bit of an update....
preliminary build write up can be found here:
Vitalstates- Amplifiers
spent all day yesterday listening, having set(I thought) bias at arounf 1.6 Amps(750mv). Very lively...immediately struck me that all the percussion was fantastically punctuated.....after about 6 hours I'd had enough, but thought this might be the goto amp in the future....but it's early days.
spent all day today addressing the bias... what a pain! it will not stay still.
measured it after turn on and thence every hour for 8 hours...what a pain...it will not stay still. I had to adjust a couple of times when it went to 800mv.....did I mention what a pain!
will publish some figures later, but in general it wandered from 625mv to 800mv.....
I've been using sp400 pads, cut from a sheet, but I know Nelson favours and advises mica and gloop, and I'm wondering if this might have something to do with the variations. I've measured the temp difference between the fet and the sink and it seems to be about 5 degrees or so.
any body else finding this behaviour?
preliminary build write up can be found here:
Vitalstates- Amplifiers
spent all day yesterday listening, having set(I thought) bias at arounf 1.6 Amps(750mv). Very lively...immediately struck me that all the percussion was fantastically punctuated.....after about 6 hours I'd had enough, but thought this might be the goto amp in the future....but it's early days.
spent all day today addressing the bias... what a pain! it will not stay still.
measured it after turn on and thence every hour for 8 hours...what a pain...it will not stay still. I had to adjust a couple of times when it went to 800mv.....did I mention what a pain!
will publish some figures later, but in general it wandered from 625mv to 800mv.....
I've been using sp400 pads, cut from a sheet, but I know Nelson favours and advises mica and gloop, and I'm wondering if this might have something to do with the variations. I've measured the temp difference between the fet and the sink and it seems to be about 5 degrees or so.
any body else finding this behaviour?
It looks like the heat goes to the heat sink through the chassis. How good is
the thermal connection between the two where the transistors are mounted?
😎
the thermal connection between the two where the transistors are mounted?
😎
I posted a similar if not so detailed question a while back. The other beta builders said that they were not experiencing any problems with bias drift. I will check mine again at the weekend.
Hi Marra
do you use pads or mica for thermal insulation?
I only ask because I've just re-measaured the difference in temp between the fets and the sink immediately adjacent, and the difference maybe more than I mentioned yesterday, e.g 10 to 20 degrees.
I need to do more testing because I imagine there needs to be a long time between adjustment and measurement because under any circumstances the sink will need time to catch up with the fet.
do you use pads or mica for thermal insulation?
I only ask because I've just re-measaured the difference in temp between the fets and the sink immediately adjacent, and the difference maybe more than I mentioned yesterday, e.g 10 to 20 degrees.
I need to do more testing because I imagine there needs to be a long time between adjustment and measurement because under any circumstances the sink will need time to catch up with the fet.
Mica and a small amount of goop.
I'll check the temp difference between sink and mosfet when I recheck bias and offset.
I'll check the temp difference between sink and mosfet when I recheck bias and offset.
mica and goooooo is preferable to that silicone thingie
change that and you'll have stable heat transfer
change that and you'll have stable heat transfer
thanks for the feedback chaps....
I've ordered some mica from ebay and I'm checking out the goo. Anybody got any recommendations as I've read to beware of some cpu goo that is not electrically insulating, and all the stuff on ebay seems to be for cpus.
This is frustrating as I've been using sp400 pads for loads of jobs since the F2, and never had any problems....c'est la vie..onward!
Ed
I've ordered some mica from ebay and I'm checking out the goo. Anybody got any recommendations as I've read to beware of some cpu goo that is not electrically insulating, and all the stuff on ebay seems to be for cpus.
This is frustrating as I've been using sp400 pads for loads of jobs since the F2, and never had any problems....c'est la vie..onward!
Ed
Just reiterating what Nelson said. I would cut an opening in the chassis walls so that the fets could be attached directly to the heatsink base.
sorry guys I'm struggling to understand here......
the FETS are attached directly to the heat sinks....
the heat sinks are the walls, the chassis is only the base and back of the case.
The sides of the case are conrad 300x150x40 heat sinks.
the FETS are attached directly to the heat sinks....
the heat sinks are the walls, the chassis is only the base and back of the case.
The sides of the case are conrad 300x150x40 heat sinks.
People see fets mounted to silver colored metal and say.. hey.. get those off there and goop them directly to the black colored heatsink.
well , not built exactly , because I dismantled it later (as numerous Papamps) ....... so - tried ,for sure
it works fine
it works fine
