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Biamping with tubes and SS: Input sensitivity key?

When biamping a low sensitivity speaker (85db), 4 0hm impedance, with a 800 Hz crossover with a TAD-60 (input sensitivity given as 1 volt or more) and, eg, a Belles 150A reference, with an input sensitivity of 1.4 Volts, and a volume control on the TAD, will it be necessary to get an attenuator on the inputs of the SS amp to equate the 2, since adjusting the output of the TAD will still make it less than the higher powered amp? Is 60 WPC tube power enough to drive the major energies above 800 Hz, which is where mid-range and highs predominate? Is this correct or is there another way of attenuating the input of the higher powered amp? (Not interested in playing with additional or active crossovers. Only in "simple" remedies". Or does someone know of a comparable quality amp with an input sensitivity of 1 volt? I have the TAD-60 and am looking for a suitable SS amp with at least 150WPC with sound similar to the Belles. Unless you all tell me that the TAD-60 is not powerful enough to provide power above 800 Hz to such an insufficient system,then I will look further.
springbok10
springbok10 OP
711 posts
 
Interestingly, when you look on the websites of amp manufacturers, it is rare to find all of sensitivity, gain and input impedance. I'm sure a phone call to each of the ones of interest will provide this, though. Thanks for your input.
larryi
3,992 posts
 
Isn't input sensitivity a measure of input volts needed to attain rated output? In that case, it is NOT the measurement needed for matching two amps for biamping, unless both amps have the same rated output. I think GAIN is the more relevant measurement.

It is a good idea to have, on the amp with higher gain, a volume control. That way you have precise control over the balance between the amps (in-line attenuators can be used if the "wrong" amp has the higher gain).
aball
2,016 posts
 
The best way is to compare input sensitivity at the same output level. You can usually calculate all the relevant data from the little bit that is given in the specs.

Arthur
springbok10 OP
711 posts
 
KISS is correct! The inefficient speakers still sound better driven with one amp of low power than biamping with a SS "D" amp. Coherence and fluidity is lost. I will try biamping with 2 TAD-60s - I've just found a used second one. Will biamp vertically - one amp to one speaker, identical tubes. If the bass is not tight enough, will use a TAD-1000 for LFs. At least they are the same amps, just more power. But then they would be biamped horizontally.
thanks for input. Numbers dont translate into coherence, so it still is probabaly correct that 2 identical lower powered amps will sound better than trying to match sensitivity, impedance and gain.
gmorris
351 posts
 
If you use an electronic xover for biamping. the issue of input sensitivities of the amps will not be that important since the levels can be adjusted via the xover.
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