Out of the closet - B120 with original Mullard EL34s

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Out of the closet - B120 with original Mullard EL34s

Postby GilgaFrank on Sat May 27, 2017 7:34 am

Just digging this out of the closet for a cleanup and service. My old (read: ancient) Sound City B120, Partridge transformer and still packed with the original Mullard and Brimar valves throughout. It's in desperate need of a service and clean, the filter caps are dried out so it hums badly so I'm wondering if I should fix it and sell it or ebay it as a project amp.

These amps are scary. No amp should ever have so much clean headroom combined with brain-damaging levels of volume. Whoever designed these was right on the dividing line between madness and genius. I'd be grateful for any info on this amp, possible year of manufacture? I'm guessing early 1970s.

Originally paid £60 for it back in the early 1990s. had to replace one valve base when it decided to arc over, since then it's pretty much been gathering dust so it's time to fix it up and move it on to someone who'll get more use out of it.

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Re: Out of the closet - B120 with original Mullard EL34s

Postby Papa Dog on Tue May 30, 2017 10:18 pm

not sure of the year, yet
it is an early Mk4 because it still carries the D/A tag
some curious "mods"
could we see some "gut shots" please?
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Re: Out of the closet - B120 with original Mullard EL34s

Postby Gooch on Wed May 31, 2017 3:26 pm

If you can replace the caps yourself, then do it. If not, then you're probably better off listing it with the known issues and selling as-is.
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Re: Out of the closet - B120 with original Mullard EL34s

Postby LD50 on Mon Jun 05, 2017 8:11 am

Looks mid 70s MkIV to me.
The window plug selectors make it later in the run (vs the earlier Hiwatt style).
I have just acquired a dead one as a project but the active preamp and 6 EL34s scares me so I may do the DR103 full conversion.
Yours looks too nice for that.
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Re: Out of the closet - B120 with original Mullard EL34s

Postby Papa Dog on Tue Jun 06, 2017 4:59 am

LD50 wrote:Looks mid 70s MkIV to me.
The window plug selectors make it later in the run (vs the earlier Hiwatt style).
I have just acquired a dead one as a project but the active preamp and 6 EL34s scares me so I may do the DR103 full conversion.
Yours looks too nice for that.

Yep, the one remaining "window" selector does date it, somewhat.
I would dearly love to get my hands on a few beater 120+s...always seem to find them when I am broke and never can find them when I have a few dollars to throw around.
I would strongly discourage doing the "conversion". There are many reasons, but mostly because even though there is a "new" Sound City line being done, it ain't the old DA or DMI and they do not make a 120+ or a 200+. What they make is very like a DR103 and more a "Dave Reeves Tribute" than not. So...they ain't being made by anyone anymore and sooner or later folks will run out of platforms to "rebuild".
There is really nothing to be afraid of. Yeah, 6xEl34s is a buncha power. The Transformer resistance is set up for 6 tubes, but there are some other, lower power alternatives.
The "active preamp" is one of the most commonly removed items, and I believe it is because it is not so well understood, but is likely one of the most versatile circuits that you will find. Ask questions. I bet I can tell you how to make it do what ya want it to without resorting to "gutting".
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Re: Out of the closet - B120 with original Mullard EL34s

Postby LD50 on Wed Jun 07, 2017 5:13 pm

Well, this is the bit of kit involved:

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:shock:
:whistling:
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Re: Out of the closet - B120 with original Mullard EL34s

Postby Papa Dog on Wed Jun 07, 2017 8:25 pm

wow...that almost makes me wanna cry
the words "rode hard and put away wet" come to mind.
However, it looks even more like it had become a donor and then left in a leaky shed.
But...if the transformers are viable it is not beyond hope
There Ain't No Such Thing As A Free Lunch.

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Of cabbages--and kings--"
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Re: Out of the closet - B120 with original Mullard EL34s

Postby Vucinic on Wed Jun 21, 2017 1:09 pm

My SC 200+, MKIV also, Carries Dallas Music Industries LTD (DMI) tag and seems to be from '74. I thing your B120 it's older.
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Re: Out of the closet - B120 with original Mullard EL34s

Postby Vucinic on Wed Jun 21, 2017 1:20 pm

My SC 200+, MKIV also, Carries Dallas Music Industries LTD (DMI) tag and seems to be from '74. S/N:74075613. I thing your B120 it's older.
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Re: Out of the closet - B120 with original Mullard EL34s

Postby Papa Dog on Wed Jun 21, 2017 4:01 pm

Vucinic wrote:My SC 200+, MKIV also, Carries Dallas Music Industries LTD (DMI) tag and seems to be from '74. I thing your B120 it's older.

check the cap and pot codes (if the pots are original)
I am uncertain that the SN has anything to do with the date.
There Ain't No Such Thing As A Free Lunch.

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"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--"
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