Other Amps

NAD

1

Just got this. No cabinet. 1951 GA-75. Awsome.

3

Love those old amps!!! I assume you're gonna' build a cab for it?

What made the 75 different from the GA-50?

4

Similar circuit, the GA-50 had two speakers (an 8” and 12”) and the amp sat on the bottom of the cabinet. Both Seth Lover designs made at the Gibson plant.

5

I say octals rule -- nice mello sound.

6

Very cool. I’d love an old Gibson amp, an EH-185 in particular.

7

The biggest circuit difference lies in the preamp. While the GA-50 uses pentode 6SJ7s for all the inputs, the GA-75 uses triode 6SC7s for the instrument inputs. While there really is no direct comparison in gain factors, the triode preamp of the GA-75 should give it more clean headroom than the GA-50. What’s really cool is all 4 inputs have their own triode, which leads to lots of possible voicing mods. Each instrument input can have its own thing going on.

8

Very cool. I’d love an old Gibson amp, an EH-185 in particular.

– Tsar Nicholas

Yea, I was looking at building an EH-185 before I stumbled over this one. Gibson was still farming out their amps during the EH-185 era. The GA series represents the Ted McCarty period when he decided that the amps should be designed and built in-house. I’ve always admired Seth Lover. A clever guy that didn’t get the attention he deserved at the time. The 1951 GA-75 is a real gem that epitomizes that first generation of amps. And the styling of the control panels? Who knows where that came from.

9

Nifty circuit design. Multiple inputs possibly being voiced differently. You'd think it would have been more common since then, 1951 was a while ago...

Higher/Lower gain (Mic/Accordion) Inputs were pretty normal, but nothing like that.

I guess the next step forward was multi-channel with effects like Tremolo and Reverb.

10

Do you think 5 inputs is enough? Are you going to try to find a field coil speaker to go with it?

11

Do you think 5 inputs is enough? Are you going to try to find a field coil speaker to go with it?

– Otter

This was one of Gibsons big amps of the day. Four instrument inputs so lots of guys could plug into the same amp I guess. Can’t imaging that sounded very good.

All of the GA-75s I’ve seen came with a Jensen P15N permanent magnet speaker. The schematic shows a 30 Henrie choke but no field coil.

12

A flaw of the original cab design was the slat opening, which effectively blocked half the speaker opening. Gibson later fixed that with the circular cutout.

The first few years of Gibson produced amps saw cabs made of 3/8” plywood. They later went with 3/4” redwood, but the original cabinet for this amp likely just fell apart.

13

Odd how we think of these old amps with multiple inputs as having options for different voices and sound options. But they were there really for the whole family to join in

Look forward to what kinda box you conjure up

14

Odd how we think of these old amps with multiple inputs as having options for different voices and sound options. But they were there really for the whole family to join in

Look forward to what kinda box you conjure up

– Vince_Ray

Yep, all four inputs voiced the same, and they all share a common cathode R/C network. Even more voicing possibilities.

I would imagine this amp appealed to traveling bands who spent time on the road. Only one amp to schlep. And now I’m imagining the Family VonTrapp all plugging in for an electric version of Do-Re-Mi. Thanks Vince.

15

Leaning toward this.

16

An early GA-20 inspired Cherry cab.

17

Yes kids there was a time when two players (sometimes more) went thru the same amp.

18

An early GA-20 inspired Cherry cab.

– Powdog

Wow! Stunning!

Someday, when I retire and have the time, imma build an amp... and I think I'd like it to be one of these old Gibson GAs or EHs. With one addition- I'd like to add tube-driven spring reverb, ala the Fender stuff...

19

Someday, when I retire and have the time, I’m gonna take this whole amp thing more seriously. Hopefully in four years.......

20

Finally warm enough around here to glue up some pine.

21

Amp arrived today. Put the tubes in and hooked it up to my 2x12 test cab. Two words.

My Gawd.

Even with the crappy JJ power tubes it is awsome. Can’t imagine anything new ever sounding like this. My hat is off to Seth Lover and Ted McCarty. What a treasure.

22

Next step, convert this big ‘ol narrow panel tweed cabinet....

23

...into a big ‘ol Gibson GA cabinet.

24

Add a few inches to the upper rail.

25

Is this amp going to be...for sale?


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