AMP HEAD II Build Thread

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Joe Malone
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AMP HEAD II Build Thread

Postby Joe Malone » Tue Jul 11, 2017 8:01 pm

AMP HEAD II
AMP HEAD II kit is a small but extremely powerful stereo headphone amp kit with balanced inputs, buss connector, volume control and has dual stereo input mixing for mixing inputs together or directly plug in our Talkback Comp and can take large dual 24mm and 16mm with pull switch volume pots. Pull switch can be set to mute, dim or mono function.
Mono and mute options can be added with one center off toggle switch and no other parts wired across the 4 outside pot terminals.
Several AMP Head II's can be power and audio connected with one 10 wire IDC ribbon cable.
Can sum several balanced inputs into AMP HEAD II with STATTEN and or DSUB4 kit.
Can handle full overload into short circuit permanently.
Can drive 8 to 600ohm headphones easily.
Frequency response 0, -1dB = 5Hz to 200kHz (or 5Hz to 50kHz if 220pF caps added under PCB across R7 and R8)
THD = 0.006% until onset of clipping.
Idle current = 50mA per AMP HEAD II kit.
Max current = 90mA per AMP HEAD II kit.
Can be powered by symmetrical +/-12v to +/-24v power rails.
Can also be powered by single 12v to 48v power rail between +V & -V as long as 2 zeners rated at half the voltage used are fitted to the PCB.
(for example 2 x 24v zeners fitted to make +/-24v from one of our 48v SMPS supplies. Any DC connector must be isolated type.)
+/-6v to +/-18v for NE5532AP and most dual type opamps. (Will work with lots of dual opamp type BUT they must be able to drive a 600ohm load.)
+/-12v to +/-24v can be used with OPA2604AP.

Note1: Current Ver1 PCB mono jumpers for pull pot doesn't work. All other functions work fine.

AMP HEAD II PCB. Size 3.35" (85mm) x 1.4" (35.55mm)
Image]

Fit all parts to pcb except zeners if not needed.
The 2 x *10R are 10R if powering with 36vdc and have 18v zeners fitted to the PCB. Or if using any +/-12v to +/-18v with no 18v zeners fitted.

Use step by step build map at this link http://jlmaudio.com/builds/maps/ampheadIImap.html

AMP HEAD II Parts list

1 x AMP HEAD II PCB
1 x Cliff S4 6.3mm Socket
1 x Cliff S4 6.3mm Chrome nut
1 x Cliff S4 6.3mm plastic dress trim
2 x Cliff S4 6.3mm Fibre washer
2 x DIP16 machined pin socket
1 x 20pin IDC header
1 x 3 pin socket & pre wired 3 pin plug
1 x 3 way terminal block
2 x 2 way terminal block
2 x 100uF 25v electro cap
4 x 10uF 25v Bi Polar electro cap
2 x 100nF mono cap
2 x 470R 5pin SIL Buss resistor packs
2 x 10R carbon 1/4 watt resistor
2 x 1k Metal film 1/4 watt resistor
20 x 10k Metal film 1/4 watt resistor

Options
4 x NE5532AP or None
1 x Dual 24mm 10k log pot or 16mm 10k log pot with switch or None

2 x 1watt zener diodes which are only needed in special setups and not included in the kit.
Extra 100nF decoupling caps can be mounted in the ZD+ & ZD- positions if zeners are not used.
If fitting zeners the 2 x 10R RF+ and RF-may need to change value depending on zener diode voltage and +/-V.
Joe :-)
JLM Audio
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kante1603
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Joined: Wed Jan 20, 2010 6:12 pm

Re: AMP HEAD II Build Thread

Postby kante1603 » Tue Sep 12, 2017 3:39 am

Hi Joe,

so I´m the one starting questions (again),hahaha :)
Have built the new AMPHEAD II in about half an hour,easy one.Very well done again Joe!

1.:For the 2 x 10r (RF+ & RF-):
I will run the amp head from +/-24vdc,Zeners omitted,I use OPA2604s.Must the value be changed?
Your instructions cover this topic as follows:
"The 2 x *10R are 10R if powering with 36vdc and have 18v zeners fitted to the PCB. Or if using any +/-12v to +/-18v with no 18v zeners fitted."

