Aragon 47k Schematics?

I'll get the cover off the power supply part of the board and take more pictures. I don't understand why they'd put big coupling caps down close to the audio when the rest of the power supply seems to be "hidden" under the RF cover... (But looking at other Aragon products- specifically preamplifiers, they seem to love using these exact same parts in all of them. And only two.)

But supposedly a "world beater" of a preamp so I want to give it every chance for success. I understand the IPS is a significant upgrade ("Better" outboard transformer) but I don't see why a DIY outboard transformer couldn't be made better than the IPS, or, is it even necessary to be better than the IPS. Maybe improving the components under the cover inside would do more good...

Still no schematic found; stand by for additional photos. If I get the board completely out of the box, I'll get photos of the bottom as well. From there we can draw up a schematic pretty easily I think. This is a good project for someone like me who's more mechanical than electrical.

I added four images I could find on the net from the "IPS" although there may be an "Ingot" in there too. So there was the standard, the IPS (Improved Power Supply) and the Ingot, which was the final version.

Can anyone glean anything from these?

Then I learned about someone offering a drop in replacement board for IPS that surpasses the Ingot. I sent an email, but the contact info was from seven years ago, so who knows what will happen...
 

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Sorry for the delay. I was having trouble logging in.

Re the signal coupling capacitors, I’m not an electrical engineer. Coupling for me had always been on the power supply. Knowing they are on the signal, they should benefit from an upgrade.

Meanwhile I heard back from the designer from seven years ago that made the upgraded power supply. Unfortunately he does not have any, or boards, as demand was too low to do a second board run. But he’s going to see if he can dig something else up.

He did provide a schematic for the small rectangular power supply, which appears to have come direct from Mondial. I will attempt to attach it.
 

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Hi Jim. I started some sketches of what the schematic might be. It was Mexican food and Margaritas for dinner tonight so I need to do them over. Might be a day or so before I get back to it. There was a recent thread that talked about the difference between coupling and power supply caps. I’ll try to find it tomorrow for you.

Phil
 
Hi Jim --
Here are some sketches of what the power supplies in the preamp might look like. The first is the "IPS". It's similar to what you posted except for an additional cap on the output and a resistor that goes -- somewhere. The next pic is the second power supply which is to the left (in post #10) of the yellow film caps. And finally a block diagram of the RIAA amplifier showing the input and output coupling caps. Probably not useful but it was a fun exercise.

edit -- "IPS" diagram does not show transformer or bridge rectifier.
 

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I am going to assume they were designed by the same person. Perhaps the Ingot was the “good” design and then they “watered it down” to control cost. Price of admission is lower; with a clear upgrade path already designed in. Good business model.

So I need a +24/-24 power supply. Excellent stability and low ripple. I’m betting there are some sweet designs floating amongst the other info here... I need to get the cover off the rest of the power supply in the main box to see what’s there, so poor decisions are not made with the external bit. I did find it odd that the bridge rectifier seems to be in the main box, but the transformer is external. Wouldn’t the “noise” be reduced if DC entered the cabinet rather than AC? Maybe with the voltage reduced to 24 rather than 115 the tendency to transmit is reduced? Even if that is true, it still seems like “low hanging fruit” to bring clean DC into the main box.
 
So, I found an old Audiogon for sale post by "kchamber" from Texas. He was selling upgraded power supplies, and goes into detail about what he did. Here is the text from his old listing:

"The Ingot MkII power supply board is a hand-built upgraded power supply board that was designed to easily drop into the triangular steel housing of either the Aragon IPS or the Ingot external power supplies. The Ingot MkII power supply board is to date the only engineered upgrade solution for Mondials older Aragon line of components. Before describing the Ingot MkII I think that it would be appropriate to identify the different external power supplies which Mondial provided with their electronics and elaborate on the specs of each unit.

Each of the following power supplies provides +/- 24 vdc to the Aragon component that it is connected to.

• The IDLK19 - Shipped with all early Mondial electronics. It was a small black rectangular plastic package with the Aragon logo on the outside. It featured a chassis mount 24 VA transformer, a voltage rectification circuit consisting of 4 discrete 1 amp diodes for the rectification circuit and a total of 4,380 µF of internal capacitance. The power connector to the component is a 3 pin XLR.

• The IPS - This unit debuted somewhere in the late 80's to early 90's and was housed in the familiar triangular steel housing. It featured a PCB mounted 30 VA transformer, a single 1.5 amp bridge rectifier and a +/- 24 vdc regulator with a total of 9,420 µF of internal capacitance. The power connector to the component is a 3 pin XLR.

• The Ingot - This unit was built specifically for the Aurum preamplifier. It is identical in every way to the previously mentioned IPS except that it has been beefed up with more internal capacitance. In the Ingot a pair of 10,000 uF capacitors are installed after the bridge rectifier, in comparison the standard IPS had a pair of 3,300 uF capacitors in this same location. Due to this difference the total storage capacitance in the Ingot is 22,820 µF. The power connector to the component was also changed to a 4 pin XLR. The reason for the change to the 4 pin XLR was to prevent users from accidentally plugging the power connector into one of the Ingot's balanced preamp outputs. Aside from the difference in capacitance and XLR pin out there is no other difference from this supply and the IPS.

• The Ingot MkII – This board uses a PCB mounted 56 VA transformer, 2 amp discrete MUR series ultrafast diodes and discrete bridge rectifiers for each voltage rail, for a total of 8 discrete rectifier diodes. A total of 35,200 uF of internal storage capacitance. Heatsinking for the regulators, LED diagnostic LED’s for the voltage rails and input/output terminals to eliminate the need for soldering.

