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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Mon Jul 11, 2011 5:18 pm 
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Posts: 238
directly without attenuator.

Just saw ur latest clip... damn, it sounds good.... rock to bluesy to mellow.......

but a question, what is the return path of the cathode current on the second triode for the latest schematic??

About patenting it... go for it...


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Mon Jul 11, 2011 7:16 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
directly without attenuator.


So, my last advise would be to borrow somewhere an oscilloscope and see what happens there.

Quote:
Just saw ur latest clip... damn, it sounds good.... rock to bluesy to mellow.......


Yes, it was what I tried to achieve. But it is hard to balance it well for all genres...

Quote:
but a question, what is the return path of the cathode current on the second triode for the latest schematic??


R13 to the secondary of the output tranny.

Quote:
About patenting it... go for it...


Patents cost money, and worth only when you have more money for lawyers.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Mon Jul 11, 2011 7:52 pm 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
wavebourn wrote:
but a question, what is the return path of the cathode current on the second triode for the latest schematic??

R13 to the secondary of the output tranny.


That would make it a (22k+1.5K+DCR) of secondary cathode R??


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Mon Jul 11, 2011 8:03 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
wavebourn wrote:
but a question, what is the return path of the cathode current on the second triode for the latest schematic??

R13 to the secondary of the output tranny.


That would make it a (22k+1.5K+DCR) of secondary cathode R??


Yes, but the grid leak (volume pot) is connected across 1.5k only. Such a way it is bootstrapped by feedback, so 1'st triode load is greatly decreased.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Mon Jul 11, 2011 8:25 pm 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
wavebourn wrote:
quikie22 wrote:
wavebourn wrote:
but a question, what is the return path of the cathode current on the second triode for the latest schematic??

R13 to the secondary of the output tranny.


That would make it a (22k+1.5K+DCR) of secondary cathode R??


Yes, but the grid leak (volume pot) is connected across 1.5k only. Such a way it is bootstrapped by feedback, so 1'st triode load is greatly decreased.


So that means the grid leak (and thus the grid) is referenced to the voltage developed on the 1.5k resistor... but with all the resistors in the cathode path, would it not shift the anode-cathode voltage value and ultimately shift the curve and operating points?

What is meant by bootstrapping by feedback?

sorry for noobie questions


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Mon Jul 11, 2011 10:24 pm 
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Posts: 54
Location: Russia
Анатолий, получился интересный звук. Что-то яркое, эстрадное. Напоминает звучание "Королевских гитар" или ранних "Paper lace". В-общем: винтаж Applause

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jul 12, 2011 8:28 am 
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Шаман, типа...

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Location: Pleasant Hill, California
AlexR wrote:
Анатолий, получился интересный звук. Что-то яркое, эстрадное. Напоминает звучание "Королевских гитар" или ранних "Paper lace". В-общем: винтаж Applause


Это хорошо, когда что-то напоминает. Музыканты любят подражать. Very Happy

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jul 12, 2011 8:32 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
So that means the grid leak (and thus the grid) is referenced to the voltage developed on the 1.5k resistor... but with all the resistors in the cathode path, would it not shift the anode-cathode voltage value and ultimately shift the curve and operating points?


Yes, it equivalent to decreased B+.

Quote:
What is meant by bootstrapping by feedback?


Bootstrap is a positive feedback to the resistor, it increases it's dynamic resistance many times such a way as applied.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Jul 12, 2011 10:51 pm 
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Posts: 238
Just saw your post on the room heater amp.. what is the tube? I am guessing a transmiter tube? Prefer to PM?


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Wed Jul 13, 2011 7:56 am 
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Шаман, типа...

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Location: Pleasant Hill, California
quikie22 wrote:
Just saw your post on the room heater amp.. what is the tube? I am guessing a transmiter tube? Prefer to PM?


It is 845.

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Fri Jul 22, 2011 5:02 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Here is the chassis, I am making it from a frying pan I bought for about $5 in Ross.


Attachments:
cassis1.gif
cassis1.gif [ 72.73 KB | Viewed 4644 times ]
chassis2.gif
chassis2.gif [ 94.9 KB | Viewed 4644 times ]
chassis3.gif
chassis3.gif [ 98.28 KB | Viewed 4647 times ]
chassis4.gif
chassis4.gif [ 116.24 KB | Viewed 4655 times ]

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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 Sep 13, 2011 10:27 am 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
Completed my amp. Decided to go for GU-50 pentode as output stage with 6N2P as first stage.

Basic circuit as per first circuit designed by Anatoliy. Not included the feedback circle and tone control yet.

No guitar to test with, but connected to a signal source it works. Sounds a little thin with no harmonics. Hum is there but I suspect is due to the low capacitance (350uF) and lack of choke of the power supply.

Will try bypassing the GU-50 cathode resistor to reduce feedback and hopefully increase some second harmonic.


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Tue Sep 13, 2011 11:23 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
Do you mean the first version with diode from anode for sagging?

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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Wed Sep 14, 2011 4:57 am 
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Joined: Mon Mar 22, 2010 1:10 am
Posts: 238
I omitted the diode Smile


 
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 Post subject: Re: Sub-miniature guitar tube amp
PostPosted: Wed Sep 14, 2011 10:35 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7317
Location: Pleasant Hill, California
quikie22 wrote:
I omitted the diode Smile


Right. It was too much sagging with diode. Very Happy

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