2.:The new AMPHEAD II has 2 inputs per channel now,great.Can I add up another one or two channels by simply adding them via 10ks (I have the schematics already,but maybe others are interested too)?

3.:It took a while before I found out what the hell the pads labeled R/B/Y meant.After receiving the kit it was clear…..colours for the phones o/p.

4.:I have my RG (L&R) on sockets now in case I will add inputs (via adjustable H-pads) to bring back some gain,learned it from my first AMPHEADs.

5.:For adding a mono/stereo/mute switch (DPDT toggle with center off position),can we use the procedure as described before in the old thread?
Link for reference:
viewtopic.php?f=2&t=165#p1430

6.:The build map is cool!

That´s it for today,

best regards,

Udo.

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Re: AMP HEAD II Build Thread

Postby Joe Malone » Tue Sep 12, 2017 12:55 pm

kante1603 wrote:Hi Joe,

so I´m the one starting questions (again),hahaha :)
Have built the new AMPHEAD II in about half an hour,easy one.Very well done again Joe!

8) :D

1.:For the 2 x 10r (RF+ & RF-):
I will run the amp head from +/-24vdc,Zeners omitted,I use OPA2604s.Must the value be changed?
Your instructions cover this topic as follows:
"The 2 x *10R are 10R if powering with 36vdc and have 18v zeners fitted to the PCB. Or if using any +/-12v to +/-18v with no 18v zeners fitted."

If you are running split +/-rails then no zeners are needed and 10R stay 10R.
Only if you were trying to drop say 48v (+/-24v) to +/-18v with 18v zeners fitted then the 10R would need to be made bigger ohms to set the current into the zeners.

2.:The new AMPHEAD II has 2 inputs per channel now,great.Can I add up another one or two channels by simply adding them via 10ks (I have the schematics already,but maybe others are interested too)?

Yes you can make like a normal 10k mix buss except this one is balanced so twice as many 10k. You will need 4 extra 10k for each stereo input.
This is what our STATTEN pcb and kit is made to do. You can ribbon cable lots of them together to make a volume & pan mix passive mixer into the AMP HEAD II.

3.:It took a while before I found out what the hell the pads labeled R/B/Y meant.After receiving the kit it was clear…..colours for the phones o/p.

Yes colour code for the prewired cables. R = RED TIP B = BLACK RING Y = YELLOW 0v

5.:For adding a mono/stereo/mute switch (DPDT toggle with center off position),can we use the procedure as described before in the old thread?
Link for reference:
viewtopic.php?f=2&t=165#p1430

Yes wired direct across the pot solder pads like original AMP Head. If you get null instead of mono reverse the 2 wires on one side of the switch.

6.:The build map is cool!

Udo.

8) :D
Joe :-)

JLM Audio

Capturing Audio without Injury

kante1603
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Joined: Wed Jan 20, 2010 6:12 pm

Re: AMP HEAD II Build Thread

Postby kante1603 » Tue Sep 12, 2017 11:32 pm

Wow,
that's a lot of info,thank you very much indeed!
I quickly digged a bit through your new small pieces of gear.....now that triggers a lot of thoughts and ideas in me :D
E.g.: Where can I ask things about the STATTEN,will there be a thread too?

Best regards,

Udo.

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Joe Malone
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Re: AMP HEAD II Build Thread

Postby Joe Malone » Mon Sep 18, 2017 12:57 pm

kante1603 wrote:Wow,
that's a lot of info,thank you very much indeed!
I quickly digged a bit through your new small pieces of gear.....now that triggers a lot of thoughts and ideas in me :D
E.g.: Where can I ask things about the STATTEN,will there be a thread too?

Best regards,

Udo.


HI Udo
STATTEN build thread started at the link below so you can ask questions there.
viewtopic.php?f=2&t=299&p=3759#p3759
Joe :-)

JLM Audio

Capturing Audio without Injury

kante1603
Posts: 85
Joined: Wed Jan 20, 2010 6:12 pm

Re: AMP HEAD II Build Thread

Postby kante1603 » Mon Sep 18, 2017 4:28 pm

Quick info:
I can confirm that wiring switches directly across the outer pot pins works well for both mono and mute functions.

Best regards,

Udo.

