Octave V70SE to drive Martin Logan Summits?

Audioquest4life, yes I recall that discussion, in this thread. Thanks again for providing the information and the links.

That's certainly a good sign that people are happy using the amp with the Aeon, although the Aeon is a slightly less difficult load (1.3 ohms at 20kHz, instead of 0.7 ohms).

There are two concerns, as I see it:

1)Will the amp be able to handle the load?

While your B&W N800's are a somewhat difficult load, they are difficult in a different way. I found a statement in a review indicating that their minimum impedance is 2.8 ohms, and that occurs in "the power band," which I assume means the bass or mid-bass. The ML, like many electrostatics, reaches its minimum impedance at 20kHz, and that impedance is highly capacitive. On the one hand, obviously much less energy is required at upper treble frequencies than in the bass region, but on the other hand the highly capacitive nature of the load increases its severity.

2)Achieving proper tonal balance. The lower the (unspecified) output impedance of the amp, the more prominent upper treble frequencies will be. The higher the output impedance of the amp, the more upper treble frequencies will be de-emphasized. The degree to which the speaker's tonal balance will vary as a function of amplifier output impedance will be much greater than for most dynamic speakers.

So I'm not sure what the bottom line answers are, but those are some thoughts.

Best regards,
-- Al

As Al says, if A drives B it should also drive C does not always hold. I have Meridian 605 amps, which are 150 watt mosfets. They never had any trouble driving my Apogee Duetta Signatures, which are known as a difficult load. But they get very hot and have to be carefully monitored driving my Gamut L5s. Most would think the Apogee was the harder load but not for the Meridians; every amp -speaker interface is different.

Al,

What can you decipher from the following specs?

Power amplifier
Output Configuration: Push Pull, advanced Pentode Mode, Grid 2 Voltage 300 V, Idle Current
Tubes 28 mA - BIAS Low, 34 mA - BIAS High. Negative Grid Voltage separately adjustable for
each Tube. Range: -16 to -40 V, 3 turn precision regulators.
Wideband Output Transformers using Silicon steel PMZ Core, single Impedance Output.
Optimum Load Impedance 3 - 16 ohms Nominal Speaker Impedance. Efficiency greater than 83
dB. Amplifier remains stable with No Load and Output short-circuited.
Output 2 x 70 W @ 4 ohms
Frequency response 20 Hz - 70 kHz @ 40 W -1 / - 3 dB
5 Hz - 70 kHz @ 10 W - 0 / - 2 dB
THD 0.1% at 10W @ 4 ohms
Signal-to-noise ratio -100 dB / 40 W
Output Noise less than 300μV
Optimal load impedance 3 - 16 ohms
Minimum load impedance 2 ohms
Gain 38 dB
NFB 10 dB
Tube set 4 x 6550 C
Quiescent current; output tubes 28 mA - BIAS Low, 34 mA - BIAS High

Preamplifier
Input sensitivity 180 mV Line Level Inputs
Input Impedance 50 k ohms
Crosstalk input to input - 105 dB
Output Impedance Pre Out 240 ohms
Channel Balance 0.5 dB to - 70 dB on volume control
Channel Separation 55 dB
Max. Level Pre Out 5 V RMS
Tube set 1 x ECC 83, 2 x ECC 81

A FAQ about Octave amp in general:

5. What is the significance of loudspeaker impedance and efficiency?

The impedance and efficiency of modern loudspeakers is not an issue for OCTAVE amplifiers.
The often-quoted damping factor is not normally a guarantee that an amplifier will exert tight
control over the loudspeakers. In practice, speakers of 85 dB efficiency and above are suitable
for use with tube amplifiers. The high stability of the OCTAVE power amplifier technology even
allows the use of speakers whose impedance dips as low as 2 ohms.

Ciao,
Audioquest4life

What can you decipher from the following specs?

Nothing particularly conclusive.

The statement about damping factor would seem to imply that its damping factor is not particularly high, and therefore its output impedance is not particularly low. Which with the ML speaker would lessen the likelihood that the upper treble will be over-emphasized, as it might be with a solid state amp.

The reference to being able to handle speakers with impedance dips as low as 2 ohms is not particularly comforting with respect to a speaker that dips to a highly capacitive 0.7 ohms, but on the other hand the amp doesn't have to supply much energy at the upper treble frequencies where that dip occurs.

Best regards,
-- Al

" Optimum Load Impedance 3 - 16 ohms Nominal Speaker Impedance"

" Impedance mismatch is without consequence, as the amplifier is stable down to a 2 Ohm load."

That means that with loads below 2 Ohms amplifier may (may!) go into oscillations.

I knew a guy who try to use some medium paert amps on his Summit. Every time sound went to treble the amp shut itself off (to avoid oscillation or whatever). He bought Spectron.

" ....the Aeon is a slightly less difficult load (1.3 ohms at 20kHz, instead of 0.7 ohms)."

SLIGHTLY ? To have the same effect amp with 0l7 Ohm @ 20 kHz must deliver almost twice more more power - if load is resistive ...but if its electrastatic its reactive load so power delivery must be substantially more then x2

Regarding 70 wpc and 83 dB efficiency - there are simple relations between this numbers and maximum SPL (in dB...) available, say 10 ft from the speakers. Not only peaks of symphonic music but even drum's transients in jazz are doubful be transmitted without huge degree of distortions (Brrrrr...).
However, you can listen pop, flute concerto and such without a sweat !

Buyer beware !