The Eagle Supre - Big SE Amp

[surfsup]

It's frustrating to sit and watch this since the Supre is such a basic and great sounding amp.

Are you still stuck in a hospital bed? Gimme your room number and I'll send you flowers to cheer you up...

Yes it works fine without. I think I know what the problem is I'll try it later today.

[Zippy]

Thanks for the compassion.

Did we ever know that it works without? I just looked back about four pages and don't see anything regarding that it ever worked.

Derailed...

[surfsup]

Zippy, yes it works. In fact, I unhooked the FX loop and rehooked it up without just to be sure nothing weird is going on. Still works. And to prove it...

Amp is a little dirty all around, the voltage switch HT/LT doesn't seem to do much. The mods and their descriptions:

1) feedback 10k/5k switch. Doesn't really do much for me. I don't hear much of a difference at all. Not a useful mod, imo (on this amp)

2) Put the 22k tonestack midR on a switch with a 10k. Definitely hear a difference. Although I don't know which is which because I forgot, one is louder than the other and more growl. Useful mod imo.

3) Cathode bypass switch on V1b to remove the cap from the circuit. I believe when I remove it, the amp cleans up a touch and also gets a bit quieter. Useful mod imo.

4) tube recto, by golly it works. Haven't tried to switch to SS yet. Voltages:

C1, 366
C2, 300
C3, 195

EL34
Pin 1, 21
Pin 2, 21
Pin 3, 361
Pin 4, 296
Pin 5 (mV), 8.1
Pin 6, 297
Pin 7, 21
Pin 8, 21

When I crank it all, there is a scratchy buzzy sound on the pots from 7-9, eerily similar to my X10 clone on the VVR. Either the laws of physics relating to amp lore have ceased to behave in my home, or somethin' fishy goin' on! (minor problem)

Okay back to the FX loop mod. I tried to bypass the plate resistor on the fourth gain stage to bring the voltage higher by locking it to the B+ rail voltage since there is no longer a resistor there. Since the signal from the FX was coming off the plate of the return stage, at a higher voltage, I thought this would help. Amp makes no sound after doing this. Back to square one. Can I post the schemo puh-leeeeze? Just for a day so you guys can look at it?

[martin manning]

On the posting of copyright material, there is no policy that I can find in the forum FAQ, etc. Some forums are very strict on this. There is "fair use" in the US, but the copyright statement in the book says its covered under the Copyright, Designs and Patents Act, which has exemptions called "fair dealing" across the pond. Similar, but different. It may be ok for educational/study purposes like fair use. Ask Merlin? Get a ruling from the Mods?

[Firestorm]

I tried to bypass the plate resistor on the fourth gain stage to bring the voltage higher by locking it to the B+ rail voltage since there is no longer a resistor there. Since the signal from the FX was coming off the plate of the return stage, at a higher voltage, I thought this would help. Amp makes no sound after doing this.

Of course it doesn't. The resistor isn't there to drop voltage; it's there because the output signal develops across it. No resistor, no output.

[surfsup]

Okay I changed a few values and was vague on some with descriptions instead so its not the same circuit anymore, but its close. If the mods want it removed I will remove it. If it gets to stay, I will remove it as soon as the problem is solved. Firestorm, thanks for clearing that up. I guess it works on the cathode follower since the signal is pulled from the cathode.

[martin manning]

No cap to block DC from the loop recovery stage? If not, then the driver stage is saturated and the signal is not getting through.

[surfsup]

Martin,

-I put in a cap between the plate of the return stage and the screen of next stage. No change. But when I probed the plate side, the amp jumped to life and immediately started into what seemed like an endless feedback loop.

This cap was a 0.02 (same cap as the others) I also tried to put a gridleak (220k) off the grid to ground on the fourth stage. The amp was very fizzy and still low volume

[martin manning]

You definitely need a cap there and a ground reference. I'd make the grid leak a 500k-1M. Pentodes and beam tetrodes have screens, triodes just have grids. I haven't even tried to follow this thread, it's too manic! I assumed you made a fresh start with the schematics above.

[surfsup]

martin that's ok. thanks for looking. I'll put the cap back in and put in the Rg but make it big like 1M. But I did do this already and there was sound but it was very fizzy. Just to be clear, the cap and 220k was put on the pin2 of the last stage with the FX lead going to the other end of the cap.

One thing that might be of reference (maybe):

-I paralleled a 56k with the 100k (on second FX stage) to bring the total R down to 35k to increase the voltage at the plate and following screen. Interestingly, (to me), this actually made the amp quieter.

[surfsup]

martin, thanks. Its working. I put the same 22n cap back in with a 1m instead of 220k and now all works. WTF. Adding the cap was #1 thing I did two days ago. Then #2 was adding the 220k.

There's a hum issue now but I think its b/c I grounded the 1M on the second stage's cathode b/c it was convenient, so that's prob why. I should be able to solve that once I recover from "soldering overload". Got SO? I thought so...

[Zippy]

Zippy, yes it works. In fact, I unhooked the FX loop and rehooked it up without just to be sure nothing weird is going on. Still works. And to prove it...

Amp is a little dirty all around, the voltage switch HT/LT doesn't seem to do much. The mods and their descriptions:

1) feedback 10k/5k switch. Doesn't really do much for me. I don't hear much of a difference at all. Not a useful mod, imo (on this amp)

Good deal. Glad to hear it.

5K to 10K isn't enough of a difference (as Ange already explored) - trying going to 100K or even open circuit if you want some hair on it.

G'luck with your looper.

[yowza]

After many delays I'm finally building my Eagle Supre and had a few questions before I get too far along.
Has anyone added a second preamp tube for another gain stage (or anything) or tried another power tube for parallel SE operation? I'll build the amp "stock" to start with but I'm thinking ahead about future options.

After living with your Eagle's for a while what is the latest consensus on NFB and which power tap do you folks use? If I want to install a switch to change power taps what type of switch am I looking for (SPST, SPDT, DPDT etc)?

Also is there anything special I need to do to switch between octal power tubes (6V6, 6L6 and EL34)? It's set up for cathode bias but do the cathode caps and resistors need to be changed when the tube type is changed?
Thanks in advance for any help!!

[RJ Guitars]

... If I want to install a switch to change power taps what type of switch am I looking for (SPST, SPDT, DPDT etc)

I am a hardened serial tasking geezer so I'll cut this to one question for now...

You want an "On / On" switch with no middle position. I put in a used 250 VAC-6A DPDT switch and I expect it will probably last forever. Let me know if you have any trouble finding one, I'm sure I've got another one here.

As far as the results I found that switching between the voltages makes very little sonic impact... I had expected it to be much more significant.

I'll look at those other questions as well but give the other guys to chime in before I post.

rj

[surfsup]

After living with your Eagle's for a while what is the latest consensus on NFB and which power tap do you folks use?

Once i repair my Supre, I will be taking out the NFB switch. Doesn't seem to do much. I am also going to switch V1 for a pentode, that's if i ever get enough time to do it...

I also added another preamp tube. I used it for a FX loop send return. Worked well.

ALso added an octal slot for a 5Y3. Works well, as well.

FX
[img:902:600]http://chicagocadcam.com/ChrisHahn/supre/loop3.jpg[/img]

Chassis with extra sockets
[img:833:500]http://chicagocadcam.com/ChrisHahn/supre/chassis1.jpg[/img]