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Old 20th June 2014, 06:28 AM   #231
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Я тоже закончил,поставил Wima 100pf в обвызку,пока всё прогревается,но звук приличный.IMG_0578.jpg
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Old 20th June 2014, 09:26 AM   #232
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Hi everyone.
I was going to order the Belleson voltage regulator and do the mod that others have already done.
Belleson are expensive and want $25 postage to the uk so I was thinking of using another make.
Are the NewClassD DX7803 3.3v regulators any good is my first question.
Is there any gain in changing the other regulators to better regulators becouse I am mostly using tube output.
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Old 20th June 2014, 10:25 AM   #233
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Quote:
Originally Posted by lomonosoff View Post
Я тоже закончил,поставил Wima 100pf в обвызку,пока всё прогревается,но звук приличный.Attachment 424617
Your line (AC) filter seems connected wrong.

You should have used "AC IN" at mains plug side. "AC OUT" must go directly to transformer.
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Old 20th June 2014, 10:34 AM   #234
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Thanks for the observation,blame my haste.
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Old 20th June 2014, 11:20 AM   #235
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Quote:
Originally Posted by Sunsun22 View Post
In the course of modification, giving clean power supply to digital part will provide finer details and darker background...
Thanks for sharing Sunsun22, nice picture also

Dave: You can order the Belleson/Dexa regulators with partconexion too. They have 20% discount as well this month. Their location is Canada, shipment to Netherlands is not expensive, most of the time about 10 US dollars for a small package.
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Old 20th June 2014, 11:33 AM   #236
kukynas is offline kukynas  Czech Republic
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Nino: problem might be import duty and tax, don't know how about other EU countries but I would pay for items over $25 around 25% of total value (including shipping cost) so for me is cheaper hificollective or directly from NewClassD in Denmark even if it's few dollars more expensive on parts itself, this is of course related to Dexa products, don't know about EU shop selling Belleson
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Old 20th June 2014, 02:35 PM   #237
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Default alternative output filter

Hi guys,

Just for fun I've designed an alternative filter for the ones that are using opamp output. It has a Bessel characteristic. The main goal was to take advantage of the nearly constant group delay of a Bessel filter. As you can see in the figures, the Bessel filter also has a less sharp roll-off.
-3dB point is approx. at 120kHz. All values for the resistors and capacitors are commonly available.

Because of the -3bB point of both original and Bessel filter is far beyond the normal 20kHz end of audio band, I don't think the gain figures would influence sound a lot. I'd expect sound improvement from the better group delay of the Bessel filter though.

The first 4 resistors come in place of the 4 11k or 12k (2nd version pcb). The total resistance of a pair should ideally match the other pairs. Lowering total resistance of a pair increases gain.

The filter can also be used for other DAC boards with a single AK4399 or AK4396 with single op-amp output. Then you have to replace the resistor pair at the front with one single 4k7 resistor (2.7 dB gain).

If you want to try this circuit, keep in mind that you get best results (with any filter) when the actual values of the capacitors and resistors are as close as possible in each channel. For capacitors I would use polystyrene. They must be soldered quickly, because their value can change when heated for too long ;we're talking pico farads here.


Any comments or improvements are welcome ofcourse.
Attached Images
File Type: jpg gain.jpg (97.2 KB, 155 views)
File Type: jpg gdelay.jpg (86.4 KB, 155 views)
File Type: jpg Circuit.JPG (40.8 KB, 152 views)
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Old 20th June 2014, 07:17 PM   #238
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If anyone is interested in Dexa, please go to Newclassd's website and have a look of their price. Partsconnextion's "original" price is a little bit more expensive than Newclassd but a little bit cheaper after 20% discount. However, please bear in mind that Newclassd is offering free shipping for purchase above Euro 100 AND BESIDES, you get 5 pcs regulators by paying only 4 (look at the bottom line of price list in UWB regulators); that is only $30 each. I regret that I missed this discount in my recent purchase.

If anyone is interested to use Belleson in this DAC, you can consider to use the mini SPM version provided you don't have a high drop out voltage because SPM model cannot mount on heat sink. Two +5V regulators of this DAC draw 50mA each while the remaining one draws a few mA only. Consult Belleson's datasheet on relationship between current and drop out voltage.

Last edited by Sunsun22; 20th June 2014 at 07:37 PM.
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Old 20th June 2014, 09:51 PM   #239
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Quote:
Originally Posted by Sunsun22 View Post
If anyone is interested in Dexa, please go to Newclassd's website and have a look of their price. Partsconnextion's "original" price is a little bit more expensive than Newclassd but a little bit cheaper after 20% discount. However, please bear in mind that Newclassd is offering free shipping for purchase above Euro 100 AND BESIDES, you get 5 pcs regulators by paying only 4 (look at the bottom line of price list in UWB regulators); that is only $30 each. I regret that I missed this discount in my recent purchase.

If anyone is interested to use Belleson in this DAC, you can consider to use the mini SPM version provided you don't have a high drop out voltage because SPM model cannot mount on heat sink. Two +5V regulators of this DAC draw 50mA each while the remaining one draws a few mA only. Consult Belleson's datasheet on relationship between current and drop out voltage.
Thank you Sunsun22 this sounds like a great.
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Old 21st June 2014, 02:00 AM   #240
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What say about these products?
TPS7A3301 -15V 1A 16uVrms Ultra Low Noise Negative LDO Regulator 7915
Discrete Op Amps | Sparkos Labs.comSparkos Labs.com
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