# Some things to remember "in the moment"



## chad (Jun 30, 2005)

It has been reported here several times of discouragement of losing speaker components and amplifiers during testing and tuning. It’s important to realize a few things. This may be remedial to many, but certainly worth remembering in the “heat of the moment”

Test tones have a 100% duty cycle, this is VERY stressful on amplifiers and drivers, and this is the way to get things the hottest the quickest! If you are not careful with tones you can kiss a tweeter goodbye right quick! The small voice coil simply cannot shag heat quick enough, and there is no break for it to do so! We listen to music not tones.

Setting your amplifiers clipping point with test tones robs you of power down the road. Since we are dealing with such a high duty cycle the power supply of the amplifier AND CAR is under stress, the most stress it will be under. If you set the clip point of your headunit to the clip point for the amplifier with tones you lose one important thing. Amplifiers clip MUCH later with music or bursts, the power supply is not sagging with music (much lower duty cycle) and the amplifier can make more power. This is not so as much with head units and processing. The maximum voltage is the max voltage. They are not driving a low impedance load as an amplifier is. You can usually eek a lot more gain out of an amplifier AFTER you set it to clip with a tone. We listen to music not tones.

Pink noise has a 50% duty cycle, if you can stand it.

There is nothing wrong with FLICKERING the clip light into a low frequency driver; it will take it in stride, no problem. HF drivers SOMETIMES will but it is not recommended. If you are flickering a clip light into a tweet you are GROSSLY underpowered.

A clip is a clip, no matter where it is at in the signal chain. If you clip your crossover the amplifier will amplify the clipped signal, a good amplifier will amplify ANYTHING, even DC on direct coupled amplifiers if no DC protection is present. Sometimes preamp level clipping is nastier than amplifier clipping due to overshoot on the op-amps and can/will have more HF content from clipping. If you clip a head unit and send it to the active crossovers they will separate this HF harmonic information, the amp will amplify it, and it will be passed to the tweeters. Modern gear has a staggering frequency response; this is good, and sometimes bad. I like my amps to clip FIRST, screw that “clip all at the same time stuff.”

The professional amplifier industry has taken a mind boggling approach to amplifier ratings and the FTC has agreed. Back in the day when you bought a Crest 8001, Crown 3600VZ, or larger type amp it came shipped with NO power plug on it, just a pigtail. Because if they shipped it with a standard 20A plug it would not adhere to safety ratings. These amplifiers can pull WAY more than 20A during sine testing and will play a sine wave at full output ALL DAY LONG and merely keep your coffee warm. No scoffs, no scuffles, this is how I tested them. In a music application it would be no problem to run them on a 20A outlet and flicker the clip light.

Today we are seeing MONDO power output figures and amplifiers equipped with 20A plugs. The FTC has given amplifier makers the go ahead to rate their amplifiers with real world figures under real world applications. Do the new amps make more music power than the old amps and weigh a mere 25 Lbs as opposed to 80Lbs? Yep! Will they do this at a sine wave? NO WAY IN HELL, in fact some see a true sine as oscillation at high levels and will go into protect! We may be seeing car amps doing the same thing as the market turns to more PWM designs as the pro audio industry has. There’s no reason to amplify a sine wave (we listen to music)

The early pro audio amplifiers are hand-me-downs (for the most part) from industrial designs used to power shaker tables, MRI machines (in fact Crown still has a division that makes gradient amplifiers, one is strikingly similar to the MA10000) and if Minivanman finds one surplus he WILL PM me ASAP! These amplifiers were the most powerful out there at the time (at a scorching 150W/Ch) but would drive a dead short. Recently we have gone to PWM and realized that 100% duty cycle was not needed, just bullet proof for the intended application, whereas the standard used to be bulletproof for ANY application! Enter the new FTC figures. Keep your eyes open folks for this to come around to us. 

I still have mixed emotions about it because I’m psycho and find nothing more beautiful than a Crest 9001 at full output sine wave heating water in a water heater at full bore with the clip lights lit up ALL DAY LONG! It’s a thing of beauty. OTOH, I’m getting older and if I can tote around an amplifier rack that weighs 1/4 as much, uses less gas to haul, less manpower to do it, and makes more power to my drivers in the intended applications…..how can I *****?

