Regulated B+ ?

[Delta Sigma]

Has anyone used a Maida-ish design to regulate B+ for a tube mic's power supply?

I want to be able to order a batch of PCBs and then transformers from a single source and be able to use them on any tube mic project. I played with some different B+ voltages and loads (100VDC - 220VDC) with passive filtering and with a Maida regulator. The Maida adds some parts cost, but it's easy to get 100 to 220 from the same transformer.

In other words, I could buy multiple transformers like this one, without knowing what project requirements would be:
https://sklep.toroidy.pl/en_US/p/TSTA-0015001-Mains-transformer-for-tubes/632

Same transformer and same PCB for multiple different projects with a few different components.

Started thinking of this after reading the @rock soderstrom thread with an already quite versatile PSU design:
https://groupdiy.com/threads/diy-pr...ps-like-preamps-buffers-or-microphones.84324/

Passive (for B+, regulate heater) might be the smartest way to go, but I do like the idea of using the same transformer for all future projects.

 

[Drosselmeier]

I ordered 20 transformers. They cost less than $15 each. B+ was made using a passive filtering. Suitable for M251 (+120V) and U67 (+230V) circuits.

 

[Delta Sigma]

View attachment 143343
I ordered 20 transformers. They cost less than $15 each. B+ was made using a passive filtering. Suitable for M251 (+120V) and U67 (+230V) circuits.

View attachment 143344

Where did you order them from?

 

[Drosselmeier]

Where did you order them from?

Russia
Rostov-on-Don city
"Tortrans" LLC
tel. +7(863)22066602

 

[rock soderstrom]

Passive (for B+, regulate heater) might be the smartest way to go, but I do like the idea of using the same transformer for all future projects.

Here is a thread about your topic with quite good info. Check the @Kingston PSU for an active regulated B+ version.

https://groupdiy.com/threads/regulated-b-solutions.71122/#post-906408

 

[gyraf]

The Polish company "Toroidy" mentioned/linked in OP are very competent people.

They are my main supplier of power transformers - their "Audio" type designs are among the quitest I've found.

You'll want to talk to Tomasz

/ Jakob E.

 

[Delta Sigma]

Here is a thread about your topic with quite good info. Check the @Kingston PSU for an active regulated B+ version.

https://groupdiy.com/threads/regulated-b-solutions.71122/#post-906408

Awesome. This is a lot simpler than the Maida, and I'd still achieve the wide range of loads from the same transformer. I really gotta start paying more attention to the Drawing Board.

 

[rock soderstrom]

Awesome. This is a lot simpler than the Maida, and I'd still achieve the wide range of loads from the same transformer. I really gotta start paying more attention to the Drawing Board.

I always wanted to build this circuit and merge it with my doubler heater-PSU linked above and then compare it directly in a microphone or preamp.

Here is my first draft for a PCB, what do you think? Sorry for the rough sketch. Diodes are UF4007, most electrolytic capacitors are 33uF/450V because I have a lot of them. I would like to install the LED as drawn, any cons?

How many dB ripple rejection would such a circuit have? We need Ian (@ruffrecords), I still can't work it out


R1,R2 = 1K for 10mA total current

 

[Delta Sigma]

I always wanted to build this circuit and merge it with my doubler heater-PSU linked above and then compare it directly in a microphone or preamp.

Here is my first draft for a PCB, what do you think? Sorry for the rough sketch. Diodes are UF4007, most electrolytic capacitors are 33uF/450V because I have a lot of them. I would like to install the LED as drawn, any cons?

How many dB ripple rejection would such a circuit have? We need Ian (@ruffrecords), I still can't work it out

View attachment 143437
R1,R2 = 1K for 10mA total current

I haven’t had a chance to look closely (film enlargement night tonight), but for a PCB, I think it’s worth having the option of a C12 style bias. Jumper instead of resistor when not needed.

I also had the thought of adding a ‘PTP’ like section to the PCB. Pads for components and wires to allow for resistors for relay switching, polar pattern voltage dividers, and switchable filters for cathode followers.

 

[rock soderstrom]

I think it’s worth having the option of a C12 style bias. Jumper instead of resistor when not needed.

I also had the thought of adding a ‘PTP’ like section to the PCB. Pads for components and wires to allow for resistors for relay switching, polar pattern voltage dividers, and switchable filters for cathode followers.

That sounds like an interesting project, I'm looking forward to seeing how it is implemented.

I'm going to make my PCB very basic for now, for use with small preamps, buffers and also microphones.

 

[ruffrecords]

I always wanted to build this circuit and merge it with my doubler heater-PSU linked above and then compare it directly in a microphone or preamp.

Here is my first draft for a PCB, what do you think? Sorry for the rough sketch. Diodes are UF4007, most electrolytic capacitors are 33uF/450V because I have a lot of them. I would like to install the LED as drawn, any cons?

How many dB ripple rejection would such a circuit have? We need Ian (@ruffrecords), I still can't work it out


R1,R2 = 1K for 10mA total current

Start with C1 and work out the raw pp ripple across it from dV = i / (C x f)

dV is the ripple voltage, i is the current, C the reservoir capacitance and f is 100Hz or 120Hz depending on your local mains supply.

So for C = 33uF, f = 100Hz and i = 10mA we get dV = 3.03 volts peak to peak so about 1V rms

The attenuation of each 1K/33uF RC stage is 2 x PI x f x R X C times = 20.73 times or about 26dB so the two stages should give you about 52dB of ripple reduction.

You could usefully increase the value of all three 33uF capacitors to 100uF which would reduce the raw ripple by about 10dB and increase the ripple reduction of each RC stage by a similar amount so the ripple would be around -80dBV when it enters the capacitance multiplier stage.

