Factory Delco Stereo Problems

[Jak220]

Doing restoration work on my '84 K10, the original radio was missing out of it, so I picked up a nice factory Delco stereo with a cassette player off eBay. (Call me old fashioned, I just enjoy cassettes). The radio has been refurbished, and the seller told me it worked perfectly when he bench tested it, given that it's in amazing shape and everything else works perfectly I'm inclined to believe him. However, the audio sounds very distorted, like the pitch is very off at certain frequences. The audio itself is crystal clear, no static or popping, but the pitch is very off. I know these factory radios don't have the best reputation and I can't expect too much, but I do think the problem lies somewhere else and was wondering if you guys had any suggestions as to where I should start troubleshooting.

Would appreciate any help ya'll could lend!

[jwpa2]

You got lucky it works, I did that and ordered one from ebay and the one I got did  work. so don't know what i'm going to do as for a radio yet.

[VileZambonie]

Try listening to better tunes 

[JohnnyPopper]

Notwithstanding VZ's gig  , have you adjusted the treble/bass knob?

When you say the pitch is off, what does that sound like, as in vocals, instruments, etc.? Or overall?

What comes to mind is that your amperage from the head unit does not match the speakers in impedance or power requirements.

[Jak220]

It's mostly instrumentals, voices sound a lot clearer. If you've ever heard a walkman or portable stereo's batteries start to get low, it sounds kind of similar to that which is why I thought it was a power thing. The truck and the radio are both wired up for 4 speakers, 2 dash and 2 rear speakers but I only have the 2 dash speakers hooked up right now. The speakers I got from   Truck, https://www. competitor.com/1973-87-chevy-gmc/cc-csb-1985-91-replacement-dash-speakers

I got the ones labeled 85-87 even though my truck is an '84 because they didn't sell any dash speakers pre-85 but I feel like they wouldn't change impedance/power requirements between those model years. Could be wrong though.

[JohnnyPopper]

I looked up the speakers, you're not going to get a full range/bodied sound out of such small speaker. Makes sense that the vocals are clear, they are in the upper frequencies, which those should reproduce well.

Still, have you adjusted the bass/treble wheel that is generally outside the volume knob?

Does the radio have 4 speaker outputs or two?

What is the Ohm impedance of your dash speakers? Website didn't specify.

Also, what is your radio spec's in terms of power and impedance? (Ohms rating)

Keep in mind, it's very important to match the speakers to the amp output in terms of Ohms ratings. You can fry your amp right quick with the wrong setup.

If you can find out the answers to those questions we can move the ball forward and get you a decent sound system.

[Jak220]

I haven't tried adjusting the bass/treble wheels, (I'm assuming those are the little pointed chrome pieces behind the volume and tuner knobs) so that's definitely something I'll have to mess around with more. The radio has 4 outputs, the 2 dash speakers, and the rear cab corner speakers (haven't had the time to buy new rear speakers and hook them up so I just left the rear output unplugged). I tried to look afterward when I became concerned it might be an impedance issue, but like you said it doesn't say the ohms anywhere on the website, I might try emailing  . I'm also not sure where to find the specs for the radio, I'll message the guy I got it from. If you had recommendations for front speakers and 6x9's for the rear that matched the amp/resistance requirements of the radio once we figure that out, I could definitely try that. For now, I guess I'll try messing with the bass/treble controls and make sure the ground is good/put some dielectric grease on there. Thanks so much for the help and I'll let you know when I know more! (Also attached a picture of the unit just for reference)

[zieg85]

Make sure you have the OEM speakers.  Many replacement speakers although "fit" the ohm rating is not the same.  The stock radio will distort big time if the ohm rating is too low.

[JohnnyPopper]

You can always use an Volt/Ohm meter. Don't be worried if they don't peg precisely at 4 or 8 ohms, close is good enough.

Now if they read 2 you might have a problem.

You might be able to look up the model number of the deck to see what impedance it was designed to handle.

You're right about the adjustments. Bass/treble on the left, if the right moves independent of the tuner, it may be a balance fader between the front and rear speakers.

It it were me, I would look for a 6x9 that is the woofer only.

If you go full range, the mid and high freq's will be lost and distorted as they aim into your backside, just muddies it up.

If you can't find a decent pair, you can always snip one of the leads going to the tweeter. Sometimes they enter through the back of the center of the magnet, others are drawn through the paper cone of the woofer. Just one, in case you want to reattach.

[Jak220]

Just heard back from the guy I bought the speakers from, he said he used 10 ohm Delco speakers when he was bench testing them so that kind of answers that question. I still haven't heard back regarding the speakers I bought, but hopefully, I will soon. Thanks for the advice on the rear speakers as well, I will keep that in mind. Do you have specific recommendations for the dash speaker? I've been having difficulty finding pretty much anything in the 8-10 ohm range online.

[Jak220]

Another update: I got an email back and they said the speakers I ordered were listed as 4 ohms so that's definitely at least part of my problem if not the whole issue. I will keep looking for 10 ohm speakers but in the meantime like I said if anyone has links they could drop for front and rear speakers I'd definitely appreciate it bc they are hard to find with that ohm rating.

[zieg85]

I am not going to say it will be impossible but it will be tough finding a 10 ohm speaker.  My last build is going to be with all OEM parts.  My 85C20 was a radio delete truck and I have several sets of speakers and complete original wiring for them saved.  It will be some time before I get to that one.  Every truck I ever parted I pulled the speakers that sounded OK.  After all these years they look OK but haven't revisited this.  I am OK with the original sound of the stereo's of that era and for as much as I will be in the truck that is good enough for me.  My current build is a radio delete truck and I will probably go modern 1.5 DIN with CD under the dash.  Best of luck with whatever direction you decide to go with.

[shinkle]

Look at   for correct factory replacement speakers.  I purchased a pair and actually talked to the company supplying  , its about the only place to find the correct 8 ohm speaker.

[JohnnyPopper]

uh oh, seems you mentioned that which should never be.

Led Zeppelin "What is and what should never be"

[Mike81K10]

BTO, ZZ Top, Eagles, Stevie Nicks, Meatloaf, and many others! I have much of the 70s and early 80s on Cassette and have a Pioneer Super Tuner I will put back in. My Super Tuner fits the original mounting hole.