An idea for ripple smoothing in 310V PSU

Admin wrote:... Din't like the subject matter they gave to practice; "Drink to me only with thyn eyes [yawn]). Kinda put me off. ...

I thought about the Tyros 5 but the price and I already have so much stuff in such a small space, made it impractical. ...

Hi Harry,
they gave you quite nice songs to practice. I had to play special etudas, one edition to train the left hand and the other one for the right hand. They were written solely for education purposes, it was no pleasure even to listen to them.

IMHO the Tyros line is obsolete now, it has been replaced with Genos. Tyros might be found for reduced price somewhere. Well, the space is always the problem.

VBRfrom Ivan

Hi Ivan,
Yes, just like a real-live conversation, the subject matter can slide a little.

But for me it is still relevant to the tube AF amplifier, that needs transformer winding.
I hope to get the transformer finished this weekend, then I will start on the choke and speaker transformer final versions (with 3D printed instead of cardboard formers).

But as regards music, I took piano lessons as a kid. Din't like the subject matter they gave to practice; "Drink to me only with thyn eyes [yawn]). Kinda put me off.
Took it up again with the accordion.

I thought about the Tyros 5 but the price and I already have so much stuff in such a small space, made it impractical. I really need to concentrate on one project at a time ;-)

Very best regards from Harry - SM0VPO

Hi Harry,
it really looks like we have moved somewhere else from DC ripple removal  

I played a violin for 11 years as a kid/student. I did quite a progress. The problem with violin is the player must practice every day. After I realized I could earn my money as a teacher of violin or as the 4th violinist in the 2nd violin group in a municipal orchestra, I stopped this activity. Since than I read notes in violin clef fluently, but I have huge problems with those in bass clef.

When electronic keyboards became available for a reasonable price, I tried it and found it was the right instrument for me - just for fun. I have never performed in public. I gradually improved my hardware. Now I have Yamaha arranger workstation. It has the same synthetiser as Tyros 5, but includes built-in amplifiers and loudspeakers. I switch it to one finger mode rather than the fingered one. I played famous polkas, waltzes and similar melodies. Unfortunately my curved fingers stopped me for now.

VBR from Ivan

Hi Ivan,

I was offered a genuine120-bass  Honer accordion in the 80's, just before I left the UK for good.
The guy wanted £500 for it but I only had £350. He went away.

A week later he came back and said he would take the £350. I didn't really want the instrument, so I said I have done some spending and only have £250 left. I thought he would go away, but he took the money and I got an accordion. It was not a lie, that was all that I had. I should have said I didn't want it. 

I locked myself in the workshop until I had mastered one piece. I should have chosen a nice simple Beatles piece, like "Yesterday". I chose The Anniversary Song ( https://www.youtube.com/watch?v=v_SnrF2bzDw ), no less than 7 different chords. It took me about 5 hours.

I have been playing on and off since then, but had to stop in 2014 because the instrument was in Spain and I was in Sweden. When I was in Spain I was always repairing and fixing, so there was little time for anything else.

But in 2002 I got a copy of Cubase (I think that was the name) where I could open and edit MIDI files. I could mute the lead instrument and use it as a backing for me on the accordion. About 2007 (not 100% sure of the year) I got Propellerhead Reason synthesizer for the PC. There I could create orchestral backings for me on the accordion. They even had male and female vocals, as well as being able to use sound files in the sampler.

Yes, I love the accordion, and I am really glad I got the 120 bass instrument with the counter-base keys. One of my party tricks was to play it upside down.
I was once asked to play in a small comedy club in Stockholm. I entertained for about 30 minutes. The owners said I was well liked and they wanted me to perform regularly, but to be honest I was nervous. Most of the session was a stand-up comedy session where I made fun of the English in Sweden, who are bad at Swedish.

If you can speak 3 or more languages you are a "polyglot"
If you only speak two languages you are called "bi-lingual"
If you can only speak one language then you are "English"

I think you get the idea how it went. I remember I had to stop a few times until people stopped laughing enough for me to continue.

Today I still use the keyboard from time to time, but not so much on the squeeze-box: the "moobs" can occasionally get trapped in the bellows . I can read music (had piano lessons as a kid).

Sorry Ivan, I did ramble on a bit. But please tell me about you? Reading between the lines I think that maybe you have some experience on the keyboard?

BR Harry - SM0VPO

Hi all,
an accordion is wonderful. A keyboard with one finger accompaniment is even better - the player does not have to push and pull the bellows.
I perhaps learned one Swedish word, too: föda should mean food. There is a shop with Swedish specialities in Prague named by this word. Now they seem to have problems with supplies due to covid,
Who eats much föda, becomes a tjockis??

