Not Your Mommy's GC

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Inside

Here is the interior:

Top board in the middle is the power supply and buffer.

Bottom board on the right is for controlling the voltages across every LED. Believe it or not the blue ones are set below spec and still light up.

Amp module is around the heat sinks. Two LM3886TF chips.
PCB, I don't need no stinking PCB for my module!

More details on my web site here:

http://home.san.rr.com/john1in2/DIY/GC_1/



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Underside of Amp Module

I used parts (black gate caps and holco/riken resistors) from Peter Daniel's inverting configuration posted here a long time ago, back when inverting was the rage. Now noninverting is the rage, but looks like buffering is acceptable too. Whew.

Kimber speaker wire and pure silver wire used in the signal path. Power supply caps are Panasonic FC.

You can see from the inside pic (above) that I added 4 filter capacitors to the diode bridge, the DC just had too much ripple using the 1,000 uF caps per rail (4 rails). Had to do it, now bass is much better and HF is clear and articulate.

All diodes are high speed soft recovery, MUR1520 in the main supply (8 heatsinked unnecessarily) and MUR820 in the low noise supply.

These sinks in operation get only slightly warm. If cranking max output into a 5 ohm resistor they get much to hot to touch. If cranking max output into speakers, they get very hot, but you can still touch them. So they seem adaquate, but I am going to drill some vents into the top cover to let them cool via convection easier (holes are already in the bottom of the case for this purpose).
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Back Panel

Here is the back panel.

One switch selects RCA or XLR inputs, it grounds the positive terminal of the differential input should RCA be selected. That way the balanced input passes through no switches.

The other switch turns off the Aux (low noise) power supply so that external batteries (another project in the works) can be used. You see the miniplug under the speaker binding posts for this input.

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Low Noise Power Supply

Here is bottom of the low noise power supply board. It uses Linear Technologies LT1964 and LT1962 surface mount ultra low noise voltage regulators mounted on bottom of board. You see that they are small, but they seem to be working well. I get some hash on the highest setting on my scope, backgrounds are silent, things are good!

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Resistor board

This board sets the LED voltages, each LED has its own trimpot, and I used diodes and base resistors for saftey. Even if you trim to 0 ohms you are still ok, and even if you reverse polarity, you won't blow the LEDs.

This board is fitted for the long cermet trimpots as well as the short stubbier type, just happens that I used all the long ones here, but for BOSOZ, I need two of these with different types of trimpots.

One reason I started this DIY stuff is that I wanted to make my own PCBs, and here in this project we have two. Very interesting even though they can be easily hardwired. I did it for the learning experience. I used Cadsoft Eagle PCB layout, and emailed my designs to www.custompcb.com.

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Front panel

The front panel was designed by me and made by www.frontpanelexpress.com. I used their free software and just emailed my design, they made it of 3mm thick anodized aluminum and it cost around $30. I have a much more complicated one for the BOSOZ which was around $60.

The lettering is etched and then filled with ink by front panel express (I have black and blue ink fill on this faceplate). Black is shown below.

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The Sound

I have had this up and running for about 2 weeks, and used it without the differential buffer for another 2 weeks. The amp has very tight bass, and smooth and articulated highs. It does not sound weak at all. And yes, its stable into my Snell E's with 25 feet of speaker wire, as well as into my other speakers and into 5 ohm 100 W resistors. There is no hum at the tweeters at normal levels.

I very much enjoy the sound. Even though I have a ARC tube amp (very old), a BAT VK-200 and a Pass Aleph 3, I get a certain sense of DIY enjoyment out of this, and don't feel like I have sacrificed very much at all. I'm using a huge 500 VA transformer and the amp sounds effortless at all reasonable volume levels. It good to know the design, nothing in there to roll off the high frequencies, which I like, and it has really good extension on the top end.

As I said, this is literally my 1st real DIY project, so please give me all your comments, I really would like to hear from you here or by email (check out my web page). I am an EE by training but went in another direction when I graduated from school 15 years ago, and I didn't know a "via" from a "header" when I started this. Learned about both during the project, bought a soldering iron and a scope. I did this for fun, not to save money, this was not inexpensive.

I hope to have measurements up and posted in 2 or 3 months. I have to work on this stuff on the sly if you know what I mean. This took about 10 months of a little here a little there (in parallel with my BOSOZ, 4 months away from being finished), and the wife says it looks like its from the '70s! Hey, the case is from the '80s get it right!
 
Nice work lgreen! ;)

I was always lead to believe that LED's were noisy items best kept away from hi-fi, even to the point of removing them from the mains distribution strips.

Now, if anybody can say if they are noisy, it should be you as I have never seen so many LED's in one project!

I don't think that I will ask you to disconnect them all though to see if it makes any difference - we may never hear from you again. ;)
 
ah, finally I see them...
considering the number and the brightness of the LEDs you won't need that much energy for your bulbs, so I guess it's ok...
not to speak about the signal path which is not really optimized, but nice front tho(except the LEDs thicket)

BTW, what kind of wire did you use?
 
LEDs...Oh you noticed?

Too many LEDs? I'm sorry for finishing this project first, my BOSOZ is going to have at least twice as many LEDs (however they will be able to be turned off via front panel switches...switches with LEDs on them of course). I would hate to give you guys the wrong impression that the 8 used on the front panel here are adaquate. My apologies!

I can actually disable these LEDs quite easily, I just unplug either of the 2 receptacles from the 9 pin headers on the LED board, takes about 1 second and it can easily be plugged back in. Doing this, it does not appear that the LEDs actually add noise. So don't ask me to remove the LEDs, I like them! Ok maybe I should have used the smaller size ....hey, this was my 1st project, still learning.

Moreover, if you look at the LED board, each LED is after a diode, which prevents electrical noise created in the LED from going backwards to the power supply that it is powered from. This is good for isolation, but if you are thinking that LEDs create noise that is radiated into the air, well nothing I can do about that except locate them remotely from the circuit, and most are very distant.

To respond to the question about the type of wire, signal wire is DH labs 54927 or 63005 silver cable; speaker cable (the blue cable) is Kimber 51981 4TC (from www.partsconnexion.com).

Here is my 1st go at the BOSOZ panel with openings for illuminated switches, LEDs . This is designed to match, assuming that one is able to see both stacked on each other through the blinding blue and yellowish light. Hmmm.... I wonder if I should start looking for welding masks to protect visitors?
 

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Nuuk said:
I was always lead to believe that LED's were noisy items best kept away from hi-fi, even to the point of removing them from the mains distribution strips.

That is complete rubbish. LEDs are often used as voltage reference in hifi regulated supplies and CCS. While not as silent as some references, they are obviously very quiet. Besides, INA13X and LM3886 have tremendous PSRR.
 
That is complete rubbish. LEDs are often used as voltage reference in hifi regulated supplies and CCS. While not as silent as some references, they are obviously very quiet.

Yes, I have to admit to having some discrete regulator circuits here that use LED's and they do work well.

This looks like one of those rumours that has been around so long, people like me believe it. At least, my take on it was to leave out LED's if I could as they certainly wouldn't improve the sound, and if there was some negative affect, it was one less thing to worry about.

I did use a couple of blue LED's to light up the tubes in my VBIGC and that also sounds just fine. ;)
 
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