I am about to start my build. Can I get some advice please.
Heatsinks are the Conrad MF35-151.5 (2 of them, 1 per channel), 0.02mm mica washers and silicon grease.
Antek AS-4218 400VA 2x18v, 8x 50v 18,000uF caps, CRC standard Pass power supply.
PCBs are DIYAudio, PRP 1/4 watt resistors, Panasonic 3w/5w resistors, hand-matched JFets (K170, J74), not matched mosfets (IRFP9140 & IRFP240)
No thermal protection or current limiting portions of the standard circuit. No DC speaker protection either. Just a speaker delay at power-on to prevent surges.
What special precautions do I need to take to make this honed down version of the circuit? I know biasing is likely to take longer, and that drift may occur in extremes of temperature, so any experience or advice is appreciated.
Heatsinks are the Conrad MF35-151.5 (2 of them, 1 per channel), 0.02mm mica washers and silicon grease.
Antek AS-4218 400VA 2x18v, 8x 50v 18,000uF caps, CRC standard Pass power supply.
PCBs are DIYAudio, PRP 1/4 watt resistors, Panasonic 3w/5w resistors, hand-matched JFets (K170, J74), not matched mosfets (IRFP9140 & IRFP240)
No thermal protection or current limiting portions of the standard circuit. No DC speaker protection either. Just a speaker delay at power-on to prevent surges.
What special precautions do I need to take to make this honed down version of the circuit? I know biasing is likely to take longer, and that drift may occur in extremes of temperature, so any experience or advice is appreciated.
You may remove the limiter (be careful), but leave the thermistor in the bias circuit. It's not worth the brain-damage with keeping the bias stable if it's not there.
The F5 is one big teeter-totter, thermally tracking the bias should be considered mandatory.
Nelson removed the limiter in the F5Turbo, but not the bias thermistor. That's a very strong hint.
The F5 is one big teeter-totter, thermally tracking the bias should be considered mandatory.
Nelson removed the limiter in the F5Turbo, but not the bias thermistor. That's a very strong hint.
OK, so you are right. I was inviting somebody to tell me how stupid a plan that was. I was just taken in by what Peter Daniel said about his F5, that it was fairly average until he removed those parts of the design. I guess he is expert enough to deal with the consequences of an amp that loses bias relentlessly.
So, what really constitutes the thermal tracking part? Is it just R15, R16 and the thermistors?
So, what really constitutes the thermal tracking part? Is it just R15, R16 and the thermistors?
As much as I like Peter and his genuinely fantastic products, he is the type that talks about the different sounds of heatsinks...
Anyway, the easiest way to disable the limiter is to omit the ZTX transistors.
I'm glad you found it useful. 
Please take a look at the F4 guide, there is much in common to both amps. Obviously the amp circuit is different, but the PSU, chassis, and many connections are similar.
http://www.diyaudio.com/forums/pass-labs/234355-guide-building-pass-f4-amplifier.html
Please take a look at the F4 guide, there is much in common to both amps. Obviously the amp circuit is different, but the PSU, chassis, and many connections are similar.
http://www.diyaudio.com/forums/pass-labs/234355-guide-building-pass-f4-amplifier.html
Pathmark -
I've run into bandwidth issues with the hosting site I use... I'm at the free limit and am not sure how I am going to proceed... Starting to pay for something has it's pitfalls as I would then have to pay indefinitely...
Anyway, the good news is that the Free limit is a monthly issue and will reset in a couple days (Anniversary of my joining day, not end of month, so it's an odd date...)
My suggestion is as follows;
Wait until you see everything again.
Save the page locally so you can view it off-line. -- This way you have it and are not at the mercy of photobucket.
I will do something in the near future to alleviate this problem. Probably a PDF and a re-make of the photo part of the thread and host all the photos locally. Like anything, it's going to take a bit of time.
I've run into bandwidth issues with the hosting site I use... I'm at the free limit and am not sure how I am going to proceed... Starting to pay for something has it's pitfalls as I would then have to pay indefinitely...
Anyway, the good news is that the Free limit is a monthly issue and will reset in a couple days (Anniversary of my joining day, not end of month, so it's an odd date...)
My suggestion is as follows;
Wait until you see everything again.
Save the page locally so you can view it off-line. -- This way you have it and are not at the mercy of photobucket.
I will do something in the near future to alleviate this problem. Probably a PDF and a re-make of the photo part of the thread and host all the photos locally. Like anything, it's going to take a bit of time.
Andrew -
Have you perhaps thought that there is a very specific reason why I don't attach them?
I realize that choice is now having some consequences for me, and part of that solution might include attaching them locally. Also I plan on making a downloadable guide in .pdf for some other easily readable format.
Have you perhaps thought that there is a very specific reason why I don't attach them?
I realize that choice is now having some consequences for me, and part of that solution might include attaching them locally. Also I plan on making a downloadable guide in .pdf for some other easily readable format.
F5 question dirveing ribbion speakers
Hi Gents, I dont want to hi jack or change the subject but i think i may be in the right place for an answer here?.
I am in the process of building a pair of F5 monoblocks and like the idear of Planear speakers and/or DIY ribbion tweeters, my question is would a F5 be able to drive a load like that?
I know it will go in to low ohms " with out burping" as papa says and a ribbion tweeter can be as low as 2 to 3 ohms , but is around 25 watts enough, do you think an F5 could do this? (though the sensivity of the ribbion depends on the mangents etc..)..if so my next project is.......?
Cheers
Johnny
Hi Gents, I dont want to hi jack or change the subject but i think i may be in the right place for an answer here?.
I am in the process of building a pair of F5 monoblocks and like the idear of Planear speakers and/or DIY ribbion tweeters, my question is would a F5 be able to drive a load like that?
I know it will go in to low ohms " with out burping" as papa says and a ribbion tweeter can be as low as 2 to 3 ohms , but is around 25 watts enough, do you think an F5 could do this? (though the sensivity of the ribbion depends on the mangents etc..)..if so my next project is.......?
Cheers
Johnny
driveing ribbion or planears with an F5
Hi, Thanks for that 6L6 your opinion on that is much appreciated and I know i can go forward now .--, any one else actually drive ribbons or planer loud speakers with an F5?, if so any DIY planer/ribbon tweeter designs used? (A few on this site i must say) -- Must go now--off to the magnet shop-.
cheers all
Johnny
Hi, Thanks for that 6L6 your opinion on that is much appreciated and I know i can go forward now .--, any one else actually drive ribbons or planer loud speakers with an F5?, if so any DIY planer/ribbon tweeter designs used? (A few on this site i must say) -- Must go now--off to the magnet shop-
.cheers all
Johnny
How to Build It
This is really great.. all we now need is someone with time an enthusiasm to put together some PDF files for Pass DIY builds. This would be a great example of how to do it and it would be even better if this thread were referenced from a more central point, say Pass DIY site? It need not mean that they support the build description, but it would give newbies a flying start and the thread could be used for updates.
Thanks for a great piece of work
George
This is really great.. all we now need is someone with time an enthusiasm to put together some PDF files for Pass DIY builds. This would be a great example of how to do it and it would be even better if this thread were referenced from a more central point, say Pass DIY site? It need not mean that they support the build description, but it would give newbies a flying start and the thread could be used for updates.
Thanks for a great piece of work
George