Wednesday, January 27, 2010

Vintage vs. Vintage

I was over at Bruce Collins’ Mission Amps shop getting some demon tweaks done to my Masco amp when I noticed he had two very interesting vintage tube amps sitting side-by-side on the floor: A tweed Fender 5E3 Deluxe and a Gibson GA-6 Lancer. Both date from 1958. Both are in perfect original sonic condition. Both have two 6V6 power tubes, 5Y3 rectifiers, and original (or period correct) Jensen P12Q speakers. I was prepared to beg Bruce to let me plug in and play both amps, but no need. He immediately suggested I do a comparison test.

The Fender Deluxe was without it’s tweed covering but was otherwise intact. The Gibson GA-6 was in near mint condition. They were both in the shop for minor age-related repairs: faulty switches or plugs that cause noise.

While the circuits of the two amps are very similar, there are some differences.

The preamp in the GA-6 is a 12AX7 wired as a grounded cathode, using a 5 megaohm grid leak bias set up, it is not cathode biased... very old school, same as the 5A3, 5B3 and 5C3 tweed Deluxe but the Deluxe used octal, 6SC7 preamp tubes.

The two volume pots and the tone pot are less than 500k, unlike a tweed Deluxe that uses 1M pots for volume and tone controls. Tone control caps in the GA-6 are the same values as the Deluxe.
The phase inverter in the GA-6 is a 12AX7 wired as a paraphase driver, same as the octal preamp tubed 5A3, 5B3 and 5C3 Deluxes.

In the Gibson the plate voltage to the power tubes is a bit hotter then a tweed Deluxe and the power tubes are idling painfully hot at about 14 watts each. Screen voltage to plate voltage ratio is lower then the Deluxe and the 5 watt power resistor used for biasing the 6V6s is 200 ohms vs 250 ohms for a Deluxe and there is no cathode bypass cap on the resistor while a tweed Deluxe uses a 25uF bypass cap.

Power supply filter caps are all 20uF vs 16uf on a tweed Deluxe.

A good running tweed 5A3, 5B3 and 5C3 Deluxe will make about 10-12 watts clean and this particular GA 6 made about 12-13 watts clean with the same size output transformer as the Deluxe.

So… How does this all translate to tonal differences? There were dramatic contrasts in the sound of the two amps. I used my big red bullet mic – which is extraordinarily hot, putting out 1 volt of current when I hit a loud passage.

Both amps sounded good right out of the gate, but the Gibson was clearly superior. The tone is bigger and warmer, with a much more natural sounding tearing on the notes. The breakup was organic and closely coupled to the pressure I put on the mic. To be honest, it sounded beautiful. I would gig that Gibson amp right now.

The Fender Deluxe had a nice vintage tone, but it just could not measure up to the Gibson. Its tone was thinner and less “connected” to what I was doing with the mic and harp. It sounded slightly boxy. At one point a ghost note popped up –the dreaded boogieman of all harp amps – while I was playing the 2-draw on an A harp. The 5E3 Deluxe amp is legendary among guitar players, and I offer no argument there. This is just about how it reacts when faced with a hot bullet mic and a harp played in second position.

The Gibson had absolutely no issues. No ghost notes or cone cry or nasal tone or noise or anything. You would have to do nothing to this amp to make it a killer harp amp: It is already there.

Small amps with two 6V6 power tubes are among the nicest sounding harp amps. They are too underpowered to carry through a loud blues band, but mic’ed or lined out they are wonderful. I sold a 1947 Gibson BR-6 amp last year and I still painfully regret doing so, especially after playing the GA-6 which sounds remarkably similar.

Many thanks to Bruce Collins at Mission Amps for graciously allowing me to thrash two very valuable vintage amplifiers. Bruce is also the drummer in my blues band, Roadhouse Joe.


peter Moore said...

