The Eagle Supre - Big SE Amp

[RJ Guitars]

I didn't want to hijack my own thread with a product distraction but I did want to point you to this thread... http://ampgarage.com/forum/viewtopic.php?t=15681
rj

[RJ Guitars]

I am making my way back to the Eagle Supre to add some final touches.

One thing I wanted to do was play with the voicing on the amp. I was looking over the coupling cap choices that are in the rev 1.4 version and I was wondering if it makes any sense to have C3 as .02uF while I have C2 and C4 at .01uF...

After I posted the above note I worked with the Duncan tone stack calculator to help me work up the best values for this build. I combined what looked best according to the calculator with what my ears were telling me sounded best and made a couple subtle changes to the drawing specifications.

I posted a new layout and schematic on page one of this thread. I will be curious if anyone else has played with the coupling cap values?

rj

[Berger]

I am making my way back to the Eagle Supre to add some final touches.

One thing I wanted to do was play with the voicing on the amp. I was looking over the coupling cap choices that are in the rev 1.4 version and I was wondering if it makes any sense to have C3 as .02uF while I have C2 and C4 at .01uF...

After I posted the above note I worked with the Duncan tone stack calculator to help me work up the best values for this build. I combined what looked best according to the calculator with what my ears were telling me sounded best and made a couple subtle changes to the drawing specifications.

I posted a new layout and schematic on page one of this thread. I will be curious if anyone else has played with the coupling cap values?

rj

Interesting. Do you still prefer it with the tone stack bypassed?

Aaron

[RJ Guitars]

... Interesting. Do you still prefer it with the tone stack bypassed?

Aaron

Yes, it still has the most full sound in that mode. There is not an exact equivalent to the tonestack I am using in the Duncan calculator but if I use the Fender model, then I see that the mids are still scooped out unless I go to a really large resistance on the mid pot... like 100K. I haven't actually tried this in the amp yet but it has me curious enough to give it a shot.

I'll post results when I get them,

rj

[Berger]

gotcha.

Looks like mine should be here Friday. I'm really looking forward to getting it. I want to sue this as my experiment amp. Maybe try some different tone stacks. Change the 12ax7 out for a 6u10 and parallel the lower gain triodes. Please with the negative feedback loop.

Fun stuff like that.

Aaron

[surfsup]

I like the stock 500p/20n/20n caps but swapping the treble pot for a 250k. Seems to look better on the duncan modeler. One of these days I will probably swap that 1M for the 250k...I will say I like the low end response of the amp as it is.

I am almost done soldering in a 6sn7 octal V1 and a second 12ax7. I hope to report on the initial test by this weekend. I am also adding another filtering stage with a 22uF cap and removing the 5Y3 tube recto. I decided on a 220R for the EL34 cathode but will initially leave in the 470R that's there. I plan to add a 1k5 between the screen and coupling cap, as well. Did anyone try a R in this location yet?

[Berger]

got my kit today, probably the best packing job I've seen. I love the edcor iron!
I'll do an inventory later and let you know if I'm missing anything rj

Aaron

Edit: Kit looks good. I think I'm missing R14 and R15 but I have spares anyways. Any problem with using 1.5k for R15?

Everything is looking good, i got the board made up and hopefully will be doing a bunch of work on it tonight.

Question on tubes. I see you've already tried a KT88,EL34,EL90, and KT66. I'm guessing I should be able to use a 6l6, can I use a 6550?

[Berger]

got my board finished and most of the offboard wiring down. Started putting in the transformers last night. So far only mods are putting a push-pull pot in for the volume control which will bypass the tone stack when pulled.

Not a huge fan of how I have my ground pulled in by the jack, but I can always rewire it later..


Aaron

[RJ Guitars]

got my kit today, probably the best packing job I've seen. I love the edcor iron!
I'll do an inventory later and let you know if I'm missing anything rj

Aaron

Edit: Kit looks good. I think I'm missing R14 and R15 but I have spares anyways. Any problem with using 1.5k for R15?

Everything is looking good, i got the board made up and hopefully will be doing a bunch of work on it tonight.

Question on tubes. I see you've already tried a KT88,EL34,EL90, and KT66. I'm guessing I should be able to use a 6l6, can I use a 6550?

Aaron,

Thanks for the feedback.... R14 and R15 were missing from the Quote Sheet - so thank you, it has been updated.

For R15, I think that is the "Mid" resistor that I have listed at 22K. Let me know if that agrees with how you see things but basically for me I like this to be something greater than 15k. You can actually use a pot if you want to dial in the amount of mid's you'll get. a 25k trim pot is often used but lately I have even experimented with values of 50k and greater. Lemme know if you need a few different values to try and I'll get them off to you ASAP.

