FYI: I heard from Monolith Magnetics regarding the PS chokes. The dielectric strength of the coil former that isolates the coil from the core is> 15kV.
banpuku, the dielectric strength practically means nothing unless the total coil is fully encapsulated by solid insulation with a certain thickness - for a typical choke it is the creepage and clearance distance that is important, and what withstand voltage the manufacturer tests the product to.
Also important is to what VAC across the coil the manufacturer rates the part, and specifies the inductance at.
Also important is to what VAC across the coil the manufacturer rates the part, and specifies the inductance at.
With warm heaters your amp is ready to produce sound from any current passing suddenly through the output tubes. Get rid of the delay circuit. The thermistors pass current even when cold so they don't do what you think they will and they react within .1 sec. and pass full current very quickly.
When switching on B+, and hearing a pop, is the signal input to the amp muted/shorted or do you have some signal source connected?
The amps are producing music without random pops. The only time the amp "pops" is when b+ is turned on. This is with the signal source connected.
Short the signal input and check if there is an audible pop when B+ is turned on.
If there is no pop, then you have a mains wiring related transient with your signal source.
If there is still a pop, then short the output stage grid to 0V, to check if it relates to the input stage or output stage.
If there is no pop, then you have a mains wiring related transient with your signal source.
If there is still a pop, then short the output stage grid to 0V, to check if it relates to the input stage or output stage.
Do you understand that hot cathodes will pass current through the output tubes when the B+ is applied, and that is the same as music output AC through the output transformers? But it's current rush pop.
20to20: I understand that it is current rush pop. What I don't understand is "why" this is happening and "how to solve".
switch bounces, inductive load, try add snubber. Hope it helps.
Switch Bounce and How to Deal with It - Technical Articles
https://m.littelfuse.com/~/media/el...load_arc_suppression_application_note.pdf.pdf
Switch Bounce and How to Deal with It - Technical Articles
https://m.littelfuse.com/~/media/el...load_arc_suppression_application_note.pdf.pdf
Why????? Because your cathodes are hot before the B+ is applied! It's to be expected, not surprising at all. It's because you delay the B+. You are in effect hot switching your amp. Thermistors do not do what everyone thinks they do. They are over and done working in .1 sec. after power is applied to them and they also allow startup current through that creates a pulse in the OPT that goes to the speaker.
If you use "standby" switch, the PSU pre charging, the output tube working with reduced B+ (and different -reduced- operating point), and rising time of B+ is about 0.8s to reduced maximum (if you use for example 3k3 resistor paralleled with standby switch), so inrush "pop" can be significantly moderated.
After shorting standby switch, practically shouldn't be pop.
After shorting standby switch, practically shouldn't be pop.
I tried the snubber: no help. still pops.
So, here is what I have tried:
1. Resistor across 1 AC leg switch
2. snubber
3. thermistor across 1 AC leg and then another thermistor across the other AC leg swith
4. shorted 45B output tube grid to ground
Still, "pop" on start up.
Darn!
So, here is what I have tried:
1. Resistor across 1 AC leg switch
2. snubber
3. thermistor across 1 AC leg and then another thermistor across the other AC leg swith
4. shorted 45B output tube grid to ground
Still, "pop" on start up.
Darn!
banpuku,
Use a 5AR4 rectifier, if the voltage and current ratings are OK for your amplifier.
It will have a little more drop than the type 83.
But . . . the 5AR4 has an intrinsic slow start, it is an indirectly heated cathode.
That way, you do not have to use a B+ [delay] switch. No more Pop! at the amp turn on.
Use a 5AR4 rectifier, if the voltage and current ratings are OK for your amplifier.
It will have a little more drop than the type 83.
But . . . the 5AR4 has an intrinsic slow start, it is an indirectly heated cathode.
That way, you do not have to use a B+ [delay] switch. No more Pop! at the amp turn on.
I have a pair of 5z3 rectifiers arriving on Monday. I will try them.
Yes, 490V B+. These are 45B tubes.
Yes, 490V B+. These are 45B tubes.
I see the spec sheet says B+ (supply) to be 495v but plate voltage is another thing specified, and I believe I read this tube to have 420v max plate voltage, and that does not mean 420v a-k voltage. It also seems to suggest on the sheet you referenced for voltages that it specifies the 1.8K cathode resistance which you have but with 408v on the plate.
banpuku,
My Post #76 has an error. I got caught by the administrator 30 minute limit,
someone came to the door and distracted me.
The 5AR4 max voltage is too close to your B+ secondary voltage 500V versus 490V.
Your Pop! is the result of a warm 45 tube filament, and then B+ coming on suddenly when you switch the 83 B+ switch.
The 5Z3 is only rated for 450V transformer, not 490V transformer.
And the 5Z3 is almost instant on, because it is a directly heated filament (no cathode).
Find another tube rectifier, which meets the voltage rating of your transformer, and current draw of your amplifier.
They will have a little more voltage drop than the type 83.
Be sure to use a tube rectifier that is an automatic slow start, (indirectly heated cathode).
That way, you do not have to use a B+ [delay] switch.
No more Pop! at the amp turn on.
This problem can be solved with the right rectifier, you are not going to be able to solve it with the type 83 rectifier.
My Post #76 has an error. I got caught by the administrator 30 minute limit,
someone came to the door and distracted me.
The 5AR4 max voltage is too close to your B+ secondary voltage 500V versus 490V.
Your Pop! is the result of a warm 45 tube filament, and then B+ coming on suddenly when you switch the 83 B+ switch.
The 5Z3 is only rated for 450V transformer, not 490V transformer.
And the 5Z3 is almost instant on, because it is a directly heated filament (no cathode).
Find another tube rectifier, which meets the voltage rating of your transformer, and current draw of your amplifier.
They will have a little more voltage drop than the type 83.
Be sure to use a tube rectifier that is an automatic slow start, (indirectly heated cathode).
That way, you do not have to use a B+ [delay] switch.
No more Pop! at the amp turn on.
This problem can be solved with the right rectifier, you are not going to be able to solve it with the type 83 rectifier.
6A3sUMMER: Per your post, I have 2 things going on here:
1. Using my existing PS schematic (cLCLC), both the 5Z3 and 83 limits are too close to operating voltage. So, if the c (0.68uF) is eliminated, then the choke power supply would bump up the operating limits of the 5Z3 to 550V and the 83 to 550-595V. Also, the choke power supply would produce a B+ of 430V, well within the specs of the 5Z3 and 83.
2. HOWEVER, both the 5Z3 & 83 are directly heated and thus this would continue to have the pop issue. Assuming the removal of c1, then we could safely use the 5AR4 with the LCLC PS design. The 5AR4 would produce 420V output, assuming the 500-0-500 power transformer.
Sound right?
1. Using my existing PS schematic (cLCLC), both the 5Z3 and 83 limits are too close to operating voltage. So, if the c (0.68uF) is eliminated, then the choke power supply would bump up the operating limits of the 5Z3 to 550V and the 83 to 550-595V. Also, the choke power supply would produce a B+ of 430V, well within the specs of the 5Z3 and 83.
2. HOWEVER, both the 5Z3 & 83 are directly heated and thus this would continue to have the pop issue. Assuming the removal of c1, then we could safely use the 5AR4 with the LCLC PS design. The 5AR4 would produce 420V output, assuming the 500-0-500 power transformer.
Sound right?