Audiophiles - This is what your Mega Dollar Cables Connect to inside your amps

[xrunner]

So my brother asked me to find out why his expensive Bob Carver Sunfire Woofer makes humming noise when the other equipment is turned off. To make a long story short I think it's a ground loop issue - ordered a ground loop isolator to try out.

But I thought I'd post some pics of the inside for all the audiophiles out there. You need to know what your Mega-Expensive oxygen depleted Super Duper cables are connecting to inside your amps.

Just wire. Normal everyday small basic boring plain little wires which go to plain little ordinary circuit board traces. See attached pics.

Have a nice day. 

[Zero999]

Lot's of lovely noisy carbon film resistors there to add depth and warmth to the sound stage.

[SeanB]

Turn the mains plug around in the socket and see if this helps.

[xrunner]

Lot's of lovely noisy carbon film resistors there to add depth and warmth to the sound stage.

At least the phono connector is gold plated. 

Turn the mains plug around in the socket and see if this helps.

Yea I heard that suggestion on another site. I've done some research on this woofer, and hum is a common problem. Some people claim it needs caps replaced but I tested a lot of them and couldn't find anything bad. I can't easily reverse the mains plug because it's a three prong.

Also there is no schematic available and the input from the mains / P.S. is something I've not seen before. It has two big caps and one is connected directly to neutral before the bridge rectifier. That thing has 165V on it when the amp is unplugged and it's a dangerous little beast.

Hope fully the ground loop isolated will make it better.

Edit -

[wraper]

This subwoofer seems to be a full of bullshit in its claims. 2700W RMS LOL. You cannot even draw such power from the US outlet even if considering it's amplifier is 100% efficient. And that's with 11"x11"x11" size and 43 lb weight  . My 300W speakers (seem to be more or less close to the truth, though I think it's a bit inflated) weight 48kg = 105 lb each  . And there is no amp inside too to add the weight.
Edit:
Posted this before seing second picture. 2700W hell yeah 

[Kevman]

I'm confused- that transformer only looks big enough to run the preamp/filter stages, and that bridge rectifier doesn't look connected to it... Is the main amplifier running directly off rectified mains?

[xrunner]

I'm confused- that transformer only looks big enough to run the preamp/filter stages, and that bridge rectifier doesn't look connected to it... Is the main amplifier running directly off rectified mains?

Hell if I know - I don't have the schematic but I might try to reverse engineer one. I don't know what they are doing, but I think it's part of the humming issue. Let me see if I can muster enough energy to draw part of it it. 

[wraper]

I'm confused- that transformer only looks big enough to run the preamp/filter stages, and that bridge rectifier doesn't look connected to it... Is the main amplifier running directly off rectified mains?

Yeah 1500uF 200V capacitors seem suspicious.

[Zero999]

It looks like it's a switched mode power supply. There should be a high frequency ferrite transformer but it's not visible on the photos.

The resistor, near where the yellow/white twisted pair is connected to the board, has overheated.

[wraper]

Isn't this an optocoupler? ...in the middle of preamp.

[Zero999]

Isn't this an optocoupler? ...in the middle of preamp.

Yes, it looks like an opto-coupler but you'll never know for sure without the part number.

What's on the other side of the board?

[Kjelt]

But I thought I'd post some pics of the inside for all the audiophiles out there. You need to know what your Mega-Expensive oxygen depleted Super Duper cables are connecting to inside your amps.

I don,t think audiophiles will have such subwoofers 
Try Velodyne or JBL. I have seen a lot of expensive amps but none had bare wire.
Still for the mains power cables I can only agree bigtime. But then I found out long time ago that snob audiophiles are selectively deaf.

[wraper]

Searched for the patent number. Looks like they are doing something crazy.

[Marco]

Bob Carver is probably one of the most famous anti-audiophiles.

Is that one of his subwoover drivers with a tracking switched power supply? Audiophiles only use space heaters.

[xrunner]

It looks like it's a switched mode power supply. There should be a high frequency ferrite transformer but it's not visible on the photos.

No it's not that kind of supply.

The resistor, near where the yellow/white twisted pair is connected to the board, has overheated.

No, it's fine that's just a shadow.

I'm drawing out the P.S. input and it's nothing I've ever seen. Check out the bridge - see that wire shorting across it? That's the two AC input pins they are shorting out - on purpose.  What does that give you - two sets of rectifier diodes in parallel? That's what it looks like on paper.

