F5 Turbo Circuit Boards

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
buzzforb

buzzforb

Member
Joined 2010
I would max it out at between 380 and 400mV across the across the source resistors until you get the temperature performance stable. You can bump it a little after that, just be careful. This amp can get away from you faster than most if you have it biased too high and the diodes cut on. Highest I have had mine is 420mV.
 
R

Russellc

Member
Joined 2003
Paid Member
WalterW said:
but when do you get your trafos? Then you should be nervous....
Just make sure the bias trimmers are in the right position before you start...I measured every potentiometer twice with the ohmmeter just to be sure..
But you are right it's always a very exciting moment switching the 230V... those big donuts can destroy everything...
Click to expand...

I have mine set to the middle, hope this wont be a problem. I will be firing up with a variac, like I did with "regular" F-5. Is this sufficient sans light bulb tester? Or is this amp so twitchy the pots must be zeroed even with variac?

Thanks,
Russellc
 
SRMcGee

SRMcGee

Member
Joined 2004
Paid Member
Folks:

Can someone explain the purpose of Q1.1 and Q2.1 to me? I understood that cascoding helped to spare Q1 and Q2 from having to bear voltages beyond their meager capacity, which is why Q7 and Q8 are in the circuit. What do Q1.1 and Q2.1 add, and are they required in all implementations of the F5T?

Regards,
Scott
 
6L6

6L6

Moderator
Joined 2010
Paid Member
In a build with lots of output fets there is a possibility to run out of oomph in the driver stage. The .1 Jfets allow paralleling for the reason AudioSan mentions, and also if you need more current to run lots of output mosfets.

Remember this design can scale up towards the ridiculous - especially in terms of how much heatsink you need... :) :) :)

Great meeting you at Burning Amp, It's always nice to attach a real face to a forum member. :D
 
emyeuoi

emyeuoi

Member
Joined 2010
Paid Member
As per original schematic: 2 resistor 1 ohm in parallel.
I complete the biasing at 360 mV. Right channel is stable while the offset of the left is not so stable. Rechecked after 1 week and the offset value move from 0,2 to 17 mV. Re-biased at 0,0 mV and I will re-check time to time.
The result? Astonishing... :eek: I was expecting a good result but, togheter with the DCB1, the whole setup is fantastic. The only flaw... trafos are slightly humming :irked:
 
M

Mallard

Member
Joined 2003
Ok, thanks Emyeuoi. What kind of trafos do you use?


emyeuoi said:
As per original schematic: 2 resistor 1 ohm in parallel.
I complete the biasing at 360 mV. Right channel is stable while the offset of the left is not so stable. Rechecked after 1 week and the offset value move from 0,2 to 17 mV. Re-biased at 0,0 mV and I will re-check time to time.
The result? Astonishing... :eek: I was expecting a good result but, togheter with the DCB1, the whole setup is fantastic. The only flaw... trafos are slightly humming :irked:
Click to expand...
 
emyeuoi

emyeuoi

Member
Joined 2010
Paid Member
The caps are nr. 8 22.000 50V for each PSU. Those caps was part of the F5T Premium kit GB organized by buzzforb that also included the parts for the PSU (the caps, the bledder and filter resistors and the diodes). The PCBs are from TeaBag... Thanks TeaBag :up:

.... and Thanks Buzzforb :up:
 
Last edited:
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom