🚀 go-pugleaf

In article <Bz0GpF.Fyn@hfglobe.intel.com> dcovell@hfglobe.intel.com (David Covell) writes:
>
>I recently bought an old tube hi-fi amp that I'd like to cannabilize for
>parts with which to build a project guitar amp. Several people have told
>me that hi-fi output transformers aren't suitable for instrument amps.
>I'd like more data on this; if the problem is that hi-fi output transformers
>can't handle the saturation that guitar amps put out, can I avoid this by
>using output tubes of lower power? 

    From what I understand the problem is the other way around.
Guitar amp xformers are crappy by hi-fi audio standards.  Harry Kolbe
of Kolbe Soundsmith in NYC told me Marshall xformers in particular
are really awful from an audio standpoint.  (This in relation to
discussion of why Power Soaks are so evil.)

>The amp uses a pair of 6L6's in each
>channel. Is there some reason I couldn't use EL84's or 6V6's, which would
>cut the power by at least 40%? This would avoid output wattage in excess of
>the transformer's rating, which is the only potential problem I can see with
>using these transformers. Am I missing something obvious here?

    Check that the smaller tubes can handle the plate voltage the xformer
was providing to the larger tubes.  RCA Receiving Tube Manual says
6L6 can take 360 volts (design centre), or 500 volts (design maximum)
at the plate.   6BQ5 (EL84) says 300V design centre; it doesn't
list design max.  You'll want to check plate (and grid etc.) voltages 
that the circuit you're using is providing.

    I've been thinking of building/converting an amp to EL84 too...
...dare I hack on my nice old Marshall?  :-)


-----
Robyn  Landers
rblanders@math.uwaterloo.ca
	"I'm just doing my rock'n'roll duty." -- Dubois