F5 Turbo v2 Stereo Amp Illustrated Build (my first amp build)

[chuckd]

OK. This has been a long time coming. I joined in 2013 and planned to get on to building shortly thereafter. But then I moved around the world a couple of times, a few different cities, and even more houses within the cities. Throw in a couple of kids and a couple of renovations and 2020 rolls around. Even then, it took an international pandemic to give me time to do the build.


Firstly, I want to thank everyone on this forum for the questions, answers and photos. I have read extensively, learned a lot and there;s still more to learn - and build. Thanks to everyone who has answered my questions as well.



In particular, I want to thank 6L6 for taking the time to talk to me (I think that was in 2014 when I was in NYC) and also for your illustrated build guides. With this guide I am following your lead and hope that this can give back to some other new diyers. So thanks Jim.



Also many thanks to Nelson Pass for providing the designs and articles for the amps, and being an avid supporter of diy. It is very much appreciated.


----


This thread is a work in progress. I will add photos and words and edit them over time. Today (23 August 2020) is the "first draft" if you will. I will try to bring in what I have learned from lots of different threads and add notes on things I found useful especially from someone who had no electronic/lab equipment at all.


On to the build....(see next post)

[chuckd]

Setting Up Shop


Hardware:



I didn't have anything to build this amp with. So I had to setup shop. I hate not having the right tools so was happy to buy a bunch of stuff. This for me was the hardest since I really didn't know essential items. Anyway, here's what I bought.


1. HakkoFX-888D soldering iron. and Hakko chisel tip 2.4mm x 14.5mm

2. Kester 24-6337-0027 63/37 solder for the PSU

2a. Cardas soldering wire quad eutectic silver solder with rosin flux for the gain and output stages - will it make a difference? I don't know but it couldn't hurt and we all want the best.

3. Variac 130V 5A from circuit specialists. I wanted the 250V but this was cheaper. I found this an easier solution than the light bulb test and I knew that I was going to do more builds so I just bought it.

5. A good Digital Multi Meter (DMM).I spent about $90 on this. Cant remember which brand. It'll be in the photos.

4. I researched standoff sizes and hex head bold, philips head bolts and basically spent far too long doing that. I ended up just ordering from Amazon an assortment of everything: M3 bolts, nuts and washes. I also got some nylon washers, lock washes, M3 fender washes (you need these for the fets on the heat sinks, M3 nylon lock nuts (not used on anything that gets hot).

5. The standoffs I got have 6mm thread and 6mm standoff. That's something I wasn't sure of - the depth of the holes in the heat sinks. 6mm seems to work.

6. Precision screw drivers and spanners/wrenches.
7. A silicon soldering mat.
8. Panavise vice
9. Quad Hands Flex Pus
10. Solder dispense reel
11. Some small parts storage case from Aldi for the components.
12. Two row Terminal Barrier blocks with 4 position, not the euro block as I learned. The black barrier ones are heavier and better for high current applications. I changed the euroblock ones i had out (you'll see the change in the photos).
13. An bunch of PCB mount, plug-in, screw in, 2 and 3 pole terminal connectors.
14. An assortment of insulated interconnects (ring, spade, fork) and different sizes.
15. A good wire stripper and crimping tool.



That's about it. I spent far too long researching this stuff, so just get the assortment.



Hookup wire


Well well well, this also took up far too much of my time as well. Stranded vs solid; gauge size; material; coating, how does the signal travel in solid vs stranded, and the list goes on. This gave me a massive headache. Since I have built the amp here are my thoughts:


1. I used solid 14 AWG for the PSU because I had it. It was hard to work with. Next time I will use stranded but the same gauge.
2. I got some 18 AWG (I think) silver coated copper stranded cable covered in PTFE from Apex (or is it Aphex) for the gain stage and output stage. This turned out to be too thick to fit in the holes of the red PCBs so next time I will buy 20 or 22 AWG (whichever one fits).
3. I will only use stranded from now on for the entire amp since it is easier to work with. I doubt I'll hear the difference.



Components


Another massive research project. This is worth doing to understand the different types of resistors (metal film, metal oxide, carbon ....) and capacitors. If you look in the BOM for the F5Turbo it has the part numbers so just get them.



1. I bought the vishay-dale metal film resistors for the amplification. After all the research I am still not sure how each of the parts affects the signal except for the transistors. But I spoke to 6L6 and he informed me (correct me if I am wrong here 6L6 if you read this) that the resistors and capacitors in the F5Turbo are not the most significant component and that I didn't need audiophile resistors that cost an arm and a leg.

2. I bought the matched JFETS from the diyaudio store way back when - the B-grade ones.
3. Thanks to some members here I got some matched FQA12P20 and FQA19N20 (I need to double check that)

4. But essentially, for the F5 Turbo v2, get the active parts from there now that they have them.

5. Get the pre-drilled chassis from the store. So much easier.

6. The back parts I got these from PartsExpress (the store was sold out) and they fit the back panel perfectly (dont forget the Shurter power entry module (see BOM) and 2 x 2.5A slow blow fuse):

- 1 x Neutrik NF2D-B-2 RCA Jack D-Series Red/Black (Part # 092-232)
- 1 x Neutrik NF2D-B-9 RCA Jack D-Series White/Black (Part # 092-239)
2 x Dayton Audio BPFI-G Fully Insulated Binding Post Banana Jack Pair Gold (Part # 091-630)


ok now on to the build...

[chuckd]

I'm not sure why but my pictures aren't attaching and I can't put them inline and comment on them. I'll keep trying.

[chuckd]

So it looks like I can only upload one file at a time. I have 70+ photos which will take a significant period of time to upload one at a time, so I will add them over time.



Here is a link to an album to make viewing the pics easier:


Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.



The problem is I am unable to easily comment on what was going on in the pictures.


Moderators, please let me know if there are any issues with posting an album and I will take the link down.


If anyone knows a better way to attach pictures here please let me know, especially putting them inline so I can comment.


Thanks and stay tuned.

[chuckd]

Here are some more PSU pictures.


I used the Rectifier bridges, no the individual diodes shown in the first pictures

[chuckd]

more PSU.

[chuckd]

I have more PSU pics but uploading them is such a punish I'll just skip to the amplifier stage. I have just finished soldering the connections for everything except the input and output signals.


The PSU powers up well and nothing burns up. I'm getting +/- 36 VDC.


Here are some pics:

[AudioSan]

Please remove those metal washers from the output boards and main boards. That is just asking for a short ciurcut.

[chuckd]

thanks. will do. i thought they were a little close but then I thought it was my bad soldering.

[chuckd]

So last night I finished the amp and set the bias with the help of 6L6.



I have added the final photos to the album so have a look at that. The link is here:


Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.


The photos here show the final bias ~350mV and 0V DC offset across the speakers.


Thanks again to everyone and if anyone (especially new members with limited knowledge) have any questions please ask away and I'll do my best to answer. I am more than happy to talk about process itself if not the specifics of the circuit.