Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Captain chunkulus on January 06, 2020, 09:29:04 pm
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So I have a 24v center tapped secondary and I wanted to try to knock it down to 12v then 5v and also elevate the heaters. Here's what I was thinking.
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Here's a jpeg.
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I'm thinking sparks! You have the +12 and +5 grounds connected to the elevated circuit ground. Maybe even smoke!
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I'm thinking sparks! You have the +12 and +5 grounds connected to the elevated circuit ground. Maybe even smoke!
Right, lol. That's why I'm here. I had thought to maybe float the grounds so that they make ground just though the elevation ground like this?
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You will want a capacitor after the LV rectifier.
If you are running DC on the heaters there is no hum-advantage from Elevation.
If you need elevation for some high-cathode stages, then the relay circuit will be elevated which may be awkward.
K.I.S.S.
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You will want a capacitor after the LV rectifier.
If you are running DC on the heaters there is no hum-advantage from Elevation.
If you need elevation for some high-cathode stages, then the relay circuit will be elevated which may be awkward.
K.I.S.S.
Sorry, I was In a hurry last night to get it posted. There is a 10,000 uf cap after the diodes. Thus is a 5 stage preamp with 3 stages and then a cathode follower hence the elevation. So, do you think the way I have it wired will work okay?
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If you are running DC on the heaters there is no hum-advantage from Elevation.
I would NOT elevate until you "prove" it's required.
since you're at 12vdc for filaments, test, add 10000uf, retest
At best you have multiple floating points for future techs to light up on, at worst you have smoldering pieces.
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If you are running DC on the heaters there is no hum-advantage from Elevation.
I would NOT elevate until you "prove" it's required.
since you're at 12vdc for filaments, test, add 10000uf, retest
At best you have multiple floating points for future techs to light up on, at worst you have smoldering pieces.
Sorry then, maybe just ground the center tap and don't use the two 100 ohm resisters at all and don't use elevation until I see what my voltages look like for the cathode follower.
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So no need for the 100ohm Center tap?
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....... and then a cathode follower hence the elevation.
Merlin has a fix for the CF problem.
http://www.valvewizard.co.uk/dccf.html (http://www.valvewizard.co.uk/dccf.html)
I like using dc stand off voltage (heater elevation) of 70 to 80dcv with a humdinger pot. Worked great on my builds. I posted this dcv in another thread way back and Ed C. did a test with the dc stand off and it didn't knock out the hum until he got it to 70 to 80dcv. :icon_biggrin:
I take the dcv from the very last/1st preamp tube, because the dcv is the best filtered there and less dcv to drop and waste PT heater current. And 2 less heater wires to deal with.