Enjoy the life!
BR from Ivan

Hi Glenn,

You may not believe it but I have really been on stage, a long, long time ago.
I played the piano-accordion, between two sessions of jokes. When I say jokes, it is a short life story with some of the things I did wrong since I came to Sweden.

A couple of friends helped me to learn Swedish, they taught me:
Yes = Ja
No = Nej
Hello by friend = Hejsan tjockis (which really means "hello fat-man")

Every week I went to the radio club they all greeted me with a warm "hejsan tjockis", and we all had a good laugh.

A few weeks later I had an interview for a job and tried to impress the interviewer with some Swedish. I must be the only person in Sweden who went for an interview, called the interviewer a "fat man", AND got the job!

The accordion is a wonderful instrument. I played "Hava Nagila". Had a lot of fun. I was invited back tot he club a couple of times, but it is not really my "thing".

BR Harry - SM0VPO

Harry and his famous guitar amplifier!
I imagine seeing you on stage playing hardrock and heavy metal...
Only the thought makes me laugh!
[/joke]

John_1981 wrote:Agreed about a proper iron core transformer being more authentic, but if you are in a situation where either you don't have a suitable transformer or need an unusual voltage for say a PLxxx valve, its a simple matter to make something like this from the junk box.

I published a video many years ago on youtube "emergency power" without soldering. That used a multi-vibrator with just 2 power transistors and a transformer (plus the battery out of the wife's car). This is one of the reasons I love wound transformers. You can get any voltage you like, and there is no RF radiation from them. So easy to make or re-wind.

John_1981 wrote:Harry, could I please have access to post photos?

Hi John,
Yes I can do that but you need to have a username and password to which I can give the access. The forum admin will not allow me to give permissions to one guest without giving it to all guests.

Very best regards from Harry - SM0VPO

Agreed about a proper iron core transformer being more authentic, but if you are in a situation where either you don't have a suitable transformer or need an unusual voltage for say a PLxxx valve, its a simple matter to make something like this from the junk box. The ready made power supplies from China are cheap, but if you make it yourself you will understand how it works and how to modify and repair it as required. And there won't be any SMD components in it...

By the way, the main power transformer can be wound on the core salvaged from an old CRT TV flyback transformer provided that the two spacers to provide the air gap are removed. 

Harry, could I please have access to post photos?

Hi John, wrote:I remember seeing a circuit diagram where a 6.3Vac heater winding was centre tapped to chassis via a pot and it was described as a 'humdinger', memorable because i was amused by the name. 

It was common in those days. It reduced the hum induced from the AC voltage on the filament into the electron system. It was not a common pot, special wirewound resistors with a movable tap were used. They had quite low resistance and they were rated for cca 5 - 10W.
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I do think that now it makes more sense to derive HT supplies from something like a self oscillating half bridge SMPS rather than heavy iron and copper,

Yes, SPSUs are smaller, lightweight and easier to be made, but they are not the proper oldtimers! Perhaps it is even better to buy a whole supply instead o making it. Some time ago I posted this link in another thread here. IMHO it is worth its price (cca 25USD).
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I intended to post the circuit on this forum but never got around to it.....

Ask Harry to add you to members of the forum. You will be able to post links and host pictures after that.

BR from Ivan

I remember seeing a circuit diagram where a 6.3Vac heater winding was centre tapped to chassis via a pot and it was described as a 'humdinger', memorable because i was amused by the name. 

I do think that now it makes more sense to derive HT supplies from something like a self oscillating half bridge SMPS rather than heavy iron and copper, I knocked one together a few years back to provide 40V for some PL509 valve heaters. The parts are all available in the junk box and the transformers are easy to wind since they have few turns compared to 50Hz. 

Take a look at DL2YEO's (sorry it wont let me post the link) 'power supply for small tube amplifiers'. I built a power supply very similar to this but replaced the "start up circuit" with a 470K resistor between B and C of each switching transistor. The base drive transformer came from a dead CCFL lamp and the switching transistors were horizontal output transistors from scrap CRT TVs. I could power a 150W incandescent bulb without any heatsink at all. The important thing is that the drive transformer saturates long before the main power transformer or the smoke escapes explosively. The main power transformer can initially be replaced with an incandescent bulb to check the phasing of the drive transformer, etc. 

A series light bulb to limit current is a must until you get the circuit working properly of course. 

I intended to post the circuit on this forum but never got around to it.....

