freestompboxes.org

What are the functional equivalents or closest thing to the specs of these transistors as used in the 76/77 MXR Dyna Comp?

SC 1849
MPS 5172

I think the later is still available, or it might be the other way around. Not sure but I need to source these soon before my build. I already have a 3080 Operational Transconductance Amplifier that I'll need too.

Thanks.

Mouser stocks the MPS-5172 and Small Bear has the SC1849's. 2N5088 has been said to work well in place of the SC1849.

Thanks! What's the difference between the "SC1849" and Small Bear's "2SC1849" transistors?

snmavronis wrote:Thanks! What's the difference between the "SC1849" and Small Bear's "2SC1849" transistors?

2SC1849 is one louder!

snmavronis wrote:Thanks! What's the difference between the "SC1849" and Small Bear's "2SC1849" transistors?

Probably the same thing. Different manufacturing labeling schemes. Mine just says C1849, but made a very nice 'script'

snmavronis wrote:Thanks! What's the difference between the "SC1849" and Small Bear's "2SC1849" transistors?

Many Oriental manufacturers miss off the first two characters, so there's no difference at all.

The transistors used in the Dynacomp aren't special - you can use pretty much any silicon NPN medium gain device. I've built them (or things similar to them) using BC108, 2N3707, BC183L, PN239, and various others. There is NO CHANGE in the performance whatsoever!

on japanese semiconductors the first character is one less than the effective numbers of electrodes.

diodes begin with "1" , and transistors with "2"

the second character is always an "S" to indicate a semiconductor

the third character indicates the type of semiconductor

A = high freq PNP transistor
B = low freq PNP transistor
C = high freq NPN transistor
D = low freq NPN transistor
J = P channel FET
K = N channel FET
S = small signal diode

in the case of c1849 you could assume the unmarked "2s" as probably not important as most of the information is with the remaining numerals.

hope this helps someone.

mictester wrote:

snmavronis wrote:Thanks! What's the difference between the "SC1849" and Small Bear's "2SC1849" transistors?

Many Oriental manufacturers miss off the first two characters, so there's no difference at all.

The transistors used in the Dynacomp aren't special - you can use pretty much any silicon NPN medium gain device. I've built them (or things similar to them) using BC108, 2N3707, BC183L, PN239, and various others. There is NO CHANGE in the performance whatsoever!

I'd tend to agree with you.

If it weren't for a FK1 dynacomp clone that wat acting weird until I replaced the mojo-brand-type unknown transistors that do the envelope cap charging. Relpacement with 2 simple BC547's cured the bug. Have seen this problem more often.

I ended up finding the transistors in a local shop and they were cheap. So, I plan to use them in my build. Does the hfe matter at all in this circuit? The MPS5172 were kind of low.

rhandy gaye wrote:on japanese semiconductors the first character is one less than the effective numbers of electrodes.

diodes begin with "1" , and transistors with "2"

I appreciate your explanation of 2SCxxxx transistor designations....in fact, I made a notation in my files for reference.
While you are not incorrect saying that the '1' and '2' are one less than the number of electrodes, the actual thing being
counted is the number of PN junctions.

Another small note:

Some 2SCxxxx transistors have letter designations on them indicating the gain range...similar to the A,B,C designations
on the BCxxx series transistors. For instance:

My C1849 has an 'R' in the lower left corner. This corresponds to:

O..... 90~150
P.....120~200
Q.....160~260
R.....210~340
S.....290~460
T.....400~650

These designations are not consistant with all transistors, as I have seen the 'O' to designate 70~140 on the 2SC1815.

jrod wrote:I ended up finding the transistors in a local shop and they were cheap. So, I plan to use them in my build. Does the hfe matter at all in this circuit? The MPS5172 were kind of low.

I hope it doesn't matter too much.....mine are in the 225 zone.
It's getting difficult to impossible to stay authentic.

PokeyPete wrote:It's getting difficult to impossible to stay authentic.

What's "authentic"? You can't buy many of the components that were used in the late 70s when the Dynacomp was new. MXR changed the components over time, to reflect what they could get cheapest - just like every other manufacturer. Electro Harmonix didn't choose the transistors they used in the Big Muff Pi for sound - they chose them for price - MXR did exactly the same!

mictester wrote:

PokeyPete wrote:It's getting difficult to impossible to stay authentic.

