Learning to appreciate the Concert Grand

[electra225]

You guys know I have been critical of the performance of my Concert Grand. Long story short, I moved mine recently, to a spot where nothing sits in front of it. I have found a way to cut it a little slack. A Concert Grand is not designed to be a drywall damaging component. It's a lot more subtle than that. It does everything well, just not in excess. The tone control circuit is overly complex for my ears, but with a little tinkering, I can get it to sound quite pleasant playing CD's. I tried using an equalizer, but that just made it louder. And, with the hotrod back I made, I can "watch" it work, look at the little "lamps and lighties" sparkle as it sings to me with the help of Norma Jean. If I want "boom" I can fire up the Marantz 2245 or my SX-1050. IF I want just plain good stereo faithfully reproduced, then the CG does it as well as anything.

And, another fact I'll have to admit. Did you ever own a car that was a great car, just not your FAVORITE car? Your favorite car was just your favorite, for a reason, or for no reason. That's how it is with the Magnavox 93 series amps. They are my favorite just because they are. Anything else I compare to them won't get a fair shot because they aren't a 93 series, which is really no comparison at all. So, perhaps Magnavox stereos can be different, with their own personalities, and can be part of my collection, favorite or not.

Had I built the CG, I would have used two 93 series amps wired as mono blocks. No biamps. I would have had a front-fired horn and 15" woofer with a side-fired 12". I would have kept the stereo reel-to-reel deck and made the remote work with it. The thing would have weighted 500 pounds, but it would have really sounded nice.....

[Firedome]

Why not make one like that, sounds like a fun project.

[electra225]

If I could find a parted CG cabinet, I might try it. It would make a fun project. The benefit of hindsight would be useful.....

[Hydrolastic]

Hello Greg, bear with me... so as you know I had not even heard stereo till about five years ago . and my electrical knowledge is limited to messing around with these consoles since 2018. I am a little confused about what your saying here..."I would have used two 93 series amps wired as mono blocks. No biamps. I would have had a front-fired horn and 15" woofer with a side-fired 12"."
Ok so the 9300 is a 25-30 watt stereo amp correct? can you elaborate on how you would turn them into a mono block? Would it be a full power mono block or would the power be cut in half like one channel. Also I was under the impression that the biamped part was that the high and low was always separated signal from the amp to the drivers. I don't know if the 9300 amp is biamped ? also what is this part about the woofer and horn facing forward and the 12" on the side. All kinds of things cross my mind here like impedance adding up to what the amp can drive. Then there is the question of what range does it fill in? The mid range ? What knobs control that ? Obviously you have been thinking about this. I am wondering if you could elaborate some more in detail. If I was using a discarded CG cabinet Idk if I would use the center remote area as a subwoofer cabinet. which leads me to a final question. How do you get a center subwoofer signal out a set of 9300 chassis/chassi. asking cause I just don't know.

[electra225]

Hydro, my comments were more of a "daydreaming" nature than a technical narrative.

I am not now and really have never been a fan of Magnavox bi-amps. I don't appreciate their performance and don't see their advantage over other amplifiers. The 93 series Magnavox amps are seven tube, regular old stereo amplifiers. If I was to use them as monoblocks, I would probably just feed one channel into both channels of the stereo 93 series and use two for stereo. I don't know anything about how to use a center channel with a 93 series amp. The 93 has that "sweet" sound all the guitar amp and console rapers like so well. I've never heard a 93 series amp that didn't sound good, and they all sound the same. The reason I would use a 15" and a horn front-fired and a 12" side-fired would be to somewhat replicate the speaker system in the Berkshire and the early Concert Grand mono instruments. I don't know the mathematical equations involved with my proposal of using a 93 for a monoblock. Would feeding one channel to both channels in a stereo amp cut the power in half? I don't know. Obviously, if I got serious about a project like this, those questions would need to be answered. There would need to be crossover networks designed as well. Some of Magnavox's external speakers used a 15", a 12", and a horn if I'm not mistaken, so that complement is not unheard of. As I said, this is more of a "daydreaming" project than a practical one.

When I was restoring cars, I wanted to put a 1956 Buick 322 V-8 and aluminum bellhousing Dynaflow in a '32 Buick "Vicky", a model 50 series Victoria coupe. I had it all designed and even bought an engine and transmission like I wanted. I found an outfit that would make headers for the 322. I was going to mate the early V-8 with a late Dynaflow trans. Jaguar front and rear suspension. Hydra-Boost brakes off a Chevy dump truck, mounted under the floorboards so I could keep the pedals original. A guy in west Phoenix was going to make a late steering column that looked like the '32 version and allow me to retain the original steering wheel. Since the original '32 engine was a straight 8, I was going to use the original radiator position for the air conditioning condenser, then move the radiator back 8" so I didn't have to use a huge fan shroud. I wanted an engine-driven fan, but would use an electric fan on the condenser. On and on like this, every little detail on paper. I even found a '32 Vicky body in a junkyard in Texas. Any missing parts were to be supplied by the '32 Buick expert from the Buick club. Everything was falling in place. Then I was diagnosed with Stage 4 throat cancer. Oh well, it was a fun project while it lasted. The shop I managed in Scottsdale had managed to repower a Rolls Royce with a 366 Chevy school bus engine, several V-12 Jags with either 500 Cadillac engines or 455 Olds. These vehicles used GM transmissions, so they begged to be swap projects. This was the inspiration for "repowering" a Concert Grand with 93 series amps. This kind of silliness is in my DNA I reckon.

[electra225]

While I'm waiting on parts for other projects, I was digging thru my file cabinet looking for the information on my Imperial, which I have misplaced. I'm sure it's not LOST, per se, I just can't find it. I haven't looked in the last place I put it, as the wife likes to point out.....

That said, I ran across the file for the Concert Grand. It is about two inches thick, full of informational goodies from when I went thru it back in 2014 and 2015. I also found something else I thought was interesting. I have both information from Sams and I have genuine Magnavox factory information, courtesy of Randy Bassham, who was a Magnavox guru from the old radio forum before ARF came online and in the early ARF days. The schematics for the 82 series CG amps are different between the Sams and factory versions. The 81 and the 82 series bi-amps are cathode biased. The listed cathode voltages on the Sams diagram and the factory diagram are different. Sams says 17 volts, factory says 15 volts. This voltage difference could make a difference in the tone, the bass response. I didn't dig thru the file enough to find the notes on what the cathode voltage in the CG was when I went thru it. In the interim, the motor on the changer has seized and the eye tube refuses to deflect on stations, so these systems need to have some troubleshooting done. As soon as I get a few more urgent tasks accomplished, probably the best bet for this, and for the Imperial, would be to just pull them both completely apart, set the electronics up on the bench and go thru them both completely again. I know there are circuit differences between Bill's Imperial, two years newer than mine and the one I have. And his speakers are sealed, mine are open. Now I see differences in the cathode voltage specs for the CG, so I need to check that out. This at least gives me a direction to take, which is what I was after. If I get the guts out of the CG cabinet, I'll tip the cabinet up on end and install a new set of casters like I did on the Stereo Theater.