Building a Class Amplifier from Scratch

Circuit Class A Single End Amplifier - Final

View attachment Class A - Single End Amplifier without Servo Control.pdf
The Circuit you will find added as PDF file, is the finished Class A Single End Amplifier.
The Amp has been build several times in different Version, this version is the best in any point of view.. at least from my point of view..
I will draw a Layout for regular heatsinks as I use special heatsinks. you will not come around to use FANS but Fans can run on low speed so you will not hear them, but the beatifull and naturelle sound of that Amplifier.

If you want to drive loads as low as 2 ohms output Transistors has to be added.
with 4 Transistors it's easy to drive loads at 4 ohms and no need to worry about output distortions. The Amp can handle it very well.

The pictures from yesterday, with the new PCB has been build and tested already. I was on it all day long today.

As soon I have some spare time or more spare time I'm going to place the build up of the Amp with all there is to know. Pictures are made already but pictures alone don't tell what is behind it.

I do not take responsibilty for Failures or Faults, burned fingers or whatever could happen while building this amp. I also do not be held responsible when your Electricity bill will increase by 100% while using this amp. In wintertime you can use this amp as a heater..

Thanks for Acknowledgement.
Regards Chris Hess..
 

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Class A Single End - ready to get Boxed

OK Now the amplifier case is almost ready to place both Sides of the amp in there.
Of course also PSU and also Speakerprotection. Switchable input selector Infrared Remote Control, as well as DAC converter for Fibre Cable. The case has just the right size, thanks to passed away Steve Jobs his inventions, it's just a beautiful case.. And it can be reused...
Here the pics how it looked last night at 7 PM and then an hour later.. it still needs alot of work both sides *Pictures 5&6* needs to be cut out and then again newly fitted in with the same kind of closure grill as it is looks now.. but because of the switches and CDROM slots so it's no use for me.
Then all the standing bolts in the case have to be removed *Picture 2* and after that the case will be inside cleaned and measured out to place the AMPS in.. soon to be true..
BTW I am going to build a CLASS A AMP. Nothing in between, a real SINGLE END CLASS A .. Despite some people think this isn't worth it.. it's more than worth..Wait and See, just too bad that you can't hear the sound of this one..OH BTW it will have a COVER also. Nice one BTW, in memory of Steve Jobs, the Apple Logo on top will be kept.
Thanks for Reading.. Pics are named so it's more or less self explained.
Regards Chris
 

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Measurements and Tools used

Current is measured across the FUSE HOLDER where the Positive or Negative Wires from PSU are connected. When the AMP is BOXED into it's CASE there will be real thick Cable will be used. It's just to make sure that Power flows easy. but just to test there is a wire of a Length of 25 CM, and 1 Square millimeter more than good enough for about 16 ampere on that Lenght.(Multiple wire inside the test wire of 1sqm)

If you are talking about the Power Connector from Wall Outlet then it's a 3 Pole inclusive Earth Female Connector, 25 Ampere Secured same a Computer Supplies using it.. only that the one I use has also Noise filters and Fuses within the Female Plug, which is fitted into the Case.
But I see you are talking about the Measure unit.. I made this system, so I do not need to measure across any resistor.. Removing the FUSE either one is good, because Amp flow is real equal down to 10 milliamps..between Positive and Negative Rails. Then inserting my System into the Fuse Holder.. When the amp is build into the BOX then it's very important that the measurements can be made without to have to remove the half of the Amplifier.. Seen this so many times.. got me upset and angry so many times that developers don't think farther than their nose length.

So the System is a Blown fuse which is soldered on two solder boots - you know the Brass small Bolts to connect wires on the PCB. then using a small PCB with two wires which connecting via BANNANA Plugs to DVM in this case DAM= Digital Ampere Meter.
Inside the CASE I use 4SQM wire with a Cable Lug soldered to each end and sealed with shrink rubber, for Connections under 10cm For connections longer than 10cm I use 6sqm Cable in three colors.. same as the short ones with cable lug, and shrink rubber then these will be screwed onto the PCB to the already soldered counter part. the cable Lugs will be Gold Plated.. the cables are OFC= Oxygen Free Copper 6sqm /750 volts 75 Degrees heat.
Check out the pictures.. BTW, the screws will be fastened with a Torquewrench, this also counts for fasten the TRANSISTOR PRESSURE PLATE..or when transistors have to be fastened then also.
I do not take Chances or I will at least try to minimize the chances that because of bad manufacturing or Production faults, the AMP will fail.. This is the LEAST I CAN DO for a long time use..
hope to have answered your question..

