Amp Qn - sound ok - fizzes / scratchy cutsout then ok?

[sonic66]

Hi, Thought i'd ask this qn here 4 some good answers.

I 've a friends Peavey special 150 which is cutting out. It seems to do it after warming up with the poweramp in  but almost straight away with the normal input. The sounds ok for chords  perhaps a bit muddy but hold a note and as the volume drops the sound becomes scratchy  fizzes and cuts out. it will then kick in again when another note is played and may cut straight back out or be 'ok'.

There is a strange noise that happens when the power is shut off.  Its not the guitar or cords or batteries etc. I'm wondering whether its an opamp ( RC4558P ) dying or need to be reseated, or perhaps the output caps?

Trying a different speaker did seem to make it less obvious - in fact it seem to clear up ( an 8 ohm rather than 4 ohm that it has?) I 'dont know ......?


What would you do to fix it?

(With the usual caveats ie if you don't know what your doing don't doo it 240v , throw it out peavey's rubbish anyway ? )

thanks

[sonic66]

Turns out its the speaker. Anyone know what kind they use? Wired the  lead to a celestion g10s and it sound fine. Also doh! Recorded from the preamp out and it was ok - so it had to be the poweramp part or the speaker / cable .

I had reseated the rc4558's for good measure anyway - guess i' was just looking for somthing to replace.  Can i swap these for another opamp (is it) burr brown? or NE5532 ? i read in another post. Any other suggestions for quiteness?

Speakers - Jenson Webber Celestion Eminance any recomendations for this sort of amp? Is it worth it or sell it maybe?

Thanks

[AL]

That sounds kind of odd. Are you absolutely sure it's not the speaker wire? If it is the speaker an upgrade would definitely help but I don't think you'll get much on a resale deal - for a few reasons:

1) It's a Peavey - they just don't go for much $$$
2) From the sounds of it it is a solid state amp - again, not much $$$ on resale.

If you want to resell it put in a cheap speaker and get rid of it. On average a Weber will run around $100 (give or take a few $$$) and up. Celestions and Jensens are good choices too but what do you want to do with the amp? If you're keeping it AND you love the amp then put in a good replacement. Lots of choices.

AL

[BD13UK]

This sounds like the description of a PV 130 special 1x12 fitted usually with a Scorpion speaker which I believe is either made by PV themselves or made for them by Eminence.

[sonic66]

Yep, its not the speaker wire - i used that to connect to the celestion and there were no problems.. I also used a different amp to drive the peavey  speaker and it happend - so it must be the speaker ( except for the noise when shutting power off).

Yep its transistor, it sounds ok and is very loud. Occured to me that its an oppertunity to kill 2 birds with one stone. My friend plays acoustic and wants an acoustic amplifier. Why not put in a PA speaker or one with a higher roll off and turn it into a keyboard / acoustic amp?add a master volume and notch filter or whatever through the fx loop.

Other thought was use it to test out mini  amps like those on ROG through the poweramp in. Or use it to make louder a small tube amp with preamp out.

any comments.

Thanks for yours