Sonic Headphone Impact-T-amp

[Iron_Dreamer]

Quote:

Originally Posted by eweitzman Most excellent! Someone with access to a good HF microphone! Please keep us posted about what you find.

Please do, I'll be very interested in the results as well, because I'll be darned if Tamp/balanced stock cable sounds better than DAC1 amp/unbalanced Zu cable to me right now

 

[Earwax]

I cobbled together a cable for HD580s using silver-plated copper wires and stuck the raw wires into the speaker terminals along with a 4.7 Ohm resistor bridging the hot & cold terminals.

I can't say I'm overly impressed right now. The detail and clarity is remarkable, but there's no presence, no guts to the music (if that description makes any sense).

 

[cosmopragma]

Quote:

Originally Posted by blumenco look at the irrisistable acronymn: S*H*I*T if we can develop this together, it will also help to solidify the clearly superior technology (and sound) of the digital switching amplifier. it is freakin 2005 where the hell is my space age for the masses!???!!?!!!

Yeah!
Finally Thinkgeek managed to ship my 2 amps yesterday, should be here within a week.I'll gladly mod these thingies into any direction.
There's already a bunch of germans experimenting with this cheap toy, usually for the purpose of driving the K1000.
Ironically I've started this german FOTM a few weeks ago by mentioning the promising capabilities of the T-amp in a K1000 related thread over at a german HiFi-forum, , and personally I got none yet.
Oh well.......

 

[saint.panda]

Quote:

Originally Posted by cosmopragma Yeah! Finally Thinkgeek managed to ship my 2 amps yesterday, should be here within a week.I'll gladly mod these thingies into any direction. There's already a bunch of germans experimenting with this cheap toy, usually for the purpose of driving the K1000. Ironically I've started this german FOTM a few weeks ago by mentioning the promising capabilities of the T-amp in a K1000 related thread over at a german HiFi-forum, , and personally I got none yet. Oh well.......

Mine is running sweetly already

However, I've gotten really interested in this CEC HD 53 which seems to get a lot of attention and whole-page coverings on the German forum.

 

[cosmopragma]

Quote:

Originally Posted by blumenco So i am considering making a pretty straight forward adaptor for the phones. it will consist of a stock sennheiser cable, cut to get four wires, and six ohn resistors across the positive and negatives of the wires (essentially parrallel to the transducers). then i will make some nice little connectoid leads for them and plug them in. then I will bring them to a high frequency mic and see if that 53000 hz is coming through.

As far as I understand the behaviour of the T-amp is different into different loads.53000 kHz is the peak for the 120 Ohm load of the k1000, maybe eweitzman finds the time to rerun the simulation for an impedance of 300 Ohm.

Btw, on Friday I've written an email to the Austrian AKG labs.
I've explained the issue and asked them to look into their archives for ultrasonic response measurements and graphs of the actual impedance/frequency relationship.

Fortunately my german is way better than my english.

 

[RonD2]

Quote:

Originally Posted by cosmopragma Btw, on Friday I've written an email to the Austrian AKG labs. I've explained the issue and asked them to look into their archives for ultrasonic response measurements and graphs of the actual impedance/frequency relationship.

Do you happen to know what the pcb boards in the K1000s do? If not, could you ask the Austrian AKG lab?

Thanks!

 

[Edwood]

I'm borrowing a Sonic Impact-T-amp (courtesy of Iron_Dreamer). It sound weird. Like the phase is messed up. I've tried different combinations of reversing polarity of left, right, and both channels.

It just sounds well....off.

The dynamics are fantastic, though. Really gives some oomph to the drivers.

-Ed

 

[NeilPeart]

Ed,
Make sure you hook the T-amp this way:

 

[Earwax]

Quote:

Originally Posted by Earwax I cobbled together a cable for HD580s using silver-plated copper wires and stuck the raw wires into the speaker terminals along with a 4.7 Ohm resistor bridging the hot & cold terminals. I can't say I'm overly impressed right now. The detail and clarity is remarkable, but there's no presence, no guts to the music (if that description makes any sense).

I ripped apart my frankenstein and rebuilt it and I'm much happier with the sound this time. (Different source, too.)

I still have the 4.7 Ohm across the terminals (in parallel with the headphones) and I added a series 47 Ohm on the positive lead. I'm still not sure it's a giant killer yet, but maybe with a little more tweaking of those resistor values...

 

[breez]

Here is panomaniac's measurements at diyaudio. Notice the bass roll-off

http://www.diyaudio.com/forums/showt...threadid=50779

 

[eweitzman]

Quote:

Originally Posted by cosmopragma maybe eweitzman finds the time to rerun the simulation for an impedance of 300 Ohm.

Just about the same as 120 ohms. At 32 ohms for Grado fans, the peak is 6db at 50kHz.

Quote:

Btw, on Friday I've written an email to the Austrian AKG labs.

Wonderful.

BTW, I read the document on the Canadian government's website.
I found an interesting result mentioned in the review: exposure to 120 db ultrasonic noise at just over 20kHz caused temporary hearing losses at the subharmonics of 4kHz, 8kHz, and other frequencies (more or less, I'm working from memory here...) Though we're not talking about precisely these numbers, so I extrapolate gingerly, it's possible that ultrasonic noise at 30kHz could cause temporary loss at 3.25kHz, 7.5kHz, 15kHz, impacting our listening experience temporarily, if not our hearing!

- Eric

 

[Edwood]

Well, bad news. I've been hearing crackling distortion and break up of signal in the left channel of my K1000 with the Sonic Impact T-Amp.

Not sure what's causing it, and it only happens in particularly loud parts of songs, but it doesn't happen all the time.

I measured DC offset for the Sonic Impact T-Amp.

0.002vdc Left rises to 0.028vdc once music is playing and stays around that level even when music is stopped.
0.008vdc Right rises to over 0.012vdc

The Left channel's DC offset is pretty high. But it's not horrible either.

I've been hearing that buzzing, crackling distortion and signal break up even with my Grace m902. But it's going away. I looked carefully under a light to see any stray hairs that may have got on the driver, but I didn't see any. Going to give the drivers a gentle blast with compressed air just to make sure.

I hope the Sonic Impact T-Amp hasn't damaged my K1000's. I've barely used them with the Sonic Impact.

-Ed

 

[Edwood]

Duh.

I think it may be a cable problem, it's only present with the unbalanced analog output from my RME digi96/8 PAD. I think it's a loose cable or something. I unplugged everything, and plugged back in, double checking solid connections.

So far no problems.

I still don't like the DC offset from the Sonic Impact T-Amp.
I suppose a small coupling cap will fix it......

-Ed

 

[RonD2]

Quote:

Originally Posted by Earwax I ripped apart my frankenstein and rebuilt it and I'm much happier with the sound this time. (Different source, too.) I still have the 4.7 Ohm across the terminals (in parallel with the headphones) and I added a series 47 Ohm on the positive lead. I'm still not sure it's a giant killer yet, but maybe with a little more tweaking of those resistor values...

FWIW, I've tried 4, 6 and 10 Ohm resistors and definitely preferred the 4. This is using a Clari-T version of the T amp into K1000s with the pcb boards removed.

 

[CSMR]

http://www.michael.mardis.com/sonic/images/TA2040.gif
This is the sonic impact circuit.
I wonder if it can be easily transformed so that it is no longer bridged.
Connect OUTM1 to PGND1 instead of 28, and similarly with OUTM2. Would that work?