# DIY car audio amplifiers - why not?



## Spasticteapot (Mar 5, 2007)

To put it bluntly, I've seen a lot of truly bad car audio amps. A 60wpc high-fidelity four-channel amplifier can cost hundreds of dollars. 

On the other hand, the LM3886 "Overture" series of amplifier IC costs a whopping $5 (though I've seen them for $2 at some surplus warehouses), can produce up to 60 watts, and requires about sixty cents worth of other components to produce an amplifier that can hold its own against home-audio amplifiers costing $500 or more.

I think you can see where I'm going with this.

Two parts are needed for such a setup: A standard home-audio power amplifier schematic, and a high-efficiency power supply. 

Amplifier designs:

1: 41hz Amp9 Basic
http://www.41hz.com/main.aspx?pageID=130


This four-channel 100w (60w before it starts to sound like crap) amplifier is tiny, efficient, and of very good quality - it's a Tripath (same as the Sonic Impact T-amp), and a good one at that. 

This amplifier has an additional advantage over most - its operating voltage. Because it requires a single 24v supply (no center tap!), and is over 85% efficient, making finding an appropriate supply both cheap and easy. In fact, good results can be had anywhere between 22 and 27 volts.

While $65, it's a heck of an amp for $65, and worth every penny - or, at least, that's what I've heard from people who have built it. If you want an even higher quality tweeter amplifier, the 2-channel 30wpc Amp4 might fit the bill - it's pretty small in terms of power, but I've heard it's hard to beat.

Finally, it has one advantage over just about every other amplifier on the market - size. Not only are the PCBs miniscule, but the high efficiency of these amplifiers mean that you can use a tiny heatsink - an old computer heatsink should be fine, and can be had for just a few bucks.

2: The Gainclone
(many variants)

The Gainclone refers to the Gaincard, a $2,500 amplifier based around reference design schematic for the lowly LM3886 power amplifier op-amp IC. To build one of these, you need a couple of $3 ICs, and a couple of bucks worth of parts.

The real issue with the Gainclone is the split power supply - it requires between 45 and 55 volts with a center tap smack dab between them. On transformers, this is a simple issue of adding a third lead halfway through one of the coils, but with switched-mode power supplies, this is a bit more tricky. (If anyone wants, I know some people who get paid to design this sort of thing, and might have a pretty simple solution.)

It's pretty easy to build a Gainclone, even without a PCB. However, Audiosector carries a kit for the LM4780, which is essentially just two LM3886s in one package. Four channels will run you $75, and it's a very easy to assemble kit - in fact, it's often reccomended for a first amplifier kit.

3: The Pass Aleph
The Nelson Pass Aleph (and all eight bajillion variants therof) is one of, if not the, best amplifier in the world. Distortion is negligible, but it comes at a cost - every other aspect of the amplifier is sacrificed at its expense. Because the amplifier runs completely in class A, it's massively inefficent - roughly 25%. This means that a massive power supply and massive heatsinks are required, although you may be able to offset the cost - even the smallest of the Aleph amp variants can replace your heater.

I won't go into the details, mostly because there are many, many, many of them. Just let it be said that all of them use expensive transistors, all are massively inefficient, and I've yet to hear of anyone who really disliked them.

Power supplies:
For a car amplifier, a swtich-mode power supply is optimal. Not only is it the easiest way to increase the ~12v output from your car alternator to the levels where an amplifier can use them, they're also highly efficient, reducing heat output and requiring less power. 

Most of these amplifiers have two parts: A bit which turns the 12v DC into 12v AC, and some sort of inductor or transformer. Since these are usually custom-made and hard to get off the rack, it's likely to be necessary to find one used for some other purpose - usually, there are several of these in any computer power supply.

Alternately, it might be able to find an off-the-rack power supply. If anyone has any reccomendations, feel free to post them.


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## SQKid89 (Feb 22, 2007)

i've built a couple of gainclones in my time, got their guts everywhere around my room. been looking to get something from 41hz for a loooong time for my home theater setup.


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## Cancerkazoo (Jul 21, 2006)

12v SMPS for automotive gainclone.


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## solacedagony (May 18, 2006)

I was planning on trying out my first DIY amp from chipamp.com. They include everything in the package, plus show you how to put it together.

I found a good extremely small head phone amp awhile back that I was also interested in trying out.


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## Preacher (May 8, 2006)

I love the idea of this, but I probably lack time, space and knowhow. I looked into it a bit last year and got stumped at the power supply's. I'd like to know more about that. Can you guaranty they'd be quiet?


