I am building a valve amp (not my design) which is supposed to have two sets of matched pairs on the output (EL84's), the application is for a guitar amp, can someone tell me how crucial it is that I make sure I use matched pairs and what the result would be if I didn't? Also are there good cheap modern equivalents of the EL84 available (in U.K.)?
Many thanks for help
Indy
Many thanks for help
Indy
Watford Valves have 12 different types of EL84 in stock and will match them for you. Just choose some that fit your budget (£7 to £20).
How affected the amp will be by mis-matched valves, depends on the design. Designs with common cathode resistors are most affected.
The Svetlana SV83 is a close cousin, and was available cheaply for a while. Can't seem to find any now.
How affected the amp will be by mis-matched valves, depends on the design. Designs with common cathode resistors are most affected.
The Svetlana SV83 is a close cousin, and was available cheaply for a while. Can't seem to find any now.
JJ Electronic manufaturing EL84. They offer matched pairs. I ordered some KT88s, and EL34s, and the matching was perfect (about 2%)
sajti
sajti
contact info please
Thanks for all your input guys. I have tried to find JJ Electronic manufacturing on the web and/or phone number but I can't find either. Can anyone tell me how to contact them.
thanks
Indy
Thanks for all your input guys. I have tried to find JJ Electronic manufacturing on the web and/or phone number but I can't find either. Can anyone tell me how to contact them.
thanks
Indy
Re: contact info please
http://www.watfordvalves.com/
Better buy from some distributor near you than directly from JJ... also because I think they sell only big stocks.
Indy335 said:
http://www.watfordvalves.com/
Better buy from some distributor near you than directly from JJ... also because I think they sell only big stocks.
2nd (3rd?) the recommendation to to use JJ EL84s and get matched set.
I built a Morgan Jones EL84 Ultralinear Amp a few years back. Started with unmatched Sovtek EL84s, changed to matched NOS 6BQ5s and finally a matched quad of JJ EL84s (over a period of about 6 months). The JJ's were clearly the best.
BTW my bias scheme is ring of 2 transistor current source in each cathode (i.e. cathode biased) set to 38mA with 470uF/50V Blackgate Standard bypass caps.
With cathode bias it is very easy to check/monitor the matching - just check the bias voltage developed at each cathode. All of mine are within 0.1V with as typical value of 9.8 Volts.
Cheers,
Ian
I built a Morgan Jones EL84 Ultralinear Amp a few years back. Started with unmatched Sovtek EL84s, changed to matched NOS 6BQ5s and finally a matched quad of JJ EL84s (over a period of about 6 months). The JJ's were clearly the best.
BTW my bias scheme is ring of 2 transistor current source in each cathode (i.e. cathode biased) set to 38mA with 470uF/50V Blackgate Standard bypass caps.
With cathode bias it is very easy to check/monitor the matching - just check the bias voltage developed at each cathode. All of mine are within 0.1V with as typical value of 9.8 Volts.
Cheers,
Ian
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