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Old 16th September 2021, 11:14 AM   #91
albertNL is offline albertNL  Australia
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Join Date: Sep 2011
Location: Brisbane area
While I wait for my H2 parts to arrive, I ordered some cheap toys from Aliexpress. The idea behind this is to be able to change the voltage on the jfet repeatedly without opening the case.
A 100R multiturn pot to replace P1 and R6 and a digital voltmeters to check the voltage. No idea if it will work, but worth trying :-)
0.36'' Mini Digital Voltmeter DC 0 100V 3 wire 4 Bit Precision Voltage Meter Panel Tester For Electromobile Motorcycle Car 12V|Voltage Meters| - AliExpress
3590S 2 103L 3590S 100 10K ohm Precision Multiturn Potentiometer 10 Ring Adjustable Resistor + Turns Counting Dial Rotary Knob|multiturn potentiometer|precision multiturn potentiometeradjustable resistor - AliExpress
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Old 16th September 2021, 12:01 PM   #92
turion64 is offline turion64  United States
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Join Date: Mar 2019
Location: Trenton, NJ
Originally Posted by albertNL View Post
No idea if it will work, but worth trying :-)
Hopefully the meters are accurate.

I like my Hammond case since the top slides out so I can just leave it open until Iím happy with the voltage setting vs H2 level.

Anyone who has never made a mistake has never tried anything new. - Albert Einstein
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Old 16th September 2021, 12:06 PM   #93
HumbleDeer is offline HumbleDeer  Belgium
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hahah! Have fun.

I'm wondering if anyone has posted about the output impedance of this preamp before? I need to add a couple of NE5532 buffers after the preamp as there will be multiple outputs, some with extra potentiometers and most of them with the possibility of a tube amp being connected. Buffers would allow me to add an extra pot without changing the output impedance!

My current schematic:
Input -> H2 → Potmeter → NE5532 buffer → Controlled out
................ ⇲→ Jumper → NE5532 buffer → Pre-out (no volume control)

Anyone with any tips, shoot! Otherwise, just interested in the output impedance of the H2.
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Old 16th September 2021, 08:16 PM   #94
WKCox is offline WKCox  United States
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Location: Wisconsin
Output impedance is just a few hundred ohms. No need for an additional buffer in most use cases.
Pass Aleph J, F5, F6, M2x, Sony VFET, ACA, ACP+, B1, B1 Korg, H2 V2; Colburn BA2018; Audio Research ST-70-C3; Dynaco ST-35, ST-70; Audio Electronic Supply SE-1; Elekit TU-8500; Hagerman Bugle; Scan-Speak Solist MTM; Selah SA-1; Seas Loki; Millett Hybrid MAX
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Old Yesterday, 08:26 AM   #95
HumbleDeer is offline HumbleDeer  Belgium
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As we need a potentiometer after the pre-amp, a buffer would be preferrable just for theoretical resistance to the kind of variability that it provides. But a few hundred ohms sounds just fine then. I can work with that, thanks!
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