Tube Amp Archive

So whenever I rape my own amp for a build or a friend donates their old broken combo to me, I always inject a fairly small ac voltage into each secondary tap, measure and record the primary voltage, then calculate the winding ratio, then the impedance ratio and divide that into various primary impedance's to determine what the tap impedance's would be for various power tube configurations.

But, I haven't the slightest idea if there is any difference in sound/performance/feel should there be an 8 ohm speaker on the 8 ohm tap or, a 16 ohm speaker on a 16 ohm tap of the same model and age speaker. I have occasionally heard people claim that it is optimum to use the whole OT secondary coil if at all possible.

I would be really curious to hear from those that have actually experimented with this to the point that they were thoroughly convinced that they either experienced a difference or not. I suppose the reason I ask is that when the time arrives to purchase a speaker for a project and I have the choice of matching the speaker to a particular tap, that a decision could lean on a collective opinion that it makes a difference or that it doesn't. If it was looking like the mass opinion was that it made no difference then I'd probably get an 8 ohm speaker just because it seems to be the most nominal impedance in my head. Ha. But, if many experienced players or amp guys swore up and down that there was some sonic benefit to getting a 16 ohm so to use up the whole darn OT secondary coil, well, thats no skin off my teeth either. I personally really don't care what speaker impedance I get if I have the tap to match it and its looking like there is no difference in the "coil real-estate" that is used, and it isn't more expensive for nothing.

Thanks all,
Best,
Phil D.

if in doubt use full secondary, otherwise you can have ringing on square wave (but not important in guitar amp world at all, cause all imperfections in transformer are usually good thing)

Thanks bepone, and sure, I don't mind corrupting a square wave here and there! I'll just say, "Hey man, that's my sound".

And this is really mostly curiosity driven, I have no worries either way no matter what. I'm 64 now and have been trying different speakers since I've been 13, never a complaint about my amps sound.

But, like I posted, if enough people made a strong claim of even a minuscule "improvement" on tone or sound, then its easy enough to pick up a 16 ohm speaker and use the whole tap. I suppose it might be more practical to buy an 8 ohm, because then, if I ever used an extension cabinet that was 8 ohms then I would plug both of those into a paralleled pair of jacks from the 4 ohm tap.

I'm not too worried about it - just very curious.

Thanks,
Best,
Phil D.