Diamond Buffer - Super Buffer

[stanislav1957]

Maybe it's better to look at other variants of the diamond buffer for use in telephone amplifiers ?

 

[peranders]

What do you mean?

 

[stanislav1957]

The main drawback of the parallel amplifier with all the complexity of the circuit was not eliminated

 

[Erlend Sæterdal]

I use Diamond buffer at input of 700 w monoblocs. To isolate any problems with outputs with capacitors or TVC.

 

[peranders]

The main drawback of the parallel amplifier with all the complexity of the circuit was not eliminated

What was the drawback?

 

[stanislav1957]

Incomplete use of the power supply voltage.

 

[peranders]

If you calculate the loss of amplitude it’s around 3 dB. The benefit is low distorsion without global feedback.

 

[stanislav1957]

If you calculate the loss of amplitude it’s around 3 dB. The benefit is low distorsion without global feedback.

A simple buffer with full use of the supply voltage.For use as telephone amplifiers .
The offset voltage of a normal battery

 

[peranders]

Notice that this thread was about my design. The application is in an audio circuit and at ±15 V supply voltage.

 

[stanislav1957]

Your topic. Your rule

 

[Erlend Sæterdal]

For everybody else who was confused. I had to measure to be sure about this.

 

[peranders]

If you look at the assemly drawing, there you have a clear view where things are located.

 

[Erlend Sæterdal]

Maybe clear for you who made it. It was not clear for me. 5-7 is very unclear I think. Can not see the 6-7. And 5-7-6 is not clear I think. 5-6-7 would be a logical order.

 

[peranders]

Scroll down in the pdf with the schematic. There you have all layers and additional info including an extra detailed assembly drawing.

 

[VeightTripleDivision]

I am interested in bare PCBs, just cautios about transistor choices, as I would prefer to have those ordered from local webshop. If I understand correctly, circuit behaves well with many types of devices?

 

[kn0ppers]

You can get these fairly common transistors from NXP, Infineon, ON Semicon, Diodes Inc. and others. What manufacturers does your local webshop carry? (Most of the smaller webshops tend to focus on one or maybe two manufacturers of discrete transistors)

 

[VeightTripleDivision]

Elfa Distrelec has many manufacturers available (and so do other webshops that are operating "within country" (means that shipping is fast and cheap compared to international ones, like farnell and such). But at the same time they often lack parts as soon they appear to be "a tad special". Like current feedback opamps, power opamps, some FETs. J-FETS are quite hard to score. Recently I found like one type of p-FETs available, nothing more. Plenty of n-JFETs though. BJTs, well, it is full of them. And I read on author's website that "The pcb fits virtually any SOT23 small signal transistor and almost any SOT223 power transistor."
I will now sleep on it and keep my eye on things. I would ideally wish J-FET buffer, but if I don't succeed, I'll take this one. Thanks.

 

[peranders]

Try to find parts with fT>100 MHz, Hfe > 300 I recommend types with Hfe > 450 like the C version of all BCxxx types

 

[VeightTripleDivision]

Okay, I ordered boards.

My plan is to use 4 of these boards to buffer differential input triode based preamplifier. Simple plate followers, CRC - series MOSFET - RC PSU, approx 220VDC, 13,2k anode resistor, biased at approx 6mA. If the coupling cap is not a leaky one and input of buffer is pulled down with 1M resistor, supply ramping up within 5 seconds, should I still invest in some protection circuitry, to prevent charging coupling cap from destroying input transistors?