63 Ampeg super echo twin 2?

[Toxophilite]

Anyone try or have one of these amps
One's come up locally for under a million $$ and I was curious

[Toxophilite]

Anybody?


I guess as I'm mostly familiar with fender Ab763 amps and later UL amps.
I was curious how the Ampegs compare in the clean department.Not necessarily how much clean headroom but what their basic sound is like. I know they have one knob EQ.
I don't now anyone with one and unfortunately the one i was looking at is several hours (like 9!!) drive away.
It is selling for a decent price though considering.

i also thought it might a neat idea for a build if it's something i thought i could get a sound i would like out of.

So if anyone has any  knowledge. experience and or comparative information about these amps i'd appreciate.
Thanks

[shooter]

I fixed one a couple years ago, what a beautiful nightmare!!!!
get the re-drawn schematic, for starts.  the amp I fixed had multiple minor problems, the major one was a blown OT, but not the easy, look it's open type, you had to play for awhile, get things warmed up, then one side would start tube arcing.  Per owners request I re-tubed, new OT but with 6V6 on "the bad" side, the amp had 7868's(?).  the amp sounded nice, trem n verb were less pronounced than the twins I've worked on, loud factor was not the same either, she was a loud amp though, I felt it was "butteryer" than the starker twin. weight was PIG like a twin.  If you get lost in tangled wires and difficult schematics and small space, this is the amp for you

[92Volts]

Doug's schematic library has the Super Echo Twin but not the 2... http://el34world.com/charts/Schematics/files/ampeg/Ampeg_SuperEchoTwin.pdf

I worked on an Ampeg of a similar era, a G-12 Gemini I, which is meaningfully different from the G-15 Gemini II and every schematic labelled G-12 I could find! In other words, don't assume the schematic I linked is correct.

With that said, I wouldn't worry, 6CG7s, 7868s, and 7591s are back in production so there aren't many potential surprises with this amp. Worst-case scenario is that it needs 7199 tubes, but preamp tubes don't need replacement often.

I was surprised to find the Gemini (65 or 67 IIRC) was built on a PCB, but it was relatively spacious and heavy/durable so it wasn't too bad to work with.

It should sound good. Looks like these are true stereo amps which could be really interesting-- but not the same as a Fender Twin for example.

[Toxophilite]

That's the one. I should have said Ampeg super echo twin ET-2


This is the later version with SS rectification(which I prefer) and 7591 output tubes
 The amp itself is supposed to be in good working condition but the cab has definitely been retolexed in standard fender black and it has Marsland speakers in it..ick. Easy enough to swap out.


Specs say 15 watts a side in stereo and 30 mon
weighs about 48lbs so like a SF vibrolux


I know they're nowhere near a twin in volume, probably closer to a pro or vibrolux in mono
I'd be using it in stereo


Shooter says more buttery than Fender
Any other opinions?

[shooter]

This is the later version with SS rectification(which I prefer) and 7591 output tubes

that's it, the one I fixed, like I said, since one side was bad the owner wanted 6V6 to "hear" if he liked the combination, he did, played for almost an hour before he settled up with me

[Toxophilite]

This is the later version with SS rectification(which I prefer) and 7591 output tubes

that's it, the one I fixed, like I said, since one side was bad the owner wanted 6V6 to "hear" if he liked the combination, he did, played for almost an hour before he settled up with me

Whew! An hour! I hope he was good player and the job paid well. You're more tolerant than I am!


The seller of this amp claims the cleans are a like a fender tweed?? which somehow doesn't sound quite right.

[Toxophilite]

Do you think $1000 Can(about $800 US)  is too steep for one of these in good working condition considering it's re-tolexed and has replacement speakers

[DummyLoad]

Do you think $1000 Can(about $800 US)  is too steep for one of these in good working condition considering it's re-tolexed and has replacement speakers

that would not be out of line if the transformers and speakers are working and original and it has not been modified. the tolex not being original has impact on value. one in near new condition sold or reveb.com for 1500USD. there's one for 1925USD that still up for sale, it's in decent shape, but not worth 2K. it has been listed for 8 months.

i'd offer 600-700USD if i really had to have one. 
 
