[Rob Reedijk]

I have started to look at selling my Roland Jazz Chorus JC-120. In
trying to date it, things have become interesting.
For a very interesting read on Roland, check out
http://www.soundonsound.com/sos/nov0...les/roland.htm
That gives you a pretty neat history. In it discusses the JC-120 first
appearing in 1975. The next year the Boss CE-1 Chorus Ensemble was
launched, and to quote the article, "The effects circuitry was based on
a single modulated BBD delay line and was lifted in its entirety from
the previous year's JC (Jazz Chorus) guitar amplifiers..."
As many of you know, a CE-1 fetches about $500 on ebay at times. The
funny part of this is that a CE-1 can be worth more than a JC-120!

I decided to have a look in my JC-120. What I found in the circuit
were the two following ICs: MN3101 (clock) and MN3007 (1024 stage bucket
brigade) which are not what you would find in a CE-1, but are in a CE-2
which is the more compact analog chorus ensemble that came out later.
(The CE-1 is based around the MN3002 512 stage bucket brigade). I would
also say that while my JC-120 has the same critical ICs as the CE-2, they
are not set up in quite the same arrangement as a CE-2 has so while I
am guessing my JC-120 may be a "second generation" Jazz Chorus, I don't
think there is as close a connection to the CE-2 circuit as a first
generation JC-120 has with a CE-1.

By the way, the only circuit I could find on the web for a Jazz Chorus
can be found at
http://blueguitar.org/schems.htm
It shows the same two ICs as mine, but it does have a different set of
Line outputs---it has two: Normal (mixed) and Effect. Mine just has
one line output which appears to be mixed.

I know that the current production is more complex---it has two line outs
one is R(ight) and the other is L(Mono) plus it has a full effects loop
with a send and returns and level switch and series/parllel switch.
The question is, what kind of chorus effect does it contain? Do the
current models actually still have analog circuits with bucket brigade
chips or did they switch to cheaper digital circuitry?

I am hoping to start a discussion here on properly dating this series of
amps. All I have found are a few mentions of the early ones not having
effects loops. I'd like to find out if the very earliest ones indeed
had the the CE-1 circuit in them---does this make them more valuable
since a CE-1 fetches top dollar? How long did Roland put in CE-2 type
bucket brigade ICs in JC-120? Till this day?

Here are the details from my amp:
SN: 258xxx
Rear panel: 2 Ext Spkr jacks/Line Out/FS(Chorus&Vibrato)/FS(Reverb)
FS(Distortion)/2 Main In jacks
Chorus Vibrato Front Panel Switch is 3 position toggle (later ones went to
a knob)
There are bright switches.
Circuit board numbers are 70116280 and 70116290
And for those of you who have wet dreams over JRC4558s, well there are
three of them in this model, even though the built-in distortion don't
sound anything like a Tube Screamer...

Thank you for taking the time to read this post about a solid state amp
(I love tube amps for any of you who want to give me a hard time).

Rob R.

[Fletch]

Rob Reedijk wrote:
I have started to look at selling my Roland Jazz Chorus JC-120. In
trying to date it, things have become interesting.
For a very interesting read on Roland, check out
http://www.soundonsound.com/sos/nov0...les/roland.htm
That gives you a pretty neat history. In it discusses the JC-120 first
appearing in 1975. The next year the Boss CE-1 Chorus Ensemble was
launched, and to quote the article, "The effects circuitry was based on
a single modulated BBD delay line and was lifted in its entirety from
the previous year's JC (Jazz Chorus) guitar amplifiers..."
As many of you know, a CE-1 fetches about $500 on ebay at times. The
funny part of this is that a CE-1 can be worth more than a JC-120!

I decided to have a look in my JC-120. What I found in the circuit
were the two following ICs: MN3101 (clock) and MN3007 (1024 stage bucket
brigade) which are not what you would find in a CE-1, but are in a CE-2
which is the more compact analog chorus ensemble that came out later.
(The CE-1 is based around the MN3002 512 stage bucket brigade). I would
also say that while my JC-120 has the same critical ICs as the CE-2, they
are not set up in quite the same arrangement as a CE-2 has so while I
am guessing my JC-120 may be a "second generation" Jazz Chorus, I don't
think there is as close a connection to the CE-2 circuit as a first
generation JC-120 has with a CE-1.

By the way, the only circuit I could find on the web for a Jazz Chorus
can be found at
http://blueguitar.org/schems.htm
It shows the same two ICs as mine, but it does have a different set of
Line outputs---it has two: Normal (mixed) and Effect. Mine just has
one line output which appears to be mixed.

I know that the current production is more complex---it has two line outs
one is R(ight) and the other is L(Mono) plus it has a full effects loop
with a send and returns and level switch and series/parllel switch.
The question is, what kind of chorus effect does it contain? Do the
current models actually still have analog circuits with bucket brigade
chips or did they switch to cheaper digital circuitry?

I am hoping to start a discussion here on properly dating this series of
amps. All I have found are a few mentions of the early ones not having
effects loops. I'd like to find out if the very earliest ones indeed
had the the CE-1 circuit in them---does this make them more valuable
since a CE-1 fetches top dollar? How long did Roland put in CE-2 type
bucket brigade ICs in JC-120? Till this day?

