My KT-88 'Blocks are 5 years old this month
Built as Steve Brown modified in previous pages, triode wired EF-86, no NFB, 275k attenuation on the inputs, and most importantly, new issue Gold Lion KT-88s.
Still making beautiful music and dead quiet. Big thank you to Tube Mack and all those who contributed to the design.
Built as Steve Brown modified in previous pages, triode wired EF-86, no NFB, 275k attenuation on the inputs, and most importantly, new issue Gold Lion KT-88s.
Still making beautiful music and dead quiet. Big thank you to Tube Mack and all those who contributed to the design.
Glad it's still running well
Mine is, too. I originally built mine in a 10x17x2 Hammond steel chassis, but re built them a couple years later like yours. I got rid of the meters on build 2. As you said, dead quiet. I was worried a bit about the Hammond output transformers, but they're really excellent (and heavy).
Mine is, too. I originally built mine in a 10x17x2 Hammond steel chassis, but re built them a couple years later like yours. I got rid of the meters on build 2. As you said, dead quiet. I was worried a bit about the Hammond output transformers, but they're really excellent (and heavy).
I'm looking for a solid push-pull KT88 design and stumbled upon this thread.
I'm on page 38 of 103, still working through it.
2 quick questions --
1) What is the latest version of the schematic? I'm up to draft 5.
2) Was it settled on which is the optimal OPT primary? I don't have any yet so can buy 3.5K, 4.3K, or 5K.
I'm on page 38 of 103, still working through it.
2 quick questions --
1) What is the latest version of the schematic? I'm up to draft 5.
2) Was it settled on which is the optimal OPT primary? I don't have any yet so can buy 3.5K, 4.3K, or 5K.
Way back on post 10: Hammond 1650R 5k - I agree, that's what I used. These guys are big and heavy and do a wonderful job top to bottom. As for latest rev, I think 8? I used the 12AT7's at 3.5ma per tube. I also ended up removing feedback and putting the EF86 in triode, but build it as shown in the latest rev and then modify as you'd like.
Thanks Bill & Steve.
dgta, the latest schematic can be found here: https://www.diyaudio.com/forums/tubes-valves/156699-mullard-5-20-kt88-pp-blocks-81.html#post2124337
dgta, the latest schematic can be found here: https://www.diyaudio.com/forums/tubes-valves/156699-mullard-5-20-kt88-pp-blocks-81.html#post2124337
Itsik,
version 8b may be the last published schematic, but I believe that subsequent changes replaced the ECC88 with 12AT7, as well as wiring the EF 86 as triode. It would be nice if some of the original builders could confirm and detail the changes, or better yet, publish a final schematic
version 8b may be the last published schematic, but I believe that subsequent changes replaced the ECC88 with 12AT7, as well as wiring the EF 86 as triode. It would be nice if some of the original builders could confirm and detail the changes, or better yet, publish a final schematic