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## ws6 beat (Jul 14, 2005)

i'm building a simple killer amp from greg, that'll be a great idea.


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## CaseyWalsh (Jul 25, 2005)

ws6 beat: If you’re going to use the SKA in your car, what do you have in mind for the power supply?


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## Spasticteapot (Mar 5, 2007)

Preacher said:


> I love the idea of this, but I probably lack time, space and knowhow. I looked into it a bit last year and got stumped at the power supply's. I'd like to know more about that. Can you guaranty they'd be quiet?


The power supplies I can guarantee will be noisy as heck.

Of course, we're building these ourselves, and are'nt going to cut costs - a $10 inductor and a few well-placed capacitors can reduce the noise to negligible levels.

Furthermore, as long as we're at it - why not put the PSU in a seperate box entirely to reduce RFI?


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## DonutHands (Jan 27, 2006)

i would love to have some tiny amps with nothing but gain controls. it looks so easy and yet so hard at the same time, i wish someone would take the plunge and start this for us. i would love to stuff 12 channels of amplification into one box. im sure it can be done, just like that 8 channel amp which i cant remember the name of.

i remember seeing someone on here that made thier own car audio amps and put them in the spare tire wheel well and had enough room to place the spare in the same space. wish i could remember who it was.


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## Spasticteapot (Mar 5, 2007)

internecine said:


> i would love to have some tiny amps with nothing but gain controls. it looks so easy and yet so hard at the same time, i wish someone would take the plunge and start this for us. i would love to stuff 12 channels of amplification into one box. im sure it can be done, just like that 8 channel amp which i cant remember the name of.



Just take the boards out of six of these. They run off of a car battery!

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-952

The Sonic Impact T-amp is actually a spectacular amplifier - just low in power. While you can get 2 channels at 15 watts each, they only sound good up to about seven watts per channel. That said, those seven watts will sound very, very good, and you can get your twelve channels for $180. (Actually, I think you might be able to get these for $20 - $25 each if you're buying six, so it might be more like $120-$150)

If you were going to use these in a car, I'd add some 10,000uf capacitors to the power inputs, though. Four 10,000uf Nichicons will only cost you about $5 at ApexJr.com. For the case, I'd mount 'em inside a Pyramid power amp, with the amplifier IC where the power transistors used to be.

Finally, a hi-fi use for Pyramid stuff!


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## thehatedguy (May 4, 2007)

I put a couple mini Aleph boards into my Monolithic A501 monoblock chassis. Damn they were noisy...but the A501s were dead silent.

Building a good quiet SMPS is no trivial task. There are literally entire text books written on the subject.


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## Spasticteapot (Mar 5, 2007)

thehatedguy said:


> I put a couple mini Aleph boards into my Monolithic A501 monoblock chassis. Damn they were noisy...but the A501s were dead silent.


Go to diyaudio.com. Odds are, you built it wrong.

Of course, you could sell them to me. 



thehatedguy said:


> Building a good quiet SMPS is no trivial task. There are literally entire text books written on the subject.


I have a frathouse full of electrical engineers who will very soon be owing me a favor.


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## thehatedguy (May 4, 2007)

I've been on DIY Audio, I got the boards from BrianGT. The noise was from the PS in the Monolithic and no filtering on the Aleph.

Then there is no soft start feature on home amps.

It's a lot of work...take a look at the Werewolf Amp post.


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## Spasticteapot (Mar 5, 2007)

thehatedguy said:


> I've been on DIY Audio, I got the boards from BrianGT. The noise was from the PS in the Monolithic and no filtering on the Aleph.
> 
> Then there is no soft start feature on home amps.
> 
> It's a lot of work...take a look at the Werewolf Amp post.


I'm a home audio person - I don't actually have a car. I'm just here to make trouble, answer questions, and buy used parts.

Speaking of which, I'd REALLY like a stereo set of those Pass boards...


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## Kenny Bania (Aug 1, 2007)

What's the feasibility of putting some of these together in a car audio amp design??

http://www.icepower.bang-olufsen.com/sw2014.asp


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## chad (Jun 30, 2005)

Spasticteapot said:


> The power supplies I can guarantee will be noisy as heck.
> 
> Of course, we're building these ourselves, and are'nt going to cut costs - a $10 inductor and a few well-placed capacitors can reduce the noise to negligible levels.
> 
> Furthermore, as long as we're at it - why not put the PSU in a seperate box entirely to reduce RFI?


