# Headphone Amplifier?



## G.G. (Sep 23, 2022)

Is there is already a discussion thread for the new HeadPhone Amplifier project? If not, can someone fill me in on what it's all about?


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## spi (Sep 23, 2022)

I'm so happy to see it, been wanting one for a while.  I'm watching this thread too.

My question is: if I'm running pedals straight into this headphone amp, does it need a cabsim (like Unicab) to sound good, or does it sound good on its own?   Without some eq filtering, straight signals can sound crap--but maybe it has adequate EQ built in.


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## deft (Sep 23, 2022)

I have another Q, what exactly is the stereo 'spread'? Common trick with modellers is to delay one ear by 10-20ms but I'm assuming it's not that


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## Bricksnbeatles (Sep 23, 2022)

deft said:


> I have another Q, what exactly is the stereo 'spread'? Common trick with modellers is to delay one ear by 10-20ms but I'm assuming it's not that


I’m guessing it does the classic stereo spread trick of changing the EQ in the two channels slightly. Cut bass and treble a tiny bit in one channel, cut upper mids in the other channel, and you’ve got a quick and easy stereo spread


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## Mentaltossflycoon (Sep 23, 2022)

If it's related to the mxr project that's out there, it definitely benefits from the unicab. I boxed them together recently. I also enjoy it with the rog ginger and the aion ts-50 I completed last night (build report coming when it's boxed). I'm hoping it's a departure from the mxr as it is easy to fart out with bass. Fingers crossed for some headphone beano.


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## Robert (Sep 24, 2022)

This one is a basic headphone amplifier.

It's not related to the MXR, it uses a pair of LM386's.

I was pleasantly surprised with how nice it sounded playing my guitar plugged straight in, but you'll likely want some sort of amp/cab sim or at the very least EQ if you're planning to do any serious practicing with it dirty.

The stereo spread was inspired by the spread effect in the DSM Simplifier which introduces a phase shift on one side.  It enhances the sound enough that I can't imagine ever turning it off.  


If you're wanting all the bells and whistles (amp sim, cab sim, true stereo, etc) you'll want to hold off a bit, but if you just want a way to drive headphones from your pedalboard for practicing quietly or testing pedal builds this should work quite well.


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## fig (Sep 24, 2022)

Robert said:


> if you're planning to do any serious practicing with it dirty.


well duh. 🤣


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## fig (Sep 24, 2022)

That reminds me...I ran the Rockman into a Parenthesis Rat-only, as my rat doesn't have any clipping options...anyway....I found a pretty cool arrangement that bleeds some pretty sweet sustained harmonic toppings to the tasty treat...it took some futzing with the amp, pedals, and guitar....so probably wasn't worth it, but it sounded pretty slick.


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## Nic (Oct 10, 2022)

@Robert Any chance you have some docs about this, still waiting for mine to show up in the mailbox and wanted to order some parts. Was wondering about some weird values or what pot to order... can't wait to try that one.   Thanks


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## Robert (Oct 10, 2022)

Headphone Amplifier
					

Headphone Amplifier  Drill Template - Revision 1 Drill Template - Revision 2




					forum.pedalpcb.com
				




BOM and drill template.    If your order was placed before today you have Revision 1.

The only difference between the two revisions is the LED placement and a pair of 100R current limiting resistors were removed in Revision 2.


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## Nic (Oct 10, 2022)

Yep, rev.1

Good, already need those 100r, those could be bypassed ?


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## Robert (Oct 10, 2022)

Yep, you can jump them with wire if you'd like.


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## Nic (Oct 10, 2022)

Ok, thanks again!


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## EGRENIER (Oct 26, 2022)

@Robert and others, a couple of questions on this project:

1- Would it work for a bass ?
2- Would there be a few mod to run a bass ?
3- What if I was to connect a second jack for an auxiliary input straight to in/gnd , a way to plug you phone and play a backtrack ?

Thanks….


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## Nic (Oct 26, 2022)

1. That's what I plan to use it for. 
2. I think it's meant to be polyvalent... ? 
3. Good idea, myself I planned on doing it on the output for 1/4 and 3.5mm


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## EGRENIER (Nov 2, 2022)

Nic said:


> 1. That's what I plan to use it for.
> 2. I think it's meant to be polyvalent... ?
> 3. Good idea, myself I planned on doing it on the output for 1/4 and 3.5mm


Interesting, so you do not think the sound need to be amplified and joined to the volume control ?  Any specific reason ?

I'm also thinking of a MH-M18 Bluetooth module, just not sure if the PCB located in a aluminum enclosure would require an external antenna...


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## Nic (Nov 2, 2022)

My plan on the output is to have a dpdt to select my output ... I don't know if it's better or not, but hey, one more switch 
On the other hand, I'm interested in mixing an auxiliary input, but my guess is that it would need at least a blend pot... I'm not experienced enough to know how to do it the right way.


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## Nic (Nov 2, 2022)

But for now, I've received my missing parts to complete this PCB, only to find out... no DPDT, I'm almost sure I had a few in my cart, but maybe I removed them because I planned on restocking later for my other pending builds.


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## EGRENIER (Nov 2, 2022)

Nic said:


> My plan on the output is to have a dpdt to select my output ... I don't know if it's better or not, but hey, one more switch
> On the other hand, I'm interested in mixing an auxiliary input, but my guess is that it would need at least a blend pot... I'm not experienced enough to know how to do it the right way.


For the auxiliary input, I think you could control the blend by using the volume of your device.  Once you have parity, the volume knob of the pedal would increase both equally if you connect the auxiliary to the input of the amp.  If you connect the aux to output, then blending would have to be done each time you change the pedal output volume...

That's my thought anyway...


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## Nic (Nov 2, 2022)

That make sense using the phone volume on the input.
I may not have been clear about my intentions on the output. I will not add an auxiliary on the output, just the ability to plug cheapo earphones if that's all I have available at the moment... wife sometime steals my good headphones.


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## RFreeman (Nov 14, 2022)

Do all the electrolytic caps need to be 16v? I have all but the 220u, but they're rated between 35v-63v.


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## Nic (Nov 14, 2022)

I'm almost certain I used bigger values higher voltage rating, as long as they fit where you need them.


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## DAJE (Nov 15, 2022)

RFreeman said:


> Do all the electrolytic caps need to be 16v? I have all but the 220u, but they're rated between 35v-63v.


That's a *minimum voltage* rating on the PCB. You can exceed it as much as you wish, as long as the cap will physically fit. Higher rated caps are physically bigger, as @Nic says above.


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## RFreeman (Nov 15, 2022)

Thanks. The caps I have do fit.


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## Laundryroom David (Nov 15, 2022)

Nic said:


> That make sense using the phone volume on the input.
> I may not have been clear about my intentions on the output. I will not add an auxiliary on the output, just the ability to plug cheapo earphones if that's all I have available at the moment... wife sometime steals my good headphones.


This is why I sleep with my Grados instead of my wife.

wait that sounded wrong


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