F6 Illustrated Build Guide

@Alistair72 I t sounds like you and I are on the same timeline. I finished up about two weeks ago and have been listening with the bias at 0.52v. Temps fluctuated at first but then seem to stabilize. I observe a fair amount of variability of temps on both Q1s and Q2s, 38-44C with the Q1s running hotter at 0.52v.
Today I upped the bias to 0.58v and initially got a range of 53-66C with Q1 the hottie on the left channel (66) and Q2 the hottie on the Right (62). Why they changed pattern I have no idea...possibly vagaries in the components? I'm using a infra red temperature meter and I notice 3 or 4 degrees of variability based on distance and angles when I take a reading.

No hum to report.

I still would like to know if anyone runs a sub with this amp by using a signal dividing wire from the music source to the amp inputs. As I mentioned above I tried this and blew a fuse. Not sure if it was coincidence or possibly a peculiarity of the wiring or source I was using (source is an RME ADI2 dac) Hesitant to try again. I generally have had great success augmenting my speakers with subs, especially with lower powered amps.
 
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Perhaps add one of the 6/24 analogue Xovers to your system with a second amplifier for bass and bipass the speakers passive Xover - the ADI-2 dac is an amazing bit of gear.
Thanks James for making me aware of that component. It may be a worthwhile future project for me.

A more general question to anyone who knows about temperatures and the IRFP 240. The data sheet from Vishay indicates maximum operating temperature at 150C. The F6 guide by @6L6 says the bias limit should be set by a T max of 66C on the 2nd pin. Is that limit for optimal operating parameters, since it appears the IRFP240 can actually survive considerably higher operating temps?
 

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@Alistair72

I still would like to know if anyone runs a sub with this amp by using a signal dividing wire from the music source to the amp inputs. As I mentioned above I tried this and blew a fuse. Not sure if it was coincidence or possibly a peculiarity of the wiring or source I was using (source is an RME ADI2 dac) Hesitant to try again. I generally have had great success augmenting my speakers with subs, especially with lower powered amps.
Might, or might not be connected, but information anyway.
I made up some triple cat5 speaker cables to replace multistrand (standard) cables.
When I switched on, I had a strong hum, and one speaker cone pushed forward. Immediately switched off and removed the cables, all ok afterwards with old cables.
I suspect instability and oscillation either capacitance or inductance related. Could not be bothered investigating so left it alone and running as it was.
 
It is typical for a few degree variance between the mosfets. You can check the heatsink temperature right next to the mosfet and the body of the mosfet and mark the difference between them. Look at that calculation for all the mosfets. If the difference is similar, then you don't have anything to worry about.

That will give you an idea if you are not transferring the heat effectively. The more you go above 65 degrees on the center pin, the shorter the lifespan of the mosfet will be. Some people like to turn the pot up until the mosfets melt and then turn it back a quarter turn... Joking but people run them pretty hot.

Glad you have been able to spend some time with it!
 
As Mike said above - that pretty much sums it up.

Just a bit more ... Sometimes the heat transfer between power fet (as measured on that centre pin) and the heatsink varies a bit due to the heatsink surface, insulator, goo, pressure, washer size, mounting hole thread angle, etc - that's also pretty normal too.

Between the extraordinary abilities of the ADI-2 to modify the sound and the transparent operation of the 6/24 kit Xover, you will be able to play to your hearts content - if the bass cross over freq is low enough, you can use a high efficiency class D amps for the bass without "breaking the bank" and quite a few good ones available now.

I've found the F6 to be quite sensitive to the power supply and the choice of caps but nowhere near as "touchy"as the F5 for speaker wires, etc - glad you found the problem early, Colin.
 
I'm organizing a badge - it's basically the same as the official F6 sign with smaller diy added - haven't found a badge maker out here yet - a detail ...

I have an interest in different types of power supplies and their different effects asit varies with different amps - different is the emphasis here, as you;d expect. In the classic C-R-C I have a liking for the old style Epcos "Sikorel" caps but for better overall sound, have progressed to the DNM T-Netwok caps and this amp drives my Betsy FR drivers > 160Hz in a folded open baffle, not full range.

For a change (and curiosity!) I 'upped' this with a Toriody (Poland) transformer (20v sec), LT4320 rectifiers, same caps followed by a version of the Salas L-Adapter regs - a rather refined sound with increase 'punch' if that isn't too presumptuous.
I'm now playing around with one of those 'u-beaut' switch mode supplies from MicroAudio, from Jordan (a specific design for class A amps, with +/- 27v rails) and the same L-Adapter reg supply with a rather different sound - more detail, darker background, quite a different overall sound - still getting used to it.

Also, this is still using the Ayre QB-9 dac as the reference so not everyone's choice of a source - I'm still finding my way around the ADI-2 dac and it's potential and wondering why I haven't used tone controls for so many years, apart from the simple 'tilt circuit' from Glassware - it's a bit of an 'eye-opener'!

