How about Charcroft silver mica,how old are the Wimas, I think the newer ones use steel leads as a cost saving.
Light bulb for visual control of operation shunt reg
Hi Alex,
Having looked up again the photos of your Super Regs I also noticed a change VS obviously made in current production SR kits.
For visual control of operation they are using now a light bulb whereas in my older units LED's were applied.
Since dice45 pointed out that using an LED here is not the best way because this could result in a short-circuit in case of an overload or damage I would like to upgrade mines to bulbs as well.
Could you please tell me something more on this bulb applied here?
Is this an E10 bulb or other? And more important for me to know would be what voltage and current spec this light bulb has.
I would be happy if you could answer me this.
Thanking you in anticipation.
Günter
Hi Alex,
Having looked up again the photos of your Super Regs I also noticed a change VS obviously made in current production SR kits.
For visual control of operation they are using now a light bulb whereas in my older units LED's were applied.
Since dice45 pointed out that using an LED here is not the best way because this could result in a short-circuit in case of an overload or damage I would like to upgrade mines to bulbs as well.
Could you please tell me something more on this bulb applied here?
Is this an E10 bulb or other? And more important for me to know would be what voltage and current spec this light bulb has.
I would be happy if you could answer me this.
Thanking you in anticipation.
Günter
Indeed.
Yes, Dice45 pointed that out, and we also had a bad experience at VS with this. For example in our RTP each SR feeds over 100mA into the audio circuits, if this needs to be fully shunted a LED will be fried in no time. So we tried this: Light bulb. Your limit of continous full shunt operation is now the heatsinking of the shunt FET.
Surprisingly it sounded even better...
Yes, Dice45 pointed that out, and we also had a bad experience at VS with this. For example in our RTP each SR feeds over 100mA into the audio circuits, if this needs to be fully shunted a LED will be fried in no time. So we tried this: Light bulb. Your limit of continous full shunt operation is now the heatsinking of the shunt FET.
Surprisingly it sounded even better...
Thomas,
Yes indeed that makes sense.
Having looked up the link you gave me I see that this bulb is specified 14V/80mA .
There is also a version available with 6.3V/200mA.
Would that not be even more appropriate due to the larger current and even slightly higher power rating of this bulb considering the over 100mA current you were talking about??
Günter
Yes indeed that makes sense.
Having looked up the link you gave me I see that this bulb is specified 14V/80mA .
There is also a version available with 6.3V/200mA.
Would that not be even more appropriate due to the larger current and even slightly higher power rating of this bulb considering the over 100mA current you were talking about??
Günter
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Thomas,
By the way I'm also quite surpised to hear from you that each SR feeds over 100mA into the audio circuits of the RTP3!
My calculation based on latest instructions and input from members would give the following: Phono amp 19 mA, Line stage cascode 14 mA and SLCF 27 mA per side.
That would yield 60 mA in total which is signicantly lower than 100 mA you were talking about!
Could you also apart from the question above comment on this mismatch please.
Thank you very much.
Günter
By the way I'm also quite surpised to hear from you that each SR feeds over 100mA into the audio circuits of the RTP3!
My calculation based on latest instructions and input from members would give the following: Phono amp 19 mA, Line stage cascode 14 mA and SLCF 27 mA per side.
That would yield 60 mA in total which is signicantly lower than 100 mA you were talking about!
Could you also apart from the question above comment on this mismatch please.
Thank you very much.
Günter
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Hi Thomas. I am sure that you did likewise, try to find an LED that was rated beyond 20mA. I didn't find one. So I aimed close to 20mA. Did not think about using something other than an LED.
Running 100mA in the shunt, yeah, that is a lot of heat. I think I limited it to 5-6 Watt dissipation max. Shows why a delay is needed and getting the filaments going before turn 'on' the HT.
Joe
Ok, it's less than 100mA, my bad. Had to do the math for myself again, when the voltages are right there's no need to measure currents.
Phono: 19 + 1.5 mA
Line: 12 + 1 mA
SLCF: 23 + 0.5 mA
Shunt curent: 15 mA
The small figures are the supplies for grid voltage of the cascodes or the CCSs of the SLCF. So it's 72mA per channel. And 4.5W dissipation on the shunt FET in normal operation.
The bulb gets those 15mA in normal operation, and yes, it's max. 72mA that would go over the bulb if all the audio circuitry cuts out at once. Or the wiring has a short, that's more likely.
Phono: 19 + 1.5 mA
Line: 12 + 1 mA
SLCF: 23 + 0.5 mA
Shunt curent: 15 mA
The small figures are the supplies for grid voltage of the cascodes or the CCSs of the SLCF. So it's 72mA per channel. And 4.5W dissipation on the shunt FET in normal operation.
The bulb gets those 15mA in normal operation, and yes, it's max. 72mA that would go over the bulb if all the audio circuitry cuts out at once. Or the wiring has a short, that's more likely.
This is consistent with my estimate of about 55mA per channel for my RTP3Cs.
Didn't Allen advocate setting the shunt current to the same as the series current delivered to the circuitry? I have never had the nerve to increase mine beyond about 20mA, especially considering the whole current is shunted on switch-on, when the heaters are cold and the valves aren't conducting.
Alex
Didn't Allen advocate setting the shunt current to the same as the series current delivered to the circuitry? I have never had the nerve to increase mine beyond about 20mA, especially considering the whole current is shunted on switch-on, when the heaters are cold and the valves aren't conducting.
Alex
The only significant current draw variation could come from the SLCF driving a low Z load. But with the usual hifi gear input Rs and sensitivities 15mA of headroom will be sufficient.
We once built a microphone preamp which should be able to feed the output transformerless (of course) into 600R, for this we cranked up the shunt current. And quickly ran into thermal problems with the SR (of course)...
We once built a microphone preamp which should be able to feed the output transformerless (of course) into 600R, for this we cranked up the shunt current. And quickly ran into thermal problems with the SR (of course)...
Hi Alex,
I wanted to raise the same question to Thomas to hear if it could give a sonical advantage to increase the shunt current to much more than 15 mA although he said already that this is sufficient.
However before trying that I would definitely first replace the current smaller heatsinks ( 25 mm length ) of the kits with larger ones ( 50 or 63 mm length ).
Looking at pictures from more recent RTP3's with the new Gen2 SR I see that VS has applied that already in the meantime.
Probably this has been done there only for better heat dissipation to stay much more on the safe side and not in order to go for much higher shunt currents I would assume.
Any comments from you on that Thomas?
Thanks
Günter