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Old 23rd June 2013, 04:28 PM   #4891
wlowes is offline wlowes  Canada
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Quote:
Originally Posted by maxlorenz View Post
Hi dear Triode_al,



Good one.
Maybe that is one of the reasons why R core (or C core) Tx sound so good.
I rejoice when I dismantle a machine with split bobines even if later I don't use them, hehe.
Maybe we have to wind our own Tx's.

I wonder if you have tried John's charge-transfer supply (I don't remember).

Cheers,
M.
I am at the same stage of planning. What do you think of the Hammond 229 series. Seems to have many of the features we seek.
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Old 23rd June 2013, 10:06 PM   #4892
roger57 is offline roger57  Canada
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Default Custom Transformers for TDA1541A and other parts

Hi all,

I'm cleaning up my project parts from the past few years on the TDA1541A since my project is finished and my "dream machine" is running nicely.
I was not happy with the transformers I could find, and wasn't thrilled with using several in a chassis, so I had Hammond custom wind some for me. I had 4 made to meet the minimum NRE charge. Here's the specs:

* Flux band for very low/ no leakage
* 6 windings total
220V RMS, 75mA
12V, 1.5A
12V, 200mA
12V, 200mA
18V, 200mA
10V, 3.5A

I have only 2 for sale.

Also, over the last 12 years, since becoming interested in the TDA1541A, I have accumulated quite a few TDA1541A chips, of which I'm also selling. The collection includes *one* Double Crown and some R1 devices.

If anyone's interested, please PM me for a list, prices and other project items related to the TDA1541A only.

Thanks to everyone in this thread over the years for making this a great and rewarding project to work on!

Gary
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Old 24th June 2013, 03:27 PM   #4893
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Quote:
Originally Posted by maxlorenz View Post
Hi dear Triode_al,

Maybe we have to wind our own Tx's.

I wonder if you have tried John's charge-transfer supply (I don't remember).

Cheers,
M.
Yes winding up our own

No, I didn't test the CT-supply. I would think that it does not reduce capacitative coupling; just it provides an earth where the initial capacitor load current is more absent.
  • From playing around with tubes I found out that sometimes just having a DC power supply for the heaters the spikes (and even signal) would show up elsewhere even if there was no direct DC link via earth. I guess this might also be capacitance . . .
  • I tested a output transformer that was straight to 90 kHz then has a dip to -20 db but passed everything above 2 MHz. . So instead of having a capacity meter we should also test with a wide-band sine generator.
albert
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DAC TDA1541 S1; Kondo post-I/V filter; MC30-Super --> two stage RIAA; Pre: Kaneda ; F5 ; 300B PP ; ESL 57
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Old 24th June 2013, 04:31 PM   #4894
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Quote:
Originally Posted by triode_al View Post
Yes winding up our own

No, I didn't test the CT-supply. I would think that it does not reduce capacitative coupling...
[/LIST]albert
Probably not and even add the Mosfet gate capacitance, yet sonically it is far superior than conventional aproach.

Quote:
[LIST][*]From playing around with tubes I found out that sometimes just having a DC power supply for the heaters the spikes (and even signal) would show up elsewhere even if there was no direct DC link via earth. I guess this might also be capacitance . . .
[*]I tested a output transformer that was straight to 90 kHz then has a dip to -20 db but passed everything above 2 MHz. . So instead of having a capacity meter we should also test with a wide-band sine generator.
The road to good sound is the figth against noise I add empirically wide band inductors to all ground interconnections between active boards or to nodes, at present...

Cheers,
M.

PS: nice transformers guys.
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Old 25th June 2013, 02:34 PM   #4895
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Hi vandenberg,

Quote:
i agree with ,that it is good to have powersupply with as low as possible capacitance to anything.
that why i use dc/dc coverters in my dacs.
Keep in mind that SMPS are EMI generators that pollute everything attached or near to it. The unshielded mains wiring distributes SMPS interference all over the building.

The power supply is in the signal path (just draw an ac diagram), so you basically placed an EMI generator right in series with the signal. I personally wouldn't do that.
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Old 25th June 2013, 03:07 PM   #4896
SSerg is offline SSerg  Russian Federation
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Hi,-ecdesigns-

Quote:
Originally Posted by -ecdesigns- View Post
The power supply is in the signal path (just draw an ac diagram), so you basically placed an EMI generator right in series with the signal.
If you are using a local shunt regulator, the signal current is closed through it.
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Old 30th June 2013, 05:54 PM   #4897
roger57 is offline roger57  Canada
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Default Hammond Custom Transformer for TDA1541A DAC

For those who have inquired, here's what a custom transformer looks like. Single solution is ultimately better that multiple transformers in a cabinet. Note the copper flux band running the circumference of the transformer. The transformer runs cool and very quiet, DAC performance is outstanding with no sign at all of 60Hz (or harmonics) noise injected in.

