Has anyone built a version of this preamp with 101D tubes? I have a bunch (14-16) and thought why not?
Shawn
Shawn
My 26 is similar to that of euro21 without the S&B....and instead has a 100K volume at the input....
What you need to know is the input impedance of your amp or amps in order to know wich capacitor value you need as output capacitor.
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 ?
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.
5K is a terrible low value impedance for a 26 with a Rp of about 8K.. My recommendation would be a minimum impedance of 15K.
A Magnequest parafeed B7-15K performs adequately..
..my 2 cents
A Magnequest parafeed B7-15K performs adequately..
..my 2 cents
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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If you are updating your drawing, put in a reference symbol for ground on the output as well.
And, but that is my preference, I favor the operating point of the 26 at about 120V B+ at 6mA iso 250Volts..
And, but that is my preference, I favor the operating point of the 26 at about 120V B+ at 6mA iso 250Volts..
Thank you again. Made the update. I will certainly play with the op point when I have it on my tabletop.
Hi guys,
Rolling the 26 now, any tubes that I should try to get and any I should avoid ( i.e those that are prone to microphonics ? ) 26 seems quite rare anyone can PM me where to get NOS ones?
Thanks.
Rolling the 26 now, any tubes that I should try to get and any I should avoid ( i.e those that are prone to microphonics ? ) 26 seems quite rare anyone can PM me where to get NOS ones?
Thanks.
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
Hi all,
I plan to build a preamp running tube 26 with 10M45s in CCS.
If anyone has this schematic or link address, pls post it here.
Thanks and best regards,
I plan to build a preamp running tube 26 with 10M45s in CCS.
If anyone has this schematic or link address, pls post it here.
Thanks and best regards,
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.
The 10M45 is a loser strategy at 5mA. The results at 5mA will vary wildy from sample to sample. The 10M45 wants something more like 10mA to work well. And, I mean functionally, not sonically.
You need another CCS for 5mA.
You need another CCS for 5mA.
Felipe, euro21 did post everything, schematic, capacitor + resistor values, tubes used, voltages, currents, everything. You can look at the indicated post #3660.