My PA turned Guitar amp conversion is almost done

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zepman

zepman

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I yanked this early 60's vintage(from what I can find on the internet) PA from a Church before they Demolished it. I also got some killer old JBL 12" speakers BUT the real treat is that not to long after I scored this, I read in an old Guitar Players magazine under "pawnshop Prize" about how great these sound as guitar amps.

newcombh25.jpg


Here is the article as published :
COPYRIGHT 2004 Miller Freeman Publications

Newcomb's tube-powered public-address systems were as common a fixture as the water cooler in offices and factories during the '50s and '60s. And though it's hard to guess how many HLP-14 (14 watt) and H-25 (25 watt) amps (as well as other models) were produced before the Hollywood-based company laid down its soldering guns in 1982, judging by the extremely low prices these units have traditionally commanded at local ham-radio fests--we're talking as little as $20 a pop--Newcomb and crew must have cranked out quite a few.

The H-25 shown here is one of the many now being offered to guitar players for prices starting around $200. It has been retrofitted with 1/4" jacks for the three channel inputs and the speaker output, and the original jumper-style impedance selector can accommodate common 4 [ohm], 8 [ohm], and 16 [ohm] loads.

In classic hi-fi fashion, the H-25 features a point-to-point-wired circuit that uses no boards or terminal strips. Its tube complement consists of two 6L6s, a 5U4G rectifier, and a bevy of vintage, octal-based preamp tubes: three metal-can 6SF5 hi-mu triodes, a 6SN7 dual triode, and a 6S17 pentode.

With its twin pilot lights, louvered metal hood, curved handles leach with a chrome center strip), and large, cream-colored knobs, the H-25 is a relic of the "golden age" of vacuum tubes. And what a cool hillbilly guitar amp this is for recording, rehearsals, or low-volume gigs. Channels 1 and 2 deliver respectable clean and overdrive tones that are in the sonic ball-park of a Fender tweed Deluxe, while Channel 3 is lower gain and less exciting. Pummeled with humbuckers and single-coils, the H-25 kicks out distortion tones that are toothy and bad, with a fuzzy midrange snarl mad plenty of low-end girth. The dynamic qualities of the amp allow you to get happening clean tones when you turn down your guitar, and the Bass and Treble controls have plenty of range to compensate for brighter- or darker-sounding instruments.

Though Newcombs aren't as underground and inexpensive as they once were, they're still pretty impressive deals. It would probably cost a couple of grand to produce a similar hand-wired amp these days, and you still wouldn't get all the nifty accoutrements that make the H-25 such a hip thing to own. And as anything hip always goes up in price, get yours before they start costing what they're really worth.
Amp courtesy of Jude Gold.


It is in greatshape, I just cleaned it really well and retubed it (Thanks Doug!!! @ http://www.dougstubes.com)
fronttubes.jpg.w560h420.jpg


And all I have left to do is install a couple of 1/4 inch inputs and we will have clippage :rock:
newcombbacktubes.jpg


I will try to get her done tomorrow night :thumbsup: What do you guys think? Kinda cool lookin mutha huh and built like a tank :gethim: I REALLY hope it does sound like a Fender Tweed deluxe if so I just found my "clean" tone amp in a trashcan
:D
 
That's kool! I have a Haldorson amp with a similar tube layout. It's metal, green, and has chicken knobs. It has a nice rumble. Probably needs new caps. It came with two RCA fat short bottle 6l6 tubes.
 
Beforetone":9c6cc said:
That's kool! I have a Haldorson amp with a similar tube layout. It's metal, green, and has chicken knobs. It has a nice rumble. Probably needs new caps. It came with two RCA fat short bottle 6l6 tubes.
Is the Halderson a PA also? How many watts?Pics?..................John :)
 
I got an old PA amp out in the garage myself. Want to do the same thing but have no idea what circuit to put in it. I'll try and get some pics of it and post them later on.
 
i learned to play guitar out of an old PA head like that. it was a Bogen. i had that and one of those red dod distortion pedals. oh the tones that came out of that rig :yes:
 
