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Old 13th February 2013, 12:45 AM   #1
Thunau is offline Thunau  United States
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Default Tripath TK2050 into high impedance load

I have a Dayton DTA-100a amplifier. It's a Tripath TK2050 based design.
I have been using it with my AKG K-1000 headphones which are rated at 120 Ohm and require 1W to play at normal to loud level. They were designed to work with regular power amps and come with appropriate cables.
I do like the sound of the combination, but I'm EQ'ing out around 7kHz-10kHz to make the headphones sound sweet and balanced.
Could that be due to Tripath not liking higher loads and possibly resonating up there or am I just hearing natural cone breakups of the headphone drivers?
Is it possible to simulate the TK2050 frequency response into 120 Ohm? I googled but came up empty so far.
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Old 13th February 2013, 06:22 AM   #2
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You cannot use any class D amplifier on a load far outside it's operating range.

The entire function of any class D amplifier requires an output filter to reshape the output from PWM signals to analogue signals.

In any commonly available class D amp not specifically designed for high impedance loads this output filter is designed for a load of 4 or 8 ohms, or somewhere in between, usually 6 ohms.

Driving loads 20 times higher than what the output filter is designed for will mean the filter has a completely different XO point and Q.
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Old 13th February 2013, 03:25 PM   #3
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With a 120R load you will get a rising response at the top end.

Try putting an 8R resistor in parallel with each output and see if it changes the sound, but it's probably a good idea to redo the output filter if you really want the best results. Maybe something like 200uH + 22nF.
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Old 14th February 2013, 02:28 PM   #4
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Quote:
Originally Posted by Saturnus View Post
You cannot use any class D amplifier on a load far outside it's operating range.

The entire function of any class D amplifier requires an output filter to reshape the output from PWM signals to analogue signals.

In any commonly available class D amp not specifically designed for high impedance loads this output filter is designed for a load of 4 or 8 ohms, or somewhere in between, usually 6 ohms.

Driving loads 20 times higher than what the output filter is designed for will mean the filter has a completely different XO point and Q.
I have a 2020 amp connected to a pair of vintage 15ohm speakers and they sound great.
I paired them up, as an experiment, not expecting too much but I have made the match permanent
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Old 14th February 2013, 05:14 PM   #5
Thunau is offline Thunau  United States
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Thanks for the responses.
I went with two Rane TF-4 transformers, which I owned for a while now but didn't use and I really like what I'm hearing.
The sound got authority and I don't detect the peaking response anymore, other than the K-1000's natural brightness, which I treat with some EQ anyway.
Here is the link to the transformer:
MA 4 Multichannel Amplifier
It has 8 Ohm primary and two secondaries one for 50 Ohm load and one for 100 Ohm load. I'm using the second tap.
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