I think preacher is refering to ground isolation.


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## chad (Jun 30, 2005)

Spasticteapot said:


> I have a frathouse full of electrical engineers who will very soon be owing me a favor.


I'm not even going to ask why or even go there


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## Spasticteapot (Mar 5, 2007)

chad said:


> I'm not even going to ask why or even go there


They wanted a subwoofer.

Let's just say that they'll be very, very happy with my reccomendation.


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## ws6 beat (Jul 14, 2005)

no im using my ska for my natalie p's for my ht.


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## Spasticteapot (Mar 5, 2007)

ws6 beat said:


> no im using my ska for my natalie p's for my ht.


In english, please?

As a side note, does anyone know of any 12v->24v step-ups?


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## ca90ss (Jul 2, 2005)

CaseyWalsh said:


> ws6 beat: If you’re going to use the SKA in your car, what do you have in mind for the power supply?





ws6 beat said:


> no im using my ska for my natalie p's for my ht.





Spasticteapot said:


> In english, please?


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## SQKid89 (Feb 22, 2007)

IIRC, SKA is referring to a certain type of chip amp setup, while the natalie p's are his speakers....? 

did i guess right? i want my cookie


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## ca90ss (Jul 2, 2005)




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## CaseyWalsh (Jul 25, 2005)

SKA = “Simple Killer Amp”, a design by Greg Ball who I’ve seen at diyaudio.com (I think), DIYHiFi.org, and now his own forums at ska-audio.com. It is *not* a chip amp.

The Natalie P’s are an MTM speaker design with quite a following.

http://www.htguide.com/forum/showthread.php4?t=13969

Cheers,
-Casey Walsh


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## CaseyWalsh (Jul 25, 2005)

Oh, an updated cookie...


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## frito (Sep 11, 2007)

I have been looking at the 41hz amp 9 also. There is at least one guy on the forum at 41hz running it off his car 12v with good results. I may try this.


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## chacalpowers (Jul 18, 2008)

*SMPS for car amp*

Hi Dears

This is my car audio SMPS. Input 13.8V-output +35/-35V.
I like it so much.

REgards.

Sandro/chacalpowers


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## nrhyan (Jan 1, 2010)

just wanted to thank you for posting these DIY amp-kit resources. Im a lifetime thirdcoaster myself, now recently in Madison. Let me know if you would be up for trading any electronics/parts!

Nick

[email protected]


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## Dryseals (Sep 7, 2008)

Power supply should be the simplest part. There are many ways to do it. In the end all you are looking for is a way to make 12VDC into something much higher. I've seen it done in many ways and I'm sure many of the old Navy ET types can tell you the same. Stability is the key. Transformers are the easy part, there are already a ton of transformers for going from 120VAC to what ever you want and twelve volts AC is a common. And the transformer doesn't care too much about which way the feed comes from. 

One of the simplest form in the old days was a 60HZ ocillator whos output drove a relay that turn on and off the contactors. Then the power was fed through the contacts, on and off 12VDC. Feed it to a center tapped xformer as +12 on the on cycle to on leg and +12 on the off cycle to the other leg.

With newer components, you can replace the older relays with a faster high current device. A fast SCR (Silicone Control rectifier) come to mind. Crank the ocillator speed up to around 1000HZ and you have instant AC that you can smooth down. The faster the ocillator the easier it is to smooth out the voltage.

For a DIY car amp, I would make the power supply a seperate device and build it very strong. That way you could tap it for what ever you want.


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## DirtyDog (Jul 30, 2009)

interesting post..subscribed


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## Luke352 (Jul 24, 2006)

These guys produce D class modules that can be used in a vehicle when hooked up to one of there Power Supplies or you could make your own power supply.

Class D Audio Car Moblle Audio - Amps


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## chipss (Nov 13, 2009)

I know this is an old post but man I sure like building stuff myself....
wonder if anyone has built a car amp yet that worked as good or better than 
whats out there?


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## splicer (Oct 4, 2008)

Dryseals said:


> Power supply should be the simplest part. There are many ways to do it. In the end all you are looking for is a way to make 12VDC into something much higher.


Funny, because to me the power supply is the hardest and most expensive part. Once you have a power supply, it's just the LM3886 and you are done...


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## Dryseals (Sep 7, 2008)

splicer said:


> Funny, because to me the power supply is the hardest and most expensive part. Once you have a power supply, it's just the LM3886 and you are done...