Hi Harry,
thank you for your kind words. My experience with electron tubes is almost null, I still have to learn much. Germanium transistors were dominant in the time of my studies. Re using G2 in an audio PA - I am sure that G2 connected to a tap of the primary has been used in commercial radios quite often. They were A class stages with one pentode.
I did not know you play a keyboard. I tried to play one as well, just for fun. I have Yamaha with built-in amplifer and loudspeakers, no external audio required, always ready for use. Unfortunately my fingers got crippled some years ago (even before my backbone did) and my Yamaha just collects dust now. The doctor said the nervature in my hands is damaged. I am attempting to cure it and I hope I will be able to play again.
The weather in Sweden corresponds with the common image now - frost and lots of snow. We in OK have temperature around 0°C, rain and some snow even in lowlands. Winter is no good for outdoor projects!

Enjoy the weekend!
VBR from Ivan

Hi Ivan,
I thought it is so obvious that it MUST have been done before. But you never know these days. I find that many new designs are based on old conventional designs, and modern engineers are not so inventive with components, but a LOT more inventive with IC's.



I really appreciate the link. I particularly like this diagram. The voltages are different, but it is the configuration I am interested in. 

With my drawing I just needed a token pre-smoothing, but the cancellation and a large cap at the output I think will save a lot of time and money. I would still need the large at the output since the 100Hz is not exactly sinusoidal, but inverting and cancelling will modify the waveform to give the noise at a composite waveform of 200Hz. By the way, The 47uf cap has a Z of 3.5 Ohms, not 7, at 100Hz. At 200Hz it will be more like 1.8 Ohms.

My 6 year old amplifier was inspired by the Marshall 45-Watt amplifier, but 12.6W is more than enough for my keyboard. In addition, my synth gives out 500mV so that amplifier should handle it without any problems. If I need more gain then V2 has a spare (unused) triode.



I also thought about the screen grid of the EL84. It is normally decoupled and fed with a resistor. Decoupled because it behaves as a second (low power) anode. I thought, why not use that available power. G2 will also have 310V DC plus the audio, so it will accelerate electrons more readily at higher voltage peaks. I remember that power pentodes tend to "sag" a little when they are run close to their limits.

Incidentally, this project and the whole article is not about the audio amplifier; it is about the inductors. T1, T2 and L1, together with simplified calculations and on-line calculators to give the turns per volt, core size, etc. This is based on 40+ years of experience winding and rewinding transformers.  As soon as it is ready for publication I will ask you to review it, if that is ok with you. At the moment I cannot get to the antenna to trim and finalize it: we are expecting -18'C tomorrow, so it is getting less and less possible.

Ok, catch you later Ivan. Thank you once more for your comments. I really appreciate them. Discussion is always a good way of sharing knowledge. I have learned a lot from you, and got a lot of "idea sparks" over the past couple of decades.

Hope you have a nice weekend. BR from Harry - SM0VPO

Hi Harry,
what an innovative idea! I cannot imagine whether it will work or not. You are right, the filter chokes are heavy, expensive and hard to find nowadays. Making one requires VERY many turns of thin wire. The choke may be replaced by a power resistor for small loads, but it wastes energy and heats the device compartment.
The only article about using two chokes on a common core I have found is this one.
One more recommendation is to keep the first capacitor (at the rectifier) not very big. It should help to avoid hum caused by its charging current.

VBR from Ivan

Hi guys,
Here is a question for you all.

I am resurrecting an old project that I never had the chance to even start, other than the drawings in my lab book. As usually I get the odd idea and this is no exception, so I wonder if any of you have seen anything like this technique before?

This is the 310V DC PSU for a valve (tube) based guitar amplifier. Only 12.6 Watts, but the supply current at 310V can peak around 90mA (absolute max). To keep it silent I may have to use 6.3V DC, but I will give it a try with AC in "common-mode".

The HT side will need some hefty smoothing to keep it silent at low signal levels, and 450V capacitors at 470uf are not cheap. A 5 Henry inductor is also expensive and heavy, unless I make it myself, but then that eats a LOT of time. So how about using a 12-0-12V winding of a small 500mA transformer?


The thought is that assuming 10V of ripple directly after the rectifier (100Hz) I can ground the centre-tapping set to only 5V of ripple. The other half of the 12V winding will act as an auto-transformer and inject -5V of ripple to cancel out the +5V of ripple. The idea is that the 100R resistor can be adjusted to notch out the supply ripple at low signal levels.

The transformer is a miniature, 260g unit at US$2.5. The only think I would have to do is the re-assemble the core laminations with all E's at one side, all the I's at the other, and 0.1mm of paper between them to break the magnetic flux, to prevent the DC from saturating the core.

If this works then it can save money on components, save a lot of weight on the amplifier chassis, and also make it quicker for me to build.

So what do you guys reckon?

Best regards - Harry - SM0VPO