Tube Amp Archive

IF you had to make a recomendation to an amateur wanting to get serious ( building and modding tube amps ) for a quality scope, something that will supprt growing interest for a few years, what would it be ?

Thank you very much, that works just fine !

Stevem wrote: ↑Fri Sep 05, 2025 8:34 pm What range of negative voltage do you get out to pin 5 on the tubes ?

-35 to -42

HI all, attached is a pic of the bias circuit ( and around ) of a JTM45 clone built from a Mojotone kit. It came to me assembled and with EL34's, I replaced the OT with a Metro spec 8K primary from Heyboer to use KT66 BUt I cannot bias them, the pot will not allow to go lower than -69 MA @455V plate...

Many thanks !

THis was gifted to me, don't know if it works yet. If anyone knows where I can find the manual, please link it !
THank you !

Thank you !

Eaxtly what I needed !

This one is about the chassis ! I have an amp that was built using "mini fuses" those are very hard to find here. I need recommendations for a tool that would allow me to enlarge the holes in the chassis to install standard size fuse holders. Let me know if this was the wrong place to ask, Thank you !

I've played other JTM45s in the past, with KT66 and much preferred the tone and response. My question was trying to confirm that would be the main explanation for the differences or if there could be other reasons/changes the make the amp different. I like to play "almost clean" to me, that circuit...

Thank you all for the input.
YOu are confirming my impressions. THe orger if going out for a new OT.
My 1st option is to go to heyboer and ask for the "Metro spec" but I am open to suggestion here. Also, if someone has one they would like to sell

Thank you again !

It' seems your staying true to form, in that every time you get something new in front of you, you want to change it . So what is it about the amp as it is now that is lacking in your opinion? I've played other JTM45s in the past, with KT66 and much preferred the tone and response. My question was ...

EL34 or KT 66 ? I just got a JTM45 clone ( built from Mojotone kit ) It uses EL34s and an OT with 3.4K primary I am debating swaping the OT for a Metro spec 8K primary and use KT66s INterested in views, experience and opinions of KT66 vs EL34 with this circuit. WHat to expect in tone, response, POwe...

xtian wrote: ↑Tue Jun 03, 2025 2:31 am

hebaton wrote: ↑Mon Jun 02, 2025 8:42 pmThis unit feels very stiff, I wonder why that would be and what, if anything, I can do to change that ?

What's the value of the first ("reservoir") fitler cap?

I pulled them out, they are both 32+32uf cans. That is not what is expected, in a original JTM45 you would find a 16+16...

The info is not visible the way they are installed. Can they be measured in circuit ?

Thank you ! I will go through it. For some reason, this unit ( I have played JTM45s in the past ) seems very "stiff" I like tube rectified amps because of the chewy response the usually have, due to sag. This unit feels very stiff, I wonder why that would be and what, if anything, I can do to change...