Power supplies are the easiest part to build, problem comes in when you start factoring in size and heat. The key for a power supply is having something that can supply the needed power for short burst and long term. If you allow me to make one the size of a shoe box, I can build one that will more than enough for anything you want. Try selling that for some one in a Honda Civic. so manufacturers make them very small, then you run into problems with heat. Heat is your killer.

The chips for the audio section audio have been around for ages, they are not very large and have been designed to be mounted for heat dissipation.

Back many years ago I had a very nice Kenwood home amp, it use 63 volts DC on each chip for the power section. the final stage IC's were no larger that wide pack of gum mounted on a large aluminium block. The amp was very heavy, all power supply, transformers.

I use a lot of 24 power supplies for my job, very high current, very heavy, very stable. The transformer is most of the weight.

If you want to build a better system than whats on the market, as you pointed out, the chips are there. But you need to get power to them in a better manner than the manufacturers do, They have to cut corners to make it fit, you don't have to.


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## chad (Jun 30, 2005)

Dryseals said:


> If you allow me to make one the size of a shoe box, I can build one that will more than enough for anything you want. Try selling that for some one in a Honda Civic. so manufacturers make them very small, then you run into problems with heat. Heat is your killer.


I can power my WHOLE civic off a power supply plugged into the wall audio and all and it is in the box size of baby shoes, and hidden. It's totally possible. There are lots of places to hide things in a car that people don't see. Going with one big-ass hidden power supply takes us back to the old zapco days, and being differential output you could put it anywhere and not worry about noise.

Especially if you put a big cap-bank in the trunk with a passive network on it to shunt any HF junk... see you CAN effictively run caps then  Caps work GREAT AFTER a differential power supply... just like any other amp out there


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## Dryseals (Sep 7, 2008)

chad said:


> I can power my WHOLE civic off a power supply plugged into the wall audio and all and it is in the box size of baby shoes, and hidden. It's totally possible. There are lots of places to hide things in a car that people don't see. Going with one big-ass hidden power supply takes us back to the old zapco days, and being differential output you could put it anywhere and not worry about noise.
> 
> Especially if you put a big cap-bank in the trunk with a passive network on it to shunt any HF junk... see you CAN effictively run caps then  Caps work GREAT AFTER a differential power supply... just like any other amp out there


We use a lot of 120VAC to 24VDC supplies for equipment. The caps in there are big enough that it takes a while for the output to drop off after the power switch is turned off, even when loaded.

With all this SQ talk floating around, it might be time to go back to a seperate power supply, get rich quick and retire soon before the craze fades into another section.

Hmmm, develope a power system than can be used to supply a fixed DC to feed smaller devices and highs outputs for larger devices. Upgradeable for futures sales, uh, improvements. Outputs floating for isolation from outside noise. Modular for quick changes and up grades. And then sell a copper bar bus system to allow you to transfer power to any section of the vehicle. We won't call it wire, we'll call it the Zanar Bus system.

Promote the side benefits, cracked frame on the car, use the Zanar power supply to weld it up.


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## chipss (Nov 13, 2009)

somone say wire? muhahaha
Dryseals: DIY amp building has done nothing but make me poor....lol


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## splicer (Oct 4, 2008)

Dryseals said:


> Power supplies are the easiest part to build, problem comes in when you start factoring in size and heat. The key for a power supply is having something that can supply the needed power for short burst and long term. If you allow me to make one the size of a shoe box, I can build one that will more than enough for anything you want. Try selling that for some one in a Honda Civic. so manufacturers make them very small, then you run into problems with heat. Heat is your killer.
> 
> The chips for the audio section audio have been around for ages, they are not very large and have been designed to be mounted for heat dissipation.
> ...
> If you want to build a better system than whats on the market, as you pointed out, the chips are there. But you need to get power to them in a better manner than the manufacturers do, They have to cut corners to make it fit, you don't have to.


You keep saying power supply is the easiest part for DIY, then talk about all the concerns with heat and size, and how the chips exist and the problem is getting power to them. You're not doing a very good job making the case that the power supply is the easiest part. It sounds to me like the power supply is just the part you understand the best. But that doesn't matter because with today's chip amps, you don't have to understand the amp part. You can make a great amp with a single chip (LM3886) and a power supply.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> I put a couple mini Aleph boards into my Monolithic A501 monoblock chassis. Damn they were noisy...but the A501s were dead silent.
> 
> Building a good quiet SMPS is no trivial task. There are literally entire text books written on the subject.


