Thanks, I didnt know if it would measure properly in circuit. I'll try it as soon as I get home.
Russellc
If your board is already mounted, you can measure across R3 and R4 instead - their legs are tied to P1 and P2 respectively.
Hmm, its was more my ambitions
I have asked fore their best, and wanted 4 of them
Price of those is not far from a pair of italian Modu enclosures
I worked my way down to E-bay (barred boss) heatsinks. Spending hundreds of dollars on heatsinks just does not seem appropriate for something that will inevitably end up sitting in my closet once it is perfected. My advice (which could be wrong) is that if you are going to spend a ton on heatsinks, go overboard and get enough heatsink so that in the future if you want to add more devices and/or more bias; you won't run into a wall. I am also thinking ahead to maybe X-ing 4 F5's into a stereo set - needs lots of cooling ability.
I bought all my components seperately - I think next time I may buy a premade chassis with full length heatsinks included. I saw a chassis I liked that even had an IEC connector and holes for speaker binding posts and RCA's, but it was going to be an additional $200 for shipping which made the total just too much.
BTW, two days ago I went to the hifi2000/modu factory to collect some enclosures and I discovered that they are going to introduce a new "all aluminum" version of their Pesante Dissipante model.
Now you can ask for top, bottom and rear panels made out of 3mm thick aluminum, brushed and black anodized.
I've been told the enclosures will be aprox. 30 € more expensive, but they now look really gorgeous.
THAT is really very good news
If they would offer more width options too it would be perfect
Anyway, Im probly just being stupid
I have TWO heatsinks, each measure 300 wide and 400 long(high), with thick base
They should give plenty cooling, tho I dont know excact cooling specs
I still regret having cut 100mm off each of them
QUESTION?
If I cut each of them in half, so that I have 4x 300x200
That way I can have 2 heatsinks pr mono
Would that give more effective cooling, over using ONE sink twice as big pr mono
I know this is more of a luxury problem, and may sound pretty daft
btw, only reason I was looking at Fissher SK157 is that it has long 80mm finning, and very effective
But I certainly wont pay 600 EUR to 1meter raw heatsink
US heatsinks on Ebay? Its heavy and shipping is a problem
dammit, I had promissed myself I would lay off this kind of hysteria
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When I design a pcb layout that mounts on the heatsink vertically (ie parallel to the heatsink flat back), I make it a point to orient the pads to mount a trimmer that has its adjustment screw facing and close to the top of the amp case. Bourns has a type with this screw. Much easier to adjust when the case is all built up. Think of servicing accessability and ease in the future. Also connect pins such that CW is less resistance and CCW more...much like adjusting a volume control.
If your board is already mounted, you can measure across R3 and R4 instead - their legs are tied to P1 and P2 respectively.
Stuffed, but not mounted......
Russellc
THAT is really very good news
dammit, I had promissed myself I would lay off this kind of hysteria
Hysteria, that's part of the thing here too.
Seriously, Cviller's F5 at BAF09 was on one big chunk of aluminum. Just bias it to normal bias, or till it reaches 55C at room temp, whichever comes first.
Cutting sinks with a Non ferrous blade is kind fun, but a mistake can make a set look really ugly.
Ofcourse
That heatsink might actually very well be the exact one I have
Fore that one 200mm is the optimal limit where cooling gain curve flattens, and cooling gain becomes less beyond this length
Which indicates that 2x 200mm is more effective than 1x 400
Now thats settled, I can spend some money on other more important parts instead
Close to 100% more effective.
SK56 is the most common 300mm heatsink in these parts.
The curve of the Seifert KL-146 shows even better that it levels out at 200mm height, the KL-146 is close to identical to the Fisher SK56 that i posted earlier.
My Al-J's do +100W of heat on 2 SK93 heatsinks of 55mm length, with boards from the GB at Holger's analog-forum.de
(are topped by hardened glass panels : Anordna shelfs for IKEA's Lillangen series, come with pre-drilled corner holes for peanuts. I bought 100 of the old series for ~$0.29 each
)
SK56 is the most common 300mm heatsink in these parts.
The curve of the Seifert KL-146 shows even better that it levels out at 200mm height, the KL-146 is close to identical to the Fisher SK56 that i posted earlier.
My Al-J's do +100W of heat on 2 SK93 heatsinks of 55mm length, with boards from the GB at Holger's analog-forum.de
(are topped by hardened glass panels : Anordna shelfs for IKEA's Lillangen series, come with pre-drilled corner holes for peanuts. I bought 100 of the old series for ~$0.29 each
)Attachments
a 100mm high sink can dissipate X watts.
A 200mm high sink can dissipate ~1.4*X watts.
A 400mm high heatsink can dissipate ~2X watts.
A 800mm high heatsink can dissipate <<~2.8*X watts.
A group of four 100mm high heatsinks in a row or forming four sides of a square chassis can dissipate 4X watts.
An 800mm heatsink cut into 8off 98mm high lengths to form two monoblock chassis can dissipate ~8X watts.
Assuming the back plate is thick enough and that deltaT(s-a) is the same for each.
A 200mm high sink can dissipate ~1.4*X watts.
A 400mm high heatsink can dissipate ~2X watts.
A 800mm high heatsink can dissipate <<~2.8*X watts.
A group of four 100mm high heatsinks in a row or forming four sides of a square chassis can dissipate 4X watts.
An 800mm heatsink cut into 8off 98mm high lengths to form two monoblock chassis can dissipate ~8X watts.
Assuming the back plate is thick enough and that deltaT(s-a) is the same for each.
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Interesting. Proof that sheer size doesn't matter.
That very nice info on relation between various lengths, and good to know, really good explanations
But bare in mind that its simplified to understand the relations
Note that almost all different heatsink designs behave different with various lengths
Ofcourse the number of outputs used, relative to sink size, and how they are spread/mounted have to matter as well
Fisher site is comprehensive and good to study to get some understanding of the effectivenes of various heatsink designs
Roughly, the longest finning seems better, and expencive
Also very wide heatsinks appears to be good, but of little use with only 1 pair output
Unless you do it like the master do it
I have no doubt that when 2 smaller heatsinks fore each channel is suggested in F5 manual, its well knowing that they are easier to get, and maybe cheaper as well
And makes nice small monoamps
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After 3 days of cutting, stripping, soldering, mounting and quadruple checking I just finished wiring up my F5 and fired it up for the first time. Rail voltages checked out okay. Once things warm up all the way I'll finish setting the bias. It's a good thing it's starting to get chilly here because this amp gets niiiice and toasty. I can't wait to give it a listen. This is my first DIY amp from scratch so I'm really excited.
I can't wait to give it a listen. This is my first DIY amp from scratch so I'm really excited.
