Hi,
I'm planning to build the amplifier here attached, and I already tested LSK170 and U440 on the bottom of the hybrid cascoded phase inverter, but I would like to know if there are other options with more gain and linearity that I can check to improve the design. More gain and linearity could permit to add some gnfb to the design, improve THD and dampening too.
Thank you in advance,
Roberto
I'm planning to build the amplifier here attached, and I already tested LSK170 and U440 on the bottom of the hybrid cascoded phase inverter, but I would like to know if there are other options with more gain and linearity that I can check to improve the design. More gain and linearity could permit to add some gnfb to the design, improve THD and dampening too.
Thank you in advance,
Roberto
I've read some threads about it (EG this one Complementary diff input with JFET and BJT cascode and this one Cascodes- the truth is out there... ), and the J113 seems one of the best candidates.
Any other suggestion?
Any other suggestion?
The new IF9030 from Interfet also looks promising, although it is very expensive at the moment and I could not find a spice model.
Another option to increase gain might be a Sziklai configuration with a jFET and a BJT at the input as shown in the schematic below.
Another option to increase gain might be a Sziklai configuration with a jFET and a BJT at the input as shown in the schematic below.
I've a newbye issue, but LTSPICE tells me that he cannot find the definition of SSM3K339R. I've saved the lib file and called the the lib file...
Thank you KlausB, it is indeed, also because I'd need two almost matched.
A BJT instead of the 12AX7? I must supply the cascode at around 450V due to the feedback configuration for the output tubes, is there anything that can be safely used and well sounding?
Hi Zintolo, example file attached. You have to edit the jfet (CTRL right click) to change "Prefix" from "JN" to "X", then change "Value" to the name of the model (NMOS_SSM3K339R) as it is a .subckt model. Note that this fet needs a positive bias voltage to conduct.
Thanks Tikiroo!
The new file is in attachment: 91 Wrms at 0,38% THD (3rd and 7th harmonics mainly).
The new file is in attachment: 91 Wrms at 0,38% THD (3rd and 7th harmonics mainly).
Code:
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+03 3.823e+01 1.000e+00 0.03° 0.00°
2 2.000e+03 4.356e-03 1.139e-04 86.84° 86.81°
3 3.000e+03 1.373e-01 3.592e-03 -2.68° -2.71°
4 4.000e+03 1.093e-03 2.859e-05 12.75° 12.72°
5 5.000e+03 4.655e-03 1.218e-04 148.06° 148.02°
6 6.000e+03 4.368e-04 1.142e-05 -89.08° -89.11°
7 7.000e+03 4.304e-02 1.126e-03 -0.90° -0.93°
8 8.000e+03 1.353e-04 3.539e-06 129.20° 129.17°
9 9.000e+03 1.190e-03 3.114e-05 89.71° 89.68°
Total Harmonic Distortion: 0.376791%(0.378500%)Although I bought 100pcs/4$ the complimentary, the cheapest I found this mosfet is on ebay from UK 5pcs/4$.
Thanks kokoriantz,
how many of them do you suggest to buy, in order to match a quartet (two per channel)?
how many of them do you suggest to buy, in order to match a quartet (two per channel)?
With transistors, I always get a matched pair from five same lot. If Mouser shipment is affordable 10pcs cost 2.6€ https://www.mouser.it/ProductDetail/Toshiba/SSM3K339RLF?qs=vPP9GyyTAo2h4IM%2B%2BLvR%2BA==.
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A BJT instead of the 12AX7? I must supply the cascode at around 450V due to the feedback configuration for the output tubes, is there anything that can be safely used and well sounding?[/QUOTE]
The BJT mentioned is not to replace the 12AX7. What I meant is a jFet (N) and a BJT(pnp) as a compound of two transistors BELOW the cascoding tube to enhance gain. The spice file I posted shows a nicely working example.
All the best for 2021
KlausB
The BJT mentioned is not to replace the 12AX7. What I meant is a jFet (N) and a BJT(pnp) as a compound of two transistors BELOW the cascoding tube to enhance gain. The spice file I posted shows a nicely working example.
All the best for 2021
KlausB
Thanks KlausB, I will try it. What if I would flip tube and SS, having the tube below and the SS on top? Are there some suggested BJTs?
Thank you, I wish the same to you and the whole forum!