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When DIY goes retail.

musicforcities

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IMG_0854.jpeg

Is it just me or does the wiring on this sunfire 2x300 look really terrible, both in general quality/construction and the soldering? As far as I know, it has never been serviced. It started smoking a couple months ago when some el caps on one channel blew.

The center is a star ground: what looks like an 18awg solid wire soldered to tabs at main caps negative terminals, along with a transformer tap, a wire to pcb, and negative speaker terminals, with another 20awg wire going from it to another solder tab at chassis ground. The solder looks very dry and the connections dodgy at best.

I was given this amp a long time ago…just sort of amazingly diy construction quality
 

Somafunk

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Looks legit :facepalm:, if it’s from a £300 Chinese built e-bike
 
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musicforcities

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image.jpg


Here are the speaker terminals. No wonder the multichannel version amir tested had so much noise. The negative speaker terminals are tied to the rca grounds with a ceramic cap as well as the chassis ground , routing round the giant transformer.

The giant resistor is for one set of speaker terminals in order to give one that, ahem, sweet tube sound. Bonkers.
 

alex-z

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That looks like someone soldered it with no temp control, using their toes, in the dark. 100% would just replace the whole thing with a Crown XLS1502.
 

Sokel

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Did some searching to see other units cause I could not believe this is a unit coming like this out of the factory but nope,it is,all I saw is similar.

And nope,DIY stuff are far better these days,if one was presenting a DIY amp made like this in the known forums he would be subject to tar and feathers :)
 

restorer-john

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I was given this amp a long time ago…

And that's the problem. You don't know it's history or what was done to it. I cannot believe the mess of monster cable on the filter caps is original to any commercially sold product, regardless of where it was made.

I've seen some horror-shows before, so it is somewhat possible I guess.
 

SSS

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View attachment 321204
Is it just me or does the wiring on this sunfire 2x300 look really terrible, both in general quality/construction and the soldering? As far as I know, it has never been serviced. It started smoking a couple months ago when some el caps on one channel blew.

The center is a star ground: what looks like an 18awg solid wire soldered to tabs at main caps negative terminals, along with a transformer tap, a wire to pcb, and negative speaker terminals, with another 20awg wire going from it to another solder tab at chassis ground. The solder looks very dry and the connections dodgy at best.

I was given this amp a long time ago…just sort of amazingly diy construction quality
If it electrically works the look is not necessary to be nice. Recently I repaired a car battery charger with microcontroller fireing thyristors. Due to unleaded solder the joints look dry and not what I am used when done with leaded solder. So dry looking solder joints are normal today. But I agree that the amp here was not assembled in a fine way. My DIY wireing looks better but I have spent much more time than a production entity can do.
 
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JSmith

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I cannot believe the mess of monster cable on the filter caps is original to any commercially sold product, regardless of where it was made.
Well... assuming this is not the exact same unit, it appears those orange monster cables are there;

1698311238104.png
1698311284206.png


Here is an article too by Bob Carver about Sunfire amps in 1995;


I thought this part was interesting... ;
Voicing

At this point in the design, the Sunfire is an amplifier that can deliver high current as well as voltage, delivering both simultaneously for tremendous output power, and runs cold. However, the design is not yet complete. The amplifier needs to he voiced. Voicing of an amplifier is the last 5% in its design (potentially the most time consuming) and is where the art of amplifier design is truly based. It is accomplished by altering the values of resistors and capacitors in various parts of the circuit, and then listening to the effect that a particular value has. When I voice an amplifier, I first use a female vocalist so that she can be accurately located in an acoustic area between the speakers, and in such a way that a believable halo of space surrounds her in three dimensions. Also, I fine tune the amp so that her voice is soft, musical, lyrical, and has a great deal of believability. (Not too much to ask, right!?)

After I finish the female voicing, I work on the male voice using baritones to get the chestiness that is a prominent feature here. When that part of the amplifier voicing is completed, I go to the symphony. I have in my head a template of what a symphony orchestra should sound like. I close my eyes and fit the sound of that symphony orchestra in my head, to the sound that my amplifier is making through the loudspeakers. (Baked fresh Salmon and a nice glass of Chenin Blanc, followed by the Seattle Symphony under the stars. Ahhh ... that's got it.) In the case of the Sunfire, after finishing the human voices, I found that the symphony orchestra locked in, and I had only minor adjustments to make, sort of like getting the flesh tones correct on a color television receiver, once that is done, all the other colors often lock in with very little further effort.
:facepalm:


JSmith
 

restorer-john

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I was given this amp a long time ago…

And that's the problem. You don't know it's history or what was done to it. I cannot believe the mess of monster cable on the filter caps is original to any commercially sold product, regardless of where it was made.

I've seen some horror-shows before, so it is somewhat possible I guess.
Well... assuming this is not the exact same unit, it appears those orange monster cables are there;

View attachment 321289 View attachment 321290

Here is an article too by Bob Carver about Sunfire amps in 1995;


I thought this part was interesting... ;

:facepalm:


JSmith

OMG. Are you serious?? Someone really lost the plot there didn't they?

:facepalm::facepalm: <----Never given a double.
 

fpitas

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My reaction is I do better work. And I've had techs run over to the bench and grab stuff away from me so they could do it right! :D
 

ErVikingo

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The internal Monster Cable sounds legit. It was a thing; for example the cables inside my IRS speakers is all Monster branded. Lots of marketing genius back then for Monster.

I have a couple of signature subs (Sunfire) and the plate amps are IMHO a very clean design and execution. None of what I see on the pics of this amp.

I remember buying a couple of used VTL amps with consecutive serial numbers. One had “a smell”. I opened them up and it was obvious someone had gone to town on it.

Sent them both to service and tech was in horror.
 
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musicforcities

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And that's the problem. You don't know it's history or what was done to it. I cannot believe the mess of monster cable on the filter caps is original to any commercially sold product, regardless of where it was made.

I've seen some horror-shows before, so it is somewhat possible I guess.


OMG. Are you serious?? Someone really lost the plot there didn't they?

:facepalm::facepalm: <----Never given a double.
Well given by my father. Who had it from new. So I known providence.
 
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musicforcities

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musicforcities

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A different unit example. From a review when these first came out. Yes that is a speaker negative wire draping over the corner of the bridge rectifier pcb. Doesn’t need to, usually it runs on the bottom of the case between the transformer and the rectifiers and just touches the side of one of the recifiers


IMG_0857.jpeg
 

fpitas

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Good grief
 
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musicforcities

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They are very large caps at very high voltage. The bridge rectifiers are very large as well, 8-10 amps each I believe. The amp will suck about as much ac current from the wall that you can give it and that it wants. Part of how it works: a “tracking downconverter”(basically another discrete 2 channel amp inside the chassis) tracks the signal to continuously vary the main amps rail voltage so it is around 6 volts above whatever power is needed. So as I understand it it is a class AB amp with a linear power supply that varies. It’s pretty ingenious in a way and the amp can produce hundreds of watts when needed at 8 to 2 ohms but only uses what it needs at any moment. It runs cool all the time. And I mean cool. No heat sinks, the transistors are mounted directly to the very thick bottom chassis (which is around 3mm of aluminum).
 
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