SE Electronics Z3300a

[micolas]

Yes my friend had just bought the same one from Ali ! but I never used a scope in my entire life... maybe it's not so complicated to learn how to use it ?
(I put one item "in my basket" )

it's very easy
like a breeze

 

[Emmathom]

it's very easy
like a breeze

Does it do "send & return" ? I mean it generates a sine-wave and analyse it ?

 

[micolas]

Does it do "send & return" ? I mean it generates a sine-wave and analyse it ?

For this price?
It is worth several times more!

no, but we have enough signal generating sources
it measures very precisely the inductance of uH and capacitors of a few pF and transistors, etc., etc

 

[Emmathom]

Great ! Yes we have plenty of choice for signal generator...

I come back to the subject of the SC1100: the source decoupling capacitor, 22uF, it passes the negative half-waves of the signal there, right? as for the decoupling capa. of a tube's cathode... right ?
so the quality of this capacitor is important (in my tube assemblies, when I need to decouple, I only do it with Elna Silmic II) > in my last Quad Tube pre the cathodes (1frst & 2nd stages) are not decoupled by choice...

But so, what happens if you don't decouple the source resistor ? you loose gain but you get "less distorsion" and more linear signal ?

 

[micolas]

okay,
Bon appétit
Good evening!

 

[micolas]

But so, what happens if you don't decouple the source resistor ? you loose gain but you get "less distorsion" and more linear signal ?

gain and low frequency response are reduced

 

[Emmathom]

gain and low frequency response are lost

so it's not the same as tubes...

In my Quad :
12AY7 K.by x 12AU7 K.by > +47dB
12AY7 K.unby x 12AU7 K.by > +44dB
12AY7 K.by x 12AU7 K.unby > +42dB
12AY7 K.unby x 12AU7 K.unby > +39db
That's my choice (last K unby) because I've got plenty of gain when associated with the EA2622 CAPI (1:7 / +17dB)
So 39 + 17 = +56dB > with static mics its alright (I don't often use ribbon or dynamic > or if so it is with MicBooster from KT > +20dB)

 

[micolas]

Among transistors, jFETs have the closest behavior to tubes (configured as) triodes
25-30 years ago I built with jFETs (J201,2N5457) the famous Marshall, Bogner, Mesa-Boogie, Rivera etc. pre-amplifiers and obtained the tube sound in pedal effects.
The most famous guitar pre of amp of all time is reproduced here with jFETs
Marshall JCM800.

 

[micolas]

...something like that!

 

[Emmathom]

Adjust the VR until the limitation disappears and the sine wave is again symmetrical and perfect. Increase the volume of the injected signal again and repeat the procedure. Make sure that the + and - branches of the sinusoid are symmetrical, limit at the same level.

I have this Waves InPhase plug-in installed in my Logic Pro

But I think the Melda is more accurate @ appropriate...
https://www.thomann.de/fr/meldaproduction_mmultianalyzer.htm

 

[Emmathom]

Hi !
I tried to replace the original transformer but it does not work and it must short circuit because I lose my supply voltages coming from 48v...
So I replaced the Monacor wired according to diagram "A" and here instead of -6dB compared to the original microphone I have +4dB (i.e. a gap of 10dB!)
I'm also thinking of changing the Tr of the other microphone for a good balance between the two
Now I'm going to bias the 2 Jfets according to the method recommended by @micolas with REW's scope and tone generator
To be continued...

 

[Emmathom]

First biasing of the modified mic :
- 56pF load / sine wave 1kHz thru 10nF
The signal is equal postive & negative alternances with a R of 7,5kΩ (+1,8KΩ R source)
The signal is saturated at 92mV (measured with DMM at smartphone output) and is clean to 75mV

 

[Emmathom]

With the proper bias the level has leveled down and fits now the original mic
on the picts, one can see that without any R after the R source 1,8KΩ the signal has more neg. than pos. / with the R 6,8KΩ the signal seems equal (but with less gain)

So now, this modifyed mic's electronic is done : will install the Arienne k47-flat (but first I got to work on the original one > change the transformer & bias the Fet)

Of course I will record with the pair (in omni & cardio) before changing the capsules...

 

[micolas]

With the proper bias the level has leveled down and fits now the original mic
on the picts, one can see that without any R after the R source 1,8KΩ the signal has more neg. than pos. / with the R 6,8KΩ the signal seems equal (but with less gain)

So now, this modifyed mic's electronic is done : will install the Arienne k47-flat (but first I got to work on the original one > change the transformer & bias the Fet)

Of course I will record with the pair (in omni & cardio) before changing the capsules...

Did you make simultaneous recordings with the stock microphone and the modified one, before changing the capsules, transformer, etc.?

 

[micolas]

Hi !
I tried to replace the original transformer but it does not work and it must short circuit because I lose my supply voltages coming from 48v...
So I replaced the Monacor wired according to diagram "A" and here instead of -6dB compared to the original microphone I have +4dB (i.e. a gap of 10dB!)

As I told you, going from a transformer ratio of 2:1 to 1.5:1 will increase the output level.

 

[Emmathom]

It's on my to-do list : record as it is now (one modified - one not) then the 2 modified (Tr & bias) before changing the capsules.
What do you think of my Fet biasing ? Does it seem ok for you ?
As I said I rejoigned the original gain level but the signal wave is clean with the add of 6,8KΩ

 

[micolas]

Hi !
I tried to replace the original transformer but it does not work and it must short circuit because I lose my supply voltages coming from 48v...

The diagnosis was correct:
The insulation resistance of the secondary of the original transformer is compromised

 

[micolas]

What do you think of my Fet biasing ? Does it seem ok for you ?
As I said I rejoigned the original gain level but the signal wave is clean with the add of 6,8KΩ

measure the voltages in the important points, including the transistors, after BIAS ing, to be able to compare them with the original

 

[micolas]

measure the voltages in the important points, including the transistors, after BIAS ing, to be able to compare them with the original

After each change or adjustment, you have to make new measurements, tests, records, comparisons, etc.,to make observations and analyze
Only then will you know the real effect of each change.
All this is very helpful for you and for everyone who follows the subject.

 

[micolas]

After re-Biasing how did the tonal character of the modified microphone compare to that of the stock microphone?