--pete

[Toxophilite]

oops looks like someone is willing to pay the asking price of $1200 Can  ($920 US) They have a fiend who can pick it up and won't have to pay shipping like me. So unless they bail I'm out of the running on this amp.

[Toxophilite]

Oh the other seller didn't buy it and it looks like I did!!
Should arrive sometimes next week

[Toxophilite]

Looking at the schematic of the super echo twin
There's two inputs for each amp and a stereo input that taps into two of them


I was understanding that there was a guitar and an accordion input on each channel with the accordion input having higher gain.
 
Looking at the schematic I see two inputs that are also hooked to the stereo input These seem to have 5.6 meg resistors to ground and 120k resistors into the preamp tube. To me these are likely the accordion inputs as it seems they'd be really high gain with the 5.6 meg to ground and I believe the stereo input was designed for an ampeg accordion pickup.


The other ones, with the 120k into the preamp tube and what looks like a switch disconnecting the 5.6meg resistor to ground (??) would seem like the guitar inputs.
Would this be right?


I'm just trying to wrap my head around the many options this amp has going on...I guess i could just wait till it arrives but I figure wrapping my head around it's Rubix cube of a schematic wouldn't hurt.


I would be cool to be able to put a dry signal into both amps and a wet into just one side. seems like you'd have to modify it to do that or have a splitter somewhere in your chain.


i guess the modest output figures for  a pair of 7591s (potentially 40 watts) is about achieving the nicest clean sound.

[davidwpack]

Both of my Ampeg B25-B heads have 5.6 M on the inputs.

[Toxophilite]

THis amp should arrive within the week and of course I'm going to play around with it a lot to find out if I like it and if I can get sound out of it as is. I might try a speaker swap if the Marslands aren't doing it for me.
One thing that concerns me though is the on know EQ. Looks like half a baxandall.
Anyone have experience with these in these amps
I've looked at Geminis etc and a lot of them at least seem to have a full baxandall circuit with is certainly more versatile.


I was considering modding one channel if it looks like I'd need to
 though I imagine there would be more insertion loss
The amp isn't a collectors piece
i was curious if anyone else here has done any modifying of old Ampegs
Just curious at this point

[Toxophilite]

Interestly people seem to claim these are two reverb rockets in one amp
Though the PI and pre of both are obviously different.
And the RR has a 2 band EQ

[Toxophilite]

Can someone help me understand the tone control on this amp
is it just half a baxandall?
Has anyone any experence with it?
If I could get a stacked 500k pot would putting a full baxandall in be a disaster?

[sluckey]

I suppose you could call it a half baxandall. My Fender Harvard 5F10 has that same circuit but the cap values are different. The Princeton 5F2A and Vibrolux 5F11 also use the same circuit. The cap ratio is still 10:1 just like the Ampeg. And my Ampeg J12B uses that same circuit. It's just a simple but effective one knob tone control. Turn it down and it's a simple bass cut. Turn it the other way and it's a treble boost just like a bright cap on the volume control.

Why not just wait until you actually get the amp before you modify it. You may just be happy with it as is. Then again, you may have to concentrate on fixing something that's broke.

[Toxophilite]

Thanks
I'll definitely check it out when it arrives. I'd rather not mess with anything if I don't have too.
I've just never encountered a one knob tine control I've been really happy with but who knows?
i was also just curious about it.

[sluckey]

Take some good gut shot pics when you get it. I'd love to see the inside of that amp.

[shooter]

gut shot pics

here's the one I worked on for comparison

[Toxophilite]

And an actual schematic (not from my amp but the same configuration and obviously pulled from a cabinet) I like how it has the voltages. I will pos the one actually in my amp when it arrives if it's any different.

[shooter]

here's a re-draw by joe piazza, came in VERY handy

[Toxophilite]

I had read somewhere that some of his drawings seem to have mistakes,I don't know this from personal experience though.
This one looks good.

