Anyone tested the SHO PCB from tayda?

[duck_arse]

willi, as can be seen in the sho circuit, the gate bias is derived by dividing the drain voltage, via R2//R1, and results in half the drain voltage appearing at the gate.



the amz mosfet booster is functionally the same, except the gate bias is applied via R3, and derived by the "noiseless bias" method, R1//R2//C3. in this instance, the voltage "Vr" will be 5V5, no matter what happens at the drain.



if you replace R1//R2 with a 100k trimpot, and take the Vr from the wiper, you can adjust the bias voltage for individual devices. (this circuit also avoids the supposedly "ok" crackle when adjusting the gain.)

my question above was regarding the upper circuit, and whether the "drain bias" adjusts automatically per device, or if it could be far enough off to cause mis-bias.

[Les Paul Lover]

I got 5V on D, 2,32V on G and 0,05V on S. and i am running off 9.58V, does this sound right to you?

I retook all measurements last night but the internet crashed so I could give them to you.
Will try to post everything later. From memory, the BS170 were like that (2 readings, 1 with the pot fully down, 1 with the pot fully up)

Its running from my one spot power supply at 9.5v spot on:

D 4.4v to 7.7v
G 2.2v to 3.7v
S 0v to 1.7v

I will try to post full volatge readings later tonight.

[Will.mendil]

I did not think to check with the pot on different positions. Shall test when I get home. But from the looks of it I have pretty similar values to you

[Will.mendil]

I got nearly the same values as you on the transistor knob up or down. I guess the problem is else where. Could it be the amp?

[Les Paul Lover]

Just in case it helps, here are my full Vs readings:

R1
2.2v / 3.7v
0v

R2
4.4v / 7.7v
2.2v / 3.7v

R3
9.5v
4.2v /7.7v


R4
0v
0v

D1
9.5v
2.2v 3.7v

D2
2.2v / 3.7v
0v


C1
2.2v / 3.7v


C2
4.4v /7.7v
0v

Q1
4.4v /7.7v
2.2v / 3.7v
0v / 1.7v

[LucifersTrip]

with this schematic:



I have (min/max):

G: 2.81/1.49
D: 7.36/2.98
S: 2.48/.13

[HOTTUBES]

Not to derail this tread ...

How can you tighten up the SHO with the pot cranked past half way etc ??

Cause i have noticed that its a great clean tight boost below half way , but as it begins
to crest about 50% - 60% it starts to add alot of low end making it " Tubby " or " loose "
sounding .

[davent]

^Smaller output cap?

[Will.mendil]

Weirdly enough. I tried it on a different solide sta amp and the sound does not cut when the knob is turned. Maybe the issue is coming from the amp. Wired. I have checked though if the amp distorts with it. I'll wait to get y tube amp done to see how it works out

[HOTTUBES]

^Smaller output cap?

Thanks !!

[Will.mendil]

That works?

[davent]

Speculation on my part, that's why the question mark (?), but i do use a rotary switch in a pentode-preamp tube amp that changes the bass roll-off by changing the coupling cap. Is from a DC30 shematic.