Ok, I'm going to call an ALERT.
The M3 threaded holes in the heatsinks are, in general, not deep enough to prevent the Output Stage mounting screws from bottoming out before sufficient seating force can be achieved between the mounting bracket and the heatsink.
The most straightforward work around will be to stack additional flat washers, or to include a split washer underneath the screw head, plus a flat washer against the mounting bracket.
The aluminum used for these heatsinks is difficult to clean up with a bottom tap. So I must withdraw that recommendation. Grinding down the length of the mounting screws for these locations will also work, if one has the tools and is comfortable doing that.
The M3 threaded holes in the heatsinks are, in general, not deep enough to prevent the Output Stage mounting screws from bottoming out before sufficient seating force can be achieved between the mounting bracket and the heatsink.
The most straightforward work around will be to stack additional flat washers, or to include a split washer underneath the screw head, plus a flat washer against the mounting bracket.
The aluminum used for these heatsinks is difficult to clean up with a bottom tap. So I must withdraw that recommendation. Grinding down the length of the mounting screws for these locations will also work, if one has the tools and is comfortable doing that.
A few quick checks... and an understanding of the GND scheme... and I'm ready for action.... I think...
Thanks once again to everyone that made this possible!
View attachment 944460
Lookin good! And you’re kit came with some nice, thick speaker wire!
The discrepancy is quite small, just enough for manufacturing variations to cause a problem. It doesn’t even look like there is a gap between the bracket and heat sink. However, the screw length doesn’t allow for a tight thermal interface.
Once I fixed one heat sink and stacked extra washers on the other one, I was able to see a little thermal grease squish out from underneath the bracket as the screws were fully tightened.
Once I fixed one heat sink and stacked extra washers on the other one, I was able to see a little thermal grease squish out from underneath the bracket as the screws were fully tightened.
This should work, flat washer + split washer. Make sure thermal grease is spread evenly on the bracket, and watch for a little to extrude as the screws are tightened down.
I’ve been thinking how best to share my ‘listening impressions’ of this amp. So far, every description is full of discrepancies and plain ole counterintuitive non-sense:
- It’s an eery detail machine, yet no details stand out
- Music is sugary and sweet, yet it doesn’t spoil my supper
- The soundstage wraps around me, yet my speakers are on an even plane
- Voices are floating, yet there’s no one in front of me
- Bass is big and present, yet we’re talking 10watts and meh damping factor
You get the picture I love it! Bravo NP 
- It’s an eery detail machine, yet no details stand out
- Music is sugary and sweet, yet it doesn’t spoil my supper
- The soundstage wraps around me, yet my speakers are on an even plane
- Voices are floating, yet there’s no one in front of me
- Bass is big and present, yet we’re talking 10watts and meh damping factor
You get the picture
I love it! Bravo NP 
These are standard UMS heatsinks, but I have some notes collected from over the years as this has been an issue that's popped up a few times.
- The most shallow part of the heatsink is about 7mm deep at the nook of the heatsink fin
- The current holes are drilled to 6.5mm, which is as deep as it is safe to go considering the thickness of 7mm
- Some drilling tolerance should be expected, as well as 0.2-0.3mm consumed by the anodization process
- 5mm should be a safe depth to use
- If this has ever been an issue for people using the Deluxe's UMS heatsinks, we have previously advised them to use washers. We include washers in the Deluxe back panel parts kit for this purpose.
- It’s possible to have some blockage in the holes due to lime deposits which formed during the rinsing after the anodisation, due to the high lime content of the local water. If this is the case some lime dissolving liquid that you would normally use for kitchen or shower glass should be able to dissolve it.
As I understand it, the threads included are the deepest HF2K can safely machine without risking perforation or deformation on the other side, given the material, thickness, and machine capabilities.
Last edited:
Thanks Codyt
Any noticable audible differences after speakers polarisations is reversed?
I know with ACA amp sound and is make difference
SE Vfet is reverse phase at the input as well
extract from original Mr. Pass article
Attachments
Nice build! You decided to move the front end boards a little further back than the build guide. Was this intentional? Do you think there is a difference? Just curious.A few quick checks... and an understanding of the GND scheme... and I'm ready for action.... I think...
Thanks once again to everyone that made this possible!
View attachment 944460
Rafa.
I'm part way through the assembly of #044. My FE boards are mounted, but I think I might turn them around to have the input face the RCA jack with the boards all the way back. My plan is to make it easy to use it as designed with the stock FE, or with a quick re-wire, run the OS straight to the RCA as Nelson mentions in the article, in order to run another linestage with enough gain / swing in front of it. I just like to have options for experimentation.
Crimp vs. Solder; why they don't mix
Pro tip: On the subject of crimping vs. solder connections, one should always use one or the other connection technique; never both. It's a myth that doing both is better.
A good crimp connection is generally more reliable than a soldered connection, since a proper high-pressure crimping tool will achieve a gas-tight "cold weld" between the crimp-on ferrule and the wire metal. This not only achieves a very low connection resistance, but keeps out environmental contaminants which might corrode the connection. The crucial factor is using the right tool - I highly recommend using a ratcheting-cam type crimp tool in order to get adequate leverage & force at the die to make a proper connection. Inexpensive rigid plier style tools can be inconsistent, and many users don't apply enough force.
Unfortunately, if you attempt to solder an already crimped connection, you're likely to do more harm than good. The application of heat will relax the stresses in the crimped metal which are holding the connection tightly together, degrading the crimp strength. Further, the solder is unlikely to properly penetrate the full mating region, whilst intrusion of fluxing materials which cannot be cleaned out into the small gaps opened up by the thermal expansion of the two crimped metals introduces active chemicals which can lead to premature corrosion. For this reason, crimp+solder connections are generally forbidden by code / regulation in many if not all safety-critical applications.
Solder by itself is also a perfectly fine connection technique, and one which is easy for us DIY-er's to accomplish (and inspect) with good consistency. However is widely recognized as less reliable than a properly-executed crimp (though probably not enough to matter in our use cases, so long as you can solder with enough skill to avoid cold joints).
Google will surface loads of good in-depth info for anyone curious to learn more.
Pro tip: On the subject of crimping vs. solder connections, one should always use one or the other connection technique; never both. It's a myth that doing both is better.
A good crimp connection is generally more reliable than a soldered connection, since a proper high-pressure crimping tool will achieve a gas-tight "cold weld" between the crimp-on ferrule and the wire metal. This not only achieves a very low connection resistance, but keeps out environmental contaminants which might corrode the connection. The crucial factor is using the right tool - I highly recommend using a ratcheting-cam type crimp tool in order to get adequate leverage & force at the die to make a proper connection. Inexpensive rigid plier style tools can be inconsistent, and many users don't apply enough force.
Unfortunately, if you attempt to solder an already crimped connection, you're likely to do more harm than good. The application of heat will relax the stresses in the crimped metal which are holding the connection tightly together, degrading the crimp strength. Further, the solder is unlikely to properly penetrate the full mating region, whilst intrusion of fluxing materials which cannot be cleaned out into the small gaps opened up by the thermal expansion of the two crimped metals introduces active chemicals which can lead to premature corrosion. For this reason, crimp+solder connections are generally forbidden by code / regulation in many if not all safety-critical applications.
Solder by itself is also a perfectly fine connection technique, and one which is easy for us DIY-er's to accomplish (and inspect) with good consistency. However is widely recognized as less reliable than a properly-executed crimp (though probably not enough to matter in our use cases, so long as you can solder with enough skill to avoid cold joints).
Google will surface loads of good in-depth info for anyone curious to learn more.