ok, i think we need to know how much the jfets Id is, so we can stimate the voltage drop across the 1K.
23V - V(R1K) = max input dynamic.
so, 23Vpeak is of course the max theoretical input voltage due to tha max voltage rail.
The exact max input voltage, limited by max power, depends by the output mosfet quiescent current.
23V - V(R1K) = max input dynamic.
so, 23Vpeak is of course the max theoretical input voltage due to tha max voltage rail.
The exact max input voltage, limited by max power, depends by the output mosfet quiescent current.
Hi Tony,
No, use voltage, not current.
Measure power by figuring out available voltage. You lose some in the drivers and outputs for drive, then there is supply sag. Finally you have to use the resulting effective supply x 0.7071 in order to get a voltage to figure out power from. This is not both rails, one rail to common. That gives you power at peak, or maximum with a constant sine input.
No, use voltage, not current.
Measure power by figuring out available voltage. You lose some in the drivers and outputs for drive, then there is supply sag. Finally you have to use the resulting effective supply x 0.7071 in order to get a voltage to figure out power from. This is not both rails, one rail to common. That gives you power at peak, or maximum with a constant sine input.
Fresh F4 build is cooking on the bench. This is a “classic” build with Toshiba JFETs, Harris MOSFETs, Silmic IIs, Panasonic 3W resistors, 400VA Antek, etc.
I love how simple the fire up, bias, offset setup is for this amp.
First thing will be to have Pearl 3 and SCG preamp feeding the F4. Then sometime I’ll swap in a Juicy Music Blueberry preamp in to the system.
Great build guide as always by 6L6! Thanks!
I love how simple the fire up, bias, offset setup is for this amp.
First thing will be to have Pearl 3 and SCG preamp feeding the F4. Then sometime I’ll swap in a Juicy Music Blueberry preamp in to the system.
Great build guide as always by 6L6! Thanks!
Attachments
How much voltage does the SCG drive? With your Tannoys you don't need much power.
I'm curious, long term, if you will prefer the F4 over the Sissy... Again, you don't need much power... lucky you. ;-)
Have fun, looks very nice.
One thing, I realize that you'd be nuts to drive 100 wpc into those speakers -but your JBLS will do great... I don't see the balanced input. Are you planning on trying the bridged F4 amps? The sound is quite different, I think the lower damping factor and the greater power makes the speakers more fun... if a bit more inaccurate. I think of the bridged F4s as the DISCO F4s.
I'm curious, long term, if you will prefer the F4 over the Sissy... Again, you don't need much power... lucky you. ;-)
Have fun, looks very nice.
One thing, I realize that you'd be nuts to drive 100 wpc into those speakers -but your JBLS will do great... I don't see the balanced input. Are you planning on trying the bridged F4 amps? The sound is quite different, I think the lower damping factor and the greater power makes the speakers more fun... if a bit more inaccurate. I think of the bridged F4s as the DISCO F4s.
Tony - SCG is designed to drive the F4 to full output. It's a single ended design, so I assume it has enough drive for the SE F4. I can't say what it does with bridged/balanced F4.
I cooked the F4 overnight and bias and offset are both rock solid. I just put the F4 on my Tannoys after a cup of coffee, getting the kids off to school, and seeing the missus off to work. Music is cranking and I'm really digging the F4. My first impression is that it's very transparent and punchy. I'm also happy that now I have the use of much more of the attenuator positions compared to 20dB SCG + 20dB Aleph 30 gain chain. 20dB total is plenty for this particular speaker / room / volume combination, even for heavy metal.
I cooked the F4 overnight and bias and offset are both rock solid. I just put the F4 on my Tannoys after a cup of coffee, getting the kids off to school, and seeing the missus off to work. Music is cranking and I'm really digging the F4. My first impression is that it's very transparent and punchy. I'm also happy that now I have the use of much more of the attenuator positions compared to 20dB SCG + 20dB Aleph 30 gain chain. 20dB total is plenty for this particular speaker / room / volume combination, even for heavy metal.
🤘Oh yeah!
Spinning the remastered version of AC/DC’s Back in Black on vinyl this morning.
Hell’s Bells!
Spinning the remastered version of AC/DC’s Back in Black on vinyl this morning.
Hell’s Bells!
Hey... did Wayne Colburn decided to run for politics? ;-)
https://ballotpedia.org/Wayne_Colburn_(Mayor_of_Needles,_California,_candidate_2024)
https://ballotpedia.org/Wayne_Colburn_(Mayor_of_Needles,_California,_candidate_2024)
I have to start my build. I can’t wait.
Maybe I’ll try it out with some Kiss, Rush, and AC/DC. It will bring me back to my childhood 😎
Maybe I’ll try it out with some Kiss, Rush, and AC/DC. It will bring me back to my childhood 😎
I've been playing Gentle Giant all day.... F4 to the Metronomes. Great guitar, great singing, awesome tunes.
The trick, IMHO, with the F4 is to either have a preamp with lots of voltage swing, or do a post-preamp like the BA3 or YITCDAF4.
The sound of the preamp is what it will sound like, so don't skimp on that. The Iron Pre Bal works very well too (with the BA3B). Tubes, good tubes, are naturally, awesome. If you can swing it, get a CJ preamp, with teflon caps.
Metal. Honestly.
The trick, IMHO, with the F4 is to either have a preamp with lots of voltage swing, or do a post-preamp like the BA3 or YITCDAF4.
The sound of the preamp is what it will sound like, so don't skimp on that. The Iron Pre Bal works very well too (with the BA3B). Tubes, good tubes, are naturally, awesome. If you can swing it, get a CJ preamp, with teflon caps.
Metal. Honestly.
I can recommend the YICDAF4, it bumped a BA3 FE and an Aikido tube pre out of my F4. Very clean and punchy.
I have nothing to compare to like PJN as I have only used the YICDAF4 boards in my F4's, but I can say that the "Yes It Can Drive An F4" boards do kick some serious butt as an F4 front end. I'm very impressed!!!
Thank you @Mark Johnson
Thank you @Mark Johnson