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Old 23rd December 2011, 04:21 AM   #21
ke4mcl is offline ke4mcl  United States
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in that schem what does the symbol with two overlapping circles at the end of one of the resistors between the 12at7's mean?
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Old 23rd December 2011, 09:31 AM   #22
dhaen is offline dhaen  Europe
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Originally Posted by ke4mcl View Post

in that schem what does the symbol with two overlapping circles at the end of one of the resistors between the 12at7's mean?
Constant Current Source, as drawn on page 2.
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Old 23rd December 2011, 04:45 PM   #23
ChrisA is offline ChrisA  United States
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Originally Posted by bigaudioscotto View Post
.. I like big warm punchy bass
and thick syrupy mids and large soundstage ..
Maybe what you need are speakers. A good amp sounds like "a wire with gain".

If you are looking to create a sound you should be looking at musical instruments amps and PA systems. Those are what make music. Stereos reproduce sound. That is completely 100% different from producing sound.

The first questions to ask yourself is "How big is the room? How far am I from the speakers? What volume level do I want? (Best if you can saying terms of dB) Then you need to know the sensitivity of the speakers you will be using.

OK now you know your minimum power in watts. You may not like that answer and then you change something above (most likely the speakers) Finally you have the minimum watts. It is reasonable to use a mutiplier on that minimum in order to have some headroom.

For most people they settle on about 8 to 12 watts per side and speakers to rate "high 90s"

If you have some old speakers from the mid 70s with senitivy in the low 80dB range this tube amp is going to be quite expensive. You'd be best to replace the speakers as 50W per channel tube amps are NOT a first time project and are actually quite rare.
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Old 16th June 2012, 07:22 PM   #24
disco is offline disco  Netherlands
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On the other hand... a tone control can be a benefit to compensate for boominess in a room. As is the placement of the loudspeaker of course, while not everyone is in multichannel.
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Old 16th June 2012, 08:14 PM   #25
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Originally Posted by Eli Duttman View Post
Lot's of good options have been presented. Naturally, I'll grind my own axe.

Build an "El Cheapo" with triode/ultralinear (UL) mode switches. The reasonably efficient open baffle speakers will produce "bleeding ear" volumes for heavy metal, etc., in UL mode. Triode mode offers greater finesse, for jazz and classical.

The attached schematic (triode mode) shows 12AQ5s, but any 6V6 family tube will work, without parts value changes. Please notice that a line stage is unnecessary. Use good O/P "iron", like Dynaclone Z565s, and full bass extension is available. Simply change the bandwith limiting combo at the I/P from 56 nF./100 KOhms to 68 nF./127 KOhms (RN65).

Jim McShane is the man for tubes and parts. Well under $100 buys a full set of power magnetics (will list if interested) from Allied.

I noticed that the first stage smoothing capacitors are 820+820 uf (410uf in effect). Why are they so big, it makes no difference at all in this position.
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