Nelson indicated that to use a IRFP240 one might want to change the bias resistor a bit to compensate for the higher Vgs, although you probably wouldn't be able to hear the difference. Since the 2SK3497 has a Vgs much closer to the SS, no adjustments should be necessary.
I'm not sure you even need 10 of the SS JFETs. They aren't paralleled in the J2, so no need for matching there. The distortion profile is influenced by the ratio of the contribution of the CCS, so I *think* you just want the ratio of Ids between the 2SK3497 and SJEP120R100 to be the same for both channels. But you can adjust that with the resistors.
Yes, the Caddock's can be used. They can dissipate a bit more heat (which we don't need) and so are a bit more expensive, but they'll certainly work fine.
I'm not sure you even need 10 of the SS JFETs. They aren't paralleled in the J2, so no need for matching there. The distortion profile is influenced by the ratio of the contribution of the CCS, so I *think* you just want the ratio of Ids between the 2SK3497 and SJEP120R100 to be the same for both channels. But you can adjust that with the resistors.
Yes, the Caddock's can be used. They can dissipate a bit more heat (which we don't need) and so are a bit more expensive, but they'll certainly work fine.
Ok....thank you!
Then I can save a bit of money if I only get 2 or 4 of the SJEPs……
I am on the GB list to get a quad of 2SK3497 so why not use them and only use the SJEPs where is really matters.
The special heatsinks your use seems perfect for the long skinnies…...where to get those?
Do they have a part no.?
Then I can save a bit of money if I only get 2 or 4 of the SJEPs……
I am on the GB list to get a quad of 2SK3497 so why not use them and only use the SJEPs where is really matters.
The special heatsinks your use seems perfect for the long skinnies…...where to get those?
Do they have a part no.?
Jim, I was talking about unauthorized Firstwatt Heatsink copy sold by a shady seller from the far east. I urge people not to fund the growth of such operation. Fake product proliferation is a very serious issue here in the far east and south east asia, it will spill to your area when enough people feed the growth.
If you feel selling a copy of official Firstwatt heatsink is a non issue then personally I am very interested to produce them in large quantity for distribution in the States and Europe. Indonesia is the country to go for aluminum products. I defer to your leadership to organize the group buy.
If you feel selling a copy of official Firstwatt heatsink is a non issue then personally I am very interested to produce them in large quantity for distribution in the States and Europe. Indonesia is the country to go for aluminum products. I defer to your leadership to organize the group buy.
While we're on the subject, I'd also love to see an extrusion to accommodate a glass lid. Something about 1" wide which bolts to the top of the heatsink, then has a row of ventilation holes, and then a C-channel to capture the glass. One for each heatsink with some 3mm or 4mm toughened glass in between to show off our babies' innards.
The MF35-150 would be perfect if they made it with a flange. Sadly, their flanged range only goes up to the MF30-1F-75, which is way too small.
I like flanges because I want to see my amp. I'm the same with cars: if the engine isn't presented nicely then I'm not interested.
YMMV.
Cheers,
Jeff.
I like flanges because I want to see my amp. I'm the same with cars: if the engine isn't presented nicely then I'm not interested.
YMMV.
Cheers,
Jeff.
Jeff, the Pass FW extrusion pattern is very good both in heat transfer and esthetics, doable but not trivial to develop another pattern to be close in performance at both aspects. Do you have some alternatives we can discuss? I always admire the esthetics of european design. Prototyping to confirm heat transfer efficacy is not terribly expensive nowadays. We could do a group buy or initiate a kickstarter project once the design is matured. An official greedy boyz heatsink featuring european fin design, what should we call it, HEFD? Pretty sure the effort will be 100 % supported by Head Honcho of OPLDF.
To MEPER and others. Please understand that this is a joke. My doing so will serve as a beacon to encourage copycatters to redouble their efforts against Firstwatt products. I am far from encouraging such distasteful activities.
I'll admit I was thinking something really basic along the lines of the Conrad finned heatsinks, but then the penny dropped. The reason the FirstWatt fins are longitudinal is because it's the only way to have a longitudinal flange on the same extrusion. Something like the Conrad must be either cast or machined.
Given that, you could imagine something like flower petals. Forgive the bad graphic, but something along these lines:
Given that, you could imagine something like flower petals. Forgive the bad graphic, but something along these lines:
Attachments
I'll be happy to discuss about this at BAF
Our supplier can produce different heatsinks from our standard ones but they are going to be more expensive and require a good amount in order to start the production.If there is enough interest I can send you their catalogue so you can see which ones could better fit your needs and we can request them a quotation
- Gianluca
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