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Old 23rd February 2013, 09:35 AM   #4731
koldby is offline koldby  Denmark
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Originally Posted by marconi118 View Post
How this concept could be pushed further by increasing the SLA voltage to lets say 36V the I/V resistor to 4.7K and obtain signal to drive an unity gain circlotron amplifer for lets say 20w on 8ohm

problem, the gate capacitance of the mosfets is about 900pf
You would probably need a driver (2sk314-15-16) for the output lateral, but otherwise a good idea IMHO
And maybe even better if you use two tda1541a in phase/antiphase so the circlotron is driven symetrically.

What is Home Theatre without good sound?
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Old 23rd February 2013, 01:58 PM   #4732
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yes full symmetric, this is an idea of ecdesign

and even better avoiding the coupling caps, the DC voltage across the i/V resistor could be the right bias for the laterals 2sk1530, then use an L pad attenuator at the output of the circlotron prior the speaker as a volume control

ecdesign could you help us? give us a design of the circlotron without drivers, only the laterals, the bias and the balancing to null the output DC
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Old 24th February 2013, 01:12 AM   #4733
Eldam is offline Eldam  France
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Originally Posted by -ecdesigns- View Post
Hi tessier,

DATA and WS attenuators are designed for 3V3 signals (SD8-transport also outputs 3V3 signals).

For WS and DATA:

1K series resistor between digital audio source and TDA1541A I2S input.
680 Ohm pull-down resistor between TDA1541A I2S input and GND.
1K pull up resistor between TDA1541A I2S input and 3V3 (use digital audio source power supply).
Hi Studiostevus,

Thank you for your reply. No problem Studio I have anothers toys (marantz cd45 with tda 1540D, i battle for smoothing the trebles... and with a raindrophui ad1865 which is better with output caps than without... sometimes a good cap or a little lundhal can do big things here whithout lose bass ). I will start when i will have all the datas... the i/v is still problematic if people use no tubes if i understand all than i read...

So I read again the advise of John after asking you about DEM with the SqueezeB receiver. (because I must read again many times to understand both because I take the train of that thread lately & without the suitcase of a techician). Ok understand now that we need to go near 1.8 v to deal with the jitter.
About the cap between pin 16 &17, I assume that you use 1 uF to 1.7 uF... i have to try.

Just another question please for the beginner I am. Cn I use the mk8 shematic for the bck TDA 1541 feeding but just with one 74AU1G74 (second one not usefull because of the cap method between pin 16&17) ? I don't understand wich chip is doing the division Fhz of the clock to arrive to 2 Mhz with a Master clock oh 12.8.. Mhz ? no bck output between SB & TDA but the Masterclock for feeding the Xiling (removing cristal in the SB as slimdevice forum showed ?)... Am i good

what happen to John ? Holiday I hope or producing module for selling I hope too (but his web is not up-to-date with differents photograph and text of the DAC module, John had no time for that with is big work with development... this guy work to much... I am doing my french guy here).

Just a two cent about DC blockink caps : John want to design a full project with minimal passive components between i/v and his speakers: it's an purist complex work but for many of us who need a DAC and not change everything maybe we can deal with these caps... after all the old philips LVh 2000 is a killer... with tda 1540, even with OS... and bad caps, and coupling caps and op5534... Thorsten use of course output caps with tubes and not transformer... and I use, me a 2 cents diyer of sundays, a lundhal with one of my cd player which has the great bass...)
感谢校长出钱,发PHILIPS LHH2000图片(新加LHH2000和D730的听感)。 - 耳 机 论 坛 - 耳机俱乐部论坛 耳机,耳塞,耳放,耳机论坛,音乐,音响 - 耳机俱乐部

Why we can sometimes hear more bass with an output cap I Don't know : phase ? cut ? curve in 40 - 150 Htz ? strucure of the bass with trebles like when we deal with a high filter in a speaker ? Maybe the new snake-oil : Krill - Huile Oemine for massing the body of the cap for liquid sound, nothing of these ?)... but i can hear it so I will not worry to much about that, IMHO.
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Old 25th February 2013, 10:40 AM   #4734
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Originally Posted by oshifis View Post
Referring to post #2738 Building the ultimate NOS DAC using TDA1541A, I would like to know if a lock condition is possible in NOS on 4 x fWS (176.4 kHz). I calculated the internal timing R for the above C values, and it seems that R is around 12.2 kohm. So the C giving 176.4 kHz fDEM might be around 465 pF. Will test it in the coming days...
...err I forgot to divide by 2 *Pi... Just for accurate measuring purpose I used a 7500 pF 0.5% silver mica capacitor, and I measured a DEM frequency of 12.06 kHz. This will give R=1.76 kohm. The average of John's capacitance vs. frequency gives R=1.9 kohm.
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Old 25th February 2013, 10:31 PM   #4735
Eldam is offline Eldam  France
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Default DEM frequency

