Hiwatt Lead 50 Head

kieranmay1

New member
I've recently ordered a Hiwatt Lead 50 head since I saw it for a great deal on Ebay, I was just wondering if this head is self biasing or not, thanks.:)
 
Re: Hiwatt Lead 50 Head

Most likely fixed bias, so swapping tubes would need a trip to a tech to bias them properly.
 
Re: Hiwatt Lead 50 Head

How does a tech set the bias on a fixed bias amp? Just wondering.

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Re: Hiwatt Lead 50 Head

^^
Thus my question.

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Re: Hiwatt Lead 50 Head

How does a tech set the bias on a fixed bias amp? Just wondering.

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As has been said: fixed bias doesn't mean "non-adjustable". Most fixed bias have a variavle resistor (pot) to adjuste the bias current. Mesa are an exception as they "fixed" their fixed bias, to make sure you use tubes that complement your amp properly (i.e. sell you their tubes).
 
Re: Hiwatt Lead 50 Head

How does a tech set the bias on a fixed bias amp? Just wondering.

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There's a few different methods of actually doing the adjustment, but the basic procedure is using a potentiometer in the amp that sets the bias voltage to the power tubes. Using a multi-meter, possibly a bias probe type device. Some amps do not have a potentiometer to allow that adjustment, and often can be modified to have them.

Fixed bias just means it's set and doesn't change, generally; whereas cathode bias is set by the tube through a different sort of arrangement that is not necessarily fixed.
 
Re: Hiwatt Lead 50 Head

Ah, now I get it. I was wondering because I have an old Carvin x amp and when I changed the tubes out a few years back and went to set the bias, I discovered that it didn't have any sort of pot, just a resistor. Now that it's getting time for another re-tube, I figured I would ask how one should go about setting the bias in such a case.

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