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PCB order for Goldmun clone

Hi there. I´ve checked ≈3/4 of the PCB and it looks OK. Maybe not a big deal but I´d switch two GNDs : the one for the 33k resistor (BC182B EB+B) and the one for the 1uF/160V (on the bottom of the "OP amp module" in the original hand made scheme) - not sure how much current will be drawn in this GND branch (where the 33k is connected and where the 1uF should be, imho). Another thing is the zobel - I´d put it (the 10R/3W) to the same point where the speaker cold (-) will be connected. Anyway, all this could be done without any modification to the current PCB.
 
Hi,

Modified the protection pcb so as to accomodate both relays as shown in Nagys data sheet for it. Not as 'handsome' as Alex's, that is for sure. Same price.


vladimir,
I am so dumn that I cannot exactly understand what you had in your post.

Zobel : Are you saying that the left side of the 3w 10ohm is not connect to the 3 10nf from the outputs on the left. But instead it is connect to the speaker -, which to my best understanding means the power GND also. Maybe it is a good idea to sketch a drawing how the boards are connected to the outside world?


For the other one, I am totally lost. Think it is possible to throw in some sketch to clear it up for me, the dumb?
 
I've got an idea, let's go one digit up :
2N5566
$7.20 each, $6.25/pc for +10 ?

Oh No, let's go one digit down then :
2N5564 => Radios For Sale
1 Dollah each, 6 for 5 buckeroos ?

Makes any sense ?
(didn't even have to check the Geekbay)

Please accept my apologies-- the 2N5564s are currently out of stock. I have
no idea when or whether I can obtain replacements.

73--

Brad AA1IP

Not able to buy...
 
Hi Nagys,

I am having some serious problem with the main board now. I cannot use alex's latest drawings because in some part of it, there is some problem with the polygons drawn (or maybe even others) which keeps it from generating the bottom layer. Somewhere in his past version, I had picked up one to work on to eliminate the blockades and able to generate the different layers. Then I redraw the parts that I had taken away (to clear away the problems), a painful lot of work actually.

Since then I had made a few changes and so does alex. When alex makes small changes, I can still incorporate that into mine and follow his tracks. Although it was no fun to do that because I am using a tool that I don't know too well.

It is growing more difficult as more changes are introduced. So there might be a few things that you might be able to help me out by answering these :


1. Can you show me a way to make my own footprint?
2. It seems that when I move or copy a footprint, there is no coordinate shown for it. Can that coordinate be display ? For even coordinate of those corners of a track? If that can be done, it can make a lot of my work easier.
3. For the version you send me, there seems to be not much of a help from the "help" manual. But you told me that it is a full version already.

I know how odd it is to ask question (or learning to) about my own tools at this almost final stage. But I would really appreciate if you or any other guys who can point me some directions on the question that I asked. Tks

I really don't want to quit after all this work.
 
Bigpanda - I truly wish that I could help you use the Sprint Layout, but unfortunately I have never used it myself. Maybe Alex can help out :) I will also ask in the main forum.

The only changes that the board needed was a different location for the rail fuses. I think the board is well designed and there's no need for any further changes. We can keep making little changes forever, so as long as the circuit is good, lets keep the board as it is. So we can all start building this amp :)
 
Transistor Equivalents

This should be very interesting for all potential builders of the Goldmund Mimesis 9.2 clone. This information is straight from the official Goldmund service manuals and schematics.

One of the obsolete (but still abundantly available) transistors that Goldmund Mimesis 9.2 uses is the Motorola BSS71/BSS74 (T11 and T12 in Alex's schematic, please see attachment). In addition, the Motorola MPSA93/MPSA43 (T7, T8, T9, and T10) are also obsolete. Wouldn't it be nice to change all of these transistors with the current production of MPSA92/MPSA42? This change is not only possible, but very easy to implement. No changes are necessary to the PCB board's layout, so potential builders can build it any way they choose.

