Heater voltage filtering.

[Khron]

The drawing shows that the South-West is disconnected, as I suggested.

Whoopsie, my bad - due apologies The circled earth point stole my attention on the commute...

 

[vmanj]

Can a battery be used as an alternative to "noiseless heating voltage"?

 

[abbey road d enfer]

Can a battery be used as an alternative to "noiseless heating voltage"?

Why not?
The first "wireless" sets used batteries for all voltages, quite often 2 or 4V for heaters and about 80V for B+ (the name B+ originates from "battery positive").
Later when automobile used 6 or 12V batteries, vacuum tubes were adapted to this new de facto standard.

 

[ruffrecords]

Later when automobile used 6 or 12V batteries, vacuum tubes were adapted to this new de facto standard.

And the first switched mode power supplies (using vibrators) were invented.

Cheers

Ian

 

[Matador]

A mod I've done on this PSU was to cut the trace between C6 and C7, and solder in a resistor there. If memory serves, you are pulling around 300mA and cannot loose more than 4V, so ~5 ohms is a good first try. 5 ohms into the stock 1000uF is about 20dB down at 120Hz, which improves the 7806 from 60dB to 80dB.

You can also replace the 1000uF with a 4700uF (the layout has space), which is worth another 10dB of filtering at 120Hz.

 

[vmanj]

I liked the option of a fixed bias on the cathode more than on the grid.
And least of all I liked the sound with auto-bias ..
Well, it's a matter of taste..

It’s just that the option with a battery is much easier for me than making a low-voltage stabilized and “clean” heating power supply, so that it can also be used for a fixed cathode bias ..

For variation, you can try this ..

 

[vmanj]

A mod I've done on this PSU was to cut the trace between C6 and C7, and solder in a resistor there. If memory serves, you are pulling around 300mA and cannot loose more than 4V, so ~5 ohms is a good first try. 5 ohms into the stock 1000uF is about 20dB down at 120Hz, which improves the 7806 from 60dB to 80dB.

You can also replace the 1000uF with a 4700uF (the layout has space), which is worth another 10dB of filtering at 120Hz.

I tried another power supply from Nady TCM 1050.
There filtering is about the same as you suggested.
But unfortunately the hum and background still remained ..

 

[Matador]

But unfortunately the hum and background still remained

Still remained? As in, it was unchanged?

 

[abbey road d enfer]

I tried another power supply from Nady TCM 1050.
There filtering is about the same as you suggested.
But unfortunately the hum and background still remained ..

Well, if the grounding arrangement is as much f...ed up than in the other, it's no wonder.
You never reported if arranging the grounding as I suggested brought any improvement.

 

[Gus]

vmanj

In this thread and another you ask questions and do not seem to listen to what people post.

IIRC all your questions have been covered in the past in older threads at this forum

The biasing stuff can be seen in schematics or on the web there is nothing new that you posted.

power supply design for low noise can be found in books.

Some of the replies have good information

Anyway there are "better" ways to heat and bias in some circuit fragments that have not been posted in the threads

 

[vmanj]

Well, if the grounding arrangement is as much f...ed up than in the other, it's no wonder.
You never reported if arranging the grounding as I suggested brought any improvement.

Unfortunately, I did not try your option, because. I've already remade the microphone in a different way.
If I return to the previous microphone circuit, I will definitely try and write the result.

 

[vmanj]

vmanj

In this thread and another you ask questions and do not seem to listen to what people post.

IIRC all your questions have been covered in the past in older threads at this forum

The biasing stuff can be seen in schematics or on the web there is nothing new that you posted.

power supply design for low noise can be found in books.

Some of the replies have good information

Anyway there are "better" ways to heat and bias in some circuit fragments that have not been posted in the threads

Thanks for the guidance.

But I'm not a professional radio electronics, but just a fan of experimenting.
That's why I came to the forum, which is called DIY, and not to the forum of engineers.

In fact, I am very grateful to the participants of this forum!

 

[vmanj]

Still remained? As in, it was unchanged?

Very little less..

 

[dmp]

Just ignore the crabby people who talk in riddles and criticize others.

 

[Matt Nolan]

Why not?
The first "wireless" sets used batteries for all voltages, quite often 2 or 4V for heaters and about 80V for B+ (the name B+ originates from "battery positive").
Later when automobile used 6 or 12V batteries, vacuum tubes were adapted to this new de facto standard.

I'm sure I read somewhere (Morgan Jones?) that using batteries for bias voltage in a valve mic is not as good an idea as you might think with respect to noise. Less hum of course than a rectified and smoothed AC supply, but it is not free of noise. Chemical cells have a grainy current which is noticeable when you apply a lot of gain to it.

Fine for heating, but heating and biasing, maybe not.

 

[vmanj]

I'm sure I read somewhere (Morgan Jones?) that using batteries for bias voltage in a valve mic is not as good an idea as you might think with respect to noise. Less hum of course than a rectified and smoothed AC supply, but it is not free of noise. Chemical cells have a grainy current which is noticeable when you apply a lot of gain to it.

Fine for heating, but heating and biasing, maybe not.

Not for heating, only for bias (cathode)..

 

[Tubetec]

Battery definately cant be considered noiseless ,mush and hum can still creep in ,
Ive used a Ni cad or Nimh cell in the cathode of preamps and it works well enough , presenting only a fraction of an ohm at the cathode instead of the 5 ohms of the series dropper scenario , the anode current of the tube itself maintains the battery ,but regular usage is required or else your doing a check with a meter

A coin cell supplying grid bias in a tube mic might be worth a look , if you were really careful about your leakage resistance a coin type cell might last 10 years or more , downside of any kind of battery is if left unattended for a period of time voltage drop and chemical leakage might become an issue .
Maybe a tube mic with an externally accessible slot for the grid battery , ie when not used for prolonged periods the coin cell is removed .A negative wired 1.5v cell lines up just about right with where an EF86 grid wants to be with cathode grounded .

 

[Tubetec]

It works ,and doesnt leave you needing to resolve any grounding loops.

 

[vmanj]

Battery definately cant be considered noiseless ,mush and hum can still creep in ,
Ive used a Ni cad or Nimh cell in the cathode of preamps and it works well enough , presenting only a fraction of an ohm at the cathode instead of the 5 ohms of the series dropper scenario , the anode current of the tube itself maintains the battery ,but regular usage is required or else your doing a check with a meter

A coin cell supplying grid bias in a tube mic might be worth a look , if you were really careful about your leakage resistance a coin type cell might last 10 years or more , downside of any kind of battery is if left unattended for a period of time voltage drop and chemical leakage might become an issue .
Maybe a tube mic with an externally accessible slot for the grid battery , ie when not used for prolonged periods the coin cell is removed .A negative wired 1.5v cell lines up just about right with where an EF86 grid wants to be with cathode grounded .

As I understand it, the battery in the cathode should ONLY be rechargeable (1.2..1.5V) - e.g. lithium battery AA or AAA ?

The coin type element cannot be used. because They only come in 3V...

 

[Tubetec]

Yes, Id only go with the rechargeable types for cathode bias as its has to safely withstand the anode current of the tube under long term usage , I proportion the cell in relation to the anode current of the tube , so it just keeps topped up at around 1/10th nominal charge current .
coin cell is fine for grid though , also in 1.5v format .