How to wind a 4000 ohm 10 watt audio transformer?

[gary350]

I know how to wind voltage and current transformers but how many turns does a audio transformer need to be 4000 ohms for a tube B+ and 8 ohms to the speaker?

Does anyone still sell these?

 

[audioguru]

Audio transformer? I think I saw and heard one 54 years ago. It blocked high and low audio frequencies and provided such poor damping of speaker resonances that the speaker sounded boomy and shrieky.
The output impedance of a modern amplifier is MUCH less than 8 ohms. It is from 0.04 ohms down to 0.004 ohms.

 

[gophert]

I know how to wind voltage and current transformers but how many turns does a audio transformer need to be 4000 ohms for a tube B+ and 8 ohms to the speaker?

Does anyone still sell these?

Look on the DIY guitar amp building sites.
Stewart Macdonald, for example.

EDIT: check, http://www.hammondmfg.com/claspg.htm

 

[Mikebits]

https://www.mouser.com/Passive-Components/Transformers-Audio-Signal/_/N-5gbg?P=1z0wnxy
**broken link removed**

For DYI: https://electronicdesign.com/power/build-your-own-transformer

 

[canadaelk]

Hammond 125xSE series. E

 

[Mikebits]

Hammond 125xSE series. E

Those are like 60 bucks at Mouser, there are some cheaper ones from different manufacturers.

 

[BobW]

<audioguru_mode>
If this is for that archaic 3 tube 50C5 single ended un-isolated death-amp from your other thread, then you'll need to find an extremely lo-fi transformer for an appropriate match. A 4000:8 ohm impedance ratio is equivalent to a 22:1 turns ratio. A commonly available 120 volt to 5 volt power transformer will give you that. Unfortunately, it won't have an air gap in the core, so it will saturate, making for bad low frequency response, and you won't be able to fully experience the loud 60Hz hum that this amplifier would otherwise be capable of delivering. Another option, though a bit more work: You could fabricate a core with some scrap iron, and then use some iron picture hanging wire to wind a custom transformer. Picture hanging wire doesn't usually come with insulation, but I don't see this as a problem.
</audioguru_mode>

 

[gophert]

Those are like 60 bucks at Mouser, there are some cheaper ones from different manufacturers.

If he is after "tube quality sound", then I cannot imagine that price is a concern.

 

[canadaelk]

I belong to the local antique radio club, lots of old transformers to be had. There must be one (a club) in San Diego you can join!
If it is the circuit mentioned in post 7, be careful! That thing has no AC line isolation! E

 

[gophert]

I belong to the local antique radio club, lots of old transformers to be had. There must be one (a club) in San Diego you can join!

That's a good way for him to get a vacation. "Wife, you stay here in Tennesee while I go to the antique radio parts swap meet in San Diego"

 

[Mikebits]

I belong to the local antique radio club, lots of old transformers to be had. There must be one (a club) in San Diego you can join!
If it is the circuit mentioned in post 7, be careful! That thing has no AC line isolation! E

I'm not looking for a transformer, Gary is...

 

[gary350]

Several people like to make fun of the old tube amps. LOL. Ha Ha.

Tube amps are highly sauté after, the Dynaco amps sell up to $1000 each on ebay. Fender and others are still very popular.

A good working tube amp has no 60 Hz hum. Laugh all you want tube amps have a much warmer sound, transistor amps have a tin bucket sound.

I don't got no getire so I don't need no fender amp no way. I aint got no good learnin but I know tubes amps smell better than transistors. LOL.

 

[audioguru]

Turn down the treble tone control on a modern amplifier and it will sound as warm as an old vacuum tubes AM radio.
Transistor and IC amps when designed properly sound like the original recording or live show. Absolutely flat and accurate frequency response and distortion much below what can be heard.

 

[gophert]

Turn down the treble tone control on a modern amplifier and it will sound as warm as an old vacuum tubes AM radio.
Transistor and IC amps when designed properly sound like the original recording or live show. Absolutely flat and accurate frequency response and distortion much below what can be heard.