Now I went on that rant to touch on wire sizing. You can calculate wire sizing all day long and come up with insanely large figures, but remember one thing…… The duty cycle of music is low, we listen to music not tones. Know that your AVERAGE current draw is next to nil in a listening system, note that you are putting in figures into wire size calculators that represent what the system will be pulling full bore. Into low impedance loads. Many wire size charts are set up to recommend sizing based on high duty cycles, such as in heating and motor applications…. Just remember that and think wisely when totaling up your fuse sizes on your amplifiers and knowing you will be running 8 ohm drivers, mids and tweets, etc. Yall are smart folks, use common sense before you buy mondo wire and look at your actual current draw.

And here’s a bit of the FTC amp ratings if you are interested, it’s a neet read. I have some easier to read articles too.I need to find them. 

http://www.soundandcommunications.com/audio/2006_06_audio.htm

Chad


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## ErinH (Feb 14, 2007)

chad said:


> Setting your amplifiers clipping point with test tones robs you of power down the road. Since we are dealing with such a high duty cycle the power supply of the amplifier AND CAR is under stress, the most stress it will be under. If you set the clip point of your headunit to the clip point for the amplifier with tones you lose one important thing. Amplifiers clip MUCH later with music or bursts, the power supply is not sagging with music (much lower duty cycle) and the amplifier can make more power. This is not so as much with head units and processing. The maximum voltage is the max voltage. They are not driving a low impedance load as an amplifier is. You can usually eek a lot more gain out of an amplifier AFTER you set it to clip with a tone. We listen to music not tones.
> 
> Pink noise has a 50% duty cycle, if you can stand it.



So, you're saying that by setting your gains with a DMM while listening to test tones, you're not giving your speakers as much power as they could get? Basically we're "under-powering" our speakers using this method? If so, that's fine with me because I'm less likely to have clipping by playing music at the selected volume the gains were set at. However, what would you use to set the gains? I assume it would be "pink noise" since you followed the gain paragraph with that sentence. Thing is, I have no idea what pink noise is...

Search button is my friend.


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## chad (Jun 30, 2005)

Knowing your speaker sensitivity and setting your REALTIVE gain with a DMM is not a bad thing AS LONG AS your dmm has the frequency response to deal with it. If you DMM can measure frequency it probably has a pretty broad frequency response. 

To set a clip point.... 

You can't with a DMM because it will not show you where the amp clips, the amp will be well into clipping and increasing the input will make the voltage go up on the DMM. DMM's measure RMS AC voltage not P-P, P-P can stay the same RMS can go up in clipping situations.

You need a storage scope and a burst to properly look for a clipping point in a music situation.

Your ears are wonderful peices of test gear.

Chad


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## MarkZ (Dec 5, 2005)

bikinpunk said:


> However, what would you use to set the gains?


Ears!

The main problem with using a DMM to set gains is that you're assuming that all recorded musical content peaks at 0dB. I've got some albums that never get that high, and some bootleg live/demo tapes that have transients that are lucky to get to -10dB. So when you set things up so that your volume knob is all the way up at the point where a 0dB recording will clip, then your -3dB songs will only get to max power minus 3dB (or half the output capabilities of the amp!). This is why amplifiers without gain adjustments (eg. your home theatre receiver) tend to clip most content when the volume knob is at around halfway or less. It gives you plenty of room for quiet recordings and low voltage sources.

So what you need to do is set your gain so that the amplifier clips when the volume knob is halfway or 2/3 up or something along those lines. Make the gain too low and you'll never be able to get max power for quiet recordings. Make the gain too high and you lose volume resolution -- in other words, your lowest volume setting will be too loud. Since the actual setting is rather arbitrary, there's absolutely no need to use measurement equipment to set your gains.

PS - A little clipping never hurt anyone. Especially for you guys running all active. It really takes an astounding amount of clipping before you begin to notice -- long duration signals overdriven at an appreciable level. Some of you may be well acquainted with my motto by now: If your speakers can't handle it, then it's time for new speakers!


