6 dB per Octave Passive Crossovers

[LowOhms]

Yes, this is Dr. LowMu elsewhere. I tried to be a bit diplomatic earlier but Jeff fails to see that others don't agree with his methodology. He's on a self proclaimed hiatus from his usual posting spot and can't stop putting his ideas out there, in this case here. In the past Jeff has written that he can hear the difference between a cathode resistor of 10 ohms difference. I asked whether that was hot or cold without a response. His posts are inflammatory and by the tone of his first question I would say that he's trolling. His experience goes way beyond most posters and if he's asking about Altec, he's owned them before or has personal experience with a variety of drivers. His current favourite speakers are by a friend of his that uses 604"s.

Hi Zelgall,

You have gotten a few things correct, and you have also made several rather important errors. I do not have the time to spend, nor frankly the inclination, to accurately respond to your writings.

If you would like to contact me privately, I will be happy to email you, so you can re-post about me to others 100% factually. I certainly would appreciate you doing that. Thanks.

Sincerely,

Jeff

[mah]

drlowmu hears volts: RE: Biasing a 300B amp - by ear? - drlowmu - SET Asylum

I hear sound pressure variations.

[zelgall]

Hi Zelgall,

You have gotten a few things correct, and you have also made several rather important errors. I do not have the time to spend, nor frankly the inclination, to accurately respond to your writings.

If you would like to contact me privately, I will be happy to email you, so you can re-post about me to others 100% factually. I certainly would appreciate you doing that. Thanks.

Sincerely,

Jeff

Jeff, you are correct. I did misquote you and it was due to my poor memory. My apologies. It was about 8 years ago but that's not an excuse.
It was a grid stopper that was in question and it wasn't that you could hear a 10 ohm difference, it was .05 ohms.
This is the relevant post from DIY tube Asylum:

Posted by drlowmu on October 4, 2004 at 07:59:39
In Reply to: Question for Doctor Low Mu posted by Vinnie on October 4, 2004 at 03:00:21:

Hey, if I had one you could duplicate, I'd send it off to you but I don't.
I can tell you, by ear, I very much like 115.00 ohm grid stoppers on that tube, and a 2A3. ( 114.95 ohms minimum, to 115.00 maximum, using a Fluke 8060A ).

My current P-P 6B4G amp is basically a globe 27 ( 227 ) AC ( cap ) coupled to a UTC A-18 as a splitter driver trannie, to P-P 6B4G's and into a pair of Dyna ( ST-35, SCA-35 ) output trannies, real sleepers.

But the amp's two B+ supplies are real low in DCR, employ eight 5Z3's, double tube regulated ( series ) and would be a nightmare for you to try to duplicate, as would the multiple L/C/L/C & current sourced DC Filament supplies. Its on four chassis. Got the mental picture??

Jefrf Medwin

[LowOhms]

Hi Zelgall,

Thank you, very nice !! I actually remember someone ( you ) eight years ago asking me about hot and cold resistances. Wow.

I shall give you my delayed answer - today !!

Since its a grid stopper, ( and not a power dissipating plate or cathode resistor ), the grid stopper would dissipate very MINOR power (heat) and it would be most subject to the ambient temperature rise of the amp, below deck. I am an amateur, and had no way of accurately measuring that.

Thank goodness, I had a couple of 4 1/2 digit Fluke 8060As working well back then, to measure things. Also, anyone can compute what happens when you place 1 MEG Ohm resistor across a 120 Ohm resistor, as a minute fractional change.

( IIRC) each mono amp had 22 regulators on them ( 16 for the filaments and 6 regulators for the B+ ) so "everything" was locked down good and tight, and it allowed me to make esoteric listening differentiations, that likely, no one in audio had ever had the opportunity to do.

Zegall, how do you think I felt when people intimated I was crazy and lying ?? Not so nice at all. When my Kansas City audio buddies HEARD that P-P-P 6B4G amp in their homes, they named me "drlowmu".... from that day on !! WE knew it was the best thing we all had ever heard. The darn ( " Zediker " ) solid state B+ regulators would blow regularly, and it became a nightmare for me to keep it going, so it got retired. An all-out FUN triode amplifier to design, build, and experience.

Since 1988, I have heard better amps, the super expensive MBL amps are wonderous to me playing their cost prohibitive MBL Radialstrayler omni speakers. For tube amps, I easily most-respect the Serious Stereo 2A3 DC amps' performance playing Altecs, over anything anyone else has built. YMMV, just my opinion, very subjective.

Good news, long-time Forum member SD-50 and I are now comparing ideas on "6 dB" crossovered A7s. He MAY even try a SERIES hookup next !! We maybe will learn things, from his work and listening. Great !

Jeff