F4 power amplifier

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#4,983
Koos,

Recently I hooked up my DAC directly to a Mofo, which like the F4 is a buffer with no voltage gain.
The DAC's max output is 2V RMS., so the max power I was getting from the amp was about 0.5W into 8 ohms.

The funny thing was that it was loud enough for some nice listening for many recordings, and my speakers are only about 90dB sensitivity.

I think you'll have fun with the F4.

Cheers,
Dennis
 
#4,985
6L6 said:
You could tweak the gain on the XP-22... :yes: You'll probably void the warranty, but everybody knows that awesome lives on the side of tweaking and optimizing things to make your system perfect.

The BA-3 gain stage is a mini F5.

F4 is awesome.
Click to expand...
Spoke to Kent at Pass, XP22 will put out 24 vrms balanced assuming a 2v input. I think it would be close enough to try. If ultimately it’s not enough gain can always Pass the F4 boards along to a fellow DIYer to enjoy.

Interestingly he did mention to option of topping the top and increasing the gain the XP22.
 
#4,986
Dennis Hui said:
Koos,

Recently I hooked up my DAC directly to a Mofo, which like the F4 is a buffer with no voltage gain.
The DAC's max output is 2V RMS., so the max power I was getting from the amp was about 0.5W into 8 ohms.

The funny thing was that it was loud enough for some nice listening for many recordings, and my speakers are only about 90dB sensitivity.

I think you'll have fun with the F4.

Cheers,
Dennis
Click to expand...
Nelson Pass said:
Most of the time people think they need a lot more power than they really do.
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Thanks to you both for sharing your thoughts.

I can only fully agree. That’s the reason why FIRST watt amplifiers are such a great product. The first watt is the one that counts!

I will probably never use more than 1 watt during normal listening session, bearing in mind that the drivers are 98db according specs (although a Chinese datasheet) and my room size of 4 x 4 meters.

Thank you for sharing the information of such a great product.

Regards,

Koos
 
#4,989
state of fact - datasheet for speaker is anyway just half relevant

especially for FR - hearing is everything

I mean - had opportunity to listen to few drivers having similar numerical and graphical data

while one was to die for, second one is to run away ........ and that even not taking price tag in account

good side of it is - more fun that way ......... something as process of finding your better half ....... had to kiss many Princesses 'till I found my own :rofl:
 
#4,990
Zen Mod said:
state of fact - datasheet for speaker is anyway just half relevant

especially for FR - hearing is everything

I mean - had opportunity to listen to few drivers having similar numerical and graphical data

while one was to die for, second one is to run away ........ and that even not taking price tag in account

good side of it is - more fun that way ......... something as process of finding your better half ....... had to kiss many Princesses 'till I found my own :rofl:
Click to expand...
And you went with the speakers and not the princess… speaks for a) the speakers, and b) the emperess at home (hopefully not waiting with the rolling pin behind the door 😉 )

…

:devilr:

…

Mighty, have a happy smokefree new year with many great new projects and everything! It’s cool to be in a place with folks like you and all the other great folks!
 
#4,991
tnx 🙂

I was/still am - happy/worthy enough to be chosen by one who is not making speaker size restrains :clown:

I got only one, agree on that 158%, limit/condition regarding system in our living room - "make it functional all the time and do not change operational routine to something illogical"
 
#4,992
myleftear said:
And you went with the speakers and not the princess… speaks for a) the speakers, and b) the emperess at home (hopefully not waiting with the rolling pin behind the door 😉 )

…

:devilr:

…

Mighty, have a happy smokefree new year with many great new projects and everything! It’s cool to be in a place with folks like you and all the other great folks!
Click to expand...
Haha!
This (logical etc.) reminds me of rhis:
1640971894159.jpeg

(muji wall mounted cd player)
 
#4,994
Nelson Pass said:
I have a pair of the Lii silver 10's hooked up, and they get quite loud at 1 watt.

As well, their curves look to be accurate.
Click to expand...
How do you like the sound of the Silver 10’s, and what is driving them?

I was driving them by a Gustard X20 pro (discrete Class A output stage) in combination with the magical First Watt F6. I had lots headroom on the dial, even with the the gain setting at +0db. Sound wise it’s a dream team as well to my ears.

However, after reading the F4 article and all the reviews about her, it must be build! 😎 Thank you for giving the opportunity to do so. We are lucky humans with these gifts.
 
#4,995
during this past years i have built a lot of Vfet amp , in fact all of them but i don't know why but i always return to my diy M2 ( original version except CLC in the power supply). perhaps because it don't mesure as good as it sounds ... like my SET tube amp. will a F4 driven by my Set amp will be better ? or is it possible to add a transformer input "a la M2 " to have some gain with line input ?
 
#4,998
Dear Friends,

All parts for the F4 channels boards were received (except the JFET's), and I am in doubt regarding the resistors for R16-21.

The BOM says this:

R16 - R21 / Resistor / 0,47 Ohm / 3W

Unfortunately, these were not available locally and I ordered the ones that were as close as possible (please see below description and link). Are these sufficient or do I need to order other resistors?

Fukushima Futaba MPC74 5W 0,47 Ohm 5% Metal film resistor 0.47 Ω Radial wired MPC74 5 W 5 %
https://www.conrad.nl/p/fukushima-f...47-radiaal-bedraad-mpc74-5-w-5-1-stuks-443893

Thanks for your input!

Regards,

Koos
 
#4,999
The MPC74 are metal band resistors and are among the very best parts that you can use in that circuit position (source degeneration resistor).

If you have an adjustable power supply (bench top lab PSU or something like that) you can match the resistors by using the power supply it in current limiting mode to push 1 Ampere though them and measure the voltage drop. Not strictly necessary, but easy enough to do.
 
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