In building the new Ingot MkII my goal was to exceed the specs of ALL the previously available power supplies that Mondial produced. I also wanted to add some features that were absent in the original power supplies. All components used in the construction of the Ingot MkII are brand new and sourced from major US distributors, i.e. Mouser, Digikey, Allied Elec., etc. This is important because buying cheaper parts from small or unknown distributors increases the chances for low quality Chinese knockoff parts to be purchased, not a good thing! I also wanted this upgrade to be easy to install, so that anyone with a couple of decent screwdrivers and a pair of wire strippers could perform the swap, no soldering required. To do this I used a set of screw down clamping connectors for both the incoming AC power and the DC output voltage. So you are probably wondering about the parts used in the Ingot MkII power supply? You will find that throughout this power supply there are nothing but high quality parts all the way down to the professionally built FR-4 fiberglass board and the Cardas Quad Eutectic 4% silver solder that was used to assemble the supply.

So let's start with the transformer, the original IPS and Ingot power supplies used a 30 VA rated transformer capable of using either 120 VAC or 230 VAC 50/60 Hz to operate. The Ingot MkII in contrast is using an upgraded 56 VA rated transformer (an 86% increase in power output capability). This transformer is also capable of both 120 VAC or 230 VAC 50/60 Hz input power just like the original, but unlike the original there is no soldering required to make the conversion for AC voltage.

The Ingot Mk II uses MUR series ultrafast recovery 2 amp discrete diodes in the rectification circuit. Not only does it use discrete diodes, but it also uses discrete bridges for each voltage rail. The original power supply Mondial produced only had a single bridge to feed both voltage rails and used standard speed diodes.

Green LED’s have also been added to indicate when the +V & -V rails are on, the original power supplies gave no internal indication of whether they were working properly.

For the regulation circuitry the original Mondial power supplies used a 2 watt base resistor in conjunction with a zener diode for voltage regulation. Both of those components were then mounted in direct physical contact with the board. In the Ingot MkII the base resistor was upgraded to a 3 watt unit and both the high power resistors and zener control diodes were mounted approximately 1/8” off of the board to allow for better convective cooling. This means that not only will they live a longer life they will also not heat the board to the point that the board begins to discolor over time due to overheating.

The regulation transistors received heatsinks which provide about a 300% improvement in cooling over the bare transistors that came in the original power supplies. In addition to this, protection diodes have been installed across the regulation transistors.

Next I want to talk about the capacitors used in the Ingot MkII. A lot of time was spent in trying to find the best components here. Nichicon electrolytic capacitors were used throughout the Ingot MkII because they are very reliable and they sound good. Directly after the rectification circuit the 4 tall Nichicons provide 13,200 uF per rail, or 26,400 uF total to filter the incoming AC and provide clean DC with minimal ripple to the regulator. Some of you are wondering why I used 4 capacitors and did not stick with two larger units to mimic the looks of the original factory power supplies. The answer to this is simple, it is better to use two medium sized electrolytics than one large electrolytic in a circuit because just about every measured parameter for that pair of capacitors will be better than if a single capacitor was installed in their place, ESR, ripple current handling, Impedance, etc. all are improved. The reason most manufacturers do not use multiple electrolytic caps in their power supplies is plain and simple, it costs more money and takes up more space.

The capacitors after the regulator circuit are all audio grade Nichicon’s and continue with the same rational, more is better. You will notice that 4 electrolytic capacitors per rail are used [8 total] on the output side of the regulation circuit. Once again the rational here was that four 1000 uF Nichicon Audio grade electrolytics would provide a much higher performance filtering bank than the original three 470 uF caps used in both the IPS and Ingot power supplies. In actuality only 6 of the 8 caps are used on the output of the regulator. Two of the eight capacitors are used for the transistor base filtering in the Ingot MkII and in the original IPS/Ingot supplies two of the six small caps were used for this same function.

On the Ingot MkII’s regulated DC rails a pair of Wima MKP2 metallized polypropylene caps are installed as bypasses. None of the original power supplies Mondial produced came with bypass capacitors of any type in them. Every Ingot MkII I hand build has been fully bench tested and then burnt-in/auditioned powering an Aragon component. It will work on any of the older Aragon equipment that used the external power supply, i.e. D2A, D2A MkII, 24K, 24k SP, 47K, 18K, 18K Mk II, & Aurum. PLEASE NOTE - THE XLR CABLE IS NOT INCLUDED WITH THIS ITEM. IT IS SHOWN IN THE LISTING TO GIVE A SIZE REFERENCE. I DO OFFER REPLACEMENT CABLE ASSEMBLY OPTIONS, LET ME KNOW IF YOU NEED ONE AND I WILL GIVE YOU A PRICE FOR IT. This power supply upgrade board includes a detailed 12 page installation document (soft copy word document) that includes pictures to illustrate the steps. Insured USPS priority mail shipping will be paid by the buyer and will cost $17 inside the continental US. I will pay the paypal fees. I have sold a number of these through Ebay and word of mouth. I go by the same user ID on Ebay by the way if you'd like to check my feedback there. As far as warranty, if it EVER breaks email me, send it back and I'll test/repair it. I have been building Aragon replacement power supplies for about 4 years now and have had nothing but happy customers to date with any of my work."

Now the attached photo I believe is the power supply board he was selling. When I clicked that photo to enlarge and get a better look, it took me to the old listing. I think between the photo, known schematics and his text above, we could build these easily enough.
 

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