F5 Finally Took The Plunge

[Ashg]

Hi Guys

Be gentle this is my first proper post on the forum. I registered back in 2011 and have been silently reading away on and off since then. I play around with electronics as part of my day job but nothing audio related. This is my first step into diy audio (been messing around with diy automotive ecu projects for the last decade but the goals are somewhat different to audio )

having read many of the projects on this site i have decided i rather like the work of Mr Pass especially his F5 design.

So far I have read just about every article and post i can possibly find on the F5 so I thought I would have a go at building one.

To start I plan to build a nice vanilla un-modded F5. It's simplicity really appealed to me and although technically I am not a total novice when it comes to general electronics, I am in the field of audio electronics. Once I have built a working amp my plan is to get a bit more adventurous and upgrade to a F5T but that's the long term plan.

So far i have ordered the following.

Diy Audio F5 V2.0 cviller boards
Diy Audio Filter Cap Board v2.0 JojoD818
Diy Audio Soft Start & Dc Protection Boards v2.0 JojoD818

4U HiFi2000 Case

F5 Board Components From Mosuer
https://gb.mouser.com/ProjectManager...sID=ac32cf6ded

Cap Board Components
https://gb.mouser.com/ProjectManager...sID=257b4a8472

Below are the things i am still working on/unsure of direction. If anyone can help me with any of the below i would very much appreciate it

1.) I am still weighing up pro's and cons with transformers (buy in mind for F5T or upgrade later? shielded or not?) are there any good suppliers that particularly stand out for audio in europe/uk? i have seen An-Tec but shipping is high.

2.) Mouser/rs/farnell don't stock Q2 JFET 2SJ74 or 2SJ108 is there another alternative or a reliable place i can get them from?

3.) the P channel MOSFET i ordered seems to be 12amp rated on all the sites i look at (fairchild and Vishay) but the F5 product manual said it should be somewhere between 15-20amps in rating (the N channel from vishay is rated at 20amps) am i missing something here?

IRFP9240PBF Vishay/Siliconix | Mouser

4.) what is the general consensus should i get the amp working without soft start and speaker protection first then add it later or just go for it from the beginning? (i have not ordered any components for those boards yet)

5.) Finally I have gone for pretty run of the mill components and will play about once it is working. would anyone mind having a look at the components i have ordered with regards to any beginner mistakes i have made?

https://gb.mouser.com/ProjectManager...sID=ac32cf6ded

https://gb.mouser.com/ProjectManager...sID=257b4a8472


Sorry for the long post I hope it is in the correct place and that i haven't repeated any questions i could have found with search (i did try search first)

Thanks

Ash

[AudioSan]

hello
1) antek is the best value for money. regardless of the shipping cost. and they have all values you need on shelf.
2) get your J-fets from spencer (he is a member here)
3) most P-ch fets is 12A. no problem at all
4) use soft start from the beginning. DC offset boards can be monted after adjusting of bias and DC offset is done. (no speakers connected before that anyways)
5) not to night but i can have a look at it tomorrow

[bear]

Originally Posted by Ashg

Hi Guys

<snip>my plan is to get a bit more adventurous and upgrade to a F5T but that's the long term plan.

The F5T's purpose is a higher B+ rail voltage. It's pretty much ONLY for that.

So far i have ordered the following.

Diy Audio F5 V2.0 cviller boards
Diy Audio Filter Cap Board v2.0 JojoD818
Diy Audio Soft Start & Dc Protection Boards v2.0 JojoD818

Pay attention to the posts about the effects of the PS on this amp.
I would use another method myself for the PS.
Hint: the PSRR of this amp is not fabulous.

<snip>

Below are the things i am still working on/unsure of direction. If anyone can help me with any of the below i would very much appreciate it

1.) I am still weighing up pro's and cons with transformers (buy in mind for F5T or upgrade later? shielded or not?) are there any good suppliers that particularly stand out for audio in europe/uk? i have seen An-Tec but shipping is high.

I'm in the USA, so someone else will have to come up with this.

2.) Mouser/rs/farnell don't stock Q2 JFET 2SJ74 or 2SJ108 is there another alternative or a reliable place i can get them from?

VERY good question. Beware of *fake* jfets being presently sold and imported from asia. They will not do the proper job. It is likely that any
Toshiba Jfets that have laser etched markings are not genuine - Toshiba used silver printing. Although only a curve tracer will tell reasonably well, and then a noise figure measurement will confirm.

There may be other jfets that will do the job... some may be SMD.

3.) the P channel MOSFET i ordered seems to be 12amp rated on all the sites i look at (fairchild and Vishay) but the F5 product manual said it should be somewhere between 15-20amps in rating (the N channel from vishay is rated at 20amps) am i missing something here?

You should choose the mosfets that are selected for the F5.
Although if you build the 2 mosfet CViller boards, then you likely have ample current capabilities. Figure your worst case load, your B+ voltage, and run ohms law to see what current is required, also look at the quiescent current WRT the B+ and figure the wattages.

