12au7 - irf510 headphone amp

[tangmonster]

The last two photos is basically a complete unit.

when i designed the pcb i could easily fit 3 pcb's onto one sheet at c boards so I ordered 3 pcb's.

When I ordered the enclosure I decided to build 3 so I can build 3 headphone amps but then their was a nice price cut for 4.

So currently I have 4 enclosures en 3 pcb's. Enclosures where around R200 each in total taking into account the setup charges.

I was planning on finishing 3 and seeing if anyone possibly even on these forums would like to buy the other one or 2.

Not looking into making money. Total cost price of one ran me just over R900

I have no problems lending one out to a audition first. Want to maybe swap out with ludo with his new design.


In all honesty I really do love the sound of these running off my pc sound card. I usually struggle to hear the difference between amplifiers.
I can't dead honestly say I hear the difference between my krell ksa50 clone and lm3886 chip amps for example. But there is NO question that this is an upgrade from the pc sound card output.

I have been using it for a while here at work now.

[Rendlan]

Hi!

I'm interested to hear what this jobbie sounds like since I recently acquired a pair of AT AD700 cans. I'm currently running them off the HP jack on my Pioneer SA508, and they sound better than anything I've ever heard. I do however feel that they could do with some more power behind them to fleshen out the lower end of the sound spectrum, but distortionless clarity, tightness and controll is at a premium. I've heard that valves ad warmth, but does that muddy the sound at all? Your comments would be appreciated.

Further, it would be really nice if the HPA could have stereo out so it could act as a preamp. I plan to run the turntable and CDP off it, so maybe multiple selectable source ins will also be handy. Are these mods possible with your design?

Thanks,

R.

[tangmonster]

I wanted to add an output but i felt that the output voltage was not high enough. 
At around 1.5V peak the waveform starts to get very distorted since I am running the valve on a much lower voltage than in the norm for 12au7.

This lower voltage is not a problem for the headphones since you will be deaf at that volume. But i am worried that it might be slightly to low for use as a preamp out on systems? Many amplifiers likes 2v or more peak voltage  for peak output.  The pc board I designed does provide for separate High voltage input for the valve that would solve this problem but this would add a second high voltage transformer power supply and need a totally different enclosure.

In short if you only need 1-1.5V peak for your amplifier this should work ,but it would be better to use a different power supply with separate 12V ac and around 100V ac input.

Adding more rca in puts will be tricky since there is no more space on the back. I would have to drill holes and add them in front or on top.
(in front will probably be easiest)

This enclosure en current power supply is more rated to just be used a headphone amplifier.
A rev B version could be build in a new enclosure if people where interested but would up the building cost around between R300 to R500 for extra components.


My idea was to design a valve based headphone amplifier with enclosure and power supply for build cost under R1000.

[Rendlan]

Okidokie....

Thanks anyway! 

Cheers,

R.

[tangmonster]

Hi All

By Friday I will have the two extra's done. I f someone is interested in a completed unit please let me know.

If there is enough people i can build more. I already have 2 friends that wants so chances is VERY good that I will build more anyway.

Anyone interested in a bare pc board or bare pc board and enclosure?

The rev B version of the pc board has space on it to populate either just the low voltage headphone amp parts.

OR

Dual voltage for use as preamp and headphone amplifier.


Currently I only have an enclosure designed for the plain headphone amplifier option , but if enough people are interested I could do an enclosure design with the added parts for 2 inputs with selector and headphone + preamp output.

[tangmonster]

I have put some of these items up for sale under bidorbuy

http://www.bidorbuy.co.za/item/37366108/Headphone_amplifier_using_valve_with_mosfet_class_A_output_PCB.html

http://www.bidorbuy.co.za/item/37351998/Headphone_amplifier_using_valve_with_mosfet_class_A_output.html

[2much2young2fast]

The build quality is great, I bought one

[tangmonster]

Glad you like it. Hope you like the sound too. loud enough?

[2much2young2fast]

More than adequate for my needs, haha