RaceU4her":31005 said:
i learned to play guitar out of an old PA head like that. it was a Bogen. i had that and one of those red dod distortion pedals. oh the tones that came out of that rig :yes:
Wow, your making me anxious to get this thing done so I can hear what I got :thumbsup: Do you still have the "Bogen"?.......John :)
 
tweed":31c5e said:
I got an old PA amp out in the garage myself. Want to do the same thing but have no idea what circuit to put in it. I'll try and get some pics of it and post them later on.
Randy, I was just going to pigtail the 1/4 inch inputs into the mic input circuit for each channel :confused: is there a better way of doing it?? :)
 
zepman":30357 said:
tweed":30357 said:
I got an old PA amp out in the garage myself. Want to do the same thing but have no idea what circuit to put in it. I'll try and get some pics of it and post them later on.
Randy, I was just going to pigtail the 1/4 inch inputs into the mic input circuit for each channel :confused: is there a better way of doing it?? :)


You are asking the wrong person lol. I am teh n00b when it comes to wiring guitar amps. I know a resistor/capacitor poped in mine last time it was played. It did sound righteous though. Its just sitting in the garage now. I'll have to blow the dust off it when I have time and shoot you some pics. Im flying to SD tomorrow so it will have to wait till sometime next week.
 
Here she is sitting on an Avatar "Bluesbreaker" Cab :rock: She looks like she needs her inputs installed so we can hear her voice huh???? :lol: :LOL:
newcomb.jpg
 
i may have some 6sn7's laying around if you're ever in need. nice score btw. :thumbsup:
 
are the inputs balanced? it looks that way to me. i'd probably just get barrel converters and do it the easy way.. but that's just me.
 
1big1":3bb15 said:
i may have some 6sn7's laying around if you're ever in need. nice score btw. :thumbsup:
Thanks Bro, VERY cool of you. I will let you know if the ones in there dont work. They are the only tubes I didnt replace :rock:
 
1big1":7fafe said:
are the inputs balanced? it looks that way to me. i'd probably just get barrel converters and do it the easy way.. but that's just me.
Damn good idea, I never thought of that. I think I will try those and see if I like the tone enough to invest any more time. Where is a good place to get the converters online?......John
 
i'll check to make sure i have a 6sn7 or 6sl7 in my box of old tubes. i also have some of those black thing-a-ma-jigs laying around. as long as the numbers match what i have it should be good.
as far as barrel converters? i'd probably try whirlwind. i know they make -20 db barrel pads etc.. so i'd start there. alot of times i'll just google stuff like that and get a plethora of responses. radio scrap also probably carries barrel converters.. if you're not opposed to something that isn't necessarily first quality but will get the job done.
 
That is the coolest thing ever. I actually dig those retro cosmetics too! Cant wait to hear it. And from the description it sounds like something Id like!
 
i have three 6sn7's that test good on my herald tube tester. they are 1) u.s.a. yellow label sylvania with black plates and top getter 2) u.s. made g.e. grey plate with side getter and 3) u.s. made admiral with grey plates and side getter. the sylvania and g.e. are 6sn7 gtb's and the admiral is similar in design to the g.e. but is labeled as a gta. you'd probably have check an rca tube guide or duncan's amp page to determine the difference between the gta and the gtb.
another really cool thing to do with those amps is to swap out different brands of rectifier tubes as it can change the compression and sag characteristics slightly. it's not a bad idea to have a couple of rectifier tubes on hand anyway.. since they take the most abuse and are more prone to failure than other tubes.
 
Telephant":63ecf said:
That is the coolest thing ever. I actually dig those retro cosmetics too! Cant wait to hear it. And from the description it sounds like something Id like!
Be sure to come over next year at NAMM again and you can play the little beast :thumbsup: It was great having you last year bro and this year I have my health back SO be READY to party :rock: ....John
 
Damn, I'd LOVE to have something like that at home.

I'm hoping to make it to NAMM this year ( could use a pass *hint*), perhaps I'll drop by Zepfest, if I'm invited of corse. Wouldn't want to impose, by any means.
 
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