Euphoric Realism vs. Euphonic Romanticism

Yes, that is certainly a possibility although when I heard it a few years back it came across as beautiful but euphonic (not that there is anything wrong with that).

I think the Audio Space will more closely match the 'modern' 300B sound that I was getting with the Mastersound integrated amplifier.
I should note that I made mistake earlier in this thread: the Mastersound 300B P.S.E. integrated amp has an active line section. I was incorrect when I said that the line section was passive.

I will pair the Audio Space with my Hovland Stratos amps this weekend and see how close I get to the magic of the little Mastersound integrated.

The Audio Space preamp and Hovland Stratos amps did not get close enough to the magic of the little Mastersound 300B integrated.
It looks like I will be selling the Hovlands and going with the Mastersound 845 monoblocks.

Exlibris, some things about this thread are striking. First, are you really running a 300B amp your MBLs? The impedance curve of the MBLs is a mismatch with zero feedback tube gear and will result in a brightness in the midrange. Here's what is going on:

http://www.atma-sphere.com/papers/paradigm_paper2.html

The MBLs are Voltage paradigm technology and the 300b amp is Power paradigm. Anytime you mix the two you can expect a tonal coloration at the very least, in this case it will be in the midrange and upper midrange- a vexing situation.

The result is likely that you will not like any preamp that is indeed neutral and musical, because it will not be laid back enough, due to the amp/speaker mismatch, if I got this right.

What you need is to run feedback so the amp can deal with the speaker. I was going to suggest that to you months ago. Either that or you need to think about a different speaker.
It would be easy to set up a feedback module that provides the gain needed to run the feedback, but IMO that defeats the purpose of zero feedback amplifiers (which is to more closely obey the rules of human hearing).

Hello Atmasphere,

To say that the 20 watt, 300B 'drove' the MBLs would be very misleading. There was next to no deep bass, there was nothing in reserve for dynamic peaks, and I couldn't play my system over 91dB. Nonetheless, it did produce the best vocals, best acoustic guitar, best electric guitar, and the best cymbals that I have ever heard on any system.
If I had the funds I would buy the 300Bs just to play select songs.

The Mastersound 845 monoblocks (50 watts; parallel single ended; Class A; no negative feedback) really do drive the MBLs. I don't know how this is possible but it's true. Mastersound does make 117 watt SET monoblocks but I have no desire to get them right now because the 50 watts is more than enough. How can this be? As you know, I know next to nothing about the technical aspects of amplification but perhaps it is because there is a big output transformer for a set of dedicated 4 ohm taps? Each little monoblock weighs 75 lbs. Mastersound makes their own transformers by hand, in-house, and they are very secretive about the windings etc. Maybe there is some magic in there.

I had thought about going to horns rather than letting the 300Bs go but now I'm enjoying my MBLs again. I've moved them into a bigger room that is all wood and that's helped as well.

Exlibris, I bet moving the speakers into a different room had as much effect as any amplifier you tried!

Larger SETs over about 7-15 watts have trouble making bandwidth at both extremes due to the issues of the output transformer. My guess is that in this case that is helping you out. The amplifier is going to make nearly constant power on the MBL if you are using it on the 4 ohm tap. The MBL is designed with the idea that the amplifier will make only half as much power in the upper midrange where there is an impedance peak. You need feedback for that if you use a tube amplifier...

Or- as I mentioned to you some months back, you could use some form of network (to absorb the excess power), or a tone control (if you don't use feedback). From what I'm able to get from your descriptions, it sounds like you went the tone control route. As far as I can tell, it seems a happy accident, but is also why you are having such issues finding your 'holy grail'. Not much out there is going to work when you try to drive a Voltage paradigm speaker with a Power paradigm amplifier.

It is a fact though that a speaker that is designed for a zero feedback tube amp would win you more performance out of that tube amp than you are currently able to get. I think you are aware that something is amiss or you would not be on the hunt. Am I right??