This thing is weird!

[PeterFW]

The first picture allready told everything you need to know without opening the speaker
Those frequency, level and phase adjustment knobs look like potentiometers.
Nothing wrong with that but the chance that the speaker is set up properly is near zero.

[calexanian]

Its a B.S. chinese plate amp. I know the guys who were making the stuff for carver. Carver went into receivership and the Chinese vendor now owns the name because they were owed the most. I actually was at a meeting with those guys a couple years ago and the new Chinese owners were here in the U.S. talking to all of the U.S. vendors for old Bob trying to figure out what to do with the dead rat of a company that had been dumped in their laps! Long and short of it now is you have Mid level AV products being sold under the Carver name. BTW if anyone wants to buy that name/company, let me know. I can broker a deal. That also goes for a number of other companies in the quickly evaporating audio market.

[macboy]

Bob Carver is probably one of the most famous anti-audiophiles.

Is that one of his subwoover drivers with a tracking switched power supply? Audiophiles only use space heaters.

Yes it is.
As for the 2700 Watt claim, well, ... it depends on how you want to look at it. The driver has a certain impedance, and the amp is capable of continuously driving a voltage into that driver that will calculate out to 2700 W if you use good old ohm's law. But it isn't that simple. His design uses a high back-EMF driver; basically the speaker in this sub acts like a motor that is not "stalled" which is in stark contrast to other speakers, which generally look like a stalled motor. This speaker produces a high back-EMF which cancels out a significant portion of the applied voltage, and therefore greatly reduces the actual power consumption and greatly improving efficiency. In other words, the "apparent power" through the speaker might be 2700W, but most of that is reactive power, not real power. The spec sheet BS numbers use the audio industries nonsensical way of calculating power (P=V²/R), but it is in line with how everyone else does it. He (Bob Carver) is very forward about the fact that the 2700 W number is both 'real' and sort of nonsense. Read the old white papers about the design of the amplifier and the driver and cabinet. This little sub went impossibly loud and low for its small 1 cu.ft. size two decades ago. This subwoofer re-defined the physics of how to produce bass by being simultaneously loud, deep, small, and efficient - a previously impossible combination. Clearly, I am impressed by the technology. I have nothing to say about how it sounds, which is a rather important trait in audio gear.

p.s. Too bad about the new ownership of the company as mentioned above.
p.p.s. This is a mkII which is very old, so clearly not made by the company's new Chinese overlords - not a "B.S. Chinese plate amp".

[SeanB]

I think that transformer is actually being used to couple the audio to the power stage, which looks like it is powered direct from rectified mains. Must be a small SMPS hidden at the back of the main board, where the bunch of caps are located.

Probably the poor earth to the front panel is the main cause of the hum, aluminium oxide, especially that which is heavily anodised, is a pretty good insulator.

[Marco]

AFAICS the Chinese owners still just sell the old designs at boutique prices.

Or maybe the dealers just paid to keep the website up to sell old stock.

[xrunner]

p.p.s. This is a mkII which is very old, so clearly not made by the company's new Chinese overlords - not a "B.S. Chinese plate amp".

Right, this was bought back in 1997 or so. Remember, it's operating as intended designed. I'm only trying to stop the hum when it's in standby (it never goes off).

So if you are interested, I drew up a schematic of the PS input, as it stands, and double checked it. This is what it shows. Anyone want to explain what's going on be my guest. CB means circuit board, I'm not going any further than that it would take way too much time.

[SeanB]

If it is wired like that then the only cure for the hum is a massive isolation transformer, so that the mains hum is not coupled through the driver circuitry.

I know Carver made some amplifiers that were seemingly designed to use the entire output of a large semiconductor fab for a week per unit, but this.........

[German_EE]

That short circuit across the input of the bridge rectifier has me puzzled. The circuit is almost like the 110V voltage doubler at the input of a PC supply, but not quite. I would be VERY reluctant to work on any part of that circuit without an isolation transformer.

[Marco]

So two half wave rectifiers going to the different capacitors to cheaply get split power from mains, what's so wrong with that?

PS. how is the isolated input amplifier coupled into the non isolated power amplifier though? I don't see a second transformer, linear optocoupler?

[Galenbo]

This subwoofer... bullshit in its claims. 2700W RMS LOL. You cannot even draw such power from the US outlet ...And that's with 11"x11"x11" size and

In thermodynamics, there is a direct relation between power, surface area and surface temperature (with some assumptions to be made)
Who is fluent in this? I would have to search for the formulas...

