Recent Posts

61

Tube Amp Building - Tweaks - Repairs / Re: Hum and Buzz in Cordovox Build

« Last post by shooter on September 03, 2025, 06:57:53 pm »

you need to "standardize" your hums n noises


ie;
I have 60hz hum
I have white noise


otherwise I just glaze over thinking about the humming bird that buzzed me the other day and the noise the wings made 


I think you're fighting on 2 fronts, maybe 3 but

62

Tube Amp Building - Tweaks - Repairs / Re: Questions about Rehabilitating a 65 Super Reverb

« Last post by tubeswell on September 03, 2025, 05:27:10 pm »

See Fig 4-4 on P57

63

Tube Amp Building - Tweaks - Repairs / Re: 5879 tube data sheet question

« Last post by Jonas on September 03, 2025, 04:23:52 pm »

i also love this tube. Why is 12.6 v heater operation not listed? I looked at a few other pentodes which only show 6.3v option in the TDS? 

64

Tube Amp Building - Tweaks - Repairs / Re: Hiwatt DR103 FX loop

« Last post by wavley on September 03, 2025, 03:43:24 pm »

Sorry to dig this one up.

I like the version of this that's simple basically interrupting the signal path, I also see a version around with the unused triode as a makeup gain stage.  I usually use that triode as a plate mixer.  I never really use effects loops and would like to keep my knob and switch count down. 

Does this amp really even need make up gain? How has the super simple version worked for the folks that tried it.  Would I be better off ditching my plate mixer in favor using that triode's cathode to drive my send?

Thanks for your input.

65

Tube Amp Building - Tweaks - Repairs / Re: Hum and Buzz in Cordovox Build

« Last post by scstill on September 03, 2025, 03:40:59 pm »

Just some things to check:
check continuity form Signal 5 to B7 on 9 pin connector
Try disconnecting NFB
Check continuity on V2a from junction of 1m & 1.2K resistors to G4 Ground

Continuity check; checked all resistors on V2, all check fine. Voltages check fine too.
Disconnect NFB - when disconnected noise gets slightly louder

Interesting that even when removing preamp tube V1 the noise persists implying it is in power tube section
But with V1 removed MV controls the noise volume which implies kin the preamp section ???

66

Tube Amp Building - Tweaks - Repairs / Re: Questions about Rehabilitating a 65 Super Reverb

« Last post by tubeswell on September 03, 2025, 02:56:19 pm »

Test the 20nF coupling cap in the vibrato channel for DC leakage.

67

Tube Amp Building - Tweaks - Repairs / Re: I'm writing a new book - suggestions?

« Last post by Sonny ReVerb on September 03, 2025, 02:40:02 pm »

hopefully in large print :-)

I'd bet more readers will have gray hair than not   
Looking forward to the book, Merlin!

68

Tube Amp Building - Tweaks - Repairs / Re: Bias Wiggle Tremolo with 7591?

« Last post by Sonny ReVerb on September 03, 2025, 02:11:40 pm »

I used a Princeton Reverb trem with a 7591 PP fixed bias power section. It works very well.

69

Solid State / Re: Unfamiliar with solid state amps, so maybe a dumb question...

« Last post by scstill on September 03, 2025, 02:03:01 pm »

That's what AI does, it "steals" knowledge... but its good that it shares, maybe the credit should be provided. Its very easy for me to find info via AI.

In the AI thread on this forum we talked about what happens when AI runs out of info, do they create new knowledge or just repurpose old info.

70

Other Topics / Re: Anybody watching Gold?

« Last post by EL34 on September 03, 2025, 12:50:41 pm »

Gaps always get filled, so there will be some of that going on