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Author Topic: 70-77 Radio, 8 track, Bluetooth upgrade??  (Read 285 times)

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Online b_hill_86

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70-77 Radio, 8 track, Bluetooth upgrade??
« on: December 31, 2018, 06:57:16 PM »
Well I was going to wait to post anything about this until I tried it and could attest to whether or not it works the way I plan BUT in order to keep Roger from pulling the plug, here goes.  ;D

After 8 years of owning my car I finally installed some speakers and a modern single DIN radio in my map pocket since my radio opening is uncut. Some previous owner of my car bent the area around the package tray speaker holes to drop 6x9s in rather than mount from below. Not sure if I should have tried to bend it all back straight-ish but in order to fit my new speakers I had to bend a slight bit more....

Anyway, my current setup isnt anything fancy but sounds as good or better than my 2010 Ram which has a decent stereo. I did the dual coil front speaker and the two 6x9s i mentioned already. All are modern 4 ohm speakers. My only gripes are I don't care for the look of the modern radio in the map pocket and that particular radio I have (though it sounds great) lacks bluetooth which leads me to my plan.

I had a 70-77 delco radio I bought a few years ago in rough looking shape for pretty cheap but it was DOA when I tested it this year. I took it to a local vintage audo shop and though they were able to clean it up and replace the lens there was apparently a fried chip on the original amp that couldn't be sourced nor replicated apparently. Their solution was to add a modern amp which would now power a left and right channel via positive and negative wires for each channel contrary to the common ground used all fine and dandy except Iíve always wanted an 8 track player added into the mix which now probably wonít work with the converted stock radio and 4 ohm speakers.

Part 1 of my plan is to head back to said audio shop with my recently purchased 8 track player to see if they can maintain the same functionality of the 8 track but install a modern amp into it like they did with the radio. That way in theory I should be able to connect the factory radio to the 8 track track player which in turn connects to the speakers in relatively the same way it did in itís factory set up. With no tape in the radio should get power and send the speaker signal through the 8 track to the speakers and went to tape is inserted the tape player should cut power to the radio  and play the tunes through the modern amp into the modern 4ohm  speakers.

Part 2 of my plan is this amplifier.

https://www.walmart.com/ip/Kenwood-KAC-M1824BT-Compact-400-Watt-Bluetooth-Connected-4-Channel-Amp/44641023?wmlspartner=wlpa&selectedSellerId=5700&adid=22222222228032076958&wl0=&wl1=g&wl2=m&wl3=61126786856&wl4=aud-566049426705:pla-108530188136&wl5=9015090&wl6=&wl7=&wl8=&wl9=pla&wl10=117878170&wl11=online&wl12=44641023&wl13=&veh=sem&gclid=EAIaIQobChMIhYiCr6_L3wIVhjxpCh3X1weoEAQYAyABEgItXPD_BwE

In case the link expires itís a kenwood KAC-M-1842BT. It is 400 watts which should be plenty for me, small enough to mount in several places, has speaker or line level inputs which  should make hooking it up to my factory radio and eight track player, which will have speaker level outputs, easier and the icing on the cake is that it has a Bluetooth radio built-in with a separate controller. You can either control your music directly from your phone or using the controller which I plan to run through or out from under the center console so it is not noticeable.  I am also going to use a splitter to split the left and right channel so that there will be two left and to right channels from the 8 track/radio combo so I can power all four channels of my current speaker set up. I will still have the factory balance control with the eight track player and the radio and the amp has fader control built-in for the Bluetooth function only.

The last thing  I will really be lacking is an equalizer to adjust sound quality. I will still have the tone control from the 8 track player and the factory radio but that will probably be the extent of how I can manipulate the audio. For music I play on my phone, which is probably honestly what I will do more often than not, there are a few apps that I have played with that function as a graphic equalizer so I should be able to fine-tune the sound of my Bluetooth audio. But I will also be able to pop a tape in or turn on the radio and at least have decent audio from it.

Sorry this turned out way longer than expected. LIKE IT? DONT LIKE IT? Any comments or feedback is welcome and appreciated. Iím no audio guru so if you foresee problems with my plan please let me know.  I just thought some others may like to see in case some of what I do benefits them. Ultimately to the overall cost of installing this is going to be relatively small. And yes I know I could mount my current single DIN radio in the glove box but honestly Iím not crazy about that idea and still lack the Bluetooth function.
« Last Edit: December 31, 2018, 08:42:05 PM by b_hill_86🤠 »
-Brian-

1977 Trans Am 400 4 Speed Hardtop

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #1 on: December 31, 2018, 08:39:24 PM »
Also, in case anyone is wondering, I haven't tested this but in theory, for those who have a factory radio and/or 8 track which require 8-10 ohm but you want to use modern 4 ohm speakers for whatever reason the solution is similar to above. You should be able to either utilize an amp like the one I posted above to take speaker level inputs from the radio/8 track and run them through the amp. Then you should only have to worry about the required resistance of the amp and not the radio/8 track because the amp is driving the speakers. If you didn't want to use an amp with speaker level inputs there are converters that convert speaker level from the radio to line level which is standard input for most amps. Ive read there is some loss of audio quality by using speaker level inputs but I can't confirm nor deny it as I haven't tried it.
-Brian-

1977 Trans Am 400 4 Speed Hardtop

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #2 on: December 31, 2018, 11:03:26 PM »
I did a stealth install in my Ď86 T/A back in the 90ís.  The car came with a factory cassette deck (double din).  I sunk a Sony CD receiver in the stock radio location and then cut the face off of the factory cassette head unit. It covered the CD receiver completely - I also cut up a cassette tape and left it sticking out of the dummy faceplate.  It made a convenient handle to pull the dummy radio faceplate off to access the Sony.

