The Eagle Supre - Big SE Amp

[Structo]

You can also use a switch for that but be sure to switch when the power is off.

[angelodp]

Be interesting to hear if there is any difference.

A

[surfsup]

switch = no. I don't want to "over" complicate things... Not sure what would happen but I'm going to prob stick to the recto tube and just try the SS once to hear the difference.

On the layout, RJ has the R off the ts to gnd on the back side of the switch. I was thinking it would be easier to just solder the R on the cap turret to switch, then run a lead to the ground at input. Is the R on the backside of the switch to prevent switching noise? Or does it matter. If anyone knows for sure and can save me a few solders in a tight place, TIA. Otherwise I'm just gonna go for the R before the switch to gnd.

Also, I really like the slope switch mod on the X10. I am considering that for this tonestack as well instead of a fat switch, any opinions?

[RJ Guitars]

...Also, I really like the slope switch mod on the X10. I am considering that for this tonestack as well instead of a fat switch, any opinions?

I like the idea of the slope switch. I will be interested in your results.

rj

[RJ Guitars]

Here is an old note that Jason from Boozhound labs sent to me a few years back. I was asking him about how many watts we could get out of a single ended KT-88. I gave him some rumored info that the output transformer on the Trainwreck DLM was a pushpull output from a Fender Princeton and that wattage with a KT-88 was said to be 22 watts. All rumors but I learned a tone from his response... bright guy and cool info that I wanted to pass along.

rj


Looks like these JJs can dissipate 42W. The most power you can get
out of a single tube is roughly a quarter of that, so 10W. If he was
getting 22 out of it, he must have been doing something tricky, or
that was RMS power during heavy distortion maybe. Or he was just
hammering the tube - which is totally possible. Forced air cooling,
anyone?

SE transformers are designed to handle unbalanced current, where PP
transformers aren't. This means that using PP as SE, the transformer
will saturate quickly, and probably distort. Which might be part of
the "charm" of what you are describing.

The typical operating point of a KT88 is 250V/140mA, so your
transformer should ideally handle that much current.

This amp seems experimental enough, that maybe you just want to find
something "really big" whether PP or SE and call it good I'm
thinking eBay.

Here is a really bad idea: You could use a big 6.3V filament power
transformer as an output transformer! 120V:6.3 would give you 2.9k
impedance into an 8 ohm load. 240V:6.3V twice that. Now THAT would
be a dirty little monster

jsn

[Cliff Schecht]

That filament transformer would sound like crap if you asked that kind of power of it. The fat laminations used in 60 Hz transformers makes them cheaper to manufacture but no good at frequencies past a few kHz. Plus no gapping means it would get saturated immediately and probably heat up from all of the saturation losses. No bueno..

[RJ Guitars]

That filament transformer would sound like crap if you asked that kind of power of it. The fat laminations used in 60 Hz transformers makes them cheaper to manufacture but no good at frequencies past a few kHz. Plus no gapping means it would get saturated immediately and probably heat up from all of the saturation losses. No bueno..

Yes a clever idea but as he says... a really bad idea. I did think about this when i was trying to come up a complete champ kit for under $100. I didn't try it because I was pretty skeptical of the sonic results. If you follow any of the boozhound labs work you'll find that Jason just loves to experiment, learn, and teach. He did build me some very cool sounding amps as he taught me the basics, still some of the best hardware I own.

rj

[surfsup]

I built my eyelet board for the FX loop and positioned and drilled it for chassis mounting. Going to break for lunch. While I'm putting in the rest of the stuff, I am wondering ...

Should I pull the signal from the last possible spot before the power tube? In the schemo I am thinking of pulling the signal at either the red or black arrow. what do you guys think?

[John_P_WI]

Surf,

What do you mean "pull the signal"? For what purpose?

The point at the black arrow has B+ on it, the red point is after the coupling / dc blocking cap.....

[M Fowler]

Between the volume pot and pin 2 for the loop.

[surfsup]

Whoops I forgot to say for the FX loop. I added another tube and put the black eyelet board together. I am just wondering where you guys would pull the signal from. You're right the black arrow has b+ on it. I assume then after the .022uF cap? The schematic i'm using has a 0.01uF on the input from the preamp (I'm using 400V rated). I assume also I don't need both caps in a row?

[surfsup]

Between the volume pot and pin 2 for the loop.

Okay, I will try that. Thanks.

[surfsup]

Okay I have everything built and all the voltages seem to test fine. Not being familiar with FX loops or Recto tubes perhaps someone can verify what's going on here because I get no sound from the speaker except while probing voltages the occasional static, etc. This PT has a low/high secondary, both voltage sets are posted low then high.

EDIT - No sound problem is solved.

[xtian]

To the right of your 47uF filter cap you've got four diodes, and I can't see anything connected to the negative ends of those diodes. Under-board wires?

[surfsup]

xtian I put those on the board in case I wanted to switch to SS rectification. Right now the red leads are attached to the tube recto just to the right in the same pic. I'm not using a mechanical switch, the leads would have to be soldered/unsoldered.