Tubes

[deanbean502]

How easy is it to replace the tubes within a head?

and more to the question why would you upgrade from stock tubes?

answers on the back of a postcard

[icastle]

[quote name='deanbean502' post='1208691' date='Apr 22 2011, 09:50 PM']How easy is it to replace the tubes within a head?

and more to the question why would you upgrade from stock tubes?

answers on the back of a postcard[/quote]

Dead easy - they just pull out of the sockets.

As to why you'd want to do this... well the obvious answer is to replace dead valves but some people reckon that changing valves for other makes/equivalents makes a difference to the sound.

[Mr. Foxen]

Preamp valves are easy, power valves are a little more involved for best effect, they need matching in balanced pairs and biasing for best performance. Stock tubes/valves tend to be budget based economic choices, depending on the sort of preamp, they can make a pretty big difference, the biggest difference commonly encountered is swapping lower gain valves into an Orange Terror Bass so you can get clean sounds from it, those are preamp ones and dead easy.

[Dood]

[quote name='Mr. Foxen' post='1208798' date='Apr 23 2011, 12:07 AM']Stock tubes/valves tend to be budget based economic choices, depending on the sort of preamp, they can make a pretty big difference.[/quote]

+1 there!

[voxpop]

If you are talking about the little bastard in your signature, just undo the 4 bolts from the side and loosen the 4 bolts on the handle and the whole amp will slide out of the case.
I found the little bastard has to much gain on the input and will distort with most basses. If you want to clean the sound swap out the two ECC83 valves for ECC81's.

ECC83 or 12ax7 have a gain of 100

ECC81 or 12at7 have a gain of 70

ECC82 or 12au7 have a gain of 20

[url="http://thetubestore.com/gainfactor.html"]http://thetubestore.com/gainfactor.html[/url]

hope this helps.

Edited April 23, 2011 by voxpop

[deanbean502]

[quote name='voxpop' post='1209254' date='Apr 23 2011, 04:00 PM']If you are talking about the little bastard in your signature, just undo the 4 bolts from the side and loosen the 4 bolts on the handle and the whole amp will slide out of the case.
I found the little bastard has to much gain on the input and will distort with most basses. If you want to clean the sound swap out the two ECC83 valves for ECC81's.

ECC83 or 12ax7 have a gain of 100

ECC81 or 12at7 have a gain of 70

ECC82 or 12au7 have a gain of 20

[url="http://thetubestore.com/gainfactor.html"]http://thetubestore.com/gainfactor.html[/url]

hope this helps.[/quote]

very informative voxpop i will take a look, thank you

[paul_5]

+1 for checking the biasing of power amp tubes. Preamp stuff is just 'take one out, pop another one in' but Power amp tubes are a bit more tricky and I'd recommend getting an experienced tube-head take a look before you power it up. Preamp tubes make a world of difference though, so I'd start with that if you're looking for less gain / warmer sound etc...

[jensenmann]

I´d always check microphonics when swapping tubes. Especially when the amp is exposed to vibrations like being placed on cabs. Put the new tube in it´s place, give the amp a minute to warm up and carefully knock with the rear of a screwdriver on the bulb. Compare what you hear from different tubes and use the one with the lowest noise. Microphonic tubes will smear the sound in a very unpleasant way.

[Mr. Foxen]

[quote name='jensenmann' post='1211864' date='Apr 26 2011, 06:11 PM']I´d always check microphonics when swapping tubes. Especially when the amp is exposed to vibrations like being placed on cabs. Put the new tube in it´s place, give the amp a minute to warm up and carefully knock with the rear of a screwdriver on the bulb. Compare what you hear from different tubes and use the one with the lowest noise. Microphonic tubes will smear the sound in a very unpleasant way.[/quote]

Plastic or wooden chopstick is best, metal things can neatly connect you to the plate voltage if the glass breaks. Also, all valves are microphonic to an extent, you just want to ensure the most microphonic has the least gain after it, in an amp with cascading gain stages, the subsequent gain stages will amplify the noise coming through, so you might think that first valve is really microphonic, but it is actually the subsequent ones making the noise louder. It only really becomes a problem if you are in the habit of jabbing the inside of your amp whilst playing, or it is so microphonic it feeds back, if your amp is actually vibrating much, the problem is probably that your cab is flimsy.

[jensenmann]

or an SVT 8x10

[Slipperydick]

[quote name='jensenmann' post='1211864' date='Apr 26 2011, 06:11 PM']I´d always check microphonics when swapping tubes. Especially when the amp is exposed to vibrations like being placed on cabs. Put the new tube in it´s place, give the amp a minute to warm up and carefully knock with the rear of a screwdriver on the bulb. Compare what you hear from different tubes and use the one with the lowest noise. Microphonic tubes will smear the sound in a very unpleasant way.[/quote]

As above, plus check for dirty or corroded pins or valvebases. Waggle the pre amp valves in their bases by gently rocking them with an index finger on the top pip. Any crackles and pops can usually be cured with a little switch cleaner on the pins.