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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 14:54 
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Joined: 11 Dec 2008, 10:23
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Location: Austin, TX
This amp would work great for the headphones I use at work, which is the Senn HD280 Pro (64 ohm).

Has anyone used a higher impedance headphone with this amp? I've got a pair of Senn HD580s which I believe run around 300 ohm. From what I've read, it's better to use an amp designed for these types of 'phones.

There seem to be some great sales on ebay for 12AU7s. I could build one for work and home with plenty spares left over in case of tube failure.

I still remember when Dad and I went to the local convenience store (7-11) or Radio Shack with a bag of TV tubes for testing.

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Rega P25 and LFD Mistral phono (analog) or Oppo DVD Player (digital) > Aunt Corey's Buffered Pre > Adcom GFA 535 > Spica TC-50


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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 17:48 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
I have a few versions in the thread, for high Z headphones you will need a higher voltage swing so the 160 volt version is better suited. I can drive my Sennheiser HD420's (600 ohm) or Grado SR 125's without issue.


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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 18:16 
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Joined: 31 Dec 2008, 15:34
Posts: 441
Location: Denmark
CrazzyAbtTubes wrote:
Really! I salvaged many of them from old computer monitors. I also have IRF610 x2, IRF640's and who knows how many other versions I have, lots of large fets from dead computer monitors and power supplies.

Hi

You can use several of different N-channel Mos-Fet's in this construction. I've just finished it, an i'm using BUK453 Mos-Fet's and it's sounds great. I don't like regulators in this construction, in my ears they kill's something in the music. I like this amp. in the simple version very much, but i had to make som changes and adjustments before i was satisfied.

Thanks to Mr. Gomez and this forum, where i've found it. :P

My brandnew amp can be seen in the link below ( pictures included ), it's all made out of scrap. :mrgreen:
http://www.hifi4all.dk/forum/forum_posts.asp?TID=70777&KW=krammeacoustics


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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 21:00 
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Joined: 03 Aug 2008, 20:22
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Location: Denver, Colorado
Nice work, I like the look you chose. The knobs add a nostalgic feel to the amplifier.

This amp can take many shapes as It is designed to be made from part bin components. Great job!


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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 22:55 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hello KrammeAcoustics.

Welcome to the forum. I'm glad to see that you have found the site useful and inspiring.

Great work on your project and thanks for sharing the results with us. :up:
Cheers,
Gio

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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 23:06 
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Joined: 11 Dec 2008, 10:23
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Location: Austin, TX
roggom,

Thanks for pointing that out. I went from the start of the thread to the last page for the conclusion. :down:

That will teach me.

My one dilemma is that now I have to build 2 versions. I'll opt for the low voltage version first because I listen through my laptop at work and it gets fatiguing.

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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 02 Jan 2009, 23:19 
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Joined: 31 Dec 2008, 15:34
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Location: Denmark
roggom wrote:
Nice work, I like the look you chose. The knobs add a nostalgic feel to the amplifier.

This amp can take many shapes as It is designed to be made from part bin components. Great job!

Thanx :P

The knobs nostalgic look comes originaly from this B&O 511K radio Image from the 50's, i've got two of them. I took out the amplifiers and tuner parts and modified the two amp's a little and ( then ) used them for "stereo" as two monoblocks ( just for fun ). Most of the tunerparts was send to the junkyard. The cabinet from the 511K will be used in a later project, where a new DAB radio. New speakers and a modern amplifier will be integrated in it and will be used in my flat, which is made a bit nostalgic 50 - 60 a'like.
Pics of the slaughtered 511K here: http://johnkramme.dk/hifi/bo/

gmilitano wrote:
Welcome to the forum. I'm glad to see that you have found the site useful and inspiring.

Great work on your project and thanks for sharing the results with us. :up:

Thanx again Gio, i'm so happy for the warm welcome.

This place was just what i was looking for. :up:

Regards from Kramme :mrgreen:


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 Post subject: Re: 12AU7/IRF612 update
PostPosted: 03 Jan 2009, 18:30 
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Joined: 31 Dec 2008, 15:34
Posts: 441
Location: Denmark
Hi again
I've got three 12 V akku's in stock and i was wondering ...hmmm :? Do you think the version in the diagram below, will work ? With 24 V connected to the tube, and 12 V to the Mos-Fet. Is it nessesary to bias the Mos-Fet or not ? It's one of the first selfmade schematics in TINA-TI from my hand, so you'll have to be nice to me, if not ...heheh :mrgreen:

Image

In few days i'll get my new Sennheiser HD650, so i want an amplifier nr. 2 with more current output, than the 12 V version for my Philips SHP8900.


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PostPosted: 03 Jan 2009, 21:11 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
If you want to add another battery this will be easy, no need to split the supply, run the entire thing from 24 volts. Just remember to wire the heaters seperate to only receive 12v.
If you split the power supplies you will need a coupling capacitor and another voltage divider like the one on page 2 of this thread.

With 24 volt supply you will have around 9~10 volts of swing and ~200mW, decent voltage and more than enough current. SHould sound very nice. Of course never power your amp with the headphones plugged in.


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PostPosted: 04 Jan 2009, 10:39 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi guys, I found my mosfet follower sounded better with more voltage, so I would try 24v.

roggom wrote:
Of course never power your amp with the headphones plugged in.

Are you doing this all manually or with a switch. I need to setup some sort of idiot proof method to do this. Have you thought about a relay?

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