Bellow, on the right is the original part and on the left is the new replacement part that needs to be substituted in order to make this change. Again, this is all as per Goldmund.

(NOTE: For the protection circuit, MPSA93/MPSA43 can be replaced with MPSA92/MPSA42 without any further changes.)

T7 (MPSA93) = MPSA92
T8 (MPSA93) = MPSA92
T9 (MPSA43) = MPSA42
T10 (MPSA43) = MPSA42
T11 (BSS71) = MPSA42
T12 (BSS74) = MPSA92
C8 (100uF) = 150uF
C11 (100uF) = 150uF
C1 (47pF) = 100pF
C3 (4.7pF) = 8.2pF
C5 (4.7pF) = 8.2pF
C6 (4.7pF) = Omitted
R10 (1K) = 1K5
R22 (30K) and R19 (30K) = Replace with a single 10K
R20 (270) = 330

That's it!
 

Attachments

  • Goldmund Mimesis 9.2 Schematic.pdf
    47.9 KB · Views: 693
Changing the Amplifiers Output Power

This info should also be interesting to all potential builders. As is, the Goldmund Mimesis 9.2 uses 3 pairs of MOSFETS (Hitachi 2SK134/2SJ49, please see the attached schematic from Alex) and has a power output rating of 250 watts (2-8 ohms). And a maximum output of 400 watts at 3 ohms.

The output MOSFETS/rails are fed with +/-80VDC. And the input stage is fed by 60VAC. The transformer needed would be 400 watts (maximum amplifier's power) X 1.414 (headroom) = 566 watts. So... Potential builders can use a 600VA toroidal transformer per channel, or two separate 300VA toroidal transformers. One to feed the -80VDC rail and another to feed the +80VDC rail. In either case, the transformer needed would be a toroidal with dual secondary windings of 120VAC in series, or 60VAC in parallel. The 60VAC before the bridge should be taken to feed the input stage and the voltage after the bridge will feed the +/- 80VDC rails. The voltage after the bridge is calculated as follows: 60 X 1.414 = +/- 85VDC, perfect for the rails. A transformer with dual secondary windings of 110VAC in series and 55VAC in parallel will also work just fine. The input stage will be fed 55VAC and the output stage's rails will be fed by (55 X 1.414 = +/- 78VDC) +/- 78VDC. Which again is perfect.

This is a powerful amplifier that requires fairly large transformers and heatsinks. Wouldn't it be nice to make this into a 100 watt (2-8 ohms) per channel, amplifier? Maximum of 200 watts at 3 ohms? It's extremely easy.

First, the rail voltages will have to be +/-60VDC and the input stage will have to be fed by 40VAC. This all works out perfectly. The transformer needed will be as follows: 200 watts (maximum power) X 1.414 (headroom) = 283 watts. So a 300VA transformer will be needed per channel, or if one choses to feed the + and the - rails with separate transformers, then each will have to be 150VA. A toroidal transformer should be used with dual secondary windings of 80VAC in series, or 40VAC in parallel. The input stage will be fed by taking the 40VAC before the bridge and the +/- rails will be fed with the voltage after the bridge, 40 X 1.414 = +/- 57VDC. Close enough to +/- 60VDC.

The remaining changes are extremely simple: Omit one pair of MOSFETS (2SK134/2SJ49) and omit R38 (6R8, 2W) and R39 (6R8, 2W). That's it! You now have a 100 watt per channel amplifier and can use a significantly smaller transformer and heatsink :)

NOTE:

The original Hitachi metal can MOSFEST, 2SK134/2SJ49 are obsolete and nearly impossible to find. The PCB will be designed to use a variety of new and in production equivalent plastic MOSFETS. They're all readily available from electronic distributors. Here's the list:

Renesas 2SK1058/2SJ162
Exicon ECX10N16/ECX10P16
Exicon ECX10N20/ECX10P20
Magnatec BUZ900P/BUZ905P
Magnatec BUZ901P/BUZ906P
Alfet ALF08N16V/ALF08P16V
Alfet ALF08N20V/ALF08P20V

When using the plastic MOSFETS, the BIAS resistor needs to be changed in the amplifier, otherwise the plastic MOSFETS could overheat. R23 (330) needs to be replaced with a 220 ohm resistor. This is the only necessary change to the schematic.