... my 2 cents
 
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Finally completed my F6 build. This is my first FirstWatt DIY amp. A huge big thanks to Mr. Pass for sharing his design and the entire commumity here whose posts helped me and your builds inspired me. Thanks to @6L6 for the illustrated guides. I'm very glad I built this. The amp is super silent and sounded wonderful right away. Not sure if it gets better as it breaks in. Folks were not kidding when they said it gets hot. Right now it's peak of summer here with temps reaching 42C and I can barely touch the heatsinks for a sec!

The enclosure is DIY since importing the one from Modushop was getting very expensive. That turned out to be quite challenging it took the most time. It's aluminium and anodised.

Couple of questions

1. I've noticed that the bias voltage slowly keeps rising. When I set it at around 0.52V after 30 min of running I noticed that on cold start the bias is just about 0.47V and then slowly climbs up. Is this fine or should I set it so on cold start it is 0.5V and let it rise from there?

2. I've read that the offset won't remain steady at 0. It also seems to creep over time. What value is considered bad?

Sharing some pics..

View attachment 1050628 View attachment 1050634 View attachment 1050630 View attachment 1050629

It is a very neat build! Could you please let me know the size terminal block you used on the F6 boards?
 
Yes, I'm a bit of a "fiddler" with these things - can't leave well enough alone! I won't mention sound differences in capacitors and resistors as I'll probably be dis-something'd or other - we're living thru weird times when differences are criticized but we've always got the diyA, eh!

I would like to say that the more sophisticated power supplies has resulted in overall "better" sound but they're just rather different - I have the H2 kit here and about to add it to the mix - a few of the guys here go nearly cross-eyed when mention of intentionally adding a couple % of the H2 and H3 to the sound plus changing the freq response with tone controls!

The main focus for me these days is the room itself and the vagaries of the balance between the direct and indirect sound (diffusion, etc) plus my listening preferences have changed quite a bit over the years.
 
Finish.Thank you all, for your help. Sound fantastic.
 

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I'm organizing a badge - it's basically the same as the official F6 sign with smaller diy added - haven't found a badge maker out here yet - a detail ...

I have an interest in different types of power supplies and their different effects asit varies with different amps - different is the emphasis here, as you;d expect. In the classic C-R-C I have a liking for the old style Epcos "Sikorel" caps but for better overall sound, have progressed to the DNM T-Netwok caps and this amp drives my Betsy FR drivers > 160Hz in a folded open baffle, not full range.

For a change (and curiosity!) I 'upped' this with a Toriody (Poland) transformer (20v sec), LT4320 rectifiers, same caps followed by a version of the Salas L-Adapter regs - a rather refined sound with increase 'punch' if that isn't too presumptuous.
I'm now playing around with one of those 'u-beaut' switch mode supplies from MicroAudio, from Jordan (a specific design for class A amps, with +/- 27v rails) and the same L-Adapter reg supply with a rather different sound - more detail, darker background, quite a different overall sound - still getting used to it.

Also, this is still using the Ayre QB-9 dac as the reference so not everyone's choice of a source - I'm still finding my way around the ADI-2 dac and it's potential and wondering why I haven't used tone controls for so many years, apart from the simple 'tilt circuit' from Glassware - it's a bit of an 'eye-opener'!

... my 2 cents
Allow me to recommend an excellent gentleman, Bruton Heaton, who I stumbled upon when looking for badges for a pair of AR-2ax speakers I had restored. He did an F6 badge for me. He is easy to work with and affordably priced.
Audio Tags Iowa
POB 107
Corning Ia. 50841
[email protected]
He also sells on Ebay
 
Hello:

Something has got me thrown a little. I'm trying to start wiring my F6 up and was trying to sort everything ahead of time and make some diagrams to follow. It seems everything here says that, for an Antek transformer at 115V, the two reds are tied together and connect to the Line and the two blacks together to Neutral.

In the course of searching around I see the directions from Antek shown in this link:

https://www.antekinc.com/tech-faq/

It seems to contradict. What am I missing? I'm using the CL-60 thermistors as seems the convention.

Thank you,
John
 

6sX7

Member
2018-04-30 5:08 am
as it is AC, it doesn't matter which you tie to hot, black or red. Just make sure to tie both of the same color to the same outlet leg.

I've always tied red to hot as red is my mnemonic.

The CL-60 are a slow start circuit and help with in-rush current at first turn on.

Recommend to follow the schematic, especially regarding the safety cap.
 
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as it is AC, it doesn't matter which you tie to hot, black or red. Just make sure to tie both of the same color to the same outlet leg.

I've always tied red to hot as red is my mnemonic.

The CL-60 are a slow start circuit and help with in-rush current at first turn on.

Recommend to follow the schematic, especially regarding the safety cap.
That's good enough for me. Thanks very much.
 
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