13 years I would go full scale change...seamoss wrote:well....not sure. None of the tubes have ever been replaced and this amp is about 13 years old.Hink wrote:...but no one has asked the obvious...is this a full scale change ot just power tubes, or jut pre-amp tubes?
the lows are pretty muddy.
guitar, organ, synths.....are some of the things I run through it and I usually run it pretty clean.
I agree with yah ew, but 12ax7's just aren't that expensive so I figure what heck, but you're right they don't take the abuse that the power tubes take...ew wrote:Actually, besides the first gain stage (the preamp tube next to the input jack), preamp tubes usually DON'T go bad. If you aren't getting any microphonics, I'd skip them. However, DO replace the phase inverter/driver tube (the one nearest the power tubes) whenever you replace the power tubes.
ew
12AX7s can last 2000 hours or more - it really depends how much use/abuse they have had. If you swap one out and the amp sounds better then it is worth doing - if not why not save the bux? If you are paying for someones time there may not be much financial advantage in trying to eke out some extra life from an old tube.Hink wrote:I agree with yah ew, but 12ax7's just aren't that expensive so I figure what heck, but you're right they don't take the abuse that the power tubes take...ew wrote:Actually, besides the first gain stage (the preamp tube next to the input jack), preamp tubes usually DON'T go bad. If you aren't getting any microphonics, I'd skip them. However, DO replace the phase inverter/driver tube (the one nearest the power tubes) whenever you replace the power tubes.
ew
no james you aren't the only one...I remember when stores had tube testing machines in them...even in drug stores...I also remember the only time I was stupid enough to touch that suction cup looking thing on a picture tubejames0tucson wrote:Am I the only one here who grew up in the era when all TVs and radios had tubes and it was a common thing for the owner to maintain them? I'm amused by the dire warnings about swapping tubes. Yeah, don't ground yourself and touch the plate. Don't work on anything that has a connected power supply. I guess it's hard to be sure caps are discharged. But come on. Generations of folks did this sort of maintenance all the time. Every hardware store would have a tube tester back in the day. We are so spoiled in the solid state era!!!
thankfully it was a black and white tv...still it knocked me on my ass...or do some welding with a screwdriver across the caps (KIDDING it very well might weldto the leads!) i've seen caps in old tvs hold a charge for years, not just 24 hrs...swapping out tubesis not dangerous if you take precautions, much like changing a light bulb could be dangerous...the main reason i'd goto a qualified tech is because there is not one way to set up a twin (i have silver face from the 70's?), an experienced tech will explain the choices in bias (louder and cleaner, dirty and sweet, etc) and maybe let you hear different tubes if they stock them or at least give you advice based on what YOU want, ie, will they listen to you or TELL you what you want...AndrewSimon wrote:Get a power resistor (470ohm or so/5 watts) from Radio Shack.
Unplug the amp from power and short the capacitor(s) leads for 1 second with the resistor (without touching the leads! ehh!)
This will safely drain the caps and you can work on the amp without any worry.
Still worried? Just get rubber gloves.
ross you're talking about very old tvs and the caps you speak of had oil in them, yes 50 years ago caps like that existed but now??????ross g wrote:or do some welding with a screwdriver across the caps (KIDDING it very well might weldto the leads!) i've seen caps in old tvs hold a charge for years, not just 24 hrs...swapping out tubesis not dangerous if you take precautions, much like changing a light bulb could be dangerous...the main reason i'd goto a qualified tech is because there is not one way to set up a twin (i have silver face from the 70's?), an experienced tech will explain the choices in bias (louder and cleaner, dirty and sweet, etc) and maybe let you hear different tubes if they stock them or at least give you advice based on what YOU want, ie, will they listen to you or TELL you what you want...AndrewSimon wrote:Get a power resistor (470ohm or so/5 watts) from Radio Shack.
Unplug the amp from power and short the capacitor(s) leads for 1 second with the resistor (without touching the leads! ehh!)
This will safely drain the caps and you can work on the amp without any worry.
Still worried? Just get rubber gloves.
sorry, didn't mean to talk about old TVs again....Hink wrote:ross you're talking about very old tvs and the caps you speak of had oil in them, yes 50 years ago caps like that existed but now??????ross g wrote:or do some welding with a screwdriver across the caps (KIDDING it very well might weldto the leads!) i've seen caps in old tvs hold a charge for years, not just 24 hrs...swapping out tubesis not dangerous if you take precautions, much like changing a light bulb could be dangerous...the main reason i'd goto a qualified tech is because there is not one way to set up a twin (i have silver face from the 70's?), an experienced tech will explain the choices in bias (louder and cleaner, dirty and sweet, etc) and maybe let you hear different tubes if they stock them or at least give you advice based on what YOU want, ie, will they listen to you or TELL you what you want...AndrewSimon wrote:Get a power resistor (470ohm or so/5 watts) from Radio Shack.
Unplug the amp from power and short the capacitor(s) leads for 1 second with the resistor (without touching the leads! ehh!)
This will safely drain the caps and you can work on the amp without any worry.
Still worried? Just get rubber gloves.
...like you say though, there is no real concern about changing tubes in an amp....I agree with you on biasing, tbh though the only tube change I ever did that didn't sound as good as I hoped was when I put groove tubes in my plexi...and then it was just to bright for me...a plexi's tone controls were not very effective.Submit: News, Plugins, Hosts & Apps | Advertise @ KVR | Developer Account | About KVR / Contact Us | Privacy Statement
© KVR Audio, Inc. 2000-2026
