Thanks Wayne!
I've adjusted the bias so that I get 0,28V across both resistors 3R3. After that I measured 940mV at pin 4 of the 1646, slightly higher than what I had set earlier (850mV).
My DC offset is 5,8mV left and 7,8mV right. Also, I've clamped the heat sink to the chassis and now it gets mildly warm, actually not even that. Much better.
Thanks again for this nice amp!!
Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
- mediatechnology
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Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
Hey Radiance you're welcome!
Thanks for the data.
One thing I can't tell from the photos is whether or not the Vbe multiplier transistors are firmly attached to the heatsinks. Is it clamped somehow? Since it's on the backside I couldn't tell.
Thanks for the data.
One thing I can't tell from the photos is whether or not the Vbe multiplier transistors are firmly attached to the heatsinks. Is it clamped somehow? Since it's on the backside I couldn't tell.
Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
It's firmly attached on the backside of the heatsink. It was a tight fit as you can see.
- mediatechnology
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Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
OK, I see the pop rivet now. Thanks.
The BD139/140 I use are electrically insulated so I didn't have to use sil-pads.
The BD139/140 I use are electrically insulated so I didn't have to use sil-pads.
- mediatechnology
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Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
So how does it sound radiance?
Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
Yesterday, I spend some time listening to Miles Davis - In a silent way/ It's about time.
Man, I had a great time. It just sounded right! And it can do LOUD.
I can say this is a step up from my previous headphoen amp. That was a headphone amp in the monitor section from a Sony MXP2900 broadcast desk build with a 5216 (???) opamp set to +/- 18V.
Man, I had a great time. It just sounded right! And it can do LOUD.
I can say this is a step up from my previous headphoen amp. That was a headphone amp in the monitor section from a Sony MXP2900 broadcast desk build with a 5216 (???) opamp set to +/- 18V.
- mediatechnology
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Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
Thanks for the update.
I'm not a big headphone listener but I have a hard time taking them off when listening to it. I handed them over to my wife and had a hard time getting them back.
I'm glad the level is hot enough. Since it's unity gain it might need, with -10 sources, a little help up front depending on the 'phones. But it was certainly loud enough for me.
I'm not a big headphone listener but I have a hard time taking them off when listening to it. I handed them over to my wife and had a hard time getting them back.
I'm glad the level is hot enough. Since it's unity gain it might need, with -10 sources, a little help up front depending on the 'phones. But it was certainly loud enough for me.
- mediatechnology
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Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
I was kind of hoping you would say that Roger.Maybe it will develop into a DIY circuit board.
Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
If you're interested I can give you the gerbers of my attempt. They'll need some modefying to make them into a DIY project though....