sonolink
Well-known member
moamps said:The input tube's plate resistor (100k) should be connected to B2 (after 51k resistor).
Ok I think I've corrected it. Please check
Thanks again
Sono
moamps said:The input tube's plate resistor (100k) should be connected to B2 (after 51k resistor).
sonolink said:Sorry I don't understand what you mean with "B2"
You haven't read my answer? This PSU needs two separate 12Vac windings.sonolink said: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.
No. It just doesn't make sense.I found JP2 strange too but I didn't bother with it much since I would use only 48v. Maybe some test point?
No; I think BC550 is adequate for handling 48V/10mA.On the other hand, Rochey has rised an interesting point regarding using a BC550 for the slow start phantom. Any comments on that?
abbey road d enfer said:You haven't read my answer? This PSU needs two separate 12Vac windings.
moamps said:The voltage 12Vac for heater secondary isn't optimal value, IMO.[...]So, the heaters should be connected in parallel, the heater voltage should be set to 6,3Vdc, and the power dissipation on regulator will be unnecessarily high if the heater secondary is 12Vac.
There are three possibilities, IMO:
1. Use of AC heater voltage of 6,3V, so the secondary voltage is 6,3Vac,
2. Use of DC unregulated heater voltage of 6,3Vdc (a rectifier with few RC stages), where the optimal secondary voltage is 7-8Vac and
3. Use of DC regulated heater voltage of 6,3Vdc where the optimal secondary voltage is about 9Vac.
Yes.sonolink said:I have a toroid that has 3 secondaries: 200+12+12. If I use one 12v secondary for heaters and the other for phantom would that sort out the issue?
abbey road d enfer said:Yes.
I would think moamps 1st suggestion is the easiest for you. put a 39R 2W+ resistor in parallels with the EF86 heater, then connect in series with the ECC88 heater.sonolink said:abbey road d enfer said:Yes.
Excellent! What about the heaters? Any suggestions?......please.....
No, this is parallels. See attachment.sonolink said:Like this?
abbey road d enfer said:No, this is parallels. See attachment.
DaveP said:I would never wire up heaters for a mic pre-amp like that. You need the best hum rejection you can get, so give it the 6.3V DC it needs. It's not just the hum in the tubes, its all the feed wires trailing around with AC on. No-one can predict what gets picked up like that.
DaveP said:Moamps gave you good advice and you should take it IMHO. If you cut too many corners it will not perform like a REDD47.
DaveP said:I have found an over spec 6V toroid will give you around 8.5V, rectify with two 47,000uF caps with a suitable metal clad resistor clamped to chassis between the two caps, end of problem
You mean with the screen connected to chassis on one end only?DaveP said:Supply the tube heaters via screened cable if you want to go to town.
My suggestion was based on using DC voltage, as the OP had posted.DaveP said:I would never wire up heaters for a mic pre-amp like that. You need the best hum rejection you can get, so give it the 6.3V DC it needs.
It's not just the hum in the tubes, its all the feed wires trailing around with AC on. No-one can predict what gets picked up like that.
That is true only if each half takes the same current; the EF86 takes 200mA and teh Ecc88 takes 365mA. The 39R resistor absorbs 165mA.sonolink said:What's the resistor for? If the Voltage source is 12VAC wouldn't placing the heaters in series give 6Vac to each one?
abbey road d enfer said:That is true only if each half takes the same current; the EF86 takes 200mA and teh Ecc88 takes 365mA. The 39R resistor absorbs 165mA.
My3gger said: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.
My3gger said:I think your layout will work good enough, just wanted to give some hints about improving it when you do another one.
My3gger said:I think your layout will work good enough, just wanted to give some hints about improving it when you do another one.
My3gger said:Btw, OEP A262A3E isn't output transformer, so use something else there.
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.Is this what you mean (please see attachment)? If not, could you please elaborate a bit more? I have a secondary 12VAC free winding for heaters.
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