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serious (but probably dumb) question

1/22/1997 12:37 AM
Hans Vorstenbosch
serious (but probably dumb) question
I bumped in to a really cool amp (Laney VC50), and it sounds great. But I read a review about it that said: "Other goodies at the back include a biasing switch (for 6L6s/5881s or EL34s)...". I'm not such a tech-head, and I don't know what that means. Can somebody explain to me what that means and if I could change the sound of the amp with it? I'm really new with this stuff, so please keep the explaination simple.  
Thank you in advance,  
Hans Vorstenbosch
1/22/1997 3:28 PM
Patrick Freuler

That means you can change the output tubes and adjust the bias by switching to the appropriate position indicated on the switch to match the tubes. Bias voltage on the output tubes keeps the current going though them within certain limits so that the tubes do not overheat and become damadged or destroyed. Different tubes have different bias voltage requirements. Most amp have this adjustment inside the chassis in the form of a variable resistor (like a volume control) and it requires a meter to make the adjustment. Your amp has been designed to accept any of those tubes listed, providing you insure the bias switch is set correctly to match the tube you are using. And yes, their will be a different sound depending on which output tubes you use. They all have certain tone characteristics. Hope that helps explain it.
1/25/1997 12:52 AM
Rainer zur Linde

You have to be very carful with changing output tubes! The 6L6's need 0,9 A for heating, the EL34's need 1,5A for heating. Normally, the mains transforner can't handle 0,6mA mor current for heating (each Tube!)and it cann damage.  
1/27/1997 12:48 AM
david coletta
those little switches control the bias of tubes the numbers you gave are  
tubes check a manual or contact the manufacturer i wouldnt play around  
with them if your item functions okay.
1/27/1997 12:43 AM
John Martin

Don't worry about changing tube types, the amp was designed for it. Just make sure you select the right switch setting. I always prefer the sound of the EL34 tubes in those UK amps. It seems they were designed around EL34 in the first place.  
JM out

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