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Highly evolved converters - the next generation

Posted 8th September 2011 at 03:47 AM by abraxalito

Its been over a year since I blogged about DACs, so, long overdue, here's an update. I've abandoned my considerable development on the AD1955 because I found something that's more interesting - multibit. In the first instance - NOS.

A while back I bought a TDA1543 NOS DAC to play with, just to see what all the fuss was about with NOS. Plenty of people have waxed lyrical about the sound. At first listen, I wasn't impressed although it had a certain tonal richness in portraying orchestral instruments that was alluring. Bottom line - its soundstage was compressed front to back. This made it sound a little 'forward' - foreground instruments and voices were more highlighted compared to acoustic spaces ('background').

A second aspect which plagues pretty much all NOS DACs is their frequency response can hardly be termed 'accurate' - owing to the sinc function of first-order hold, they exhibit a significant HF roll-off which begins around 5kHz and reaches 3.2dB...
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LME49810 300 W amp kit from TaoBao (Test)

Posted 5th September 2011 at 10:17 PM by panson_hk

The board is ready for test. The bias level is adjusted via monitoring the THD level as well as the distortion residual.

THD vs power for 20 Hz, 1 k and 20 k for 8 Ohm are shown in the figure. It is so high compared to all my 498xx amps. For 1 k, we should have THD lower than 0.0008 %.

Let test the THD vs power without load. Without load connected, output stage contributes very little distortion. This can be used to check whether the 49810 functions as spec or not.
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LME49810 300 W amp kit from TaoBao (Cont.)

Posted 5th September 2011 at 12:10 PM by panson_hk

The amp is assembled and ready for testing. It is designed to have two rails: one for LME49810 (suggested +/- 60 V) and one for driver/output (suggested for +/- 45V). The speaker protector uPC1237 also has an input for detecting the presence of AC (half-wave rectified).

In my initial test, one rails supply to 49810 and the output stage. The positive is also connected to the AC input of upC1237.
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Old

LME49810 300 W amp kit from TaoBao

Posted 5th September 2011 at 08:26 AM by panson_hk
Updated 5th September 2011 at 08:36 AM by panson_hk

This kit is available in many sellers in eBay and TaoBao. My one is purchased from TaoBao. The output stage does not have protection. All the resistors are pre-inserted. What a nice service to save some time.

The 49810 heatsink screw holes are not aligned well. I also worry about its size.

The Miller compensation cap is a pre-soldered chip cap on the bottom side as shown in the picture. Fuses are pre-installed in the fuse holders.

Output are five pairs of 5200/1943.
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Old

Old Majestic Car Amp

Posted 2nd September 2011 at 01:00 AM by DigitalJunkie

I got this amp in 'fried' condition from a friend many years ago. I finally managed to get it working,and I've been using it for my subwoofer amp ever since,probably about 10 years now? It's not the greatest amp,but it has served me very well on sub duty.

It claims to be 200W per channel, and bridgeable to 400W. It might even pull that off,on a good day.

Anyways,I had some very poor scans of the schematic for this amp(which I later discovered was almost identical to a 4 channel Rockwood amp.) I managed to re-draw the basics,and thought I'd post it up for the forum to check out.

I've been thinking of taking this amp to the bench to do some tests,and maybe some tweaks. I'm all ears if anyone has any thoughts?

Here's a link to the redrawn schematics,I might put the original scans in there also.
Some component values are missing,I was going from memory,and what I could make out from the original scans.

MA-9400 pictures by Nothing40 - Photobucket
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Old

EMT 950 Turntable

Posted 31st August 2011 at 04:00 AM by Davo58

Has anybody had to try and play discs that run at slower speeds than 33 rpm.
We have some 24 rpm and 16 rpm discs that we need to digitise and was wondering if you hve been able to slow down your EMT950 to be able to do this.
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Please help to decide box for FE103En

Posted 29th August 2011 at 08:54 PM by audiomovil

i want to build a box for my new FE103En, please help to decide between Buschhorn Mark II or the Sperrin and Vampyr-v, from Woden Design.
I use a Yamaha amplified 10" sub and Yamaha amp 60x2, for use in a living room 11 ft by 13 ft, for movies and music., jazz and rock.
Thanks for the help.
Gustavo Espino from Jalisco México.
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Old

Best source for TX2575 Naked Z-Foil Resistor

Posted 28th August 2011 at 07:52 AM by dvb projekt
Updated 28th July 2014 at 10:12 AM by dvb projekt

All members who want to use the "holy grail" audio resistor,

the TX2575 Naked Z-Foil,

could order it direct at Texas Components.


That´s the cheapest way to get it IMO.

They have also great Trimpots with Bulk Metal Foil Technologie.





P.S.: If you send a mail to Arbie, send her regards from me!
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Old

Conn strobotuner

Posted 27th August 2011 at 01:17 AM by blackveilbridessixx

does anyone know how much a conn strobotuner model st 11 is worth?
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Old

Projection lens and Fresnel lens

Posted 23rd August 2011 at 11:37 AM by djhot143

Hi to all friends,I am new here.
My name is DHIRAJ from mumbai,india.

I need your help, I want to make a projector but i am not getting parts of it.
Can anyone tell me where i can buy projection lens and Fresnel lens in Mumbai. plz help me.
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