New tweed-style amp

[Bobo]

I thought I'd post some pics of my new amp.

It is a clone of a 1950-1951 Fender Super-Amp. The hand built chassis and final assembly were done by Bruce Collins of Mission Amps in Colorado and the tweed V-front cabinet was created by JD Newell of Newell Amps in Georgia.

This amp is somewhat unique, in that it uses an all-octal tube preamp section. That was Fender practice before 1955 or so. As I understand it, the power tubes are cathode biased and the preamp section is grid-leak bias. The phase inverter is of the paraphase type.

What it all adds up to is a primitive, yet full and "round" tone. It sounds wonderful clean but has a nice, natural, gritty overdrive at higher volumes. To me, it's the ideal amp for blues, early rhythm 'n' blues, and early rock 'n' roll. It has a different sound than a later wide-panel or narrow-panel tweed amp.

The amp is a 5B4 circuit but it has some slight upgrades (modern 6L6GC power tubes instead of the original 6L6G spec, 6SL7GT preamp and phase inverter tubes instead of the 6SC7 that was in the original version). Power tubes are modern SED "Winged C"; and the 6SL7GT preamp tubes, as well as the 5U4GB rectifier, are NOS. It has beefy power and output transformers from Allen/Heyboer. It has a bass-cut switch tied to the bright channel. Power output is about 22-24 watts RMS, which could be boosted to 25-27 using a GZ34 rectifier.

Speakers are Weber alnico 10-inchers - one 10A125 and one 10A125-O. The V-front cab design helps spread the sound out in a room.

I've had the amp for just a few days and am very happy with it so far, given my limited ability as a guitar player. Experimenting with it and having fun.

 

[capnjuan]

Hi Boris and congratulations on your new (but vintage) amp; it's a beauty! Octal tubes in the preamp wasn't just Fender's practice; no matter what make including Gibson, nearly all the post-war to mid-'50s amps had octals in the preamp. Ampeg (and Guild) used them into the early 60s; Jets, Mercurys, and early reverberrockets had them.

The 6SC7 is a 'common-cathode' twin-triode tube; has two halves (triode sections) like a 7025/12A_7 except each tube half shares its cathode with the other; not so with the 6SL7 and usually not so with 12A_7 tubes. You can't 'voice' the tube halves separately.

'Grid-leak' bias produces a 'way-back' tone; probably not as crisp as conventional cathode bias but a warm, fat tone that I think is the hallmark of the era. It's a beautiful amp and I can't think of better choice than those Weber classics. 8)

 

[Bobo]

Hi Boris and congratulations on your new (but vintage) amp; it's a beauty! Octal tubes in the preamp wasn't just Fender's practice; no matter what make including Gibson, nearly all the post-war to mid-'50s amps had octals in the preamp. Ampeg (and Guild) used them into the early 60s; Jets, Mercurys, and early reverberrockets had them.

The 6SC7 is a 'common-cathode' twin-triode tube; has two halves (triode sections) like a 7025/12A_7 except each tube half shares its cathode with the other; not so with the 6SL7 and usually not so with 12A_7 tubes. You can't 'voice' the tube halves separately.

'Grid-leak' bias produces a 'way-back' tone; probably not as crisp as conventional cathode bias but a warm, fat tone that I think is the hallmark of the era. It's a beautiful amp and I can't think of better choice than those Weber classics. 8)

Thanks, capnjuan! It sounds like you really understand these early-type circuits. I guess way back in my mind I was aware that octal preamp tubes were used by the other amp makers early on too, but I had sort of forgotten that. I think Valco/Supro also used them into the '60s, like Ampeg and Guild, right?

It occurred to me awhile back that the sounds of the guitars in many of the 1950s recordings I love were probably amplified through amps that were at least a few years old at that time. For example, guitarists at recording sessions in '55 or '56 were probably often using amps from '51, '52, '53... or older. So that's what set me off searching in the direction of cathode-bias and all-octal tubes.

Anyway, I've always just loved that early, primitive, fat sound (as you said, "way-back"). Of course, there is a bit less overall definition and clarity with this kind of circuit, but that's OK with me.

Regarding the 6SL7s: from what I gather, the preamp tube sockets on this amp were wired to accept 6SL7s because NOS non-microphonic 6SC7s are considered difficult to find these days, while good NOS 6SL7s are more plentiful.

 

[capnjuan]

I tried to look at some old Supro schematics on Schematic Heaven but it's still iffy over there but I know Ampeg stayed with octals and, because of unmistakable similarities, so did Guild; some 66Js, all the 98RTs, and at least some of the 99Js ... same as 66J but with 6L6s. Didn't know about the 6SC7's tendency towards microphonics but, Bruce Collins is right, there are a lot of very good 6SL7s out there.

They get their '6' from the fact that the heaters are 6 volts where the 12A_7s are 12 volt. 6 volt AC heater circuits can be touchy when it comes to noise and grounding. In the old days, one side of the heater circuit was grounded to the chassis, the other side fed the heaters. The 12A_7 heaters are wired 'humbucker' damping their own noise which makes grounding - at least for noise abatement reasons - less of an issue.

