Beware of two things with this circuit:
1. You must use NJM4556 because it is designed for headphones. It can give 70mA at 150 Ohm loads. No other opamp can do that with the same performance.
2. I do not know how hard can NJM4556 be loaded, which is the minimum headphone impedance before the distortion starts to go up. I am not sure that this amp is suitable for 30 Ohm headphones.
1. You must use NJM4556 because it is designed for headphones. It can give 70mA at 150 Ohm loads. No other opamp can do that with the same performance.
2. I do not know how hard can NJM4556 be loaded, which is the minimum headphone impedance before the distortion starts to go up. I am not sure that this amp is suitable for 30 Ohm headphones.
May I suggest a very simple and exceedingly good performing headphone amp using the THAT1646 driver IC? It was designed by Wayne Kirkwood (@Mediatechnology). Layout by Prasi and Gerbers available. Literally, add two BD139's and BD140, and a few resistors to an ultralow THD driver IC and you have a HPA that can drive any impedance cans in push pull Class A DC coupled with zero offset.
Simple Class A Headphone Amp Using THAT1646
Built up:
Here is 1.0Vrms into 50ohms FFT (where's the distortion?):
Simple Class A Headphone Amp Using THAT1646
Built up:
Here is 1.0Vrms into 50ohms FFT (where's the distortion?):
I found relevant info in the legendary O2 thread which also uses NJM4556. NJM4556 "will drive nearly any headphone from 16 - 600 ohms to "live" levels." So my reservation about drive capabilities of NJM4556 are unfounded.
See first page of The Objective2 (O2) Headphone Amp DIY Project
See first page of The Objective2 (O2) Headphone Amp DIY Project
Im adding it to my list and will bookmark that topic, thanks.And yes my plan is to use njm4556ad or add if i can find it.
I have extra PCBs and can give you one if you pay shipping.
Yes, for good reason. A PCB isn't flexible so it can't pass through the USPS's letter sorting machines like paper documents can.
So your $13 quote is spot on!
I sell quite a few PCBs for different projects and it's difficult for folks outside the U.S. to understand that shipping is probably going to cost more than the PCB.
After reading several of your posts here, I see that you're quite content on using the infamous JRC NJM4556 op-amp for whatever reason.
I've tried that op-amp in numerous applications and unlike ivanlukic, I found its SQ to suck moose balls in all the preamp/HA applications I've tried it in.
Just FYI, most DIP-8 op-amps aren't designed to "drive" headphones as ivanlukic is trying to make you believe.
That job is left up to higher current buffers or at the minimum a CFA op-amp.
This is something that you'll have to find out for yourself.
ALL the better HA amps will usually use discrete devices(not op-amps) in their output stage in order to have enough balls(read current) to drive lower impedance cans.
One such example is the Schiit Magni 3, which sounds incredibly good for a ridiculous price of $99 plus shipping.
NO NJM4556 design can surpass it's SQ.
Take care and good luck with you layout. After all...we all have to start somewhere when it comes to layout design.
I use absolute headphone classics, Sennheiser HD424 (2000 Ohms) and AKG K141 Monitor (600 Ohms). These headphones are old and are designed to work well with opamps like NJM4556. NJM4556 drives both without any problems and the sound is excellent. But Wayne Kirkland's HP amp will probably be great for all headphones, including latest models which tend to have impedance of 30-120 Ohms.
Yes, for good reason. A PCB isn't flexible so it can't pass through the USPS's letter sorting machines like paper documents can.
So your $13 quote is spot on!
I sell quite a few PCBs for different projects and it's difficult for folks outside the U.S. to understand that shipping is probably going to cost more than the PCB.
After reading several of your posts here, I see that you're quite content on using the infamous JRC NJM4556 op-amp for whatever reason.
I've tried that op-amp in numerous applications and unlike ivanlukic, I found its SQ to suck moose balls in all the preamp/HA applications I've tried it in.
