Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on November 30, 2010, 05:33:11 am
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I get this mixed up all the time...
A 6V6 pushing an OT with 9K primary, secondary 8 ohms into an 8 ohm speaker.
Switch out the 6V6 to a 6L6.
What secondary (16 ohm or 4 ohm) do I use to best match the 6L6 with the 8ohm speaker?
Thanks!
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I've used a 16 ohm with 5881/6L6 with an Emminence 8 ohm speaker for a number of yrs now & it sounds fine to me.
Hopefully someone will chime in that actually knows if that's correct.
With respect, Tubenit
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Your OT has a 9K primary??
Actually the tone is not the issue. The amp sounds great with any impedance choice.
Just looking for the "proper" match. Thanks!!
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Sorry about that. No, the OT primaries on the two amps I've done this with are 6.6k & 7.6k.
With respect, Tubenit
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4 ohms.
If you pulled two tubes out of a twin reverb, you would run an 8 ohm load. Same if you replaced all 4 6l6's w/ 6V6.
You are going the other way. So, 8 ohms for 6V6's becomes 4 ohms for 6L6.
Dave
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A 2:1 or 1:2 mismatch is considered generally acceptable: e.g.: 4Ω speaker off an 8Ω tap, and vice-versa. Caveat: Marshal's are said to be particularly fussy about this. My SF Princeton was hotrodded with 6L6's, which mismatches the primary OT 1:2; this makes the 8Ω secondary 4Ω. It drove an 8Ω speaker. Another 1:2 mismatch on the secondary side. It worked fine for hours on end, and sounded so good someone insisted on buying it. I A/B'd 4Ω vs. 8Ω impedances with an impedance matching tranny to convert the now 4Ω tap to 8Ω, to match the speaker. It sounded good, though a little different, either way.
Ditto to Dave arithmetically. A tranny performs simple arithmentic. (How it does this and proper design are too complex for me, but the result is simple). 6L6's have 1/2 the plate impedance of 6V6's. So, if you halve the impedance on the primary side then you automatically halve the impedance on the secondary side. The 8Ω tap becomes a 4Ω tap.