Re: [Harp-L] Multi-amplifier



You asked:
Q:But what's the risk of putting a 3 ohm speaker on an 8 ohm amp
A: It's "kinda" like a small short circuit, The tubes and transformer have to dispate the energy gemerated. I do not recomended it.


Q:could an 8" 4 ohm speaker (be wired in *series* with the 3 ohm?
A: Yes, that is a good solution. You could also opt for a resistor in series. If the speaker is truley a 3 ohm speaker, ( dc ohm resistance measurements may not equal audio signal resistance/impedance), then a 4 or 5 ohm resistor would work well. I would recomend the resistor be a 25 watt or greater size. ( that is 5 times the expected power dispated of about 5 watts of a 9 watt amp)


Jim Rumbaugh


----- Original Message ----- From: "geoff atkins" <geoffatkins@xxxxxxxxxxxxxx>
To: <harp-l@xxxxxxxxxx>
Sent: Monday, December 14, 2009 1:30 AM
Subject: [Harp-L] Multi-amplifier



Advice please.
I just got my new amplifier yesterday,.. we are "nearly there".
It has a coke bottle rectifier, DC heaters, a couple of ECC83 preamp tubes,
separate bass mid and treble controls, and two class A-b outputs:
one is a single ended 6V6 (~5W) and
the other is twin EL84 's in push pull (~9W).
Problem:
I have narrowed the 12" speaker choice down to two: an 8 ohm HandH 35year
old (~50watts), and a German 3 ohm veteran from the late 30's (~25 watt
handling capacity). The output transformers are designed for 8 ohms.
The German 3ohm speaker sounds wonderful, -even without a cabinet!
But what's the risk of putting a 3 ohm speaker on an 8 ohm amp?
What blows first, speaker, output transformer or tubes?
"I won't play at full volume".. not for the first week anyway.


Option: could an 8" 4 ohm speaker (be wired in *series* with the
3 ohm? and would the speakers then interfere with the signal getting to the
other?




Geoff Atkins

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