DIY Headphone amp

I'd love to join you. But I must warn you, I don't know a thing!!

Sharukh...you think i do ?
Would love to have you in the team. And guess what....if it works out we'll make two, one for you and one for me.....
thats a promise

Manek.

Meesa interested But then, I know even less than you two

Why does a headphone require an amp ? Why not plug it in directly at the source, CDP or Tape Deck ?

Behram.

behram..good question

I want to use my tube pre with my headphones. My tube pre has an output impedance of 600 ohms and cannot drive my headphones of 30ohms. So once I have a decent head amp then i dont really have to worry about impedances much.

Secondly, my dvdp and cdp dont have headphone out. I finally want a tube head amp. I want to use the 6SN7 tubes I have for the same. They make awesome head amp tubes and have enough grunt to drive electrostats headphones if need be.

thirdly I just love the 6sn7 sound !

Fourth, I need to start small somewhere so why not a headphone amp ?

Can think of many other excuses but to be honest I just have the munchies to make something !

Manek.

Hey Guys, ANY way I can help, please let me know.

I am tied up this Saturday.

Friday evening or Sunday is fine with me.

Though sitting at a Restaurant with a Circuit diag, some sample components and a multimeter, could raise eyebrows and maybe even get us arrested as a Bomb making team !

Incidentally, I have an DIY Line stage that has Valves for the input, driven by a Class A MOSFET Output stage.

Wanna Connect an Input Volume control and suitable Headphone jack to see what it sounds like ?

You will have to bring yr H-phones... I have ipod phones and STAX Electrostats... Nothing in between ...

Hi Manek,

As far as I can follow, you are looking out for a unity gain buffer stage. It can be a simple emitter follower or an op amp buffer.

What I dont seem to understand is why should a valve unity gain stage sound better than a solid state one ? After all there is no amplification. It is just impedance matching you are looking out for.

Am I missing out on something ?

Behram.

Hi Behram,

Nothing is perfect... Even at Unity Gain.

Distortion & Noise do not necessarily co-relate to sound.

That is why different Op Amps also sound Quite different. ( Replace the Op Amp in your Pre amp - Its on a socket )

You will hear the difference even between different op amps.... leave aside a Valve and an Op Amp.

All this is excellent motivation for a DIY Headphone amp, No ?

Behram, Why dont you lead this effeort / project ?

You have years of Electronics, R&D experience...

Hi Amp Nut,

The Op Amps are not mounted on a socket, they are soldered. I remember mentioning it to you sometime ago. The two preamp boards are mounted on the main board via sockets. I did buy the two op amps before opening the top cover but could not replace them for this same reason.

I still am not sure what "difference" one expects to hear from a unity gain stage !

Behram.

Amp nut wrote

Behram, Why dont you lead this effeort / project ?

I would not mind, but you guys usually meet on weekends, and I am not available on weekends ! I do not mind week days.

Behram

Behram, Amp_Nut,

What are the good op-amps that are available in Mumbai...are there any good ones available....which will be a good one.

I'm looking at options for a Balanced TX module..

regards
Siva.

What are the good op-amps that are available in Mumbai...are there any good ones available

Send me your Wish List and I will revert.

Alternately call : Cirkit Electronics - Lamington Road, Mumbai (022) 2387 7777, or (022) 2380 0888,

NE5534 / TLO72 - Dual

LM387 (National Semiconductor, not sure of the number though)

TLO84 - Quad

LM301 - Single

By today's standards, these are all dated...

The 5532 and 5534 find their way into audio equipment even today ( Including MF most products ) but are considered phoo-phoo by others.

The TL 072 and 082 series have no short circuit protection besides a series ( built in ) output resistor and were hence liked by may.... but that was almost 20 years ago !

The 072 & 082 series have JFET inputs... therefore High Impedence and higher noise than Bipolar inputs.

Google for the spec sheet of the OPA 2134.

Its IMPRESSIVE. Used in MANY High End products - ML, Classe, etc. Its sadly not available in India.

For Siva's application, a high CMRR is required. Select accordingly..

THE OPA 2134 OP AMP

FEATURES
SUPERIOR SOUND QUALITY
ULTRA LOW DISTORTION: 0.00008%
LOW NOISE: 8nV/ÖHz
TRUE FET-INPUT: IB = 5pA
HIGH SPEED:
SLEW RATE: 20V/ms
BANDWIDTH: 8MHz
HIGH OPEN-LOOP GAIN: 120dB (600 Ohm)
WIDE SUPPLY RANGE: ±2.5V to ±18V
SINGLE, DUAL, AND QUAD VERSIONS
High Performance
AUDIO OPERATIONAL AMPLIFIERS


APPLICATIONS
PROFESSIONAL AUDIO AND MUSIC
LINE DRIVERS
LINE RECEIVERS
MULTIMEDIA AUDIO
ACTIVE FILTERS
PREAMPLIFIERS
INTEGRATORS
CROSSOVER NETWORKS

DESCRIPTION
The OPA134 series are ultra-low distortion, low noise operational amplifiers fully specified for audio applications.
A true FET input stage was incorporated to provide superior sound quality and speed for exceptional audio performance. This in combination with high output drive capability and excellent dc performance allows use in a wide variety of demanding
applications. In addition, the OPA134’s wide output swing, to within 1V of the rails, allows increased headroom making it ideal for use in any audio circuit.
OPA134 op amps are easy to use and free from phase inversion and overload problems often found in common FET-input op amps. They can be operated from ±2.5V to ±18V power supplies. Input cascode circuitry provides excellent common-mode rejection and
maintains low input bias current over its wide input voltage range, minimizing distortion. OPA134 series op amps are unity-gain stable and provide excellent dynamic behavior over a wide range of load conditions, including high load capacitance.

yep behram, you are right...looking for impedance matching....thats all, to begin with. I would think I would would be looking to build something with about 20K ohms of input impedance and 5 ohms output impedance to drive 30ohm headphones. Possible ?

finally....want to get to building a head amp which connects to a line source...SS and then tube.

Manek.

Manek, your requirements are quite simple. Only a single transistor emitter follower stage would be apt. Whatever negative contribution (distortion, noise etc)would hardly matter or be audible.

Scout around Bombay's Lmgn Road and pick up an Audio kit that has one such stage. This way you will have your PCB ready. You may omit the circuitry which is not of use to you. Check out VISHA kits opp the Lam Road police station.

Rgds. Behram.

Incidentally, I have an DIY Line stage that has Valves for the input, driven by a Class A MOSFET Output stage. Wanna Connect an Input Volume control and suitable Headphone jack to see what it sounds like ? You will have to bring yr H-phones... I have ipod phones and STAX Electrostats... Nothing in between ...

amp_nut, i will bring my phones....:-)
BTW what tubes are used with the line stage ?

Manek what headphones are you trying to drive? You could start off with a CMoy... its really easy to build, cheap and works very well for the amount of money spent.

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

thanks behram....

reinofchaos, I did check out cmoy earlier :-)

The cmoy uses an OPA2132PA Op Amp.

Any idea where I can buy it in India ?

Ofcourse any op amp will Work.... but sound RATHER different.

The OPA 2132 is the SAME OPA134 family ... OPA 2134 that I mentioned earlier today.

I have been wanting to buy this op amp for 2 years...

No idea locally but you can buy from www.digikey.com. However it helps if you buy 10+ instead of 1 since shipping charges are high. IIRC 2132 is a higher spec part than 2134.