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Old 23rd December 2009, 02:50 PM   #111
Salas is offline Salas  Greece
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Maybe you will like the resistor more after all, has its merit too. When you check with the gyrator, make sure to keep levels the same for comparing, its gonna up the gain. In what system did you listen to it by now? Any comparison preamps around?
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Old 23rd December 2009, 03:15 PM   #112
vgeorge is offline vgeorge  Greece
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My system now is horn loaded - based on Lynn Olson ideas - around 105db sensitivity with my F5 clone, that I just set up and try to configure crossovers etc, so I can not be sure. Your phono also. What I know is that music is much more alive and real maybe than with a passive pot previously used. Even if gain was enough before, F5 needs an active pre for sure.
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Old 23rd December 2009, 03:19 PM   #113
Salas is offline Salas  Greece
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This 12B4 with the simplistic Reg will be hard to beat in the future. One of the best things you could add to drive the F5. See for best mechanical decoupling of your 12B4s since you got ''real'' speakers, and you are mainly set.
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Old 23rd December 2009, 03:55 PM   #114
vgeorge is offline vgeorge  Greece
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I am thinking for a suspened suchassis for the tubes. Also add some dumping to the case. It' s a Hammond aluminium one. As this was was the first thing I build with tubes I wanted to have some sound first and then deal with details as my confidence builds up.
You can have look at the speakers I am setting up.
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Old 23rd December 2009, 04:01 PM   #115
Salas is offline Salas  Greece
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The real McCoy I see. I am afraid that some active anode load (any type) by upping the gain and adding some of its hiss, may lead you back to the resistor, because with so sensitive speakers it may add some ''artificiality'' taste. But you will see for real, soon.
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Old 23rd December 2009, 04:05 PM   #116
vgeorge is offline vgeorge  Greece
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Quote:
Originally Posted by Salas View Post
The real McCoy I see. I am afraid that some active anode load (any type) by upping the gain and adding some of its hiss, may lead you back to the resistor, because with so sensitive speakers it may add some ''artificiality'' taste. But you will see for real, soon.
I am afraid of that but it' s fun to try though!
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Old 23rd January 2010, 11:52 PM   #117
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The real McCoy I see. I am afraid that some active anode load (any type) by upping the gain and adding some of its hiss, may lead you back to the resistor, because with so sensitive speakers it may add some ''artificiality'' taste. But you will see for real, soon.

Hi, Ok, so is the final schematic using LEDs or just a MOSFET? There is a manufacturer that I am attempting to convince to build these as in his regular lineup of preamps, to get him away from the standard 12AU7 tube preamp.

So can someone just email me the schematic with the list of parts, running at 15MA at 20V. Not wanting to do any experimenting, just want to build it and be done.

What can I expect the gain to be, and the output impedance to be. I would probably for the grid stoppers use 4K each to have a good value and also to deal with the ringing of any form of microphonics. I also would need the exact specs for the transformer. I was thinking of simply using a diode supply to keep the power supply somewhat simple. Want to build this in one box.

As an idea, people have used the LED for regulation. Why not just use another 12B4 tube. They are also supposed to be good regulators in there own right.

I myself can not see the pics, because I am blind. So building this piece would be a nice project. I will have to ask some assistance of you guys here and there, like what do you suggest for the layout chassis size and so on. What size ohmage of pot is suggested?etc. etc. etc.


Thanks guys for any assistance.

You can email me at raybronk@gmail.com


Ray Bronk
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Last edited by ray bronk; 23rd January 2010 at 11:55 PM.
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Old 24th January 2010, 11:00 PM   #118
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Default To Build a 12B4 Preamplifier from scratch

Hi, Ok, so let me ask this then. In this thread there has been several, well, a couple of schematics for the 12B4. Ok, so which one do I use with the exact values so I will be doing 15MA and 20B. I have not seen any replies to my queries yet, so I will ask this also. If I use a Class D supply, what do I need then to have the supply see at its output, ... B+ filament of 12,? and what other parameters? I'm trying to see if I can make this as simple as possible without sacraficing the quality of sound produced by this preamp. So I just need the schematic and the details as to what the power supply needs to see. I thank you guys for any help at all. I hope I get a response soon.

Ray Bronk


I CAN MAKE THIS AS SIMPLE AS POSSIBLE WITHOUT SACIFRICING QUALITY.
Quote:
Originally Posted by Salas View Post
The real McCoy I see. I am afraid that some active anode load (any type) by upping the gain and adding some of its hiss, may lead you back to the resistor, because with so sensitive speakers it may add some ''artificiality'' taste. But you will see for real, soon.
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Old 24th January 2010, 11:18 PM   #119
Zen Mod is offline Zen Mod  Serbia
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Originally Posted by ray bronk View Post
.......
maybe this will help you :

12B4A preamp - DIYAudio.rs

pics and schematics aren't in Serbian , and you don't need to register to see graphics

edit: shunt reg is further down the thread , one per channel
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Last edited by Zen Mod; 24th January 2010 at 11:21 PM.
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Old 24th January 2010, 11:59 PM   #120
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Originally Posted by Zen Mod View Post
maybe this will help you :

12B4A preamp - DIYAudio.rs

pics and schematics aren't in Serbian , and you don't need to register to see graphics

edit: shunt reg is further down the thread , one per channel
Ok, thanks. Since I am not able to see the schematic due to blindness, I will have to ask someone else to look at this. this is kinda why I had posted what I had posted earlier. I know this is simpler to build than a typical 12au7 preamp. I wanted to know what I need to do with reference to the power supply voltages and current. I think I will look for a Class D supply that can give me what I need, and supplement as far as the supply goes to make this sound really good. I will pass this along. Is this the same schematic that the guy from Grece built, or is this the one from Brian or Frank, ... or neither?

Ray Bronk
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