Cool, I haven't sen this for many years but this is the circuit that I built way back ... around 2000? Or thereabouts. But with one small change - I never installed the resistor/cap combination from the centre tap of the tx primary, to ground. No good reason, I built the circuit first without these components and it worked just fine (it still does!) so I never bothered to add them in. Am I missing anything important?
Hi, I didn't get a message about your response in my email. Sorry for the late reply. Well... I don't have any TDA1543 here. If the output has a standing offset current like a TDA1541A without a current source, I'd suggest using a capacitor to block that before the transformer. Which Lundahl are you using? I'll try to help you. DaveHi Dave and other Guys...
...thanks a lot for all answers.And yes Dave your sugestions work best.Dave if you could be so nice,can you tell me if I can use this Lundahl transformers with TDA1543 dac to??I just become some dac board from my good friend with TDA1543 in non oversampling mode with direct output via capacitor(47uF electrolitic).Si I would use now in the place of the output capacitors this lundahl LL1527 transformers.Is this posibile??And if yes,would I need some aditional parts (resitors,capacitors)on the primary or secondary site of the transformers??
Rado
I think your fine without that filter. That was the only place I have ever seen that configuration used. Dave
TDA1543 with Lundahl LL1527?
Hi audiorado, I think your using the LL1527. I will assume 1:1 Line level configuration ~ 800 Ohms primary. Take a multimeter set to low VDC. Measure the output pin of the DAC or DAC side of the electrolytic capacitor to ground. You may see anything from a Volt to mV's. If you get a few milliVolts's. It should be possible to use the transformer without the capacitor. Otherwise, I have used 10 uF Polypropylene capacitor with 10 K Ohm series resistor to the transformer. Good bass too. Let me know what you measure, check both channels. I can draw that up for you and post the wiring. Hope that helps. Dave
Hi audiorado, I think your using the LL1527. I will assume 1:1 Line level configuration ~ 800 Ohms primary. Take a multimeter set to low VDC. Measure the output pin of the DAC or DAC side of the electrolytic capacitor to ground. You may see anything from a Volt to mV's. If you get a few milliVolts's. It should be possible to use the transformer without the capacitor. Otherwise, I have used 10 uF Polypropylene capacitor with 10 K Ohm series resistor to the transformer. Good bass too. Let me know what you measure, check both channels. I can draw that up for you and post the wiring. Hope that helps. Dave
I think your fine without that filter. That was the only place I have ever seen that configuration used. Dave
Thanks for the reply Dave. Any idea what is the purpose of the filter?
Filter network....
It appears to establish a ground reference at the center point of the transformer. At very low frequencies it should remove rubbish. When I used the Lundahl LL1690, the designer of that DAC left the center point unterminated. I found no issues with that. My CS4398 DAC is dead quiet without signal. It does have a relay based mute. So that may not be a good comparison.
DAC CS4390+lundahl LL1527 passive output
Hi Dave.....
...sorry for late response,I was on holydays and just came beck home.Thanks a lot for al your help.In the next days I will try the option with my lundahls LL1527 and TDA1543 and see what I get from this combo.Your instruction are verry verry helpful,and many thanks for your help.In the min time I have buy some lundahls LL1690 to.
So I will try the diference between the LL1527 and LL1690 to.
But becouse the LL1690 seems to be bether becouse thay have amorphos core I will try to sell the LL1527 tranys.
SO IF SOMEONE WILL NEED A PAIR OF THE LUNDAHLS LL1527 IN VERRY GOOD CONDITION,you could email me for the price and shipping options.I buy this from sweden a 6 months ago for about 160 euro(caa.200usd)!
I will report back in next days,when I will try the non-os tda1543 dac with transformer output.
Hi Dave.....
...sorry for late response,I was on holydays and just came beck home.Thanks a lot for al your help.In the next days I will try the option with my lundahls LL1527 and TDA1543 and see what I get from this combo.Your instruction are verry verry helpful,and many thanks for your help.In the min time I have buy some lundahls LL1690 to.
