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Old 12th January 2012, 03:45 PM   #1
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Question New to tubes and diyaudio here, question about torrids and tube amps...

Hi,

I am new here and I am considering a few projects for this year. The CMoy headphone amp, an KT88 SE amplifier, a small chip-amp (based on the LM1875 chip) and a tube pre-amplifier (the Aikido is mentioned here there and everywhere, so that might be the way to go).

The first thing I am looking to tackle is the KT88 SE amplifier, and I have read things about power sources and regarding using toroidals (apparently not a good idea) over wound iron core transformers (a good idea).

So here is my few questions, if toroidal transformers cause something strange with the first and second harmonics (this is what I read) in the tube amplifiers, is the sound coming out those amplifiers really bad or noticeable?

With respect to solid state amplifiers a few Aikido builds (pics of Aikidos with toroidal transformers), wouldn't these have the same harmonics problems? They work great in medical equipment and big box store bought subwoofers.

Just asking because I actually have a few Chinese made toroidal transformers kicking around from a previous job given to me as samples.
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Old 12th January 2012, 04:03 PM   #2
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How is a power transformer supposed to affect the first and second harmonics of the output signal?

maybe if you were to share your source of information...

Last edited by Michael Koster; 12th January 2012 at 04:06 PM.
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Old 12th January 2012, 04:31 PM   #3
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Originally Posted by Michael Koster View Post
How is a power transformer supposed to affect the first and second harmonics of the output signal?

maybe if you were to share your source of information...
I am not sure. I thought I had read that some where (I am looking through my browser history to find the link, but it was either here or diyaudioprojects I think) and just couldn't get a my head around it, so I thought I would ask directly. I have been lurking and reading posts here and there trying to decide on the best community to join and what to build (diyaudio is the only community I joined btw).

If I can find the link, then I will post it.
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Old 12th January 2012, 04:47 PM   #4
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Originally Posted by overtheairbroadcast View Post
I am not sure. I thought I had read that some where (I am looking through my browser history to find the link, but it was either here or diyaudioprojects I think) and just couldn't get a my head around it, so I thought I would ask directly. I have been lurking and reading posts here and there trying to decide on the best community to join and what to build (diyaudio is the only community I joined btw).

If I can find the link, then I will post it.

Actually, I am sorry. I think it was a little late when I was reading about using toroidal transformers. It might have been this thread:

Toroid transformers

And I might have been mixing up "windings" with "harmonics". Sorry about that. With that in mind, I had better check to see if the transformers I have have a 6.3 volt tap otherwise, they might be boat anchors.

Again, I am sorry for my confusion (still trying to learn).
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Old 12th January 2012, 06:53 PM   #5
DF96 is offline DF96  England
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Some people use toroids for valve output transformers. I think they need better DC balance than a conventional transformer. Are you talking about output or mains transformers? I assume you are already experienced in building mains powered equipment so are fully aware of safety issues.
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Old 12th January 2012, 08:15 PM   #6
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Originally Posted by DF96 View Post
Some people use toroids for valve output transformers. I think they need better DC balance than a conventional transformer.
Agreed, DF96!

This is due to the fact that any laminated core has more or less a small air gap, while a toroid hasn't.

Best regards!
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Old 12th January 2012, 09:21 PM   #7
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Originally Posted by DF96 View Post
Some people use toroids for valve output transformers. I think they need better DC balance than a conventional transformer. Are you talking about output or mains transformers? I assume you are already experienced in building mains powered equipment so are fully aware of safety issues.
It would be the mains transformer (that would be the what I know as the power supply).

However, looking back in and considering it all, it might be better (since it is my first build) to stay with what is described in the schematics and what others have used in their projects and just stay away from the toroidal transformers for the time being. I need to do more reading on the subject to avoid the unexpected smoking amp.

The DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier based on Mikael Abdellah's KT88 SE Tube Amplifier or if I am still lacking the confidence, then the Bob Latino ST-70 (with KT88 or 6550 tubes as I have a bunch of those) are the tube amps I think I will settle on.

I will leave the toroidals for a chip amp of some sorts.
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Old 13th January 2012, 12:01 AM   #8
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Originally Posted by overtheairbroadcast View Post

The DIY Single-Ended KT88 / 6L6 / EL34 / 6CA7 Tube Amplifier based on Mikael Abdellah's KT88 SE Tube Amplifier or if I am still lacking the confidence, then the Bob Latino ST-70 (with KT88 or 6550 tubes as I have a bunch of those) are the tube amps I think I will settle on.
Two quite different amps..........What is the sensitivity of your speakers?
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Old 13th January 2012, 02:16 AM   #9
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Two quite different amps..........What is the sensitivity of your speakers?
My speakers are 93/90 dB (room rated/anechoic).

And then there are a pair of old A25 Dynacos I need to recap and put new speaker cloth on (besides having excellent reviews as a kit, this is why the Bob Latino ST-70 became desirable option).
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