Preamp Tubes

[nonamemx]

How do you know when your PREAMP tubes are worn out?

I know what to look for in Poweramp tubes, but how do you know when preamp tubes are tired and done for?

Like, what kind of symptoms?

Thanks.

[Cleveland Metal]

Re: Preamp Tubes

Usually a fair sign they are on the way out is that they get microphonic. If you tap them while the rig is turned on, you will hear it through speaker fairly loudly. Bear in mind that even the best and newest tube may exhibit "some" slight thumping noise when tapped if they are in the high gain stages though.

[VomiT]

Re: Preamp Tubes

Yeah, also since you're talking about the pre-amp tubes you'll notice lower gain then usual - the distortion will sound different, flat etc. Also when you change your tubes make sure you buy them in pairs - don't remember why [img]/images/graemlins/smile.gif[/img]

[nonamemx]

Re: Preamp Tubes

lower gain? flat?

Yup, theyre dying. Its got these anchient Sovteks in there, so old that I accidently whiped off the writing when I touched them.

Because I played a JCM 2000, and it had more of a snarl than my JCM 800, so I KNEW that SOMETHING was terribly WRONG [img]/images/graemlins/laugh.gif[/img]

[Cleveland Metal]

Re: Preamp Tubes

Yeah, I forgot to mention that. Also, as the tube gets microphonic, you will often hear a noise (static or rumble) through the speakers that will follow the the picked notes as well.

You can replace preamp tubes however you want, if one is bad you can just replace it. I will often just clean house and replace them all myself as I figure if one is going bad, the others may be on their way out as well. But not necesarily, if they are all fairly new and one is screwing up, just replace it. If they are all old (several years), clean house . However, this concept doesn't quite apply to NOS boutique tubes (mullards etc) as they can last for a VERY long time, as in many many years if not the life of the amp..

No real reason to by preamp tubes in pairs, you're probably thinking of power amp tubes. And power amp tubes should actually just all be replaced at the same time, as they operate as team of sorts. But yes minimally in operating pairs if you are truly pressed for dough.

[Cleveland Metal]

Re: Preamp Tubes

And yes, if the 2000 sounds better than the 800, you have a problem, haha... [img]/images/graemlins/wink.gif[/img]

[VomiT]

Re: Preamp Tubes

preamp tubes in pairs (or all)... there ya go... I'm geting senile hehe

[GodWentPUNK]

Re: Preamp Tubes

Check out eurotubes.com. I got some ECC83S for my Marshall. Also, you'll need to purchase 1 balanced ECC83S in the phase inverter hole which the one next to the power tubes.

joe...

[Fragle]

Re: Preamp Tubes

aren't they all balanced? i remember buying a full set of 4 JJ ECC 83S tubes and they were all balanced..afaik they didn't even have "normal" unbalanced ones...but then again, i didn't buy from eurotubes

anyways, JJ tubes are great, especially the preamp ones. great to tame overly treble heavy amps. today i swapped the stock mesa preamp V1 tube in my DC5 for one of the JJs and the sound improved 200%, so they seem to work equally well with mesas. electro harmonix' are said to be great tubes, too....i'm going to try them out soon.
i remember having some sovteks in my laney and they sounded fuzzy.

just some random thoughts...

[nonamemx]

Re: Preamp Tubes

Well, I thought that they were going out, and I knew that they were of questionable quality, and I have no clue how old they are. The EL34's are marked only as "Electron Tube" [img]/images/graemlins/laugh.gif[/img] The preamp tubes are Sovteks 12AX7s. OLD!

I actually ordered some JJ's from Eurotubes last week, and they arrived today!

I got a matched set of EL34L's (the L's have increased bass response and more complex harmonics)

2 "High Gain" rated ECC83S for the preamp. They will supposively give me a fatter, thickers sound and will drive 10% more than your normal ECC83

and a Balanced ECC83S for the Phase inverter.

So, im set for a while. I cant WAIT to hear this, Ive never heard my JCM 800 with decent tubes!

I heard Electro Harmonix were relabeled Sovteks. Dunno if this is true or not, but its what I heard. I have 3 EH 12AX7s lying around, from when I retubed my Classic 30. I retubed it with Groove Tubes, which I heard were also Sovteks.

[GodWentPUNK]

Re: Preamp Tubes

I got the same EL34L's and ECC83S. I am very happy with them especially for the price.

joe...

[rodrigo_echeverri]

Re: Preamp Tubes

This is what I dont get!...

Preamp tubes