OT: Use of LOW POWER Amps

[alancohen]

Amplifier type, class or design is not the topic. Getting an appropriate match between amplifier power, speaker sensitivity, listening distance and environment is what it is about.

In that case I think I'm OK with my 3W amplifier. By his guidelines you need to double the power for each 3dB gain. So logically it would follow that increasing the sensitivity of the speaker by 3dB doubles the realized acoustic power of the amp. His baseline is an 85dB speaker. Mine are 102ish. That translates to:

85dB - 3W
88dB - 6W
91dB - 12W
94dB - 24W
97dB - 48W
100dB - 96W
102Db - 160w

So by his argument my 3W amplifier into 102dB speakers sound as loud as a 160W amplifier into 85dB speakers. I'm good with that. I much prefer running low power amps into very sensitive speakers.

[LowOhms]

Attachment 1768

Check out this article on inverted tube operation, SE OtL from Steve Bench..

Inverted Tube Operation

...........................GC

Hi 604man,

There are several problems with the Steve Bench amp you referred us to IMHO:

(1) First is that is it is paralleling many tubes to obtain the Finals stage. These tubes are never equally matched, and certainly not so over time. This produces a "choir" effect which you will not get from a single tube as the Finals tube.

How about a lovely single EML mesh plate 2A3 there instead??

(2) Additionally, it is a three stage amp, which loses transparency on Altecs, compared to a really good two stage amp.

(3) Another problem is it has a cap-couple, which should be avoided in favor of NO SERIES capacitors, just do DIRECT COUPLED, less is more. KISS rules in high end audio !!

(4) The power supply is deficient. You should never add series resistances to filter B+ to the Finals. It makes the amp "dead as a doornail", in terms of dynamic expression, and having ANY possibility of playing good bass.

Look at the 3.9K Ohm series resistors ( in the plus and minus 350 VDC B+, B- lines. ) Those added resistive parts to the Finals "screws the pooch" right there.

Hey 604 man, why do you think my moniker is LowOhms?? :-) Where Steve is using 3.9 K Ohms, I will have 30 Ohms (or less) in L1 and L2, as series resistances to the Finals.

The general amplifier schematic / configuration I have posted above is about as simple and as good as it gets on Altec speakers for home high fidelity use, IF the amp is built correctly. ( Dad used to say to me, " if " is a big word. )

It is a quasi Loftin-White configuration ( circa 1929), with a proper supply attached to it. Americans in the 30's, 40's, and later, people like Isamu Asano, and Nobu Shishido used to build it, except they all never executed their power supply ideally.

Cheers.

Jeff

[acasanis]

I have both the Bottlehead Foreplay III Preamp and the Paramount Monoblocks (configured as 2A3 SET) currently running my 1976 M19's. I cannot say enough good things about the Bottlehead amps! They far exceeded my expectations and were a blast to build/modify. I highly recommend ANY of there products!

Has anyone here every tried a bottlehead amp? Their website makes them out to be a good amp to try. And reasonably priced.
Single Ended eXperimenter's Kit