@Do,
Please check my previous posts regarding these changes, they've been verified both in simulation as well on a number of ExtremA amplifiers.
Please check my previous posts regarding these changes, they've been verified both in simulation as well on a number of ExtremA amplifiers.
Do you have any other way of lowering the bias even if just a little, other than emitter resistors which I already did (3x 1ohm 5 watts - 0.33 ohm). I'm at 65 celcius on the heatsink after 3 hours and stable but it is a little too hot... I'm thinking of fans but prefer not to use them.
Thanks
Do
Thanks
Do
Lower the supply voltage, but that might not be an option? If your transformer has 220 and 240V windings you could pick the latter.
Yeah the transformers are encapsulated and 120Vac primary.
I'll use fans for the time being until I find a more elegant solution.
I've got to say that the working channel sounds superb, of course no stereo imaging yet.. 😀
Do
I'll use fans for the time being until I find a more elegant solution.
I've got to say that the working channel sounds superb, of course no stereo imaging yet.. 😀
Do
@Do,
You mentioned in a previous post your PCBs were starting to wear out due to swapping out parts etc. I'd be happy to send you a new set if required. It would be a shame to abandon this project after all of the work you've put into it. Just let me know and I'll get a new set sent off to you.
You mentioned in a previous post your PCBs were starting to wear out due to swapping out parts etc. I'd be happy to send you a new set if required. It would be a shame to abandon this project after all of the work you've put into it. Just let me know and I'll get a new set sent off to you.
Hi Sander,
No need for PCB yet. I've been able to solder under the PCB (top traces were just pads) without any issues so far.
Here's the PCB with drivers mounted on the Sanken since one of the tap hole has a broken screw inside and cannot be removed. Since the drivers need to track the Sanken heat to prevent thermal runaway then this should be more than edequate but a little less elegant. You can also see the new 5watts 1% 50ppm non-inductive emitter resistors (3x 1 ohm instead of 4x 1 ohm) in order to help dissipate the Sanken emitter lead heat transfer and lower the bias. I'm at 59 watts in Class A under 8 ohms load at the moment.
Ciao!
Do
No need for PCB yet. I've been able to solder under the PCB (top traces were just pads) without any issues so far.
Here's the PCB with drivers mounted on the Sanken since one of the tap hole has a broken screw inside and cannot be removed. Since the drivers need to track the Sanken heat to prevent thermal runaway then this should be more than edequate but a little less elegant. You can also see the new 5watts 1% 50ppm non-inductive emitter resistors (3x 1 ohm instead of 4x 1 ohm) in order to help dissipate the Sanken emitter lead heat transfer and lower the bias. I'm at 59 watts in Class A under 8 ohms load at the moment.
Ciao!
Do
I take it you have someone to do that machining for you ?
(~100 bucks on your end, a set for engine short-block bolts does a whole lot more )
Attachments
Hi Jacco,
I do my own machining, sorry not a broken screw but broken tap inside... It is a 4-40 hole so it is extremely hard to remove but I still had some grip for a screw, just a little short and cannot put too much force to it. I tried a punch to break the tap pieces by pieces but it was getting too deep for the punch to be effective. Other option is to drill the tap with carbide bit but the tap has to be flush for this to work properly.
Anyways, should be all fine the way it is now?
Thanks
Do
Hi Andrew,
It is the supply for the FE of the amplifier and the PSU disconnect signal.
Ciao!
Do
Yeah, that's an option but the BD139 is so small that the plug insert might make it lose some thermal area. Don't know if it would impact it or not though.
Do
I had to have a broken tap removed by spark erosion, it cut a cylindrical hole through the tap
Stuart
Stuart
Plugged in the second channel and adjusted the offset, a little more difficult to adjust than the first channel, it drift a little but not bad.
So far it sounds fantastic! I have to cool it better than I can listen to it for a longer period of time and do a full burn in as well.
I'll keep you posted
Do
So far it sounds fantastic! I have to cool it better than I can listen to it for a longer period of time and do a full burn in as well.
I'll keep you posted
Do
I have found a thermal pad product far superior to Kerathern Kerafol Red according to the specs here
http://industrial.panasonic.com/lecs/www-data/pdf/AYA0000/AYA0000CE2.pdf
Keratherm Kerarol Red 0.25mm is 6.5 W/mK but this Panasonic PGS Sheet is anywhere between 700 and 1950 W/mK (2 to 5 times as high as copper) according to their spec sheet. Anyone tried those? The price is really good so I was thinking of using this for the Sanken.
Do
http://industrial.panasonic.com/lecs/www-data/pdf/AYA0000/AYA0000CE2.pdf
Keratherm Kerarol Red 0.25mm is 6.5 W/mK but this Panasonic PGS Sheet is anywhere between 700 and 1950 W/mK (2 to 5 times as high as copper) according to their spec sheet. Anyone tried those? The price is really good so I was thinking of using this for the Sanken.
Do
Look at the ones with 1kV insulation in the spec. You're looking at the graphite only version.
Hopefully I'm reading this properly...
The only thing that worries me are the ones with low thermal resistance are rated 100 celcius max... and the thermal resistance is not specified, just "low thermal resistance" is written...
The only thing that worries me are the ones with low thermal resistance are rated 100 celcius max... and the thermal resistance is not specified, just "low thermal resistance" is written...
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