71 specs 50 watt clip on youtube

Get support and show off your MetroAmp 50 Watt kit builds.

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Post by VelvetGeorge » Fri Dec 07, 2007 3:14 pm

J.DavisNJ wrote:
VelvetGeorge wrote:Thanks, glad you like them. The 50w is straight 1987 specs. Just like all of the schematics you find on the web.
Transformers are my own 1202-118 and 784-139. These same parts are used in the upcoming 50 watt kit as well.

george
Forgive my ignorance George, but then what differentiates a '71 spec 50 watter from a '68 like described in your kit?? thanks.

-Joe
Filtering is higher on the metal panels. (3) dual 50uf cans.


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Post by VelvetGeorge » Fri Dec 07, 2007 3:15 pm

jctaudiodesigns wrote:Hey George,

I can't tell from your picture but it looks like you did not go all the way with the 71 spec, correct me if I am wrong but it looks like you used a .022 cap on the lead channel off V1 instead of the .0022 uf cap that is in your layout for the 71.
Good question. I'll have to default to the 50 watt experts. But it's my understanding that 50 watts retained the .022 cap longer than 100 watts, which changed in mid-late '68.

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Post by VelvetGeorge » Fri Dec 07, 2007 3:29 pm

Correction: I did use a .0022uf Sozo on V1B in the 50 watt on youtube.

My apologies. I probably looked at the Marstran site and felt this was most accurate. I referenced Brian's site constantly while building 3 or 4 of these amps, and the 50watt kit.

Thanks Brian!

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Post by rockstah » Fri Dec 07, 2007 4:38 pm

sounds real good. i like how chewy it is.
i used my strat with the darkburst pickup in it.

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Post by Brian Wallace » Sat Dec 08, 2007 10:41 am

I referenced Brian's site constantly while building 3 or 4 of these amps, and the 50watt kit.

Thanks Brian!

george
Your very welcome George, that's what the site is for. :)
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Post by J.DavisNJ » Sat Dec 08, 2007 10:01 pm

VelvetGeorge wrote:
J.DavisNJ wrote:
VelvetGeorge wrote:Thanks, glad you like them. The 50w is straight 1987 specs. Just like all of the schematics you find on the web.
Transformers are my own 1202-118 and 784-139. These same parts are used in the upcoming 50 watt kit as well.

george
Forgive my ignorance George, but then what differentiates a '71 spec 50 watter from a '68 like described in your kit?? thanks.

-Joe
Filtering is higher on the metal panels. (3) dual 50uf cans.


george
Ah, I see...

So the kit is '68 specs right? Will it still get as aggressive as the 71?

-Joe

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Post by thousandshirts » Mon Feb 04, 2008 4:29 pm

J.DavisNJ wrote: Ah, I see...

So the kit is '68 specs right? Will it still get as aggressive as the 71?

-Joe
The 68 spec is a bad ass amp. It is a mean machine. Might be all the aggro amp you need. And to change it to a metal panel (like a 71) setup is very simple. Just a few parts. You may find you like some of those changes more than the others, and end up with a new middle of the road.

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Post by jcs » Mon Feb 04, 2008 6:03 pm

very good tone and representive of what a 71 smallbox 50 like mine sounds like.

i use rft/siemens el34 or mullard xf2s or big bottle sylvanias (i sub in occasionally) along with early bugle boy 12ax7 but i go with a 12at7 often in v3 for more clarity and less mush (more plexi like) as my amp is very mid heavy and a gain monster.

i can also swap in some cheap tubes and make the amp sound pretty bright and harsh :roll: ,these amps are very picky about tubes imo.

to me the 50 watters of this era are lower mid heavier than most of the 100s which vary but have more kick down low.

someone mentioned rolling back the volume and playing koss licks,if you play along with the 'free' records, koss chord tone is fairly clean imo, except for leads where koss rolls up the volume to 10 on his pauls as seen in videos.

i have played and heard my 71 small box 50 thru many 4x12s over the past 12 or so years(pre rola-rola etc), oddly i have an early jcm 800 cab with the early 75s that sounds very good with this amp,tighter down low than greenbacks.

however the later celestion 75s are too stiff and bright,pretty nasty really.

another speaker that is great with these amps are the celestion 65s :wink:

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Post by jackboy10 » Mon May 12, 2008 4:31 pm

I have just heard ths lovely clip and it is what I want to get oout of my 1987 metro clone built using an old 2204 chassis and trannies with a metro 1987 standard ptp board loaded with sozo's.

my amp seems much thinner and bright compared to the sound on the clip- would it be the trannies I used from the late 70's 2204 compared to the ones George used in his 71 spec 1987/

Also was the clip recorded without any pedals or a hotplate at a very loud volume?

regards

Nick

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Post by frenchie » Thu Jul 24, 2008 2:13 pm

is there a layout available for the 71 specs ? someone can show it ?

