Setting Proper Gain

[shaudioV6]

Hi there guys! First post but been an admirer of the forum for many years now.

Before i ask my question i would like to ask if anyone has any recommendations on CHEAP oscopes. I know most of you in this forum use the DD-1, but at $150 i'm in no rush to buy one for myself (nothing against steve or dd-1 and i completely understand that production costs, especially for a unique and really desired product like the dd-1 are not cheap.) I know "good" oscopes go for around the same if not more, but i'm not looking for anything fancy. Simple cheap oscope is all i need.

HU- Pioneer deh x3500ui (a few years old. pretty low end. could be had for ~100 and the new versions are just as cheap. definitely no 99prs LOL)

AMP- Pioneer d9601 with harrison labs fmods (high pass 30hz bc no SSF). i know what a lot of people will say about this amp but for $180 and 1200 watts, it isnt a bad amp. they're actually 120 shipped now.

SUB/BOX- RE SXX 1200 watts. in a 1.8 cube at 36hz. 8 awg ofc speaker wire (i know its overkill but it was a better deal than the 10 awg)

POWER- 0 awg ofc with a mechman HO alt, so no worries on the voltage drop

My question regarding amp gains is about matching them with the HU voltage. I normally use a DMM with a 60 hz test tone to set my gains. I use the Ohm's Law formula and set my gain to the AC voltage thats right for the setup. I know this is only a theoretical way to set the gains and other variables are going to ultimately determine whether or not my amp clips. I currently own a low end pioneer head unit and when i tested it's rca voltage going to my amp, i was getting .9 volts with a 60 hz test tone at fairly high volume. Again this is a low end pioneer HU not a 99prs, so out of 62 volume i do not exceed 46-50. (again, no dd-1 or oscope so i cant tell you for sure at what volume my HU clips, but i honestly feel that it will start to clip right around 48). I would assume that my HU is going to give me the rated 2v at somewhere around max volume, at which i can guarantee it will clip. When im not playing any decaf, dj inclined or other similar music, my music (even some rap) doesnt really allow my amp/sub to get 1200 watts or its max AC voltage taken from Ohm's Law. i try to avoid using loudness or my HU eq. I occasionally my subwoofer adjustment and will give it like 3/6. Im not exactly sure if this is +3db bass boost or what it really is, but i TRY to avoid it. anyway, i cant really get very much output from my sub/amp without turning the volume up past 50, using the loudness, eq, and other functions, or turning the gain up on my amp to around 5/6 of the way (which looks like around 1V pre-amp on the amp itself). These are the only ways that i can match my AC voltage to the one i calculated and get actually decent output. I am just concerned about clipping and without either a dd-1 or oscope i'm kinda stuck on speculation. Normally i would just eyeball it and use that ACV number with a test tone, but this is my personal setup and i spend a pretty good chunk of money on it, so i just want it to last me a while. Since im actually getting around 1V from my HU at a volume that i assume should not clip, i was wondering if it were okay for me to set the gain on my amp to 1V. I would not even be asking the question because it sounds so obvious, obviously if you're getting 1V output from HU then set the gain on the amp to 1V. It sounds like common sense. But my issue is that 1V on the amp is very close to the max setting on the gain, and i only really get 1V from the test tone. When my normal music is playing at proper volumes, im getting as little as .5V AC. Im testing this by putting the pos test lead from my dmm to the pin of the rca while putting the neg lead to the outer metal shell of the rca. Its truly amazing how low my voltage from the HU is proving to be. Any feedback would be greatly appreciated. I know this is long as hell so sorry in advance for anyone who reads this. Also, thanks in advance for anyone who is actually taking time out to read this and trying to provide me with any feedback. Constructive criticism is ALWAYS welcome!! thanks guys!

Also, im pretty sure this is a stupid question, but has anyone ever noticed their HU's amp starting to go out? again, this might be a dumb question but im wondering if an old and very very used HU's ability to process and assign power can start to deteriorate. i know they have mosfet power supplies so it might be a dumb question but screw it i just asked haha.

I honestly really do appreciate anyone who is reading this and is providing me with feedback. thanks!

[ShadeTreeMechanic]

Welcome to SMD! Wow what a long post. Normally when I have a source that has a low output I will run a pre amp EQ to boost the signal. This allows the amps to be run with the gains set low. If you are not measuring distortion (which is different than clipping) when you set it up then basically you are tuning by ear and what ever you set the head unit to doesn't matter. Just don't expect to play full volume safely.

[shaudioV6]

ShadeTreeMechanic, I really appreciate your response. Just one question though. When adding an eq, wouldn't boosting the lower frequencies give your amp more of a chance to clip? (assuming you have no tools available to measure distortion and clipping). Wouldn't that essentially be like using bass boost on either your HU or amp since you're basically boosting the low frequency signal going to the amp/sub?

Once again thanks for reading and responding.

[ShadeTreeMechanic]

Using an EQ to boost a given frequency will reduce the headroom available at that frequency. An EQ with a built in pre amp can raise the whole output signal sometimes as high as 9 volts depending on which unit is used. This way the undistorted signal from the head unit will be stronger. Bass bost, EQ, loudness can cause the signal to be clipped at the boosted frequency while the rest of the spectrum is not because the boosted frequencies will max out first. None of this matters without measuring distortion because there is no way to be sure of what you have. All you can do is "play it by ear". There is a ton of information on this site. Just use the search function. I have learned alot in my short time here. Hope this helps.

[Efreakingt]

As far as an O scope goes, the cheapest out are the DSO nano at $50-100. They are kinda a pain to use. I just bit the bullet and got a DD1, it's super easy to use and worth it to protect my equipment.

[RooTxBeeR]

I bought my dd1 used for 105 shipped to my door. Was so damn worth it because if I want to re tune or do any type of anything. That piece of equipment will ALWAYS be there to help me. Then to top it off, It is made in the name of the greatest customer support rep, named Steve Meade. Unless you take video of you hammering it to death with a shovel and say steve, it stopped working. That would probably be the only time he wouldn't help someone get it replaced or fixed.