Hi Oshifis,

Do you know please the value for DEM cap for a 176,4 Khz lock ?

You talk about 7,5 nano for 12,06 Khz... Do you lock with it & does it sound ?

Is it good to go below 150 Khz ? Or above 250 Khz ?
I understood 176,4 Khz could be a good Fdem for lock between these 2 values, is it true ?

John said (for his SD card module):

6K8 between pin 15 (-15V) and 16
6K8 between pin 15 (-15V) and 17
Timing cap between pin 16 and 17 (1n5 or lower).

I mistake writting just before your post: 1 uf to 1,7 uF for Fdem... It's nano Farad... not micro Farad.

So I assume 1,5 n is for 80 Khz (4x20Khz minimum advised ... I do not clearly understand which Fdem is used by John) ? So Fdem good between 80 Khy and 250 Khz ?

Is there a table for KHZ below 250 Khz ? Do I need to change R of pin 15 or 6k8 can be a set value ?

Sorry for replaying the "free DEM frequency" posts here but I misanderstood about the setting of it...

Many thanks if you or somebody could help me.
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Old 25th February 2013, 10:46 PM   #4736
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I used a 1000 pf (1 n) cap, 6K8 resistors, and -15V to pins 16 and 17 to achieve a lock at ~88kHz. I have a 100 pf air capacitor in parallel with the 1000 pf cap, but its barely engaged.

Does anyone have the calculation(s) for the oscillator capacitor values at varying frequencies?

Same for the MSB capacitor at varying frequencies?

Sorry if I missed that somewhere.....
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Old 25th February 2013, 10:54 PM   #4737
Eldam is offline Eldam  France
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Default The Graal of the Good DEM

Originally Posted by brubeck View Post
In my personal experience (with 1uF cap) the optimum for my ears is around 60khz DEM. If i go higher (>100khz) the sound seems more refined but tends to irritate, if i go lower (<25khz) it becomes a bit lifeless. I find it hard to correlate the results. There's a lot going on in the chip
Here Brubeck's experience. Do we understand as John seems suggest that 1,5 nF is for somewhat 80 khz and 1 nF (not uF) for 60 Khz should be good results (under the 100 khz of Brubeck)?

But StudioStevus (his source is a Squeezebox receiver outputing 3.3 V I2S like I try to plan...) is almost happy with 175.4 Khz.
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Old 25th February 2013, 11:16 PM   #4738
Eldam is offline Eldam  France
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Thank you for the input Crobbins,

If I'm right I think it's important to have some inputs of readers here to understand the best values needed for Dem and into these values if a subjective value must be seted for each particular system (speakers, I2S source or I2S attenuation, MSB caps value...).
Because If I understand what I read before there is a match to do for the DEM Fhz Cap for SQ between a SM cap la John and a bigger Silver cap la... I forget the name here). A trigger cap seems to give bad SQ (right/wrong?) even with // true cap. It should be very expensive to buy a lot of silver mica or good SM cap. Not to good for the TDA1541 too!

What do you use for MSB decoupling ? 1 Uf, 2 uf everywhere ? Ceramic? or John 's SM caps ?
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Old 25th February 2013, 11:18 PM   #4739
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The resistance of TDA1541 DEM RC oscillator should be around 1K85, so you can calculate the capacitor value for any frequency using the typical RC oscillator formula: c = 1 / (2 * Pi * 1850 * fDEM) (capacitance in Farad). Around 485 pF for 176kHz. BTW, I believe the resultant capacitor value has to be trimmed to lock (thanks James).
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Old 25th February 2013, 11:26 PM   #4740
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For MSB decoupling I use 4 uF solen caps. It's strange...but they sound wonderful. The next two caps are 1 uf Wima's and the remaining four are .22 uf Wima's.
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