I'm wondering what the damping factor is for this amp. Is this the right place to ask? That spec isn't given on the Rachael web page.

Good question and it never crossed my mind when I ordered our Rachael amp. I kind of gave up on the spec game when I proved to myself that Steve's Zen path was the way to go for us. George Augspurger is a well known name in acoustics/pro-sound world and I think he knows of what he speaks. I can vouch for the fact that our Rachael drives and controls our Omega 7XRS amazingly well. As a bassist I am a little OCD on the amount, tone and texture of that end of the spectrum. What speakers are you thinking of driving with a Rachael? Happy listening, Chris.

I realize it will be low, even very low because of zero negative feedback. It may also relate to the output transformer and factors related to it, among other things(such as the resistance of the speaker cables). But is the damping factor for the Rachael known? Could it be as low as 2 or 3?

The reason I ask is that I recently have been assembling a system. It isn't all the way there yet but the Rachael is the amp. The speakers are a custom build of the Musical Affairs Mini Baffle. This is a 1.5 way speaker using modified EMS LB12EX wideband field coil drivers with a MA5EX tweeter to augment the high end. It is a about 95-96 db efficient.

I noticed that bass performance was a bit lean. Part of that could attributed to break in for the drivers. Just to check it out, I connected an old NAD 7150 50 wpc receiver to how the sound was different. First thing I noticed besides the minimal amount of turn the volume knob allowed before getting way too loud was the bass was much better. Of course there were other differences too regarding the overall character of the sound  but that wasn't the point.

I asked a very highly respected builder of SET amps about it and he offered that the difference in bass performance could be related to a damping factor so low that the amp wasn't able to get the driver to deliver full bass. He told me many of his clients believe they need more watts to achieve proper bass when it really is that they need an amp with a bit more damping. Usually obtained by use of better OPTs.

It may just be that this amp and these speakers just are not an ideal match. No fault of either component, not all amps and speakers can be expected to work equally well together.

I think Omega designs are a better match up with Decware SET amps. The drivers used are apparently more forgiving of very low damping it seems.

I may be needing to do some further system changes.

The field coil power supplies (one for each speaker, powering both drivers) come with the speakers. They're preset at 12.4 volts and aren't variable.

They appear to be OB's.
http://www.musicalaffairs.com/home-fieldcoil/

I don't know where you are at, but 124 sounds like it could be your wall voltage?

Good because 12.4 had me scratching my head.

Still don't understand why the NAD would give you more bass, more controlled bass yes.

Too bad the voltage isn't adjustable to some degree, I could see where that would be helpful with different amps.

In my experience a lower damping factor usually means more bass because the cone moves more (higher x-max at resonance). It is not until the power exceeds the compliance of the speakers' suspension that the lack of damping is ever a problem. Once the power level is at that point for a given speaker driver in a given box or baffle, then having a damping factor greater than zero will allow the speaker to play louder without distortion. So if the speaker has to be played loud to too have bass, then some damping would be desirable. If not, then damping will result in less bass.

The SE34I.5 is a triode wired pentode(EL34) or beam tetrode (6L6) amplifier that by being wired as triodes have linear output into all impedances making the damping greater than zero. The SE34I.5 into 8 ohms is about 5.7 damping factor. Of course there is the inconvenient truth that a speakers resistance rises and falls through it's frequency response. At resonance the speaker is more likely to be around 30 ohms not 8 ohms.  At 30 ohms the damping factor would rise to between 15 and 21 depending on what position you had the speaker impedance switch set to. Another inconvenient truth is that this simple formula only works with pure resistance, and both the amplifier and the loudspeaker have impedance which is to say resistance, capacitance and inductance. That makes reality 36 times more complicated than the damping formula can predict.

Please read the following excellent explanation:


Click here for a great  explanation of damping factor and speaker relationships.

Steve