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I am washed out today. I just laid down thinking how much of a bummer it is that I am having a problem. It always something it seems. There's lots of amplifiers on Craiglist, but then I was thinking... thinking of all the things I had wished I had done and done differently over the years. The above picture is one my Denon Two Channel Amps. They were the best they offered for Home Theater 1995 or so. Just simple cabinets, power supply distribution and control running down the center, a transformer for each block on the left and the right. Each block on the left and the right is considered one channel. A block measuring 4" x 6" x 8". I have seven of these "blocks". I was thinking it's too bad I couldn't pick up some older home theatre units and strip them of these components. They'd probably be easier to assemble and mount where you want to fit them for maximum use of space and intelligence of design. I have an idea after seeing Joe and his under seat slide out tray. That's how I would like my amps and connections. Just slide it out from under the seat in rails and wham...
The voltages are wrong for these though. Pretty slim odds that they are designed to run on 14 volts. My project is going to stall out temporarily as I will either have to reconfigure my amps to accommodate two half dead channels, fix the amp or buy another. It might be a little before the wind blows one way or another. This was only to be a day project (installing the amps and speakers) and it's gone on and on and on... it's always one thing not going right. It's the journey, not the destination.
Oh... and no, the DSP does not have built in test tones but it came with an audio CD with a few common ones. Simply pop the CD in the Head Unit. For anything else there is our friend the internet.. all kinds available.
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Maybe I could run a high quality inverter... have my auxiliary batteries solely for that purpose solving all my needs at once? Then run 120 volts for my audio? I guess that would be kind of crazy eh? I am just thinking out loud without a good nights sleep behind me. It would be pointless still needing those transformers / toroid coils. House equipment is much cheaper and more abundant used that's all. Especially 20 year old technology. Probably a really bad idea.
Last edited by dberladyn; November 30th, 2018 at 1:46 AM.
The output of today's car stereos don't use a "common ground"
Looking that the circuit schematics, Stan appears to be correct. The outputs are marked + and - and not referenced to ground so it seems they are diferentially driven, which is smart. It's more immune to interference.
Originally Posted by dberladyn
I pulled a cover off an older amp today ... the connections are all grounded.
The input should be grounded but not the output.
I think the mixing circuits will still work. You just have to mirror whatever you put on the + and - lines (resistors, opamps or what have you.)
Last edited by mountainmanjoe; November 30th, 2018 at 2:17 AM.
I haven't tried my Onstar lately. You can pull your Onstar box out and install "Bluestar" in it's place. I won't bother with either, but it might be for you.
So what is the deal with Digital Amps compared to the old school analogue amps? I never really dwelved into it, but I read all the hype that the new amps are compact, more efficient and create far less heat. My 4 x 150w Hertz HDP4 that I assume is not working properly is digital. Is this all hype, or you think there is a more advanced means to get that power in a smaller box? I am thinking there is. I am also thinking it is far less reliable and far less serviceable. Lots of older amps on CL. I'd lose space, but they are cheap and I bet they work like the one I have configured for 200W per speaker. It's smoking hot to touch, but it's working.
Last edited by dberladyn; November 30th, 2018 at 2:29 AM.
As for the OnStar, unless it's broken, by law, it should dial 911, service or not. And that applies to any cell phone. And say what you will, but if you're pinned down and your cell isn't within reach, that red button on the dash could save your life.
Just a guess, but "digital" probably refers to that "optical" input. I've never seen it on car equipment before, but I have been out of the business for quite a while.Optical is a digital mode, sent over fiber optic line. There may also be some analog to digital conversion and back again, but that shouldn't make more power in less space, and isn't efficient. It uses more electricity to do that, not that there's a limited supply, but still. The mundane circuitry can get smaller, but the output transistor still needs to be the same size it always was.
And you probably don't want to try home equipment in a car. It doesn't have the filters needed to keep it clean and quiet.
I read up on all of this at one time, and I do not want to spend hours reading and absorbing this morning for a refresher, but it is probably a reference to the below in combination with Marketing...
Class D
Often erroneously referred to as “digital amplification”, Class D amplifiers represent the zenith of amplifier efficiency, with rates in excess of 90% being achieved in the real world. First things first: why is it referred to Class D if "digital amplification" is a misnomer? It was simply the next letter in the alphabet, with Class C being utilized in non-audio applications. More importantly, how is 90%+ efficiency possible? While all the amplifier classes previously mentioned have one or more output devices active all the time, even when the amplifier is effectively idle, Class D amplifiers rapidly switch the output devices between the off and on state; as an example, Class T designs, which are an implementation of Class D designed by Tripath as opposed to a formal class, utilize switching rates on the order of 50MHz. The output devices are typically controlled by pulse width modulation: square waves of varying widths are produced by a modulator, which represents the analog signal to be reproduced. By tightly controlling the output devices in this way, efficiency of 100% is theoretically possible (although obviously not achievable in the real world).
I was given this amp as a throw in when buying something else. It was free. An MTX (brand). It weighs a ton. It's in an ugly chassis (my tastes). I never planned on using it. I have tried selling it several times. No interest. Today I decided I'd pull the cover off and I am glad I did. See those large black cylinders? They are shot. You can tell by the deformation on the top of the can. Going to Mouser it's going to cost roughly $25 to order new ones. I can upgrade them for another $2 - $5. Of course there are some similar amps on Craigslist for $30 to $50 so... I am not sure. I emailed a few people. The ones that replied have already sold what they listed. I am not wanting to spend $300 or more on something I do not really want. Maybe I should order new capacitors for this amp? Maybe have it running in two weeks, use it as a stop gap measure and try selling it again? The one thing I over looked is the quality. This amp is really heavy due to a huge heat sink. That's good! It has good reviews online. People who own it like it.
