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5F1 vs. 5C1???

imwjl
December 21st, 2008, 11:44 AM
Hi,

I'm wondering about the search here again. I didn't get anything searching 5F1 and 5C1, but open google searches got a TDPRI link.

Anybody know or compare these hands on? I thought the 5C1 was more prone toward gain based on the Weber site description of "This is a real grinder with the octal pentode 6SJ7 preamp." but somebody I know who built one didn't think it was too or very prone to distortion.

I am trying to decide which kit/type of amp to order and build.

I generally like blackface tone if that makes a difference but have been thinking about getting something with a personality different than my blackface amps (I have DRRI and PRRI).

Thank you.

muchxs
December 21st, 2008, 12:09 PM
If you really want the definitive answer build a "Champ" with both 5C1 (grid leak bias 6SJ7) pentode front end and 5F1 (cathode biased 12AX7) triode front end dumping into the same SE PA section. Then you'll know.

I'd build it on a 5F2 chassis because the tweed Princeton chassis is easily roomy enough for another octal socket. Or build it on a 5C3 chassis, that gives you four inputs (two per channel), volume/volume/tone. Use an octal to mini adapter for the extra socket.

Yes, I know. Neither the 5C1 nor the 5F1 has a tone control. Just about everyone wants a tone control. Just in case you want to know what a 5C1 sounds like with a tone control...

Oh yeah, use a 125ESE OT for a choice of one or two PA tubes SE.

EuropaChris
December 21st, 2008, 12:30 PM
I built a 5C1 as my first DIY as I have a soft spot for 6SJ7s. I modified the circuit slightly to make it cathode biased rather than grid leak biased, but it's basically the same. It sounds very nice into an Eminence 10" alnico (blue frame) speaker, but I wouldn't call it a gain monster. It's very touch-sensitive, so you can easily control the breakup from the guitar, but I don't think it compares to the nastiness of the 5F1 circuit cranked. It obviously depends on the pickup output, also. But for old-school blues, it's absolutely perfect. Indeed, it's raw and loose, and a lot of fun to play. It's the cream tolex amp in the picture.

My second project was an early 50's Gibson GA-20 based amp, also with the 6SJ7 preamp. It sounds very similar to the 5C1, but it does have quite a bit more gain due to the phase inverter adding it's helping of gain along with the 6SJ7. Everyone who's played it goes ga-ga over it. Sort of a one-trick pony also, but what a fine trick it is! http://lh5.ggpht.com/_8XqhIZ7TQCA/SKtmdT4MtnI/AAAAAAAAAEM/KlQZAugB7NI/s800/DSC02231.JPG

ruger9
December 21st, 2008, 02:04 PM
Any soundclips fellas?

imwjl
December 21st, 2008, 03:03 PM
I built a 5C1 as my first DIY as I have a soft spot for 6SJ7s. I modified the circuit slightly to make it cathode biased rather than grid leak biased, but it's basically the same. It sounds very nice into an Eminence 10" alnico (blue frame) speaker, but I wouldn't call it a gain monster. It's very touch-sensitive, so you can easily control the breakup from the guitar, but I don't think it compares to the nastiness of the 5F1 circuit cranked. It obviously depends on the pickup output, also. But for old-school blues, it's absolutely perfect. Indeed, it's raw and loose, and a lot of fun to play. It's the cream tolex amp in the picture.

My second project was an early 50's Gibson GA-20 based amp, also with the 6SJ7 preamp. It sounds very similar to the 5C1, but it does have quite a bit more gain due to the phase inverter adding it's helping of gain along with the 6SJ7. Everyone who's played it goes ga-ga over it. Sort of a one-trick pony also, but what a fine trick it is! http://lh5.ggpht.com/_8XqhIZ7TQCA/SKtmdT4MtnI/AAAAAAAAAEM/KlQZAugB7NI/s800/DSC02231.JPG

Thank you. Where did you source your parts and that burgundy cabinet?

So do I understand that the 5F1 is more distorted at higher volumes and the 5C1 tops shy of that? I want small size and not so much distortion that I'll be chased downstairs where my bigger amps are.

OTOH it seems like this DIY is as additive as many things in life so I've thought about the cab and head route, but the 8" speaker Champ-type cabs will sit on my desk.

Thanks again.

EuropaChris
December 21st, 2008, 05:46 PM
Thank you. Where did you source your parts and that burgundy cabinet?

So do I understand that the 5F1 is more distorted at higher volumes and the 5C1 tops shy of that? I want small size and not so much distortion that I'll be chased downstairs where my bigger amps are.

OTOH it seems like this DIY is as additive as many things in life so I've thought about the cab and head route, but the 8" speaker Champ-type cabs will sit on my desk.

Thanks again.

The amp (both of them, actually) is scratch built. Finger jointed pine for the cabinet and the raw chassis for the GA-20 from Komboking (http://www.komboking.worldbreak.com/index.html), but it doesn't look like he's making chassis at the moment. The 5C1 just used a Bud aluminum box for the chassis. The 5C1 used trannies I had laying around that came out of some sort of Sony tube reel-to-reel, I believe - nice beefy power transformer and 5k primary outputs. The GA-20 has custom Electra-Print Audio Co. transformers.