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## chad (Jun 30, 2005)

MarkZ said:


> Ears!
> 
> .....
> 
> PS - A little clipping never hurt anyone. Especially for you guys running all active. It really takes an astounding amount of clipping before you begin to notice -- long duration signals overdriven at an appreciable level. Some of you may be well acquainted with my motto by now: If your speakers can't handle it, then it's time for new speakers!



And BTW Mark and I are in no way realted  

Chad


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## ErinH (Feb 14, 2007)

MarkZ said:


> Ears!
> 
> The main problem with using a DMM to set gains is that you're assuming that all recorded musical content peaks at 0dB. I've got some albums that never get that high, and some bootleg live/demo tapes that have transients that are lucky to get to -10dB. So when you set things up so that your volume knob is all the way up at the point where a 0dB recording will clip, then your -3dB songs will only get to max power minus 3dB (or half the output capabilities of the amp!). This is why amplifiers without gain adjustments (eg. your home theatre receiver) tend to clip most content when the volume knob is at around halfway or less. It gives you plenty of room for quiet recordings and low voltage sources.
> 
> ...


Wow, now I'm more lost...what do you use to set the gain with? I mean, audio-wise? Do you use a pink noise track? Do you use music, etc? Because like you said, music is different. However, I did set all my mp3s to the same decibel level via a volume matching program.

I was just fine with the DMM method...dangit, now I'm ruined!


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## T3mpest (Dec 25, 2005)

If you'd like to use tones to set gains, just don't use 0db ones. -3 or -6 will give you a bit more realistic gains setting. As was already mentioned, using 3/4 hu volume gives you headroom for low volume recording, as well as keeping your preouts from clipping.


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## MarkZ (Dec 5, 2005)

bikinpunk said:


> Wow, now I'm more lost...what do you use to set the gain with? I mean, audio-wise? Do you use a pink noise track? Do you use music, etc? Because like you said, music is different. However, I did set all my mp3s to the same decibel level via a volume matching program.
> 
> I was just fine with the DMM method...dangit, now I'm ruined!


I just use various CDs that I'm familiar with. Most are recorded hot, some are much quieter. Personally, I use two tracks in particular for the quiet ones just because I'm familiar with them and they're recorded rather low -- "Double Dip" by Hum (rock) and "Nuages" by Claude Debussey (classical). Both are very dynamic with high crest factors (~12-15dB) and I find that useful to gauge volume.

Anyway, there's nothing special about gain adjustments. It's just a volume knob. The whole point of adjusting it is so that your volume knob on your head unit spans the range you need it to. Don't pay much attention to voltage settings and the like. I know people desperately try to line up the "4v" mark on their amplifier because their head unit says it has 4v outputs, but it's a waste of time.


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## ErinH (Feb 14, 2007)

T3mpest said:


> If you'd like to use tones to set gains, just don't use 0db ones. -3 or -6 will give you a bit more realistic gains setting. As was already mentioned, using 3/4 hu volume gives you headroom for low volume recording, as well as keeping your preouts from clipping.


This is a major step off the other tutorials I've read where 0db is the preferred method and anything below was "bad". I'm not disagreeing with you, though. 




MarkZ said:


> Anyway, there's nothing special about gain adjustments. It's just a volume knob. The whole point of adjusting it is so that your volume knob on your head unit spans the range you need it to. Don't pay much attention to voltage settings and the like. I know people desperately try to line up the "4v" mark on their amplifier because their head unit says it has 4v outputs, but it's a waste of time.


I just put the importance on not overdriving your amp. I actually set my gain a tad under what the calculated was. Oh, well. I'll consider your advice. I can't think of any tracks that I can use to tune with right now. Plus, it's hard to change the gain and listen at the same time...might get the woman to help, lol. Setting the gain for my subwoofer would be pure hell like this though...the subwoofer is on top of my false floor, where my amps are under.  

Thanks for the info.


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## chad (Jun 30, 2005)

T3mpest said:


> If you'd like to use tones to set gains, just don't use 0db ones. -3 or -6 will give you a bit more realistic gains setting. As was already mentioned, using 3/4 hu volume gives you headroom for low volume recording, as well as keeping your preouts from clipping.


