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Gyrator loaded Son of ZV9/F3
Gyrator loaded Son of ZV9/F3
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Old 23rd February 2019, 07:11 PM   #221
juma is offline juma  Serbia
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Quote:
Originally Posted by maouna View Post
...do you have any other shunt PSU like the one with TL431 but with 48V output and the same noise suppression results...
No, I don't but I think that Salas has some that will do nicely.
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Old 23rd February 2019, 07:36 PM   #222
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Quote:
Originally Posted by maouna View Post
If i want to put a coupling capacitor between input volume pot and R3...
No, you put it before the pot, with minus pin towards the gate. If you expect the DC voltage at the input you got to protect the pot too. Also, the JFET's gate must have a firm DC reference to GND so you shouldn't interrupt it with a cap. Or, you can add another 100k - 1M resistor between the JFET's gate and the GND so you can put put the cap wherever you like (as long as gate has a firm DC reference to GND).



Quote:
Originally Posted by maouna View Post
Regarding the 470ohm gate stopper resistor,should i ommit it ithis case? i have already made space for the resistor in my small pcb.
As you wish - it doesn't make a difference in this case, as I already wrote.
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Old 24th February 2019, 09:22 AM   #223
maouna is offline maouna  Greece
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Quote:
Also, the JFET's gate must have a firm DC reference to GND so you shouldn't interrupt it with a cap......
I thought the gate was DC referenced to GND through resistors R1-R4 series combination so i wouldnt need 100k - 1M resistor between the JFET's gate and the GND to put the cap wherever i like.Do i still need that 100k - 1M resistor you suggest? My plan was to not use a pot at all but include an input 10u cap bypassed with 100n wima.
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Last edited by maouna; 24th February 2019 at 09:34 AM.
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Old 24th February 2019, 04:00 PM   #224
juma is offline juma  Serbia
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R1-R4 works too. I just did not see it. Many winters passed since that preamp...
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Old 24th February 2019, 04:03 PM   #225
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Quote:
Originally Posted by juma View Post
R1-R4 works too. I just did not see it. Many winters passed since that preamp...
But you will still need the pot somewhere before the preamp's input. You do not want to drive it into clipping.
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Old 7th June 2019, 03:29 PM   #226
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Juma4-Bs170-37.4V.asc

Juma4-Bs170-37.4V.jpg

Juma4-Bs170-48.asc

Juma4-Bs170-48V.jpg

Juma4-Bf862-Bs170.jpg

While I wait to BF862 to arrive I was impatient and first redraw the schematic to me understanding way and then make minor changes to can work with BS170 instead of BF862.
I need voltage swing of ~12Vpp for SEWA preamplifier. I make this for rail supply of 48V, but when I finished the building realized that I have only 37.5V and changed the schematic again. I was intended get 13mA on source of BS170.
Now it works, on left channel have 13mA on right only 10mA. Looks like that I must put trimmer pot instead R5 to fine adjust.
I share this because I am very pleased how it sounds. I get little warming and softly sound. This is my best sounding preamplifier yet built. I was build Bridge of Zen and Apex Fet preamplifier which sounds very precise and clear but they have no softness what I hear with this preamplifier .
I do not have much knowledge about electronics, maybe I put some wrong values somewhere, so if somebody has better suggestions I will accept that.
I only wish to get warm, wide and soft sounding preamp.
Soon I'm intend going to do this same preamplifier with the j310 to see what's changing in the sound image.
Thanks Juma.
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Old 11th June 2019, 05:19 PM   #227
TungstenAudio is online now TungstenAudio  United States
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Default Gyrator Son of ZV9 for M2x IPS

Hi Juma,
I have a different application in mind for this circuit. I would like to have an input stage (IPS) with a small amount of gain for the M2x amplifier. I started working with the Bride of Zen circuit, then realized there was not practical way for this to drive the Edcor WSM 600:15k transformer that the M2 uses for its main voltage amplification. The gyrator loaded circuit that you have described in post #24 of this thread seems much better suited for this application.

I have attached a modified version of the gyrator loaded Son of ZV9 that I would like to try as an IPS module for my M2x. I have made transistor substitutions based on what I have available, and what might handle the higher power supply voltage in this application. This circuit just barely fits in the space that is available for the IPS boards. The main board has a 1k input resistor followed by a 100k shunt to signal ground, so I omitted that in the IPS circuit. I also omitted the output load resistor, as the Edcor transformer already represents a heavy load. I figured the ZVN3310A would be more capable of driving the transformer, but I have a small number of BS170 Mosfets if necessary. I have also substituted a trimmer resistor in place of the 68k to allow adjustment as necessary. I am hoping for a gain of about 6 dB, which will be added to the 14dB of the autoformer configuration.

Does this look like a reasonable adaptation?
Thank you,
James
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Old 11th June 2019, 05:43 PM   #228
juma is offline juma  Serbia
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Hi James,
sorry but you can not use enhanced mode MOSFET as a direct replacement for depleted mode JFET.
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Old 11th June 2019, 08:20 PM   #229
TungstenAudio is online now TungstenAudio  United States
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Perhaps my wording was not clear. I was hoping that my schematic would indicate what I was planning to do.
In place of the BF862, I would like to substitute a 2SK170 JFet. I have some genuine Toshiba parts in the 10mA range for Idss. The BF862 is very difficult to build with, so I am hoping that the K170 will be a reasonable replacement. I also have some Linear Systems PN4416 and J309 devices available if those would be a better match for this circuit. I can probably sort a few parts to get some in the 10mA range.
I wanted to use the ZVN3310 in place of the BS170. The Zetex part has similar Gate-Source threshold, similar Transconductance, with higher current and power dissipation. I was hoping it would provide better drive into the Edcor transformer.
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Old 11th June 2019, 09:55 PM   #230
juma is offline juma  Serbia
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yes, k170v will do just fine instead of bf862
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