Regards

Chris Hess
 

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@hpro,
What kind of power connector are you using (is the current measured within the connector, fancy)?
Link to the pic: https://www.diyaudio.com/forums/att...ifier-scratch-3-class-single-build-mac-g5-jpg
The Connector behind is connected to wall outlet and there are connected to
1. Three Power Amps all of them CLASS A
2. Pre amp - Audio Research SP9
3. Internet Box
4. Subwoofer Unit amplifier, almost never used
5. Vinyl Washing Mashine - Ultra sound - Made by me - Record will not have contact to anything else than Water solution for the ultrasound . Sold 120 Pieces
6. Record Dryer rotating
7. 24 Channel 1Ghz Hub
Overload Secured to 220 - 240 Volts @15amps Master Slave operation. If there is no load connected (Ampere Selectable) the Master will not open the SLAVE
When short ciruit the Master cuts of the connector which has the short.
But this is not my Working room this is our Living room
Working room is a lot more sophisticated..
Hope to have answered your Questions, more question, all you have to do is ask.. I serve you with true answer as it is..
Regards
Chris
 
Case Modeling and getting space

So,
Took a few days to get on with this, as I do have a Business to run besides that..

Today the BOX will be ready to get the AMPS into it.. Last night removed the Stands from that G5 Case because, there is no use for these Stands*thread Bolts*. Now today the Side Panels needs to get cut out.. which will be replaced as soon the Output stages and PSU has been placed.. As the case is rather huge 19" x 15.5" x 7.8" I'm trying to get a Quad amp into it.. But first I need to decide how to make the Air channels to release the heated Air out of the case so that this will use up as little space as possible, and that 95% or more of the air does leave that Case. Then also need to decide where the SLOT for intake of Fresh Air must be..

I also see a possibility to change the Layout to the PCB to gain some Space there as well, not much, but at least 2" per PCB as the PSUis rather large..

Going to place 2x 1000VAC Toroid Transformers in there of course Stacked as well as the PCB stacked.. too.. The large Resistors will be screwed against a large heat-sink at the back of the AMP, Resistor inside that Amp, will be in the AIR CHANNEL of the AMP itself and then the Heat-sink will be mounted outside at the back-plane. Then also Wall outlet connector 3 Pole, Noise filter including Main fuse, Speaker Terminals..Inputs

Check out the Pictures.. It's Still a lot of Work..

I don't think that Push Pull AB Amplifiers with A bias are PURE CLASS A.. I doubt that very much.. but many People build them.. I build my Own, of which I can say, it's Pure Class A, and I also I'm willing to take all whatever it needs to finish it..

But reading here on this Forums helps me to understand the MAINSTREAM and it helps me to even more make my Decisions what Kind of Amp, for me is worth to build..
For me Class A, is loss of Energy to a high price, it's loss of Efficiency to a high price, it's a lot of HEAT which could be used otherwise. BUT the Pureness of the SOUND which it's delivers, is just MIND BLOWING, or call it fantastic clean clear and Pure.

Always thought that these Class A, I build before with Current Source Transistors where good.. since I listened to this Single Ends, I changed my mind. Either the Transistor Version or the IC Version, I think this is very near the truth of what uncolored sound, should sound like..

Thanks Guys,, check out the Pictures of the CASE MODIFICATION which have to be make to make this happen.
And, the pics are only to show how it should be, so if there are 90Degrees angles which are only 88 forgive me.. the Real one will have 90 degrees, these pics are just meant to give you an impression how it will look like.. Don't know yet if this is going to be enough space for a 4 channel or only 2 channel.. Will find out.. 2 channels are ready to place in the box as soon the modification have been made..* hopefully today*.
Regards Chris
 

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Project closed

Building A Class A from Scratch

Hi everyone here..


