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Add step-up tx to 26 lineamp
Add step-up tx to 26 lineamp
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Old 17th October 2020, 09:05 PM   #11
merlin el mago is offline merlin el mago  Europe
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Quote:
Originally Posted by analog_sa View Post
You should do some basic troubleshooting.

Play a 1kHz sine on the dac and measure the voltage across the 50ohm resistor. Connect transformer 300ohm primary to resistor with the secondary unloaded and take measurements at both primary and secondary windings. Add tube stage.
Can't do it see attached schematic of the output filter of the noDac I use.
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Old 17th October 2020, 09:36 PM   #12
merlin el mago is offline merlin el mago  Europe
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Oooops I forgot I use SET 5687 CCS loaded between the noDac & the 26, surely this is the guilty increasing the output impedance of noDac

Last edited by merlin el mago; 17th October 2020 at 09:39 PM.
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Old 18th October 2020, 11:50 AM   #13
euro21 is offline euro21  Hungary
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Add step-up tx to 26 lineamp
Try to check primary/secondary ratio (maybe it's 1:7).
Adding 1Veff (from 5687, for example at 1kHz) to lower side, on the other side the voltage must be 7V.

Repeating this, several times, at different frequencies (from 20Hz up to 50-100kHz) turns out if it is suitable for step up input transformer.
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Old 18th October 2020, 03:08 PM   #14
merlin el mago is offline merlin el mago  Europe
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SG 0.250Vrms, 50 ohms source impedance, without zobel.

20Hz 2.61
100Hz 4.8
1K 4.8
5K 2.56
10K 1.28
15K 0.75
20K 0.47
25K 0.3
30K 0.12
35K 0.05
40K 0.04
50K 0.04
55K 0.08
60K 0.036
70K 0.14
80K 0.32
90K 0.16
100K 0.039

Last edited by merlin el mago; 18th October 2020 at 03:16 PM.
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Old 18th October 2020, 04:15 PM   #15
merlin el mago is offline merlin el mago  Europe
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300R side have a center tap that measures the same between the center tap & the 150R of both sides

Freq. Ratio
20Hz 2.52
100Hz 5.72
1K 7.07
5K 1.78
10K 0.74
15K 0.37
20K 0.20
25K 0.063
30K 0.048
35K 0.032
40K 0.028
50K 0.048
55K 0.19
60K 0.12
70K 0.04
80K 0.04
90K 0.04
100K 0.036

Last edited by merlin el mago; 18th October 2020 at 04:17 PM.
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Old 18th October 2020, 04:45 PM   #16
merlin el mago is offline merlin el mago  Europe
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I have a couple of Edcor GXSE5-600-15K pri.15K sec.600R

Freq. Ratio
20Hz 1.15
100Hz 2.59
1K 4.68
5K 3.86
10K 2.96
15K 2.4
20K 2.04
25K 1.79
30K 1.59
35K 1.45
40K 1.35
50K 1.18
55K 1.08
60K 1
70K 0.86
80K 0.72
90K 0.64
100K 0.041

Edcor measures 24R & 258R

Last edited by merlin el mago; 18th October 2020 at 04:51 PM.
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Old 18th October 2020, 05:18 PM   #17
analog_sa is offline analog_sa  Europe
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Add step-up tx to 26 lineamp
That kind of clears it up.

You have nearly 1:5 @ 1kHz, the low frequencies are depressed because of high output impedance/low transformer inductance and the highs are depressed...dunno why really but a crappy transformer or a capacitive load seem both possible. How is the transformer loaded?
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Old 18th October 2020, 08:57 PM   #18
merlin el mago is offline merlin el mago  Europe
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Without load.
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