Simple valve amp

[GlowBlue]

Hi guys

It was a while i was active on this and other forums.Had to cool down in my enthausiasm building a tube amp.Still have that ambition but first things first.
I bought a small amp, https://www.radiomuseum.org/r/unknow...plifier_s.html from my local marketplace but it has only 3 tubes instead of 4. I did not ask the seller but does it miss the phono?
And can i get help to restore this thing and upgrade it to the best possible?
Tomorrow when my money is in i can pay the €28 shipping included and think i have it in the day after. This hobby makes me broke But i don't care.I am talking to people who can make a chassis out of nature stone
Is anyone or more interrested to guide me to rebuild this simple amp?And what you think in general of this small amp and the possabilaties of it turning it into a good sounding amp?

Leon

[Megatron]

I think its probably 2 watts, and has very small output transformers.
the sonic abilities will be somewhat limited, that said a good starter project.

I would be suspicious about input voltage. the one you send the link to says 220v, its made in japan. Japan use 220v 60 & 50Hz mainly, I dont know what your mains voltage is there but you may find its a bit on the high side?
I have seen japanese stuff before that seems to be designed for 220max,
208 gets all the voltages right..........when you plug in to typical UK voltage things go pop!. I have seen 260V here on occasions though usually its nearer 250.

HL94 output valves dont seem to be very common either... 2 watts output at 11% distortion.......

[GlowBlue]

Hi Megatron. That's what the seller said,it is not even 2 watt.But i buy it from the Netherlands with the same voltage so i assume it is ok.But we will check that first before plug in.It was build for a Dutch brand Hapé so i think that part is fine.But never check enough

I think also this can be a good starter project before i dive into the deep trying to build a tube amplifier from scratch.I have to be patient and start from where you guys started.

Internet makes it look more easy but it isn't.You guys learned it without the distortions of the internet.You learned it step by step and on the road you understand things as they are.For me now in this era it is much harder to pick a point to start.All the information is confusing me.Mr a says B and Mr b says A.

Thats why i start with a simple amplifier and i hope i can learn from you

[Diabolical Artificer]

Agree, a good amp to start with, but is there a schematic out there for it? If not this makes things a lot harder.

Andy.

[peter_sol]

I doubt there will be anything wrong with that amp.
What are the positions on the selector switch? and what valves does it use.
Yes it may not have Magnetic cartridge inputs but that expensive amp you were thinking of building may not sound much better.

Good luck with it.

[Herald1360]

Originally Posted by Megatron

I would be suspicious about input voltage. the one you send the link to says 220v, its made in japan. Japan use 220v 60 & 50Hz mainly, I dont know what your mains voltage is there but you may find its a bit on the high side?
I have seen japanese stuff before that seems to be designed for 220max,
208 gets all the voltages right.............

Japanese domestic voltage is 100V 50 or 60Hz in different areas.

Usual three phase supply is 200V l-l open delta with ground half way between two of the lines giving the option of 100V or 200V as single phase supplies and 200V l-l three phase.

Yes, it is odd!

Back at the amplifier- it looks like there's a mains transformer and solid state rectification. It'll be interesting to find out exactly what they did for heater and HT supplies.

[Sideband]

The 30A5 output valve according to the National Valve Museum is capable of 2.1 watts at around 11% distortion so very far from Hi Fi. The other two valves are 12AX7 or ECC83. Presumably the heaters are in a 150mA series chain and fed from an 84 volt supply or thereabouts. I doubt the HT is more than 150V since the 30A5 is designed for low HT applications.

[Radio Wrangler]

Leon, you sound very very enthusiastic, but it sounds like your drive to get a valve amplifier - any valve amplifier is driving you to your financial limits. Please don't hurt yourself.

The audio world is saturated with myths and legends. There is an amount of truth in some of them, there is no truth in many, and plenty will actually make things worse.

A natural stone chassis, for example, sounds nice in words. Once made it could look wonderful. But amplifiers don't work by their looks, they don't work mechanically. They work electrically. Electricity and electrical properties are largely invisible. What may or may not look right if you looked at it as a mechanical machine can be totally misleading. Electrical signals move at approaching 300,000 kilometres/second, sound waves move at about 330 metres/second. The difference is astounding.

The chassis of an amplifier does two things. It holds things in the places you want them and it provides a really good common connection point.

Stone isn't any good as an electrical conductor, and adding wiring to substitute for chassis connections is not as good as a metal plate.