Guys I thought the circuit I placed in one of the pdf which is a 3 transistor CLASS A SINGLE END Circuit, was made by me.

I got an Email this very early morning at 6am, where one Person told me that this cirquit has been done before or at least a good Portion is from that person, that's why I will stop this project right here.



I was stupid to think that this could be mine, Sorry about that.

So I'm not the Guy who is going to copy paste from anyone else..

If this has been done before then:


Project closed.


Moderator please delete this thread.


Regards

Chris Hess
 
The Original Circuit of the one in Question

Hi
Sorry about this Break, the Circuit owner and I'm are in contact and it seems that this project is going to finish one or the other Way.. As there are so many cirquit out in the open, it's sometimes really hard to find out who acutally is the owner of it.

Now, anyway I was looking at my build from 1976 and found that circuit you will see below.. The stages after the IC UA741 are close to the Single End I posted earlier here..

I used this in 1976, and I used it modified till the year 2000.. Take a look and compare the driver stage and you will see the similarity. I would be happy to give credit to anyone who is the man of thought. But in 1976, I found this in a Thai Magazine, Electronics World to DIY.. they didn't State who was the owner or from where they got it.. Asia isn't Europe or USA.. I Lived there from 1974 till 2002.

So this one I place here is the origianl as it was in that magazine. Only numbers of transitors have been changed and I can't find that Magazine anymore.. I just have the Cirucuit,

I never used that circuit the way it is drawn, because of it was very unstable and not enough power came out of that..
I modified this several times.. I have also the one which was modified. but we keep that for a later day. May we are lucky to get the guy who was the one who drew it, so I can thank him and show him my respect for his work.. until then we need to wait and hope..


thanks
Regards Chris
 

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@PRR, thanks for your input.

The person who owns the copyright is Nelson Pass, so Credits go to him.

Still I'm sure that I never did copy any contents of his designs.
After I send a Email with my apologies to him, he answered following.. He's a very generous Man.

"A good percentage of the circuits I thought I invented turned out to also have been done somewhere in the distant (or even recent) past. I even named one of them only to find out that 65 years before someone else had given it the same name....."

Even I own some Pass Amps in the past and still own one, I would never go an copy his work. But to build a Class A with only 3 or 4 Transistors. it will be hard to "DRAW" something really new, Borders are set very tight.. Because before someone like me could think of something in that way of building a Amplifier which is not common, there was the masters who did this already..

Recent I've read the BOOk of Douglas Self, Audio Amplifier Design Handbook, Third Edition, after I came up with that Dual Rail Single End Output MJL4281 Transistor Stage. I would anyone urge to read that book who wants to design Amplifiers, it's worth the time.
And this was actually the first time I saw a similar circuit of a single end stage with dual Rail Voltage. Check out that Screen shot of that book.

As in the past 40years I almost never used complimentary output stages but instead only Quasi Complimentary NPN output stages in all my builds, and I have done quite a few, so this was my Point of actually going to this project. Of course there are many influences from the Big guys the Famous designers. Also I have never ever made only one Amp with a single Rail voltage.. Can not remember it. I always tried to go for OTL and OCL. and this can not be done with single rail.
Of Course I read also a lot and the techniques from Nelson PASS, Rod Elliot and from some German Guy about Amplifier creation. All of them are the Masters.
I have read that Testing Mosfets sheet of Nelson Pass, and was impressed by it.. Even I dislike to use Mosfets.
That's to the Subject Own a Circuit of Copyright.

Another sad story about getting parts.
5 days ago I have ordered 2 Hammond Transformers from USA, 750VAC 30-0-30 Volts & 30-0-30 Volts for this Project as I couldn't find adequate Transformers for the project here in Swiss or in Europe. it will take up to 14 days to receive them.

