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Topic: Newcomb E-17 Amplifier |
Charles ONeal
From:
Arizona, USA
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Posted 10 May 2021 9:13 pm |
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I recently got a all original Newcomb E-17 Amplifier in great shape.
It's a two channel 17w mono push pull with variable output impedance.
So far I've only changed out the cord for a 3 prong and soldered temporary wires leading from both the existing rca and 4 prong mic jacks to external 1/4 inch jacks for the inputs.
I've had it set up where I fork my lap steel's output sending an Orange Squeezer and a Sea Blue EQ to Channel 2 (the hotter input) and then have a dirt effects chain going into a volume pedal feeding Channel 1.
With the levels set right I go from a bluesy relatively clean tone to overcoming that with the dirt channel.
It's like a vintage fuzz volume pot cleanup only better. With a mid heavy wah in the dirty chain and contorting with that and the volume pedal... oh my golly.
One thing that I noticed today is that if I put a fuzz face in the front of the dirt chain it Channel 2 sound like a miss biased fuzz even if Channel 1 is turned all the way down on the amp and volume pedal, good to my ears by not the "clean channel that it should be.
I'm thinking that the input impedance might be affecting the tube bias.
The strange thing is that it's only the fuzz face and not other fuzzes and it doesn't matter if there is other pedals following it before it goes to the amp or not.
It's a +9 silicon Fuzz Face and not a -9 PNP.
I'm working on putting together a impedance tester/speaker to line load/pickup simulator unit so I can troubleshoot it while I'm deciding what to do with the amp.
Since it isn't stereo I don't feel bad about modding it.
I'm leaning towards puting on a lower chassis extention, pulling the tone stack and replacing it with a transformer free Poorman's EQP1-A.
If I do that I could use the mic input tube socket for a Channel 1 preamp tube.
I just figured that I'd share the neat set up and am curious if anybody had experience moding the units or and general thoughts on the schematic as it's not quite like any other amp layout I've seen. |
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Dave Zirbel
From:
Sebastopol, CA USA
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Posted 11 May 2021 8:25 am
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Skip Simmons in Northern California does lots of old tube PA conversions for guitarists and harmonica players. He also does a weekly podcast I think.
http://www.skipsimmonsamps.com
Not sure if he'll share his secrets  but I have a couple of his Newcombs and they are great. He usually wires them as a dual channel amp but only having one instrument input, and having a couple of blend pots that are voiced a little different. You can simply dial in one or the other, or blend them. I'm not a tech so I really can't help you much.
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Dave Zirbel-
Sierra S-10 (Built by Ross Shafer),ZB, Fender 400 guitars, various tube and SS amps
Last edited by Dave Zirbel on 12 May 2021 1:51 pm; edited 1 time in total |
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Charles ONeal
From:
Arizona, USA
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Posted 12 May 2021 8:53 am
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Thanks for the referral Dave.
I just looked at his website.
I'd prefer to work on it myself. I've made all my pedals other than my wah and volume pedal, so it's a natural evolution to step up the voltage and work on the amp.
The Newcomb's design is a wonderful introduction to tube theory being similar in topology to many revered guitar amps but being seemly unique in how the preamp has the negative feedback loop and is self biased.
Looks like I should get ahold of him and see if I can a bit of general advise along with a parts kit, tubes to roll or something that makes it worth his time so I'm not just a bother. |
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