Great rigidity isn't needed. You can shake electronic stuff around and the effects are difficult to determine. As part of my job I shake aircraft radios with levels of vibration representing accelerated life and also the levels of vibration measured in damaged helicopters. The aim is to see if electronics work properly and whether things start to fall apart. Any effect on the signals is a sure sign of a design error.

So all the heavy stone, spiked feet and such things for amplifiers are a joke to people who do serious electronics design. A plain old metal chassis is close to ideal. Any fancy bits serve as nothing more than decoration.

Back in the sixties, the first transistor amplifiers came out. People hadn't learned how to design around the new device's characteristics, and the results were very poor. It was a big step back in audio quality. Overly simplistic measurement techniques and a lack of understanding failed to show up the problem. Out of this grew the beliefs that any valve amplifier has to be better than any transistor amplifier, and that measurement results were meaningless.

Well, some progress was made, and from the middle seventies onwards, some very good transistor amplifiers have been designed and measurement techniques evolved to be able to see the problems of the sixties and people learned how to not make such mistakes.

Unfortunately these beliefs still continue. They've entered folklore and have been repeated so many times that they must be true.

In practice, it means that valve amplifiers and their key components are heavily sought after and their prices are pushed unnaturally high. It also means that the results are not wonderfully better than transistor amplifiers.

Simple valve amps distort audio signals, but the nature of the distortion is liked by many people. It's usually described as a warm sound. Back in the fifties and sixties, the rather cheap and crude valve amplifiers in small record players and tape recorders gave quite a lot of it, but people aspired to getting valve amplifiers by Leak, Quad and Radford which gave a lot less of it. Back in those days, people knew how to listen and they voted with their money.

So take care. Beware of all the stuff on the internet and magazines trying to lure you into buying their latest product, beware of consumers trying to persuade you into buying the same types they have (It makes their gregarious instinct feel good and it makes doubtful purchases feel less foolish)

There is much smoke, mirrors, psychology and misinformation.

Good science and good engineering form a reliable and impartial bedrock.

David

[snowman_al]

Everyone,
I think Leon has asked us to keep everything simple for him.
Quote, ''All the information is confusing me. Mr a says B and Mr b says A.
That's why i start with a simple amplifier and i hope i can learn from you''.

The Radio Museum amplifier and pictures are Not correct to the product. It should only have 3 valves, 12AX7, 30A5 and 30A5. (The horizontal one near the input sockets is a modification.) There are pictures and more information here: https://forum.audiofreaks.nl/index.php?topic=39941.0 in Dutch even! You can see the transformer is marked 220 volts in and 72 and 120 volts out as well.

Leon,
Did the seller say it was working? If not best post some pictures of your amplifier when you get it and before you plug it in. We can advise you better then. Alan

I think it is well worth getting going and using, 1 watt is more than enough to annoy the neighbours and at 1 watt it will have much lower distortion than 11%. Nice bog standard economy valve amplifier.

[usradcoll1]

Many of the portable stereo phonos sold in the US had amplifiers similar to the one shown. Some had only two output valves and were driven by a high output pickup cartridge, ceramic type.
I only ran into only one radio that used a 30A5 output valve, not a common one here.
The small amp shown is a little better, it uses a mains transformer with a tap for the heater chain, instead of a large dropper resistor.
We had the same kind of Japanese Amplifier sold here, but without the mains transformer, using isolating capacitors between the chassis the metal enclosure. Naturally, I had one many years ago.
Dave.

[peter_sol]

It will no doubt have some negative feedback to minimise the distortion. so try it you may be pleased.

[usradcoll1]

The one shown, must've been more expensive than the ones for the US market. Good sized mains transformer and the output transformers are a little larger than the one sold here.
The early Japanese equipment was not U/L or other inspection agency approved.

[GlowBlue]

Time flies Again it is to days ago before i react on this thread.I have no email notification.I was wandering on the net past days but today i got the amp and at first i was very dissapointed but now i'm more enthousiastic then ever.David,thanks for your words.I know it is not the way to use stone.I understand what you say.For me it is far away to do that kind of things but it is part of the freedom to do what you want if you are into DIY.I dislike the looks of 90% of the tube amplifiers.In my mind a tube amplifier is for life sinse you can repair and tweak it all along.So why not make it with that in mind?Take care of the looks and feelings also.For now that's not the point and i have to concentrate on the amp itself.

I learned a lot today.It is all on the right speakers i learned.This simple amp was very dissapointing at first but now it is my most loved thing.The sound is amazing for what is is after playing all day with speakers and my whole arsenal of vintage gear.If i had to do this with more expensive things i was broke at the first minute.Now i can use all my gear to combine,compare,test and get used.With my original plan i had to build a tube amplifier from scratch i would have walked into walls.Now i know 2 times 1 watt is enough to provide in my daily needs.10 watts will be much in my living room.So to step up the tube ladder with a spartan amp like this i think i am on the good way.

