s/n ratios

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I am temporarily replacing a Pioneer DEX P78 with a Rockford Fosgate HU and it brings me to an interesting question. The CD S/N ratio for the RF is listed as 90 dB. The pioneer lists theirs as 120 dB. I know what S/N ratios are, but how does that affect the qualities of the sound that makes it to my ear? The Pioneer was a 4v preout and the RF is a 5v. Would that additional signal (and its corresponding lower amp gain) compensate for something like this? How important is that number?
 
Hello again. Lets see if I can shed some light hear. From my years in the car audio biz my opinion on the higher voltage preamp outputs is pretty much hype. I am still a big fan of older Eclipse decks and some of then are not even 2.8V out and I have no problems or one once of added noise. IMO if you route your wires right and have good equipment and solid grounds the preamp output is not that big of deal.

As for the added S/N I dont think you will probably be able to tell the difference. Heck I am running full Eclipse DDL/GFO (direct diggital link/ glass fiber optics, its old but man its still sweet, no RCAs between the deck, dsl and changer, all digital) system in my SQ car and its only rated at 108db and it is cleaner then just about anything else I have heard in a car. I think that in todays world most source units are about the same within reason. I used to work at a car audio shop that had a nice PASS switching system in the sound room and with everything set to 0 and no DSP or loudness going it would really hard to tell the differnce between one deck to the next within a reasonable price rate.

Also, as for the gain thing, if your amp is of desent quality turning the gains up to match the lower v out of the deck is not going to add much, if any, distortion. In car SQ car that is running the Eclispe DDL stuff it was qut hard to match it the my McIntosh amp. The way it ended up in the end was the gains on channels 3 and 4 (got the sub) is running at about 95%. I have competed at local events with this setup and plan to do bigger shows as soon as I get teh install looking the way I want. I can tell you from what everyone says after they listen to it, it is quit amazing, crystal clear with a great sound stage.

NOw for the not so techy stuff. Someone once told me the RF decks were made by Delco. I have had many bad runins with RF amps. For some reason I never had one that would not go up in flames but back then my old Coustic Power Logics would never die running the same system. It was also not a big selling piont when I go to the big IASCA Spring Break Nationals in Daytona Beach and RF have a big tent setup outside to fix all the blown RF amps through out the weekend. I did not see any other company have to fix that many amps. Make me think either they are really really behind the people competing or there stuff is just not all the reliable. Going on my past with RF I pick the later. So for me the RF would be out. I have work quit a bit bit with the Pioneers and really have nothing bad to say about them exect for there stupid wiring which I think they have changed to the standard colors now. I would look into either a Clarion are my person choice of course would be Eclispe. Both are great decks with good usable features.

Let me know what you come up with.
 
Hi Volt Decks

Well, it's not hype, but a misunderstanding of what a high voltage output deck really does in your system. It does NOT automatically guarantee a noise free system, or even a quieter one. An amplifier's gain is set to deliver, say, 50W with a 1v input. At 0.5V input, it will deliver 25W, all things being equal. If you place a high voltage output deck in your vehicle you will need to turn DOWN the gain on the amplifier to deliver the same power output. Now - what do we know about gain and noise? More gain equates to more noise in the preamp circuits of a typical car audio amplifier. So by turning the gain DOWN, you're benefiting from less noise produced by the amplifier, while retaining the same power output.

It's all implementation.

RF decks WERE built by Delco, though I don't think they are anymore - this has nothing to do with RF amps, which we know are poorly built. Delco builds the finest tuners available and a very solid performing radio. Delco is responsible for the hybrid ceramic SMD platforms in the old RF Punch series amps, too....the ones that didn't burn up as quickly. 🙂

Coustic Power Logic amps were poorly manufactured, and marginally engineered - but they sounded great and, as you said, never die. They did a lot with cheap parts!
 
hi volt decks

Here's my reasoning for a high volt deck (and tell me if I'm on the right track) I had some real problems with induced noise from the alternator and the fuel pump (which resides about 7" from the amplifiers). I tried routing the power wire on different sides, running the RCAs on opposite sides, noise filters and the works. I bought this Pioneer 4v deck and was able to do exactly what you were talking about; drop the gain on the amps and bingo: noise gone. My thinking was that since the alt and pump induced a fixed amount of voltage (lets say 0.1v), it was comprising a higher percentage of my signal with a 2v deck. I got the idea sorta backwards from doing theater sound design. Although I was grossly unqualified, I found that running Hi Z signal all the way back to the board picked up everything, so I put the amps under the stage and ran Low Z to the board and induced sound went away. Is my reasoning right? The amps are certainly sensitive enough to pickup even tiny voltage so I don't need it for SPL or SQ, but it sure did make the noise go away.
 
Close enough

That's close with your Lo-Z comaprison. A Lo-Z (low impedance for everyone else) is typically also a balanced connection in which a high voltage (12-30V) low current signal is passed between two hot lines with a shield connected at the source end to ground. The two hots are a difference signal, that is, they are out of phase with respect to each other. The receiving end is a differential input comparison amplifier that looks ONLY for a difference signal. When noise is induced on to the signal cable, it appears in BOTH hot lines at the same time (especially if they are twisted). That is called common noise mode and the receiving amplifier rejects any common mode signals.

