RonRyan85

I see some factory built HEADPHONE AMPS pictured in an expensive
audio equipment catalog I get in the mail and they are $300. and up.
Seems like it would be a good project for electronic hobby people to
build themselves. (Small amp: 1 tube or a few transistors? ,power
supply ,2 earphone jacks and a small aluminum box/chassis.). Anyone
have a schematic or ever built one yourself?

JStrider

heres some info about the cmoy pocket amp

havnt built one myself but it looks like a fun project

http://tangentsoft.net/audio/cmoy-tutorial/

__________________
-=JStrider=-

~Clatto Verata Nicto

yatzr

my roommate and i have been getting ready to build some cmoy amps. you can actually get the op-amps for free from texas instruments as free samples.

__________________
Mechanical Engineers build weapons. Civil Engineers build targets.

RonRyan85

Jstrider and Yatzr:

Thanks for the great info! I will check out the websites and build one .
I have been transferring some music to my new Ipod from a collection
of old cassette tapes I have and need a small amp to boost the signals
from the output of my tape recorder/player.

RonRyan

jujueye

You might check out the HUGE discussion boards at Head FI . But beware: lots of opinionated people there (so unlike here *sigh*). Anyway, lots of good ideas and comparisons for you to read about!

An external amp for any portable unit is a great idea. You'll like the sound much better.

soundmotor

Also headwize.com

soundmotor

vanblah

Check out PAIA for all kinds of cool electronic projects. Mostly geared toward professional musicians ... but with a few modifications you could do almost anything:

www.paia.com

Their website is a little hard to navigate ... but just click around and you'll figure it out.

soundmotor

I built one hardwired on vectorboard over lunch last week. It used 2x 9V's & an AD712 opamp. The design varies somewhat from the CMOY in that I used the parts I had on-hand. Also, I used a dual opamp (AD712) and it is easier to build around than using 2x 8P cased ones (OPA134) as recommended in the CMOY article. You could use a dual OPA2134 instead.

All that aside, it makes a major improvement over the stock HP out a portable device. Using a set of large 300-ohm phones, it pushed them to louder levels than I would normally listen to. Also, off 2x 9V's its ran for nearly 7 hours before the output dropped. For static use, I bought a 16V computer wall-wart and I use it in place of the batteries.

Good luck, this is a great beginners project that has real merit.

soundmotor

soundmotor

That is the schematic I used for mine. I started with the 5532 as shown then ditched it for an AD712.

PAIA HP Buffer

I used the CMOY power supply schematic to power it and rewired it for a stereo volume control rather than mono as shown.

soundmotor

flat5

Another amp idea. Very powerful, simpler power supply.
Easy components to find/replace. Uses two LM386

http://www.minidisc.org/headbanger.html

soundmotor

I think if you counted up the parts, this would be at or close to the others in terms of solder connections. They are both op-amp based.

soundmotor

RonRyan85

Jujueye:
Thanks for the info and link to Headfi. I bought a new 20GB Ipod and
have been adding music tracks to it via some CDs, Itunes store and
old cassette tapes. I have used a pretty good 3 motor Denton tape
player and a small solid state amp to play the analog signals into my
laptop with Total Recorder program installed to turn the signals into
MP3 tracks. Works pretty good but I think it would be better if I had a
good fidelity 5 watt? headphone amp to do the transfer. Any thoughts
about this?

RonRyan85

Thanks to Soundmotor and all others who replied to my post.
I am checking out all of them. Thanks

soundmotor

Your welcome!

An aside, I had not built anything from solid-state parts for years when I decided to make one of these. I've been building with vacuum tubes for the last decade. I'd forgotten how simple & easy it is. If you've never done it before, take your time and double-check your connections. Also, don't get swamped by the audiofool hype that exists on many of the forums catering to this. When you get into these types of circuits, although you may be able to measure differences, it is unlikely you could hear them.

soundmotor

RonRyan85

Purchased a few parts today at the local Radio Shack and ordered the
Op Amps from Digi-Key Electronics. Will report back when I finish my
Headphone amp. ..........in case anyone is thinking of also building one.

flat5

Hello soundmotor, well you have built a Cmoy amp so you are loyal to them.
That's cool. What turns me off is the need for dual supplies.

