L'Amp: A simple SIT Amp

Oh so good to hear that. Actually can't wait to receive them , in the meantime
I am listening the same little amp with the LU1014D , no degeneration , no cascode . So sweet .

Hi Stefano,

It may be a little off topic, but could you post the schematic you're using? I have a few LU1014D I'd like to use for something, and this amp looks like fun!

Cheers
Nigel
 
Pass DIY Apprentice
Joined 2001
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I appears that other grades have other Vp, Vgs charracteristics. I don't have any definitive information.

KD-33 works well in Figure 11, because it runs (at the desired sweet spot current) with a negative Vgs equal to the voltage across the source resistor. Other grades will behave differently, perhaps poorly, or perhaps go up in smoke. Not having other grades to try I can't say.

My recommendation for other grades is simply to build Figure 10 and adjust the bias for 2.5A or so. (Vds approx. 13.5V) In any case, Figure 10 sounds a bit nicer, if you're up to it.
 

ra7

Member
Joined 2009
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let's do the math: looking at figure 11, 2 channels x 50 V x 2.75 A = 275VA. This is class A and normally you would need at least twice this size... so figure on a MINIMUM of 600 VA. 800VA is best.

Mike uses two 400VA transformers, so this calculation is not too far off. This one should work:
http://www.antekinc.com/details.php?p=128

It's even got some 18V and 12V windings to develop bias.
 
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Mono vs Stereo

Spot on, 300VA minimum per channel.

My amps are mono. I dig monblocks. I used the 400VA from Antek because they were only $4 more and I find this gives me a bigger performance boost than spending $4 more anywhere else, e.g. shiny binding posts, or fancy wire.

I have thought a stereo 800W transformer would give a lower impedance than 2 400W mono blocks. The stereo transformer with single or paralleled windings has half the resistance of a transformer with a rating of half the watts. All other things being equal, that is, same total capacitance in stereo vs mono, the stereo should sound more powerful.

There may be diminishing returns at some point.

For the purist it may be physical limitations, can't lift the stereo amp with 3600W transformer and four farads of capacitance. I build stereo amps when I can. I have built mono tube amps because I couldn't find power transformer's large enough for stereo, rectifier tubes become a problem and couldn't lift the beast if I did.

Michael, I am interested if you have compared?

Just my thoughts.

Rush
 
Tubey or not tubey?

Hiya Mike,

Do you know if anyone has adapted the 2sk82 for use in Pete Millett's Starving Student headphone amp?

I built one of them and I like it, but I wouldn't complain if it got tubier. But I don't know how to mod a circuit like that.