Nagys,
I tend to agree with Wahab your protection diodes are the wrong way around, as attached they don't protect anything. I believe Pass labs and Hafler use a similar scheme, the small signal diode in series with the Zener is added for temperature compensation (which Pass does not use),
Attached is the Hafler scheme
If I am wrong please explain to me why? If not Alex has to flip his diode orientation on his PCB layout.......
Jam
I tend to agree with Wahab your protection diodes are the wrong way around, as attached they don't protect anything. I believe Pass labs and Hafler use a similar scheme, the small signal diode in series with the Zener is added for temperature compensation (which Pass does not use),
Attached is the Hafler scheme
If I am wrong please explain to me why? If not Alex has to flip his diode orientation on his PCB layout.......
Jam
Attachments
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PCB layout
Hello,
Interesting design and thanks for bringing this to the forum,
Just went through the PCB layout, since there is 60vac line on it and its ground shares with rest of the ground, this must be corrected. The resistors used with it should be well placed together and must be of the best quality.
The layout is good but can be improved just to be on the safer side and not give any chance for oscillation to break free.
Regards,
Smathias
Hello,
Interesting design and thanks for bringing this to the forum,
Just went through the PCB layout, since there is 60vac line on it and its ground shares with rest of the ground, this must be corrected. The resistors used with it should be well placed together and must be of the best quality.
The layout is good but can be improved just to be on the safer side and not give any chance for oscillation to break free.
Regards,
Smathias
jam - My diodes/Zeners are connected in exactly the same way as in the schematic you just posted. If Alex has shown them incorrectly in one of his PCBs he will correct it as soon as he reads this. Again, please look at the schematic I posted on the first page. They are correct, unless I'm blind.
smathias - You are correct regarding the ground. I'm sure Alex will make a quick fix when he reads this.
smathias - You are correct regarding the ground. I'm sure Alex will make a quick fix when he reads this.
tinitus,
The amp appears to be a of an early Goldmund design, I have taken one of these apart years ago. The topology is is copied from I believe the Hitachi databook at that time.
They added a few improvements to the differential pair but forgot th address the current mirror. The Goldmund version was prone to oscillation with some cables. Perreaux also produced several amps with the same topology.
Jam
The amp appears to be a of an early Goldmund design, I have taken one of these apart years ago. The topology is is copied from I believe the Hitachi databook at that time.
They added a few improvements to the differential pair but forgot th address the current mirror. The Goldmund version was prone to oscillation with some cables. Perreaux also produced several amps with the same topology.
Jam
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tinitus - Ok fair enough. This amplifier has been in production for many years from the late 80s to late 90s. Thousands of units have been sold. You ready guys for the secret...? It's from a Swiss company Goldmund!!!! Now this should be exciting enough for even the most prestigious of audiophiles. This is the schematic for a Goldmund Mimesis 9.2 mono block, it's also identical (the only difference is 2 pairs of MOSFETS versus 3 pairs) to Goldmund Mimesis 3, Goldmund Mimesis 6, Goldmund Mimesis 9, Goldmund Mimesis 8.5, etc.
I have personally owned different versions of this amp and have made 2 of my own. I have since sold these. The circuitboard I etched myself was not as nice as Alex's, but never the less, the amp sounded phenomenal. This is the very best sounding amplifier ever made, IMO.
I have personally owned different versions of this amp and have made 2 of my own. I have since sold these. The circuitboard I etched myself was not as nice as Alex's, but never the less, the amp sounded phenomenal. This is the very best sounding amplifier ever made, IMO.
Nagys,
..................I don't think so, ask yourself what the purpose of the Zener is ignoring the small signal diode for the moment and you will see what I mean, your diodes are the wrong way around........either that or am I going blind.
Jam
..................I don't think so, ask yourself what the purpose of the Zener is ignoring the small signal diode for the moment and you will see what I mean, your diodes are the wrong way around........either that or am I going blind.
Jam
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jam - You're right. I took a closer look at your Hafler's schematic and they are indeed different. But the schematic I posted on the first page is identical to Goldmund's original schematic. No exactly sure yet why they're connected the way they are, but that's how they are in the original schematic.
I have to conclude that Goldmund had an error in their schematics.
I also believe that part of the Goldmund secret formula was their mechanical grounding scheme and layout. A good amp when used correctly but can be improved quite a bit by addressing the current mirror on the second differential. The amp was always on the verge of instabilitry and increasing the value of the gate stopper resistors sometimes helped.
Jam
I also believe that part of the Goldmund secret formula was their mechanical grounding scheme and layout. A good amp when used correctly but can be improved quite a bit by addressing the current mirror on the second differential. The amp was always on the verge of instabilitry and increasing the value of the gate stopper resistors sometimes helped.
Jam
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I was going to say just because you're diodes are in that way doesn't mean it's correct, maybe you've just never had to use the protection circuit there fore it hasn't had the opportunity to fail yet.
I do like the way this amp is working, I don't see any reason it couldn't be used with an extra pair of output devices or how this would harm anything at all? I think once files are posted I will etch this my self and build it but I wouldn't be a good tester as it won't be done for quite a while.
I do like the way this amp is working, I don't see any reason it couldn't be used with an extra pair of output devices or how this would harm anything at all? I think once files are posted I will etch this my self and build it but I wouldn't be a good tester as it won't be done for quite a while.
Picture of Goldmund Amp can help for clone pcb.