I have used the LM386 amps. They are tough, reliable, easy to buy.
They do not require dual power supplies. They are made for battery operation, and low current drain.

From the data sheet:

General Description

The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.

The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

Features

Battery operation
Minimum external parts
Wide supply voltage range: 4V-12V or 5V-18V
Low quiescent current drain: 4mA
Voltage gains from 20 to 200
Ground referenced input
Self-centering output quiescent voltage
Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8Ohm, PO = 125mW, f = 1kHz)
Available in 8 pin MSOP package

Applications

AM-FM radio amplifiers
Portable tape player amplifiers
Intercoms
TV sound systems
Line drivers
Ultrasonic drivers
Small servo drivers
Power converters
---

RonRyan85, I don't understand why you think you need a 5 watt amp to transfer from tape to mp3? Why not go from line out on the tape player to line in on the soundcard?

One watt (RMS) is already way too much power for a single headphone amp.
0.089 watt to 0.238 watt is what most headphones are capable of. After that they are overloaded.
http://www.rane.com/pdf/note100.pdf

soundmotor

I wouldn't go so far as to say I am loyal to them. The HP amp I built is a hybrid of several designs not just the CMOY. The advantage of dual supplies, is linearity of operation for the device being utilized. With the micro performance levels these things have, any advantage is worth exploiting.

However, I have not built a LM386 based HP amp either, so I cannot comment on its merit. Although it uses capacitor coupling on its output (I am not a fan of that as it adds parts & puts one more thing in the signal path) I am sure it sounds just fine. But, you can build a dual supply quite simply from (1) 9V battery too. Take a look at the power supply for the CMOY here:

CMOY

For the one I built, I used 2x 9V batteries with my grounded connection being at the point the "+" of battery #1 to "-" of battery #2. Not a great deal of added complexity. Also, I was weighing the LM386 design you posted to the CMOY relative to the parts count & solder connections each has. To me they look to be near identical in that regard meaning neither presents a clear advantage in terms of how long it takes to build. Lastly, like the CMOY in the link above, the LM386 design you posted needs 2x single op-amp devices. I wired mine up for a dual 8P op-amp & thus reduced the parts count further.

Bottom line, there is no absolute here, just people sharing ideas on what worked for them. I'd recommend one more site for those inclined to build audio deivices for themselves:

DIY Audio

soundmotor

Soldering Advice: Don't hold the hot end!

flat5

Two 9 volt batteries can make a simple daul supply but if the batteries do not discharge at the same rate problems can ensue, depending on design..

If a circuit has a few more parts than another, I don't concider that fact so important.

I don't wish to debate headphone amps further.

soundmotor

I didn't realize we were debating. I thought we were exchanging information & letting others come to their own conclusions.



soundmotor

jujueye

Wow...I completely forgot I had posted here. Sorry for the wait.

Well, the only thing different about your two different amp possibilities would be input and output impedance, and impedance matching. I think that's probably really not something that we shoudl worry about...maybe a little to tweaky..!

BUT: how are you connecting these things, exactly? If you are using the speaker outputs from the amp to the laptop, you could have less-than-desireable results. I would imagine that the Denon would likely have a 2 volt output for a tape deck, and that should be enough of a signal for the laptop. An amp could easily supply too much voltage and could burn something up on your laptop. Just a thought: be careful!

Here is a simple test: take a one minute sample of music. First, record it with your current setup with the amp in line. Second, start a new recording without the amplfier, that is: plug the tape deck directly into the laptop, and record the same piece of music. Save both recordings to your desktop or wherever. Now, the most important part: Listen! Which one sounds better?

Have fun with it. I need to get my own casette deck out and find those favorites and get them on CD....thanks for the reminder!

