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Old 11th August 2011, 09:51 PM   #1
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Default Need a proposal for a stereo amp


Im new at this forum and have never built a tube amp before. I have been looking around at the forum for a good schematic but i think i need help with choosing the right one. I need a proposal for a amp that can run two 50w (4 Ohm) speakers in stereo. Do any of you have a good proposal?
Since this is my first tube project it would be nice if it was not a to complicated schematic.
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Old 11th August 2011, 10:02 PM   #2
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Need a bit more information. I am afraid that 50W speaker is pretty much meaningless. I presume that it is some sort of power handling specification but without the conditions stated that would make it at least helpful in knowing how not to break it. However even with qualifiers it doesn't help much in determining what type of amplifier you will need.

Here are some things that will help the folks help you.

1. Size of your expected listening room.
2. What type of music you listen to and at what relative volume (background, earsplitting, something in between...)
3. Sensitivity of your speakers (usually expressed as ##dB at 1 Watt at 1 meter or something on that order)
4. Speaker type (full range, two way, three way, Kabuki. )

That will start to give a us a clue as to what direction you might want to go.
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Old 11th August 2011, 10:18 PM   #3
kevinkr is offline kevinkr  United States
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Hi Freestream, Welcome to the forum..

Perhaps you could fill us in on the type of music you like to listen to, at what volume, and in what size of room. Also some further information on the type of speaker and its efficiency would be helpful..

I imagine a PP amplifier would probably be the right way to go depending on the power you require.. Tubelab's simple PP might be worth checking out.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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Old 11th August 2011, 10:21 PM   #4
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1. The room is about 13 square meters.
2. The music can differ from time to time but mostly i listen to metal and everything in between . Iam not realy playing at a earsplitting level but it is not far away from it.
3. Those I have right now is at 91 db and a frequency range at 50-32000 Hz.
4. They are two way
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Old 11th August 2011, 11:08 PM   #5
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Ok. so if I did the calculations right that is about 140 square feet so not a huge room and relatively efficient speakers. I am thinking that push pull EL84 of which there are many variations might be a good choice. Could go with beefier tubes but though I haven't built one everything that I have heard indicates that it is hard to go too far wrong with these bottles.

Another completely different direction that you might want to try if the inner details are important to you is a fairly beefy single ended pentode (or UL) might also suffice. Your speakers don't go really low so the utmost in deep bass performance is not really needed (you can always add a powered sub). So far my experience with a SE UL KT-88 amp that I am working on using far less efficient speakers leads me to believe that you could get satisfaction that way too.

Lots of possibilities really with your situation.
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Old 12th August 2011, 12:55 AM   #6
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Originally Posted by kevinkr View Post
Tubelab's simple PP might be worth checking out.

Another PP which I know works well (I built an EL84 version aka Poddwatt, recently) is the 'Oddwatt' series from Bruce Heran. Scratch build (details are on the web) or buy a kit from Oddwatt.

Lots of choices out there, but probably something on the simpler end of the scale would be best for a 1st build?

The 4-ohm requirement shouldn't be a problem as long as you buy output transformers with 4 ohm taps, to suit the schematic you choose.
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Old 12th August 2011, 12:38 PM   #7
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6c33 SET.
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Old 12th August 2011, 02:05 PM   #8
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@VictoriaGuy: I have looked at the Oddwatt amp kits and they are a bit to expensive, i would rather choose one that is a bit more cheep to begin with.

@mashaffer: Do you have any good push pull EL84 schematics that you would recommend?
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Old 12th August 2011, 02:37 PM   #9
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Well how about the Darling amp? Cheap and sweet. With that speaker efficiency has all the power he'll need.
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Old 12th August 2011, 04:20 PM   #10
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@MrCurwen: Hmm can you be a bit more specific? I googled Darling amp and got several hits
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