TDA1541 + I/V Output Transformer

mrstone · 6th April 2004, 08:24 AM

Hi Folks,

In transformer-coupled I/V stage, a resistor (around 20 ohm) will be used to terminate the Idac output and then couple to a step-up transformer.

However, at idle stage (silence, no signal), TDA1541 have sink current at the output.

So, my question is: Will this sink current saturate the step-up transformer? Any transformer in the market can be used and is suitable for this purpose?

Your suggestions and comments will be appreciated! Thanks!!

Cheers
Mr. Stone

mrstone · 12th April 2004, 04:55 PM

Pls help.

dddac · 12th April 2004, 09:32 PM

No problem.......

there are specially wound transformers for this purpose. Like the Sowter 8347 1:18 TX. Goes very well, I have built 3 applications with it with Current outputs and it works just fine....

tc
doede

guido · 12th April 2004, 10:13 PM

Use two dac's, feed one with inverted signal. Each has the resistor to gnd. Then connect the transformer between the resistors. No DC over the transformer.

Greetings,

mrstone · 13th April 2004, 03:23 AM

Hi dddac, guido and all,

Could I use Amplimo Signal transformer type TM3? as it's much cheaper than Sowter...

Actually, I send email to Amplimo and asked for the spec, but up to this moment, I still haven't received any response from them....anybody can share your experience on it?

Thanks so much!!

dddac · 13th April 2004, 05:12 AM

Quote:

Originally posted by guido
Use two dac's, feed one with inverted signal. Each has the resistor to gnd. Then connect the transformer between the resistors. No DC over the transformer.

Greetings,

Good trick Guido, as extra bonus you have extra output voltage. One point: Output impedance increases by 4x ...

with the sowter = 14k. Should be ok for most apps...

tc
doede

dddac · 13th April 2004, 05:13 AM

Quote:

Originally posted by mrstone
Hi dddac, guido and all,

Could I use Amplimo Signal transformer type TM3? as it's much cheaper than Sowter...

Actually, I send email to Amplimo and asked for the spec, but up to this moment, I still haven't received any response from them....anybody can share your experience on it?

Thanks so much!!

I don't know this one.... sorry, just try it I would suggest?
tc
doede

guido · 13th April 2004, 10:21 AM

From the website:

Signal transformer type TM3 Euro 26,47

Never try to check the windings with an ordinary multimeter. The DC-current of the meter will magnetise the core!

Ratio
1 : 15

frequencyrange +3dB
30 - 25000 Hz

max. input at 30Hz.
800mV

to connect primary
microphone of max. 200 Ohm

to connect secondary
min. 45 kOhm

primary wires
green - grey

secondary wires
red - blue

lead length
70mm

max.voltage between prim. and sec. winding
100V

dimensions excl. screwthreat
22 x 23mm (diam x height)

Greetings,

firestorm · 16th April 2004, 08:19 AM

Mr Stone,
Have you used the Amplimo Signal transformer type TM3 ?

What are your findings ?

Regards
firestorm

rbroer · 16th April 2004, 11:00 AM

My findings:

The TM3 is physically smaller, and output voltage collapses quite easily.
IME, sweet sound, but bass and dynamics suffered using either stepup transformer, TM3 being worst. YMMV.
Also experienced hum problems that I could only solve by giving up galvanic isolation.

In the end too low output for me when using Riv of 22 ohms for
TDA1541 In this setup, the TM3 had almost no output, much less than one would expect when comparing the 18* and 15* stepup ratios.
My preference clearly goes to the Sowter 8347 1:18 TX

6th April 2004, 08:24 AM	#1
mrstone diyAudio Member Join Date: Aug 2003 Location: Hong Kong	TDA1541 + I/V Output Transformer Hi Folks, In transformer-coupled I/V stage, a resistor (around 20 ohm) will be used to terminate the Idac output and then couple to a step-up transformer. However, at idle stage (silence, no signal), TDA1541 have sink current at the output. So, my question is: Will this sink current saturate the step-up transformer? Any transformer in the market can be used and is suitable for this purpose? Your suggestions and comments will be appreciated! Thanks!! Cheers Mr. Stone __________________ Mr. Stone

12th April 2004, 04:55 PM	#2
mrstone diyAudio Member Join Date: Aug 2003 Location: Hong Kong	Pls help. __________________ Mr. Stone

12th April 2004, 10:13 PM	#4
guido diyAudio Member Join Date: Mar 2002 Location: diepe zuiden	Use two dac's, feed one with inverted signal. Each has the resistor to gnd. Then connect the transformer between the resistors. No DC over the transformer. Greetings, __________________ GuidoB

13th April 2004, 03:23 AM	#5
mrstone diyAudio Member Join Date: Aug 2003 Location: Hong Kong	Hi dddac, guido and all, Could I use Amplimo Signal transformer type TM3? as it's much cheaper than Sowter... Actually, I send email to Amplimo and asked for the spec, but up to this moment, I still haven't received any response from them....anybody can share your experience on it? Thanks so much!! __________________ Mr. Stone

13th April 2004, 10:21 AM	#8
guido diyAudio Member Join Date: Mar 2002 Location: diepe zuiden	From the website: Signal transformer type TM3 Euro 26,47 Never try to check the windings with an ordinary multimeter. The DC-current of the meter will magnetise the core! Ratio 1 : 15 frequencyrange +3dB 30 - 25000 Hz max. input at 30Hz. 800mV to connect primary microphone of max. 200 Ohm to connect secondary min. 45 kOhm primary wires green - grey secondary wires red - blue lead length 70mm max.voltage between prim. and sec. winding 100V dimensions excl. screwthreat 22 x 23mm (diam x height) Greetings, __________________ GuidoB


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12th April 2004, 09:32 PM	#3
dddac diyAudio Member Join Date: Jul 2003 Location: Wiesbaden	No problem....... there are specially wound transformers for this purpose. Like the Sowter 8347 1:18 TX. Goes very well, I have built 3 applications with it with Current outputs and it works just fine.... tc doede

16th April 2004, 08:19 AM	#9
firestorm diyAudio Member Join Date: Mar 2004 Location: Surrey, UK.	Mr Stone, Have you used the Amplimo Signal transformer type TM3 ? What are your findings ? Regards firestorm

16th April 2004, 11:00 AM	#10
rbroer diyAudio Member Join Date: Mar 2002 Location: Netherlands	My findings: The TM3 is physically smaller, and output voltage collapses quite easily. IME, sweet sound, but bass and dynamics suffered using either stepup transformer, TM3 being worst. YMMV. Also experienced hum problems that I could only solve by giving up galvanic isolation. In the end too low output for me when using Riv of 22 ohms for TDA1541 In this setup, the TM3 had almost no output, much less than one would expect when comparing the 18* and 15* stepup ratios. My preference clearly goes to the Sowter 8347 1:18 TX __________________ Rudolf Broertjes

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