F4 power amplifier

[korben69]

Thank you Marco, good link.
I'm planning two mono units, I'll try to build 2 cases using the heatsinks, some wood and alu panels, wondering how...

 

[Jaac]

Re: Re: There is an update to the 6Moons Review...

I expect yet another soon.

Oké any hints ?? the INT 150 ?

 

[Nelson Pass]

I meant an additional installment of the F4 review.

 

[lykkedk]

Hi all...

I would like to know, if it's worth swapping mosfet's (irfp240) in / out because of this :

I am in progress of making my second (first is allright ) F4 monoblock, and while testing the left channel (bias/dc-offset adjust) i realised that i had a difference between the irfp240 at this range 248mV / 228mV (around 8-9%), is it worth doing something about or not ?

The rest of the irfp240 / irfp9240 is in the range 245mV - 250mV. This i consider good!

I know i could do some listning test, but please just tell me, if it's acceptable or not !

Please respond quick

Jesper.

 

[lykkedk]

I did correct, the error with another irfp240, sry. for my desperate thread...

i will pay ya' back with a pic. of my kids... (background is 2. F4 setup)

Jesper...

 

[carpenter]

Beautiful children!

The amp doesn't look half bad, either

 

[Zen Mod]

Beautiful children!

The amp doesn't look half bad, either

I second that



amp.... what amp?

 

[lykkedk]

By ZenMod : amp.... what amp?

No amp... 2 amp's ! have a look

Well it wasen't supposed to be shown yet, as they are not finish. But the other day i paniched, and accedently showed a pic... So what the hel..
Here is how far i got till now : Both amp's fully tested, and played some hour's. The temperature settles around 40-45C after 1,5hour and becomes 'termic-stable' here Bias is 250mV (pending between 243-252mV around the six mosfets on each channel. I still need a faceplate, (wood perhap's)but havent made my mind up about it!

I got 1 quistion today. I have a thermistor CL60 in serie with primary, which must eat around 0,9A / 230V and it grows really hot (around 60C) is this normal ???

I have uploaded a few more pic's on this website here
ENJOY.

Jesper.

 

[protos]

Thermistor starts cold with a high ohmic value to limit surge then heats up and drops impedance considerably at the correct current draw.
Not recommended of course for non-class a amps.

 

[lykkedk]

I use CL60's at 2 to 2.5 amps, and not above, as they
get quite hot. I have seen failures at 4 amps or so, so
above 2 amps I run 1 each on the dual primary windings.

This was from a very old thread, posted by master Pass himself... I guess it's allright that they grow hot!

Jesper.

 

[Studley]

Application question

In the user manual it says the F4 will work well with a preamp or other line source (assuming you have efficient speakers).

I'm wondering whether this would work: My CDP (ouput 2v) into a passive volume control (eg TVC or Lightspeed) into F4 driving Bastani Atlas open baffles (sensitivity 100db / 16 ohm load). A couple of watts is apparently enough to drive these OBs.

If necessary maybe I could insert a Burson Buffer in the chain as they add 6db.

??

 

[R-K Rønningstad]

Re: Application question

In the user manual it says the F4 will work well with a preamp or other line source (assuming you have efficient speakers).

I'm wondering whether this would work: My CDP (ouput 2v) into a passive volume control (eg TVC or Lightspeed) into F4 driving Bastani Atlas open baffles (sensitivity 100db / 16 ohm load). A couple of watts is apparently enough to drive these OBs.

If necessary maybe I could insert a Burson Buffer in the chain as they add 6db.

??

As the F4 is unity gain, your 2 Volts (peak) will give 1/8 Watt RMS into your 16 ohms speaker. (P =U^2/2*R)

RK

 

[Studley]

RK
OK thanks (for showing my ignorance )

 

[spencer]

I have finished my second F4 amp today. Distortions as below:

Left: 0.016% @ 1W and 0.03% @5W
Right: 0.017% @ 1W and 0.035% @ 5W
All 1kHz, 8.2 ohm load. Bias 1.5A each channel.

I used it as balance mode and the bass is much firm and strong than single unit guess due to higher power and match up with my Bal DAC. I would say it is another step better!

Thanks NP for sharing this wonderful design.

Spencer

 

[protos]

This was from a very old thread, posted by master Pass himself... I guess it's allright that they grow hot!

Jesper.

Don´t forget that is amps at the primary not the total bias+losses of the amp itself at the secondary.

 

[Salas]

Its amazing how the old and straightforward buffer concept is celebrated worldwide, only after Nelson put it forward again. It seems that audio world is not needing super circuits, it simply needs concept lead.
Bravo Nelson.

 

[korben69]

Great job Spencer, very attractive babies, congratulations !
Could you let us know about your enclosures, seems to be galaxy...
Thanks for the answer.
Very good looking F4 pieces, I hope to design mine as successfully as yours.

 

[spencer]

The enclosure has two version but my final version is 200mm height x 400mm deep x 350mm wide because I manage to find a supplier of heatsink of 400mm wide x 50mm thick in China. I design the case with all drawings and ask a metal shop to custom made for me for a total cost about US$200/ea. Face plate is 10mm wider/taller with 10mm thick and all polished and anodized per my spec. All the plates and heat sink are connected together with 12 pieces "L" sharp bar with either holes or tapped holes. Total weight of the case is 13kg net and completed amp is over 20kg.

With this size, the temperature rise is about 18 deg C max.

 

[Nelson Pass]

Its amazing how the old and straightforward buffer concept is celebrated worldwide, only after Nelson put it forward again.

Well, it just goes to show that this is a fashion industry.

 

[Variac]

Or it's because sometimes a new need arises which can be addressed by an old idea...