Treb
Treb Reader
9/3/11 9:09 p.m.

I'm modifying the NOS radio in my wife's FIAT 124 spider. This is an AM mono 2-shaft radio. We're keeping the radio for its looks; the sound is pretty poor.

I've added a switchable ipod input and I've installed a single 4x6 speaker -- infinity, maybe? I can't remember.

The amp in the radio is noisy and distort-y. Needs moar powar. So I got a small old alpine amp off ebay -- I think the model number is 3505. Made a line-out direct from the volume knob of the OEM radio, etc. etc.

Hooked everything up... and no louder than the old setup. Cleaner, but no louder. Conversation - level when turned all the way up. Not what I was looking for.

So, first approach: can I make this louder? There are two channels to this amp; I'm only using one right now. If I put the same signal into both and hook both outs to the same speaker... will it be any louder? There is no "bridge" type switch or anything. Second possible way to make it louder: there is a round connector, 7 or 8 pins, in the case. I have not connected anything to it. Is it possible that one of those is a volume control or something?

Second approach: who has, or can recommend, a small mono or bridgeable amplifier? And how much power should I need to drive one 4x6?

Matt

madmallard
madmallard Reader
9/3/11 10:42 p.m.

the pot may not have a very big range?

fast_eddie_72
fast_eddie_72 Dork
9/3/11 10:53 p.m.
Treb wrote: Made a line-out direct from the volume knob of the OEM radio

How did you go about this? I'm guessing the line-out isn't supplying enough signal. I'd use a speaker to line level converter. In fact, I did for a long while until my factory stereo broke. Worked really well.

Shoot, it's sitting here taking up space. Pay shipping and you can have it.

Alpine amps (old and otherwise) are super-duper.

(edit) Oh! Running the input to both channels is fine, but running both outputs to one speaker is a no no. You're sending one channel's output in to the other channel's output. Amps don't like that. Would be fine to run it to a second speaker. But as low as you're describing the output, I'm sure that's not your problem. My 10 or so WPC tube amp is making well above conversation level right now. I'm sure your Alpine is capable of making more power than that.

(Post edit) Just looked up the 3505. Well, that is a little flea of an amp! But all the same, 18 watts should make well more than the kind of level you're talking about.

Treb
Treb Reader
9/4/11 10:54 a.m.
fast_eddie_72 wrote:
Treb wrote: Made a line-out direct from the volume knob of the OEM radio
How did you go about this? I'm guessing the line-out isn't supplying enough signal. I'd use a speaker to line level converter. In fact, I did for a long while until my factory stereo broke. Worked really well. Shoot, it's sitting here taking up space. Pay shipping and you can have it. Alpine amps (old and otherwise) are super-duper. (edit) (Post edit) Just looked up the 3505. Well, that *is* a little flea of an amp! But all the same, 18 watts should make well more than the kind of level you're talking about.

I made the line-out by opening up the case and bypassing the amp stage of the OEM radio -- snipped the signal and ground leads going from the volume pot to the amp board. Ran those two out of the case and to the inputs on the Alpine.

I had initially tested it using the headphone out from an ipod. I had a headphone cable that had been cut on one end; hooked up ground and one channel's signal. The level out of the volume pot is very similar to that.

Are you suggesting hooking up the amp board inside the old radio again, and using the OEM speaker outs to go to the speaker-to-line-level converter, to the amp?

Wouldn't that have the same crackly/distort-y sound as the OEM radio (but louder?).

I don't necessarily understand what I'm doing, here; I'm just willing to mess around.

Thanks for the help! Matt

fast_eddie_72
fast_eddie_72 Dork
9/4/11 11:57 a.m.

Well, it's really hard to say for sure. "Line level" signals vary a lot and what the internal "line level" of your radio is may not be enough to drive the Alpine to full output. Plug your iPod directly into the Alpine and see if it doesn't get louder.

Yes, I was suggesting using the internal amp and stepping it down to line level with a converter. As for how it would sound... it depends. I would bet a lot of the sound quality issue you had is due to low power. So more power from the little Alpine would sound better. Like I said, I did that with a factory Toyota stereo. I didn't want to worry about thieves in my T Top MR2, so stepped the factory stereo down to line level and into an Alpine amp and good speakers in factory locations. It made a huge difference. I will say, replacing that recently with an Alpine head unit made it sound better.