No matter what level the tone is recorded at it's still a 100% duty cycle.

Chad


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## evan (Dec 2, 2006)

What does clipping sound like?


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## chad (Jun 30, 2005)

Honestly..... Not like much unless it's severe 

The high end will get spitty and you may hear harmonics.

Chad


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## npdang (Jul 29, 2005)

evan said:


> What does clipping sound like?


It depends on a great variety of things... for very brief periods of time at low frequencies I doubt you could hear it. It's more debatable in the midrange and treble frequencies. Of course, consistent heavy clipping is definitely audible and sounds as if your recording turned to noise/static.


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## MarkZ (Dec 5, 2005)

evan said:


> What does clipping sound like?


You could download some tone generator software (try TrueRTA?) and compare a square wave to a sine wave for a rough approximation. You could also try going into Winamp's EQ window and turn the preamp level all the way up and you can get something resembling what you'd hear clipping real world music. In practice things are a bit different, but it may give you some idea.


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## T3mpest (Dec 25, 2005)

bikinpunk said:


> This is a major step off the other tutorials I've read where 0db is the preferred method and anything below was "bad". I'm not disagreeing with you, though.
> 
> 
> 
> ...


That's because anything less than a 0db track can cause clipping on actual music. Setting by ear will also allow for light clipping, but will also give you more power on the normal parts of your music. Honestly I've always just set my gains by ear, except for subs. I use songs that I know are "loud", set the hu to 3/4 volume. Then I turn my gains up until it's loud enough, or I hear stress. Once I hear stress I back it off until the stressing sounds are gone, then a tad more for good measure. Subs that usually doesn't work though.


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## chad (Jun 30, 2005)

Yeah me too, I use ears on the subs too, the sub is least efficient in most situations so once that's dialed in it's just a balancing act IMHO. When the sub gets "blatty" I back off.

Chad


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## FoxPro5 (Feb 14, 2006)

MarkZ said:


> I know people desperately try to line up the "4v" mark on their amplifier because their head unit says it has 4v outputs, but it's a waste of time.


That's a very good point. Those voltage ratings are very missleading, as we all know.

I've always viewed the gain knob as sort of evil. I don't now, maybe it's just me?? Something I've always felt would be useful would be to buy high power amps with matching high input sensitivities. For example, running 2x the rated power on all drivers with the gain at absolute minimum. This way you can make finite adjustments on the HU with level matching and let the power do the work. You get all the dynamics in the music from the power and no clipping as a result of guessing wrong on the gain setting. 

Someone correct my logic if it's incorrect here, please! 

If the gain on the amp really is just a volume knob, then it would make no difference if you cranked the HU volume or cranked the gain. Right???


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## jearhart (Jul 28, 2006)

B-Squad said:


> If the gain on the amp really is just a volume knob, then it would make no difference if you cranked the HU volume or cranked the gain. Right???


no, the input signal can be clipped before it reaches the amp. and having the gain cranked and the volume at a minimum would make the volume knob usless and would have bad noise issues.


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## chad (Jun 30, 2005)

The gain contril is a sensitivity adjustment, even with it turned to it's least sensitive position the amplifier can make full output with enough input.

Dunno if that helps?

Chad


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## MarkZ (Dec 5, 2005)

B-Squad said:


> That's a very good point. Those voltage ratings are very missleading, as we all know.
> 
> I've always viewed the gain knob as sort of evil. I don't now, maybe it's just me?? Something I've always felt would be useful would be to buy high power amps with matching high input sensitivities. For example, running 2x the rated power on all drivers with the gain at absolute minimum. This way you can make finite adjustments on the HU with level matching and let the power do the work. You get all the dynamics in the music from the power and no clipping as a result of guessing wrong on the gain setting.
> 
> Someone correct my logic if it's incorrect here, please!


A gain setting is always there, regardless of whether or not the amp has a knob. "Gain", by definition, is basically the amount the input voltage is amplified by. So if you feed the amplifier a 1v sine wave, and the amplifier is going to drive the speaker with a 50v sine wave -- then the gain = 50 (no units). Raising the gain setting gives you more of a voltage gain. But if the amp is only able to output 70v, then raising the gain any higher than 70 is going to cause your 1v input signal to be clipped at 70v on the output of the amp.

