This amplifier was published in the German electronic magazine ELRAD so as in this book: "High End mit Röhren" - go to
High-End mit Rohren. Referenzschaltungen zum Nachbauen: Amazon.de: Gerhard Haas: Bucher
A friend of mine had this power amplifier built by an electronics engineer and stated from the beginning that the life time of KT88 is only a bit longer than a year. Idle current is 40mA and anode voltage aproximately 490VDC.
Schematic is on page 171 from the attached pdf's in German - go to post #2.
I remember a website where the same circuit was published with tweaking notes to extend the life time of that tubes. Unfortunately I don't find it currently. Maybe one of the member will give me some hints or know this website.
Thank you very much.
Copyrighted material removed by moderation
High-End mit Rohren. Referenzschaltungen zum Nachbauen: Amazon.de: Gerhard Haas: Bucher
A friend of mine had this power amplifier built by an electronics engineer and stated from the beginning that the life time of KT88 is only a bit longer than a year. Idle current is 40mA and anode voltage aproximately 490VDC.
Schematic is on page 171 from the attached pdf's in German - go to post #2.
I remember a website where the same circuit was published with tweaking notes to extend the life time of that tubes. Unfortunately I don't find it currently. Maybe one of the member will give me some hints or know this website.
Thank you very much.
Copyrighted material removed by moderation
Last edited:
IMO KT88 Rg1 value is to high (220K) , I will reduce those grid resistors value to be not more than 100K ,but in the same time values of four coupling capacitors need to be raised from 0,22uF to about 1uF,each one to be with 1KV= or more voltage rating ,also check for correct nominal 6,3V filament voltage , and check for bad solder joints on those pcb`s ,specially around tube sockets pins .
This amplifier was published in the German electronic magazine ELRAD so as in this book: "High End mit Röhren" - go to
High-End mit Rohren. Referenzschaltungen zum Nachbauen: Amazon.de: Gerhard Haas: Bucher
A friend of mine had this power amplifier built by an electronics engineer and stated from the beginning that the life time of KT88 is only a bit longer than a year. Idle current is 40mA and anode voltage aproximately 490VDC.
Schematic is on page 171 from the attached pdf's in German - go to post #2.
I remember a website where the same circuit was published with tweaking notes to extend the life time of that tubes. Unfortunately I don't find it currently. Maybe one of the member will give me some hints or know this website.
Thank you very much.
some pictures of the built up amp will surely help, right now we have no clue as to how that amp was built in real life so we can not really help...
The built amp was exactly according the images of the attached PDF. Because this attachment was deleted, I will make pictures with camera next time. Why do you think, you can help, if you check that pictures ?
Online isn't any image of the version with 4xKT88 mono block, unfortunately.
No , claimed output power is 140W per channel , output stage is (PPP) or circlotron configured where four KT88 works in quasi pentode mode and biased very close to B class ,
German magazine Elrad published in 89 conceptually very similar 120W amp , but with self biased OPS and 6x EL34 .Glasboden-Amp mit 6xE34L, von Falk Eichmann
German magazine Elrad published in 89 conceptually very similar 120W amp , but with self biased OPS and 6x EL34 .Glasboden-Amp mit 6xE34L, von Falk Eichmann
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.