One more thing: there is a place online called AudioAsylum. The have a PC Audio forum there. Some technical questions, some basic questions. If you get some time, browse the forum. Hell, sign up if you want! Good online info.

AudioAsylum PC Audio Forum

RonRyan85

[QUOTE=jujueye]


Here is a simple test: take a one minute sample of music. First, record it with your current setup with the amp in line. Second, start a new recording without the amplfier, that is: plug the tape deck directly into the laptop, and record the same piece of music. Save both recordings to your desktop or wherever. Now, the most important part: Listen! Which one sounds better?

Have fun with it. I need to get my own casette deck out and find those favorites and get them on CD....thanks for the reminder!



QUOTE]

Thanks for the reply. Yes ,you are right....I didn't need the little amp.
Another poster said the same thing. I tried the MP3 song transfers
with just a line output into my laptop and it worked a lot better. I'm
using TOTAL RECORDER to turn my old tapes into MP3 tunes and I
had forgotten to adjust the recording volumn in their program. Any
way ...seems like most of my Cds and tape tracks sound pretty good
to my ears from the IPod. That Ipod is pretty fantastic in itself. I
got the 20GB and did not want to spend the 300 Plus bucks for it
but I'm glad I got it.

OK on the forum...I've visited it a few times. I'll post a picture of
my headphone amp when I get it built. Sent off for the amp chips
and dual volumn control . All other parts bought from Radio Shack
and a electronics shop here.

jujueye

So which one are you going to build? I've got the itch to break out the solder gun myself!

RonRyan85

Hi Jujueye:
I downloaded the CHU MOY design (19 Pages !) and because it had so much
info on building.....I am building that one. Bought everything from Radio Shack
and Digi-Key.com. Bought the plastic box from a local electronics store here.
Will probably buy a better set of headphones now just to see if they sound
better than the ones I have now. (Koss TD/70 Digital). maybe I can go to the
Tweeter store (Home Entertainment) and ask them to show me all of their
headphones?)

jujueye

Excellent. I have heard it is a good one for the price. Plus, building it yourself is fun, and you can show people what you did! Yay! I'll take another look at it. Maybe I can build one, too.

jujueye

I started what we will call "the shopping experience" on May 23. In about a month, I had finally come up with the correct parts for the Mint amplifier. Why did it take so long? Because Tangent has some holes in his description on the site. For example, using the parts described will give a gain of 10 for the Mint. For Sennheiser, this is wayyyy too much. So I had to pore through the head-fi site and figure out what I really needed. He also leave out little details here and there. Most of the parts are listed, just not all. I think an extra web page with [i]complete [/] parts lists for a typical Sennheiser or Grado pair of headphones would go a long way.
I also caught site of a post where he seemed a bit irritated and said something about his website like, "...I thought it was pretty self explanatory." Oh well, mine is almost done. Had some parts that were backordered like wire and the case. It should be working by tomorrow night. Yay!

RonRyan...how did you fair?

RonRyan85

Hi Jujueye:
I did build the headphone amp but got in a rush to finish
so I think I might have criss-crossed a few of the op amp
wires and did not buy any carbon film resistors as the plans
specified so.......my amp does not work too good. I plan to
rebuild it again,but I've been having a lot of fun with my
iPod player and running the output into my old stereo
Carver receiver so it might take a while to rebuild.

(Remember
the old "Hands On Electronics" magazine? They use to have
bunches of cool electronics projects. I see one on the
racks of the book stores here called :"Volts and Nuts" but
never see too many good things in it. We have a shop here
called "Electronic Parts Outlet" that has lots of parts,
computer stuff and surplus junk where I spend a lot of my
money. Take care....

jujueye

Well, save for a few little case tweaks, mine is done. It worked from the first time I fired it up! Yay! The design of my case leaves the inside of the power switch without heat shrink tubing on it, so I need to swap out my 9v battery connectors for some that are capped. I don't want that battery lead to touch anything and short out this long project! Noooooo!!!! Anyway, I was totally amazed that it worked, and by the way it sounds pretty damn good. Far better than a $100 heandphone amp should! I wil let this break in for a year or so, then move on to the Pimeta.