Here are the details from my amp:
SN: 258xxx
Rear panel: 2 Ext Spkr jacks/Line Out/FS(Chorus&Vibrato)/FS(Reverb)
FS(Distortion)/2 Main In jacks
Chorus Vibrato Front Panel Switch is 3 position toggle (later ones went to
a knob)
There are bright switches.
Circuit board numbers are 70116280 and 70116290
And for those of you who have wet dreams over JRC4558s, well there are
three of them in this model, even though the built-in distortion don't
sound anything like a Tube Screamer...

Thank you for taking the time to read this post about a solid state amp
(I love tube amps for any of you who want to give me a hard time).

Rob R.

What kind of speakers are in it? Jensens, Emminence? Are there date
codes printed on the frame? Sets of numbers.

How you would read a typical date code is as follows...

If it is, say 308638, then the 308 is the part number, the 6 is the year
within the given decade and the 38 is the week of the year.

If you know it is a 70's era model, then the year is easy, 1976,
produced in the 38th week. That would be a good bet that your amp is a
1976. So, knowing the decade is a little important.

You might also check the main power tranny. As I recall the JC120 is
solid state, but should still have a power tranny. There will be two
numbers, one will typically follow the above date code conventions, six
numbers; the other will be the serial number and may have a letter as
the first character.

I just got a Twin and the date codes on the speakers and the trannys all
point to the second half of 1969 or very, very early 1970 because they
are dated, via the date code, as 1969.


--Fletch

[Rob Reedijk]

In rec.audio.pro Fletch wrote:

What kind of speakers are in it? Jensens, Emminence? Are there date
codes printed on the frame? Sets of numbers.

How you would read a typical date code is as follows...

If it is, say 308638, then the 308 is the part number, the 6 is the year
within the given decade and the 38 is the week of the year.

If you know it is a 70's era model, then the year is easy, 1976,
produced in the 38th week. That would be a good bet that your amp is a
1976. So, knowing the decade is a little important.

I looked all over the frame in the usual places and nothing. They are
Speakers, made in Japan. The only code I could find was printed on the
cones and I think they read:

9340
PCKI

You might also check the main power tranny. As I recall the JC120 is
solid state, but should still have a power tranny. There will be two
numbers, one will typically follow the above date code conventions, six
numbers; the other will be the serial number and may have a letter as
the first character.

The power transformer reads
245-273N
2LX1

No output transformer of course.

I just got a Twin and the date codes on the speakers and the trannys all
point to the second half of 1969 or very, very early 1970 because they
are dated, via the date code, as 1969.

Thanks for your help.

Rob R.

[[email protected]]

The schematic at blue guitar (if I remember correctly) is for the 1984
head model of the amp. I have at least two more schematics somewhere
in my archives. Those can also be found from the Internet (one is at
the Free Information Society schematics page - where the rarer one
was, I can't remember - and frankly I don't even care to search since
this is likely the third or fourth time I post this same info). There
have been at least 8 versions of that amp - most of them are quite
different from each other. The only things that seem to be common are
the stereo arrangement, controls (sort of), chorus circuit and
cosmetics.The version should be written at the back of the amp in a
format of JC-120-xxx where the xxx is a letter code marking the
version. Roland has never bothered to explain its meaning in public
but if you email them they will likely tell you the year when the
concerned model was introduced. And you also know the serial
number...! Amplifiers with serial of # 481650 - 502499 have been
introduced after February 1979 but I don't know about the rest. Guys
at Roland should know.

[Rob Reedijk]

In rec.audio.pro wrote:
The schematic at blue guitar (if I remember correctly) is for the 1984
head model of the amp. I have at least two more schematics somewhere
in my archives. Those can also be found from the Internet (one is at
the Free Information Society schematics page - where the rarer one
was, I can't remember - and frankly I don't even care to search since
this is likely the third or fourth time I post this same info). There

It's a great resource:
http://www.freeinfosociety.com/elect...page.php?cat=1

There are two versions there. One is the same schematic that I referenced
in my first quote. But my amp appears to be more like the other listed
schematic.

have been at least 8 versions of that amp - most of them are quite
different from each other. The only things that seem to be common are
the stereo arrangement, controls (sort of), chorus circuit and
cosmetics.The version should be written at the back of the amp in a
format of JC-120-xxx where the xxx is a letter code marking the

Mine just says JC-120. There is no letter code.

version. Roland has never bothered to explain its meaning in public
but if you email them they will likely tell you the year when the
concerned model was introduced. And you also know the serial
number...! Amplifiers with serial of # 481650 - 502499 have been
introduced after February 1979 but I don't know about the rest. Guys
at Roland should know.

I guess I have to email Roland!
My serial implies it's fairly early. However if there is truth to the
Sound on Sound article stating that the first ones have the identical
chorus circuit to a CE-1, then mine isn't one of those.

Thanks for all the help.

Rob R.

[Rob Reedijk]

In rec.audio.pro wrote:
version. Roland has never bothered to explain its meaning in public
but if you email them they will likely tell you the year when the
concerned model was introduced. And you also know the serial
number...! Amplifiers with serial of # 481650 - 502499 have been
introduced after February 1979 but I don't know about the rest. Guys
at Roland should know.

Wow! Roland was quick to reply. Mine is from late 1982. Seeing as the
number is 258xxx and the series that you quoted is from after 1979, it is
possible that they don't follow serial numbers in order. Unless
481650 - 502499 is from a lot later than 1979.

Rob R.