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The RCA BA-4 series...

were built for commercial monitoring duty in recording and transmitting applications, but are wide band full fidelity amps, unlike many commercial units, which were more PA oriented, or restricted in frequency response for various reasons, and thus not so suitable for home audio without modification.

The 1620s are just a low noise version of 6J7s, and 1622s are low noise versions of 6L6GCs. The plate cap connections are generally avoided in consumer gear due to high voltages, not good for little (or big!) fingers, much safer to route it thru base pins.

Our BA-4 is slated, after a re-build, for duty in a future bi-amp situation, where it will drive a single low-frequency 15" speaker system 35-500 Hz. The top end over 500 Hz will be a pair of speakers with ADS midranges & tweeters, and possibly high frequency horns, driven by a stereo Magnavox 9303-00 (4 x EL84) power amp from a console.

Rex: do you know a source for the plug in electrolytics? Can't find them via my usual source... I'd like to replace all 7 if I can find them.
 
Top cap connector on tubes like 6J7 and such.This was not a plate connection but the grid connection.It is safe to touch----BUT-- if you do be prepared for a loud startling noise thru the speakers of the system the amp is connected to.I tested devices with these tubes as pass-fail by turning the gain down and touching the top connector.If you heard hum or noise the amp is most likely working.1622 tube-low noise-RF version of a 6L6GC these were sometimes encountered as RF buffer amps in AM transmitters,Modulator input amps(Speech input stages)in AM transmitters.The original Continental Electronics Variable Frequency source for the 420A transmitters here used those tubes in the sources output stage.When 1622 tubes became NOA,used regular 6L6GC-they would work-but got short life from them.The Continental Electronics device was replaced by solid state frequency Synthesizers.The old devices got surplused-don't know where they went from there.
I don't know of any new sources for new plug in caps-wished I did.The caps that used to be in our parts stock were actually older JAN parts-since this plant is a gov't agency-parts often came from other agencys.The caps were old-had to "form" them in an old Sprague "Tel-Ohm-O-Mike" cap tester before using them in the TMC transmitters.Otherwise you would trip the supply breaker or blow the fuse.Once they were formed-the caps were OK.They were old when we had them!Since the TMC's were scrapped-the caps must have gone with them-too bad-I could have used them.You could always wire an octal socket in the device you want to use them in.Sadly,you may have to go to wired caps unless you can find the plug-ins on the gov't surplus markets.Electronic gear made for Gov't use used as lot of those plug in caps.More so than commercial gear.Roger--wish you luck in finding the caps.And like your idea of the Bi-amp with an RCA amp and the Magnavox ones.Wish you luck on this.It is still impossible to find caps for my McIntosh "60" amps.If only I could get the caps would be easy to recap my amps and put them back into use.None of the modern suppliers carry caps that are over 450V.I need-525-600V.Debating the idea of using oil filled caps-but on an outboard chassis.What it may boil down to.Oil filled caps are easily obtained.See LOTS of them in transmitter power supplies.And the 1622 tubes used for video amps and DA's,too.Older TV stations.
 
6J7 tube and equivelants-these tubes common in older Gates and RCA broadcast consoles as mic and TT preamp stage tubes.Ampex 300 used the "red" can 1620 version in the PB preamp stage.And have found these tubes in many older radios and amps.Radios-IF stage,RF stage tubes-and amps-low level preamp stages.One Seeburg jukebox amp I used to have had one of these tubes.Other Ampex PB amps had them-thats where I tested them by touch to see if the amp worked-edit decks in radio stations.
 
Like the oil cap idea for the Mc's

Marantz was one of few consumer amps to use them, in their M2 and M5 amps. AFAIC Marantz made the best quality consumer-grade tube electronics of anybody. And current prices reflect that, unfortunately, could never afford a pair of M5s today.

1622s are still avaialble, just got a few NOS RCAs from a guy who has tons of them.
The BA-4 has RCA black plate 6L6GCs now, but wanted the original 1622s for it.

Top connectors - in power output tubes like the 1622s and in other common ones like 807s, not a good idea.
 
Yes,top caps on power tubes like 807 and such-it is the PLATE connector and is high voltage.In transmitters top plate connector tubes must be behind an interlocked access panel to prevent shocks and burns.Consumer gear the same sort of thing-but 807's in consumer gear is VERY RARE.Maybe in "Ham" radio sets-but in those the tubes are behind an interlocked cover or door.
 