Try the iPod into the amp and see what that gets you. It will give you more information at least. If that makes it a lot better, might should try to figure out some small, inexpensive pre-amp.

Treb
Treb Reader
9/4/11 2:05 p.m.

My initial test was from the iPod headphone jack direct to the Alpine.

Sound was pretty similar to the second test, which was iPod (dock connector)-> iPod charger/preamp (volume set at full)-> switch-> volume knob in old radio-> Alpine.

Matt

Treb
Treb Reader
9/4/11 3:35 p.m.

So, googling about, I found a discussion of the little amp that I have that included this line:

"I have the same amp and the 8 pin plug has a black(ground), red(power) and 2 rca female plugs/ black and red."

So, here's my thought. Is it possible that the input I'm using right now is for speaker-level inputs, and I'm feeding in a line-level signal; but line-level signals should really go through this 8-pin connector? I don't, obviously, have the connector for it.

Alpine's website is supposed to have manuals and so forth in the support section; but no results on a search for 3505.

Thanks Matt

fast_eddie_72
fast_eddie_72 Dork
9/4/11 5:50 p.m.
Treb wrote: So, here's my thought. Is it possible that the input I'm using right now is for speaker-level inputs, and I'm feeding in a line-level signal; but line-level signals should really go through this 8-pin connector? I don't, obviously, have the connector for it.

Maybe. The input you're using now- is it RCA jacks or wires? A line level input will almost certainly be RCA jacks (or perhaps this 8 pin DIN). If it's wires, you are probably exactly right.

peter
peter Reader
9/4/11 6:00 p.m.

Do amps work properly if you only have one speaker connected? My physics of electronics class was ages ago, but I wonder if it's hard for the amp to drive a load on one side while remaining open-air on the other?

Curmudgeon
Curmudgeon SuperDork
9/4/11 7:24 p.m.

Is there a potentiometer on the amp for 'level input' or 'sensitivity'? All the Alpine amps I have ever owned (I have one in the Trooper now, for instance) have that. Turn up the sensitivity and the volume goes up.

Treb
Treb Reader
9/4/11 8:11 p.m.

Curmudgeon: no, there isn't a pot on (or in) the amp. I looked...

fast_eddie_72: the input I'm using now is wires. There is a bundle of wires in to the amp -- power, ground, speaker out, and 3 input wires. There's also the 8-pin, which I guess I need to trace and figure out which pins are the inputs. ??? There are no RCA jacks on the amp.

Matt

fast_eddie_72
fast_eddie_72 Dork
9/4/11 8:33 p.m.

In reply to Treb:

Well, that really sounds like the answer. You can probably find the plug you need on ebay. Just search "8 pin din".

The pinout info you need might be here.

http://doswa.com/2010/01/01/diy-aux-input-on-alpine-car-stereo-m-bus.html

They would have had to be consistent in the wiring, I would think.

Treb
Treb Reader
9/4/11 8:48 p.m.
fast_eddie_72 wrote: In reply to Treb: Well, that really sounds like the answer. You can probably find the plug you need on ebay. Just search "8 pin din". The pinout info you need might be here. http://doswa.com/2010/01/01/diy-aux-input-on-alpine-car-stereo-m-bus.html They would have had to be consistent in the wiring, I would think.

Awesome. Will report back!

Matt

Treb
Treb Reader
9/5/11 11:46 p.m.

Yep, that did it.

Thanks! Matt

fast_eddie_72
fast_eddie_72 Dork
9/11/11 2:35 p.m.
Treb wrote: Yep, that did it. Thanks! Matt

Awesome!

On a related note, I found an Alpine CDM-7833 in a Mercedes at the You Pull And Pay today. Pulled it out and brought it home. Well shut my mouth, looks like it works! And it has the same connector.

I did a little more research today. Alpine called it an "M Bus". Not sure what that means, but they do make all kinds of adapters for it. I found loads of aux in stuff, but no aux out! Huh. So good to know that seems to be the answer. I'll wire up my own in/out plug and be able to use my iPod and an external amp. Or maybe dig up an old Alpine amp like you did!

fast_eddie_72
fast_eddie_72 Dork
9/11/11 2:45 p.m.

Hum, actually, I'm kinda of confused.

M Bus looks like it was just intended for cd changers. Sure looks like the same plug. Strange. Not sure how it all works. Going to have to do some more research. Lots of info out there though.

Oh well, glad you got your amp working!

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