Look at the pdf data sheet for the devices, and they have a SOA graph, you will find the DC line on the graph it will show voltage vs. current

IRFP9240PBF Vishay/Siliconix | Mouser

4.) what is the general consensus should i get the amp working without soft start and speaker protection first then add it later or just go for it from the beginning? (i have not ordered any components for those boards yet)

My view is that the amp does not need soft start unless you throw a big honking transformer on, with a bunch of capacitance.

Speaker protection is up to you, I personally prefer to live on the edge, and don't like fuses or protection circuits, *except* maybe when checking the amp out and making sure it is ok and stable. YMMV.

5.) Finally I have gone for pretty run of the mill components and will play about once it is working. would anyone mind having a look at the components i have ordered with regards to any beginner mistakes i have made?

https://gb.mouser.com/ProjectManager...sID=ac32cf6ded

https://gb.mouser.com/ProjectManager...sID=257b4a8472

Follow the BOM. For the higher wattage resistors, I suggest that they make a difference. I would use either better quality resistors or else parallel the wattage resistors called for making the correct ohmage.

Sorry for the long post I hope it is in the correct place and that i haven't repeated any questions i could have found with search (i did try search first)

Nice post. Not a problem as far as I am concerned.

You should be aware that this amp will make sound if it is put together according the the schematic, but the sonic character can change rather radically depending on the choice of mosfets, other parts, the power supply and the bias points.

Reports have been offered of a sound that ranges from dull and maybe mushy to dynamic and clean.

Thanks

Ash

The above is only my opinion, others doubtless have their own.

[Marra]

I agree with Audiosan; Spencer is the man for jfets.
Store | FET Audio
Regarding mosfets contact h_a on the forum or Buzzforb if you want to try Fairchilds instead of IRF's.
Good transformers in the UK are available from Avel Lindberg also Farnel carry a good range and people have mentioned Airlink transformers but I have never tried them myself.

[Ashg]

wow you guys are fast thanks for all the replies. lots of food for thought there.

ok have managed to order the JFETS from Spencer

Had a look at Avel and Airlink but went for the antek in the end their reputation/feedback on here seems pretty good and the total price was only £6 more (including shipping) than the uk suppliers (as long as i dont get an import tax bill :-S ) with the added advantage of split primaries (never know i may move state side one day)

has anyone done a back to back of the IRF's vs the Fairchilds? was there a notable difference in final SQ? I did try to get a couple of fairchild transistor kits from H_a but he hasn't replied to my pm or reply on his thread.

@bear thanks. i did do a quick tot up in my head to make sure it would technically work before I ordered the p channel MOSFET, I was more concerned that there was a 15-20amp version that I could not find that offered better final SQ. At work we end up chopping and changing components frequently depending on supply/price fortunately the judgement of final output quality is not reliant on my ears

I am trying to follow the BOM as closely as possible, hopefully what i end up with will sound nice, if not im sure i will have fun playing around getting it there.

[doolav]

Originally Posted by Ashg

Hi Guys
...upgrade to a F5T ...

So far i have ordered the following.

4U HiFi2000 Case

Hi Ash,

I would not swear, but those heatsinks might be not enough for F5T (more heat than F5 I guess). I used them for my F5 clone (F5 measurement/tuning), and with ambient temperature in my dwelling at ~19-20C they getting as hot as ~50C in hour - hour and half.

This is just from my experience (my first diy amp project), but really - the bigger HS the better (especially if you want to have some headroom to play with bias later).

Alex.

[doolav]

Correction - I used this type of HS, but 5U (210mm x 300mm).

Alex.

[Ashg]

Originally Posted by doolav

Hi Ash,

I would not swear, but those heatsinks might be not enough for F5T (more heat than F5 I guess). I used them for my F5 clone (F5 measurement/tuning), and with ambient temperature in my dwelling at ~19-20C they getting as hot as ~50C in hour - hour and half.

This is just from my experience (my first diy amp project), but really - the bigger HS the better (especially if you want to have some headroom to play with bias later).

Alex.

Hi Alex

I had a feeling that the sinks may be a bit on the small side, once I have the thing up and running I will take some measurements and share. if it needs more heat dissipation I have a nice pile of thick copper bus bars at work that I can chop up and use. At the moment I am waiting on parts.................

In the long run I will make a custom case and heat sinks (my other hobby is fabrication and i am lucky enough to have a big mill, lathe and tig welder)

i had a look at your thread and left a message hopefully it was constructive.

[esprit]

Hi Ash
Just purchased 2, 400va, transformres from Canterbury Windings.
Build of f5 still in progress.

[doolav]

Hi Ash,

If you have a big mill all the rest is unimportant

For prototyping it should be quite enough - it does not get hot instantly. Another option - going monoblocks, but this is space demanding.

Thanks for the suggestions in my thread,
Alex.