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boneshaker 9th April 2006 07:10 PM

Which components should be matched?

I am going to build my first audio amp (but I built several guitar amps): the WAD KEL84 ( It is a simple Push-Pull EL84 amp.

Which components should be matched in such an amp (in a guitar amp this is not necessary).

I am asking because there is a guy selling stereo volume pots that are selected for minimum tolerance (so that the 2 channels are identical as much as possible to one another).

Does this make sense? (Especially since the tubes used in the 2 channels will vary anyway.)

Are there other critical componentes that should be matched, too, to make the two stereo channels of the amp as identical as possible?

(I was going to use resistors with 1% tolerance, BTW.)


kevinkr 10th April 2006 02:38 AM

Actually this does make a lot of sense as tracking between sections in stereo pots is often as bad as 3dB section to section. This results in possible fixed level mismatch between the channels over most of the control's range as well as a possible variation in mismatch between the channels as you change the setting of the volume pot.

Triodes have pretty consistent mu, and hence voltage gain, provided that the passive component values are reasonably well matched from channel to channel.

1% resistors are fine, in most instances 5% resistors are ok too if you wish to use vintage allen bradley carbon comps for example.

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