With that numbers, the surface temperature must be high enough to cook an egg on it.

[dannyf]

There is an oscillator, a low-pass filter, a comparator, a dc-dc converter, a feedback loop, etc.

The amplifier is a variable output power supply.

[IanB]

In thermodynamics, there is a direct relation between power, surface area and surface temperature (with some assumptions to be made)
Who is fluent in this? I would have to search for the formulas...

With that numbers, the surface temperature must be high enough to cook an egg on it.

Actually, that would not come under thermodynamics, it would come under heat transfer. But thermodynamics does tell us that the continuous average power output must be less than or equal to the continuous average power input from the mains.

[M4trix]

The topic should be --> Audiophoolers - This is what your Mega Dollar Cables Connect to inside your amps

 

[Red Squirrel]

Maybe it's audio grade solder. 

Ok I was joking, but apparently this actually exists:

http://rankoaudio.com/AudioGradeSolder/241.htm 

[xrunner]

So two half wave rectifiers going to the different capacitors to cheaply get split power from mains, what's so wrong with that?

PS. how is the isolated input amplifier coupled into the non isolated power amplifier though? I don't see a second transformer, linear optocoupler?

Redrawn attached showing the bridge converted to two diodes and yes you can see two half wave circuits. Also some things require various taps of lower AC voltages ...

[cosmicray]

Right, this was bought back in 1997 or so. Remember, it's operating as intended designed. I'm only trying to stop the hum when it's in standby (it never goes off).

Any chance the caps (at ~18 years) have reached their retirement age ?

[wraper]

I just wonder about the inrush current of this thing. 2x of 1500uF capacitors and no current limiting at all (like NTC or power resistor + relay). Doesn't it trip circuit breakers by the chance   .

[xrunner]

I just wonder about the inrush current of this thing. 2x of 1500uF capacitors and no current limiting at all (like NTC or power resistor + relay). Doesn't it trip circuit breakers by the chance   .

It does make a large "thump" when plugged in, and the plug at the wall sparks a bit LOL. 

One of the large caps retains 165V for days, and it's dangerous to be in there until it's discharged. I discharge it with a large resistor, I think I just grabbed a 1.47k power resistor.

Any chance the caps (at ~18 years) have reached their retirement age ?

I don't think so cosmicray. I checked both large caps and they were perfectly fine. I checked some others at random and found no problems.

This thing is a Bob Carver Sunfire MKII "true" (whatever that means) subwoofer. It has known humming problems if you research it. There are various solutions out there, and my brother wanted me to check out the capacitor issues, but like I said, it has no issues with caps. The other known issue is the notorious ground loop issue. This is what I think it is.

At his house he claimed it hummed badly, but at my house it's not nearly so bad. The ground loops are different. I ordered an el cheapo ground loop isolator and we'll see what that does for it. It connects to the audio input and stops an ohmic path around the ground loop (whatever weird path it takes in your particular house and equipment) 

[amyk]

That is exactly like the voltage-doubler circuit used in half-bridge PC PSUs, giving a +/-170V supply. The transformer is there to power the lower-voltage circuits.

Not surprised that it will hum, when the reservoir caps get old and lose capacitance.  They're driving the speaker directly from mains voltage.

[dannyf]

Carver is the guy who thumped the golden ear types before thumping the golden ear types was cool.

He showed that tube amps and solid state amps, when in their respective performance envelops, are indistinguishable, audio-wise.

[xrunner]

Might as well post this. It's the massive magnet inside the thing. I'm not even kidding, this thing weighs a TON. It hurts my back to move it into the living room.

[Galenbo]

Actually, that would not come under thermodynamics, it would come under heat transfer. But ...

In our school all this was treated in the course "thermodynamics", things like Turbines, Black body, convection, Isochoric process, heat exchanger rendement, cavity, turbulency,...

[xrunner]

Funny discovery. I had brought the woofer back into the living room and hooked it up to my system. It was there all morning and it wasn't humming. I went in to microwave lunch and then by chance checked the woofer - it was humming a lot louder than it ever had. Didn't think too much about it but all of a sudden it stopped humming ... just as the microwave stopped. I started the microwave again and sure enough it started humming, and it quit when the oven stopped.

Was it a ground loop or RF? I started the oven and while the woofer was humming, I pulled the audio input - it stopped humming even though the oven was still running.