Thanks!

[shooter]

This one looks good.

he's among 6-7 re-drawers I trust, most of the others live here
ALWAYS have an original though

[sluckey]

When you draw as many schematics as Joe has you're bound to release some gremlins. Fender has certainly released quite a few. Me too! 

[Toxophilite]

So this beast arrived today in one piece
Obviously retolexed but the amp itself looks to be in decent shape
Obviously there's been some cap work (brown blobby guys)


One thing perplexes me
Channel one seems to be much louder than channel 2 and it comes through both speakers
Channel 2 is much much quieter (channle 2 - 10 =channel 1 - 4) and only comes through one speaker


Is it supposed to be that way


I had though that both channels were separate however the switching jacks on the schematic confuse me


Does Channel one default to 30 watts mono?


I did test the channel 2 tubes and found that the PI 6SL7 was pretty weak so I replaced it with one i had. No difference
the other tubes test good except one of the power tubes was very microphonic

[Toxophilite]

Anyone have one of these or can tell me how the two channel arrangement works
I know verb is in one side and tremelo is in the other
and there's a switch which you can basically switch channel two to the left side
Here's what I can figure out
Channel - 1 goes to both amps/speakers, verb is just in channel 2speaker  trem just in channel one(maybe a hint in channel 2)


channel 2 - just goes to the channel 2 speaker/amp, when you flip the switch it seems to go to channel 1 and gives you the same basic arrangement as channel one


Using the stereo jack gives you the same sort of situation basically.


Actually I quite like how it's setup. i quite like the reverb and the tremelo. When I build my own stereo amp i think I'll steal some of this arrangement. I just don't care for the lack of EQ control.


I'd be tempted to get a stacked concentric 500k pot and build a full baxandall into at least channel one


 Still have to try it loud though and see how it works then. obviously the volume and tone controls interact alot.

[shooter]

One thing perplexes me

you're doing well then

If you paid $'s for it, I'd highly recommend the JJ caps for the cans and whatever floats your boat for the other ecaps.  I found 1 ch bleeding 5+vdc on a least 2 couplers around the PI.  I also believe the one I fixed dialed in close on all the original dcv.  Notes say I just replaced all the jacks, and 2 sockets, besides all the ecaps couple tubes, OT, think that's the highlight reel, have fun, I did

[sluckey]

What is the labeling for the toggle switch above the input jacks?

[Toxophilite]

it's
echo/vibrato channel one only
or
echo vibrato channel one and two


However you never really seem to get vibrato in channel 2


Shooter how do you test for leaky caps
I only have a digital multimeter. it can test capacitance but not leakage
I do have a scope but very little experience with it and NO formal electronics background.


and yes more than one thing perplexes me!!


for example why does it have such a big cabinet. It probably has about 10 lbs too much of just cabinet!

[shooter]

how do you test for leaky caps

all the ecaps I removed, no testing required, well age
the coupling caps, when I measured 5+dc volts where none should, I replaced them.

they had to build a large cabinet to celebrate the fact they got 10lbs of S^%&T it a 5lb chassis

[Toxophilite]

I take you have a tester for cap leakage
Something like this?
http://www.facstaff.bucknell.edu/esantane/restoration/captester.html


i'm not getting ANY hum at all I was going to deal with all the small Ecaps
I'm not even sure if I'm going to keep this beast


Humourously that chassis looks like on of my builds! I didn't think it looked very cramped, lot's of room!
However if I was more into the basic sound of the amp, I would probably transplant the whole deal into a reasonable sized cabinet and make it a fair bit lighter and less %$%$ bulky

[sluckey]

You don't need any special test equipment to test for coupling cap leakage. Usually, getting a good set of voltage readings for all tube pins will reveal if you need to test for leakage. A bad grid voltage is a good indicator for leakage test. If you have a couple positive volts on a grid that should read zero volts, do the test. If you have -10v on a grid that should have -40v, do the test.