Two years ago I could log into my Farnel Account and order what I had in mind. And I would get these parts next day. Today most of the Parts are out of sale or very hard to get..
So it complicates my "Work" quit a bit, as I like to get things done fast. Boxing the Amp can be done anytime, but instead of that I have to wait.. This will be my last Amp anyway, Have no space to store then amps anyway but I ask myself, what's going on with the big dealer. There is Reinelt, but he does not sell Transformers. then there is Sedlbauer, but he is run out of that model I would like to have.. and so on. sad Story
Last but not least
My apologies to all if I have offended anyone here with my writings or circuits or whatever is the belongings of someone else. Sure it was not done on purpose and I will take responsibility for my post.
Also here the screenshot of my first view of that BOOK by Douglas Shelf.
The Idea about single end Output Dual Rail was in my mind for at least 2 years already but never actually made til a few months ago.
BTW my first circuit (The one I did not invent but draw, prior to post here) I send to Nelson PASS a few months back by Email.


Regards Chris Hess
 

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PRR

Member
Joined 2003
Paid Member
> my first view of that BOOK

In the 2002 printing, on the page before, 256, there is a mis-statement (there's always slips in any large book). The resistance-loaded amplifier is at-best 8.3% efficient, not 12.5% as sometimes written. This result was published a couple places in the 1970s.

> "circuits I thought I invented turned out to also have been done somewhere in the ..past."

Also known as: "The Ancients are stealing our inventions!" This may be true in most inventing, but seems peculiarly true in Audio.

Some decades back I invented a better engine valve. And worked out why it would not be a revolutionary better valve (heat and leaks). So 30 years later a company reduced a better-compromised concept to practice and had Detroit geeks come for a demo. Then a decade after that the same Douglas Self compiled a looong page of engine valve designs. None quite duplicated "mine" but so much overlap that my "I Claim" on a patent would be a very narrow weak thing.
 
Amplifiers and more

Got you, so may Douglas Shelf made this to his path, writing about other Inventions Stuff
I'm as a Swiss Citizen look at this from the neutral position.
I read what he has to say, take what is worth and leave what I think is useless.
It is not in my or our Power to double check out everything what is in the wide and open, if someone does this at the end of the day he searched for something and has done nothing ..
Check out my Google search: Class A Amplifier single end dual Rail voltages - Google Search


Ok, that Class A single end with 4 Transistors, which I placed the Circuit I measured that one very good.. Bandwidth from 10 - 100K withing the spec of +- .5 DB is has an output Power of 14.634 Volts RMS
Feeding Rail Voltage +- 42 Volts * it's actually more than that, but Transformer can't hold the original Output voltage, and it stops at +-42.Volts.*
SO if we count both rails then we have 84 Volts, and it delivers a 14volts output RMS, before Clipping Level. This would equal about 11%. But the sound is worth a 100%


Ten years ago, I've read and looked Rod Elliot Death Of Zen. I think you know about this circuit. I looked at the circuit and decided to build that but made a very much modified version of it..

Boxed that amp, then made Pictures and send a E-mail to ROD. with all the data. What came back was: Yea, but this and that is missing, no current source control etc, etc. All things I took out of that circuit of him, because DEATH OF ZEN first Version is just V+ and GND.. and he wrote, I'm not going to build that one..

And I tried to stay away from capacitors, ONLY OCL circuits for me. Even the SPECS of his DEATH OF ZEN AMP are fantastic. Better than the one I got with dual RAIL but in the Sequence where I expected the AMP doing certain things and it does it.
This is what actually counts for me.. Sure trying to get linearity of +- 0.0000db. but in the end, this doesn't make the music..

When I found out that the Amp actually had minimal heat problems at the output - DC would change from 0 to +- 150Millivolts depending on heat. So I added a PID to keep it as close to 0Volts as possible. No need to make a new PCB just connecting two wires to and from the PID BOARD to the PCB of the AMP and it worked like a champ. Pics of the amp shows only Test Sinks with that amp and PID
The other Pics were taken in BKK Thailand in 1992, the guy in the pics is me, with age 40..The Amp which is on the 'Street' it's actually in from of my Shop from then, was the amp I sold about 40 Pieces,, all hand made by me.. Housing I ordered from Local Manufacturer in BKK , thought it was something like a US$ 100. had the same circuit but less BIAS Current that the AMP lasted..

