Hi, i want to build a dumbleator, an external buffer for fx loop. It is a tube buffer. My question is: they want 135V from a power transformer that convert 115V to 135V that will be rectified. Ain't that a very low voltage for a 12ax7? If not, why not using directly the 120V from the wall, it is not that far from 135V? I would just use a 6.3V transformer for the heater. The problem is that i can't find any 135V transformer.... I have found a 170V transformer at a good price, i don't know if it is way to much...
What do you think?
Thank you
Frank
What do you think?
Thank you
Frank
Using the mains power directly is an invitation to death. Don't!
Yes, 135V is low, but you're after effects, right? Don't sweat small voltage differences- a 120 or 150V transformer will work fine. Here's one that will give you 140V:
Antek - AN-05T160
Yes, 135V is low, but you're after effects, right? Don't sweat small voltage differences- a 120 or 150V transformer will work fine. Here's one that will give you 140V:
Antek - AN-05T160
okay, i didn't thaught about it that way (safety).
That is a nice transformer, i have used Antek transformer in the past, for my linkwitz labs pluto's speaker, they are very well made, great stuff. I am not sure it will fit in the enclosure i was planning to use, but i will try to see if it is possible.
Thank you for your help!
Frank
That is a nice transformer, i have used Antek transformer in the past, for my linkwitz labs pluto's speaker, they are very well made, great stuff. I am not sure it will fit in the enclosure i was planning to use, but i will try to see if it is possible.
Thank you for your help!
Frank
That Antek IS a nice transformer, but looks like overkill for running a single 12AX7. I'd use two small 6V or 12V filament transformers (a 1A secondary rating should be enough) as Doug shows in #3. Together they're smaller and probably weigh a third of what that Antek weighs, and will fit in your enclosure.
Agree.
Yet, if that 170V transformer is cheap, available, small, cute, etc. , you *can* use it, lowering voltage is easy.
And anyway, I think the Dumbleator used the lowest voltage he could , for unknown personal reasons of the highest mystic value (did I say $$$$
?).
Of course, you may have to use some slightly higher voltage caps.
Please post the schematic here
Yet, if that 170V transformer is cheap, available, small, cute, etc. , you *can* use it, lowering voltage is easy.
And anyway, I think the Dumbleator used the lowest voltage he could , for unknown personal reasons of the highest mystic value (did I say $$$$
?).Of course, you may have to use some slightly higher voltage caps.
Please post the schematic here
This may work: Single Preamp Tube Project Power Transformer High voltage, though.
Another option is to look for a Stancor PS-8415 which was used in the Alembic F2B preamp with two 12AX7's. They can still be found on ebay occasionally.
EDIT: I haven't dealt with them, but it looks like Leeds Radio in NY still has the PS-8415 for $22.
Another option is to look for a Stancor PS-8415 which was used in the Alembic F2B preamp with two 12AX7's. They can still be found on ebay occasionally.
EDIT: I haven't dealt with them, but it looks like Leeds Radio in NY still has the PS-8415 for $22.
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I have deal with tube depot, it is a good place to deal with, imao. The 170 V transfo i was looking for was this one:
110V 30W Transformer 170V 6.3V for 6N3 PRE AMPLIFIER | eBay
chinese shitty transformer probably made by beated children
For using 120V, i would use two of these :
VPS12-2000 Triad Magnetics | 237-1256-ND | DigiKey
Since i am ordering other thing from digikey, all would come in a box with the second option... The only fear i have is hum, i hate them so much. For now my project have work with mercury magnetic and hammond transformer so i have never had any problem with transfo, i hope this is not the begginning of hell...
What do you think?
110V 30W Transformer 170V 6.3V for 6N3 PRE AMPLIFIER | eBay
chinese shitty transformer probably made by beated children
For using 120V, i would use two of these :
VPS12-2000 Triad Magnetics | 237-1256-ND | DigiKey
Since i am ordering other thing from digikey, all would come in a box with the second option... The only fear i have is hum, i hate them so much. For now my project have work with mercury magnetic and hammond transformer so i have never had any problem with transfo, i hope this is not the begginning of hell...
What do you think?
Cool! Of course the Alembic used a ladder of caps and resistors to get the exact voltage they wanted. But that's a great transformer source for me! I have two really old "footwitch" tube chassis, each with a fender-circuit preamp channel but then a small output transformer and teensie speaker as a 'speaker emulator'... I'd rather just convert them both to the exact Alembic schematic. They have decent pots, but inferior power supplies. I might just bolt the two stompboxes together, externalize the power supply with the real Alembic transformer and even better chokes and caps, convert to DC heaters or raise the AC with with some DC offset bias like Weber, and make a great little Alembic preamp that could be positioned closer to the guitar and both channels in series, so I could use one, the other, or both via the footswitches.
I bet if you just used a 115v output transformer in the 50 to 200VA output range
you would realy get close to 135 v out if not higher in your case. Rember small power transformers don't have good regulation. That is a 50va 115 v output transformer will have about 115v out when loaded to about 400ma but at a much lower load the output will be substantialy higher.
you would realy get close to 135 v out if not higher in your case. Rember small power transformers don't have good regulation. That is a 50va 115 v output transformer will have about 115v out when loaded to about 400ma but at a much lower load the output will be substantialy higher.
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