LSC
413 posts
May 16, 2013
5:56 PM
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I just acquired a Mergili "One Trick Pony". May have been the only one made. I'm hoping I haven't just found out why.
The problem is the gain is ridiculously hot. With both the tone and the volume turned completely anti-clockwise, i.e. off, yes off, I can barely get the volume control on the mic on when the dreaded feedback rears it's head. I've used Twins, Super Reverbs and all sorts and never experienced anything so touchy. The mic is one of Greg's wood body with a CR. If I turn the amp away from me, facing into the back of a padded chair, and stand several feet away I can play enough to hear that tonewise it has great potential if I can get it to be useable. Sounds like a Zoo on steroids. I've got a Zoo and a SJ Avenger and was hoping this would fill the gap in between.
The amp has an unusual tube line up - 12ay7, 12at7, 2xEL84. I can only guess that the 12ay7 is being used as the rectifier which is something I've not seen before and seems very unusual if that is the case. I'm not much of a tech guy but it seems like just going to a lower gain preamp tube isn't going to be a solution in this case. Can any of you guys possibly point me in the direction of a possible solution please?
On the plus side, I didn't pay a whole lot for it, the cabinet is way cool and overall the amp looks in excellent shape.
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LSC
Last Edited by LSC on May 16, 2013 5:58 PM
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Rick Davis
1818 posts
May 16, 2013
7:25 PM
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It looks very cool.
If those are the only tubes you see I would guess it has a solid state rectifier. The AY7 would be preamp, the AT7 is commonly used for phase inverter, and the EL84s of course are your power tubes.
I'd start with a 12AU7 in V1, but I think this one might require the services of a good tech. Pinching down the input signal -- with an external preamp, for example -- might rob the amp of its tone.
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-Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
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walterharp
1099 posts
May 16, 2013
7:27 PM
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yeah, amp tech, might be as simple as a resistor on the input, or a resistor could be loose somewhere
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Rick Davis
1819 posts
May 16, 2013
7:31 PM
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I like this tube a lot for stuff like this, and it is only $19.95.
NOS Sylvania 5814a Triple Mica
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-Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
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Last Edited by Rick Davis on May 16, 2013 7:34 PM
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LSC
414 posts
May 16, 2013
8:24 PM
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Thanks Rick. I hadn't thought of a SS rectifier. Duh. I'll try a preamp tube swap before I take it to the tech. I've got a NOS Conn branded RCA 12au7 I can try.
I think it will have to take a trip to the amp vet though. Damn power cable is only about three feet long for a start. It hums a bit at idle as well. More than you would expect from a relatively new amp. My go to guys here in town are very good and for what I paid I can afford a service.
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LSC
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eharp
2101 posts
May 16, 2013
9:11 PM
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that is a sweet lookin' amp, though!
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SuperBee
1118 posts
May 16, 2013
9:52 PM
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Mmm...have you tried it with guitar? Got a schematic? Wonder if its designed that way or if it has a problem.
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LSC
415 posts
May 16, 2013
10:33 PM
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Mystery solved. Just got an email from John Mergili. This amp was never meant to be sold. He built the cab for bench tests and trying out some covering techniques. He stuck an amp in it for the hell of it built out of spare parts. He eventually gave it away to a friend who sold it to the guy I got it from. File under, "If it sounds too good to be true it probably is."
Still, John has offered to rectify matters and I may end up with a great harp amp that will fit what I wanted for the tool box. File under, "Clouds and silver linings."
"If I've told you once I've told you a million times, don't speak in cliches and don't exaggerate!"
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LSC
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Greg Heumann
2145 posts
May 17, 2013
7:13 AM
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If it is that hot, you're probably going to need to put 12AU's in BOTH positions. The phase inverter IS a gain stage. At least, I wouldn't be afraid to try that, and don't worry about the tone. If the amp isn't playable......
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/Greg
BlowsMeAway Productions
See my Customer Mics album on Facebook
BlueState - my band
Bluestate on iTunes
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gmacleod15
205 posts
May 17, 2013
7:57 AM
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Nice looking amp!
I am still looking for a style of cab to build and this one caught my eye. Anyone have any experience with this particular style.
I guess my main concern would be the relatively small amount of surface area for the speaker to project through.
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MBH member since 2009-03-24
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HawkeyeKane
1683 posts
May 17, 2013
8:26 AM
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"I've got a NOS Conn branded RCA 12au7 I can try."
Oh really?! I've never seen Conn tubes before! I own two Conn horns, a Frenchie and a cornet. I've always been a fan of their instruments, but I never knew they sold tubes as well.
Very cool amp though LSC. Not many people can say they own a one-of-a-kind amp like that. I'll bet you anything Mergili can revamp that sucker to a nice little compact tone cannon. :-)
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Hawkeye Kane
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LSC
416 posts
May 17, 2013
11:41 AM
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@ Hawkeye - I believe Conn also made organs which is where the tube most likely came from.
Spoke with Mergili this morning. I'll be taking the amp to him tonight. He has doubts as to whether or not he can turn a sows ear into a silk purse but he's going to try. He was pissed that he gave the amp away only to have it sold and then sold again. He is kicking himself for having put his logo and labels on it. Those logos were why I was misled. As he said, "Any guy would have thought the same thing."
The good news is there are some quality parts in there, Kendrick black frame speaker, Hammond OT, all JJ tubes. Unfortunately there are some design flaws, the transformer position causing a 60 cycle hum amongst them.
@Greg- Thanks. I'm not sure if I have two AUs. I'll try the one to see what happens before I take it over to John and two if I have two. As luck would have it he's right in my neighborhood.
Thanks again for your thoughts guys. I just never get caught out buying gear. Kind of pride myself on it. But even the best blow a wrong note once in a while. The trick is to bend it around and call it jazz.
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LSC
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LSC
Last Edited by LSC on May 17, 2013 12:14 PM
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LSC
418 posts
May 17, 2013
12:13 PM
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Found another Conn AU. Using two has helped quite a bit but the volume before feedback is only about equal to my Zoo. I'll wait and see what John can do. If he can get more volume and less hum out of it I can still try and tweak the tone with different brand tubes and/or going to a Weber 10A125 rather than the ceramic Kendrick which is in there now. Then of course I still have the Kinder which I have used to tame the wildest of horses. This pony may avoid getting shot yet.
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LSC
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Rick Davis
1824 posts
May 17, 2013
12:33 PM
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I'd like to hear it.
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-Rick Davis
The Blues Harp Amps Blog
The Mile High Blues Society
Tip Jar
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HawkeyeKane
1684 posts
May 17, 2013
12:57 PM
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I'm with you Rick. I'm really intrigued. If John can pull a rabbit out of his hat, seems to me it could wind up sounding like a Pro Junior.
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Hawkeye Kane
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LSC
419 posts
May 18, 2013
2:57 PM
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Just dropped it off with John. He said until he looks at to remember what he did exactly he can't give me an accurate ETA but asked to be given a couple of weeks so he can get it right. "Lowering the gain is a quick fix but I want it to sound good so it does you proud."
I didn't notice till I put it in the car but it exactly matches the interior vinyl on my El Camino.
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LSC
Last Edited by LSC on May 18, 2013 2:59 PM
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