: 1961/62 Motorola SK75-MA  ( 1447 )

SeniorSteve

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Re: 1961/62 Motorola SK75-MA
« #15 : April 26, 2020, 01:30:17 PM »
My favorite would be the "Declaration" model by Drexel.  Very clean lines and I'm sure it sounded sweet! 
I think this model ran for several years with different "SK" models.  I also like the rounded tuner dials. 

TJ

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Re: 1961/62 Motorola SK75-MA
« #16 : April 26, 2020, 01:48:46 PM »
My favorite would be the "Declaration" model by Drexel.  Very clean lines and I'm sure it sounded sweet! 
I think this model ran for several years with different "SK" models.  I also like the rounded tuner dials. 
I've always wanted a Motorola in the Drexel "Decleration" cabinet.  They use same components as my other high-end Motorola's, so I know they sound great. 

Motorola built some really nice stuff back in the day.  Their quality was good, nice furniture, and good sound.  They were right up there with Magnavox.  It's a nice looker Trevor.
What I want to know is if Motorola was unique in working with a furniture company, Drexel, to sell components in furniture that people could buy that matched the rest of their furniture set.
My Consoles:
1962 Motorola SK112CW-FM, All original tubes
1958 Magnavox Continental - DIY Concert Grand!
1957 Magnavox Brittany - Amp 148 Magic!

Bill

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Re: 1961/62 Motorola SK75-MA
« #17 : April 27, 2020, 06:54:28 AM »
The photo that Senior Steve provided is my Motorola, and mine is complete with reverb.  The only difference is mine has short legs.  It's a low rider, so to speak.  :) ;)  My cabinet needs complete refinishing, and I have yet to do the rebuild on the electronics.  I guess I have put this one off because of the cabinet.  When I got it, the mice had used it for a hotel, someone must have used it for there tunes as they drywall their home.  It had about an inch of drywall dust everywhere, and the top was stained and full of deep scratches.  It's been completely cleaned of all traces of mice and drywall dust, but the rest is still waiting restoration.  I have a friend who has his parents Motorola that looks just like Senior Steve's photo.  Unlike mine, his looks brand new.  It's electronics need restoration as well, and he has hinted a couple of times that I should do it.   ::) :)

I'm not sure why Motorola partnered up with Drexel or Heritage, but it's a good thing they did.  High quality furniture along with good electronic's made a good match.  Early on in Magnavox's life they also used Drexel for some of their high end cabinets.  Somewhere around 1964-65 RCA stepped up their cabinet making as well.  I'm not sure if their high end cabinets were farmed out, or in house, but my Grandparents 1966 RCA Stereo Theater is solid maple, and weights a ton.  It's a fine piece of furniture.

Bill


Bill

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Re: 1961/62 Motorola SK75-MA
« #18 : April 27, 2020, 06:56:51 AM »
Trevor!  I forgot to ask, do you nave any photos of the guts of your newest Motorola?  I would like to see what the amp that uses the 6V6's looks like.  Mine has 6BQ5's and 6BM8's. 

Thanks,
Bill


TJ

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Re: 1961/62 Motorola SK75-MA
« #19 : April 27, 2020, 12:50:55 PM »
Here is a link to the Google Photo album for the SK75. 

https://photos.app.goo.gl/snFYCkxGrwCSqqsSA

Enjoy
My Consoles:
1962 Motorola SK112CW-FM, All original tubes
1958 Magnavox Continental - DIY Concert Grand!
1957 Magnavox Brittany - Amp 148 Magic!

Bill

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Re: 1961/62 Motorola SK75-MA
« #20 : April 27, 2020, 03:43:39 PM »
Thanks Trevor!  Interesting comparison.  Chassis looks similar, but the transformer is different, and of course the tubes. Looking at yours, and you saying how good it sounds, is giving me motivation to start mine.   ::) :)

Bill

TC Chris

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Re: 1961/62 Motorola SK75-MA
« #21 : April 27, 2020, 06:37:41 PM »
What was the frequency or range at which Motorola crossed over from two-channel for highs to one channel for bass?  Was it a sharp transition or gradual?

Chris Campbell

TJ

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Re: 1961/62 Motorola SK75-MA
« #22 : April 27, 2020, 08:07:11 PM »
What was the frequency or range at which Motorola crossed over from two-channel for highs to one channel for bass?  Was it a sharp transition or gradual?

Chris Campbell
I'm not sure of the frequency ranges, in fact, I'm not sure how Motorola is even doing the crossover.  When you look at the schematics for the three-channel amps, there are no crossover networks like on Magnavox.  The only way I think they did it is with capacitors and resistors.  They do a crossover capacitor between the 8" midrange and the 5.5" tweeters, but, there is nothing on the amp itself for the bass channel.
My Consoles:
1962 Motorola SK112CW-FM, All original tubes
1958 Magnavox Continental - DIY Concert Grand!
1957 Magnavox Brittany - Amp 148 Magic!

Motorola Minion

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Re: 1961/62 Motorola SK75-MA
« #23 : April 29, 2020, 11:02:56 AM »
What was the frequency or range at which Motorola crossed over from two-channel for highs to one channel for bass?  Was it a sharp transition or gradual?

Chris Campbell

The crossover is probably made unnecessary by the fact a bass channel is dedicated. The SK112 sounds like the power to drivers is balanced such that tone controls do not need to be tweaked to compensate, like on a combined channel.

 This means that power to the mid range 8" and tweeters has very little low frequency content. There is no need to separate and divide the power sent to HF drivers, in order to protect them from LF-induced damage.
Tubes - Magical - Tubes

Dave

TJ

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Re: 1961/62 Motorola SK75-MA
« #24 : April 29, 2020, 12:22:10 PM »
What was the frequency or range at which Motorola crossed over from two-channel for highs to one channel for bass?  Was it a sharp transition or gradual?

Chris Campbell

The crossover is probably made unnecessary by the fact a bass channel is dedicated. The SK112 sounds like the power to drivers is balanced such that tone controls do not need to be tweaked to compensate, like on a combined channel.

 This means that power to the mid range 8" and tweeters has very little low frequency content. There is no need to separate and divide the power sent to HF drivers, in order to protect them from LF-induced damage.
If you look at the Magnavox Bi-Amped units, they have coils on the amp that filter frequencies so that the bass channel only gets bass and the upper frequencies go to the horns. 

Motorola is kind of bi-amping the console having a dedicated bass channel, but the question of how are they directing bass frequencies to the bass channel and everything else to the other speakers? 

My Consoles:
1962 Motorola SK112CW-FM, All original tubes
1958 Magnavox Continental - DIY Concert Grand!
1957 Magnavox Brittany - Amp 148 Magic!