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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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PostPosted: 05 Sep 2009, 00:58 
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Joined: 03 Aug 2008, 20:22
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Location: Denver, Colorado
I have been away for a while, but picked up on your post.

The quickest, cleanest, and easiest PS is a 12v 7ah UPS battery. They are used in APC ups's and sometimes emergency lighting boxes, if all they are $24 brand new. If you know any IT guys they usually have a couple old but good ones laying around.


:cop: Lead Acid Battery Charger info split to: The cheapest lead acid battery charger ever!


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PostPosted: 20 Oct 2009, 07:34 
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Hey guys! Noob here, just bringing this old thread back. Im planning to build my first preamp and was thinking, could this headphone amp possible? Thanks in advance.


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PostPosted: 20 Oct 2009, 12:43 
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Yes you could. Do you know how much voltage gain you need?

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PostPosted: 01 Jan 2010, 11:28 
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Hi All! I am a newbie to electronics. and I Have 2 questions.
I want to start from building an easier amplifier (on batteries). I understand all the schematic but I cant understand how does that Voltage Generator look?is it just an volume regulator?

On the schematic there is only 1 channel showed but in reality there are two. Should I redraw the schematic for two channels?How should I deal with that?

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PostPosted: 01 Jan 2010, 15:02 
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Koval

Welcome to the forum, well you are in luck as I am in the process of putting a tutorial together and a PC board.

The power supply is as easy as a sealed lead acid battery 12v 1.3ah or larger and fuse and a switch.

I use an old canon K30120 13v switch mode power supply. These can still be found rather cheaply on ebay, there are other comparable power supplies, but this one has survived accidental shorts and leaving my amp on for a few days.

The circuit is focused on very basic common cathode volt amp and a source follower buffer. I changed the source load resistor to an LM317 for a stable constant current. You can find more info on Gios build and link.
http://diyaudioprojects.com/Solid/IRF61 ... phone-Amp/
http://diyaudioprojects.com/Technical/V ... Regulator/

For now here is the new schematic, a new thread will be up very soon.
Attachment:
NP-100_12v_lm317.PNG


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PostPosted: 02 Jan 2010, 14:44 
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Hi Rogers

It's great to see the new schematics uploaded from you. :up:

I can't get away from some thoughts. I'm wondering .....if any of the illustrations below, could be workable :confused:

I guess there could be drawed "more" current through the MosFet, either bi and/or serial the LM317 / 12AU7 fillament. :idea:

Maybe it's completely nonsens ....hehe. :mrgreen:

Image

Image

Image


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PostPosted: 02 Jan 2010, 19:55 
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Hi John,
Its been a while,
Your idea can be achieved by eliminating the voltage regulator and using the heater as a source load, but there will have to be some further modification for proper mosfet bias and plate voltage, as the B+ will have to increase.

Pete Millet has done this with his Starving student amp. http://www.pmillett.com/starving.htm


For current time I have a pcb constructed and want to make it as simple and low part count as possible. This way someone with very little electronics background can make a tube amp. I am finishing the tutorial and now going over some casing ideas.

Here is a peek at the prototype pcb. The new version is has less unused space in front and back measures around 50mm x 105mm.


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PostPosted: 03 Jan 2010, 00:20 
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Joined: 26 Oct 2008, 13:48
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Location: Central California coast
Hi Roggom,

I have a simple question about the HV 12AU7/IRF612 HP amp. What is the max current draw for the MOSFET supply? I ask as I am sourcing the PST. I figure the draw on the 160V supply to the tube plate is only 10 to 15mA split between the 2 tube sections, maybe less. But I haven't a clue about the MOSFET!! :?:

Thanks,
Mike 8>)


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PostPosted: 03 Jan 2010, 02:05 
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Mike,

The max current draw will of course depend on the Drain voltage and the value of the source resistor. As you see from the schematic, the 18v drain voltage was derived from tapping the between the back to back transformers. So with a 100 ohm resistor, the draw is only shy of 100mA (this is with potentiometer p1 set for a ~9.5v at the source. Because the transformers are 1.2 A, using them back to back will drop the va rating to 600mA max for that part of the circuit. That is why the heaters run from a separate supply.

If you make a separate power supply for the MOSFET you can increase the drain voltage, but remember you are only driving headphones, so there is no need for more than 1.5 watts. Anything more than that, you will be only be wasting in heat.

I have attached the TINA-TI schematic, the program can be found here: http://focus.ti.com/docs/toolsw/folders ... na-ti.html
Attachment:
NP-100HV.zip

it is real easy to use, and you can simulate frequency response, voltage drops, current etc. There are even scope simulations and dvm readings, all before the first resistor is soldered.


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PostPosted: 03 Jan 2010, 13:54 
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Joined: 26 Oct 2008, 13:48
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Location: Central California coast
Thanks, Roggom ;) that helps. Also the Tina-TI, didn't know it was a Texas Instruments implementation of Spice. I'll give it whirl. :xfingers: How are you modeling the tube?

Right now this is a "design" project while I finish up a couple other projects already on the bench. I plan on using your little amp to drive my B&O U70s from an iPod. I'll probably use 6C4s as I have a few to play with, and I have a couple IRF630 MOSFETs.

Mike 8>)


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