Opinions on Redd47 P2P Layout please

[My3gger]

Solder 1k grid stopper resistors directly to E88CC pins, join their other ends and wire them to 1M/22n point. This is good general practice with tubes like this one.
If you turn tube sockets around, it is easy having power connections on the bottom, away from sensitive parts like grid inputs, which helps get lower noise and smaller current loop.

Like this? (see attachment)

Yes, like that, just solder resistors directly to two tube socket pins and leave the rest as it is on picture.
By redoing layout i meant board in the first place, where turret pins are. If you have HT at the top of turret board all sensitve parts need to cross it, which can mean troubles sometimes. Try to get it to bottom like in V72 and you will see there is no other way sometimes than turning (rotating) sockets 180 degrees.
Heater wires look fine to me.
Nice to hear that you want experiment with output and other things. Very rewarding

 

[sonolink]

By redoing layout i meant board in the first place, where turret pins are. If you have HT at the top of turret board all sensitve parts need to cross it, which can mean troubles sometimes. Try to get it to bottom like in V72 and you will see there is no other way sometimes than turning (rotating) sockets 180 degrees.

Oh I see what you mean. Ok I'll try to do my best identifying the different parts and their function and redraw my layout then
Thanks for the tip!
Cheers
Sono

 

[sonolink]

No this is what I mean, it's a very basic CT power supply.  Diode drops have less effect on voltage than a bridge and the diodes are very low drop Schottky type.

Good luck
DaveP

Ok I see what you mean....isn't there a way of doing that starting from 12 vac without a CT? I have a toroid with a free 12 vac winding that would be great to use for heaters

Like this maybe? Would that work and be correct?
Thanks
Sono

 

[abbey road d enfer]

Like this maybe? Would that work and be correct?

No. The components marked "6Vac" are resistors. You would end up dissipating more power in these resistors than in the heaters and/or insufficient voltage on the heaters.
You may turn this problem in every direction, you will find that my recommended solution is just the only one practical and sensible if you want to use your existing xfmr.

 

[sonolink]

No. The components marked "6Vac" are resistors. You would end up dissipating more power in these resistors than in the heaters and/or insufficient voltage on the heaters.
You may turn this problem in every direction, you will find that my recommended solution is just the only one practical and sensible if you want to use your existing xfmr.

Abbey, don't get me wrong. I'm just trying to learn here ok? What you suggested is, as I stated, what I'm more familiar with in my guitar amps and I'll probably go for that anyway, I sincerely think AC heaters properly twisted and routed in chassis isn't a problem. BUT, I was curious to learn about the other options Moamps suggested and DaveP described

SO, my next idea is: since the resistors would have to cope with plenty of heat etc in my previous proposal, how about I rectify 12VAC to 12VDC and THEN I regulate to 6.3VDC? Would that be better? This is a question out of curiosity ok? Imagine that I HAVE to go the DC way....

Cheers
Sono

 

[abbey road d enfer]

SO, my next idea is: since the resistors would have to cope with plenty of heat etc in my previous proposal, how about I rectify 12VAC to 12VDC and THEN I regulate to 6.3VDC? Would that be better? This is a question out of curiosity ok? Imagine that I HAVE to go the DC way....

Yes, you could do that; you would waste twice more energy in the regulator than in the heaters. You could also drop  the 12Vac  down to 6.3Vac with a resistor; you would waste as much energy in the resistor than in the heaters. That would be the simplest solution. You may have to implement the noise balancing scheme I mentioned earlier.

 

[sonolink]

OK so definitely the way to go is either what you suggested earlier together with a rigorous "wiring hygiene and discipline" or a transformer with 200v, 50v and 6.3v

One last question ok?

The phantom circuit on that PSU is ok and worth using?
I've reattached the schem...

 

[abbey road d enfer]

OK so definitely the way to go is either what you suggested earlier together with a rigorous "wiring hygiene and discipline" or a transformer with 200v, 50v and 6.3v

One last question ok?