The burgundy tolex came from Vibroworld.com (http://www.vibroworld.com/parts/tech11.html#fabric2). I've had two different versions of it, one is more an elephant style, nice and heavy, the other is a more thin, grainy material. I think the Burgandy Crush is the thinner one, and the Wine Taurus is the nice one. Grill cloth is just standard Fender stuff, wheat for the GA-20 and oxblood for the 5C1.

I did have a custom faceplate and nameplate laser etched out of champagne (gold) Alumamark for the GA-20. It really adds the classy touch to the amp rather than rub-on lettering, etc.

Cabinet dimensions are I believe tweed Princeton for the 5C1 and tweed Deluxe for the GA-20. I really like the tweed style cabinet, narrow panel in particular, even if I'm not building a Fender circuit in it. It just works, it's easy to build, and makes servicing and tweaking the amp a snap.

That said, NEITHER of these amps is particularly "home" friendly if you want to turn them up. 5 watts for the 5C1 is loud as heck, and the 12 watts from the GA-20 is just insanely loud at home if cranked. But, if you can live with a big, round, warm tone at lower levels, and maybe a hint of grit, either will be great. With decent parts and transformers, and a matching alnico speaker, these amps will breathe, shimmer, moan, and bark. Every nuance comes through due to the low parts count - there's not much in there to screw up the tone.

If you want to crank it up and be the dirt-monster - build one of these: Moonlight amp (http://picasaweb.google.com/cbeck69/Moonlight?authkey=5qEJw0DwMac&feat=directlink) http://lh4.ggpht.com/_8XqhIZ7TQCA/STRrDNfvbEI/AAAAAAAAAOk/4Ob3WIYeF9c/s400/P1010033.JPG I recently finished it up using yet more junkbox parts, and another Bud box, burgandy tolex and grill cloth. Speaker is a Weber Sig 8S. Clean headroom is about zip except at a whisper, but it will do some great old-school distortion for blues or classic rock. I'm not sure of the cause, but it's a darker amp than either of the other two. Could be the cheap Allied output tranny, maybe just the circuit EQ, but it sounds great cranked up because that darkness keeps out any harshness. Even still, it's pretty darn loud.

Fun stuff!

Chris

Architect
January 20th, 2009, 11:51 AM
I have an old magnatone Varsity amp which is basically a 5c1 circuit. I agree this amp is either the "tone grinder" weber describes, however it it a killer little amp. The gain is just enough and sounds wonderful to my ears. The amp is very touch sensitive and open sounding. I picked the amp up off ebay for $125, add $35 for upgrading the stock speaker to a weber sig8s (plus any upgrades in tubes, I'd rec the coke bottle mazda 5y3)and for $155 you have a great vintage amp.

JohnnyCrash
January 20th, 2009, 12:00 PM
Here's something I learned myself.

Build a 5F1 without the preamp cathode bypass cap (like it is supposed to be, and is on all original layouts and schematics) for a cleaner Champ. Add a bright cap across the volume pot to brighten it up at low volumes.

The overdrive is thicker and creamier without it, and it's a much less gainy overdrive. Put the bypass (and bright cap) in on switches to have both options. I put a second bypass on the preamp via a switch and switch both bypasses in/out as well as the bright cap when both bypasses are out.

Honestly though, you can't beat a BF/SF Champ. The tonestack helps and they're pretty much as gainy as any other Champ circuit.

imwjl
January 20th, 2009, 12:09 PM
Here's something I learned myself.

Build a 5F1 without the preamp cathode bypass cap (like it is supposed to be, and is on all original layouts and schematics) for a cleaner Champ. Add a bright cap across the volume pot to brighten it up at low volumes.

The overdrive is thicker and creamier without it, and it's a much less gainy overdrive. Put the bypass (and bright cap) in on switches to have both options. I put a second bypass on the preamp via a switch and switch both bypasses in/out as well as the bright cap when both bypasses are out.

Honestly though, you can't beat a BF/SF Champ. The tonestack helps and they're pretty much as gainy as any other Champ circuit.

Thanks.

It's too late for the moment. I've ordered a Guytronix kit with .5 => 2 watt and tone options.

I'll have to remember all of this for a future build and now twist the thread to a what speaker or cab topic he he he...

Thanks again.

loosecounty
January 12th, 2010, 03:31 PM
I just wanted to weigh in on the 6sl7 thing. I have an ancient "green" tweed amp That uses a 12sj7 in the preamp and a 6sn7 in the PI 2(6v6). It is, without question the finest sounding amp I have ever heard! The 12sj7 is just like a 6sj7 but with 12v heater requirements. The tone is very warm with HUGE round treable notes that sound as big as a chord and are never harsh. Playing lead on this amp is SOOO good. The amp has a very screwed up filament circuit that has one side of the heaters tied to the filement centertap AND the 6v6 cathodes, which makes no sense to me but works! This amp also has a field coil speaker so tracking down its "mojo" and recreating its sound might be tough, but I am in the process of trying to recreate the circuit without all the weird stuff , and keep most of the magic, I will post the results when done. Oh BTW the 12sj7 is also grid leak biased.