Replacing Valves In An Amp

[Lu_B]

I'm contmplating replacing the vales in my 2/3 year old Ashdown Peacemaker as its got a bit buzzy and I noticed the other day a ringing sound, rather like when a light bulb hass blown and you shake it (this went after a bit).

I have four questions that I hope someone can give me a little guidance on

1. should I replace all the valves (pre amp 12AX7 and power EL84) all at once?
2. which valves do I need to buy in matched pairs?
3. I'm thinking of buying JJ Teslas (its got Electro Harmonics in at the moment) are these any good?
4. how easy are these things to change, can I do it myself or does it need to go to a tech?

Cheers

Lu_B

 

[Simon_F]

Re: Replacing Valves In An Amp

1. You should replace all the power valves at the same time, doesn't matter about the pre-amp valves.

2. The power amp ones

3. I've used those in the pre-amp and I like them - smooth and warm. Everyone has different opinions on what brands to buy!

4. Changing valves is easy, like changing light bulbs, though I've heard you should try to avoid touching the glass as this can create hot spots. I'm sure I've touched the glass when changing mine. However, when you replace the power valves the amp's bias should be checked and set. Depending on your amp and your experience this might be a job for a tech.

 

[Lu_B]

Re: Replacing Valves In An Amp

Cheers for the tips

 

[Jeffrec]

Re: Replacing Valves In An Amp

I'm contmplating replacing the vales in my 2/3 year old Ashdown Peacemaker as its got a bit buzzy and I noticed the other day a ringing sound, rather like when a light bulb hass blown and you shake it (this went after a bit).

I have four questions that I hope someone can give me a little guidance on

1. should I replace all the valves (pre amp 12AX7 and power EL84) all at once?
2. which valves do I need to buy in matched pairs?
3. I'm thinking of buying JJ Teslas (its got Electro Harmonics in at the moment) are these any good?
4. how easy are these things to change, can I do it myself or does it need to go to a tech?

Cheers


Lu_B

You can replace them all if you want. I use Groove Tubes, and only the power tubes (EL84s) are matched. It's the same with other companies I'm sure.

Jeff

 

[Otis]

Re: Replacing Valves In An Amp

I'm not familiar with that amp but most amps that use EL-84s are cathode biased which means plug in the new ones and go.

Some amps are fixed bias which usually means adjustable (what do you think of that?) and the bias ought to be set by a tech. I try to teach anybody who brings me an amp how to set their own. It's not hard.

If the microphonic tube noise is rattley and sounds like static, it's usually a power tube. If it's pingy, tinkley or the amp starts singing its own little tune, it's a preamp tube. Turn up the volume and tap on each tube until you find it.

 

[Lu_B]

Re: Replacing Valves In An Amp

I'm not familiar with that amp but most amps that use EL-84s are cathode biased which means plug in the new ones and go.

Some amps are fixed bias which usually means adjustable (what do you think of that?) and the bias ought to be set by a tech. I try to teach anybody who brings me an amp how to set their own. It's not hard.

If the microphonic tube noise is rattley and sounds like static, it's usually a power tube. If it's pingy, tinkley or the amp starts singing its own little tune, it's a preamp tube. Turn up the volume and tap on each tube until you find it.

Thanks for the advice Otis, I'm definately going to try your test to determine which ones need replacing.

I've just looked on Ashdowns website for the spec and it says its Class A Auto Bias - so it looks like I can just plug new valves in and not have to worry about the bias thing.

It also says it has 4 El84 so does that mean that I have to buy a matched quad set?

 

[Gearjoneser]

Re: Replacing Valves In An Amp

My friend, Todd, owns www.revolutionguitar.com He's a dealer for all the best tube companies, and he undercuts the competition in order to gain business.
My personal favorites, for an amp like yours, would be 4 JJ EL-84's and GT12AX7C's.
I'd suggest replacing all the tubes in your amp, since you've had it that long.
Spend the money on those GT'C's. They'll tighten up your pre section, nicely......much better than the JJ 12AX7s.