So you've always got a gain. It's just that sometimes the manufacturer puts a knob there so that you can adjust it to whatever you want. If you don't want to adjust it (like with amps that don't have a gain adjustment), then don't turn the knob. 




> If the gain on the amp really is just a volume knob, then it would make no difference if you cranked the HU volume or cranked the gain. Right???


That's pretty much right. There are sometimes exceptions at the extremes though. For instances, some head units clip at their max volume setting, so you usually want to avoid setting your amplifier gain in a manner that would cause you to have to crank the head unit all the way up.


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## FoxPro5 (Feb 14, 2006)

MarkZ said:


> A gain setting is always there, regardless of whether or not the amp has a knob. "Gain", by definition, is basically the amount the input voltage is amplified by. So if you feed the amplifier a 1v sine wave, and the amplifier is going to drive the speaker with a 50v sine wave -- then the gain = 50 (no units). Raising the gain setting gives you more of a voltage gain. But if the amp is only able to output 70v, then raising the gain any higher than 70 is going to cause your 1v input signal to be clipped at 70v on the output of the amp.


Right, I understand the purpose of the amp. I guess I'm arguing that it would be better to buy an amp that does a minimum of 100v of gain rather than buying one that does 70v, but you have to crank the gain up 30v to get the 100v (musical loudness) you desire. 

It probably makes no sense [damn voices inside my head]. :blush:


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## FoxPro5 (Feb 14, 2006)

chad said:


> The gain contril is a sensitivity adjustment, even with it turned to it's least sensitive position the amplifier can make full output with enough input.
> 
> Dunno if that helps?
> 
> Chad


I understand that, thanks.  

What I don't understand fully is how to go about buying the right amount of power so that no clipping is involved and you don't have to worry about those moments. 

Do you recommend capping your tweeters then Chad?


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## chad (Jun 30, 2005)

B-Squad said:


> Do you recommend capping your tweeters then Chad?


I cap my pro HF devices but not in the car. Dunno why, just never had an issue.

Chad


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## Preacher (May 8, 2006)

Square wave =


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## chad (Jun 30, 2005)

Preacher said:


> Square wave =


Naaahhhh, That's just a "modified sine wave" 

Actually

You'd be suprised what that looks like, I'll try to find a waveform, or I'll have to take a pic of the scope. It starts as a sine when clean and as you increase the distortion there is 2 bumps per peak or valley, then it gets progressively more ragged from there. It also makes "crossover distortion" whereas at the zero crossing point the waveform doglegs at first then there is a zig-zag notch at the cross point. This "dog leg" at the cross point is one of the things that gives a well driven tube power stage in a guitar amp "that sound."

A square wave type distortion would not work well with guitar, just not "enough" distortion.

Chad


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## Preacher (May 8, 2006)

I'd love to see wave forms of different distortion if you have time. We'll start a new thread in OT. Sorry about the picture size.

Is the proco rat more like a plain square wave?


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## fej (Feb 8, 2006)

Cool thread thanks Chad/Mark.

I have always set systems by ear as well, and generally with the subs off, midrange/bass, mid, tweet and then I add the subs and try and blend, the more advanced the system the more time I spend playing with crossover points in the midrange/tweet area. I tend to buy higher power amps as I like headroom, or the ability to turn it up loud and not have the amp clip. Most people misuse the gain on the amp as they mistakenly think that you will not get all 400w if the gain is at minimum on the amp, so they crank the gain and then have huge bass and no chance of the front stage catching up with their HU at 40% of max. Right now my system is at minimum on the tweets and mids, 5% on the midbass and sub at 65/80 on an 8053. (clips at 78/80 from my measurement)

Anyways, thanks for the thread, it is always nice to hear that people that know their stuff recommend doing things the way you have always done them  Makes me feel like less of a n00b  

Moral of the thread, use your input control to maximize the signal that your amp has to amplify in the first place, they won't have to work as hard to get to the volume that you are looking for, and are far less likely to send a clipped, or badly clipped, signal. (at least IMHO)


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## less (Nov 30, 2006)

Just out of curiousity, anyone here familiar with the system McIntosh uses to monitor its car amplifier clipping? The material released indicates that the amplifier automatically sense whenever the amplifier is clipping or going to clip and reduces the output to prevent it. 