AG, I don't think you understand, a guy on Audiophiles.com said "tube amps are the best and listening to amplifiers based on silicon make his ears bleed". Therefore, happiness cannot exist for this poor guy until he has an amplifier that sounds like the AM radio in your dad's first car.

 

[BobW]

Gary, sorry for my earlier comments, but the fact is that the amplifier that you discussed in your other thread is just one gawdawful circuit and will not sound good. I don't mean to put down tube amplifiers in general. I've built a few myself, and some of them sound pretty good. (In fact, as I type this, I'm listening to some internet radio played through a tube amp to my desktop speakers.) I'm just saying that there are a lot better simple tube amps than that one that you are interested in.

If you really want to build this amplifier, then take Canadaelk's advice and pick up a used transformer. There are lots of them around for little cost.
A transformer suitable for your circuit is readily available in almost every old 5 tube AC/DC radio that you'll find in a garage sale, dirt cheap.

Build the circuit, see what you think. But don't spend a lot of money on it.

And by the way, I don't know where you got the 10 watt spec from, but you don't need a 10 watt transformer for that tube.

 

[Nigel Goodwin]

Tube amps are highly sauté after, the Dynaco amps sell up to $1000 each on ebay.

Just goes to show there are a number of idiots about

 

[JimB]

Tube amps are highly sauté after

Does that mean that people jump for joy when they find one?

JimB

 

[gary350]

Gary, sorry for my earlier comments, but the fact is that the amplifier that you discussed in your other thread is just one gawdawful circuit and will not sound good. I don't mean to put down tube amplifiers in general. I've built a few myself, and some of them sound pretty good. (In fact, as I type this, I'm listening to some internet radio played through a tube amp to my desktop speakers.) I'm just saying that there are a lot better simple tube amps than that one that you are interested in.

If you really want to build this amplifier, then take Canadaelk's advice and pick up a used transformer. There are lots of them around for little cost.
A transformer suitable for your circuit is readily available in almost every old 5 tube AC/DC radio that you'll find in a garage sale, dirt cheap.

Build the circuit, see what you think. But don't spend a lot of money on it.

And by the way, I don't know where you got the 10 watt spec from, but you don't need a 10 watt transformer for that tube.

LOL........You are right that 2w amps is terrible they don't get much worse than that. I was just day dreaming about building another one for fun it will bring back good memories. I get the cart before the horse sometimes I don't need to build a bad amp project I should build something useful.

The old tube radios did make bad sound but not from the amp it was horrible from the radio signal it received and amplified.

You don't find dirt cheap tube amps anymore they are highly sauté after. I bought an old tube stereo turn table combo thing with a big 300 lb wooden cabinet for $2 at a yard sale 20 years ago you need a fork lift to move this thing. I went home to got tools then returned to remove the amp and bust the cabinet into firewood. I had the 20w push pull amp working in a very short time it sounded good with my 45 years old HiFi turn table but old vinyl is nothing but static noise but it was a FUN project. Amp was good but vinyl made noise, the sound quality is only as good as the worse item in the circuit. I had fun with the amp for several years then listed it on ebay $15 starting bid price thinking that is all it is worth and 7 days later it sold for $203. Wow I was surprised. I talked to a stereo friend Roger he said, I could have probably gotten $300 if I had listed the tube amp on the Stereo HiFi forum. Wow that's crazy.

The old Dynaco tube amp KITS were $35 in 1974 now reproduction tube amp kits sell for $980.

I am still day dreaming about building a good useful tube amp it would be FUN but not sure I really will I have no use for it. I wish I still had all my old tubes and parts a project like this would be very easy but if I have to pay $500 for parts I'm not sure I really want to build an amp. I never get board being retired I can always fine fun things to do.

 

[JimB]

they are highly sauté after.

Gary
The word you are looking for is "sought"

"highly sought after"

JimB

 

[Mikebits]

Personally I would buy the transformers just because winding over a 1000 feet of copper wire would be a pain. Just the copper wire alone would cost you a lot as well.