tubes

[aero_91]

im not sure if this question had been asked before, so do help me with this.

i went around looking for tubes for a Marshall 2245 JTM45 head. and i found out that there are 2 different types of EL34 tubes.

So came my first question.
can the tubes on the head, for preamp ECC83 and poweramp 5881 be replaced by the EL34s? Whats the difference?

Then came number 2.
Whats the difference between QUAD tubes and DUET tubes?

Thanks in Advance!

 

[jskadiang]

if i'm not wrong quad and duet tubes means 4 matched tubes and 2 matched tubes respectively, calibrated to work optimally with each other. also, if you replace the tubes in your amp with a different kind (e.g. ECC83 to EL34s) you'd need to rebias the amp. not the expert on that so someone else on the forum might be able to help you with that.

 

[aero_91]

anyway, whats preamp for? i still dont really understand the difference. im still looking for advice on the 2 questions.

 

[PatheinRaindropMoe]

try asking over at marshall amp forum. They shud be able to help.

http://www.marshallampforum.com/forum/
http://www.marshallforum.com/

 

[Weiht]

quote: if you replace the tubes in your amp with a different kind (e.g. ECC83 to EL34s) you'd need to rebias the amp

ECC83 are preamp tubes which can be swapped to any other preamp tubes for ur own preference, but EL34 are powertubes which after changing needs to be biased. Note, u cant change a ecc83 to el34

Also it often safer not to change the type of powertubes in most cases, altho there are amps made nowadays that u can interchange between a 6l6 type of sound to a EL34 type. There are also "compatible" tubes ie EL34 and KT77, or 6l6 and 5881 etc.

For ur case, i dun think u can fit el34 into the JTM. Stick with the 6l6 type which it was build for, and thats also the reason why ppl buy the amp in the first place.

 

[Benster]

sorry double post

 

[Benster]

im not sure if this question had been asked before, so do help me with this.

i went around looking for tubes for a Marshall 2245 JTM45 head. and i found out that there are 2 different types of EL34 tubes.

So came my first question.
can the tubes on the head, for preamp ECC83 and poweramp 5881 be replaced by the EL34s? Whats the difference?

Then came number 2.
Whats the difference between QUAD tubes and DUET tubes?

Thanks in Advance!

Good day,

you can use any combination of the ECC83/12AX7 family of preamp tubes in the preamp section. its cool to experiment with different preamp tube gain structures (preamp section needs no rebiasing)

besides the stock 5881's that come on the JTM45 you can use 6L6, KT66 power tubes in the JTM45. they are in the same family. they all sound different. you just need to rebias the amp accordingly for each type. (better get a qualified amp tech who knows what he is doing, to do this). doing this WILL NOT spoil the amp provided it is rebiased properly.

i'd try the KT66 for the vintage 'bluesbreaker' kind of tone..

you can also use EL34's if you change out the screen grid resistors (mod it).. but as Weiht said, that defeats the purpose of getting a JTM45.. which is a very specific early period non-EL34 marshall tone.

DUET means the 2 tubes in a matched pair. QUAD means 4 tubes in a matched quartet.

you can find out more/ask more over at

http://www.amptalk.com/message-board-forum/

or

http://www.thegearpage.net/board/forumdisplay.php?f=11


hope this helps..