Octave V70SE to drive Martin Logan Summits?

I second the concerns indicated by Stan and Dob about the impedance characteristics of the Summit. I've seen specs indicating that its nominal 4 ohm impedance drops to 0.7 ohms at 20kHz. That variation will make its tonal balance very sensitive to the output impedance of the amplifier, even assuming the amp can handle the load. I would not extrapolate from its performance with Dynaudio's, which have completely different (and much more benign) impedance characteristics.

I couldn't find specs on the Octave's output impedance, or damping factor (which equals output impedance divided into 8 ohms). That might be useful information if it can be obtained. Beyond that, I second the recommendation of trying to arrange in in-home trial.

Regards,
-- Al

I did a search on the Octave forum for Martin Logans, several Octave owners have tried them. ML Aeons seem to be a good match.
http://www.octave.de/forum/index.html

IMHO, if I could drive B&W N800's with Octave MRE130's, you should be able to drive the ML's. Make sure you do gte the Super Black Box though. It does make a difference.

Here is what I found on the Octave on the Octave english website about the V70SE:

"The V 70 SE, as all OCTAVE Amps, is based on the enhanced pentode configuration. This configuration ensures the absolute stability of the amplifier against the unstable impedance of the speaker. Impedance mismatch is without consequence, as the amplifier is stable down to a 2 Ohm load. An important contribution to this stability is the Single Impedance Output Transformer.

Power Output 2 x 70 Watt into 4 Ohm
Frequency Response 10 Hz - 80 kHz / ± 0,5 dB
Total Harmonic Distortion < 0,1% @ 10 Watt into 4 Ohm
Signal-to-Noise Ratio > 100 dB
Input Sensitivity 120 mV
Minimum Speaker Impedance 2 Ohm

Al,

I have chatted with you in the past about Octave products. Here is a link to the user manual for the V70SE with lots of specs:

http://www.octave.de/en/pdf/Manual_V70SE_engl.pdf

Ciao,
Audioquest4life

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