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Post by thousandshirts » Thu Jul 24, 2008 6:50 pm

frenchie wrote:is there a layout available for the 71 specs ? someone can show it ?
It is with just a few exceptions, but the "71" metal panel 50 watt is almost identical to the "68" plexi 50 watt.

Screenshots from MetroAmp 50w Instruction Manual -- "Thanks, MetroAmp!"

"Plexi" Era

Image

"Metal Panel" Era
Image

Notes:

1.) The V1B plate bypass cap is changed from the Plexi (0.022uf) to the Metal Panel (0.0022uf).

2.) The 33+33uf filter that found in the middle of the preamp boards on the 1968 era 50w, it is raised by 1971 to 50+50u. Also the 50+50u is now in many cases no longer on the board, but instead, on the chassis surface.

3.) The NFB resistor is changed from the Plexi (47k) to the Metal Panel (100k). The NFB resistor on some later Metal Panel (100k) is hard wired to the 4 ohm tap. These later Metal Panels with this setup generally had no 0.68uf cap on V2.

4.) With the extra 0.68uf on V2, having the 100k on the 4 ohm tap can get a bit mushy. So 47k on to the 8 ohm tap (if using a 8 ohm cab) seems to be the popular preference for these.

5.) Some later Metal Panel amps use 25k pot for the presence control, instead of the 5k pot, and instead of the 0.1uf cap on the presence, they use instead a 0.68uf cap, along with a 4.7k resistor.

6.) A 5000pf bright cap was used on later Metal Panels.

EDIT: Photos updated
Last edited by thousandshirts on Tue Mar 31, 2009 8:11 pm, edited 1 time in total.

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Post by frenchie » Fri Jul 25, 2008 1:21 am

wow thanks .....great info ....detailed and all ... kick ass ! :D

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Re:

Post by Roe » Mon Sep 29, 2008 4:30 am

thousandshirts wrote:
1.) The V1B plate bypass cap is changed from the Plexi (0.022uf) to the Metal Panel (0.0022uf).

2.) The 33+33uf filter that found in the middle of the preamp boards on the 1968 era 50w, it is raised by 1971 to 50+50u. Also the 50+50u is now in many cases no longer on the board, but instead, on the chassis surface.

3.) The NFB resistor is changed from the Plexi (47k) to the Metal Panel (100k). The NFB resistor on some later Metal Panel (100k) is hard wired to the 4 ohm tap. These later Metal Panels with this setup generally had no 0.68uf cap on V2.

4.) With the extra 0.68uf on V2, having the 100k on the 4 ohm tap can get a bit mushy. So 47k on to the 8 ohm tap (if using a 8 ohm cab) seems to be the popular preference for these.

5.) Some later Metal Panel amps use 25k pot for the presence control, instead of the 5k pot, and instead of the 0.1uf cap on the presence, they use instead a 0.68uf cap, along with a 4.7k resistor.

6.) A 5000pf bright cap was used on later Metal Panels.
RE:
1) The 1969 amps used .0022s
2) the filtering also went up before 1971, I think it was higher when the alu era started in 1969
5) Didn't some 1973 amps use a .68uf on the 5k pot? Wasn't this what george lynch prefered? Or have I got it wrong?
6) the 5000pf was ordinary by 1969
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Re: Re:

Post by thousandshirts » Mon Sep 29, 2008 2:25 pm

Roe wrote: RE:
1) The 1969 amps used .0022s
Right -- and they had metal panels. . . :P To say "plexi = 0.022" and "metal panel = "0.0022" as regards the bright channel of lead (split) circuits seems "the most correct."
Roe wrote: 2) the filtering also went up before 1971, I think it was higher when the alu era started in 1969
Yes, hence "by 1971"
Roe wrote: 5) Didn't some 1973 amps use a .68uf on the 5k pot? Wasn't this what george lynch prefered? Or have I got it wrong?
I actually had a 1971 in that was wired that way, though I don't know if the wiring was original or altered later, as the amp was a mess
Roe wrote: 6) the 5000pf was ordinary by 1969
Other values are still used past 1969. . .Lets face it there is no cut and dried explanation that will satisfy each amp that Marshall produced (unless you use an explanation that includes alcohol). The best a person can do is watch their use of qualifiers and determiners (count language versus noncount language), and make sure you don't say "all," but "many," and instead of "none," say "few," etc etc.

I think if a person wanted to change their 50 watt from a "1968 spec" as seen in the 50 watt kit instructions to a "1971 spec" that our pointers, as laid out, would get them 95% of the way there. Surely we could always find strange exceptions. Or we could find amps that have been rewired, so that we may never know how they left the factory.

As an aside I found the .68 on the presence pot to be simply hideous in tone! :shock:

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Re: 71 specs 50 watt clip on youtube

Post by rastan » Fri Oct 24, 2008 8:59 am

Can you explain to me why some caps are changed...?Why George don't do exactly the same Marshall head?What's the differences about tone between original 1971 Marshall 50W head and Metroamp head?
Thank you!
P.S:Excuse me for my poor english... :-p

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