EL84 matched pairs

[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

 

[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?

 

[Bas Horneman]

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.

 

[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.

 

[sajti]

JJ Electronic manufaturing EL84. They offer matched pairs. I ordered some KT88s, and EL34s, and the matching was perfect (about 2%)

sajti

 

[SY]

Second on the JJs. Relatively inexpensive, good matching.

 

[Indy335]

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

 

[Giaime]

Re: 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

http://www.watfordvalves.com/

Better buy from some distributor near you than directly from JJ... also because I think they sell only big stocks.

 

[dhaen]

World Audio Design have some JJ EL84's at £5 each here but not matched, I'm afraid.

 

[SY]

In the US, I buy these from Triode Electronics. Ned is a good guy to deal with.

 

[Bas Horneman]

In the US, I buy these from Triode Electronics. Ned is a good guy to deal with.

Seconded. Also for Europe!

 

[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

 

[Indy335]

Thanks Ian,

I'll give the JJ's a go.

Indy