Another 12 Series Original vs Replica clip

[VelvetGeorge]

#12380 pic.

The notable things about this amp vs more typical 12 series:


all 1M pots are large, Mil spec

.68uf cathode caps are yellow box type

screen grid resistors on the output tubes, three are round chassis mount types (typically used in Majors)



George

[neikeel]

Ah George so you have SL 10584?

As you know I have SL10403 which is very much to 12 series spec with split cathode etc, although I suspect had 100uF cans across the preamp board and the 16/48 Hunts PI. I also have SL10366 but the preamp board was missing. I am restoring to same spec as the other (probably to sell) although cannot help wondering if that would have been shared on V1 with all the other early SL/SB features?

[Tazin]

Well, the basic circuit is the same between the two amps so the sonic differences between the two amps probably doesn't lay there. That just leaves the iron, filtering, rectification. My gut instinct tells me it's a combination of the old iron and old filter caps that create this unique complexity found in 12380. BTW, amp SL/12376 also has the same type of screen grid resistors as found in 12380, so it appears Marshall ran out of the normal ones and grabbed what ever they could find in the shop.

Neil,
It's tough to determine which circuit SL/10366 might have had, but I can say if the amp has the window style serial number (as found in JTM amps) then it would not have the split cathode circuit. If you have pictures of the amp in your photobucket library I might be able to determine which circuit the amp originally had.

[VelvetGeorge]

I do have 10584, it is shared cathode and has a Dagnall OT. I'm guessing it's late '67, just before the change to 12 series.

Which OT does your 10366 have Neil?

Re: complexity and randomness in vintage amps, I'd have to agree. I suspect I'd lose some of that swirl if I replaced the filter caps. It's definitely a sum of the parts equation, further evidenced by how close the replica with NOS caps and tubes is to the original.

george

[neikeel]

I do have 10584, it is shared cathode and has a Dagnall OT. I'm guessing it's late '67, just before the change to 12 series.

Which OT does your 10366 have Neil?

Re: complexity and randomness in vintage amps, I'd have to agree. I suspect I'd lose some of that swirl if I replaced the filter caps. It's definitely a sum of the parts equation, further evidenced by how close the replica with NOS caps and tubes is to the original.

george

!0366 has a Dagnall C1998 OT and the stamped serial exactly the same as my 10403, pots are same CTS ones, rather than the big RS ones like my 67 amps.

I think the replica sounds pretty good.

Re: Georges comments on tubes, I was playing around with preamp tubes this afternoon (bought some RFTs, Tungsram and BVA Brimars) in my 67 JTM50 and it was the YP Mullard ECC83s that made the difference, smooth, lots of gain, no excess fizz. BTW huge amount of gain in this amp for shared cathode with -128 OT . Sorry, going off thread

[Big Mike]

Badass.

Man, it's SOOO close. I could be happy with either.
Love em!

I doubt ANY non serious players could tell the difference.

[VelvetGeorge]

Here's a new one. Still comparing 12380 and 12093. But, the replica now has NOS tubes also.

12093 is in variac mode and 12380 is plugged into a variac set to 93V AC. Plate voltages and bias are the same in each amp.

I'll let you sort out which is which:

https://dl.dropbox.com/u/64682773/12380 ... 202013.wav" onclick="window.open(this.href);return false;


george

[neikeel]

Very interesting!

I think that the only way you can tell there is a difference is that one is slightly softer maybe slightly more harmonics, but hard to tell in isolation.

I reckon the clone is first (has new filter caps) and the original is second.

The difference you hear could easily be changed/reversed by switching the second amp to a newer set of speakers vs playing the second one through some well broken in prerolas or prerola clones IMO.

Do they feel different to play?

[VelvetGeorge]

The feel is very much the same. Like previous clips, I perceive some things while playing live and other things only when I play back the recordings. And even then, it depends on what I'm playing, where on the neck, which strings etc.

This clip was strictly audio from the iso cab, no camera audio mixed in. It's drier and very revealing.

Just a quick one while I had them on the bench. I'll see if I can make one with video and more settings this weekend.

george

[OnTheFritz]

Wow, incredible how close they are. Well done George!
Imagine that clone after some years under it's belt.

[tsma]

First of all, I appreciate that this is a 24-bit WAV file. That means I could put it in my DAW and listen through my monitors and hear it with real clarity. There, the differences were readily apparent. Amp number one has a much fuller low-end, a smoother top, and less growl. The lows might be deceptive, because amp number two is also quieter.

My first thoughts were, "Amp number two must be the replica. It doesn't have the balls of amp number one and the snarl is a bit raggedy, whereas amp number one has a more pleasing, refined growl." I found myself thinking how I would EQ amp number two to make the top a little smoother. I wasn't worried about less low-end for amp number two because that's something I typically need to shave-away when mixing.

I was definitely preferring amp number one.

But now I'm hearing the elements that make amp number two cool. That extra snarliness is pretty badass. And maybe amp number one is TOO full.

However, I think what's pretty incredible about what George has done is how they react. Listening to them carefully, these amps are responding in exactly the same way to his playing. I mean it's RIGHT THERE. So now I do wonder whether or not age and playing on the amp will bring them ever closer together in sound.

So here's a question (potentially a stupid question because while I own and occasionally use a soldering iron I don't know diddly about electronic circuits): what would 12093 sound like (and what would 12380 sound like) if their filter caps were swapped?

Incidentally, I do have a dog in this fight. When we're done here, 12093 is being sent to my address. In a purple box.



-bryan

[neikeel]

I was definitely preferring amp number one.

Incidentally, I do have a dog in this fight. When we're done here, 12093 is being sent to my address. In a purple box.

-bryan

Either way you are coming out with a great amp

So here's a question (potentially a stupid question because while I own and occasionally use a soldering iron I don't know diddly about electronic circuits): what would 12093 sound like (and what would 12380 sound like) if their filter caps were swapped?

Not stupid at all, I ask myself exactly the same when I do a cap job on a vintage amp! It will depend on what caps George used in building 12093 (F&Ts usually?). It is possible to get Erie mains cans and Hunts/Erie 32/32 NOSand reformed (I have a few for my projects but am about to run out. The 32uF 450v axial Daly's I have never seen for sale. TCC and very similar ones are around. You would have to go NOS on an amp like this and I personally would not use 'pulls' other than in a vintage resto and even then only if they reformed perfectly first time.

I may have an original Dagnall C1998 spare when a package arrives from George so those experiments could be done (I would be prepared to lend - not sell- the OT for Georges tests for the greater good ).

[Strat78]

#2 seems to be the 12830, it just has that open smile that new builds don't. George, do you have more shots of the chassis, she's a beauty!

[jimmyride]

I think the first one is the original, second replica.

[Tazin]

Both amps do sound really good....I don't even want to hazzard a guess as to which amp is which. There are differences between the two amps such as "tsma" pointed out, and I'm not sure if the volume difference which shows up on certain chords is playing tricks on my minds perception of what I'm hearing.

George, what kind of plate voltage are the two amps seeing under this lastest test?