Here is the link where is a aprox. calculator to know the output capacitor value depending of the input impedance of your amp or amps Coupling Capacitor Calculator by V-Cap
Hey Guys -
I started building one of these a few years back, but life got in the way and never finished. Since then there have been may iterations - so I've looked at the parts I have on hand vs Ale's design and have come up with esentially copying his, but using the OPTs I currently have (Electraprint 5k:600). While I believe this will reduce gain slightly, the higher load should help with distortion. Any other thoughts ?
I started building one of these a few years back, but life got in the way and never finished. Since then there have been may iterations - so I've looked at the parts I have on hand vs Ale's design and have come up with esentially copying his, but using the OPTs I currently have (Electraprint 5k:600). While I believe this will reduce gain slightly, the higher load should help with distortion. Any other thoughts ?
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An externally hosted image should be here but it was not working when we last tested it.
Sorry - you are correct. I just dug out the transfo's out and they are in fact 15k. I'll make the updates accordingly to the schema.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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If you want to use your 15K transformer you could be better off with a 4P1L. It's a bit microphonic, but manageable with around 2v input as long as you have a massive and well-damped chassis. Below 2v input and your best choice is Ale's 01A preamp which is stunning, as long as the 01As aren't microphonic. Or otherwise his active load for the 26. Have a look at his Bartola website.
What you really need to know is the rating in Henries. For a 26 it's good to see 100H or at least 60H and the more the better.
Depends what the gap is as well - the 4P1L wants 20mA at least.
What you really need to know is the rating in Henries. For a 26 it's good to see 100H or at least 60H and the more the better.
Depends what the gap is as well - the 4P1L wants 20mA at least.
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These old DHTs are completely unpredictable - it really is a case of individual tubes. Some are good, some are bad, some are microphonic and some are not. I doubt that you will find any help in buying just one make rather than another. The only way to guarantee some good ones is just sheer numbers - get a dozen and select.
As for where to buy them, look for tested good. Some ebay dealers are pretty good at testing, and you can look at feedback though this isn't a sure guarantee. I bought my stock from the smaller tube dealers - usually a few older guys with testers who still had stock. That worked very well, but I cleaned out a few of them of the DHTs I was after. You have to scour the internet for these dealers, which is what I did. I found a few really good guys, and bought a few other DHTs like 01A, 46 and 10Y while I was at it.
As for where to buy them, look for tested good. Some ebay dealers are pretty good at testing, and you can look at feedback though this isn't a sure guarantee. I bought my stock from the smaller tube dealers - usually a few older guys with testers who still had stock. That worked very well, but I cleaned out a few of them of the DHTs I was after. You have to scour the internet for these dealers, which is what I did. I found a few really good guys, and bought a few other DHTs like 01A, 46 and 10Y while I was at it.
Clicked more than 15 times and bought 30+ pcs. of #26,but only 3 manage to draws 5-6mA.
Now, I've just bought 4 gorgeous looking Cunningham CX-301A.
OMG, this hobby is killing me and can't find a schematic besides Bartola's cascode-FET gyrator circuit. And I'm a dumb when comes to IT.
You guys out there is awesome, spoon feeding newbies like myself .
Thanks!
Zekk
Now, I've just bought 4 gorgeous looking Cunningham CX-301A.
OMG, this hobby is killing me and can't find a schematic besides Bartola's cascode-FET gyrator circuit. And I'm a dumb when comes to IT.
You guys out there is awesome, spoon feeding newbies like myself .
Thanks!
Zekk
You asked the same question in post #3658 and euro21 already gave you a schematic in post #3660. What is it that you do not understand? Why do you want 10M45S CCS plate load for a 26? I do not think anybody else tried due to distortion is not very good at ~5ma. Perhaps a 2SK170 gyrator with 10M45S cascode can be better and for this Ale is your man to ask. I personally use LL1680, not great but good enough for me.