse peak. So in many times I've reached and execedeed 300V DC without any problem. If you go well beyond 250V consider to put a 100-200ohm resistor in series with AC leads before  the graetz bridge.

• PY82 spice model

* PY82 model (spice)        18/08/2002  rev. 1.0  (ag)
*developed by a. galavotti
* valid for  py82 / ey 82 till 100ma
*
* connections:
*                                          plate
*                                          |
*                                          | | cathode
*                                          | | |
.subckt XEY82_xey82_0  p  k
B1 p k  i = 0.003* ( ( uramp (v(p k)) + 0.8 ) ^ 1.5 )
cpk p  k  10p
Rpk p k 1G
.ends py82

f(x)=0 if x<=0
f(x)=x if x>0

P.S. Parte One: AT + 2a3's heater

Here is the circuit :

Remeber to tune RF2 to get 2.5V for the heater. I put there a variable resistor as i've found that 2a3's heating current differs noticeably form one supplier (p.e. cinese)  to another (sovtek etc.). If youre planning to keep always the same tubes in your amplifer, substitute RF2 with a fixed resistor of the right value.

I've used also 2 coils to reduce the RFI from SS diodes . Their values are not critical, anyway if you want to know my choice,  I'm using a good 1.8mH on toroid core from scrap.

The coil on the AT section is 20H 200ma.

If you decide to go for EY/PY82, rember that all my types showed a little AC noise from heater/glass if you supply the heater with AC (expecially PY) so I've decided to use DC heating also for them.  This PS circuit is not showed here but as you can image it's quite simple.
 
 

P.S. Parte Two: Neative Bias + 6C45P's heater

Here is the circuit :

• 6c45P's heater:

• Negative Bias:

Listening Impressions
 

I like silence (I live in the country) and one goal I wanted absolutely to eploit in "angelo"  was no heater/PS noise. No noise means more dinamic range and details at the maximum.  The result is that this  amplifier is absolutely  the quietest i've ever made.

Listening to "Angelo"  deep in the night is something to tell.

For the ones  who decide to use vacuum tubes diodes instead of SS, in their amplifier, provided that evering remains equal you'll notice:

• Less Bass "punch"
• Sound seem more crispy and deatiled expecially voices start to "breath" .
• Soundstages opens and instruments seem more distinguishable.

• It's very difficult to come back...  ;)

That's all folks, Listen - have a happy new year and ENJOY!
 

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