My first thread here, hopefully some members could direct me to the right place if this has already been discussed. I would take the following schematic and run the power tubes with KT88 and possibly a tube rectifier. I couldn't find any schematic available for 6SN7 paired with KT88. This was the closest thing I could find on one of my books. Any suggestions or possibly direct me to the right area of research and discussion for this newb. to read up on? Or anything t take note on? Thanks in advance.
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Seems to be a classic design. Dual triode preamp and driver and ultralinear output single ended pentode. NFB from transformer.
The key item is the output transformer. Can you get it?
The key item is the output transformer. Can you get it?
The schematic BOM requires 2 x 5k primary and 8 ohm secondary at 15w power rating. Should not be too difficult for me to locate, I believe Edcor or Hammond might have something similar?
If you look for a very good output transformers:
https://sklep.toroidy.pl/en_US/p/TTG-EL84SE-Tube-output-UL-transformer-5kOhm-EL84-6V6-SE/572
https://sklep.toroidy.pl/en_US/p/TTG-KT88SE-Tube-output-UL-transformer-3kOhm-KT88-300B-SE/566
https://sklep.toroidy.pl/en_US/p/TTG-EL84SE-Tube-output-UL-transformer-5kOhm-EL84-6V6-SE/572
https://sklep.toroidy.pl/en_US/p/TTG-KT88SE-Tube-output-UL-transformer-3kOhm-KT88-300B-SE/566
15W for a single 6V6 is a bit exagerated, I don't know the KT88 you want to use, so let me avoid to emmit opinions regarding it.
You want to use KT88 tubes because?
You want more power output
You like the looks of the KT88
You have heard that they are very good sounding (a lot of other tube types are very good sounding too).
You already have two or more KT88 tubes.
You heard a friends KT88 amplifier (single ended?).
You read an advertisement of a KT88 amplifier.
Etc.
Or . . . What?
"Requirements drive the path to a solution".
You want more power output
You like the looks of the KT88
You have heard that they are very good sounding (a lot of other tube types are very good sounding too).
You already have two or more KT88 tubes.
You heard a friends KT88 amplifier (single ended?).
You read an advertisement of a KT88 amplifier.
Etc.
Or . . . What?
"Requirements drive the path to a solution".
Hello DerekRonin:
There are many proven KT88 Se designs. Rather than trying to modify a design you are not familiar with or have the DIY skill to do. Perhaps you might consider following a proven design. There are a couple of well made videos out there on a very successful design.
DIYAudio Members BlueGlow, and Steph have both produced Youtube video series that are well worth watching. These videos will give a very good idea of the scale of the project and some very useful insight into the build and design process.
I hope this helps
There are many proven KT88 Se designs. Rather than trying to modify a design you are not familiar with or have the DIY skill to do. Perhaps you might consider following a proven design. There are a couple of well made videos out there on a very successful design.
DIYAudio Members BlueGlow, and Steph have both produced Youtube video series that are well worth watching. These videos will give a very good idea of the scale of the project and some very useful insight into the build and design process.
I hope this helps
#7 88 is golden number , very lucky number for most yellow skin people ,, in my country a sim card with 88 is very expensive compared to other number
Hi SCD, I did have the chance to build the one by Alex Gendrano. It sounds wonderful and I love it. This is more a trial-and-error, learning experience for me for the KT88/6SN7. I couldn't find a schematic with a proper build with this combination, (only 300B). Noticed a few of the China suppliers with this type of topology, so it kind of piqued my interest and curiosity. Can't help it, I'm just a tinkerer by nature.
Hello DerekRonin:
You may be at the point where you should consider increasing your knowledge of how circuits work. Studying the development process behind the circuit. A fellow named Patrick Turner from Australia developed a very good website before he passed away that is still available on the calculations involved (http://www.turneraudio.com.au/ ). This is a great website and well worth spending some time understanding his work.
Another fellow is Matt at Cascade Tubes ( https://www.cascadetubes.com). He goes to the effort of explaining the process of how he develops his circuits with graphs. He also does nice case work for very beautiful presentation.
Then there is the books by Morgan Jones, Merlin Blencoe.
Then there is the section on this website devoted to tube learning.
Lots of information to study. It takes a while to get your head around this stuff, everybody learns differently. Trial and error works but can be expensive and rather dangerous.
Good luck
Nuff said for now
I hope this helps
You may be at the point where you should consider increasing your knowledge of how circuits work. Studying the development process behind the circuit. A fellow named Patrick Turner from Australia developed a very good website before he passed away that is still available on the calculations involved (http://www.turneraudio.com.au/ ). This is a great website and well worth spending some time understanding his work.
Another fellow is Matt at Cascade Tubes ( https://www.cascadetubes.com). He goes to the effort of explaining the process of how he develops his circuits with graphs. He also does nice case work for very beautiful presentation.
Then there is the books by Morgan Jones, Merlin Blencoe.
Then there is the section on this website devoted to tube learning.
Lots of information to study. It takes a while to get your head around this stuff, everybody learns differently. Trial and error works but can be expensive and rather dangerous.
Good luck
Nuff said for now
I hope this helps
Much appreciate the reference materials, and help in directing me to the right place. I'll definitely brush more on my studying. I've gone through these books and built 3 units (just following the experience builders' post). I agree, still have far more to learn and understand and wrap my head around. Seeing that I've built a El34 and KT88 (both with 12AX7). Wanted to try something different, but I do know it is probably beyond my current capabilities. So was hoping someone could or would direct me to areas to future my journey in this hobby. So do I appreciate you taking it easy on an amateur like myself, instead of the typical "If you need to ask, you are not ready". Here are just some of the books I've utilized to help me better understand everything involved.
The difference you are going to find is a KT88 is gonna need more voltage swing from the driver than a 6L6 does. That first design shows the output tube with -28V on the cathode (and fixed bias on a SE amp...), you are gonna end up with -40 to -42V with a KT88 and I'm not sure that cascaded 6SN7 will do it.
You might instead try the cascode 6SN7 front end I used with my 300B amp (which is what that second one you posted is doing), and replace the 300B in my amp with a KT88 and use some plate to plate feedback like they did in that second one, but try a bit more like around 300K. And I would then skip the GNFB. Looks like the seconds one is wired in pentode instead of UL, with UL use something like a 1.2K screen stopper and with UL you can probably get away with just using "Schade" feedback like that blueglow/Kegger amp did. I like simple/fewer parts in my builds.
Have fun tinkering and don't let people discourage you 🙂
https://www.skunkiedesigns.com/300b
You might instead try the cascode 6SN7 front end I used with my 300B amp (which is what that second one you posted is doing), and replace the 300B in my amp with a KT88 and use some plate to plate feedback like they did in that second one, but try a bit more like around 300K. And I would then skip the GNFB. Looks like the seconds one is wired in pentode instead of UL, with UL use something like a 1.2K screen stopper and with UL you can probably get away with just using "Schade" feedback like that blueglow/Kegger amp did. I like simple/fewer parts in my builds.
Have fun tinkering and don't let people discourage you 🙂
https://www.skunkiedesigns.com/300b
Hi Stephe, huge fan of your content, as matter of fact one of your older posts from another forum got me digging deeper to see if I was able to find a schematic to start with. I appreciate your suggestion and guidance! Will definitely try these suggestions out and continue my tinkering. 😃
If you have flexibility for the input tube, there are other options that would make your life easier. I have used EC/PC86 triodes, very linear, easy to get 60Vp (120Vpp) with low distortion, u ~60.