OK *cracks knuckles*... 😀

What I previously explained about Hi-Volt decks is exactly what results - you don't have to have the amplifier gain up as high, so you are rejecting small signals by virture of lowering their volume. It's not the same thing as complete common mode rejection - and it would be impossible to accomplish this using an unbalanced cable. Gain structuring is a completely relative process, and the hi-volt decks make it easier to maintain a low noise system by overcoming some faults of linked components. The result is a "darker" background, which really makes CDs sound their best. Of course, you have to have a clean signal inside the deck for the benefits to really emerge. I have an older Alpine 7930(?) Tuner/CD that has significant "hisssss" that starts at volume "1" on zero bit tracks off the IASCA disc. I wouldn't use it in a SQ system, but my Kenwood X815 Deck is extremely quiet and very clean.:nod:

I have built line drivers and receivers for car audio and they all have a S/N ratio over 110dB, A weighted. Their CMRR is over 90dB - you can't get a better style of signal transfer, but balanced lines have not been widely accepted in mainstream car audio. I think Zapco has their Symbilink and Kenwood had a Balanced line of Excelon amps...and a smattering of ultra high end Sonys, Pioneers and Alpine stuff is balanced.
 
Hello,

There is so much mis-information out there in car audio.

For the record, all Rockford head units pre-out voltages are rated RMS. Even their entry level decks are 2.3 volts RMS.

For all the car audio wizards out there, you should check the input voltage range of your amp before you add a 'line driver' . Most amps on the market can produce their full power as long as the input voltage of the low level signal is 2-3 volts RMS. Putting 8 or 10 volts into your amp will just clip the input section.

It is much more importans supplying the current that the amplifier needs. Most large amps are never producing their full potential in peoples cars. Their charging system cannot supply enough current. 1500 watts divided by 14.4 volts equals 104 amps.

Most cars do not have this large of alternator. Even if they do, you have to allow for the electrical systems in the car, your headlights & air conditioning.

The spec to look at is the head units output impedence. It relates directly to the sound quality of the deck and to the decks performance when used with multiple amps.

EnvisionAudio, please do not speak unless you are sure about what you are talking about. You are correct in stating that Delco used to build Rockfords decks in the late 90s. You are 100% wrong in stating that they had anything to do with Rockford amps.

I hear everyone praising Eclipse decks. Suprise, Eclipse does not build their own decks. Who does? Hyundai builds Eclipse decks and they also build Rockford decks.

Rockford amps had the loudest score at this years DB Drag world finals, oh yeah, they also won the death match. This is with a consumer BD15001. It was actually Pioneer that was using the Rockford Amps.

There is a lot of world class car audio products out there, Rockford is for sure one of them. The installer and the way he installs the electronics and builds the subwoofer enclosure is at least as important as the electronics used. When an amplifier burns up it is most often an install related problem. Enough said.

KevinLee




🙂 🙂
 
Once you're around 90dB SNR, the extra dBs are negligable.

The extra voltage on the preamp outs only reduces the noise floor. If you have 2V, that's more or less going to be comparable to 4 or 5V. There really is no difference between 4 and 5V.
 
Hmmm. I was hoping this board was going to be more "high class" then for people to get on here and start bashing other people. Maybe I am taking the tone wrong.

Just to let you know I have been in the car audio industry for about 16 years now and was one of the youngest people to ever get there MECP Master install title back in the day. I have worked with just about every brand out there but no one pays me to say I like one or the other. I just state the things I have delt with in the pasts. I know companies and products change over time, just look at poor PPI. They used to be one of the best amps out there, now you could not give one to me to use in my car.

As fpr your bondness about the Rockford decks all being 2.3 volts RMS, I think you need to go check out there website and see what they are saying there outputs are on there decks. No offence but I am going to go by what they are saying about there units over you. There high end deck go upto 8V, only the lower models are 2.3V. PLease, lets make sure we all have the "facts" straight here.

As for the voltage/impedence of teh outputs, yes it can help in some situations. I was not trying to say it does not do anything. Guess I should have worded it different. But if you have a system now that does not have noise then it is not to much of an issue. There might be very very small diference in sound from one setup to another but there again this is car audio and there are way to many variables.

For the stament about power bemands that is correct for bepending on the besign of the amp to can be better then others. If your amp has a non-regulated power supply then its output is a direct equations of its input voltage. The the input V is high then the amp will put out all it can, but if it is low the out goes way down. This is not as bad with regulated PS amps. There output is not as input V sensitive. Ex: a Mcintosh amp can put out its rated power with in input V less the 10V. Yes you are right about big amos drawing a lot of current but when playing most music that is only for a % of a second at a time. Just to let you know I know what you are talking about I will tell you that in my mian car i have a 260amp atl. with the V set to 14.4, two yellow top Optima batts and 6F cap and running throught )guage wire.

