VFET headphone amplifier

[Cauwil]

Hello,

I bought the vfet pt 3 kit, I have the necessary VFET and I want to use these parts to build a headphone amp.

What is the best way to achieve this ?

Many thanks,

Cauwil

 

[Zen Mod]

link to exact sch. ?

 

[adason]

What is vfet pt 3 kit? Where can i get it?

 

[Vunce]

Here:
vfetless-round-3-output-stage

 

[adason]

I am confused. Thread title clearly mentions headphone amplifier.

 

[Vunce]

Yeah, me too🤪

 

[Zen Mod]

using any of recent Papa's VFet amps for headphones:

- no need for gain stage, but some sort of buffer is needed, to properly drive OS; one idea - use FE having JFet buffer and xformer, but shorted (or just cap) instead of xformer
-take care of inserting some sort of power-on delay circuit for headphones, due to inevitable thump uring power on; with speaks that's not problem, it can kill headphones

now, if intended schm is posted here, I could write more

without it, I don't want to risk broken telephones scenario

 

[adason]

Converting any amp to headphone amp is just a matter of two resistors on the output. I used to do it for low power tube amps.

Why use 10watts power amp as headphone amp? When 10 milli watts is used?
When Whammy or ACP+ are available?
Vfet will require large heatsinks, high bias and will burn close to 100watts of idle power (~1.5A per channel at 24VDC).
Still easy to ask in vfet builders thread.

 

[Cauwil]

Thank you all for your answers.

@ Zen Mod : so I can use the FE described in this doc : https://www.firstwatt.com/pdf/art_diy_sony_vfet_pt2.pdf by replacing the transformer by caps ? Will 2,2uF do the job ? Can I put a pot at the same place to change the volume ?

Thanks again.

 

[Cauwil]

Hi,

Here is what I am going to do :

• build the 2 VFET kits
• use the FE card from the vfet part 2, short the xformer
• use a velleman k4700 kit to prevents switch-on clicks and DC components on the output
• use 2 SMPS DC Filter P089ZB Kit and 1 Mendel Meanwell 36v SMPS

I have 2 last questions:

• which values should I use for R1 and R2 - knowing that the impedance of by headphones should be between 32 and 300 ohms ?
• should I use 220 ohms parallel resistor at the outputs like xrk971 to drop off the output impedance : https://www.diyaudio.com/community/...-builders-thread.370689/page-113#post-7275358 ?

Many thanks

 

[Cauwil]

And I will run my topping E30 as a preamp

 

[cjfrbw]

This was the resistor complex from the Sony TA 4650 that connected the VFET amp to the headphone output:

 

[Cauwil]

Thanks !

 

[Cauwil]

What about using my thx aas 789 as a front end ?

Thank you