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 Post subject: Smallest possible amp
PostPosted: 20 Mar 2010, 13:31 
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Joined: 02 Mar 2009, 12:41
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Location: Vänersborg, Sweden
A clever guy came up with an idea to have a thread of possible smallest amp, and I am just a poor instrument to implement the idea ...

Consider this as a thread where pics and descriptions of small amps could be published.
There will be no rules as amplifiers can have various sizes depending on output power and choice of tubes. Of coyurse a miniature KT88-PP amp will be big, but how un-big can it be.

This is my factory made Chinese 6P1P-amp:

Image

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“If you don't know where you are going, any road will get you there.”
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PostPosted: 20 Mar 2010, 14:15 
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Joined: 28 Oct 2009, 02:34
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Location: Utrecht Nederland
Hallo everybody and Magnus, of course.

Here are the pics of my first KT88 OddBlock amp. Kind of cute and small, I really loved it. But it was toooooo small for being noise free, so it's guts moved into a big Hammond enclosure.


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Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project


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PostPosted: 20 Mar 2010, 14:17 
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more pics


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Greetings from Holland, Ben

My DIY Audio Projects:
- Single-Ended 12B4A tube amp with ECC802S driver
- DIY Push-Pull KT88 tube amp (OddWatt amp from scratch)
- 832 / GU32 tube push-pull amplifier project


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PostPosted: 20 Mar 2010, 14:26 
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Location: Vänersborg, Sweden
What are the main obstacles?
Noise and hum :headphones: . Heat ... :hot:

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PostPosted: 20 Mar 2010, 20:51 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
Heat and noise are pretty big obstacles, but there is also power limitations in terms of size, and the question and motivation of "how much patience are you willing to give up to get wire something that is 2"x2" in size...."

Here is a cute little guitar amp I found..... a wopping 0.5 watts!
http://zvexamps.com/amp_view.html

And for stereo....
http://www.impamp.com/

I think Ben's KT88 amplifier qualifies as being pretty small in terms of power and tube type used.

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PostPosted: 21 Mar 2010, 02:12 
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I think the ZVex amp is Hybrid... right ?

I love posting mine :)
viewtopic.php?p=13138#p13138

If there is FullTube Tiny amp for Headphone or Home speaker ... let me know, I love building tiny one.
I was thinking Nuvistor ..... I know it's too low for power but .... using it as puss pull ? bad idea ?
just for Portable headphone amp ?
anyone ?



Cal


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PostPosted: 21 Mar 2010, 11:16 
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Location: Dartmouth, Nova Scotia
I have a bunch of Nuvistors, with ultra miniature sockets, and I have three strange ones that are part ceramic and have caps on them.

Here is a neat site with some diagrams....
http://www.thevalvepage.com/valvetek/Nu ... vistor.htm

oooooooooh, here is a preamp!
http://www.tnt-audio.com/clinica/preamble_n.html

And these are like the ones I found....
http://www.r-type.org/addtext/add035.htm

Just some fun stuff for ideas, since there is no tube that I know of that is smaller than a Nuvistor. :D

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PostPosted: 21 Mar 2010, 19:57 
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Nuvistor, nice link.
I love that tiny tubes, too bad it's too small to create an Amplifier or Headphone amp.

is there a schematic somewhere ?
anyone tried ?

Cal


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PostPosted: 22 Mar 2010, 15:47 
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Joined: 15 Mar 2010, 08:32
Posts: 487
Location: Canada
Soundbrigade wrote:
Smallest possible amp

Hi.

I think I have breadboarded the world's "smallest possible amp" & also 'simplest possible amp' todate - a one-stage MM cartridge tube phonostage/passive linestage. I have enjoying listening to it for many months, seated it right on top of the metal mesh top cover of my super-upgraded Dynaco ST-70 power amp. I just take it easy as it is a breadboard anyway.

I love its sound - so transparent, so dynamic & so musical. All my audiophile friends listened to it & everyone wanted me to build same one for him. My answer is:- "Let see until I build it properly in a small plastic box - 7.5" x 4.5" x 2.5" !!!! Am I crazy? Yes, maybe as I love cute looking small builds.

The heater is & will be powered by a 6V rechargeable SLA cell outboard & the 440V HV is & will be
tapped out from my Dynaco power amp.

It is a major handcraft challenge even to a veteran guy like me who already built & using a dual monaural 2-stage phonostage using discrete biplars & battery supplies ALl built in a tiny plastic black box only 2/3 size of the box for the tube phono/linestage above.

Despite the box is super small, this tiny tube phono preamp will be fully loaded with 440V HV regulator, phono/line I/P jacks, line level control, & powered sub-woofer O/P, switchable on/off from the signal path. The last thing is to let the subwoofer interconnect attached to the signal path when not in use. This is something so crucial sonically & yet so many overlook.

c-J

PS: being so busy with my daily works, I don't know how long it will take me to move the breadboard into its small designated housing although all the jacks & switches are already installed. I don't want to rush it, as I am now enjoy the breadboard bigtime.

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PostPosted: 22 Mar 2010, 18:03 
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Joined: 14 Oct 2008, 17:35
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If you have any pictures of this phono stage, I wish to see them, also, what tubes are you using and how much gain do you actually get from it? It sounds more like a "preamp" than an actual "amplifier" but this thread can apply to any thing with a Tube that is really small.

calico wrote:
Nuvistor, nice link.
I love that tiny tubes, too bad it's too small to create an Amplifier or Headphone amp.

is there a schematic somewhere ?
anyone tried ?

You should be able to build a simple preamp no problem using any Nuvistor, my uncle has a phono stage that uses two 6DS4's, I am going to try making my own modified circuit for the pair of strange Nuvistors that I have.

Here are a couple of my small projects, though they could be smaller....
Attachment:
50EH5 amp2(small).jpg

Attachment:
Mini tube preamp in use(small).jpg


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