What's "authentic"? You can't buy many of the components that were used in the late 70s when the Dynacomp was new. MXR changed the components over time, to reflect what they could get cheapest - just like every other manufacturer. Electro Harmonix didn't choose the transistors they used in the Big Muff Pi for sound - they chose them for price - MXR did exactly the same!

Hi Mictester, I understand your point. I guess 'authentic' to me is a concept. It's what my mind will accept as 'real'.....either from an old schematic, or gut shot, or whatever makes me believe the part is correct. If I want to build an 'authentic' representation of a pedal, I'll use what my mind believes is an actual part. Now, my part may have a date code of '96 instead of '73....but to my mind that's OK.....what matters is the part number. I know in most cases parts really don't matter that much......but......sometimes it just feels good to be 'authentic'.

So-called NOS parts don't mean anything. They are a myth and mojo doesn't exist. But if you are trying to clone a pedal from a certain era it's cool to use the same parts it had if they are available. But I'm game for anything "equilavent" to the original funtionality and specs so long as the resulting clone sounds representative of the original pedal.

PokeyPete wrote:
Some 2SCxxxx transistors have letter designations on them indicating the gain range...similar to the A,B,C designations
on the BCxxx series transistors. For instance:

My C1849 has an 'R' in the lower left corner. This corresponds to:

O..... 90~150
P.....120~200
Q.....160~260
R.....210~340
S.....290~460
T.....400~650

These designations are not consistant with all transistors, as I have seen the 'O' to designate 70~140 on the 2SC1815.

The gain indicating additional suffix may have differed depending on the manf. On some of them, the suffix was related to an actual colour marking on the transistor (I've seen/have some old Germaniums marked this way). That carried over into text (O=orange, BL=blue, Y=yellow, GR=green, etc.--Toshiba?).

if i want something "authentic", i normally buy a bunch of used japanese radios, tape players, car radios etc from the 60's and 70's and reef out the all the transistors. dirt cheap and fun.

I like using MPSA18's in Ross clones so that could be another option to ponder.

You can make things cleaner with better caps & such
so if one thought older " authentic " parts may make
it grungier and period of the 70's i can see that ,
slower opamps , but who would use a 741 ?
although in trying to replace one in a dist box , the
" better " one sounded horrible thin & bright .
maybe for something unity gain , there's nothing to be gained
so it gets to be like the Eric johnson debate
if there's a difference , is it enough of a difference
to make a difference [ in perception ]

Comp On !

i don't actually give a crap about what i put in my fx, old or new parts. i mostly pull stuff out of old equipment as something to share or do with my old man. we both sit there with soldering irons talking complete rubbish, he mostly tells me vietnam war stories.

i was only suggesting that if someone wanted, or was hell bent on "authentic" parts, perhaps one of the easiest places to look was in old equipment.

i wasn't trying to preach old is best. i actually posted in the fuzz face discussion somewhere that i've pulled heaps of those blue philips electrolytics and that they are crappy and leak.

anyway, i was only trying to offer help to another forum member.

rhandy gaye wrote: i was only suggesting that if someone wanted, or was hell bent on "authentic" parts, perhaps one of the easiest places to look was in old equipment.

That is an excellent tip for someone with access to surplus equipment.

I was a drummer in my youth. I played guitar over the years, but it was not my main passion.
That has changed over the last decade. I love guitar now. But have only purchased a few pedals
over the past few years. I've made many more than I've purchased. I don't own any 'real' classics.
I do have some reissues, but that's not the same thing. It's much more enjoyable (and affordable)
to create a classic. By 'classic' I mean...all ceramic caps (if that was the original build), no input/output
resistors, no true bypass, no LED, etc. This allows all the noise, hiss, signal drop, pedal incompatibility
issues, et al to become apparent. The main reason to do so, for me, is to experience what my favorite
guitarists of yesteryear had to go through to achieve their 'sound'. Building 'authentic' pedals is just
a fun experiment for me. If I were building pedals to stock my 'on stage' pedalboard, I would build
each pedal with the ideal of getting the best sound possible from it, whatever that might entail. I've
heard that David Gilmour asked Pete Cornish to build him a pedalboard to alleviate the noise problems
that he was experiencing with his, now famous, pedals. Still, while somewhat frustrating, it is fun
for me to connect my homemade 'authentic' muff, power boost, flanger, and delay together and
attempt to get Comfortably Numb to come out.