F5 Turbo Builders Thread

[AndrewT]

Yes, shaving both sides.
I started by dismantling a few damaged ones. and then tested a couple of new ones.

[Rush]

Originally Posted by AndrewT

Yes, shaving both sides.
I started by dismantling a few damaged ones. and then tested a couple of new ones.

I would forget which is P and N and have a mess.
This seems a long way to go. Was't there a thread about a little heatsink that coupled 2 TO92 devises? Here is one: The next best thing to 2SK389 / 2SJ109 ?


Rush

[buzzforb]

I agree. If there was much to be gained, people like Nelson would be doing it. This is where DIY goes a little crazy.....as if I have rrom to talk

[sangram]

After my successful (sort of) attempt at the F5 a couple of years ago, I decided to get my feet wet with a full-fledged build including a nice chassis. I chose cViller's F5c schematic, added P3 and implemented the newer connection of TH1/2. Or you could say I picked the F5 Turbo V1, and added current limiting and a cascode. I needed a lot of swing but not much current capability as my load is a very gentle 8 ohms, but low sensitivity.

The build is essentially a balanced amplifier, with one F5T 'Module' per signal half. I understand that matching of halves is going to be a task in itself. One major schematic change I was hoping to make was to connect the wiper of P3 to ground instead of Pin1 to help with adjusting the circuit symmetry. The other big change was using much less feedback, which in my case stands at about 30dB total - 24dB per 'Module' and 6dB from balanced operation. This is about twice the F5T schematics. If it doesn't work out well I will double up the feedback resistors and look for more voltage upstream.

The power supplies will be 8x10000uF and 8x22000uF per monoblock, with 8 0.22 ohm resistors, all running off a 25V, 1KVA transformer and dual MUR3060 bridge rectifiers. This will give me a total of above 0.5F on 32V rails across both channels, hopefully that will be enough or just about. The heatsink and case are pictured here - 12" high at the sinks, 20" deep. The narrow width means copper heatspreaders are absolutely required (also because the sink has a vertical contact patch). I have all the components I need, just waiting for PCBs to be designed and printed. Career situation permitting, I should have more progress in a few months.

[Itsmee]

I like those heatsinks, where did you get them?

[AndrewT]

Yes,
I was thinking of getting a post and packing quote from that Indian manufacturer.
http://www.perfectmetal.in/contactus.html

Could it become a UK Group Buy?

[sangram]

Almost every Indian aluminum manufacturer has this profile in their catalog, minimum order is one bar - 6 feet, and cost is about INR 3000/- per foot for raw unfinished sinks, IIRC. That would be about $55 today and is a good time because dollar is quite high against Indian Rupee (bad for us who have to import everything). However I suspect you might get better/cheaper sinks from European suppliers.

In the site AndrewT has linked, this is N34 profile, on page 7 of the catalog. I outsourced the entire job to an outfit called Soundfoundations that does this sort of work (woulda posted the link but it might be advertising). The sinks were bought from Jindal, another, older/more established company. I've used the same profile in slightly shorter (10") length for my earlier F5 attempt and it was really good, the sink temperatures never crossed 60 degrees in the hot summer - each sink was dissipating 75 watts as my bias was a touch more than default. My room was a different matter though, so the F5 remains a winter-only amplifier

This build will see about 300W dissipation per monoblock, I'm hoping the sinks will manage or I will have to back it down to about 200W or so.

[kroyin]

I got quotes from perfect metal a couple of weeks back.They approximately $ costs for 1 feet segments

N1- 30$
N34- 27$ (PDF catalog says 30kg/m, website correct it to 16kg/m)
N56-60$

Taxes+shipping extra.

They are dealers & not producers so these would perhaps be Hindalco profiles

[cdfac]

apologies if this has been definitively addressed elsewhere, but is it safe to say that the 5U chassis now in the DIYAudio store is probably not up to a fully-biased 32V-rail Turbo V1? i see the rating of 0.28C/W reference in the chassis webpage and assumed this was probably for one side/set of 2 sinks, but didn't know for sure (i don't have a real good handle on heat dissipation figures yet).

while there's a lot more to it than heatsink surface area, obviously, a rough calculation shows that, not counting the waviness, these sinks are only about 10% larger in radiating area than a set of the 10" profiles from HeatsinkUSA that are 6" tall (what i used in my basic 25Wpc F5, borderline for that as-is). i don't know if there's enough magic in the chassis/profile to make up the difference.

[AudioSan]

Originally Posted by cdfac

apologies if this has been definitively addressed elsewhere, but is it safe to say that the 5U chassis now in the DIYAudio store is probably not up to a fully-biased 32V-rail Turbo V1? i see the rating of 0.28C/W reference in the chassis webpage and assumed this was probably for one side/set of 2 sinks, but didn't know for sure (i don't have a real good handle on heat dissipation figures yet).

while there's a lot more to it than heatsink surface area, obviously, a rough calculation shows that, not counting the waviness, these sinks are only about 10% larger in radiating area than a set of the 10" profiles from HeatsinkUSA that are 6" tall (what i used in my basic 25Wpc F5, borderline for that as-is). i don't know if there's enough magic in the chassis/profile to make up the difference.

its 0.28C/W pr SINK. so 0.14C/W pr side. they can handle a 2ch V2 fine.