Remember when Stromberg-Carlson made PA amps,telephones,radios and such.Esp remember their central PA systems in schools-the main unit usually with TT,radio tuner,tape deck would be in the admin section of the school-often by the principals office.Then there was a clock-speaker panel in the classrooms.Often the principal and other admin folks would make annucements over the system before your teacher started the class for the day.And at Christmastime-Christmas music was played thru the system.
 
Reply#37

Rex -I had the same experiences. The principal's office had a large panel with as many switches on it as rooms for the school, including the gym. Select the rooms and press the heavy-weighted stainless steel mike, and you were "live". Those were such good memories, actually - much sower times. I was in all our schools between college, as a night-time custodian, to help pay for tuition. I know the Stromberg-Carlson name, but I can't remember the brand in our school district. I do remember times when the principal turned on the system and a huge feedback came over the speakers - that woke everyone up. LOL!
 
Stromberg-Carlson

was a Rochester NY outfit, became a big player in the telephone business, and much later on post-war made some very nice Hi-Fi component amps, tuners, receivers, speakers, even a turntable, and high-end consoles that had their discrete components mounted in them, like Fisher and Pilot. I have a late '50s brochure around here somewhere showing their Hi-Fi line, and have had a few of the products, all were excellent. Prior to the mid '50s besides telephone equipment they were also well known for floor and table radios as well, and TVs in the 50s. In the early 60s they were absorbed by General Dynamics, and more or less abandoned their consumer product lines at some point.
 
I do see, occasionally, some of those Stromberg-Carlson radios/consoles that look very nice. Your information, Roger, just brings a little more appreciation to a name I'm not too familiar with.
 
RE Stromberg Carlson

In 1952 My Parents went to O P Lutz furniture Co in Lenoir NC and bought a Stromberg Carlson Hi Fi, it was still around when I was a kid, it had a 10 inch speaker facing forward, and a 12 inch facing the floor, it really had some thumping bass , I really would like to find another one,as I remember Mother said it cost over 200.00 which was a fortune back then,They saved for a year to buy it.
 
Anyone got pictures and stats on SB Hi-Fi systems-The products SB made I have seen have been the school PA's,PA amps ,and phones.Also another school sound system maker was DuKane.Have the manual for a DuKane system that was at the DuPont factory out here.I am sure its long been replaced.The DuKane unit had two 50W amps with PP 5881 tubes.And it was 70v Line.At a swap shop bought a couple plastic tubfulls of books-they came from a former DuPont Engineer-made for interesting and useful reading.
 
Found the S-C brochure

showing their TOL Hi-Fi component line for 1959. Problem is I'm without scanner at the moment. Meanwhile here's a good link to some S-C stuff:

http://www.audiophool.com/MadeInRoch.html

They had a pretty comprehensive line-up, my brochure doesn't show the consoles or radios, but the better consoles had the S-C Hi-Fi components in them, such as the ASR-333 and matching tuner, I've had one of them, along with some of S-C's Custom 400 components. The weird ASP-422 amp uses the rare and oddball 6DY7 tube that has both push-pull stages in one tube! I've been wanting one of these for some time but haven't run across one yet.
 
Excellent info on the SC Hi-Fi gear-The 6DY7 tube is a real oddity.Would have been neat if it caught on.Makes me think of an 815 Tube-two power tetrodes in one envelope.Plate connectors on the top of the tube.I have seen 815's in older-early FM transmitters and TV transmitters.Typically used as frequency multiplier stages.Ampex used 815 tubes as bias-erase oscillators in Ampex 300 Rec/Pb amps.Put the machine into record mode and hold a neon lamp near the 815-it will light if the stage is oscillating.
I have one of those Kodak amps in a Kodak "Pagent" 16MM projector.Got it for free from the dump.The machine does run.Missing the speaker.It would be the one with the 35L6 tubes in the output.Kodak projectors were common along with Bell&Howell ones for classroom proectors used in schools.A few times I was assigned to be the impromptu projectionist for running a film.The boys in that class got their turns!Teachers did not like being projectionists-so they had one of the students do it.Occasionally a film got broke.
 