Sure hope you can get yours up and running. Maybe a post on the head-fi.org forum and a few photos would help. The community there is pretty good for troubleshooting.

I don't remember Hands On Electronics. Sounds like fun.

Mr_Tickles

If you're still interested, take a look at:

http://focus.ti.com/docs/prod/folder...tpa6120a2.html

it should have plenty of oomph behind it. there's a reference shcematic in the datasheet as well.

Cheers

T

jujueye

Here are a few photos. The little Mint is working pretty good!

Front


Rear


Inside with foam backing on the bottom. All the cabling is routed in the grooves and covered with heat shrink. I saved some real estate doing this, and battery changes are pretty quick.


Finally, a shot of my Mint and his new buddy!

flat5

Good work, jujueye!

Would like to see pics of the board and with batteries, if you would like to show them.

jujueye

Thanks flat5. I've built some other small electronics before, but they always sucked. Then I fiddled with some tube audio and thoughy...now I'm getting somewhere!!! This particular project really got me excited aobut DIY audio.

Okay, here is a pic of the board. It's not my pic...or my board, but will give you a perfect example of it.


Two pics of the case with batteries. I added two 9v battery snaps so I can go longer between battery changes. I also had a pretty good scare when showing this off to a family member. He looked at it up, down and upside down. When I got inside to show him the details the battery was sitting on top of the board. Geez, it could have shorted something out! So I added some foam rubber, just like an old transistor radio. It is removable.



It's a pretty good fit for the Hammond 1455J case.

Here's a quick view of where the board sits in the front. The volume knob is soldered directly to the board, so the whole unit is right up there with it. I suppose one could not mount the volume knob on the board and just wire it up from a distance if you were really in a tight squeeze.

flat5

That was a fast responce to my post. :-)

If the amp goes "intermitant" in the future, see that the vol. control has not developed
bad connections to the PC board. It likely will happen after some time if the VC is the only mechanical connection holding the PCB to the box. Might take years though.

Looks really good. Enjoy!

jujueye

Thanks. Point well taken as I had not thought about that. I might be able to stretch it out even further, though. You'll notice on the last (crappydigicam) shot something yellow below the board. It's a bypass capacitor for the output caps seen on top (the round ones). The board is resting on the bottom of the case (on a trimmed-to-fit piece of plastic) and the bypass caps. Well, okay...it's actually resting on the caps and lots of resistor leads that poke through! This should keep it from moving around too much...hopefully.

Thanks for the comments! I really had a great time building it. Listening to it is great...but building it was just as much fun. I'll work with this one for a year or so, then move up to the next model.

EDIT: BTW: I'm so glad I posted the pics and stuff here. I posted similar information at Head-fi, but nobody said anything... Thanks for the ego-boosting comments. I love TFP!

flat5

Computer type standoffs would require holes and screws so that's no good.
However two little dabs of hot glue might hold the board in place. Will the glue stick to the box? If not, a pressure fit, using rubber or a foam will keep the board from moving.

Maybe all this is not necessary, though. Time will tell.

jujueye

That could be true. I mean, I don't plan on mountain biking with it...!

flat5

I'm thinking vibration. Walking, biking, car seat, putting down on hard surface.
All of this flexes the solder connections of 6 connections. A hairline crack will develop in time. But you are not going to the moon. Lives don't depend on these connections. It can be fixed.

In the 1960s, the 1/2 watt (or 1/4 watt, I don't know) resistors used by the military in some projects cost ten dollars each. Because of the testing of each one, or each production run, again I don't know. So a 2 cent resistor cost ten dollars. Mil spec.

jujueye

HOLY CRAP!

1_C_E_M_A_N

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OPA2134 @ $4.00
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jujueye

Hey 1ce, I won't be buying parts for a different amp until next year. Thanks, though.