The phantom circuit on that PSU is ok and worth using?
I've reattached the schem...

It wouldn't be right; as I mentioned earlier, with a single 12V winding, one of the voltages has AC superimposed on it; of courese it can't be phantom, so the heaters would be DC but still radiating as much as AC heaters. With two separate 12Vac winding, it would be correct.

 

[sonolink]

Sorry I explained myself incorrectly. The toroid I'm using has THREE secondaries, unlike the one on the posted PSU schem. 200v for HT, 12Vac for the heaters using the schem you suggested (in series with a 39R resistor in parralel of one the EF86) and ANOTHER 12VAC that would be used to create 48v phantom following the pertinent section on that same schem.

My question is: is the 48V section of that PSU ok and worth using or you would suggest using some other one for some specific flaw, noise or problem for instance?

Cheers
Sono

 

[abbey road d enfer]

Sorry I explained myself incorrectly. The toroid I'm using has THREE secondaries, unlike the one on the posted PSU schem. 200v for HT, 12Vac for the heaters using the schem you suggested (in series with a 39R resistor in parralel of one the EF86) and ANOTHER 12VAC that would be used to create 48v phantom following the pertinent section on that same schem.

My question is: is the 48V section of that PSU ok and worth using or you would suggest using some other one for some specific flaw, noise or problem for instance?

Cheers
Sono

Generating 48V out of a 12Vac winding is not very energy-efficient. If you had to power a large number of mics, I would recommend using a dedicated 48V xfmr with full-wave rectification, but here, for a single mic, it is not very important.
However, I shall point out that the current spikes in the secondary, rectifiers and caps may create issues if they were allowed to feed through the audio ground. The "power" lines should not be allowed to pollute the sensitive audio ground. In practical terms, it means the complete 48V circuit must be layed out as a separate unit (no common ground, no ground plane) and connected to the audio ground at a single point.

 

[kambo]

Sorry I explained myself incorrectly. The toroid I'm using has THREE secondaries, unlike the one on the posted PSU schem. 200v for HT, 12Vac for the heaters using the schem you suggested (in series with a 39R resistor in parralel of one the EF86) and ANOTHER 12VAC that would be used to create 48v phantom following the pertinent section on that same schem.

My question is: is the 48V section of that PSU ok and worth using or you would suggest using some other one for some specific flaw, noise or problem for instance?

Cheers
Sono

Generating 48V out of a 12Vac winding is not very energy-efficient. If you had to power a large number of mics, I would recommend using a dedicated 48V xfmr with full-wave rectification, but here, for a single mic, it is not very important.
However, I shall point out that the current spikes in the secondary, rectifiers and caps may create issues if they were allowed to feed through the audio ground. The "power" lines should not be allowed to pollute the sensitive audio ground. In practical terms, it means the complete 48V circuit must be layed out as a separate unit (no common ground, no ground plane) and connected to the audio ground at a single point.

how many mics u think u gonna power from ur mic pre's 48 V ?

in any case,
there is a very easy solution....
either u listen to Abbey, or u find out the hard way  ;D

 

[sonolink]

Generating 48V out of a 12Vac winding is not very energy-efficient. If you had to power a large number of mics, I would recommend using a dedicated 48V xfmr with full-wave rectification, but here, for a single mic, it is not very important.
However, I shall point out that the current spikes in the secondary, rectifiers and caps may create issues if they were allowed to feed through the audio ground. The "power" lines should not be allowed to pollute the sensitive audio ground. In practical terms, it means the complete 48V circuit must be layed out as a separate unit (no common ground, no ground plane) and connected to the audio ground at a single point.

My idea is to build a 2ch Redd47 so I will power 2x mics max.

I've attached the 48v PSU section properly drawn for clarification

To follow your directions I would also have to connect the ground to switch phantom off on the 48v on/off switch (p2p layout) to the 48v PSU 0v rail right?

