I put this 2 JFET amp in a case quickly so that I can take it with me out of the lab to enjoy music outside the lab. I am using a 24v 5amp SMPS, a Juma cap multiplier, and qnty 16 x 2200uF 25v cap bank for 35mF, that cap bank is connected via 0.33R to 5 x 2200uF cap bank 11mF after the 4700uF cap connected to the Mx. The 16 cap bank has 3.1mOhm ESR - this is good because it about matches the Rdson of the LU1014D for unmitigated bass authority.The 50k volume pot is mounted on a bare veroboard for addition of future cross-feed filter.
Hi X,
Is this how you connect the cap bank?
SMPS -> Mx -> 11mF -> 0.33R -> 35mF cap bank
I put this 2 JFET amp in a case quickly so that I can take it with me out of the lab to enjoy music outside the lab. I am using a 24v 5amp SMPS, a Juma cap multiplier, and qnty 16 x 2200uF 25v cap bank for 35mF, that cap bank is connected via 0.33R to 5 x 2200uF cap bank 11mF after the 4700uF cap connected to the Mx. The 16 cap bank has 3.1mOhm ESR - this is good because it about matches the Rdson of the LU1014D for unmitigated bass authority.
Hi X,
Is this how you connect the cap bank?
SMPS -> Mx -> 11mF -> 0.33R -> 35mF cap bank
Almost, I forgot to mention that there is a 0.47R between CMx and 11mF for additional filtering.
SMPS --> CMx w/ 4700uF --> 0.47R --> 11mF --> 0.33R --> 33mF
Zetex publishes their models - I an not sure if it's as simple as pasting relevant code into schematic ?
http://espice.ugr.es/espice/src/modelos_subckt/ZMODELS.LIB
I am working on a slick little Altoids tin amp board using the ZVN4306 and BF862. I need to figure out values in order to set bias on MOSFET correctly - I am aiming for circa 60mA.
Here is half of the layout using a sharpie marker.
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Thanks X!
I have come to the conclusion after examinining Elfishi's schematic with dissimilar BF862s that there is not much point using 10R source resistors. The distortion is no better, and the Zout is higher. Always best to match the BF862s for idss within 5%, that is good enough.
I will fiddle with this ZVN4306 later today...... thank you for sending them on.
Hugh
I have come to the conclusion after examinining Elfishi's schematic with dissimilar BF862s that there is not much point using 10R source resistors. The distortion is no better, and the Zout is higher. Always best to match the BF862s for idss within 5%, that is good enough.
I will fiddle with this ZVN4306 later today...... thank you for sending them on.
Hugh
As far as my experience goes, no. I had to create dedicated ZTX**** schematic symbols and point them to the model (in my SUB folder) to get my simulations to work. Perhaps there is another way, though, that I did not try.
At any rate, the .subckt is harder to use than the .model.
Pocket Class A First Sound
Well, I had a productive night. The BF862 and ZVN4306 amp is now singing. I had to adjust the input source resistor to 100R to get enough voltage at the gate of the MOSFET. I am running qnty 4 x 470R SMT source resistors in parallel (123R) on the ZVN MOSFET for a bias current of 67mA. I left a lot of copper plane for a heatsink for the MOSFETs.
Circuit follows this schematic but with LU1014D replaced with ZVN4036 SOT-23 but with R2=100R and R7=123R, R6 = 220R, and output C is 1000uF:
The SMT parts on on one side, which I will put in thermal contact with the bottom of the case. The through hole components are on top and will be visible,
Just tested a few songs - sounds very promising - nice bass, clear highs, smooth mids. Running from two 9v Li-ion batteries in series for 18v supply.
The board has been tested to fit in an Altoids tin with two 9v batteries perfectly.
Final layout before acid etch:
SMT side (I wanted to use nice 47uF OSCONs but change of plans put SMT on flat side next to case so no room):
Top side:
First sound test:
It's running now and temperatures are doing OK - not too hot. Sound is very nice.
Zetex publishes their models - I an not sure if it's as simple as pasting relevant code into schematic ?
http://espice.ugr.es/espice/src/modelos_subckt/ZMODELS.LIB
I am working on a slick little Altoids tin amp board using the ZVN4306 and BF862. I need to figure out values in order to set bias on MOSFET correctly - I am aiming for circa 60mA.
Here is half of the layout using a sharpie marker.
Well, I had a productive night. The BF862 and ZVN4306 amp is now singing. I had to adjust the input source resistor to 100R to get enough voltage at the gate of the MOSFET. I am running qnty 4 x 470R SMT source resistors in parallel (123R) on the ZVN MOSFET for a bias current of 67mA. I left a lot of copper plane for a heatsink for the MOSFETs.
Circuit follows this schematic but with LU1014D replaced with ZVN4036 SOT-23 but with R2=100R and R7=123R, R6 = 220R, and output C is 1000uF:
The SMT parts on on one side, which I will put in thermal contact with the bottom of the case. The through hole components are on top and will be visible,
Just tested a few songs - sounds very promising - nice bass, clear highs, smooth mids. Running from two 9v Li-ion batteries in series for 18v supply.
The board has been tested to fit in an Altoids tin with two 9v batteries perfectly.
Final layout before acid etch:
SMT side (I wanted to use nice 47uF OSCONs but change of plans put SMT on flat side next to case so no room):
Top side:
First sound test:
It's running now and temperatures are doing OK - not too hot. Sound is very nice.
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Last edited:
Some more mods with caps and resistors which improved clarity and bass extension:
http://www.diyaudio.com/forums/head...lass-headamp-without-heat-11.html#post4944606
Superb sound - wonderful bass and clarity now.
http://www.diyaudio.com/forums/head...lass-headamp-without-heat-11.html#post4944606
Superb sound - wonderful bass and clarity now.
X, have you looked at the Panasonic CT / CX series? Also polymer but in a much smaller package (7.3 x 4.3 x 1.9mm), and decent voltages
https://industrial.panasonic.com/cdbs/www-data/pdf/ABE0000/ABE0000C49.pdf
Thanks for the tip! I will have to pick some up on my next order of parts.