Nice post, very interesting. I owned a Gibson GA-40 years ago. Bought it at a New Bedford, MA musical pawn shop, the owner said it had belonged to Magic Dick's. Whatever. Still, it was a bargain and I used it for years for recording and gigs. Very different than my Tweed Deluxe but great tone. In the end, I thinned the herd and sold the GA-40 and a tweed Vibrolux as I was not playing them enough.

I kept the Deluxe because I like the ability using the Bright and Normal Volume to adjust the tone. For whatever reason , my deluxe bleeds the bright when plugged into the normal channel. A tech told me this was a mod he had employed. I am sure Mr. Collins can speak better to this than I. I have often wondered whether you can put a"line out" in an old tweed amp like your champ. Can you ask Mr. Collins that for me?

Oh, glad to see you still have the Masco. You will regret sellingthat, the way I do about my GA40! (I wonder if Magic Dick feels the same way?!)

Bruce Mission Amps said...

The 5E3 is the weapon of choice for many guitar players but there was no doubt the Gibson Lancer was superior in tone when blowing harp through it.
A side note... isn't it amazing how amateurish the Gibson GA 6 is built compared to the pro quality eyelet board and layout of the Fender tweed Deluxe..?

Rick Davis said...

Old Gibson amps are cool. I once briefly played through a '59 Gibson amp with 2 6L6 power tubes and a big ol' 15-inch Jensen alnico speaker at a blues jam. Not sure of the model number. It was like a Fender narrow panel Pro knockoff. Sounded great.

EV630 said...

Were they your amps Bruce, or were you working on them for someone?

On a tangent - like your Masco pick, Rick. I have one on the way from Skip Simmons.

Rick Davis said...

EV630, I think you will like the Masco a lot. Which model is it?

The ME-18P that I have has a deep "oh" sound, while many other harp amps have kind of an "ah" sound. Before voicing the amp for harp, it had a "woofy" quality.

I know Skip Simmons, and he does excellent work (at a premium price). Be sure to let me know how your Masco sounds and I'll make it an article here on the blog.

EV630 said...


I don't know the model - MA17 I think. It's the same one he did for Estrin and Oscher.

Your Oh and Ah descriptors... does Oh indicate more bass and Ah more of a mid range tone?

Anyway, I'm getting this on the recommendation of a friend and I have heard some clips on Youtube, so I know I'll like it.


Bruce Mission Amps said...

These are not my amps. A customer of mine wanted me to clean up some noise in both of them. The Deluxe had a bad input jack and the GA 6 had a nasty hum.
It was repaired by moving some high impedance grid wires around and installing a Faraday shield on the back of the upper rear valance panel.

Bruce Mission Amps said...

The tone control is actually connected to the bright channel on both of these amps... so yes the normal channel is not so good (with respect to the tone pot) and the highs are bled off through the common parallel junction of the two volume controls.
That is a stock artifact.
Also, if you plug into the bright channel and turn it's volume to zero, then turn the normal channel up, you'll hear solid but muted audio from the amp. It will only make about 3-4 watts like this but you can now start milking in the bright channel volume control with the tone pot set for taste to mix the sounds together.
A classic guitar setting would be, plugged into the bright channel, volume on 5 to 7, normal channel on 8 to 10 and the tone pot set to taste but usually around 7 to 9.
Harp would be different of course.
You reverse the input and plug the mic into the normal channel as it is duller right from the start since the tone control is not actually connected to that channel's volume control and then tweak the overall amp tone with the bright channel's volume control.

Yes, you can install a very simple line out from either of these amps but the deluxe is easier since it has two output speaker jacks so you use the other speaker jack as the line out "send" jack.
The Gibson would require a jack or a way to get the signal out to a jack.

Mike Lynch said...

One of my best setups was a late '50s Gibson Gibsonette (1 x 10) and an early '60s tweed Ranger (1 x 12). Both amps sounded great, but together they were killer. I agree, dual 6V6 amps rule!

Adam said...

Are these push-pull class A?