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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

Showing 9 responses by springbok10

springbok10 OP
711 posts
 
Sorry, Gregm, just established from Paul that the Input sensitivity of the TAD-60 is 1.25 volts.
springbok10 OP
711 posts
 
>>KIS<
springbok10 OP
711 posts
 
>>KIS<< was supposed to have a question mark. What is KIS?
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.
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.
springbok10 OP
711 posts
 
I'm not a techie - exactly how do I measure the output voltage of each?
springbok10 OP
711 posts
 
Aball, I hear what you say. I certainly couldn't make the sound coherent using the gain control on the lower powered tube amp, which I suppose is not surprising. But does your reservation still apply to vertically biamping with 2 identical tube amps, which I now have, although one is being repaired? The speaker manufacturer strongly advise biamping because of the inefficiency (85 db) and the unique driver dispersion and energy requirements. They suggest "2 medium-powered amps, or bi-wired with one high-powered amplifier". I have listened with a powerful D amp bi-wired and one tube amp bi-wired and far, far prefer the tube sound. If you believe the vertical arrangement with identical amps wont work, please explain why. If they don't work, I'll probably look at the Moscode Hybrid 401, which I haven't heard, but all the reviews are pretty stellar.
springbok10 OP
711 posts
 
Eldartford, sorry to be dense, but is this done with the amps idling or doesn't it matter? Does voltage change with resitance, eg if one is feeding a tweeter and the other a high excursion woofer, while measuring? Sorry, but pretend you're writing a munual for a technical newbie:)
springbok10 OP
711 posts
 
Arthur,
Done deal. You have sold me. Vertical biamping with 2 identical amps. If the TAD-60s dont cut it, I'll look for 2 more pwerful tube amps.
Thanks again, all, for your help.
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