Frankly, this is one of the things that really intrigued me when I was shopping and ultimately was a small factor in my purchase of an old Mc (MC440M) amp for my system. I used to be a major ADS fan, and their original tweeters didn't handle clipping at all... I listened to music loud a lot back then and probably toasted 10 ADS tweeters in my day. I sure didn't want to do this with my new speakers (and at the time, I was using ADS speakers in the system).

Is this a marketing point only, or does the system really work as advertised? I have only been able to get the thing to clip once or twice (according to the light) and then only at ridiculously high levels of output. 

Anyhow, it does seem to work, and it is nice not constantly worrying when you crank it up that you are going to be buying new tweeters next week! I must say, purchasing an older McIntosh amp was one decision that I won't regret! That old bugger is built tough - it sounds simply magnificent - its highly under rated powerwise with a ton of headroom - and I doubt I could kill it if I wanted to. I can't imagine a better amp - or a better value if purchased used.

Less


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## chad (Jun 30, 2005)

Most of the time it's a comparitor circuit that looks at the input and the output and ignores gain. When it senses controversy it applies limiting. I used to know a one chip wonder's part number but I forgot it. I have a repair to do on an amp with this circuit in it, I'll write it down.

Chad


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## ErinH (Feb 14, 2007)

I'd like to add something to this list:

Do your tuning with the car running. Or at least do it in intervals if you don't want to start your car (and who can blame you, with the gas prices being so high). That way you won't get a dead battery and wonder why your cd player no longer powers up. 

^^ Happened to me today.


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## chad (Jun 30, 2005)

bikinpunk said:


> I'd like to add something to this list:
> 
> Do your tuning with the car running. Or at least do it in intervals if you don't want to start your car (and who can blame you, with the gas prices being so high). That way you won't get a dead battery and wonder why your cd player no longer powers up.
> 
> ^^ Happened to me today.


I have a HORRIBLE battery in my Civic, as I imagine you do too if you are stock. I run my car on an external power supply while tuning....

Having a high preamp voltyage will not harm the preamps or hinder their life. if you have even a bottom feeder op-amp at bipolar 15V it will safely produce WAY more than 6.5V RMS for a time period of longer than I have lived 

Chad


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## solacedagony (May 18, 2006)

bikinpunk said:


> I'd like to add something to this list:
> 
> Do your tuning with the car running. Or at least do it in intervals if you don't want to start your car (and who can blame you, with the gas prices being so high). That way you won't get a dead battery and wonder why your cd player no longer powers up.
> 
> ^^ Happened to me today.


Not only that, but tuning with your car off attempts to negate the fact that their will (unless you have deadened ridiculously) be a ton of road/engine/air vent/etc noise to deal with. So tuning with your car off isn't actually how it's going to sound while you're driving. I like to tune in my driveway with the car on, then take a drive around the block to see if it sounds alright. I usually end up turning up the sub and mid bass a bit because I loose it while driving.


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## MarkZ (Dec 5, 2005)

solacedagony said:


> Not only that, but tuning with your car off attempts to negate the fact that their will (unless you have deadened ridiculously) be a ton of road/engine/air vent/etc noise to deal with. So tuning with your car off isn't actually how it's going to sound while you're driving. I like to tune in my driveway with the car on, then take a drive around the block to see if it sounds alright. I usually end up turning up the sub and mid bass a bit because I loose it while driving.


Tuning with the car on will give you a ton of noise in your measurement. Especially low frequencies. This is fine if you're tuning by ear, but not if you're using an RTA because it'll show up in the spectrum.


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## dawgdan (Aug 10, 2006)

Dumb question.. is there such thing as a clipping indicator (aside from an o-scope) that one can purchase? Maybe just like a light or something?

I've been setting gains by ear for awhile now, with success, I might add.. but I can't help but wonder if I'm not using my amp to maximum potential.


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