Distorted, scratchy vocals from tube amp

i recently picked up a used Jolida Fusion 3502 S and i’m noticing scratchy/distorted sound especially on vocals (yes sibilance included but all vocals sound like the person speaking/singing has a congested throat).

i’ve isolated this to the amp by trying different turntables, different carts, different phono stages, switching to digital, and even using different interconnects.

the auto-bias indicators for each tube seem fine (light up solid red), but would this be a sign my tubes need replacing? or is there something else i can check/test?

many thanks

 

I'll bump it for you in case someone knows. I don't have much experience with valves but I thought generally the sound starts to vanish, get very dull or noisy when valves need replacing, distortion might be another problem.

 

Could be a wire coming loose in the amp's chassis somewhere. If so, a simple resolder would likely fix the problem.

 

Try the easy stuff first. Pull the output tubes and clean the pins and sockets, and clean the connectors on the back as well. If the volume pot is scratchy, try and get some Deoxit into it as well. Hopefully, the auto-bias is working correctly.

jeff

 

any advice on how to clean those pins?

 

Contact cleaner and a Q-Tip.

 

How many hours are on those tubes?? Most likely too many. I would replace the tubes from a good dealer like Jim McShane, who tests the tubes he sells, so you should have good tubes to install. Cleaning is fine, but it ain't gonna do nothin' for bad tubes.

 

No. There is problem you have not discovered.

 

You could just move the tubes in and out which would clear up some oxidation. Still, don't be cheap and replace the tubes.

 

You could be right but replacing the tubes is the first step. Any repair technician will tell him the same thing.

 

found out yesterday the tubes have 4-500 hours on them. power tubes are electro harmonix EL34s, pres are tung sol 12AX7s.

i suppose next month i'll swap out all 8 tubes and report back. and i'll check out Jim McShane, thanks for the referral.

but assuming the new tubes act the same... any advice on what to do then?

 

If the tubes are not the problem then you should contact the manufacturer and inquire about service.

 

well i’ve bought a whole new set of tubes, no improvement, and the guys at Jolida are also at a loss. my next step is to ship it to Jolida unless anyone knows of any reliable repair shops in the NYC area that could look at this type of thing (Jolida said they didn’t know of any)?

 

Have you tried using Google?
I've just pulled in a list as long as my arm.
Don't rule out guitar amp repairers either.

 

Have you tried another amplifier?
You might have a speaker problem.
In the same vein, have you tried different speakers?

 

What speakers is the tube amp driving?
The Klipsch Heresy speakers on your profile information?
Have you made sure the speakers impedance and watts rms match with the amp?
If you’re driving other speakers especially things like Magnepans or electrostatic speakers, you might need an impedance matching transformer.

 

@SeeDeeFirth ive used a different amp with the speakers and haven’t had the issue. the key word i came to the forum for instead of google was “reliable”. given the amount of tube amp owners on this forum in NY/NJ/CT, i was hoping someone had a recommendation. or that a tube amp repairman themselves would come across my post.

@Oelewapper i haven’t done that - yes they’re the heresys from my profile - i’ll look into that, thanks

 

Jolida are usually very good (and responsive) about fixing their gear. I had a Jolida amp struck by lightning that they repaired after which it worked good as new.