I building amps for me only, not for sale anymore as before when we lived in Thailand - just to listen to and enjoy it.. and to have something to do when I come home in the Afternoon from my Job .. and when this project here which I'm still on, finishes then it will take a long time before all equipment at the test bench is going to see Power floating through it's circuits again.. In 2 years I'm 70. My goal is to return to our other home in northern Thailand in the Jungle - if by that time there still is jungle - and enjoying the rest of my life.. with nature and good Sound.. Still have that A-100 from Forte Audio - Product of Nelson Pass up there.. and a few of my amps..
Here a Circuit I drew in the late 70's build it many times it was changed many times..till I got at least somewhat a good amp to listen too.. it's hand drawn by me and it took almost a year to finish.. you might laugh, but this is actually like that.. that time back I had a Sanwa Analogue Multi-meter TR360 and a Soldering Iron, no Scope, Function Gen, nor any computer to calculate. The Circuit I made on a Wooden Board, drew each stage of it on thick white paper in oversize. then fixed that paper on the Wooden Board and used Nail as connection joints for the wires * PCB TRACKS* to connect. on top of the NAIL I soldered Resistors and Caps Transistors.. and so made "my designs"..
It did not leave much free space to do your own thing.. I did my own thing always, but I had to cope with things like no holidays, no fancy Cars * had an old Mazda Familia* ect. Just to follow my Hobby, building AMPs.. Even in the 1990 to 2000 I could sell them good. but our main income was a TV Repair Shop..


BTW in the pic with the Gold Plated Board on my legs, this is a Class A Line Drive, with double Sided Gold Plated PCB, then 4 outputs, two passing Output capacitors and the other two were straight out.. Output Transistors I think this is the only Line Drive with Mosfets 2SK214 as output..Delivered a 16VOlts RMS, need to check where the circuit is,, had these copied into my Database at home..

Up to date I Like to build amps.. or anything technical I can do.. not wasting my time with just breathing into the world..
Now I have many thing I would like to have in the past, Like digital Scope, Function Gen, 20 Multi-meters, Component to build at least another 10 AMPS..But now time is running against myself.. so make that last CLASS A Single END and then - Future will tell.
Thanks for your Input.. I take all input as a help..
Check out pics..

Sorry for the long post always..

Any questions just ask
 

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I know it's two week or more, and Transformers are not even on the road..
This gave me the time to make a few other things..
Getting this Class A Circuit to the Edge .. will post more about that tomorrow.. Getting some readouts as well as pics from testing..
Still fight 50 and 200 Hz of PSU but as long the Transformers are not here, it's a mere MAGIC Act to get the noise out of the PSU.. It's actually HUM..but it's low level, but with this kind of Circuit, this screams just to amplify all what comes. even the Ripple is only 50 milllivolts,, it still picks it up..
 
So finally we will see the end of the Transformer Tunnel. Transformers have been shipped in USA, and these should arrive in Switzerland in about 3 - 5 days if it takes long.. this is what the shipper tells me..

Now this makes it necessary to get the Case ready..

Think on Sunday I will post some Pictures from BOXED AMP including Cooling Unit but without Power-supply, because this will be designed newly as soon as I have the Transformers..

Guys, I just know that this amp sounds just great, and it could be done with only three Transistors.. Meaning Input Drive Output.. and all in PURE SINGLE ENDED CLASS A..
BTW working on a new LAYOUT with 6 Output Transistors to be able to hook up Loudspeakers with a resistance as low as 2 OHMS.. Just for the sake of Sound.,,
 
Transformer for Class A Single End.

Hi Gents
At last, or least today it's a day to look forward to the End of this Project..
One of the HAMMOND Toroid Transformer has come. the Second one is still outstanding but on the way from USA, this one was delivered from UK
So this is the Transformers, used for 1 Channel of that Class A.. Need to develop a real noise and Hum less Power Supply with a Soft-start for the Transformer.. Which when Power Switch is pushed on, and the transformer reaches half of Voltage will be bridged and turned on. because this will draw a huge amount of current when this AMP is going to be switched on.. And it's not only one, no Each channel will have one.. May I need to stack them because of not enough space in the case.. we will see..
On to the design board... * Multisim* Bougth it from Farnel, Price 175 USD / Piece.
 