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Re: AMP HEAD II Build Thread

Postby Joe Malone » Mon Sep 18, 2017 4:39 pm

kante1603 wrote:Quick info:
I can confirm that wiring switches directly across the outer pot pins works well for both mono and mute functions.

Best regards,

Udo.


Cool yes only the pull pot direct switch pads are wrong for mono. So direct wiring will work perfectly :-)
Joe :-)

JLM Audio

Capturing Audio without Injury

AlexWelch
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Joined: Fri Mar 08, 2019 5:28 pm

Re: AMP HEAD II Build Thread

Postby AlexWelch » Sat Mar 16, 2019 12:46 pm

Hi Joe,

Build several of your kits over the years. Always a pleasure. Always delivered super quick too!

Just trying to work out how to hook up my power supply.

I'm using the SMPS 48v 315mA power. Trim pot turned down.

Am I right in assuming that the V+ from the power supply is hooked up to the V+ on the Amphead and then just ground to 0V? (Ground?).
Leaving the v- off?

I've got the 18volt zener's on the Amphead board. and I'm using the 5532 (if they are still alive).

Cheers,
A

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Re: AMP HEAD II Build Thread

Postby Joe Malone » Sat Mar 16, 2019 5:43 pm

AlexWelch wrote:Hi Joe,

Build several of your kits over the years. Always a pleasure. Always delivered super quick too!

Just trying to work out how to hook up my power supply.

I'm using the SMPS 48v 315mA power. Trim pot turned down.

Am I right in assuming that the V+ from the power supply is hooked up to the V+ on the Amphead and then just ground to 0V? (Ground?).
Leaving the v- off?

No. When the zeners are making the 0v the 36v power will be wired between +V & -V with nothing from the power supply going to 0v only audio grounds like XLR pin 1.

From first post on this page
"Can also be powered by single 12v to 48v power rail between +V & -V as long as 2 zeners rated at half the voltage used are fitted to the PCB.
(for example 2 x 24v zeners fitted to make +/-24v from one of our 48v SMPS supplies. Any DC connector must be isolated type.)"

I've got the 18volt zener's on the Amphead board. and I'm using the 5532 (if they are still alive).

Cheers,
A


If you wired it wrong at least one of the 10R would have burnt and maybe one of the zeners will be short. If that didn't happen then you are probably ok.
Joe :-)

JLM Audio

Capturing Audio without Injury

AlexWelch
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Joined: Fri Mar 08, 2019 5:28 pm

Re: AMP HEAD II Build Thread

Postby AlexWelch » Sat Mar 16, 2019 7:01 pm

ok, so I have the following setup:

power supply V+ V- to respective V+ and V- on board.
Live, Active and Earth to respective spots on the power supply

I've got an input with the tip to L+ ring to L- (and an SPDT switch to switch the ring to R+ for when I plug a stereo signal in instead of balanced). I'm also using the push/pull pot to switch for mono (I'm planning on using this for an in-ear monitor setup taking a feed from a mixing desk).

10R's metered fine. I can't smell any smoke and nothing looks to be burnt.

What I am hearing is a quiet bassy pop noise every second or so. Almost sounds like my power supply is tripping up on itself.

I thought I would consult here before proceeding.

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Re: AMP HEAD II Build Thread

Postby Joe Malone » Sat Mar 16, 2019 9:15 pm

AlexWelch wrote:ok, so I have the following setup:

power supply V+ V- to respective V+ and V- on board.
Live, Active and Earth to respective spots on the power supply

I've got an input with the tip to L+ ring to L- (and an SPDT switch to switch the ring to R+ for when I plug a stereo signal in instead of balanced). I'm also using the push/pull pot to switch for mono (I'm planning on using this for an in-ear monitor setup taking a feed from a mixing desk).

10R's metered fine. I can't smell any smoke and nothing looks to be burnt.

What I am hearing is a quiet bassy pop noise every second or so. Almost sounds like my power supply is tripping up on itself.

I thought I would consult here before proceeding.


If the green led on the power supply is going on and off it is in short circuit protection mode?
If so you probably have a dead short zener from previous wrong wiring or zener backwards or solder short.
Also check you have fully turned the power supply down to get 36 to 37v
Joe :-)

JLM Audio

Capturing Audio without Injury

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