Most all my old gear is gone within the last 10-15 years.
Collins S30-1 Amplifier
Collins 75A-4 receiver
Hallicrafters SX-115
Heathkit transmitter ( cannot remember the number)
[Link: eham.net]

Speaking of which, none of the tubes in that set had octal plugs and sockets. This seems to me a bit late to introduce a tube that wasn't octal, so obviously I don't know when octals were introduced!


I was skeptical, so I looked. According to the site you sent me to above, the 80 was introduced in the late twenties. Obviously this site has some lore as well as some facts. (EDIT: Later in the same description it indeed says it was introduced in 1936. The site names two dates of introduction.)


It sure is! it's an integral part of the power supply, a low-pass filter intended to pass the low low frequency called DC.

BUT since AC from the power supply is introduced into this coil, the magnetic field varied at the rate of 60 Hz (ok, ok, 25 to 60 cps) in it, which resulted in hum in the speaker. To counter that, a separate small coil was added to the speaker magnet assembly, and that was fed filament voltage that could be adjusted in the better amps.

So... we need a magnet; power supplies can use coils; the coil is a magnet but it has some hum; so some adjustable hum is introduced to counter that... and we wonder why it took so long to get high fidelity sound?


THAT explains its robustness, even its large surface area, which helps it be cooler than it might be!

I don't have the room for all those amps. My stuff for installation is almost overwhelming as it is. If I had the room, I'd have two cutting lathes, anyway....

I just remembered the thing that had the greatest impact on me as an installer. I went to school at UC Riverside and got myself a summer job in the Physics Department disassembling and salvaging parts from equipment that had been bought at surplus.

In a nutshell, I saw how this great nation poured ingenuity and thought into equipment that could make the difference between lives saved and lives lost on the battlefield.

I saw weatherized product, a thick layer of waterproof... lacquer? over everything. I saw a device 18" wide that was built in three sections, hinged so they folded down to about six inches of width. This stuff was laced with silk thread, with a half knot every 3/8" or so, but EXACTLY spaced.

Every installation I do owes something to that equipment, and every installation is but a poor imitation of it. I appreciate the situations where the price is not an issue, because then things can be done incredibly well. I also am proud of you guys and the wonderful photos you sometimes show of your work, work to be truly proud of.

It's said that there are artworks inside walls of the Notre Dame Cathedral in Paris. These paintings and such were done on open walls that the construction workers knew would be covered up as the church was built. That didn't matter: this beauty and perfection was just fine, even if only the eyes of God could see it. It's good to think of our work behind the scenes that way, too.

The field coil is after the rectifier in the power supply, used to drop the voltage as well as filter, but in those days, large value high voltage caps for filtering were difficult to make in a small package but it was really there to remove the ripple.

The additional coil, wired in reverse polarity, is the basis for humbucking instrument pickups and they only came into being in the early 1950s.

WRT filament voltage- the reason those hummed is because that was AC and one or more tubes (or half of a tube) may have been on opposite poles- the hum goes away when they started using DC for this. One of my guitar amps is the same model as the one used when Marshall built his first guitar amp, which is almost a carbon copy but with some components that needed to be changed because the original parts weren't available in Europe- lots of analysis has been done and one site goes into each section, explaining why it does what it does and that particular model of Fender amp can have a very low noise level. It's interesting to read comments from people outside of electronics- they have the opinion that these were designed from the ground up by people who were absolutely brilliant when in reality, most looked in a circuit book to find something for each section that would work for the application. Take a bit of this power supply, use this filter, add this input section, a pinch of tone stack, grab a phase inverter and choose an output section before deciding if they wanted it to be squeaky clean or a bit dirty. Clean (ultralinear) came later, but people are out there, coming up with their own designs all the time.

The designer of the 5F6a Fender Bassman, which is the amp that Marshall copied, was a session musician and if you watched Warner Bros cartoons, you have heard one of the recordings he played on many times- he played steel guitar and the first sound on their theme is the slide 'sweep' that starts low and goes up in pitch.

One of the reasons I like old things is to see how they were made and when parts are available to make them work, I get them to work. The Oahu amp from the '30s is very simple, but made to last- the ground buss is a stiff wire that's attached to both ends of the chassis and all grounded components are soldered to it. They placed components as close to where they needed to be with leads as short as possible and it's very quiet when no signal is present. I also have some old hand planes for woodworking and if I were to sharpen & hone the irons, they would work as well as they did when they were made which, in one case, was the late-1700s.

The thread or string for lacing wires was used by Sony before they started using plastic wire ties or the ones that are twisted, with a small bead at the end. The wires were straight & parallel, the spacing of the knots was very regular.

WRT spacing of wire management (wire ties, etc), when I did car audio, an Acura NSX came in and we had to install a lot of additional equipment, including an alarm, subwoofer, more amplifiers, etc. These all required that wires be added in various areas of the car and to do that neatly, we needed to un-do the sloppy work the previous installer had done. There were two of us working on it, we were trained differently (Tony was trained when he was in the Marines), but we both liked to do things in a similar way and part of that was wire management. When the car owner decided to sell the car, he took it to the shop closest to home and it was a place where I had worked, so I was still in contact with the people who were still there. I was going to lunch with the service tech one day and the car audio installer came to the front of the store, bitching the whole way about the number of wire ties used to secure the bundle along the rocker panels. When he stopped, I said "Looks good, right?". That really set him off but later, he agreed. Every six inches and if one or more wires needed to leave the bundle, it wasn't just allowed to hang loosely.