Agree with your remark about the tone and gear was being used in '50s recording sessions. That's Ms. Carole Kaye of the 'wrecking crew' with a narrow panel Fender behind her:

I like Clapton, Bloomfield, the others as much as the next guy but I came of age when we were still going to sock hops in the gym on Friday afternoons ... guys like these were my first guitar heroes ... I guess they still are:

Enjoy your amp; it's a time-traveling machine

 

[Ian]

Ok, I'll ask the question. "Who's the band in the bottom photo, and why is the name of the band blocked out ? "

Cheers, Ian

NB Some Hifi gear (particularly preamps) still use the 6SN7/6SL7 valves. I think the Melody line of amps use them. IIRC they are both interchangeable, it just alters the gain ?

 

[mad dog]

Boris:

That is a drool worthy beauty. If you could ever find your way into making some clips ...

MD

 

[capnjuan]

Ok, I'll ask the question. "Who's the band in the bottom photo, and why is the name of the band blocked out ? "

Hi Ian; it's a picture of a schoolboy band from 50 years ago whose name is blocked out because I don't have the band's permission to use it. If they'd become musical biggies, that might change things.

It's offered here only to evoke a time when every kid wanted a Fender Pro like Boris' repro ... or a Gibson ... and not a Marshall stack and nine pedals. Note the amps ... a '57-'58 Gibson (probably) GA45 Maestro and two late-50's, narrow-panel Fenders of the same vintage as Ms. Kaye's in the pic above.

and just for a little 'Memory Lane' fun ... Chuck Berry in France, in the late '50s doing 'Rollover Beethoven' through what looks like a Gibson GA400 ... and I think that's an early Gretsch bass amp on the right:

 

[Walter Broes]

Very cool looking amp, I'd love to play through one of those earlier tweeds someday. Only have experience with the narrow-panel later models.

Seriously cool cab too btw!

 

[Bobo]

Thanks for the nice words, everyone!

A friend of mine came over last night -- someone who can REALLY play guitar -- and he put the amp through its paces (using a Telecaster). What I found was that the amp basically stays clean up to about 4 on the volume control. At that point the tone acquires just a slight edge. At about 6, more "fur" is added to the overdrive, and then at 9 or 9 1/2 it gets downright nasty and becomes even more gritty up to max volume (12). So there are a lot of usable tones in this amp. There is more grit in the bright channel than in the normal channel. Overall, the amp is really a primal beast, but it is capable of some really full, round, clean (and semi-clean) tones too.

My friend -- and I will qualify this by stipulating that he's a blues/early rock 'n' roll fanatic like me -- said it was the nicest amp he'd ever played through. Upon leaving, he said he was going home to play some Howlin' Wolf records. Said the amp put him in the mood!

 

[Ian]

Thanks Capn, they looked like a band that I thought that I ought to have known the name of...

Boris, that sounds like a great amp, any chance of some sound clips ? (of course if it turns out that you are some 14 year old guitar prodigy sitting on the end of your bed doing amazing things on your guitar, then dont bother :lol: )

Cheers, Ian

 

[Jeff Haddad]

Very nice! That's a great looking amp, cool idea for something of a different tone than alot of what's around.

I built a Mission Amps 5E3 kit several years ago and Bruce was great to deal with. When I called him about a problem I was having, he had me check some voltages and I could tell he was nervous about me poking around inside. :shock:

 

[Default]

Agree with your remark about the tone and gear was being used in '50s recording sessions. That's Ms. Carole Kaye of the 'wrecking crew' with a narrow panel Fender behind her:

Just wanted to point out Carol's custom Guild 12 string. She could not buy a twelver, so somehow she had that 12 commissioned - whether by Guild itself or by someone who could put the pieces together. Guild never offered a thinline single cutaway 12, but wouldn't one be nice. :mrgreen:

 

[fronobulax]

Here you go for the 12 string.

 

[skinny]

Boris,
Congrats on the amp!! That's a beauty !!
Bruce Collins is a stellar tech. He's tuned up a few of my amps over the years.
With a minor adjustment, he turned my Magnatone 213 into a Deluxe killer !!

skinny

 

[Bobo]

Boris,
Congrats on the amp!! That's a beauty !!
Bruce Collins is a stellar tech. He's tuned up a few of my amps over the years.
With a minor adjustment, he turned my Magnatone 213 into a Deluxe killer !!

skinny

Hi Skinny, thanks! You have a Magnatone 213? Cool amp! The regular rig for my band's guitarist/singer is a '59 Magnatone 260. Nothing like the vibrato of those old Maggies.

 

[iismet]

It's offered here only to evoke a time when every kid wanted a Fender Pro like Boris' repro ... or a Gibson ... and not a Marshall stack and nine pedals.

:wink:

 

[tele4tone]

Bruce designed the circuit for the Weber 5E3X2. I love his work. Fantastic looking cab! Have you got to work jumpering inputs yet? It's amazing how that works on my Risen Brute.

Jeff

 

[Bobo]

Bruce designed the circuit for the Weber 5E3X2. I love his work. Fantastic looking cab! Have you got to work jumpering inputs yet? It's amazing how that works on my Risen Brute.

Jeff

Jeff, I agree. The work on this amp is superb throughout. JD Newell of Newell Amps did the cab, which is supposed to be exact spec '50 Super-Amp. On jumpering inputs: unfortunately, that won't work on this amp. Bruce explained it's because the octal preamp section uses 1940s-style contact grid-leak bias rather than resistor cathode bias. But that's OK with me... the volume and tone controls allow a lot of different sounds and tones. Very touch-sensitive, as they say.