It's a ground loop issue.

[SeanB]

Ground lop is easy to fix cheaply as you are not actually using the capacitors to transfer a high fidelity ( foley sub noise only) signal, so just isolate the 2 input sockets ( I assume you feed it from a dedicated sub output) from the alloy chassis with some sleeving and plastic washers, and then couple the input and input ground using some 47uF 400v capacitors on the 4 leads. That should get rid of the hum.

[Marco]

It's a ground loop issue.

You might need an active ground loop isolator by the way, or you're going to lose some low end.

[free_electron]

It looks like it's a switched mode power supply. There should be a high frequency ferrite transformer but it's not visible on the photos.

The resistor, near where the yellow/white twisted pair is connected to the board, has overheated.

nope. they rectify incoming 110 volt and store it on two 200 volt caps.. that is the main supply for the amp....

[Zero999]

It looks like it's a switched mode power supply. There should be a high frequency ferrite transformer but it's not visible on the photos.

The resistor, near where the yellow/white twisted pair is connected to the board, has overheated.

nope. they rectify incoming 110 volt and store it on two 200 volt caps.. that is the main supply for the amp....

I get that now but how are the inputs isolated from the PSU? The signal connections need to be isolated from the mains, otherwise bad things can happen.

[SeanB]

Probably they use optoisolators run in linear mode, at the frequency range a sub handles 10% or more distortion, and a bandwidth of 3Hz to 60Hz will be easy for even the poorest opto to handle.

[thm_w]

I'm really confused by the image of the RCA inputs.

They are using a single earth wire from the mains lead, connected only to one RCA jack (saved some pennies there).
I'll assume that the insulated RCA jacks are not actually insulated and make contact with the black anodized plate. Otherwise if you plugged in the wrong jack it would have no ground reference.

Wouldn't this lead to a huge ground loop?

[xrunner]

They are using a single earth wire from the mains lead, connected only to one RCA jack (saved some pennies there).
I'll assume that the insulated RCA jacks are not actually insulated and make contact with the black anodized plate. Otherwise if you plugged in the wrong jack it would have no ground reference.

Wouldn't this lead to a huge ground loop?

They are all grounded together, I just checked it because of your post.

When you touch the black anodized finish with the probe leads (but not hard enough to scratch it) it will not even read into the megohms range - it's an open circuit as far as my DMM is concerned. But if you dig in a bit with the probe lead, it will go into the nearly zero ohms range. So since the RCA jacks are tightened pretty good, they have penetrated the anodizing well enough to make a good ground.

[NiHaoMike]

How is the input board grounded to the chassis? Maybe try adding a direct connection with copper wire as aluminum is infamous for making bad connections. Also try shorting the inputs to ground at the connectors themselves to see if it might be a floating input picking up noise.

[Someone]

Funny discovery. I had brought the woofer back into the living room and hooked it up to my system. It was there all morning and it wasn't humming. I went in to microwave lunch and then by chance checked the woofer - it was humming a lot louder than it ever had. Didn't think too much about it but all of a sudden it stopped humming ... just as the microwave stopped. I started the microwave again and sure enough it started humming, and it quit when the oven stopped.

Was it a ground loop or RF? I started the oven and while the woofer was humming, I pulled the audio input - it stopped humming even though the oven was still running.

It's a ground loop issue.

Is the neutral isolated from the earth somewhere in the subwoofer? If it isn't it's created the mother of all earth loops. Neutral will flap around as other loads are turned on/off, such as the microwave. If it is isolated then the rejection of the isolating is poor and you'll need to look at how to increase the common mode rejection of the isolation.

[xrunner]

Is the neutral isolated from the earth somewhere in the subwoofer? If it isn't it's created the mother of all earth loops. Neutral will flap around as other loads are turned on/off, such as the microwave. If it is isolated then the rejection of the isolating is poor and you'll need to look at how to increase the common mode rejection of the isolation.

I dunno. Look at the schematic I drew up in an earlier post. Neutral goes off to the circuit board after that I don't know. Also, one terminal of the speaker is connected directly to neutral.

[xrunner]

Ha - I just thought of a new business opportunity. Just advertise to audiophools to install Mega De-oxygenated wire (or whatever catch-word turns them on) on the inside of the amp from the terminals to the circuitry. Just show them pics like I took, where their Mega cables transfer to little cheap wires, and they'll freak out. 