Harmon Kardon Tube Receiver TA224 - $225 (Bothell)

ad: " armon Kardon Tube Receiver TA224 - I believe this was the first stereo receiver built for the consumer market and it is in near mint condition! - Nice NOS 6v6 output tubes - All input and driver tubes are vintage. Great Sound!!!! Also I have a nice HK Walnut Case which is rare and included with receiver . firm on price. Will sell on ebay otherwise. Auditions welcome - tuner. glass, and chassis and lettering are near mint. all lights working. - No disappointments - everything is functioning correctly - this has a nice phono stage - Cool Mid Century Looks - I believe this was built around 1960 to 1962 "

http://seattle.craigslist.org/see/ele/4884629508.html
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Antique Magnavox Concert Grand Stereo Console

ad: " Magnavox Concert Grand Stereo Console circa 1959 - Make an offer!
*This is a classic, some call it the Holy Grail of collectable antique radios, found in my barn
*Cabinet needs refinishing but no major damage
* Independent left and right tube stereo amplifiers each with 15" woofers and mid / tweeter horns
* Tuner dial mechanism works (it moves when the dial is turned), face is complete and undamaged
*Turn table appears complete
*Electrical chassis need total rewiring, some tubes are still with the chassis
*Partial schematic pinned to the back of the cabinet "

http://bend.craigslist.org/atq/4892836597.html
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Difficult to find, but that CG looks "crusty"

That's the first CG in that vintage/style that  I've seen that did not have remote control...but I'm no expert. The multiplex adaptor is where the complex RF remote unit would normally be. Notice the knob holes for the remote on/off controls in the changer compartment are covered. I suppose this is a later model since the"green eye" tuning indicator is now [COLOR=#008000; font-size: 12pt]an Astrosonic-style meter. Also unusual to see the "fish hook" record changer. No "record reject" button on the CG plaque either, pity.[/COLOR]

 

This Concert Grand has been on the local Craigslist for one month, first advertised with no price and now showing up at $1,500. You'd need to want one very badly.

[this post was last edited: 2/16/2015-13:14]

http://palmsprings.craigslist.org/ele/4829724714.html
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MCM shows

This was the week of the Mid-Century Modern shows in Palm Springs. There are many venues (for a price) to explore. No time or money to do a visit and pick up that CG at the same time. Instead, we're just hunkering down as a winter of much less intensity buckles the tree limbs with ice and cold continues. Twintubdexter, are you out there - just pick this up for me and I'll be out in my dreams to pick it up.

~~~~~~~~~~~~~ ice man cometh
 
Whats with the abundance of CG Hi-Fis on the West Coast? But NONE in my area?Just remember my Moms-hers had the Multiplex unit just like on the back of the one shown. Hers didn't have any remote controls.Noticed in the picture of one of those units the rear speaker cab access panel was removed.Needed for proper operation.Other folks say around here Magnavoxes were indeed rare.-there were no dealers in Greeville.Closest was Raleigh.
 
On with the hunt!

My "expert" friend in Tennessee with his huge collection of Magnavox stereos says that most of them were made in Greeneville...Greeneville Tennessee that is. The plant, long shuttered, is still there where his Aunt was employed for many years. For some reason, as far as Craigslist, I have seen more well-cared for Magnavox consoles in Northern Oregon and Washington than anywhere else. My CG popped up in Eugene Oregon, was $85 reduced to $40. A very nice lady was selling the contents of her late parent's home. I actually gave her $100 since she worked with a shipper for me, then I sent her a small gift afterwards. The point here is that you need to keep looking and eventually you'll discover one at a reasonable price and perhaps even in your own area. It's not like you're trying to find another Hope Diamond.

 

By the way, my TN friend says that he prefers the sound of his Imperials to his Concert Grands. I guess it's a matter of taste and how well your hearing is.

 

Two of my friends CG's...can you guess which one is real wood and which one is the faux pas?

twintubdexter-2015021709360301109_1.jpg
 
Right now NOT looking--maybe I will stumble into a CG at a swap shop or yard sale.Just hoping.They might as well be the Hope diamond in my area.The Hi-Fi on he left in the picture looks like the real "woody" model.The tuner-preamp on that one looks just like what my Moms had.Hers was the "modern" type case.She liked Early American furniture-surprized she didn't get one like what is in the picture.Got many,many hours of listening from her unit!-Records and the radio.Later CD's.Connected a CD player into the Aux input on her unit.Worked really well!She then played more CD's than records.
 

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