Cheers

Ian

 

[rock soderstrom]

Start with C1 and work out the raw pp ripple across it from dV = i / (C x f)

dV is the ripple voltage, i is the current, C the reservoir capacitance and f is 100Hz or 120Hz depending on your local mains supply.

So for C = 33uF, f = 100Hz and i = 10mA we get dV = 3.03 volts peak to peak so about 1V rms

The attenuation of each 1K/33uF RC stage is 2 x PI x f x R X C times = 20.73 times or about 26dB so the two stages should give you about 52dB of ripple reduction.

You could usefully increase the value of all three 33uF capacitors to 100uF which would reduce the raw ripple by about 10dB and increase the ripple reduction of each RC stage by a similar amount so the ripple would be around -80dBV when it enters the capacitance multiplier stage.

Cheers

Ian

Many thanks for the comprehensive explanation, Ian!

Now I know roughly how to fish! I'm still not quite sure what the Kingston variable voltage reference adds in terms of ripple reduction.


I don't quite understand fully this circuit yet, I see it more as a regulator, the zener diode (plus the trimmer) gives the voltage reference for it. If this is a capacitance multiplier, then I can easily increase C1 (in the Kingston circuit) to 33uF, right?

To optimize my circuit a bit more I suggest to add another 33uf/1K RC filter, simply because I don't have 100uf capacitors at hand, so according to your calculation I would get about 78dB ripple filtering before it goes into the Kingston circuit. That should be enough for a clean B+ voltage, right?

Thanks again for your support!

 

[Khron]

I don't quite understand fully this circuit yet, I see it more as a regulator, the zener diode (plus the trimmer) gives the voltage reference for it. If this is a capacitance multiplier, then I can easily increase C1

It's technically both. Or rather, a cap multiplier with a zener clamp for the "reference".

Here is a simple capacitance multiplier as I know it as an example.

That's not a capacitance multiplier at all - rather a zener-based discrete linear regulator (that just happens to hace a capacitor in parallel with the zener - almost pointlessly, by the way).

https://sound-au.com/articles/regulators-2.htm#s2

"While it's often seen, adding a capacitor in parallel with a zener diode is close to useless because their dynamic resistance is very low, so the cap doesn't achieve anything useful."

so according to your calculation I would get about 78dB ripple filtering before it goes into the Kingston circuit.

Surely it wouldn't take THAT long to put this together in LTspice and run an .ac simulation and get some numbers, right?

 

[rock soderstrom]

It's technically both. Or rather, a cap multiplier with a zener clamp for the "reference".

Thanks!

That's not a capacitance multiplier at all - rather a zener-based discrete linear regulator (that just happens to hace a capacitor in parallel with the zener - almost pointlessly, by the way).

https://sound-au.com/articles/regulators-2.htm#s2

Thanks again, I had the wrong picture attached, which I have now deleted because it was wrong.

Surely it wouldn't take THAT long to put this together in LTspice and run an .ac simulation and get some numbers, right?

I don't use LtSpice, I didn't get on very well with it. Nasty GUI...

Basically, we meet here to discuss our favorite topic, Khron. Not all of us are geniuses (like you) , so we ask questions about things we don't know (or aren't really sure about). I think that's perfectly normal and also one of the reasons for a specialized forum. You could find out almost everything yourself by googling, simulating, reading countless books etc. which we do to some extent. On the other hand, we've all asked questions here that are very obvious, including you.

 

[Khron]

Basically, we meet here to discuss our favorite topic, Khron. Not all of us are geniuses (like you) , so we ask questions about things we don't know (or aren't really sure about). I think that's perfectly normal and also one of the reasons for a specialized forum. You could find out almost everything yourself by googling, simulating, reading countless books etc. which we do to some extent. On the other hand, we've all asked questions here that are very obvious, including you.

Flattery will get you nowhere!.. It's weird to be someone's favourite discussion topic, though

That being said, i usually reach out for help only after i've burned through all the ideas i could come up with on my own, but... maybe i'm just weird like that

 

[rock soderstrom]

Flattery will get you nowhere!.. It's weird to be someone's favourite discussion topic, though

That being said, i usually reach out for help only after i've burned through all the ideas i could come up with on my own, but... maybe i'm just weird like that

No idea what you're talking about and what that's supposed to mean. I don't see any added value for this thread in your last post. I think you should stick to the topic...

 

[Delta Sigma]

I too had a rough time with LT Spice. Even worse for me, I have a Mac and the UI is terrible. I started using Easy EDA's web sim. It's UI is way better than LT Spice, but it doesn't have a component lookup, which can be frustrating. The web interface is nice to be able to work on it at home, then on breaks at work.

I was making progress on some sims (+6V, -6V, 100-240V Maida) but gave up after a while.

 

[rock soderstrom]

I too had a rough time with LT Spice. Even worse for me, I have a Mac and the UI is terrible. I started using Easy EDA's web sim. It's UI is way better than LT Spice, but it doesn't have a component lookup, which can be frustrating. The web interface is nice to be able to work on it at home, then on breaks at work.

+1.
I am EasyEDA user as well, I should check out their simulation function...the web interface of EasyEDA is a big plus. I never thought I would say this, but it is really very convenient to be able to access your EDA workplace anytime and anywhere. Great for a DIYer like me.

I was making progress on some sims (+6V, -6V, 100-240V Maida) but gave up after a while.

Looks interesting, I'll take a closer look at the sim function at the weekend.

 

[Delta Sigma]

The big thing I wanted the sim for was to check current. I don't want to order some transformers and find that inrush current was significant, or idle current was close to the transformer rating.