Simple Symetrical Amplifier

[Salas]

Do you notice degradation even if you have a small cap in parallel...

...any thoughts on that ?

mike

I have seen a 0.1uF MKT capacitor across all cathode auto-bias fuses in all Jadis tube equipment.

 

[Esperado]

I have seen a 0.1uF MKT capacitor across all cathode auto-bias fuses in all Jadis tube equipment.

I wonder what can be the purpose of this cap ? To prevent the fuse from blowing with very high HF ? To prevent the spark when the fuse blows ?

 

[Salas]

Spark I guess is the primary goal, as I have seen highly biased tubes failing violently near their life's end. I wouldn't be surprised if that most respected artisan French tube amps company has some subjective sonic beliefs about using them also.

 

[mikelm]

The purpose of the cap is to partially absorb any noise caused by poor connection between fuse & fuse holder

 

[Salas]

That, or some little HF part of non linear cathode feedback signal added by the fuse as it merrily passes bias swing in series with the cathode resistor? They use resistive auto-bias in almost all their models.

 

[dipolar]

This thread has taken me into different dimension of world.

@Shaan ,Awesome PCB soldering/wiring there, beautiful !

 

[homemodder]

we await with interest

Below find input section of 1) 1995 German Class H high power PA amp Input circuit. (See the similarity of the amp presented in this thread.
2) Sony N1 CFB from 90s. (I like this circuit, see the twist in the vas.

Pioneer models still to come, I am having problems getting schematics in electronic form.

 

[DIGORA]

Do you know the Pioneer Super Linear Circuit ?

This circuit could be adapted to use a current feedback as SSA?


the Headphone amplifier

 

[dadod]

Below find input section of 1) 1995 German Class H high power PA amp Input circuit. (See the similarity of the amp presented in this thread.
2) Sony N1 CFB from 90s. (I like this circuit, see the twist in the vas.

Pioneer models still to come, I am having problems getting schematics in electronic form.

2) That is Hawksford enhaced cascode.

 

[Esperado]

Do you know the Pioneer Super Linear Circuit ?
This circuit could be adapted to use a current feedback as SSA?
the Headphone amplifier

If i make no mistake, the Pioneer Super Linear circuit used no global negative feedback, apart DC servo. So, the response would be: no.

 

[DIGORA]

Bonjour Christophe

http://www.audiodesignguide.com/Headphone_amp/A-09_inputstage.JPG

This schematic look like current FeedBack but with Jfet

 

[homemodder]

Do you know the Pioneer Super Linear Circuit ?

This circuit could be adapted to use a current feedback as SSA?


the Headphone amplifier

Doesnt need to be adapted, it is current feedback, thats pioneer A9 like I mentioned in previous post, dates back to 1993 and one of the very best amps ever produced. The technology was quite advanced comparing european or american amps. Price was around 8000 US dollars. I dont need to post that one anymore then.

 

[homemodder]

2) That is Hawksford enhaced cascode.

Indeed, THD figures for that amp are very good, Ive got 7 of these amps, 5 see daily use in bars (14 hours a day), 2 spare. They are however very reliable so spare ones are still boxed and never used. Its practically a SSA with hawksford cascode. Output uses Class H circuitry, bipolar and Mosfet.

 

[DIGORA]

In fact I would like BJT input as SSA

 

[homemodder]

Theres not much of a choice nowadays anyway, there are no more toshiba complementary JFETs around, the ones that can be used in such a input stage have to be purchased in 1000 s to maybe get 100 pairs matched to Idss and gm.

 

[Esperado]

Bonjour Christophe
http://www.audiodesignguide.com/Headphone_amp/A-09_inputstage.JPG
This schematic look like current FeedBack but with Jfet

Yes, it is. Nice schematic. Very clever.
No need for adaptation if this is the pioneer you were talking of. (The shematic i founded with google was absolutely different).
[edit]Why did-you like to change input's JFETs by a BJT ? They have their own advantage (noise factor/bandwidth/impedance)..

 

[DIGORA]

This schematic ( with 2sk1058 ) could have the same speed as your AMP ?

I have matched 2sk246Y 2SJ103Y

 

[Jay]

Do you know the Pioneer Super Linear Circuit ?

This circuit could be adapted to use a current feedback as SSA?

the Headphone amplifier

Bonjour Christophe

http://www.audiodesignguide.com/Headphone_amp/A-09_inputstage.JPG

This schematic look like current FeedBack but with Jfet

Which one have you asked in the first place, the headphone amp or the Pioneer? The Pioneer is current feedback, but "less CFB" than the SSA.

In fact I would like BJT input as SSA

Same here. And I think the SSA is better than the headphone amp (just use the same BD139/140). The head-amp "trick" to lower distortion has consequence with the sound (tho not easily recognized). It is better using a string of dual silicon diodes like in the SSA. The resulting THD (and offset) will not as low as the head-amp but who needs super long trailing zeros anyway.

 

[DIGORA]

Hello Jay,

I pasted this site link to illustrate my request about the SLC

I would like to make a very fast and linear amplifier with lateral mosfet output 2SK1058.

The speaker : http://www.hometheaterhifi.com/imag...s/magneplanar-1.7-speaker-impedance-phase.gif

 

[shaan]

Hi digora.

Go for SSA, which is damn fast, super linear and has large power output.