[Tomo]

Hello,

I have been screwing around with THS4022, high bandwidth high speed amplifier. This is a voltage feedback amp.

(I have also posted this in HeadWize forum as well.)

This opamp is EXTREMELY sensitive to stray capacitance and inductance. Thus, all the connectors must connect perfectly. Also, the grounding must be perfect. There is absolutely no mergin for error for this opamp. Any error will result in hum or oscillation.

I used EVM from Texas Instrument. This allow me to just plug and chug the circuit with minor modifications. I am not so accustomed this type of opamp and I do not intend to push my luck this moment. Besides, 50 USD is far less compared to the cost of me actually making the board in super high precision. (My laziness is also significant factor in this decision but I will recommend against you using THS4022 haphazardly.)

The sound is extraordinary. Given that you have good equipment and good recording, THS4022EVM headphone amp sound heavenly. This is clearly faster amp compared to my other amps. The detail and accuracy is better than OPA134/2 and Szkeres'. It has surprisingly beefy and natural sound for a single opamp amp. However, this amp is hyper-sensitive to the qualities of recornding and the playback equipment. Bad recording and poor equipment is 100% sure ingredient to the PAINFUL experience literally (assuming you built the amp perfectly).

Battery operation is not recommended since grounding is not so perfect in that case. (Not for portable listening!!) This is definitely not happy with portable CDP in battery operation. Also, interconnect should be shielded. Ground loop stopper is an absolute requirement.

I have not added any volume or crossover networks to decrease any stray "whatevers." But I am very happy with it.

Tomo

P.S. This is a newbie-killer. Do not attempt this even if you have EVM. This project is for experienced DIYers only ... I am sorry. It's way too hard to deal with for new timers.

 

[topher]

Nice. Also a great idea to post to headwize too.

 

[Tomo]

Hello,

I have been running it continuously for last 24 hours.

I found the high is very smooth. I was expecting harsh high. It has very open sound; kinda eye opening.

I still like it ...

Tomo

 

[Tomo]

Hello,

I found something really cool. I can make TV Interference with this thang. So make sure you got Zobel Network!!!!

Tomo

 

[jteef]

Hello,

Tomo, you have said you don't like using ceramic capacitors. Did you use them for the zobel net? Do you have a zobel net on input and output?

how much gain are you using?

what do you mean by ground loop stopper?

jt

 

[Tomo]

Hello,

I never said I do not like ceramics. You must understand there is no BEST caps for everything. You must pick one that suit your specific purposes. For example, electrolytics should not be used for signal coupling but you should use these for PSU bypassing since they offer the largest capacitance.

I believe zobel network does extremely little to audio signals since the capacitor in the network is ~10Kohm at 20kHz and higher at lower freq. So audio signal will not see the zobel network at all. But I want to keep the freq at which zobel network start to kick in precisely around 1.6MHz; not 1Hz less. So I used ceramic from RadioShack. (Ceramics keep its capacitance and thus impedance at constain even at very high freq.)

I set my gain to 11. This is different from default at which the evaluation module comes. So you will have to modify the module properly. The default is 21. This gain is not too large.

Ground loop stopper is a circuit devised by Mr Meier for his amp. (He calls it so, I thought.) This is simple device that connect the amplifier ground to power supply ground/transformer ground. This is very necessary since stray current that is left in the circuit can flow all over the place causing oscillations and other baddies.

Tomo

 

[aeberbach]

There's nothing like an amp that goes to 11

 

[Tomo]

I forgot to mention that there are three types of THS4022 available. One with PowerPad, one without, and one manufacture dependent DIP. The max possible power dissipation is different for different types. In fact, the max power diss for PowerPad Version is 2.14Watt while the other is below 1Watt.

TOmo