F5Turbo Illustrated Build Guide

for 28V5 rail (and you'll get something as Vac x1.25 , when PSU is loaded ) , use 15K up to rail , 10K down to GND

remember that you don't need making heaters of cascode bias net resistors ......... so no need for so low value as you suggested

Hi Zen, how much difference will it make if i keep both the resistances 10K, since the potential divider will just half the input voltage, in my case around ~14 V, guess that should work just fine
 

6L6

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F5Tv3_schematic.jpg


There is one error in this schematic - R26 should be 10K

Original documentation here -

http://www.firstwatt.com/pdf/art_f5_turbo.pdf
 
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Hi, noob here. Could someone explain what has been done with the terminal block with the leads coming from the transformer? Looks like there are some resistors or caps that have been soldered in but I can find no mention of them in the BOM or on the PSU BOM or instructions.

Thanks,

John
 
The gatestoppers work essentially like a shock absorber at high frequency (way above audio) and damp the Mosfet from oscillation. The F5T is a pretty darn high bandwidth design and depending on a ton of variables it can oscillate. Higher value gatestoppers help damp that tendency.

BUT, if your amp works, don't worry about it. If it was going to break out in oscillation it would already have done it and you'd know because your Mosfet would be fried.

6L6,

May I ask if anyone has tested ferrite beards instead of resistors as gate stoppers like this one https://www.tme.eu/de/Document/2c95f46ee39e2edc46e38cef692acce0/fr.pdf
, so 1000 ohm at 25MHz...

I tried this in my tube gear (but with not so critical tubes) and It was giving me a nice upgrade, clearer, more dynamic...its basically a piece of copper wire...

Is this feasable to usein the F5T as well ?
 
Ok, this might be an experiment for later then...

In 2017, I built this amp, it work with 32V rails...I want to improve and implemented Peter daniel changes like no thermistor, no diodes and implemented the bridge thing for earthing...and got a big FLASH when switching on in the area of my power plug.

Amp was dead.

I never had the time to look into it again until now. I checked the PSU through - is OK, delivers from its 600VA 25V transformer through a CLC-Filter about 36V in idle / no loads.

Than I used my variac to power the amp up again...but the mosfets stay cold. No currenty at all measurable at the 0,5 ohm resistors.

Did I kill them or are there other points to check before ordering a new set of matched fets ?