It is late now and i will go deeper into all the replies later.Thanks for that.It is part of my enthousiasm people try to help and give advice.I priciate that.It's what my life is based on

Not sure if it is ok to link to another forum.If not remove the link.Here is a thread on the amplifier and my findings so far. https://www.diyaudio.com/forums/tube...ves-types.html I came there searching things and my simple question went bigger.

Hope you understand all the information on internet is bigger then a libary to learn things.And now in the libary you have at least 4 people telling you things all another way.There is no 1 learning master but many people with many visions.Hard to find the right path.On the other side it pushes me to think,so i see it as possitive.

Later on i go deeper into the posts where needed but for now i need some sleep. Thanks for all the kind and helpfull replies. Leon.

[Diabolical Artificer]

"you have at least 4 people telling you things all another way. There is no 1 learning master but many people with many visions. Hard to find the right path."

People can only guide you, most info folk give you will be meaningless and confusing as you have little or no base knowledge or more importantly, experience, to start with.

Electronic engineering is a complex subject, audio amplification which is a very minor part of EE is also beset by sincerely held misconceptions, rumour, myth, black magic and downright dishonesty. If you want to know the truth, find out for yourself, forget what people say, or at least treat what folk say with suspicion and go and learn practical electronics bearing in mind some people will still try to bamboozle you and get things wrong.

Therefore get yours hands dirty, get an old tranny amplifier that doesn't work and try and fix it, or build a simple power supply, you'll struggle at first and make lots of mistakes, (this is good) but you'll pick it up eventually and have experience that will guide you through the maze that is audio hifi.

Andy.

[Heatercathodeshort]

It will probably sound a lot better than the specification may suggest. It will be designed for a ceramic or crystal pick-up. A low noise pre amp will be required for a low output magnetic type and quite frankly I doubt if it is worth the added expense. Good luck with it and I bet it works OK. John.

[GlowBlue]

Andy,i do get my hands dirty Took it apart and looked at it.All the wiring is gone.When i bend it a few times it all break.Think i have to rebuild it fully.
When i connect it (my way) to my Denon PRA 1500 pre-amp and send it to my cheap Nobsound pre-tube amplifier and also to my Philips Mfb speakers with an old 80's equalizer between i can get a very promising tube sound in general.Using this thing not in power but somewhere in the line makes the end of the line very nice to listen to.Not the ideal thing but it proves me sound is not numbers.It took me 2 days to tweak with all my gear from the outside and i learned not everything is what it seems Not one thing is good and another thing not.I have piles of old stuff and the key is in combining things.I found a combination in transistor things where this bad tube amp found it's place to create a good sound in my ears.

That's what i want to do with smaller parts.Tweak untill even this small amp can sound good (in my ears) Now i did it externally with my pile of gear but i think it's the same on a smaller scale changing internal parts in an amplifier.

John,the sound is now very good in a line of 5 other things.Giving that little distortion to that line is amazing.Never got that kind of sound out of my motional feedback speakers.Not the full thing but just a little touch of the tube amp inserted into the line.Just that small bit works It brings the total more real and it does not sound worse.
Hard to explain but this total setup does not suffer from the bad tube amp.The bad tube amp add a certain thing to the setup what is good.Everything is more "there" now.If i disconnect the tube amp what i simply can do,everything is gone.Sounds good but that "thing,warm sound" is gone in dust.Amazing how the singers and instruments went back into the speakers by disconnecting that small thing.It costs me a long time to set up.It might not be the best thing to start with also.But now i know what tubes/valves are.Even if it is bad,they are 3D.That's what it does.If i turn off that small amp the ghost is no longer circling trough the room but goes back into the speaker.
For me i am addicted to tubes and i will never get the ghost back into the bottle because i don't want him Only that small influence in the transistor line can do great things.Sorry for the long story
I'm happy and up to things...

Leon

[GlowBlue]

Had this song playing at full power earlier https://www.youtube.com/watch?v=FAvQSkK8Z8U It still is here! I mean all my neightbours were gone and i could do it.Now 3 hours later i am still into that.Never experienced that before.It's 3D,not surround.I'm not good at explaining things but hope you understand it a bit.That song is still going on in my brain

Not relevant but can't help to post it
https://www.youtube.com/watch?v=fRt8CoZT35k
https://www.youtube.com/watch?v=rbmJ...ZT35k&index=12 !!!!!!!!!