I will check out the FETAudio but it looks like a private party type sale? What about the resistor value change for the mu follower network? I can't believe 3W resistors are that hard to keep in stock. Also, has anyone tried a generic low noise JFET n-channel 400 mW TO-92 transistor from an "in-stock" part at Digikey as a replacement for the LSK170? I want to order all my stuff from Digikey in one swoop.
Digikey has nothing like it.
I just found it in stock at Mouser for $0.47 ea.
http://www.mcmelectronics.com/product/2SK170
Digikey has nothing like it.
I just found it in stock at Mouser for $0.47 ea.
http://www.mcmelectronics.com/product/2SK170
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Nelson Pass mentioned Fairchild J111 being a possible substitute for 2sk170 for F5. Only $0.16 each, 73,000 parts in stock at Mouser. It seems like it would work very well in the ACA - using an available part would go with the spirit of making it an approachable, entry level project. I know LSK170 is available, not sure where and if one can buy in small qty. Mouser/Digi-key do not seem to stock.
I have bought from fetAudio and very reliable source. It can be off putting for a newbie to trust/buy from some dude in Hong Kong.
J111 Fairchild Semiconductor | Mouser
I have bought from fetAudio and very reliable source. It can be off putting for a newbie to trust/buy from some dude in Hong Kong.
J111 Fairchild Semiconductor | Mouser
So buy the rest of the stuff there.
And/or get the parts for the next amp and/or preamp now as well -- because let's face it, nobody builds just one of these...
EDIT - They do? Do you have a link or a Mouser part number? I can't find it on their search.
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2SK170BLF Toshiba | Mouser
Obsolete.............. Not available
I tried J111 and could not get it to work...
prob just something I don't know.
Obsolete.............. Not available
I tried J111 and could not get it to work...
prob just something I don't know.
What exactly was the issue with using J111? Just plain dead, did not work? I may get some and swap out in my ACA give them a shot.
Mouser had 2sk170GR back in Oct. 2012 but I have not seen them since.
So buy the rest of the stuff there.
And/or get the parts for the next amp and/or preamp now as well -- because let's face it, nobody builds just one of these...
EDIT - They do? Do you have a link or a Mouser part number? I can't find it on their search.
See link in post 841 above.
MCM (vs. Mouser). I bought a Raspberry Pi from them once - never dealt with them for anything else. Their FETs real?
Here is another US supplier.
2SK170BL - B&D Enterprises International
Still would like to try some J111 and see if I hear a difference in the ACA.
Here is another US supplier.
2SK170BL - B&D Enterprises International
Still would like to try some J111 and see if I hear a difference in the ACA.
I could not get it to drive the gate of Q1 but who knows what I did wrong...
Probably something really simple-- or stupid?
Even went so far as to make a test bed (with cheap but working spare parts)
works fine with k170's ...
I just saw the working link to k170's --- thanks.
it said Mouser so I didn't read careful....
Attachments
Alternate resistor possibilities
You might consider using one higher wattage resistor of half the value (two .68 ohm in parallel equals .34 ohms). Digikey has a .33 ohm 7 watt wirewound here: AC07000003307JAC00 Vishay BC Components | PPC7W.33CT-ND | DigiKey. Not sure if it will fit but you might find another that would.
If resistors R1,R2,R3 and R4 are same as original schematic the current bias will be 1.13 A. The two mosfets Q1 and Q2 would contribute a total of about 20.7w of heat to the heat sink (for one channel). The remaining heat being lost by the resistors R1 thru R4.
The "BL" grade of 2SK170 is same as "B" grade for LSK170, so you are good.
BTW, when I ordered the 0R68 3W resistors last October from Digikey they were out of stock also. I just had to wait a couple of weeks for them to restock and send order.
Hope you decided to go with a regular passive heat sink instead of water tank thingy.
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Hope you decided to go with a regular passive heat sink instead of water tank thingy.
xrk971,
Sorry for the smart*** remark.
I considered water cooling also, and did the design calculations, etc.
I ended up with a passive heat sink. If you want info on heat sink sizes let me know.
Regards,
cochleus
What's wrong with my Amp Camp Tea maker anyway ?
I just think it would look kind of wacky and cool. I should get a teapot and bolt the MOSFETs to it, then I can fill with water and it won't spill or splash and i can pour it out to have some hot water for a cup of tea! Not sure if 40 watts will be warm enough....I looked at passive heat sinks and if went that route I will probably use PC CPU cooler heat sink. I could order extruded heat sinks, I think they sell them by the inch and it would end up costing maybe $20 for two.
Where did you end up buying your heat sinks from and what size did you get?
The "BL" grade of 2SK170 is same as "B" grade for LSK170, so you are good.
BTW, when I ordered the 0R68 3W resistors last October from Digikey they were out of stock also. I just had to wait a couple of weeks for them to restock and send order.
Hope you decided to go with a regular passive heat sink instead of water tank thingy.
Glad I accidentally got the correct ones. It was not clear from the instructions from Nelson Pass which ones to get. So you don't want quiescent current too low then? Maybe someone can explain what the requirement is and how you figured that out.
Hot beverage? Hmmm, now that sounds useful.
The DIYAudio Store had heat sinks, you can get those if they are in stock, or get the size info. My nephew and I are building the Amp Camp and we are putting both boards on one heat sink. It is a 5 inch length of 10.08 inch profile from HeatSinkUSA. I have a 6 inch piece of that profile on a different amp that stays 22.6'C above ambient (measured next to mosfet) with 45.5W heat input.
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