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Old 5th January 2004, 01:29 PM   #11
SY is offline SY  United States
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What makes that experimentation even trickier is having to balance against the positive feedback to the driver tube.

I don't know if it's been incorporated into the Audio Anthology series yet, but I'd highly recommend an article by Norman Crowhurst, "Realistic Audio Engineering Philosophy," Audio, October 1959. He does a pretty thorough analysis of unity coupling and the driver stage tricks used by Mac.
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Old 5th January 2004, 05:43 PM   #12
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Default Yes, it is.

It's on pages 60-65 of volume 5 of the Audio Anthology.
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Old 7th January 2004, 02:45 AM   #13
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Default In the garden

Olá Pedrinho

Bem vindo ao forum da Diyaudio. Principalmente ao dos TUBES. Há poucos brasileiros aqui (acredito que nós dois).

Like you I´m just starting with tubes. Until now I am just building, mostly with schematics from Internet. Doing so to get a good amplifier to play while I am studying the theory.

I read menno´s book too. I even thought about building the Maurits, but Positron (member from this forum) recomended to find an other design. Search for maurits at this forum and you will find out why. Menno´s design with EL84´s runs the EL84´s at a higher than recomended dissipation. He says they can have it...

Have you thought about brazilian suppliers for output trafo´s? I know Lynx Audio http://www.audiolink.com.br/audiolin...formadores.htm and Tesla transformadores (excellent service). Their number is 0xx21-2233-4975 or 0xx21-2233-4050. Ask for Manoel Pereira, or his son, Roberto. I haven´t used or heard trafos from neither company, but both seem to export to Europe (to the non-brazilians guys: a brazilian product exported to Europe is really fantastic). At the moment I´m using torroidals from www.toroid.com.br as OPT.

And the tubes? Where will you get them? The guys from Rei do Som in São Paulo are asking crazy prices, I wouldn´t buy from them. Eletrônica Rei das Válvulas (in RIO) sells 6A3 (don´t know the brand) for 55 reais/each. They have got 12BH7A (ultron SQ) for 15 reais/each, 6EM7 (westinghouse) for 9 reais/each. I bought PCL86´s at 8,60 each (RSD) to buid a DPP, using the schematic of an ECC83 and EL84. Or have you already bougt excellent audio tubes from a failed company? Maybe got them from the "lixão". I think this must be possible in Brazil.

Good luck with deciding and building your amplifier(s).

Erik

P.S. 1US$ ~ 2,90 reais.
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Old 7th January 2004, 02:56 AM   #14
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Hi,

Quote:
Bem vindo ao forum da Diyaudio. Principalmente ao dos TUBES. Há poucos brasileiros aqui (acredito que nós dois).
Welcome to this DiyAudio forum. More specifically to the tube forum. There are few Brasilian people around here. Basically just you and me...

Hey...One of you should speak Dutch too, right?

That was an easy translation...I'll check the technical content later on...

Bem vinido, buen venido, willkommen, bien venue, welcome, welkom...


Just kiddin...
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Old 7th January 2004, 03:10 AM   #15
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Ik heb nederlands geleerd, aangemoedigd door mijn vader:
"Leer nederlands en je zou aangename momenten hebben wanneer je luistert naar de "plasante" uitspraak van de nederlandse taal door de vlaamse broeders".

I learned dutch because my father stated:
"Learn dutch and you will have good times listening the belgians speaking".

Geintje

Kidding too.

Erik
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Old 7th January 2004, 03:36 AM   #16
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Hi,

Quote:
Eletrônica Rei das Válvulas (in RIO)
That should be a good company to buy from in Brazil.

I recall meeting with the manager....damm I even recal what his office looked like.

King of tubes he probably wasn't, casecs regulations you know, but he seemed to know what he was doing...

Quote:
Ik heb nederlands geleerd, aangemoedigd door mijn vader:
Ah,...I had the idea it was the other way around....
Congratulations!

Cheers,
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Old 7th January 2004, 01:04 PM   #17
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Default Re: In the garden

Quote:
Originally posted by ErikdeBest
Olá Pedrinho

Bem vindo ao forum da Diyaudio. Principalmente ao dos TUBES. Há poucos brasileiros aqui (acredito que nós dois).

Like you I´m just starting with tubes. Until now I am just building, mostly with schematics from Internet. Doing so to get a good amplifier to play while I am studying the theory.

I read menno´s book too. I even thought about building the Maurits, but Positron (member from this forum) recomended to find an other design. Search for maurits at this forum and you will find out why. Menno´s design with EL84´s runs the EL84´s at a higher than recomended dissipation. He says they can have it...
It never occurred to me to build the Maurits - it seems to me
a very personal project, and according to Menno he used mainly
some spare parts he had in his workbench. It didn't particularly seduced me. I was rather thinking about Menno's barebone design (chapter 11 of Menno's book) with EL34's (30 to 100 W), or some improvement of it, such as the project of Rudy Godmaire (http://www3.sympatico.ca/r.godmaire/), because it gives some freedom of choice on the valves, and the type of feedback (if any) and phase splitting. Or this, or a McIntosh-like design, as I said in my former thread - that if I can manage to understand all aspects of such a design. I'll probably have to buy one or more volumes of the Audio Anthology, at least to be able to read Crowhurst's paper on McIntosh's unity coupled design ("Realistic Audio Engineering Philosophy"), since I couldn't find it on the Web for download.

