Help with adding headphone jack to speaker cab simulator

[njkmonty]

Ive tried scouring the internet to find how to apply a headphone jack.
Was hoping someone could tell me if my cut and pasting methods are sound or completely wrong  and if so  ,how to implement it.
the goal is to use it at night with headphones so other half doesnt get pissed!


here is what i came up with.
any help advice would be greatly appreciated!

[marcelomd]

Hi,
This will work, but may be a bit weak. I would use one opamp per side. Also, 470r may be too much.

I made one for me with a NJM4556 + 100r per side. I think I set the gain to 3x.

[mth5044]

There are a couple headphone amp schematics out there, check out DeadAstro's cab sim for one, and THCustom headphone amp for another.

[njkmonty]

There are a couple headphone amp schematics out there, check out DeadAstro's cab sim for one, and THCustom headphone amp for another.

DeadAstro's cab sim  was were i did the cut and paste!

[merlinb]

DeadAstro's cab sim  was were i did the cut and paste!

Your cut and paste is correct compared with the Astosim, so if it works for Deadastronaut it should work for you too. But if you have an extra opamp (why not use a dual?) then it makes sense to use both to get a bit more power. Remember to use an NE5532 and not a wimpy TL07x. Some 10k pull-down resistors after the output coupling caps would also be a good idea.

[marcelomd]

This is one I made a few months ago. It works well, but I would have done differently today.

[njkmonty]

ive order some TDA 2822M
i think i like the idea od incorporating TH Custom effects stereo headphone amp section.
however i dont want a mono /stereo switch
do i need to incorporate the tl074  section?
also i like the idea of having a haeadphones volume.
how would i connect it to my existing xlr output section?

[anotherjim]

Blame it on CMOY. Not even the well known audio line driver op-amps are really up to driving headphones, they have just been kludged into doing the job.
A small power audio amp probably ought to be better, but I have trouble suggesting any candidates. The choices we have in thru hole that can work off 9v are vanishingly small and the specs probably don't please audiophiles, which leads back to the CMOY designs.
The TDA2822M is probably a good choice, but is ( of course ) obsolete.

[njkmonty]

i ordered what i hope is the smd version?
TDA2822D

https://au.mouser.com/datasheet/2/389/tda2822d-957132.pdf


heres the previously mentioned one
TDA2822M
https://www.st.com/resource/en/datasheet/cd00000134.pdf

[287m]

why i suddenly remember marshall drp when read tda2822 chip?  must blame matsumin 

[marcelomd]

Hi,
The NJM4556 I used above is rated for 70mA. It does a good enough job even if not in parallel. Also, cheap. I found about it in a blog where the guy used proper engineering to make an opamp-based headphone amp, just to piss the hi-fi crowd.
Other than that, I can only think about a discrete design or something made for mobile gadgets.

[njkmonty]

below is where im upto so far implementing across between TH Custom effects Headphone super mini & Hifi Headphone amp, (both use the 2822 chip)
the only thing i feel i need now is guidance how to connect to the IC 4 section of the circuit in picture. preferably add a pot to adjust headphone volume.

any help please?

[anotherjim]

R31 and R30 become a dual gang 10k log pot with wipers to the amp inputs?

[merlinb]

Since it's a mono signal you don't need a dual gang pot. Just tie the chip's two inputs together and use a single volume pot.

[njkmonty]

something like this?
* do i include 10K resistor (R33)  or omit?
* do i have wiper 3 of headphone volume connect to pin 1 output  or  to + Input pin 3?
* Headphone volume pot value? 50kA, 100kA?

[merlinb]

something like this?

[anotherjim]

One of the pitfalls of those small amps in the datasheet circuit is fairly high gain, this one is near 40dB? It probably won't be happy when driven from line level.
So R33 might have to be there to pad down the maximum level. I'd want to breadboard it to find out or you can arrange your board layout to make it easy to fit a temporary R33 with a wired pot to find the best value for a permanent fixed R33.

Going from the volume pot wiper to the amp, the load resistance is going to mess with the pot taper. If we have to have the pair of 10k input pull-downs of the datasheet, a 10k log pot is going to feel that and then you also have a 3rd 10k R32.
I'm thinking the vol pot might be 1k log to reduce the loading effect on the taper. R32 isn't really needed at all, but one could be fitted as a safety to reduce popping noise if the pot wiper became disconnected, but it can be 100k in that case.

As with all chip amps, do make sure the power pin has plenty of bypass capacitor nearby. Datasheet shows a minimum of 10uF, but I'd go with more like 220uf.

[njkmonty]

Ive got the cab sim already out on a breadboard just waiting for TDA2822D  to arrive.

is this better?

[merlinb]

Ive got the cab sim already out on a breadboard just waiting for TDA2822D  to arrive.
is this better?

Yes. Although C28/29 serve no purpose whatever.

[njkmonty]

ok cheers , but why would TH Custom effects include them in their ...
HiFi Headphone Amp V3.1B

http://diy.thcustom.com/shop/headphone-amplifier-stereo-simulation-v1-1-pcb/#