Tube condition

[Guido tum SudenKeymaster]

Hi everyone,

I've got the old SPL Channel One: https://spl.info/fileadmin/user_upload/__bilder/Bilder-Archiv/ChannelOne_1500.jpg

Now, I had the situation, that I got a distorted signal when the singer of my band (with a classical (opera) touch in her voice) sang a long, very loud "ah" syllable.
As far as I could see input and output were okay, the compressor didn't go all the way down.

Now, the SPL is approximately 10 years old, although according to the previous owner seldom used.

Is there a chance that I'll need a new tube or should I look elsewhere to find the problem? If so, where?

Guido

[John GleasonParticipant]

Generally, distortion in tube circuits usually comes from over-driving the tube rather than a problem with the tube itself (ringing would probably be the tube). That said, you should really have good quality spare tubes on hand for any tube devices you have (not always available on short notice!). (Price makes a difference on tubes -- the older (new or used) tubes often sound better and command a higher price. Try tubedepot.com but always pay extra for the balanced triodes, low noise and microphonics testing for preamp tubes, if available.)

I would look first at the microphone and the singer's mic technique. If she was too close to the mic during that loud high note that would cause distortion in the mic and/or the preamp.

If the singer is available to help you could ask her to sing into several different microphones using different pres (if you have others) to help you isolate the problem.

Best of luck!

John

[John GleasonParticipant]

Guido, I think SPL sells the replacement tube for the Channel One directly to users -- might be your best bet to keep one on hand. Since the Channel One is still in production ($1400 new in the U.S.), if you are able to isolate the problem to the preamp you might want to give SPL support a call for advice before you replace anything. As I understand the Channel One design, the front end of the preamp is solid-state and the tube is on the back end to add "color." So, IF the preamp is really distorting without being over-driven, the problem could be in the solid-state circuits up front (let's hope not!).

I'm still betting on the mic/mic technique!

John

[Guido tum SudenKeymaster]

Thanks John,

it's probably a mic/voice thing. I'll see if I can find the recording and post a part of the vocal track.
Having a spare tube is probably not a bad idea. I'll ask SPL directly. No problem, since it is a German company.

Guido

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