Homemade Headphone Amplifier?

[Luke73]

Hi there everybody

I have a need for a small battery powered headphone amplifier so that I can practice in hotel rooms and late at night without disturbing others, and whilst I have found some that are available (the Cafe Walter looks excellent) I would like to build my own just for fun.

I have a little electronics knowledge, and good soldering and construction skills. I've built lots of kits, but have never considered anything more ambitious before.

Having done a little research, the Philips TDA7052 mono audio amplifier chip looks to be a good option.

Having read the data sheet I'm thinking I should be able to use it construct a simple headphone amplifier powered by a 9v battery. A mono input is good, and if I'm reading it correctly, I could use outputs 1 and 2 on pins 5 and 8 to drive the left and right sides of a pair of headphones.

I want it to be a no frills amplifier. I really don't want any EQ sections or similar on it. At most, perhaps a volume control. On/Off switching would be via the input jack.

Here's the data sheet for the TDA7052:

http://www.ortodoxism.ro/datasheets/philips/TDA7052_CNV_2.pdf

Would anyone care to take a look and comment on my plans?

Many thanks,

 

[Tony G]

It looks very feasible to me. Looking at the block diagram of the chip, I wonder where you planned on putting your volume control?

 

[Luke73]

I was thinking I could add an audio taper pot to the input at pin 2. Not sure of the appropriate value though.

Another idea I read about was a "level" switch rather than a volume control to cater for basses with higher outputs. To do this I would switch the input to a resistor to attenuate some of the input voltage before it gets to pin 2, or for a lower level bass, simply switch the level switch to allow the signal to pass directly to pin 2.

 

[fdeck]

The input impedance of the chip is 100k Ohms, so you could use a 100k audio taper pot to feed pin 2. It's important to follow the diagram, which shows that neither output terminal is grounded.

The chip looks like a snap to use.

 

[Luke73]

Thanks fdeck

Excuse my ignorance, but would you mind elaborating on the comment regarding the fact that neither output terminal is grounded, and what the implications are for connection to an output jack to be used with headphones?

Thanks,

 

[fdeck]

I'll do you one better and draw it up. Give me a few minutes.

 

[fdeck]

Hope this helps. Note that "BTL" in the data sheet refers to the same thing as a "bridged" power amp.

 

[seanm]

Here is the headphone amp I made for going to England. I ended up not going, but did build the amp. Even found a place that would rent a bass for the week.

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The schematic is a bit confusing since the output is in the middle and the inputs at the edges.

 

[Luke73]

Hope this helps. Note that "BTL" in the data sheet refers to the same thing as a "bridged" power amp.

Many thanks fdeck!

That's what I had in mind, but I would have connected the hadphones incorrectly. I appreciate the clarification.

I have the parts on order, and should have them in a day or two.

Another note...I have noticed on various schematics for similar amps, many people use a capacitor on the input to filter DC voltage.

Would that be necessary in this application?

 

[Luke73]

Here is the headphone amp I made for going to England. I ended up not going, but did build the amp. Even found a place that would rent a bass for the week.

Invalid Link Removed

The schematic is a bit confusing since the output is in the middle and the inputs at the edges.

Thanks Sean - looks great. How does it sound?

 

[fdeck]

Many thanks fdeck!

That's what I had in mind, but I would have connected the hadphones incorrectly. I appreciate the clarification.

I have the parts on order, and should have them in a day or two.

Another note...I have noticed on various schematics for similar amps, many people use a capacitor on the input to filter DC voltage.

Would that be necessary in this application?

It would not be a bad idea. Something like 0.1 microfarad, assuming a 100k volume control. Even a small electrolytic would be OK.

 

[Luke73]

Great I'll do that.

I notice in your drawing, you have ommitted the 100nf and 220 uf caps on the supply voltage, and the 5k resistor from the input voltage.

Are they not required?

 

[seanm]

Thanks Sean - looks great. How does it sound?

Very very clean.

If you think of making it, I would breadboard it first. Like I mention, I had to really reduce the gain for it to work with my headphones. You might need the gain back.

Also, if I was using batteries, I might not use the opamp to provide the Vref. It turns out this takes quite a bit of juice.

 

[fdeck]

Great I'll do that.

I notice in your drawing, you have ommitted the 100nf and 220 uf caps on the supply voltage, and the 5k resistor from the input voltage.

Are they not required?

Some sort of resistor to ground is probably needed, but I am assuming the pot does the job. I would put the 220 uF cap on the supply voltage, though it's not so crucial when running on battery power. The combination of 100 nF and 220 uF is an audio trick that purportedly deals with the non-ideal nature of an electrolytic capacitor, but is probably not worth worrying about here.

 

[seanm]

Many thanks fdeck!

That's what I had in mind, but I would have connected the hadphones incorrectly. I appreciate the clarification.

I have the parts on order, and should have them in a day or two.

Another note...I have noticed on various schematics for similar amps, many people use a capacitor on the input to filter DC voltage.

Would that be necessary in this application?

Passive or active bass? You shouldn't need a cap for a passive bass since there is no DC. For an active, a cap might not be a bad idea.

 

[Luke73]

I currently have a passive bass, but who knows - I may want to plug an active bass in at one time or another. I might also make one for my bass teacher, who uses an active bass.

As long as the cap on the input voltage line does not have an adverse effect, I should probably include it.

Regarding bread-board, I already have some on my bench waiting for the TDA7052 chip to arrive. I'll build it on the bread board and test thoroughly before I built a fully finished version. The parts should arrive tomorrow, or perhaps Monday.

Many thanks for the input everyone It's most helpful.

 

[Tim__x]

Here is the headphone amp I made for going to England. I ended up not going, but did build the amp. Even found a place that would rent a bass for the week.

Invalid Link Removed

The schematic is a bit confusing since the output is in the middle and the inputs at the edges.

Passive summing on the output?

Edit: Here, I whipped up what I think is a much better topology. Obviously it's not fully fleshed out, no bypassing is shown (nor power pins for that matter), virtual ground, input and output jacks, etcetera.

 

[Kazan]

Hi , I have been reading this thread and thought that I might like to follow your example , so I did a google search on the Philips TDA7052 chip and I found a list of kits to build small amplifiers . Please take a look and see which kit you would recommend .

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[Kazan]

Moved to proper forum

 

[WillPlay4Food]

Couldn't you get different headphones and use the iPod remote? Do iPods still come with the remote? Mine did, but I bought it in 2002 and I think iPods came with more stuff in the box at that time.