The 6550 has similar characteristics to the KT88 and the transformers were specified more than adequately to accommodate all your options. You would be able to use a KT120 if you got the itch.

Thanks for the posts, you are making quick work of this unit. looking forward to the sonic report.

rj

[Berger]

No problem RJ I had some 22k resistors on hand so I used that for now. If you look at the pic I have it going from the left of the push-pull pot to ground. So an easy place to change values if I want to tweak it a bit. I noticed in the kit the trim pot, but no place in the schematic for it. I'm guessing its for the mid resistor like you said in your post?

When switching output tubes are there any mods I need to do? I've never used different output tubes in an amp a side from what it was originally spec'd for.

I'm guessing I'd need to check the voltages to be sure they aren't too high, as well as check the bias. Do I need to change the grid resistor?

Thanks for all your help! If I get time tonight I may get to fire this puppy up. And once its running then I'll start the mods.

Aaron

[RJ Guitars]

No problem RJ I had some 22k resistors on hand so I used that for now. If you look at the pic I have it going from the left of the push-pull pot to ground. So an easy place to change values if I want to tweak it a bit. I noticed in the kit the trim pot, but no place in the schematic for it. I'm guessing its for the mid resistor like you said in your post?

When switching output tubes are there any mods I need to do? I've never used different output tubes in an amp a side from what it was originally spec'd for.

I'm guessing I'd need to check the voltages to be sure they aren't too high, as well as check the bias. Do I need to change the grid resistor?

Thanks for all your help! If I get time tonight I may get to fire this puppy up. And once its running then I'll start the mods.

Aaron

Eventually you want to tweak that amp for the specific tube you are using. Since this is a self biasing amp you have a lot of leeway in tube choices without having to rebias... sooner or later you want to optimize but for testing you can try it. For something like a 6K6gt it might red plate but for the big stuff probably not.

looking forward to the first report of sonic output. I am just about ready to start dialing mine for optimum tone. Maybe get that started this weekend.

rj

[Berger]

finished the amp tonight. Didn't get to play with it too much.
First off it is the quietest amp Ive built so far! I haven't shorten any of the transformer leads but its still very quiet.

I forgot to hook up the negative feedback loop but it sounds good. Plan is to put a pot there to have a 'presence' control.

The pushpull tone stock bypass sounds great and works as advertised. The normal tone controls sound ok. I have the stock .01uf cap in there. I think I'll put to 500pf instead. But I was using my dual emg guitar for testing so that probably not the best guitar for checking.

Oh I was using the hv taps, Ruby EL34, EH 12ax7.

Hopefully I'll get to do some mods in the coming days.

Aaron

[Zippy]

<applause>

Great news, Aaron. I look forward to hearing about your tweaks. I drilled my front panel for a Mid pot - 25k with a 10k tail to ground. I know RJ is talking about MORE MIDS but I think he's got a lil' hearing loss. I'm not worried about him reading this 'cause I think his vision is going too.

Got any Strats around?

[Berger]

Yup I have a strat a tele and a carvin ct4 that I'll do some testing with. I also have 2 7-strings 1 with an emg as well.

I was thinking about a mid pot as well. I'm guessing from your post it doesn't do much?

Aaron

[yowza]

Eventually you want to tweak that amp for the specific tube you are using. Since this is a self biasing amp you have a lot of leeway in tube choices without having to rebias... sooner or later you want to optimize but for testing you can try it. For something like a 6K6gt it might red plate but for the big stuff probably not.

looking forward to the first report of sonic output. I am just about ready to start dialing mine for optimum tone. Maybe get that started this weekend.

rj

RJ It's taken way longer than it should have but I'm almost finished with my Eagle Supre build and the end is finally in sight.

What's the best way to tweak the grid resistor to find the optimum resistor value to use for a given tube, trial and error? Is there a more scientific method than that? I don't have an EL-34 on hand so I'll be trying out both 6V6 and 6L6 tubes. Since it's good to use a nice hefty grid resistor where's a good source to buy different values of the ohmite 10 W resistor you sent me and which values would be good to have on hand for tweaking?

In our offline email correspondence you mentioned something about tweaking the dropping string resistors so I was wondering what the general consensus is on this. What dropping string resistor values is everybody using in their Eagles? Is this also an area to tweak based on which tube is used?


To Zippy, did you ever build your Tweed Eagle, if so how did that turn out? I reread this whole Eagle thread a while back and have been wondering about the tweed Eagle and curious about what you did with that.

Thanks

Ed