Banned
Joined 2002
Dougie085 said:Well was mostly just a joke. But something of the sorts. Solidstate is going to take place of everything eventually. Movies, Music even video games will move to solid state media. I'll only get digital media if its in HQ though which is very high quality MP3 rips (not your normal crap you get off itunes) or a lossless codec.
But my comment above was for fun and games
Every mp3 is compressed.
Heat sinks and transformer for F4
I was wanting to use these heat sinks for my F4 amps. I know they are a little small and I was wandering if it would be better to lower Bias or only use 4 Mos fets instead of 6? I also have a choice of transformers 200VA at 20 volts or 300VA at 18v. If I go with these heat sinks and the 200VA transformer I can make it into I fairly compact case
I was wanting to use these heat sinks for my F4 amps. I know they are a little small and I was wandering if it would be better to lower Bias or only use 4 Mos fets instead of 6? I also have a choice of transformers 200VA at 20 volts or 300VA at 18v. If I go with these heat sinks and the 200VA transformer I can make it into I fairly compact case
Attachments
Re: Heat sinks and transformer for F4
Hi
This is a matter of choice. 18V seccondaries dissipates less then the 20V (11%). What could be more important is that the maximum voltage of one the jfets is 25V. Chosing the supply voltage higher than 25V, in my view, is better not done.
18V secondaries will give 24 - 25V supply.
20V will give 28 - 29V.
If you go for 4 pets, you can have a higher bias, sure. Stick to 6 fets and you have a higher thermal reserve. I'm not sure what I would prefer.
Higher bias defenately will sound better.
wirewiggler said:
Hi
This is a matter of choice. 18V seccondaries dissipates less then the 20V (11%). What could be more important is that the maximum voltage of one the jfets is 25V. Chosing the supply voltage higher than 25V, in my view, is better not done.
18V secondaries will give 24 - 25V supply.
20V will give 28 - 29V.
If you go for 4 pets, you can have a higher bias, sure. Stick to 6 fets and you have a higher thermal reserve. I'm not sure what I would prefer.
Higher bias defenately will sound better.
Banned
Joined 2002
Re: Heat sinks and transformer for F4
heat sink WAY to small.
Don't we all learn ? Well i learn every day
wirewiggler said:
heat sink WAY to small.
Variac said:Congrats Jason,
The tough battle make victory that much sweeter - or some such trite saying. But one does learn from those horrible moments when things don't work...
Don't we all learn ? Well i learn every day
Banned
Joined 2002
Ok, here's a data point: back when I was planning my F4 I told Nelson that I was thinking of making balanced F4 channels with just two devices per channel. (ie a total of four for balanced amp channel) He told me to make the amps with 6 per channel (ie 12 per balanced amp channel as "the specs were better"
So I did! and I'm glad I did!
and now we are back to the same question as I STILL wouldn't mind a two device per channel/4 per balanced amp configuration as is being discussed here for my mids/highs if there wasn't a performance hit. It occurs to me that maybe another MOSFET might work better with fewer in parallel. Like maybe 140's or 250's -both of which I have (but I would have to buy the other opposite channel versions)
hmmm maybe some well-known amp guru in this area will pop in here....
So I did! and I'm glad I did!
and now we are back to the same question as I STILL wouldn't mind a two device per channel/4 per balanced amp configuration as is being discussed here for my mids/highs if there wasn't a performance hit. It occurs to me that maybe another MOSFET might work better with fewer in parallel. Like maybe 140's or 250's -both of which I have (but I would have to buy the other opposite channel versions)
hmmm maybe some well-known amp guru in this area will pop in here....
Variac said:
DF is certainly better with more devices in output ;
but - that 's a goal if you use it in widerange config ; if you use it just for your dreky Fostex
you are good with just one pair of mosfets per channel ( two for balanced) ; having more DF is just irrelevant it''s always matter of compromise .......... but main factor is heatsink ; if you have it ....... it's pretty irrelevant how many outputs you'll use , from costs reasons ........ because you already spent bigger part of overall cost .
instead of 240/9240 pairs ......... ?
150/9150 .......
Wait!
I think I've got it !
250/9250
What's a really appropriate use for 250's?
I know the standard answer: It will work.
But is there an instance that they are preferable? Like maybe
if you are only using a few of them? heheheh
Looks like they are worse in specs but take more abuse- like you'd expect...
Ya see, after Burning amp, there were a bunch of them sitting there than no one wanted..
Heres the 250 data sheet:
http://www.irf.com/product-info/datasheets/data/jantx2n6766.pdf
Heres the 240 data sheet:
http://www.irf.com/product-info/datasheets/data/irf240.pdf
I think I've got it !
250/9250
What's a really appropriate use for 250's?
I know the standard answer: It will work.
But is there an instance that they are preferable? Like maybe
if you are only using a few of them? heheheh
Looks like they are worse in specs but take more abuse- like you'd expect...
Ya see, after Burning amp, there were a bunch of them sitting there than no one wanted..
Heres the 250 data sheet:
http://www.irf.com/product-info/datasheets/data/jantx2n6766.pdf
Heres the 240 data sheet:
http://www.irf.com/product-info/datasheets/data/irf240.pdf
Variac said:
looking at Ciss and other C data - I think that they are more than good if you use just one pair/channel
crank bias ............... through the roof,babe !!!!!!!!!!
yeah.......... so poor mod was forced to clean rented space .......
EDIT:
I'll ban some mods for OT writings ......
this isn't F4 thread .........