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Price is 175 Swiss including Shipping. From Farnel. It was sent yesterday from England. this is the best Deal I could get with a two year Guarantee..

Farnel is very good in exchanging if there are Guarantee or Warranties issues.. And as it can be read on the LABEL it's manufactured in Canada... I'm willing to pay the price, as long the Quality is OK.. Not being a rich man, but invest in longtime view..

On my Next build I will consider to order from that Toroidy.pl Suppose this is Poland..
I have a Class A Line drive in the Que, and there I will need some Toroidal Transformers with high voltage.. 2 * 50 0 50 2 AMP per winding..

about same Price.. I just was on that Site.. the same Transformer is 622sloty, this equals 152 Swiss without Shipment, and I'm sure that shipment and import Tax will take another 50 Swiss, so it's more expensive.. But I have to say, the Transformers are looking nice and good

Thanks for your Input..
 
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Getting The Case Ready

Hi,

As you can see in the pics, trying to get the Amps into the case, so HEAT EXCHANGE is guaranteed as well as Noise is reduce to a minimum from Transformers Magnetic Fields..

Between the AMP section and the The transformers as well as the input Section in the Back, some Magnetic Shielding will be installed. The top, above these three NOCTUA FANS will be Airtight sealed, as well the space to the front where between the Heat-sinks and also the FANS..
The lower Fan will input Air from the BOTTOM upwards, and the HEAT SINK fans will run the Cool Air between the heat-sinks to left and right side of the AMP.

All three Fans will be controlled for SPEED and also Temperature, but only as much that the turning of the FANS can't be heard.

The Bottom fan will check the HEAT of both AMPS via heat sensors, and accordingly to this increase or decrease the airflow from below the AMPLIFIER, which of course will have a filter installed so no dirt and dust goes into the AMP. Both of the HEAT SINK fans, will turn only enough, to keep the heat-sink under 75 degrees..Celsius. As soon the heat increases to more than 100Degrees on what channel is not important, that channel will be cut off from Main Power..

Power-supply will fill into the empty space besides the Transformers. At the back of the Amplifier there the 4 200 Watts resistors will be mounted inside the Case on a HEAT Sink which is mounted on the outside..
All four of these Resistors will also be cooled by a NOCTUA FAN..

This also will be shielded with a Air-channel so Air distributes for all 4 Resistors the same.
One side becomes 2 Resistors, which can be paralleled by a switch, but only if the AMP is switched off. Also both Channels will be switched simultaneously, so that there is no difference in Sound Quality.

This amp delivers with one Emitter Resistor @15 Ohms 12.5 Watts, with @10Ohm 17Watt @8Ohm and 28 Watts.
When Paralleling the 10Ohm and 15 Ohm end Value will be 6 Ohms, which will pull about 6.5 Amps at that load..
There I'm still trying to find the Best "DEAL" for me 7.5 Ohms of RE would be just about good, but its difficult to make this Value so that no other changes at the amp need to be taken when Switching to "HIGH POWER" talking about 28 Watts.. But I will find a way.. At present time I listening with RE Value of 10Ohms @40 Volts which give a 4 Ampere Idle and a linearity 10 - 200K -0.2db and sound is just fantastic..

BTW the AMP which are seen now in the CASE are only Placeholders for getting to see how it looks like, the real amps you can see in the Picture at the end.. Number 4, 5, 6 and.. these two will be placed in that case..

Any input is welcome..
Thanks for reading..
Chris
 

Attachments

  • 5. AMP Left Channel DC output 10mv.jpg
    5. AMP Left Channel DC output 10mv.jpg
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  • 4. Real Amps.jpg
    4. Real Amps.jpg
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  • 3. from side.jpg
    3. from side.jpg
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  • 2. Positoning Transformers.jpg
    2. Positoning Transformers.jpg
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  • 1. Placement of AMPS and Cooling.jpg
    1. Placement of AMPS and Cooling.jpg
    190.9 KB · Views: 68
  • 6.Amp Right Channel - Ouptud DC 3.5mv.jpg
    6.Amp Right Channel - Ouptud DC 3.5mv.jpg
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