However what I think I really want to do is... I want to buy the appropriate pre-made 'blocks' and build my own custom set up. I can do this after reading this morning. For the price of each amp 'block' per speaker I can buy all six of them plus choose my desired heat sink size / shape for the price of one store bought amplifier. Wiring will be the way I want it with no extra setting switches. Everything nice and SIMPLE. Mount them onto slide out trays under each seat and bob is your uncle. Of course, just by looking at the pictures and comparing the circuitry... I do not know, depends on the chips right? Also, it is not fair to compare by looking at the picture. The MTX Amp probably has voltage converters, energy storage and switching circuitry for different setups. Not to mention to some filters. All things that can be added to 'blocks' as needed. For a direct comparison, the MTX Amp likely only has actual amplifier circuitry in the far left and right cluster of components. So they are comparable.
An another idea is to mount the amps outside, under the floor of the seats inside sealed aluminum enclosures. Save space and cool them at the same time. I wonder how that would work in the winter with below freezing temperatures or in the Summer in cooking heat while idling in traffic? I like all this stuff. I like to explore ideas and learn no matter the 'hobby'.
Last edited by dberladyn; November 30th, 2018 at 2:48 PM.
Class D amps are super efficient. As the price of silicon goes down, these will probably become ubiquitous.
Originally Posted by StanVan
As for the OnStar, unless it's broken, by law, it should dial 911, service or not.
The blue button definitely doesn't work. It just beeps forever. I don't know if the red button works, but I'm not going to test it.
Your statement doesn't make a whole lot of sense though. If a particular technology is discontinued and simply doesn't exist any more, then there's no law that will make a button work again. I contacted OnStar and was informed that the technology it relied on was phased out. They quoted me a really large dollar value to upgrade the system to make it work again. If something happens to me, I'm more likely to be closer to my cell phone than that red button.
I am going to do this. I am going to sell the Hertz Amps that I have and go this route. I like it.
There are so many designs. So many options. Some of them are just direct copies of high end gear that was sold over the years. From what I have ascertained the only thing to watch out for is whether the board is designed for an AC or a DC power supply. Nothing operates at 14 volts. This is what I am concluding. Even the car amplifier I show above, it steps the incoming car voltage up to 35 volts for the amplification circuits. At least I currently believe it does. I could use my DENON amps. I believe they are running at 71 volts. The only problem with them is that they are AC (which may not even matter realistically). I do not want to do that anyways. They are too special to me. I used to dream and drool over the desire to have them when I first started buying stuff. Even if they are only mediocre, they are a 'classic'. I am wishing I built my own home amplifiers 15 years ago. It would have a fun hobby. I could have even got into tube amps.
Ok.. so on to the truck. I guess the place to start is the desired wattage. What wattage do I want to send to each speaker?
1-1/4" Tweeter
3" Mid-Range
6.5" Woofer
12 Sub-Woofer
Specifications for each. At least Specifications for what I will use for "Reference" Speakers. Too much power is Ok. Perhaps I will just do what the Product Sheets state (see here)?
After that, it is deciding on which Chips to use as the actual Amplifiers. Then, the corresponding Circuit 'Block'. Then DC-DC Step Up converters for the power supply.
I would need to buy another multi-meter to be sure of my assumptions above but... if I am wrong, it just gives me even more options for speakers. House speakers are cheap. People cannot give away their old higher end equipment. I myself have 12 quality 5-1/2" Woofers and matching 1" silk dome Tweeters. They sound excellent with the right amp. They cost a fortune, but they are worthless on the market. People do not think of the components, they think of the cabinets. No one wants all these speaker cabinets anymore.
By the way, there is a good chance I am wrong which is why I should pick up a multi-meter. Everywhere I have read on car speakers... people have claimed they run at the car voltage. So 14 volts max. I'll figure it out. Just reading from somewhere else:
Voltage = Square Root (Power x Impedance)
So for 100 Watts into an 8 ohm speaker
Voltage = Square Root (100 x 8)
= Square Root (800)
= ~28.3 Volts
If I do the same with a 4 Ohm speaker:
Voltage = Square Root (Power x Impedance)
So for 100 Watts into an 4 ohm speaker
Voltage = Square Root (100 x 4)
= Square Root (400)
= ~20 Volts
I am going to assume my DENON equipment is at 70 volts at the Power Supply because it's AC. 35 volts per Rail.
35 volts is what I already had in mind after looking at all the various boards. It's probably correct unless someone knows different. The car speakers I have are probably designed for 14 to 20 volts, but I need to buy a new multi-meter to be sure. House speakers may be designed to handle as much as 40 - 45 volts, I am not sure. It makes sense as the common impedance is 8 Ohms. Twice the Voltage, twice the impedance. I read some time ago that cars use 4 Ohms because of the lower voltages on hand. It just became it's own standard. I suspect car speakers are different as my amps didn't perform well driving my 4 Ohm house speakers. Source here: https://theartofsound.net/forum/show...ge-to-speakers
This explains why my existing car amps didn't drive my house speakers properly. I couldn't get much volume out when I tried individual components. Maybe I ruined that one Hertz Amp trying?
[ Not sure if anyone else is interested in this, but it is interesting to me. At least to explore. ]
Last edited by dberladyn; November 30th, 2018 at 7:33 PM.
November 30th, 2018, 1:21 AM