Size is as shown.

Regards,
Gary
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File Type: jpg DAC_Xfmr_Top_View.jpg (277.9 KB, 756 views)
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Old 30th June 2013, 09:01 PM   #4898
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I was thinking, aren´t diode rectifiers just as bad as SMPS, with their switching? They certainly are generating EMI on both the mains and the subsequent circuit.

SMPS can operate at a chosen optimal frequency that can be very well filtered.

Active PFC (power factor correction) can make the mains current close to senoidal.

So, I think a well designed smps can be better than diode rectifiers.

Of course, the audio currents needs to be decoupled and separated from the pulse currents of the supply. Shunt regulators come to mind.

Just some thinking.
-Alex

Quote:
Originally Posted by -ecdesigns- View Post
Keep in mind that SMPS are EMI generators that pollute everything attached or near to it. The unshielded mains wiring distributes SMPS interference all over the building.

The power supply is in the signal path (just draw an ac diagram), so you basically placed an EMI generator right in series with the signal. I personally wouldn't do that.
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Old 11th August 2013, 02:26 PM   #4899
Skorpio is offline Skorpio  Denmark
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Quote:
Originally Posted by -ecdesigns- View Post


I attached latest TDA1541A circuit schematics:

- DEM synchronizer circuit
- I2S attenuators
- I/V converter

I/V converter uses a plain (unselected) 2SK170-BL JFET and a 10K bias resistor. Actual I/V conversion is fully passive as the JFET merely passes the DAC output current as is. Gate current is much lower than LSB current.

I use +5V as reference instead of GND. This excludes +5V power supply from the direct signal path as I measure directly across the I/V resistor.

This converter provides simplest and cleanest output signal as the actual I/V converter consists of a single 500R resistor. All other options require active amplification and / or transformers that will introduce additional distortion.

Output coupling cap needs to be added to block DC. The hybrid coupling cap that performs closest to DC coupling was composed by paralleling 2.2uF/250V Monacor MKT, 3.3uF/250V Monacor MKT and a 40pF Teflon trimmer (set to max. value).
Hi,
Thank you for very interesting work!
I have implemented your nice IV-converter and it works fine on the test bench. But now I want to hear it in my system and got some questions:

The output must be taken over the 500R resistors and with +5v as reference, but when connecting to my amp this will be connected to amp ground...problem?

Normally a capacitor output has a bleeder resistor to gnd on the output side to discharge cap, should this be connected to gnd or +5v?

Can the 500R be changed to 680 or 1000R if I need more output and what are the limits, drawbacks?


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Old 11th August 2013, 03:39 PM   #4900
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Hi Skorpio,

The I/V stage built around the 2SK170 is outdated, one of the problems is that it exceeds TDA1541A output compliance.

Quote:
The output must be taken over the 500R resistors and with +5v as reference, but when connecting to my amp this will be connected to amp ground...problem?
The adjustable DC reference voltage takes care of this. It consists of a 1K trimmer with a 1000uF cap between wiper and GND, and another 1000uF cap between the wiper and +5V.

The voltage at the wiper serves as GND connection for the RCA sockets. This works as long as this reference voltage is not short-circuited by other connected equipment.

The trimmer is set for lowest possible DC voltage reading between the wiper of the trimmer and both RCA outputs.

Quote:
Normally a capacitor output has a bleeder resistor to gnd on the output side to discharge cap, should this be connected to gnd or +5v?
This design requires no coupling caps, it ensures highly transparent playback with optimal bass response and ease of mind that one exceeds the performance of the best film caps available.

Quote:
Can the 500R be changed to 680 or 1000R if I need more output and what are the limits, drawbacks?
Not with the 5V supply. When the supply voltage (for the I/V stage only!) is increased, to say to 10V, it is possible to double the output amplitude by using a 1K I/V resistor. Disadvantage is that the selected bit currents no longer flow back into the 5V supply like the unselected bit currents do. This leads to higher ripple voltage on the 5V supply and increased on-chip jitter levels.
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