So I will try the diference between the LL1527 and LL1690 to.
But becouse the LL1690 seems to be bether becouse thay have amorphos core I will try to sell the LL1527 tranys.
SO IF SOMEONE WILL NEED A PAIR OF THE LUNDAHLS LL1527 IN VERRY GOOD CONDITION,you could email me for the price and shipping options.I buy this from sweden a 6 months ago for about 160 euro(caa.200usd)!
I will report back in next days,when I will try the non-os tda1543 dac with transformer output.
HI all,
I'm embarassed to make some stupid question to very experts as you,
but I have a micromega DUOBS and DUOPRO2 dacs , wich are 1 bit ( IMHO very good), but " IC output stage.
So, I have thinked to modd with a sowter transformer , but I have no idea if the dac CHIPS ( Philips?) are voltage output or current output.
Is it possible put a transformer in both cases ,or only if they are "current output"....?
Thanks for help
Paolo
VEnEZIA, Italy
I'm embarassed to make some stupid question to very experts as you,
but I have a micromega DUOBS and DUOPRO2 dacs , wich are 1 bit ( IMHO very good), but " IC output stage.
So, I have thinked to modd with a sowter transformer , but I have no idea if the dac CHIPS ( Philips?) are voltage output or current output.
Is it possible put a transformer in both cases ,or only if they are "current output"....?
Thanks for help
Paolo
VEnEZIA, Italy
Last edited:
1 Bit dac
1 bit dac's are usually voltage out devices. Voltage out is good because you don't need any additional Opamps. Can you pop the hood and get the chip number off the dac? I can look it up and see what needs to be done. I use transformers with the TDA1541A... The transformer operates as a passive filter after the I/V. here is a link to my just finished dac. http://www.diyaudio.com/forums/digital-line-level/166807-dac-gallery-10.html#post3570456 Discrete I/V and Edcor's. My best sounding dac to date for pure sound quality. DaveHI all,
I'm embarassed to make some stupid question to very experts as you,
but I have a micromega DUOBS and DUOPRO2 dacs , wich are 1 bit ( IMHO very good), but " IC output stage.
So, I have thinked to modd with a sowter transformer , but I have no idea if the dac CHIPS ( Philips?) are voltage output or current output.
Is it possible put a transformer in both cases ,or only if they are "current output"....?
Thanks for help
Paolo
VEnEZIA, Italy
thanks dave,
i'll look at your work just as possible ( VERY BUSY WITH N.E.M. SPEAKERS CANADA -
A NEW STRATOSPHERICAL COST TO PRICE RATIO FACTORY, WICH WANT "ATTACK" THE MAGICO MINI AND WILSON WATT AND TAD LITTLE AND LITTLE AVALON AND Thiel,etc,
at a little fraction of the cost.....
(new politic/strategy : stop to excessive expansive speakers)
( by my design... -thanks to a contact on this site/forum - !!!
see PHASELESS SPOT on "loudspeakers - multiways")
thank you very mutch!
cheers
Paolo Phaseless high end speakers
i'll look at your work just as possible ( VERY BUSY WITH N.E.M. SPEAKERS CANADA -
A NEW STRATOSPHERICAL COST TO PRICE RATIO FACTORY, WICH WANT "ATTACK" THE MAGICO MINI AND WILSON WATT AND TAD LITTLE AND LITTLE AVALON AND Thiel,etc,
at a little fraction of the cost.....
(new politic/strategy : stop to excessive expansive speakers)
( by my design... -thanks to a contact on this site/forum - !!!
see PHASELESS SPOT on "loudspeakers - multiways")
thank you very mutch!
cheers
Paolo Phaseless high end speakers
Big they are...
DIY is never done it's evolution.....
You should see my current system. Big.... At the moment... Paragon Regents running full range with augmented bass (2) 12 Inch subwoofers. Just got it dialed in tonight. Very happy with it. Next Magnepan MG 2.5R's with augmented bass system. That one is more difficult to do. DSP will be needed.oh . interstying thread and dacs!!
