F5m kit

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#2,642
tonyEE said:
If I had to run away from the Mods.... which amplifier would sound best in Pago Pago? Upwind from the fish cannery, of course?

I looked at the build guy. I do have some parts.... and it looks reasonable. Might just give it a try to build. Looks like a 3U, 300MM size.

Already have an F5... it was rebuilt, started as a Rawson, so it has that all metal case that Tim uses.

BTW, the link to the F5m kit is bad.... and the "backpanel kit" is sold out...
Click to expand...
Get the 400 mm deep version. More sink than regular deluxe U4 @ 300 mm deep.

My 400 mm deep 3U F5m does get rather warm
 
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#2,643
My small F5m setup burning in. Blue sound, Khahadas DAC, Iron Pre, F5m.

I like it better than my original F5. Still has a certain edge I also heard with original F5 and F6, but improved in my opinion over original.

Slightly more gain than original, which is welcome. I remember back in the "original F5 days, before P3 knob, folks would leave out the protection/limiting pieces. Basically and F5m.

I added a large complaint object to top of amp...
 

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#2,644
^ Hey, I got racks like that too....

I figured out how to add shelves from the top, without having to take it all apart... Do it by carefully rotating the top rod counter clockwise, then rotating it back clockwise. It will loosen the top plastic cap.

BTW, the last two racks I got from the local Craigslist. I just wanted one, and someone wanted like 430 for two racks, we settled at 300 for both and he delivered them in his truck. Four shelves each, one has the 12" LP sized shelf.

I'd show my F5 but then people would notice the Fancy Tim Rawson Casework. ;-)
 
#2,647
birdbox said:
Things that could have been brought to my attention...Yesterdaaaay! Lol. I'm kidding.


I actually looked at placing the boards lower when I was doing initial layout, but the boards don't fully match up with the UMS. There's 4 holes to mount the amp boards, but they do not all work with the UMS mounting pattern as only 2 will line up. I was scratching my head for a while, then just decided to mimic 6l6's approach. In fact, a lot of what I did mimicked 6L6's layout. That was intentional. No thermal concerns were mentioned with his build, so that's the route I went, and I'm not too worried about it. If it's not cooling efficiently enough, I'll just flip the amp upside-down, problem solved 😉 (or dare I bring up feedback control loops for actively controlled forced convection babysitters again?)

My gut tells me the difference in temps will not be all that significant, but I really have no clue as a noob here and my gut instinct is wrong 50% of the time. Darned convection never fully there when you need it, and then shows up when you don't want it (like the wind chill factor in MN when it's -16°F). This all sounds like a test problem in a thermal dynamics class. It's a good data point for a beginner like myself to account for going forward. At least I can avoid the math as it can be easily measured by flipping the amp inverted and measuring the difference in temps. I shall report back with results.....but first, gotta get this thing biased up tonight. Very excited to hear what it can do. For now, I got this distraction called "work" that's getting in the way of all my F5m fun.
Click to expand...
The boards are super light weight , no caps, hardly any parts. I just hung them dead bug style off the mosfets like I did my original F5, (with even tinier boards, Peter Daniels boards). It's worked fine for years....

Russellc
 
#2,648
So i have a pair of Fetzillas with decently sized sinks. I'm thinking of re-purposing the sinks and Exicon laterals (ECX10N20/ECX10P20) and making a layout and board, turning it into a F5m, so i won't have to get new sinks, drill and tap. Has anyone tried it with these or similar laterals? I'm prepared to spend time dialling it in.
 
#2,649
Not with laterals, but with Toshiba SJ201 / SK1530. These have a gate-source voltage of around 2V. I forgot what I changed other than making the source resistors 0R22 Ohms. I think I paralleled the trimpots with some resistance. Can‘t look right now because I‘m on vacation.
Worked perfectly and sounds mighty fine. Combined with 2 Connex 300REh as dual-mono power supplies, it is my favourite amp at the moment.

Regards, Claas
 
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#2,651
F5m.

Here's what I changed:
  • replace Q3 and Q4 with Toshiba 2SJ201 / 2SK1530 matched pairs
  • change R6 and R7 to 0R22
  • parallel R8 and R9 with 680R

There's loads of space in a 4U400 case once you use SMPSs ...
I just put a pair of PO89ZB filters (configured for positive resp. negative) behind the Connex SMPS 300REh. Doesn't do a lot, just reducing a tiny bit of buzz that I could hear with my ears against my 100 dB/W spaekers.

Regards,
Claas

F5m Boards all Toshiba.jpg


F5m dual mono SMPS.jpg
 
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#2,653
It is still on my list to measure it, but so far I'm too busy listening to it 🙂 ... so, can't really tell yet.

In my M2, also with 2SJ201 / 2SK1530, it looks like I had less than 0,03% THD at 1W, with 2nd and 3rd harmonic of comparable amplitude. However, those were measurements still done with ARTA, and I can't fully recall my set-up and measurement parameters ...

Regards, Claas
 
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#2,657
^ You are 100% correct, I perhaps oversimplified and assumed that they may want to try and also stuff in a linear PSU.

Overall, there are tons of options. However, in general, and in my opinion, stuffing an F5M into an ACA chassis (with a linear supply and with PCBs as supplied by the store) would be a challenge for anyone that didn't have "skillz".

:cheers:

Edited for clarity.
 
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#2,659
I don't know about fit with a linear supply (use of the smaller toroid would increase chances of success and go with lower bias range), but a smaller chassis like that will almost certainly require external forced air cooling. I built an F5m in a recycled short chassis and use two low-speed muffin fans under the unit. It works well and I am very happy, but Birdbox's suggestion about the F5m Redux is a more elegant solution, IMO.
 
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