Thank you to everyone who helped out as well. It is now biased to the correct 200mv and is singing like no other. My god this thing sounds good.
R3/R4
Just measured voltage across R3 and R4 - it is 96mV, which gives 4.4mA (96mV / 22.1 Ohms). It seems a bit low. I was expecting about 7mA. Are R3/R4 supposed to be 22.1? I was using schematic from Post #1 of this thread...
Just measured voltage across R3 and R4 - it is 96mV, which gives 4.4mA (96mV / 22.1 Ohms). It seems a bit low. I was expecting about 7mA. Are R3/R4 supposed to be 22.1? I was using schematic from Post #1 of this thread...
You can play with the source resistors... Change them to 10ohm and try again.
But remember the input stage is a buffer, so if it's working, there probably won't be much change.
But remember the input stage is a buffer, so if it's working, there probably won't be much change.
Hello,
Greetings from Spain.
I´m wondering if I can drive an F4 using an Eastern Electric BBA.
Specs here:
Morningstar Audio Imports, Inc.
Loudspeakers would be Zu Druid MK IV.
Regards,
Daniel
Greetings from Spain.
I´m wondering if I can drive an F4 using an Eastern Electric BBA.
Specs here:
Morningstar Audio Imports, Inc.
Loudspeakers would be Zu Druid MK IV.
Regards,
Daniel
That may be the range of desired impedance of the amp other than that it a real puzzle . In the ad it states 100k down to 600 ohm amps . 10 k may be a miss print should have been 100k the range of amp input drive . That's a guess on my part . 😱
Last edited:
maybe they are telling us the output impedance is 800ohms and that the optimum load is 10kohms.
Because that widget is an "impedance interface," (whihc really means "tube tone effects box") I bet there is a pot somewhere not-normal to change the operating point and therefore output impedance, thereby having a big inpact of the sound without large gain swings.
Thank you all for the advice.
The thing is that I´ve been using the BBA with a First Watt F5 clone (now in rebuilding process) and I liked the combination a lot (my other amp is a Leben CS-300). Actually I preferred the BBA+F5 vs the Leben.
My setting with the BBA driving the F5 was: Gain at 11 and Volume at 9.
As I´d like to build an F4, and this has no gain like the F5, my concern is if the BBA might or not might be a good match.
Thank you again.
Daniel
The thing is that I´ve been using the BBA with a First Watt F5 clone (now in rebuilding process) and I liked the combination a lot (my other amp is a Leben CS-300). Actually I preferred the BBA+F5 vs the Leben.
My setting with the BBA driving the F5 was: Gain at 11 and Volume at 9.
As I´d like to build an F4, and this has no gain like the F5, my concern is if the BBA might or not might be a good match.
Thank you again.
Daniel
Hello guys,
I am gathering the materials to build the F4, I will be using this power supply (the one from diyAudio Store used for the build in this thread) and I have a doubt about the line input capacitor that is shown in this picture:
It is the small blue cap across the power input lines. I am not sure about it's value, is it 0.0033uF 120v? or something different? Any help will be appreciated.
Thank you.
P.
I am gathering the materials to build the F4, I will be using this power supply (the one from diyAudio Store used for the build in this thread) and I have a doubt about the line input capacitor that is shown in this picture:
It is the small blue cap across the power input lines. I am not sure about it's value, is it 0.0033uF 120v? or something different? Any help will be appreciated.
Thank you.
P.
Last edited:
It's a .0033uf (3300pF) cap that must be x1 (or x2) rated for across the line use.
Here's a link to an appropriate part-
WKP332MCPEJ0KR Vishay / Roederstein | Mouser
Here's a link to an appropriate part-
WKP332MCPEJ0KR Vishay / Roederstein | Mouser
Which prompts the next question:
would it be better to keep the capacitor and ADD a snubber in parallel to absorb the energy of the ringing?
would it be better to keep the capacitor and ADD a snubber in parallel to absorb the energy of the ringing?
My F4 which is slowly taking shape.The heatsinks are on there third amp and are from Fischer 265mm wide x 200mm long with fins of 75mm with a 12mm thick base.Toroidal is a 500VA from Air Link in the UK.
