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 Post subject: A personal project
PostPosted: Mon May 22, 2017 4:33 pm 

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Here are some infos posted on the other RS forums, but I thought you would enjoy having it here too, and maybe talk and discuss about it ?
Nearly 10 years ago, I started building my first guitar amp, based on the 1W amp-Mullard schematic…some AC125, AC126, AC128s transistors, two transformers, some usual electronic parts, a good old vintage speaker, and I had my first BM-style amplifier, the perfect companion to my RS and TB to achieve the tones we all love. I couldn’t expect I would still be working on this circuit ten years later.

As you may remember, 3 years ago, I managed to find a Supersonic PR80 amplifier board, which is a key part of Brian May’s original Deacy amp. I was lucky enough not only to find an original board, but also some extra original transformers that were used on these boards.

Here is an unseen picture of my original board.
Image

Owning this original board and these transformers was of course a unique source of information that I only could have dreamt of before. All the technical details, but also aesthetical infos were there before me…still waiting to be fully discovered though. I then decided to start another “journey”, which ended a few days ago : building from scratch my best BM-style studio amplifier, using the same parts John Deacon once assembled if they were still available or building my own if they were not.

The key elements were the audio transformers…which I completely replicated, using an original pair of Supersonic original transformers. It was not only a technical replica, but also the original vintage look was part of the project. Having full access to the loose transformers did help a lot of course, as some unexpected details and infos could be seen and measured.
Having done this work, I thought I should go much further, and build a twin brother/sister to my original Supersonic board. I won’t bore you with all the details of my R&D work, but it took me most of my spare time during the last 3 years. I carefully replicated the electronic board, but also the speaker cabinet (thanks to a very similar cabinet I have). The speakers, another key part, have been chosen and tweaked using the original Elac speakers as a reference.
Enough talking, please find below some pictures of my work.
I hope you’ll enjoy seeing these as much as I enjoyed my “special journey”.

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Last edited by Manuel Angelini on Tue May 23, 2017 2:06 pm, edited 1 time in total.

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 Post subject: Re: A personnal project
PostPosted: Mon May 22, 2017 4:34 pm 

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And a few sound snippets…
I decided to not alter the recordings in any way : what you hear was just recorded off the amp, with no EQ, no reverb, etc.
We must remember Brian used many different methods to create different tones. As I couldn’t find that kind of information out, I felt it best to leave the recordings "as is" so as to not disguise anything.

God Save the Queen beginning
https://soundcloud.com/smile44/gstq-raw-mix

N&M OOP
https://soundcloud.com/smile44/nm-oop

B&M Cello
https://soundcloud.com/smile44/bm-cello

B&M Clean
https://soundcloud.com/smile44/bm-clean

B&M IP Chord
https://soundcloud.com/smile44/bm-ip-chord

B&M IP High Lead
https://soundcloud.com/smile44/bm-ip-high-lead

B&M IP Low Lead
https://soundcloud.com/smile44/bm-ip-low-lead

B&M IP
https://soundcloud.com/smile44/bm-ip


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 Post subject: Re: A personnal project
PostPosted: Mon May 22, 2017 7:37 pm 
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Thanks Manuel.

There are several members on here who will be very interested in your achievements.

Marcus Hunger in Germany is currently building a Deacy replica. Jon Griffin is interested too, maybe a few others.

Doug



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 Post subject: Re: A personnal project
PostPosted: Mon May 22, 2017 8:39 pm 

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Manuel,

I contacted you some months ago about your transformers. Your amplifier appears and sounds comparable to the original. Thank you for sharing your build. You are very fortunate to have found a radio and a spare set of transformers. They seem to be as rare as hen's teeth. Forum member Marcus Unger actually completed his amplifier a few months ago. His circuit board is not a direct duplicate like yours is but, like your amplifier, it sounds very much like the original. My projects are all on hiatus right now while i am studying for CCNA certification, but you can look at my Deacy thread here.

viewtopic.php?f=43&t=473


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 Post subject: Re: A personnal project
PostPosted: Mon May 22, 2017 9:16 pm 

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Hi Jonathan,
Yes, I remember your e-mail. I have also previously read your own thread on the subject, and you have made a good research work. Well done. These original transformers are indeed very difficult to source, almost impossible now I would say, as it seems not many of these radio sets have been kept over the years, though many were produced at the time. When you look on Ebay at all the european and american vintage radios we can source until today, you realize that keeping/collecting old stuff was not a priority in Rhodesia !
About the tone and sound, as you surely know, the amp tone in the flesh and on a recording can be very different, and you can more or less match a recording while sounding rather different in a AB test. The thing is I think one can achieve a similar tone using vintage transformers of that era (not all of them would do the trick though !), but then you also have to mtach the speakers, and that's another story !
If i were you, I would indeed (as you started doing) test a few original transformers pairs found on Ebay with vintage speakers of that era. You would be period correct, and maybe easily close in tone.