The test... Disconnect the end of the cap that is connected to the lowest voltage (usually the grid end of a coupling cap). The other end of the cap will usually still be connected to a previous tube plate. Connect your DVM to the dangling end of the cap and chassis ground. If you measure anything above a few tenths of a volt, replace the cap because it is leaky. The more leaky a cap is, the higher the voltage will be. If a cap is shorted, it has maximum leakage and the voltage may even be up in the B+ range.

 

[Toxophilite]

Thanks very much. That will very useful!


I tried the amp out today at volume. A/B ing it with a vibrolux reverb build just to compare it with something I'm familiar with.
I tried many combinations of volume and tone and I tried both inputs (accordian and guitar)

As is I found it to be very mid heavy and lacking in bass a little. the top end was actually very pretty.


I have a Boss GE-7 EQ pedal that I use as a clean boost so I tried scooping some mids to see how it sounded.
I got a sound I liked a lot but I had to adjust


200hz   +2.5 db
400hz    -4 db
800hz    -10db!
1.6khz   - 5db
6.4k hz  +1.5


and then I had the boost up about 5 db


Then it sounded quite lovely. If only it had a built in 7 band EQ!!!
Adjusted that way it reminded me of the sherwood mono hifi I had that had 7591 output tubes(40 watts) that I put a Ab763 tone stack in front of. It was also in a 2 x 12 cab


So many factors
Could be the 7591 output tubes,
could be the 2 x 12" speakers
Could be the ampeg circuit

[Toxophilite]

Oh and the schematic basically has the main B+ plate voltages for each tube
THough it does also show a voltage of 23 volts for pin 5 of the both power tubes
On one channel measure 14.5 on pin 5 of both 7591 tubes and the other channel is around 13.5 on each tube

Seems wrong!

[shooter]

Seems wrong!

13.5/14.5*100 says you're 93% balanced after 55yrs

I swapped the PS caps as PM's (preventive maintenance).  I don't like amps coming back in less than a year.

[Toxophilite]

Fair enough but the schematic I have reads 23v on Pin 5
I seem to be reading quite a bit lower
Am I misinterpreting this?


My B+ voltages are all pretty good


The other thing is that the newish (brown) caps are all in the tremelo circuit and instead of being .05 (or.0470) they're all .03
What would that do to the tremelo?

[sluckey]

THough it does also show a voltage of 23 volts for pin 5 of the both power tubes
On one channel measure 14.5 on pin 5 of both 7591 tubes and the other channel is around 13.5 on each tube

Tack a 22µF cap across the 140Ω cathode resistor. Does the voltage go up. If not, you probably just have some weak 7591s. Good time to order a quad.

     https://www.tubesandmore.com/search/node/7591

Smaller caps in the tremolo would increase the speed of the tremolo oscillator.

[Toxophilite]

Duh
I forgot about how the tubes affect the bias
I should remember having to adjust the bias for many different sets of 6V6 and 6L6 on my deluxe reverb and vibrolux reverb builds
Thanks for reminding me!!


Looks like both sets are weak..funny though because  the channel two set is actually a set I put in that are from a Hammond AO-63 as one of the originals was pretty microphonic


Any ideas on the tremelo and have the sub of .03 caps for the 3  .05 caps will affect it?

[sluckey]

read my post.

[Toxophilite]

Right. Not sure how i missed that. I usually am I good reader. It's pretty well 25% of what I do. READ!That sounds right too as the tremelo on this amp is pretty fast and doesn't get very slow.

[Toxophilite]

I wonder if there's a non-invasive way (meaning no more holes drilled in the chassis) I can build a big mid scoop into the tone stack of one channel? Maybe centred around 800hz

[Toxophilite]

Because I'm rash and impetuous I found this simple mid control online (out of a Framus cobra) and I've clipped it in after the volume control of channel one and before it hits the 270 k resistor
(I just noticed the Framus cobra has it prior to treble/bass tone stack and gain control so maybe I'll try it prior to the tone stack next to see which I prefer or if there's a big difference)

Frankly both the original and  the redraw schematic are pretty &^%*& confusing
The original has channel on on the right and channel 2 on the left
The redraw has the right side speaker called speaker 2 and the left side is called speaker 1


It's like a maze trying to follow the signal with an occasional game of snakes and ladders thrown in!