Oh crap - the shipping costs would be a little on the high side though.

[wagon]

Ha - I just thought of a new business opportunity. Just advertise to audiophools to install Mega De-oxygenated wire (or whatever catch-word turns them on) on the inside of the amp from the terminals to the circuitry. Just show them pics like I took, where their Mega cables transfer to little cheap wires, and they'll freak out. 


Oh crap - the shipping costs would be a little on the high side though.

Can't see them caring about the shipping cost when they're paying thousands for their space-heating amplifiers.

[cosmicray]

Oh crap - the shipping costs would be a little on the high side though.

Promote it as a "white gloves" service, where you show up on site and do the upgrade there. 

[macboy]

Ha - I just thought of a new business opportunity. Just advertise to audiophools to install Mega De-oxygenated wire (or whatever catch-word turns them on) on the inside of the amp from the terminals to the circuitry. Just show them pics like I took, where their Mega cables transfer to little cheap wires, and they'll freak out. 


Oh crap - the shipping costs would be a little on the high side though.

Can't see them caring about the shipping cost when they're paying thousands for their space-heating amplifiers.

This, sadly, is not a new idea. People do such upgrades, installing boutique RCA jacks wired to the PCB with teflon insulated solid silver wire, and custom oxygen-free cryogenically treated power cords. Sheeple will spend more on these upgrades than they do on the gear in the first place.

[dannyf]

Can't see them caring about the shipping cost when they're paying thousands for their space-heating amplifiers.

A friend of ours is in the business of helping mid-aged women pregnant - those tend to be empty nesters from (extremely) well-off families. The doctors compete on good service, results, and surprisingly, VERY high fees. You want to be known as the most expensive clinic in town, not the other way around.

Same here.

[xwarp]

A friend of mine who brings me "vintage" receivers to service brought me one of those subs.

I normally don't work on anything I can't find a schematic for, but did check a few of the caps on the boards and foud more than half a dozen with extremely high esr.

Gave it back to him and told him to send that POS to some company in Phoenix, AZ that reworks them. It wasn't worth my time with the problems it had.

[xrunner]

A friend of mine who brings me "vintage" receivers to service brought me one of those subs.

I normally don't work on anything I can't find a schematic for, but did check a few of the caps on the boards and foud more than half a dozen with extremely high esr.

Well this one is fixed. 

The El Cheapo ground loop isolator from Ebay did the trick. I'm calling brother tomorrow and he can come get it.

Thanks for all the responses. 

[LektroiD]

Just because something is expensive, it doesn't make it good. There's loads of new overpriced brands popping up which are simply white van junk.

As for audio cables, I run a recording studio with 96 analogue channels at mixdown. Cables often get stood on, pulled, or run over by the castor wheels of a swivel chair. They also run alongside mains and data cables so shielding is a must. It's a no brainer to buy industry standard double shielded Van Damme cable and Neutrik jacks for a solid connection, avoid crosstalk and be durable enough to withstand heavy studio usage. I certainly wouldn't dream of hooking up the audio element of my studio with bell wire!

That said, there are some companies (like the manufacturer of the dodgy subwoofer in the OP) who thrive on selling cheap junk at high prices to gullible folk. Overpriced power cables is a common one.

[timofonic]

Are there some good schematics to make cheap & DIY true audiophile hardware without snake oil nor magic? I wonder, because I'm newbie and want to practice building my home equipment, and try to get some money for spending it in student stuff (test equipment, private tutor, public transport, English academy and saving for ERASMUS or working overseas).

[wiss]

http://www.douglas-self.com/
and
http://www.cordellaudio.com/

[LektroiD]

Are there some good schematics to make cheap & DIY true audiophile hardware without snake oil nor magic? I wonder, because I'm newbie and want to practice building my home equipment, and try to get some money for spending it in student stuff (test equipment, private tutor, public transport, English academy and saving for ERASMUS or working overseas).

Not always cheap, as many good audio designs will use expensive hi precision rail to rail opamps, etc. although you can usually drop in cheaper TL07x opamps. Since I build for audio I always use metal film resistors too. Polystyrene film and silver mica capacitors can soon make a project expensive too.

For studio gear, there's a load of Neve schematics here. They make some of the best designed stuff in the industry.
 
but if you're after straight audio separates, amplifiers, etc. just google for schematics and manufacturer of your choice. Some older service manuals even have the PCB trace screens so you can etch your own single sided boards.

