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Old 13th April 2005, 12:01 PM   #11
opentop is offline opentop  Netherlands
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Quote:
Glad you like it too. What's your experience on clipping /ringing in your setup ? nice system ! What's the efficiency of those speakers? What amp did you normally use?
I experience no clipping at all. But then again, I use a pre-amplifier.

That said, I once connected the T-Amp directly to my cd-player. Again there was no clipping, though I had to turn up the volume to approximately '2 o' clock'. I play in a small room (only 3 x 4 meters).

I don't know the effiency of my speakers. I only know that the next model Magnepan developed, the 0.6, has an effiency of 86 dB. That's not much, but apparently enough.

Before the T-Amp I used a Audio Analogue Donizetti power-amplifier (2 x 50 W).



Good luck with your Amp3!
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Old 13th April 2005, 12:46 PM   #12
dgo is offline dgo  Netherlands
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Quote:
Originally posted by opentop


I experience no clipping at all. But then again, I use a pre-amplifier.


Good for you that it doesn't as it's not pretty when it does.

With very dynamic music, the t-amp will start to distort heavily and
clip eventually when driven to its limits. This especially seems to
happen with overall loud, dynamic music on sustained notes (like a
violin in full blazing orchestra striking out in a solo or on very
dynamic sustained vocals)

At my setup approx. with the dial from 1 o'clock and beyond,
depending on the input signal, I reach clipping levels. That's at 8 ohm 89dB Hepta's.

When you reach the clipping level, seems to depend heavily on the
efficiency of the speakers. The people I've heard where it doesn't
clip or a lot less, use very efficient speakers. Perhaps your speakers
are more efficient than you suspect?

I don't understand what the influence of a pre-amp on the clipping
level of the SI would be, can you explain please?

By the way, I'm listening in a fairly smal room as well (6x4) and it's
quite easy to stay below clipping levels, so it really isn't a big
problem except with some music parts.

Some good measurements at Michael Mardis' site about the clipping
behaviour http://www.michael.mardis.com/sonic/sonic3.htm

[/QUOTE]


Quote:
Originally posted by opentop
Before the T-Amp I used a Audio Analogue Donizetti power-amplifier (2 x 50 W).
How does it compare to the SI?


Quote:
Originally posted by opentop
Good luck with your Amp3!
[/QUOTE]

Thanks! I'm waiting for some components and then I *hope* it will
play Can't wait to hear it.
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Old 13th April 2005, 02:54 PM   #13
BWRX is offline BWRX  United States
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Quote:
Originally posted by dgo
At my setup approx. with the dial from 1 o'clock and beyond,
depending on the input signal, I reach clipping levels. That's at 8 ohm 89dB Hepta's.

When you reach the clipping level, seems to depend heavily on the
efficiency of the speakers.
That sounds about right. The onset of clipping on a stock SI should be right around 1 o'clock with a 1Vrms sine wave input. From my experience those are pretty good listening levels with 89dB speakers in a small room.
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Old 15th April 2005, 08:49 AM   #14
opentop is offline opentop  Netherlands
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Quote:
I don't understand what the influence of a pre-amp on the clipping level of the SI would be. Can you explain please?
Well, using the SI this way, it serves as an power-amplifier (I know, it sounds strange with this little bugger). The pre-amplifier give it extra juice, so I can play louder, with the volumeknob on maxium. I control the volume via the pre-amplifier.




Quote:
How does it compare to the SI?
I am not sure yet (because I use it in a setup wtith pre-amplifier, DAC and Ultracurve). Bit I like to think there's a little more detail with the SI.
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Old 15th April 2005, 12:48 PM   #15
Pano is offline Pano  United States
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Quote:
Originally posted by opentop

The pre-amplifier give it extra juice, so I can play louder, with the volume knob on maxium. I control the volume via the pre-amplifier.
This is often the case. A buffer stage (e.g. preamp or line driver) will make a power amp sound better, often louder or stronger. If it does, then you can suspect that your source is not strong enough to drive the input of the power amp. Not uncommon.

But the preamp can not raise the power amp clipping threshold or output power, only a better and/or higher voltage power supply can do that.

FWIW, the stock Sonic has a somewhat low input impedance meant to be driven by a headphone jack. Some CD players may sound a little weak when driving it. YMMV.
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Old 15th April 2005, 01:21 PM   #16
opentop is offline opentop  Netherlands
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Quote:
But the preamp can not raise the power amp clipping threshold or output power, only a better and/or higher voltage power supply can do that.
Okay, thanks for the info. But like I said earlier, I haven't experienced any clipping whatsoever. My listening room is 3 x 4 meters only. So I don't have to play loud: with preamplifier, the volumeknob of the preamplifier on 10 o' clock, with only the SI, the volumeknob on 12 o' clock (higher is too much for my ears).
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Old 15th April 2005, 06:51 PM   #17
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I just finished the first round of mods on one of my SI boards and just wanted to give a few impressions on the sound. First the mods:

1. Removed the 100 pf caps to ground and left the pads "open".
2. Removed RO1 and R02 and left their pads open.
3. Removed the volume pot header.
4. Replaced the 330uf filter cap with 660uf panasonic from Digikey.
5. Removed L1 and L2 and jumpered the pads.
6. Removed C3 and C4 and did the same.
7. Ran 2.2uf poly's to the audio input thru holes where the volume pot header used to be. I left the other two legs of the poly's dangling off the edge of the board.
8. soldered the remaining legs of the input caps to the wipers on an Alps blue velvet 50K pot.
9. Replaced R4 and R5 with 20K res.
10. Replaced all stock wires with 22 guage stranded copper wire.
11. Added a "Mexx" heatsink

I haven't had a chance to box this thing up in a chassis yet but I should be getting to that in the next day or so. I mainly wanted to do a smoke test prior to mounting in a chassis but It sounded so nice that I decided to let it burn for awhile.

I ran the SI off a 12V SLA 7AH battery that I scrounged from a defunct ADS burgler alarm that my condos previous owners left behind.

My first smoke test was a pretty intense moment. I hooked the modded SI up to an el-cheapo bookshelf system that I recently inherited. The speakers are four ohm'ers that sound like everything is being played thru a bowl of oatmeal.. so I figured no big loss if I blew 'em out during the test. I also ran a mini stereo jack to RCA adapter cable from the headphones jack on this system to the SI.

Powered everthing up...no smoke! but no right channel . So I stopped and powered up my O-scope and did some checking around. With the board powered down I inserted a .8 volt signal into each of the input caps and managed to trace the problem to R4...yep, bad solder joint. So I resoldered that puppy in and fired the amp up...Good sound from both channels.

So I unplugged it from the cheap bookshelf system and hooked the SI up to my Dynaco A25's. I fed the outputs from my Technics CD jukebox into the SI.

The sound at first was harsh. The sound was very detailed and had pretty good bass but had a certain "airy" or "grainy" quality to it. I was playing my Best of Queen CD and Freddie Mercury sort sounded like he was singing into a tin can. Initially I was a little disapointed but I decided to let the amp burn in awhile. I came back after about four hours and most of the harsh quality was gone...not all...but definately better. I left the unit on all night and by this morning the amp was sounding very nice indeed. Can't wait to get it boxed up and get started on my next project!
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Old 17th August 2005, 11:05 AM   #18
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Default T-Amp volume pot bypass

Hello, the T-amp; why pay more for an amplifier ?
I wish to use it as a power amp (the smallest one I have ever had !) and would therefore like to remove the volume pot. There are 5 wires going to the pot. Any ideas on how to bypass the connections ??? thanks to you all, its my first time up here !
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