I hope this information helps everyone. And rest assured, it all comes directly from Goldmund's service manuals and schematics.

Here are some transformer recommendations, I strongly prefer Hammond and Plitron:

Hammond 182L60 (300VA, 2X60VAC) = $95
Hammond 182P60 (626VA, 2X60VAC) = $135
Plitron 057026201 (160VA, 2X40VAC) = $80
Plitron 077026201 (300VA, 2X40VAC) = $94
Plitron 07742201 (300VA, 2X55VAC) = $94
Plitron 077052201 (300VA, 2X60VAC) = $94
Plitron 097042201 (625VA, 2X55VAC) = $143
Plitron 097052201 (625VA, 2X60VAC) = $143
 
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Hi Alex,

Just want to make sure one thing : Can you generate gerber files for your work (I mean with your copy of Sprint.) Because if you can do that, I don't have to do what I am doing now : making changes to my copy according to what you have change.

Last time when you send me what you have, I wasn't able to generate the gerber files for fabrication and without the gebers, your work cannot become real pcbs (or there may be other file formats that can go to the fab. house but I don't know). What I have done was I tried to dele some part of your drawings (a small area) and tried to generate the gerbers. Although the area I remove is small, I cannot find the exact cause of the problem. All I know is that if I redraw that small area until I can generate the gerbers. Bit by bit I redo the areas in doubt and finally got a layout (with, I don't record how many changes I have done). After I had an exact copy of yours (or almost ) but in my version (which can generate gerbers ), I tried to make the changes on my copy in syn. with your changes. Je, that is no fun at all.

So what I am saying is that if you are still in helping out in perfecting the board, do you think you can do this first : check and see if your layout can generate gerbers so your work can be use directly by the fab. house. If it cannot, find out where the mines are and clear them out first. Here are some possible errors that can fail you in generating the gerbers : I found that several polygons that you have in your layout having duplicate corners seems to have cause the trouble. I think you don't have to take that much time as I did to find our the faults.

If you can help with this, I will only do the job of bookkeeping the order, not pulling together the layout.



And Nagys,
tks for the alternative transistors, that should make life a little easier. If the present version of seperate boards is working fine, do we really have to go to a consolidated board? It may cause more.
 
Bigpanda - Having both circuits on the same board is a lot better, IMO. The output does not have to go from the main board to the protection circuit board and then to the speaker terminals. This way the output Zobel and series inductor are all closer to the speaker terminals. It would just look nicer and perform better in my opinion.
 
BigPanda, with a ground plane you want to minimize EM fields parallel to the plane, so as not to introduce circulating EMI currents which interfere with currents flowing through the plane. Consider the orientation of the output Zobel. The magnetic field is parallel to the plane. Wouldn't it be better to stand the coil vertically?

- keantoken
 
Hi keantoken,

As far as i can see, if you think that by standing the coil upright, it can do better, (pls I am not too good at these, and if you have an opinion just say it out), you can implement it that way, providing that you construct the coil to be able to do so and the air space clearence is enough for that. Actually I am not the one laying the board, Alex_mm is. It's just because the work he passed to me cannot generate gerbers (at least with my version of Sprint, at my location, and use by a dumb like me) and so I dare to touch his work to make it OK for gerber generation. If not, I would rather keep the original design.
 
Of course I could do it myself and tell noone, but then who would benefit?

For a very fast amplifier, I think this matters, because any high currents flowing through the coil will flow through the ground plane and through the decoupling caps, possibly complicating the stability with extra resonances and interactions.

I only had a brief look through the beginning of this thread, and I thought it was you who made the PCB design you showed. I'm sorry.

- keantoken