[dannyf]

cheaper TL07x opamps.

If you peek inside a studio mixers, etc., you will find lots of lm324 in them, and maybe a few TL0xx chips on the high end units.

Think about how little your "precious" audio-grade opamps can do to sound that has gone through those LM324s,

[Kevman]

Are there some good schematics to make cheap & DIY true audiophile hardware without snake oil nor magic? I wonder, because I'm newbie and want to practice building my home equipment, and try to get some money for spending it in student stuff (test equipment, private tutor, public transport, English academy and saving for ERASMUS or working overseas).

http://sound.westhost.com/

Some of his information is slightly... Redacted, though- reserved for those who buy his PCBs.

[Yansi]

cheaper TL07x opamps.

If you peek inside a studio mixers, etc., you will find lots of lm324 in them, and maybe a few TL0xx chips on the high end units.

Think about how little your "precious" audio-grade opamps can do to sound that has gone through those LM324s,

What professional mixing consoles do use LM324 in their signal path? Give direct examples.

Even Uli Behringer does not use this shit in his cheap consoles.  The only thing where 324s were seen to be present, was the lo-freq part of 31 band GEQ from the same company. There is the right spot to use these.

[Zero999]

cheaper TL07x opamps.

If you peek inside a studio mixers, etc., you will find lots of lm324 in them, and maybe a few TL0xx chips on the high end units.

Think about how little your "precious" audio-grade opamps can do to sound that has gone through those LM324s,

What professional mixing consoles do use LM324 in their signal path? Give direct examples.

Even Uli Behringer does not use this shit in his cheap consoles.  The only thing where 324s were seen to be present, was the lo-freq part of 31 band GEQ from the same company. There is the right spot to use these.

I doubted that too. The LM324 really doesn't have enough bandwidth for audio use.

[Yansi]

Bandwidth is not the only issue, also the slew rate matters. Considering proffesional audio equipment using relatively high signal levels, faster opamps are needed to keep signal distortion low.  Especially the 324 is quite slow.

Cheap mixing consoles (like that ones from Behringer) use NJM4560 and 4580. "Standard" level proffesional mixing consoles like Allen & Heath use mostly TL072 and NE5532 on the more critical places. Maybe some really crap quality consoles might use st. like JRC4558, but never seen them in any mixing console. Even the chinese crap like Omnitronic use NE5532. (but if they are original parts one can only guess)

Your doubt was right, only dannyf again pushing his number of posts, in every thread he can.

[Zero999]

Yes, due to the poor slew rate, the LM324 only has a full power bandwidth of 5kHz.
http://www.ti.com/lit/ds/symlink/lm124-n.pdf

[Yansi]

Heh, have you noticed the layout on page 23? 

[TimFox]

Are there some good schematics to make cheap & DIY true audiophile hardware without snake oil nor magic? I wonder, because I'm newbie and want to practice building my home equipment, and try to get some money for spending it in student stuff (test equipment, private tutor, public transport, English academy and saving for ERASMUS or working overseas).

Try this book (apparently a new edition is almost out):

High-Power Audio Amplifier Construction Manual Paperback – May 1 1999
by G. Randy Slone (Author)

ISBN: 0071341196

The author has strong opinions in favor of bipolar transistors, but he discusses real technical details of the difference between bipolars and mosfets.   He also includes practical full schematics for each type of device.   He is too dismissive of vacuum tubes, in my opinion, but he is reacting against some of the recent extreme tube opinions, especially single-ended triodes.

[dannyf]

but he discusses real technical details of the difference between bipolars and mosfets.

The mosfets he was talking about in that book are not your run-off-the-mill mosfets you often see today.

[Yansi]

Maybe this one will also help: Bob Cordell, Designing Audio Power Amplifiers

//sorry if some have already mentioned it

[suicidaleggroll]

Are there some good schematics to make cheap & DIY true audiophile hardware without snake oil nor magic? I wonder, because I'm newbie and want to practice building my home equipment, and try to get some money for spending it in student stuff (test equipment, private tutor, public transport, English academy and saving for ERASMUS or working overseas).

Check out www.amb.org

Full schematics, board layout, BOM, with the blank PCBs and some of the hard-to-find or matched components available from his store to simplify the build process.

Most of the designs are for headphones, but there are some bigger amps for real speakers (the parts are not cheap though).

[Gringo]

Does Marc Vincent have a new name now?