Time to go to lab wher ythe dac is for restore laser and i'll open the dacs and read the chips - item...
thanks
Paolo
phaseless speakers italy
C.E.O. N.E.m: spekaers - canada ( website coming soon)
by
paolo
DIY is never done it's evolution.....
Hi
I use transformers with Burr Brown voltage o/p Dacs with superb results. I wound my own 1:2 step up txs for these to give the redbook standard o/p level.
One thing to watch out for is that most voltage o/p dacs specify a minimum AC load
impedance ie 1.4K in the case of the BB dacs. Depending on the particular tx it can happen that the impedance presented by the txs primary inductance plus its dcr falls below this value at low frequencies. This can be seen on the scope as a nasty oscillation. Ok its only at low frequencies but not a nice way to treat a dac.
A cure for this is some series resistance in the primary which adds enough to the txs inductance and dcr to stop the oscillation. In my case 100R was sufficient.
I use transformers with Burr Brown voltage o/p Dacs with superb results. I wound my own 1:2 step up txs for these to give the redbook standard o/p level.
One thing to watch out for is that most voltage o/p dacs specify a minimum AC load
impedance ie 1.4K in the case of the BB dacs. Depending on the particular tx it can happen that the impedance presented by the txs primary inductance plus its dcr falls below this value at low frequencies. This can be seen on the scope as a nasty oscillation. Ok its only at low frequencies but not a nice way to treat a dac.
A cure for this is some series resistance in the primary which adds enough to the txs inductance and dcr to stop the oscillation. In my case 100R was sufficient.
Agreed
I use a value of 1K Ohm on a CS4398 dac. There doesn't seem to be any downside to filters made from these transformers. Edcors are very inexpensive too.
Before pursuing that method, I would suggest applying a transformer suitable for the application. I use a Jensen JT11-DMPC for my DAC outputs, which has -3dB bandwidth down to 0.1 Hz. Now you can avoid band-aiding the setup with series resistance. In essence you are throwing away signal with a voltage divider. THD of -86dB at 20 Hz is no slouch for a transformer output. It only gets better as you go higher in freq.
Jensen
I hear that those are very good transformers. Thanks for the tip. I have tried Edcors and Lundahls so far. The latter are very expensive.
pioneer legsato link 1 bit/current output DAC chips
hi all experts,
Micromegas DAC apart,
my intentions is to purchase ,used, a PD 95 or PD 77 Pioneer wich was 1 bit , differential output current dac chips ( if i remember correctly).
Jet "stand alone" ,with poor iC buffer and amplifications / low pass filter, they IMHO sound "GOOD" ,
but I suspect that IF I remove that darmn IC and swap with a sowter or lundhal transformer ,
the sound will be GREAT.
ARE I "crazy"?
Cheers,
paolo venezia Italy
hi all experts,
Micromegas DAC apart,
my intentions is to purchase ,used, a PD 95 or PD 77 Pioneer wich was 1 bit , differential output current dac chips ( if i remember correctly).
Jet "stand alone" ,with poor iC buffer and amplifications / low pass filter, they IMHO sound "GOOD" ,
but I suspect that IF I remove that darmn IC and swap with a sowter or lundhal transformer ,
the sound will be GREAT.
ARE I "crazy"?
Cheers,
paolo venezia Italy
Hi Zigaflux
The Jensen tx looks like a superb tx but I would imagine its quite expensive? It
uses large laminations which could give a nice high primary inductance which
would indeed avoid the loading problems. In my case 100R does not significantly
attenutate the o/p and I can use cheaper smaller laminations (neccesary as
its for a commercial product). Must try the bigger lams myself. Thanks for the tip.
The Jensen tx looks like a superb tx but I would imagine its quite expensive? It
uses large laminations which could give a nice high primary inductance which
would indeed avoid the loading problems. In my case 100R does not significantly
attenutate the o/p and I can use cheaper smaller laminations (neccesary as
its for a commercial product). Must try the bigger lams myself. Thanks for the tip.
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