Quote:

Have you thought about brazilian suppliers for output trafo´s? I know Lynx Audio http://www.audiolink.com.br/audiolin...formadores.htm and Tesla transformadores (excellent service). Their number is 0xx21-2233-4975 or 0xx21-2233-4050. Ask for Manoel Pereira, or his son, Roberto. I haven´t used or heard trafos from neither company, but both seem to export to Europe (to the non-brazilians guys: a brazilian product exported to Europe is really fantastic). At the moment I´m using torroidals from www.toroid.com.br as OPT.
I don't know about the other brands of toroidal transformers,
I decided to stick to Plitron because it's the only brand I have had some aural experience - an audiophile called Paulo Ramos, who lives in Santo André (Grande São Paulo) has built a VDV-like PP tube amp using Plitron and invited me and my father to have a testdrive. The result is simply exquisite.

Quote:

And the tubes? Where will you get them? The guys from Rei do Som in São Paulo are asking crazy prices, I wouldn´t buy from them. Eletrônica Rei das Válvulas (in RIO) sells 6A3 (don´t know the brand) for 55 reais/each. They have got 12BH7A (ultron SQ) for 15 reais/each, 6EM7 (westinghouse) for 9 reais/each. I bought PCL86´s at 8,60 each (RSD) to buid a DPP, using the schematic of an ECC83 and EL84. Or have you already bougt excellent audio tubes from a failed company? Maybe got them from the "lixão". I think this must be possible in Brazil.
The neighborhood of Rua Santa Ifigênia (center of São Paulo) has quite a few tube stores. My first surveys gave EL34 a price around 50 reais/each (Svetlana). Comparing with prices at, say,
http://www.thetubestore.com, ($27.95 for a matched pair, not including shipping costs), it's not that expensive. A JAN/Philips
ECC81/2/3 costs also around 50 reais/each ($12.95/each at
the site above). Scrap tubes are becoming scarce, and with brands I've never heard of - MESA Engineering, for instance.
I don't know about KT88/6550's. Real triodes are either unavailable (such as the 845) or outrageously expensive (300B) around Santa Ifigênia - certainly far beyond my present budget.

Quote:

Good luck with deciding and building your amplifier(s).

Erik

P.S. 1US$ ~ 2,90 reais.
Thanks - the same to you... I also thank the warm welcome...

Pedro

P.S.: Regarding European ascendence, my grandfather was Danish (my middlename is Lauridsen), but I can't speak a single word of Danish...
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Old 8th January 2004, 02:32 AM   #18
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Default Tubes

Hi Pedrinho

R$ 50,00 for an EL34 is a good price. Rei do Som is asking R$ 190,00 at their site.

Rei das Válvulas has ECC83 for R$ 30,00 / each.

If I remember well (one of) the phase splitters used in Menno´s amplifiers is based on a ECC82. I remember Frank de Grove stating that 9 in the 10 designs using an ECC82 in the circuit sound better when you use a 12BH7A (R$ 15,00 at R. das V.)instead of the ECC82. He can surely tell you more.

In case you find a batch of 6AS7 or 6080 for a good price, give me a hint. No, it´s not for the Maurits, but for an OTL I´m building.

Thanks.

Erik
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Old 8th January 2004, 12:15 PM   #19
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Default Re: Tubes

Hi Erik,

Quote:
Originally posted by ErikdeBest
Hi Pedrinho

R$ 50,00 for an EL34 is a good price. Rei do Som is asking R$ 190,00 at their site.

Rei das Válvulas has ECC83 for R$ 30,00 / each.

If I remember well (one of) the phase splitters used in Menno´s amplifiers is based on a ECC82. I remember Frank de Grove stating that 9 in the 10 designs using an ECC82 in the circuit sound better when you use a 12BH7A (R$ 15,00 at R. das V.)instead of the ECC82. He can surely tell you more.

In case you find a batch of 6AS7 or 6080 for a good price, give me a hint. No, it´s not for the Maurits, but for an OTL I´m building.

Thanks.

Erik
Nice price for the ECC83... What surprises me is the difference
of price between this valve and the EL34 in your case.

Regarding the ECC82, some higher power designs use the 12AX7WA instead for the phase splitting, specially when using negative feedback. I've seen the 12BH7 being used before only as a voltage amplifier stage. Anyway, this is always an optimization I can make later - I just have to see whether I'll have to change some component values in order to achieve the correct operating point in the course of substituting the valve.

As for the 6AS7, I'll probably visit the tube stores in the next days - I'll see what I can do.

Regards,


Pedro
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Old 19th May 2005, 08:53 PM   #20
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Default need powrtron schematic

Hi I saw your post on the Powrtron amp. I am interestred in this amp, but there seems to be some hard to read components on the schematic from Stan white. do you or anyone have a schematic for the Powrtron Amp which shows all the compnents clearer.

John Robey
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