Just FYI, most DIP-8 op-amps aren't designed to "drive" headphones as ivanlukic is trying to make you believe.
That job is left up to higher current buffers or at the minimum a CFA op-amp.
This is something that you'll have to find out for yourself.
ALL the better HA amps will usually use discrete devices(not op-amps) in their output stage in order to have enough balls(read current) to drive lower impedance cans.
One such example is the Schiit Magni 3, which sounds incredibly good for a ridiculous price of $99 plus shipping.
NO NJM4556 design can surpass it's SQ.
Take care and good luck with you layout. After all...we all have to start somewhere when it comes to layout design.
It is simplest design to start, that is why I have chosen it. It was this or CMoy, and as I understand they are very similar so I have chosen simpler, I understand it is nothing special. My thinking is that I must build something and to start listening it, I must get some experience. I can order some more complicated boards and start assembling them but I don't want to skip steps. Parts for this are very easy to find and I will assemble i without any problems then listen to it for week or so to get reference, starting point. Later I will see if new amp is better do I like it or not.
Yes, for good reason. A PCB isn't flexible so it can't pass through the USPS's letter sorting machines like paper documents can.
So your $13 quote is spot on!
.
I buy in pcb's from China and they cost $5 for 10 pcb's and $30 for shipping.
Elecrow
2layers PCB 1.6mm 100mm x 100mm 10pcs Green
PCB Qty :
10pcs
Layer :
2layers
PCB Thickness :
1.6mm
Dimensions :
100mm * 100mm
Castellated Hole :
No
PCB Color :
Green
Surface Finish :
HASL
Copper Weight :
1oz
Text Color :
White
Different Design :
1
Subtotal $4.90
Shipping & Handling (Select Shipping Method - Registered Airmail) $9.48
Grand Total $14.38
2layers PCB 1.6mm 100mm x 100mm 10pcs Green
PCB Qty :
10pcs
Layer :
2layers
PCB Thickness :
1.6mm
Dimensions :
100mm * 100mm
Castellated Hole :
No
PCB Color :
Green
Surface Finish :
HASL
Copper Weight :
1oz
Text Color :
White
Different Design :
1
Subtotal $4.90
Shipping & Handling (Select Shipping Method - Registered Airmail) $9.48
Grand Total $14.38
Registered airmail is slow and that's why shipping is only $9.48.
"XRK" was the one offering you a THAT board(s) for the ridiculously low shipping price of $2 as a "first class letter".
As I noted above, I already know the high shipping cost for a board from the U.S. to some foreign country from selling many of my own PCBs.
In addition, customs forms usually have to be filled out for international shipments.
When it's all said n' done, it's not worth my time and effort to send my PCBs to foreign countries.
That's why I only send my boards to folks within the U.S..
Good luck with your NJM4556 op-amp HA design!
LOL...it shouldn't take you long to realize how the SQ sucks moose balls compared to a discrete design like the Schiit Magni 3 should you decide to do any real comparisons.
Now...let's bust out the moonshine and soldering iron and build something!
Good luck!
ammel,
You don't have to go to the Post Office to send a letter to foreign country. All you have to do is to check postage rates for the weight of your letter, buy postage stamps, glue them to your letter and throw it in the nearest letter box. That way you won't be annoyed by the postal clerks. I always use this method because in Serbia everything concerning Post functions the same way as in US. Nobody can force you to bring the letter to the Post Office. The weight of the letter can be up to 2 kilograms! The only limitation is the size of letter box slot. But all envelopes with PCBs can pass through letter box slot.
You don't have to go to the Post Office to send a letter to foreign country. All you have to do is to check postage rates for the weight of your letter, buy postage stamps, glue them to your letter and throw it in the nearest letter box. That way you won't be annoyed by the postal clerks. I always use this method because in Serbia everything concerning Post functions the same way as in US. Nobody can force you to bring the letter to the Post Office. The weight of the letter can be up to 2 kilograms! The only limitation is the size of letter box slot. But all envelopes with PCBs can pass through letter box slot.
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