Point is what you can do with these things is almost limitless.  My Ď78 dash is uncut too - if I were doing an 8-track in mine Iíd probably use the 8-track cassette as a stealthy holder for my phone and then build a 2nd system for the car that directly connects to the phone... use an a/b type switch to swap between the 2 systems.

The street rod (especially rat rod) guys do a lot of hidden systems like this - you can probably get some good ideas from their forums etc.  there are some small USB and 3.5mm, etc., adapters that can be used to drive systems out there.

Good luck and have fun!

Offline gilbertsta

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #3 on: January 01, 2019, 12:37:31 AM »
Props to you for coming up with a plan like that. Itís gotta work. I like to cut holes in my door panels for speakers, so what do I know? Being able to make adjustments from your phone would be cool. I like angry birds suggestion of a stealthy 8 track. My ďNewĒ stereo is already outdated as I have a hidden iPod in it. The iPods that are not made anymore. Lol.

Online b_hill_86

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #4 on: January 01, 2019, 10:50:47 AM »
I do like angrybirds idea. May be an option if my 8 track turns out to be a paperweight. It was advertised as working but o lynpowered up when I tested. Nothing but buzzing through the speakers. The audio shop is closed till Jan 7th so weíll see.

Whatís your iPod setup? Just curious
-Brian-

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #5 on: January 18, 2019, 09:53:58 PM »
Well, 8 track works now but after I spent some money on it. Iím waiting for my bill but the seller of the 8 track apologized and asked for a copy. Iím assuming for a partial refund which would be nice. Wonít hold my breath though.
As far as my idea, the whole common ground speaker output on both the radio and 8 track caused me an issue. It appears there is no way to hook that kind of output to a modern amp. My solution is to create a line output on each source which I can then run to a stereo rca splitter with a switch on it. Switch it one way and the radio will feed into my amp. Switch the other way and the 8 track will feed into the amp. The shop is working on creating the line outputs and heís going to show me how to reverse it in case I ever want to return either piece to stock form.

Attached is a crude drawing of my plan
« Last Edit: January 18, 2019, 09:55:09 PM by b_hill_86👮‍♂️ »
-Brian-

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #6 on: March 25, 2019, 08:52:36 PM »
Havenít had a lot of time lately but I did get the 8 track and radio back both with line outputs.

Hereís a short teaser of it hooked up with line outputs to my home amp. Stock speaker outputs are supposed to work still. Still messing with it but I do have a bit of distortion with amp volume low and 8 track volume up. And the right channel is a little quieter than the left so weíll see if I can work that out.

-Brian-

1977 Trans Am 400 4 Speed Hardtop

Offline Burd

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #7 on: March 25, 2019, 10:55:25 PM »
Nice work👍🏽
1978 YEE

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #8 on: April 25, 2019, 05:43:53 PM »
Made some progress. Both the radio and 8 track are hooked to the Bluetooth amp driving 4 modern speakers. Radio sounds surprisingly good! 8 track, not as much and itís okaying a little fast so I have some adjustments to make. Bluetooth sounds very good too! So far Iím very happy with the setup.





-Brian-

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #9 on: April 27, 2019, 10:10:28 AM »
Thereís a screw for the speed, you may make to take the cover off.  Itís been so long, I adjusted mine.  Iíd put a new belt on if you remove the cover.   
1978 YEE

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #10 on: April 27, 2019, 11:18:44 AM »
Nice work!

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #11 on: April 27, 2019, 01:46:49 PM »
Belts were changed and I did end up finding a speed adjustment. There is still a hum and higher volume causes some distortion. Probably some result of the newly added line outs. Iím
Gonna see what the shop that did the line outs says. Otherwise I think it sounds pretty good and Iím really happy with the radio and Bluetooth.

Thanks angrybird im honestly a little surprised it worked.
« Last Edit: April 27, 2019, 06:01:26 PM by b_hill_86 »
-Brian-

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #12 on: June 03, 2019, 07:20:48 PM »
Iíll probably do a video update for fun but I got the 8 track back from the shop again. Before I took it back I hooked up some 8 ohm speakers to the factory outputs and I had a great sound, great volume without distortion and no hum. Obviously though with the common ground speakers I wasnít able to make use of those outputs even though my amp has a speaker level input option. HOWEVER once I told the shop this what ended up doing was, what I think is the cheapest, best and EASIEST option for anyone trying something similar with a radio or 8 track player.

He ended up using a speaker level to line level converter that cost about $5. I had considered this option before but wasnít sure if it would work with the common ground speakers and I could not find one single reference to it online or elsewhere and believe me I looked. All he did was connect one speaker output to one (left) positive lead on the converter and the other speaker output to the other (right) positive lead and grounded both negative leads to the player chassis. I tested it today and it worked great! As far as I can tell this is the best way to hook up a pre 78 radio or console 8 track to a modern amp. Hope it helps someone. Iíll post some pictures and maybe a video later.
-Brian-

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Re: 70-77 Radio, 8 track, Bluetooth upgrade??
« Reply #13 on: June 05, 2019, 12:38:35 PM »
So my radio had a fried chip in it that couldnít be fixed or a replacement sourced at the time I had it in the shop. Now the guy thinks he can build the part but in the meantime he built his own amp for the radio but it uses positive and negative wires for each channel instead of one wire per speaker like factory. For that reason I couldnít hook it to the 8 track player the way the factory did. And he added line outs that work great unlike the line outs on the 8 track hence the switch you see me press in the video. That changes the amp input from the player to and radio and visa versa. But I THINK if a person had a radio and 8 track they could use a line level converter on the outputs at the 8 track and it would convert the radio signal with a tape out and the player signal if there was a tape in.

-Brian-

1977 Trans Am 400 4 Speed Hardtop