5/20 ohm vintage amp

[rinkel]

I recently came across a vintage German amp (1966? Klemt Echolette M120), and had it suped up by one of the best guys around.
You can have the Ohms set to either 5 or 20.
I'm looking for the perfect speaker cab for this amp, and I'm really not sure what Ohm I should be looking for (since, obviously, most are set @ 4, 8, 16...).
Any help with this, or any more info you might have about getting the best sound possible out of this lil' hot rod would be much appreciated.
Thanks!
Dave

[Enzo]

4 amd 16 are quite close enough to 5 and 20. DOn't sweat the difference. Remember, speaker impedance is a point on a curve. The nominal impedance of a speaker is determined at one frequency. But the actual impedance of the speaker varies widely across the audio frequency range. Rather dramatic variations, like as much as 10 to 1. The impedance at 80 Hz will likely be very different from the impedance at 3000Hz. SO unless yuo are amplifying a steady 1000Hz, your 4 ohm speaker is probably something else.

[rinkel]

So how about 8 ohm cab?

I'm looking at a Crate V212T cab with 8ohm alnico tone tubbys. Is this a good idea if I plan on using the 5 ohm setting?
Would it be better to hold out for a 4 ohm cab, or maybe 16 (using the 20 setting)?
Where would any negative side effects occur; in the amp (i.e. shorter tube life?) or the speakers (i.e. getting blown out)?

[stokes]

Using the 8ohm cab in the 5ohm output would be fine.You would probably not even notice a difference with the slight mismatch,like Enzo already pointed out,the 8ohm rating of the speaker is nominal.A mismatch is only "bad" if you put a smaller speaker load,say 4ohm into a larger,say 16ohm output,this makes the secondary run closer to a dead short,makes the tubes run hotter.Reversing the mismatch,16ohm load into 4ohm out would actually make the output tubes run slightly cooler.

[rinkel]

This was my first post here, and you guys are really a huge help!
Thanks!

[Steve Conner]

A 2x12" cab with two 8 ohm speakers in it will be 4 ohms if you connect them in parallel, or 16 if you connect them in series. Either way should suit your amp fine, using the 5 or 20 ohm taps respectively.

[Bernardduur]

Hey all!

I have an Klemt Echolette BS40 that has that same output impedances as the TS's......... The OT is wired up as two parts of 10 ohm taps which are OR in series (20R) OR in parallel (5R).

I wondered; can I wire it up as a 'normal' OT and only use the 5 ohm and for example the 10 ohm out as 4 and 8 ohm outputs???? Or should I keep the wireing close to the original? Is this way of wiring better or just different???

Schematic

[Steve Conner]

Even if you just use one of the taps, the proper load for it is still 5 ohms. There's no way of getting a match to 10 ohms with this setup.

Proof: Impedance goes as the square of the turns ratio, and you can only change the turns ratio by a factor of 2.

[Bernardduur]

True, but this unit also has taps between the 10R parts making it two 5R taps (which are wired in series = 10R)...... or am I really missing something