Pass F5m

[generg]

And Nelson, it would be cheaper!

:--)) :--))

 

[generg]

Lynn, don´t do it, give Nelson a chance!

:--)) :--))

 

[lhquam]

Depends on whether 2 x half transistors and half resistors are more expensive than 1 x full transistor and resistor,

 

[generg]

And if you abstract from the voltages needed Nelson did the one transistor and one resistor solution already with the SIT-1.

:--))

 

[Zen Mod]

that one is complicated almost as he already made Babelfish SIT-1

 

[generg]

and by the way....

Spice says that the change from IRFP240/9240 to IRFP140/9140 in the normal F5 changes the pattern as well.

So there is a good chance for everybody running already the normal F5 to have the H2 dominance without changing the rest of the circuit to the F5 M parts.

Of course I will check it in real when my IRFP140/IRFP9140 arrive.

 

[Jaytor]

I've got a couple of chassis that I used for a previous pair of monoblocks that I'm going to repurpose for two F5M stereo amps. I designed a PCB to use the same mounting holes for the PCB and MOSFETs on the two side heatsinks.

In addition to the basic amplifier circuit, I added Jensen input transformer for balanced input (as well as RCA), a DC servo circuit, and a speaker protection circuit with delayed turn-on relay.

I just finished the design and haven't fabricated these yet, but plan to send them out in the next few days.

 

[EUVL]

My FFT plot was normalized to absolute ADC levels. The fundamental at -25dB corresponds to 2.82Vrms output followed by a 10:1 attenuator.

Would you be kind enough to show a FFT for 10kHz at 2Vrms, for comparison ?


Many thanks in advance,
Patrick

 

[lhquam]

Patrick: Unfortunately the chassis used for the F5m is currently occupied with my Holy Grail Output Stage (aka. ZD25-Mini). When I get a chance I will do a board and FET swap of one channel and do the measurement.

What load resistance do you want?

 

[EUVL]

4 and 8 ohm would be great.
And I meant 2.8Vrms, not 2Vrms.
Too quick typing.

And maybe a 10kHz square wave into 8R//100n,
If not too much trouble.


Many thanks,
Patrick

 

[lhquam]

Here are some F5m measurements using the IRF FETs since I do not have any of the Harris FETs.

Spectrum 10kHz 1Watt 8R (4V peak)

Spectrum 10kHz 2Watt 4R (4V peak)

Spectrum 1kHz 1Watt 8R (4V peak)

Spectrum 1kHz 2Watt 4R (4V peak)

Square wave response 4V peak 10kHz 8R

Square wave response 4V peak 10kHz 8R || 100nF

 

[EUVL]

Many many thanks.

So it appears that distortion is quite a bit higher at 10kHz.
Slew rate is about 3.5V/us.

And a little bit of ringing with reactive load.


Patrick

 

[lhquam]

Do you have any other requests for F5m measurements? I would like to switch back to using the chassis for my ZD25-Mini.

 

[chermann]

Hi

What is the FG of that amp?...normally the F5 is going up.
chris

 

[lhquam]

FG? Not sure what you mean.

 

[chermann]

-3dB Bode diagram

 

[EUVL]

Load dependent.
You need to specify what load.
Pure resistive ? 8R ?


Patrick

 

[lhquam]

Here is a Bode plot from simulation with 8R load, showing -3dB at 167kHz.
I did a bench measurement and found -3dB at 177kHz.

 

[EUVL]

Very accurate simulation.


Patrick

 

[Samuel Jayaraj]

lhquam, how does the Pass F5m sound compare to The Holy Grail Follower Output stage you presented here https://www.diyaudio.com/community/threads/the-holy-grail-follower-output-stage.406850/