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PostPosted: 12 Feb 2019, 09:19 
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Joined: 02 Mar 2009, 12:41
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Location: Vänersborg, Sweden
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I’ve never seen this design before. Does anyone know how it sounds ? It is weird that they used two separate transformers to create some kind of center tap between them. There is no phase splitter stage too. If I understand correctly, the upper transformer pair takes care of the positive phase of both left and right channels, and the lower pair reverses the positive signal to create the negative phase of both channels. Kind of like phase splitters that use interstage transformers.


I picked this design because it was simple and according to what is written on the internet, it sounds pretty good and appears to show an output power higher than it should be.

It is actually two separate SE-amplifiers, sharing one transformer. The signals to the speakers should be something like Left-Right and Right-Left.The second transformer (the lower one), however extracts the sum of of the two OP signals - Left+Right and when feeding the upper transformer with this signal, the "minus-signals" are removed, leaving a pure LEFT and a pure RIGHT signal to the speakers.

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PostPosted: 12 Feb 2019, 16:05 
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Joined: 19 Oct 2018, 15:30
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Location: Montréal, Québec
It is a really interesting design/topology. It’s a bit less powerful than what I was hoping for, but the transformers used are a lot cheaper. I’ll read a bit more about this design but I think i’ll try it !


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PostPosted: 12 Feb 2019, 16:11 
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Location: Vänersborg, Sweden
You can also use toroid mains transformers in "normal" PP amplifiers.

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PostPosted: 12 Feb 2019, 19:27 
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Joined: 06 Apr 2009, 10:08
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Location: US Pacific Northwest
Gab wrote:
My goal is to design a small power amp for the beginner who doesn’t want to spend 100$ or more for a power transformer, and at least 100-120$ for each opt. I know that some compromises will need to be made in order to achieve this goal, so I want to stick to common, cheap and easily available parts.
For output transformers, you might want to give these little units a go: Transformer - Output, 8 W, Single Ended. At $13.95 a piece they seem to fit your purposes. I have used them in the past with acceptable (if not great) results. In fact, I originally prototyped the 6CY7 amp with the little $13.95 transformer and was pleasantly surprised at the sound quality (for the price). Antique Electronic Supply has been selling these little output transformers for years as replacements for old A5 radios and the like.

You might also try the 5W Edcor GSXE: GXSE5-5K. At $20.60 they would add $13.30 to your stereo build over the other ones, but might be worth the additional cost.

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PostPosted: 12 Feb 2019, 21:35 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, The GSE trannies are seriously under rated. I get really nice response from below 30HZ to past 20K. The push-pull ones are even better.

EDIT: My personal thought is if you are going to build something to actually use it is cost effective to use good parts. If all you want to do is see if something can work as a learning experience then anything will do. :soapbox:

Good listening
Bruce

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PostPosted: 15 Feb 2019, 10:51 
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Location: Montréal, Québec
gofar99 wrote:
Hi, The GSE trannies are seriously under rated. I get really nice response from below 30HZ to past 20K. The push-pull ones are even better.

EDIT: My personal thought is if you are going to build something to actually use it is cost effective to use good parts. If all you want to do is see if something can work as a learning experience then anything will do. :soapbox:

Good listening
Bruce


It’s good to know. I will certainly be experimenting, but the goal is to end with something I’ll use and listen to. The speakers I’ll be using (still have to build the enclosures) roll of at approximately 35hz. It would be nice to have transformers that can actually go down there. I might still buy the 13$ ones for a guitar amp project.

I just saw that edcor is selling really nice "Bruce Heran" transformer kits :D


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PostPosted: 15 Feb 2019, 14:30 
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Location: Arizona, USA
Hi, I have had Edcor design a number of trannies for my projects. Eventually they are used in the kit amps as well. I like dealing with a company I can call on the phone and talk to real people. Plus the cost vs performance ratio of their products is diy friendly. There are certainly other good transformers out there, but none so far has been able to meet my needs as well.

Good listening
Bruce

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PostPosted: 17 Feb 2019, 03:05 
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Joined: 23 Feb 2017, 02:02
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There are geniune transfomers output on rs components which should come to your house for cheap, within 20usd to your house.
Never brought one but is for the tube use.


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PostPosted: 17 Feb 2019, 19:31 
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Joined: 09 Oct 2012, 19:43
Posts: 338
Location: Vancouver Canada
Hi Gab. Reading this thread I can clear up a couple things for you.
1- Bruce Heran (kit) you refer to is "gofar99" so he knows what he is talking about.

2- I live in Canada to so I know Edcor Trans are some of the best but something no one mentions is the
customs and duty cost which with shipping and exchange rates will about double the cost of any part you
see. Not a bad thing just something to be aware of.

3- You are in Montreal so in Canada Hammond Manufacturing makes trans as well and they are in Guelph, Ontario.
I am sure you have electronic supply stores where you are who could order in for you. Shipping would be about $5.00Can.
If you do this, first look at my #4 for pricing to make sure you are getting a good price.

4- Bookmark "DigiKey electronics". They are in the USA but, on their sight you can switch to Canadian Currency then every
price of every item is in Can dollars, and, that price DOES include the customs / duty fees so there will be no surprises/extras
when it gets to your door. And the prices themselves are very compatible with buying them anywhere else.
Honestly if I buy a Hammond trans from a supplier locally (Vancouver), it takes a week to come and includes $5.00 shipping fee.
If I order the same trans from Digi it costs same or less and is delivered next day with all charges done at the time of ordering
so no delivery surprises.

If you are wanting to build something that lasts the years it is worth waiting for cash to get quality parts.

I hope this helps a bit. It's useful info for your future projects to.


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PostPosted: 17 Feb 2019, 20:33 
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Joined: 23 Feb 2017, 02:02
Posts: 553
digikey typically cost me a fortune when buying outisde of usa to shipp.
rs components has free shipping even if you only buy a dollar of components.

Quality components place heavy influence in tube amps, not gonna sound good if your using cheapo transfomers and capcitors.


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