AMP HEAD Build Thread

[Joe Malone]

Thanks Joe.

Cant see anything unusual on the output, I just wasn't expecting them to be so hot. I probably wouldn't have mounted them one above the other, side by side might have been better.
These have a gain of about 5 times is that correct? If I input say 2v peak to peak 1KHz I see about 10v p-p output at max output

Thanks

Peter

Standard gain is 5.5 (15dB gain). The AMP HEAD input is made to be run by pro level +18dBM balanced outputs which really only need a gain of 2 to 3 to clip as this keep the noise floor very low.

Can be increased by making the two 1k resistors smaller in value.

[studiomollan]

[/quote]

Is the 1k now back to 1k? How many more dB do you think you need? Was the desk out unbalanced ?[/quote]

Yes the 1k is back and the outputs are balanced. 5-10db more should probably do it.
/
Emil

[TWM]

Standard gain is 5.5 (15dB gain). The AMP HEAD input is made to be run by pro level +18dBM balanced outputs which really only need a gain of 2 to 3 to clip. This keeps the noise floor very low.

Can be increased by making the two 1k resistors smaller in value.

Its perfect, I'm driving it from various balanced sources in my studio. Sounds really good.

Peter

[Joe Malone]

Standard gain is 5.5 (15dB gain). The AMP HEAD input is made to be run by pro level +18dBM balanced outputs which really only need a gain of 2 to 3 to clip. This keeps the noise floor very low.

Can be increased by making the two 1k resistors smaller in value.

Its perfect, I'm driving it from various balanced sources in my studio. Sounds really good.

Peter

Cool good to hear

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[Astuck]

Hi Joe,
I've ordered 2 Amphead kits but the schematic is absent of the box, could you send them to me ?
Thanks in advance
Astuck

[Joe Malone]

Hi Joe,
I've ordered 2 Amphead kits but the schematic is absent of the box, could you send them to me ?
Thanks in advance
Astuck

As the forum mentions no paperwork ships with the kits. Most small PCB kits can be built directly off the PCB overlay in a few minutes.

All info is on the build threads and for schematics not on the forum just send me a email request so I can reply with a watermarked schematic.

Also anything you are not sure off while building the kit feel free to ask questions here.

We have had to stop publishing most schematics directly on our forum as other companies were just cloning our products.

[Astuck]

Thanks Joe !
A last question, using a linear sym psu +24v/0/-24v, do you think mounting the 2 zener 24v can improve the stability of the psu ?

Cheers

[Joe Malone]

Thanks Joe !
A last question, using a linear sym psu +24v/0/-24v, do you think mounting the 2 zener 24v can improve the stability of the psu ?

Cheers

Yes & No. As they will draw more current so reduce the effect of the RC filter on the AMP Head PCB slightly. But if the symmetrical power was basically unregulated dc then the zeners would help.

But for normal regulated symmetrical power rails we leave the 2 zeners off the PCB as the simple RC filters on the AMP Head will make even the most basic regulated power supply very quiet.

[Lowfreq]

Hi Joe, I just have a question about the 10r resistors.

In the parts for the amp head (and for some of the other psu projects) it's specified as a carbon resistor.
Is there a particular reason for using a carbon resistor as opposed to using a metal film resistor?
Would a metal film resistor work the same?, or is there something that the carbon does better than the metal film?

My understanding is that the 10r with the 0.1uf cap is to separate 0v and chassi to help avoid ground loops. Is that right?

cheers,
Steve

[Joe Malone]

Hi Joe, I just have a question about the 10r resistors.

In the parts for the amp head (and for some of the other psu projects) it's specified as a carbon resistor.
Is there a particular reason for using a carbon resistor as opposed to using a metal film resistor?
Would a metal film resistor work the same?, or is there something that the carbon does better than the metal film?

My understanding is that the 10r with the 0.1uf cap is to separate 0v and chassi to help avoid ground loops. Is that right?

cheers,
Steve

Metal film resistors when used where high current surges happen can go open circuit with no external signs at all. Carbon ones will handle high surges and show discolouring if stressed by a fault.

So metal film resistor will work fine but beware if a fault happens and makes the resistor open circuit you will have to test them to check they are ok.

The 0.1uF on the AMP head are power rail decoupling and need to be fitted. The 10R are part of the +/-V RC filter for smoothing so also need to be fitted.

The 0.1uF across the 10R is used in our power supply kit for floating the 0v from ground. This is not used in the AMP Head as it is not a power supply.

[Bluzzi]

Hi Joe,

I just got my AMP HEAD and I'd like to hook it up but there is no wiring directions for power.

I'll be using 2 9v batteries in series for each side (center is 0v and ends are +18v and -18v).

It looks to me like I just need to hook up the -18v to the -V on the green terminal block, the +18v to the +V terminal and 0v is my center.

Headphone will hook up to the +L, -L,+R and -R then with ground on 0v?

Just making 100% sure before I hook it up.

Thanks

Jim

[Joe Malone]

Hi Joe,

I just got my AMP HEAD and I'd like to hook it up but there is no wiring directions for power.

I'll be using 2 9v batteries in series for each side (center is 0v and ends are +18v and -18v).

It looks to me like I just need to hook up the -18v to the -V on the green terminal block, the +18v to the +V terminal and 0v is my center.

Headphone will hook up to the +L, -L,+R and -R then with ground on 0v?

Just making 100% sure before I hook it up.

Thanks

Jim

HI Jim Yes you are 100% correct on the wiring. For batteries do not fit any zener diodes. For a power switch you will need a double pole so you can switch +18v & -18v at the same time.

[Bluzzi]

OK thanks Joe just needed to know where to put the wires up.

Cheers

Jim

Hi Joe,

I just got my AMP HEAD and I'd like to hook it up but there is no wiring directions for power.

I'll be using 2 9v batteries in series for each side (center is 0v and ends are +18v and -18v).

It looks to me like I just need to hook up the -18v to the -V on the green terminal block, the +18v to the +V terminal and 0v is my center.

Headphone will hook up to the +L, -L,+R and -R then with ground on 0v?

Just making 100% sure before I hook it up.

Thanks

Jim

HI Jim Yes you are 100% correct on the wiring. For batteries do not fit any zener diodes. For a power switch you will need a double pole so you can switch +18v & -18v at the same time.

[trenchrecordings]

I ordered the parts and built this pcb. Its not working. Sounds like a 8 bit motocycle reving up on the headphones when it powers up. Signal does not pass through. When i unplug power I can hear a distorted signal for a second before power dyes off.

Confirmed that it is getting +16V 0V and -16 using NE5534P.... oh just noticed it should have been NE5532 thats probably why

[Joe Malone]

I ordered the parts and built this pcb. Its not working. Sounds like a 8 bit motocycle reving up on the headphones when it powers up. Signal does not pass through. When i unplug power I can hear a distorted signal for a second before power dyes off.

Confirmed that it is getting +16V 0V and -16 using NE5534P.... oh just noticed it should have been NE5532 thats probably why

Yes you must use NE5532AP dual opamp. NE5534 is single and different pinout.