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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s lowest channel.

Post Subject: What a beautiful result!!!Posted by Romy the Cat on: 5/19/2011

Romy the Cat wrote:

It did not last long….

Just a couple days back I was thinking that I will live with my current lower bass for a while and now I feel that I will not. I do not feel that my current ULF is wrong. In fact I feel that it is truly superb but I would like to add to it one character, still without losing what I have. I do not want to change my lower bass but I would like to a very very very very very very minor degree to add some SS hardness, still preserving all long and beautiful LF harmonics that I have now. I am sure that no one would recognize it but I do. I do have some kind of nostalgia to my bass in old room. Even though in my current room I have in a way better a sound and better lower bass but I need to deLamminise my lower bass. My lower bass now has the quality that I did not like in Lamm ML2.0. With all phenomenal integrity of Sound in that amp it did not sound hard when it called upon. I was forced to idle the Lamms output stage very aggressively but then Lamm has no power when it drove 32R with 4R tap. Even in that configuration it was too polite. Milqides and then DSETing long change it but now with 4 stage Modified Marchand tube crossover and B2 amp I find myself in the same boat. I have very-very good bass but if music is called to rock-hard stress of the very leading edge then my ULF handle it a bit overly elegant.

So, What I am planning to do it to revise my Marchand crossover further. Here is the plan:

1)      Get rid of input stage and let my preamp to drive the filters directly.

2)      Get rid of output stage, moving the attenuator to the power amp.

3)      Slightly add current to the remaining 2 tube, dropping grid resistors from 180K to 160K

4)      See what happened then

I will get rid of half of the tubes and it might do the trick. I also consider using 6N6P instead of the 12AX7 as they might be better in cathode followers. They have the same ping and just need 6.3V, since I will have just two tubes left then I might connect them in series and to use the default Marchand 12V power supply…

Yesterday I modified my Marchand tube crossover in accordance to what I described. The result was exactly what I hoped, the crossover got slightly harder sounding – two unnecessary tube stages were gone. The Sound move the right direction but some of so harmonics I felt were not as sumptuousness wonderful as they were with 4 tubes. It was however not only about the harmonics but rather about the mitigation between the accent of the leading edge and the decay. I consulted with a friend of my and he advised to play with plate current of my 12AX7. Driving it up and down I end up with 157K cathode resistor, that gives 1.27mA. It is very nice result with a very accurate enunciation at the very pit of the very bottom end but with immediate and always spooky very smart release of the pressure. Very musical, very dynamic and very natural – simply beautiful!

They I played a bit with multiple 12AX7 tube that I have. When I had Lamm ML-2.0 I accumulated a Lot of 12A7 for Lamm’s first stage. Properly I have 30 different types. With Lamm I very much preferred Telefunken with smooth plate for MF and ribbed plate for bass channels (I multi-amped with ML2). Since it is ULF channel then the ribbed plate was the obvious candidate. All Telefunkens are different, even of the same contraction and party by party sound different. All my tube were marked by sound (in context of ML2) and I find that it was no correlation how they sound in my crossover and in ML2. The best for bass tubes in Ml2 were too aggressive for my crossover; still it is nice to have it as an option. All together I turn out to like Russian made 12AX7WA. They are a bit muddy but it turns out works very nice with the plate current that I have settled.

Hm, I migh not need 150W DSET after all…

The caT

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