This is a great post.

Thank you.

To this day I am deeply impressed by what the military did to ensure performance under ridiculous circumstances, such as in the jungle rain.

When you hear about military budgets, remember that they don't just want money so they can break things (the basic offensive action of every army), they want money to protect their "assets," our brothers and sisters.

If you get a chance and especially if you're interested in military aircraft, go to the Wright-Patterson Air Force Base and museum. They have aircraft that are open to allow viewing inside and the wiring is often exposed- that's cable management to an extreme. Wear comfortable shoes- it's a lot of walking but they have so many interesting planes and jets including a YF-12, which was the experimental fighter-interceptor counterpart to the SR-71.

Here's one of the other planes-

[Link: en.wikipedia.org]

I think you overly denigrate passive crossovers. There has never been to my knowledge, any huge rush in any part of the market, including tweak golden-ear listeners, to dump all their speakers with passive crossovers and convert to speakers and amps with electronic crossovers.

The advances in speaker design that I've witnessed over the decades have almost all come out with passive crossovers. (And I only say "almost" because I can't think of A SINGLE TIME that a hot new technology has been brought out using electronic crossovers, but that doesn't mean it didn't happen once or twice among the thousands of new models.)

It can't be that bad as well as being nearly universal.

Not too long ago I turned up an old Jensen tool bag I had in storage that hadn't been used for probably 20 years.  It had IBM Type 1 connector parts in it that were from the late 80s and also a bunch of BNC T-Connectors & terminators from the early days of Ethernet!

For you guys that aren't old enough, IBM Type 1 connectors were used in some of the early corporate/campus networks long before networks were commonplace in business or homes.  It was a token ring network and didn't last too long before Ethernet became a standard.

When Ethernet became established and before twisted pair took over, coax cable (thinnet & thicknet) was used between devices with BNC connectors.  Just like Token Ring, a break anywhere along the network cabling would crash the entire network (not just a single device).

I was talking to an IT guy a few weeks ago that was in his 30's and he had no idea networking even existed before before twisted pair based Ethernet.  He seemed to think CAT5 is where it all started...

If you didn't tell him this, next time you see him you should mention that the "5" might have been a hint.

Of course, then he's going to think RG6 was the sixth cable they tried (It was the sixth RG cable that they named). And before you say it, yes, WD40 was the fortieth water displacing formula they tried... and it IS NOT a lubricant.

Designing a good crossover operating at speaker driver impedance is a mess.

From a system design standpoint we should not be attempting to design "flat" speakers and "flat" amplifiers, we should be designing a "flat" system and the "speaker" should accept a line level input, hopefully balanced.

Unfortunately, this will rob the audiophile of some historic choices. The drill has been to search for the "ultimate" amplifier, "ultimate" speaker, and "ultimate" speaker wire. It's a lot less fun if there is only one search. In reality, since the audiophile's room is what it is, a little DSP work inside the amplified speaker box could be helpful. (but probably not as helpful as some acoustic treatment) Unfortunately, DSP does not seem as "pure" as the ultimate amplifier.

A nasty practical detail is that a good speaker designer and a good amplifier designer are usually not the same person or company.

As I said, I think you overly denigrate passive crossovers.

We did a system for a client.

When we broke it in, we set it up in a tiny test room, about 15 ft x 20 ft. We played the system -- three JBL Everest mains, Six JBL 18" subs, and the six surrounds, with the level up over 100 dB. I've played instruments and have been doing music things for decades, and that system sounded REAL.

It also sounded REAL in its theater environment, 60 feet from front to back, about 40 ft wide and 20ish feet high, also over 100 dB.

Might I say that those speakers have two input terminals, a plus and a minus? They don't AT ALL match "Personally, I wouldn't see that as a bad thing because passive crossovers are not great for fidelity."

buzz would be quick to point out -- and correct -- that the Mark Levinson amps and the rest of the JBL system might have something to do with the overall high quality, but that could not overcome passive crossovers if they were not great for fidelity

And yet, the commercial and recording industries have been using active for decades because of better time alignment and other benefits.

Passive crossovers are used because it's easier for them to design this type and it's easier for them to say they have perfected the crossover through some untold means that will baffle (no pun intended) their followers.

True time alignment in passive crossovers isn't new, but the means to accomplish it are:

shift the physical position of the drivers and hope the listener is sitting in a way that it will still work and the room will allow the benefits to be heard.

That's about all.

Passive crossovers can be very expensive, too. The ones I built for my speakers cost far more than the drivers and basic materials for the cabinets, even with a wholesale account for the parts.

If you get a chance, listen to the Steinway Lyngdorf system.

I think you're forgetting the thing that makes active speakers difficult to sell- they need to be placed near an outlet. Try selling that to people who don't understand the benefits.

Tell him when the concept and first use came about, then watch his reaction.