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 Post subject: Re: A personnal project
PostPosted: Mon May 22, 2017 11:04 pm 
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Manuel
I read your project on another forum Facebook group page, so happy to see you have posted it with us too!
Projects like this make me smile as it's so great to see that hard work and research is still alive.

My congratulations to you on what you have achieved, it's quite amazing.

If I maybe bold enough to ask, we are always on the lookout for amazing projects to put on our website, would you consider allowing us to share your project on the website too? In a PDF format or something?

Once again my congratulations on your achievement and what you have built, I am sure many will be interested.


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 Post subject: Re: A personnal project
PostPosted: Tue May 23, 2017 12:46 am 

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Manuel Angelini wrote:
These original transformers are indeed very difficult to source, almost impossible now I would say, as it seems not many of these radio sets have been kept over the years, though many were produced at the time. When you look on Ebay at all the european and american vintage radios we can source until today, you realize that keeping/collecting old stuff was not a priority in Rhodesia !


I read about a phenomenon called "tin whiskers". This afflicts AF11X series transistors and causes them to have internal shorts rendering them useless. The Supersonic uses AF116 transistors in the AM and FM amplifiers. I would bet that most of these radios, (with their perfectly good amplifier boards!), ended up in landfills because they stopped working after a transistor short. From the start, these radios were probably less common than something like a Hacker. When you combine the two factors, the result is precious few PR80's trading hands in the 21 century.


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 Post subject: Re: A personnal project
PostPosted: Tue May 23, 2017 1:36 am 
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A couple of comments:

For those that are benefitting from his painstaking research and development work, knowledge and information, please thank Manuel by hitting the thanks button! :D

Secondly, I bought a bag of components from Nigel Knight last year. In it are a quantity of germanium semiconductors of various gains which Nigel has measured and marked on the body.

These are no particular use to me (I only bought the stuff out of interest and because I thought it might come in handy in the future). I have an official KAT Deacy replica amp and have no desire to make my own although I am very interested in electronics projects from an academic perspective. If anybody wants them, I am prepared to sell small quantities for personal Deacy replica and treble booster build projects so PM me if you're interested.

There are plenty of AC128 transistors but only a very small number of AC125 transistors.

Doug



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 Post subject: Re: A personnal project
PostPosted: Tue May 23, 2017 10:02 am 

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Admin wrote:
Manuel
I read your project on another forum Facebook group page, so happy to see you have posted it with us too!
Projects like this make me smile as it's so great to see that hard work and research is still alive.

My congratulations to you on what you have achieved, it's quite amazing.

If I maybe bold enough to ask, we are always on the lookout for amazing projects to put on our website, would you consider allowing us to share your project on the website too? In a PDF format or something?

Once again my congratulations on your achievement and what you have built, I am sure many will be interested.

Thanks again for the very kind words ! Yes, sharing the project on your website would be a very good idea. I may come up with a pdf, as suggested, that you could use for that matter. I may take a little time to make it, but that will definitely be on my list.


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 Post subject: Re: A personnal project
PostPosted: Tue May 23, 2017 10:17 am 

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Jonathan Griffin wrote:
Manuel Angelini wrote:
These original transformers are indeed very difficult to source, almost impossible now I would say, as it seems not many of these radio sets have been kept over the years, though many were produced at the time. When you look on Ebay at all the european and american vintage radios we can source until today, you realize that keeping/collecting old stuff was not a priority in Rhodesia !


I read about a phenomenon called "tin whiskers". This afflicts AF11X series transistors and causes them to have internal shorts rendering them useless. The Supersonic uses AF116 transistors in the AM and FM amplifiers. I would bet that most of these radios, (with their perfectly good amplifier boards!), ended up in landfills because they stopped working after a transistor short. From the start, these radios were probably less common than something like a Hacker. When you combine the two factors, the result is precious few PR80's trading hands in the 21 century.


Well, the AF116 and AF117 were commonly used at the time, and were afflicted with the tin whiskers issue you described. All the brands used these transistors, and i guess all of them had this same issue. The replacement is not a simple "drop-in" job, but we have to keep in mind that radios were not cheap at all then, and those were the times when you mended things, instead of throwing them away, because it was economicaly worthwhile to do so. No wonder why we can still find all these vintage service manuals nowadays : they were very useful !
About the number of sets.... Supersonic was really big in the 1960s, and produced between 400 and 800 sets a day, comprising of around 14 different models. 2000 workers were employed by Supersonic in the mid 1970s... So don't think that was a short-lived manufacturer, but they litterally produced tens of thousands of each model.That's why their rarity today is rather surprising to me.


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