As for you jumping on someone for saying something, well I was the one the said that Rockford deck used to be made my Declo.

Eclipse might be assemble the final unit but they do in fact make there own custom clips for some of there unit and they do make the transports at least in the higher end units. I am not saying Eclispe is the end all in deck, I was just giving advise on what I like to use and what has worked for me. I like to look at all the specs and the like but for me what really counts is what my ear tells me. It has told me for years the my old Eclispe DDL setup sounds better then just about anything I have heard, exept for the Alpine F1.

I dont think we were talking about how did or did not win any SPL contest here. I have biuld a few actually servo motor subs (yes no voice coil assembly, just a motor looking thing) that were 15" and hit 150DB+ on 20 watts but they would not stand up to daily use and sounded like azz for the most part.

You might like Rockford but not Eclispe. I like Eclispe and not Rockford. I am not about to go off blasting someone for what they like or dont like. If it works for you then cool. If you want to let someone else know you like Rockford then do so without blasting. I have seen some very strange and odd setup sound great and have also seen some very very high end stuff sound down right awful.
 
Let's get it straight...

For all the car audio wizards out there, you should check the input voltage range of your amp before you add a 'line driver' . Most amps on the market can produce their full power as long as the input voltage of the low level signal is 2-3 volts RMS. Putting 8 or 10 volts into your amp will just clip the input section.

Most car amplifiers on the market will produce full output power with less than 200mV input at max gain.

EnvisionAudio, please do not speak unless you are sure about what you are talking about. You are correct in stating that Delco used to build Rockfords decks in the late 90s. You are 100% wrong in stating that they had anything to do with Rockford amps.

Yeah, I wouldn't know what I'm talking about...🙄 Delco didn't build Rockford's amps, but they built the SMD ceramic daughterboards that soldered into the main boards in the Punch 45/75/150 and that's it. SMD manufacturing was fairly expensive then, but it was more profitable for Rockford to modularize their input and MosFet driver sections into these lightweight and very reliable modules. Rockford still DESIGNED them, but they didn't manufacture them.

I know this board is more classy, and I believe it should stay that way. There are some of us in the industry that are in the know - beyond the installation bays and into the minds of the engineers that bring the equipment to market.
 
So back to the deck

So the RF HU came in the mail today. Its sexy. copper plated case, sweet display, and ah.. the smell of new electronics.

To refresh some of you: I bought this RFX-9210 HU to temporarily replace a Pioneer unit that is being repaired. The numbers that are pertinent to this conversation go like this:

1998 Pioneer Premier DEX-P78
CD S/N =`120dB
FM sens = 12dB
signal out V = 4v

2003 Fosgate RFX-9210
CD S/N = 90dB
FM sens = 9dB
signal out = 5v

So we've determined that the difference between 4v and 5v preouts is completely a wash in this case. The Fosgate I got for a song. I got it for 60% off of Crutchfield's clearance price, and its new, not refurbed or scratch and dent, just a super closeout.

I have a few options with this deck: Sell in on Ebay and try to make a few bucks, return it to Crutchfield for a refund, put it in the SS and keep the refreshed Pioneer as a backup, or install it in my BMW and put up with the fact that it has a multi-color face. :whazzat: I don't think blue numbers and red buttons would quite cut it in an all orange dash. The Bimmer currently has an older Pioneer unit that is all orange and it looks like its supposed to be there. Even its numbers are better than this RF HU. My wife has her brand new JVC with the Dolphin display. I don't even think she cares if there are speakers.🙄

Whaddaya think? Anyone want an RF HU? Should I hang on to it? Its just too pretty to send back.
 
Turboegt said:

As fpr your bondness about the Rockford decks all being 2.3 volts RMS, I think you need to go check out there website and see what they are saying there outputs are on there decks. No offence but I am going to go by what they are saying about there units over you. There high end deck go upto 8V, only the lower models are 2.3V. PLease, lets make sure we all have the "facts" straight here.

For being in the audio industry for so long, I would think you were aware ratings are generally inflated. Just look at internal amps and their ratings. Even the RMS power on those ratings means nothing since THD specs are usually never given (yea, I can take the RMS of my amp while its driving a sine wave at 10% THD... that'll look REAL nice).

Also noteworthy: RF bought a ton of Denon Z1 decks, adjusted the AM/FM and put their stamp on it. They're sitting in a factory right now as backed up by Rob Hephner and an RF dealer I know. There's one on ebay going for $650... MUCH cheaper than the Denon deck originally goes for.
 
I did it

Well, I did it. I bloody jumped in and did it. I was putting some Polk EX 3550 separates in my little BMW today (which, by the way sound absolutely killer) and was just going to stick with the original HU. I debated putting the RF HU in, but thought better of it until I realized that I had mixed up my colors. I was thinking that green was right front. So, I figured if I was going to cut into the harness anyway, might as well put a new one in.

I'm glad I did. I don't like the blue numbers, but I think the old one was just tired. The old one (although rated higher wattage) didn't want to push the speakers much.

So, anyone want a tired Pioneer from 1999?
 
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