If I was going to build an amplifier for the car, this is the one that I would build. I never understood the allure of the gainclones, since the circuit isn't substantially different than what you would find in a lot of consumer amplifiers. But the Mini Aleph is something entirely different.

If anyone is interested in building one, you can use laptop power supplies to run it. Someone on diyaudio did this. So you could literally spend $40 on a pair of SMPS power supplies and get "up and running" in an afternoon.

Then again, using laptop power supplies for your amplifier is kinda ghetto 

The dude who did that on diyaudio also used a computer heatsink and fan, which I thought was rather brilliant


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## Patrick Bateman (Sep 11, 2006)

Dryseals said:


> Power supplies are the easiest part to build, problem comes in when you start factoring in size and heat. The key for a power supply is having something that can supply the needed power for short burst and long term. If you allow me to make one the size of a shoe box, I can build one that will more than enough for anything you want. Try selling that for some one in a Honda Civic. so manufacturers make them very small, then you run into problems with heat. Heat is your killer.


This is why I like the idea of using computer heat sinks. They cool the amp more effectively than a huge heat sink. Basically build an aluminum tunnel, put the heatsink and fan on one end of the tunnel, the amp itself is IN the tunnel, and air is circulating through it all the time.

The Zalman fans are completely inaudible in a car (assuming the amp is in the trunk.)

If anyone here is into high performance computing, they're starting to do things like this with computers, but at a much larger scale. Instead of an amplifier in an aluminum tunnel, they put an entire data center into a steel tunnel. The advantage of putting the data center in a tunnel is that you can run air through the tunnel. When you have twenty thousand CPUs in your network, fan failure is a nightmare. A few big fans are easier to manage that 20,000 small ones.









In this pic you can see some huge fans on the edge - those are pushing air through the tunnel. And yes, that IS a shipping container


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## Dryseals (Sep 7, 2008)

splicer said:


> You keep saying power supply is the easiest part for DIY, then talk about all the concerns with heat and size, and how the chips exist and the problem is getting power to them. You're not doing a very good job making the case that the power supply is the easiest part. It sounds to me like the power supply is just the part you understand the best. But that doesn't matter because with today's chip amps, you don't have to understand the amp part. You can make a great amp with a single chip (LM3886) and a power supply.


Sorry if I can't make the case well enough, I've only been in the electronic world for close to 40 years, 35 five of those with a meter in my hand. I've seen the transition from tube to transistors to IC's and beyond.

Power supplies have had some major changes, but for the most, the only thing that has changed for them is how they operate, energy efficient.

What they have tried to do is reduce the size of the supply and for the sake of less heat, make the supply only produce what is needed, kind of an on demand power supply. If that's the type of supply you want then it's going to get complex.

But if you are willing to endure some excess heat and size, going back to the old tried and true relaible power supplies are the way to go, big bulky and can take some abuse.

As for the audio side of things, I've been there just as long. Started with tube amps and moved forward. I can't tell you how many 2N3055 I changed out, used to be the favorite of every manufacturer, sit for hours with a stack of JAN2N3055's to find a matched set.

The last one I built was a kit, Hafler. But had some good specs. If you look through the manual, you can see by the pictures that the whole thing was mostly power supply and heat sinks. The power supply was there no matter what level you were playing.

I have an Onkyo TX-SR703 in my shop for music, doesn't get near as hot as the Hafler or the Sony 55ES. But you can hear the power supply switching on and off as you adjust the levels.

63 volts on the Hafler gave you 100 watts at eight ohm. 63 volts is not that far a stretch for a 12 volt source.


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## Dryseals (Sep 7, 2008)

Patrick Bateman said:


> This is why I like the idea of using computer heat sinks. They cool the amp more effectively than a huge heat sink. Basically build an aluminum tunnel, put the heatsink and fan on one end of the tunnel, the amp itself is IN the tunnel, and air is circulating through it all the time.
> 
> The Zalman fans are completely inaudible in a car (assuming the amp is in the trunk.)
> 
> ...


One site I worked at was two levels, bunch of HF transmitters, 30 and 50KW types. The whole basement was an air conditioner, you walked into a room that was full of walls of coils. Air was first cooled using water, then on to the A/C unit. The upper floor was grating every where. Big FD fans blew cool air up throught the equipment. It was kept at 64 deg F all year round.


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