An illustrated guide to building an F5

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#942
6L6 said:
10K resistor and an LED between V+ and V- as Albert suggests.

And honestly, do yourself a favor and build it in one case. Add a handle or something. 2 cases, although seemingly an advantage when moving, will just be a colossal pain in the rear.

That said, the narrow heatsink tower will look pretty darn cool. (Add a few vent holes, it should be cool enough)





Did you use oil on the tap and back it out as soon as there was any resistance? I bet you didn't... 🙂 🙂 🙂
Click to expand...

Thanks guys! I'll implement the LED as suggested...

I used oil but after you do enough of them, 'resistance' becomes a relative term...🙄 I thought I was being safe, but I guess I wasn't safe enough.
 
#943
I like to add a Zener in series with the LED and across both rails, rather than across each rail.

The Zener switches off the Green LED when voltage drops significantly.

eg.
Vsupply = ±23 to ±26Vdc
LED Vf=1.8V @ 4mA
Zener = 33V
Resistor = {26+26 -1.8 -33} / 0.004 = 4300r, use a 4k3 or 4k7
at ±23Vdc the LED is still lit and passing ~2.6mA
@ ~36V total supply the LED is OFF.
i.e. it's off if one rail collapses to near zero and it's off if both rails sag badly to <±18Vdc
 
#944
Well the alum didn't work. I finally found a punch small enough to fit between the fins and was able to drive it out. The hole is obviously way too big now, but I thought of a couple options.
1. I have some 1/4" aluminum rod that I could thread and create a plug for the hole so that I could re drill it. Downside is the hole is about the size of a No10 screw right now, so I'd be taking out a lot of material to insert that plug.

2. I could drill/tap the whole for a 10/32 screw and insert a brass screw, cut it, drill and tap to 6/24 for the transistors.

I'm leaning toward no2 because it keeps the most material in the heatsink but I just wanted to see if I needed to be concerned about heat dissipation or currosion going to 3 dissimilar metals instead of 2?
 
#945
AndrewT said:
I like to add a Zener in series with the LED and across both rails, rather than across each rail.

The Zener switches off the Green LED when voltage drops significantly.

eg.
Vsupply = ±23 to ±26Vdc
LED Vf=1.8V @ 4mA
Zener = 33V
Resistor = {26+26 -1.8 -33} / 0.004 = 4300r, use a 4k3 or 4k7
at ±23Vdc the LED is still lit and passing ~2.6mA
@ ~36V total supply the LED is OFF.
i.e. it's off if one rail collapses to near zero and it's off if both rails sag badly to <±18Vdc
Click to expand...

and what the heck is the gain? the LED don't light up when the rest of the amp do?
 
#950
Hi all,
I've been lurking on this site for... I don't know, ten years or so... been a member for a few but never had anything to post. I just did my first REAL DIY project, other than a few pairs of speakers and a tube buffer, an F5. It's very vanilla: the amp boards and PSU board from the DIY store; the Deluxe 4U and parts kit from the same source; the same Antek transformer used in the pdf manual; components from Digikey and a couple of ebay sellers. Anyway, after a couple of hickups with the JFETs it's working and sounding great. I have about 585mV of bias and 1-3mV of offset on each channel, so not too shabby. I just wanted to say a HUGE thank you to 6L6 for the incredible documentation on the amp and the PSU, and of course to Mr. Pass (may I call you "Papa"?) for his generosity in releasing the design. This has been tremendously rewarding, both in the spiritual and audible realms. Next up: either an F6 or a Tubelab SSE!
 
#953
Yeah, I looked at the Aleph J as well. Two questions: 1) which sounds less like the F5, the Aleph J or the F6? I would have guessed that the F6, with the transformers, would sound very different. Not that I don't like the F5, I'd just like to have some variety. 2) Will the J2 ever be made available to the DIY community? Or are the parts too exotic to be practical?

The Aleph would have the advantage that I could just swap the boards into my F5 case; my layout for the transformer and power supply aren't conducive to putting the F6 boards into the same case. This is nice, but frankly I don't want to tear this down when I just got it working, so I would probably build a new PSU and put it in a new case anyway.

But I'll probably do the Tubelab build first. It's something completely different.
 
#959
I was looking for 2SK170 and 2SJ74 for my F5 build. Then, I suddenly remembered that I had a kit for Dispre2 before and the BOM used two 2SJ107 to substitute 2SJ74. So I actually has 4 matched 2SJ107 and 2SK170 with Idss: 8.2mA. 😱 :cheers:

So my question is that if these two jfet can be paired to build the normal F5 v3?

I will be "laughing all the way" home if those can work for me. :spin:
 
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