| Indy335 |
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 |
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| audiousername |
The EL84 is still in production in Russia and a few other places. If you're looking for rather cheap ones, this may be a start.
How utterly crucial matched sets are will somewhat depend on the bias scheme. Do you have a schematic you can share with us? |
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| Bas Horneman |
| quote: | | tell me how crucial it is that I make sure I use matched pairs and what the result would be if I didn't? |
Sounds worse if you don't have good balance. |
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| dhaen |
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. |
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| sajti |
JJ Electronic manufaturing EL84. They offer matched pairs. I ordered some KT88s, and EL34s, and the matching was perfect (about 2%)
sajti |
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| SY |
| Second on the JJs. Relatively inexpensive, good matching. |
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| Indy335 |
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 |
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| Giaime |
| quote: | Originally posted by Indy335
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 |
http://www.watfordvalves.com/
Better buy from some distributor near you than directly from JJ... also because I think they sell only big stocks. |
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| dhaen |
| World Audio Design have some JJ EL84's at £5 each here but not matched, I'm afraid. |
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| SY |
| In the US, I buy these from Triode Electronics. Ned is a good guy to deal with. |
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| Bas Horneman |
| quote: | | In the US, I buy these from Triode Electronics. Ned is a good guy to deal with. |
Seconded. Also for Europe! |
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| gingertube |
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 |
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| Indy335 |
Thanks Ian,
I'll give the JJ's a go.
Indy |
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