Audio gnd connected to chassis would be transformers gnd, pin1 and DI gnd only, correct?

Thanks

 

[abbey road d enfer]

To follow your directions I would also have to connect the ground to switch phantom off on the 48v on/off switch (p2p layout) to the 48v PSU 0v rail right?

I don't understand; please rephrase.

Audio gnd connected to chassis would be transformers gnd, pin1 and DI gnd only, correct?

Not xfmr ground! Negative pole of C20&21.

 

[sonolink]

I don't understand; please rephrase.

Ok I'll try again, sorry

I'm trying to clarify the ground scheme basically.

1-On the p2p layout there is a GND symbol near the 48v on/off switch that is also connected to the 48v 0v return. Is that a chassis connection? Is that necessary? Isn't it better that phantom is NOT connected to chassis and only to it's own 0v return to keep it away from audio ground and prevent noise, etc?

2-The other GND connections on the p2p layout I understand them as chassis, thus pin1, DI, and the 0v rail to which input  and output transformers are connected. Is that correct?

3- I understand that there is no connection to chassis from any part of the PSU sections since they are each connected to their respective 0v return. The only connection to chassis here would be the Earth at the IEC connector. Is this correct?

I hope that makes sense

Cheers
Sono

 

[abbey road d enfer]

In order to keep RFI/EMI at bay, pin 1 of the input XLR should be connected to chassis. The phantom 0V should be connected there also. Since you use a separate winding for the 48v rail, that will be the only reference connection necessary.
The B+ 0v should be connected as close as possible to the output stage, where the negative of the decoupling capacitor, the cathode resistor and its bypass cap should join.
The heater's 0v can be "grounded" (I prefer the word referenced) almost anywhere clean.

 

[sonolink]

Sorry I’ve been out gigging.

I've marked on the p2p schem where the gnd and 0v connections should go. Could you please check it to make sure I'm following you 100%?

Cheers
Sono

 

[abbey road d enfer]

Sorry I’ve been out gigging.

I've marked on the p2p schem where the gnd and 0v connections should go. Could you please check it to make sure I'm following you 100%?

Cheers
Sono

That is essentially correct.
ther are still two points that must be addressed.
The DI jack ground; connecting it to chassis as it is, is good for RFI/EMI protection, but may not be that good in terms of noise (hum). You may have to experiment with the position.
Alternatively, you could connect it to the audio 0v (as close as can be to the input stage) via ferrite bead AND to chassis via a 0.1uF ceramic cap, with very short leads.
Heaters: it seems you have opted for AC heaters; anyway you need to reference this voltage to a "ground". Best would be a potentiometer (anything from 470r to 10k) with wiper to ground.

 

[sonolink]

The DI jack ground; connecting it to chassis as it is, is good for RFI/EMI protection, but may not be that good in terms of noise (hum). You may have to experiment with the position.
Alternatively, you could connect it to the audio 0v (as close as can be to the input stage) via ferrite bead AND to chassis via a 0.1uF ceramic cap, with very short leads.

Ok, I will experiment with that

Heaters: it seems you have opted for AC heaters

I decided to give your suggestion a go

anyway you need to reference this voltage to a "ground". Best would be a potentiometer (anything from 470r to 10k) with wiper to ground.

Oooops you're right. I forgot to ground them 
What's the pot for? I mean, why not a resistor, or resistor pair with chassis in between them kinda thing? "Tuning" I guess?

Thanks a lot for all your input Abbey

 

[abbey road d enfer]

What's the pot for? I mean, why not a resistor, or resistor pair with chassis in between them kinda thing? "Tuning" I guess?

You guessed right.

 

[sonolink]

Kewl

Ok, I'm ready to build then I guess!!
Thanks a LOT for your guidance Abbey. I'll report back with some pics as soon as I get to build this baby

Cheers
Sono