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 Post subject: Sub-miniature guitar tube amp
PostPosted: Mon Jun 20, 2011 3:40 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
A new demand exists, on low power tube amps for practice and recording. Digital simulators are nice, and contain lots of presets for famous guitar amplifiers, but reality is always much more real than any model.

I am going to start from a simple experiment: to reproduce sound of a small venerable Fender Champ 5F1 amp using sub-miniature vacuum tubes available from Russia (Soviet military stocks).


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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jun 21, 2011 8:00 am 
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looks really interesting... will it be basic amp or with tone controls and distortion controls too?


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jun 21, 2011 10:21 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
This one will be exactly like Fender Champ Amp, with no tone controls.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jun 21, 2011 11:38 am 
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I was thinking along the lines with 6N2P and 6P1P. What do you think about these tubes for a guitar amp? I don't think they will sound like a Champ though...


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jun 21, 2011 3:19 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
I was thinking along the lines with 6N2P and 6P1P. What do you think about these tubes for a guitar amp? I don't think they will sound like a Champ though...


Why not?

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jun 21, 2011 6:24 pm 
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Posts: 238
wavebourn wrote:
quikie22 wrote:
I was thinking along the lines with 6N2P and 6P1P. What do you think about these tubes for a guitar amp? I don't think they will sound like a Champ though...


Why not?


Slightly different curves I guess? Different tubes?

But I am thinking of making one although I don't have a guitar Wink Will make it and maybe give it to my friend as a birthday gift.


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sat Jun 25, 2011 8:29 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
Here is my current schematic:


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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sat Jun 25, 2011 9:31 am 
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Joined: Mon Mar 22, 2010 1:10 am
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Nice job but a few silly questions from a newbie...

The output tube is at a lower voltage than the drivers... So that it has a lower headroom and distorts earlier?
What about the diode-R from the higher B+ to the anode, what is it for?

Why do we still use GNFB feedback?


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sat Jun 25, 2011 9:38 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
Yes, most of distortions come from output stage. Diode is for lowering of G2 voltage and preamp B+ for "sagging", i.e. kind of non-linear compression.

Feedback was used by Fender in the original amp, I will try both with it and without. I suspect it increases difference between loud and soft sounds.

Actually, preamp and G2 are not powered by too high voltage: see R4 that is 56K. Currently it is like 200V, when anode voltage is 160V. When I connect preamp stages it will be even lower. The trick is, it depends on sound loudness.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sat Jun 25, 2011 11:15 am 
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Joined: Wed Oct 01, 2008 7:13 am
Posts: 54
Location: Russia
quikie22 wrote:
I was thinking along the lines with 6N2P and 6P1P. What do you think about these tubes for a guitar amp? I don't think they will sound like a Champ though...

Будут звучать нормально. Главное, для 6П1П не превышать напряжение экранной сетки в +300 В.
Я снял ВАХ разных ламп для включения по схеме Fender Champ:
http://valvelab.pochta.ru/fc.htm
Остаётся рассчитать Ra и выходной трансформатор.
Анатолий, получилось неплохая схема. Очень интересует звучание с цепью диод - резистор между экранной сеткой и анодом и без неё. В чём отличие на слух?

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sat Jun 25, 2011 12:27 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
AlexR wrote:
Анатолий, получилось неплохая схема. Очень интересует звучание с цепью диод - резистор между экранной сеткой и анодом и без неё. В чём отличие на слух?


Пока не пробовал. Но боюсь, что постоянная времени большеватая, может придётся уменьшать ёмкость конденсатора.

Мне сейчас привезли на ремонт совершенно идиотские моноблоки: по паре 845-х в параллель, каждая раскачивается своей 300B, нагружены на трансформаторы типа пятнадцативаттного размера. Буду занят ими.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sat Jun 25, 2011 10:02 pm 
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Joined: Wed Oct 01, 2008 7:13 am
Posts: 54
Location: Russia
wavebourn wrote:
нагружены на трансформаторы типа пятнадцативаттного размера. Буду занят ими.

Забавно. ВЧ-тракт?

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sun Jun 26, 2011 7:22 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
AlexR wrote:
wavebourn wrote:
нагружены на трансформаторы типа пятнадцативаттного размера. Буду занят ими.

Забавно. ВЧ-тракт?

Да нет, просто выходники относительно небольшого размера для пары 845-х в параллель. Я, правда, с ним ещё не разбирался, может он и двухтактный. Хозяин говорит - однотактный. Но какой - то странный.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sun Jun 26, 2011 9:47 am 
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Joined: Wed Oct 01, 2008 7:13 am
Posts: 54
Location: Russia
Посмотрел datasheet.
http://www.triodeel.com/845_p1.gif
Могучая лампочка. Может это дросселя и бестрансформаторный выход?
Анатолий, подскажите что означает фраза в Datasheet-е: Plate Resistance?
Load Resistance - это приведённое Ra.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Sun Jun 26, 2011 5:12 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
Насколько я знаю, под Plate Resistance обычно подразумевают параметр лампы, внутреннее сопротивление. То есть, коэффициент усиления лампы делённый на крутизну характеристики.

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