Anyway I plan to see how this works in the morning when I can actually play guitar though an amp, albeit quietly
If it does...well I don't really need that stereo jack meant for accordions anyway...

[sluckey]

I like your idea of using a James tone control with dual concentric pots. I like the sound of the James in the Gemini II amps. Not as mid-scooped as a BF Fender, but a big improvement over the one knob tone control.

[shooter]

It's like a maze trying to follow the signal

that amp was well designed for ADD techs, if you're OCD, sell IT!

[Toxophilite]

Oh heck! I'm not up on my TLA's

It's like a maze trying to follow the signal

that amp was well designed for ADD techs, if you're OCD, sell IT!

[Toxophilite]

I use the James alot when I was doing Roberts/Akai reel to reel preamp/amp conversions. It works well. Quite versatile.
I just wish there was a local source for dual concentric pots locally and I didn't have to wait ^%*&^ two weeks! to have a couple shipped to me. I have one but it's 2meg and and 1 meg. Can I tweak the cap values and use it> (maybe half one set of values?) (Guessing!!)

I like your idea of using a James tone control with dual concentric pots. I like the sound of the James in the Gemini II amps. Not as mid-scooped as a BF Fender, but a big improvement over the one knob tone control.

[SILVERGUN]

I use the James alot when I was doing Roberts/Akai reel to reel preamp/amp conversions. It works well. Quite versatile.
I just wish there was a local source for dual concentric pots locally and I didn't have to wait ^%*&^ two weeks! to have a couple shipped to me. I have one but it's 2meg and and 1 meg. Can I tweak the cap values and use it> (maybe half one set of values?) (Guessing!!)

I like your idea of using a James tone control with dual concentric pots. I like the sound of the James in the Gemini II amps. Not as mid-scooped as a BF Fender, but a big improvement over the one knob tone control.

As a general tip, you can always strap a resistor across the 2 outer lugs of a pot to make it into a lower value pot.
Use a parallel resistor calculator:
http://www.sengpielaudio.com/calculator-paralresist.htm

[Toxophilite]

I use the James alot when I was doing Roberts/Akai reel to reel preamp/amp conversions. It works well. Quite versatile.
I just wish there was a local source for dual concentric pots locally and I didn't have to wait ^%*&^ two weeks! to have a couple shipped to me. I have one but it's 2meg and and 1 meg. Can I tweak the cap values and use it> (maybe half one set of values?) (Guessing!!)

I like your idea of using a James tone control with dual concentric pots. I like the sound of the James in the Gemini II amps. Not as mid-scooped as a BF Fender, but a big improvement over the one knob tone control.

As a general tip, you can always strap a resistor across the 2 outer lugs of a pot to make it into a lower value pot.
Use a parallel resistor calculator:
http://www.sengpielaudio.com/calculator-paralresist.htm

Another duh moment for me!!  thanks for the reminder. Headache day! My excuse is a slow befuddled brain.

[Toxophilite]

Next $10,000 question/questions


On the gemini the volume is between the 1st and second gain stage and the tone stack is between the 2nd gain stage and the PI


On the super echo twin the volume  and the tone stack are paired after the first gain stage
The signal comes out of the 1st gain stage and goes into the wiper of the tone pot and the top of the volume control simultaneously


To make this easier to bring back to stock if necessary I'm going to pull the original volume and tone stack intact as they are very interconnected with caps etc.


I have another 1 meg pot to use for the volume and I have my James all wired up.


How would I best implement this?


Into the tone stack from the 1st gain stage and then into the volume control and then into the PI? (or the 2 x  270k resistors that actually take channel one into both PIs)

or visa versa?