freestompboxes.org

Guys I realy need some help... I think that with this all information that we have now and breadbording a little we can do something usable. If all major components are in the upper side more than 60% of this circuit are reveled.

This went from the owners site, a summary of how it works:


There is one dip-8 through hole mount IC that I have any Idea what it is: I don't think that it is a single or dual opamp as 4558 or another, the others components in the bigger surface pads are tantalum caps and the smaller pads are resistors and ceramic caps in the image below:

Don't know if this will help... I've only seen the terms Pre- and De- Emphasis associated with RIAA equalisation in phono preamps. Given the vintage of the original, it makes sense to me that Tape and/or Vinyl hifi circuit techniques would have been used.

Pre and De-emphasis can be as simple as a CR network giving treble boost on the way in to a circuit and a corresponding CR circuit giving treble cut at the output of the circuit. It's no great magic (forget RIAA by the way - the frequencies aren't interesting for guitar). I use exactly this approach to improve the signal to noise ratio of hissy pedals! It really helps with BBD Flangers and Chorus circuits.

the long search schematic... Schaffer Replica ....

I had one of these in for a new DC socket. I did the repair while the owner was waiting so not much info.

I did notice that the I.C. labeled as the booster has the number C042 but thats all i noticed.

Hi there all!

Dries from Solodallas here, I did (still doing!) the engineering on all the products. I actually made that block diagram drawing !
Not so easy to figure out - it was a pain for us and we had the original systems ourselves (not the schematics). It's a complex sound byproduct of a complex system. So, good luck

Getting close to the original systems was really a PITA. Over time in design stage a lot of tweakings were done to improve it further;

Ps anyone wanting one of our praised products... get in touch with us! Will give you a great deal'

mictester wrote:Pre and De-emphasis can be as simple as a CR network giving treble boost on the way in to a circuit and a corresponding CR circuit giving treble cut at the output of the circuit. It's no great magic (forget RIAA by the way - the frequencies aren't interesting for guitar). I use exactly this approach to improve the signal to noise ratio of hissy pedals! It really helps with BBD Flangers and Chorus circuits.

There's some app notes here in the pdf the last examples are of companding with pre and de-emphasis. Looking at the pedal it would seem the input pot is a input trim associated with the smd opamp and the output is associated with the dip 8 opamp... I'm sure they'd buffer that compander... I don't see the "optical" limiter in the pedal version. The replica guy talks of one over at the les paul forum. Just got caught up in the web form a rig rundown on you tube and ended at this wireless unit and the replica..

mojah63 wrote: I'm sure they'd buffer that compander... .

Maybe a sallen key low pass filter:

EddieTavares wrote:

mojah63 wrote: I'm sure they'd buffer that compander... .

Maybe a sallen key low pass filter:

[ Image ]

In the application notes 1/2 of an opamp is used for pre emphasis before compression and the another 1/2 is used to de emphasis the expdander. Now could you do the pre + de emphasis just with passives... and is there enough passive components around that compander? Or maybe used the 1/2 of the 2nd op amp to de emphasize You need to account for the input gain control here. One trace goes to to the non or inverting input of 1/2 of the op amp. I can't see the pin 1 orientation mark in the pict. I only see two op amps and a compander on that board. So they are very limited on what they did actively. They also have an output boost, so there's probably 1/2 of an opamp too.

I believe that we reveled almost all about this gadget but, let me think a bit:

If I get the guitar signal with enphasis in the highs, compress, de-enphasis the highs and expand the signal, I'll probably have almost the same signal what I had in the begin, nothing special, there is tons of wireless systems that does exactly this

Angus set his amp to have an overdrive and set the transmitter/receiver to boosts its overdrive. Almost all guitar players do the same with a booster pedal like ts9 that is a mid boost, if I use a linear boost like lpb1 or mxr microamp to boost a marshall amp we have harsh highs and blured basses but if I use the same in a Mesa boogie it sound great.

Ts9 enphasise mids about 500 hz, Evh had used a eq pedal to boost mids about 800 hz, Brian May boosts 1.2 khz and I believe that svds isn't just a expander, It enphasise something between 300 and 500 hz, the question is: how? The answer is in filters I believe.

EddieTavares wrote: Angus set his amp to have an overdrive and set the transmitter/receiver to boosts its overdrive. Almost all guitar players do the same with a booster pedal like ts9 that is a mid boost, if I use a linear boost like lpb1 or mxr microamp to boost a marshall amp we have harsh highs and blured basses but if I use the same in a Mesa boogie it sound great.

The Rig Rundown (PG Premier Guitar) was Angus that I saw on you tube. He sets all his Marshall's, and there were at least 8 super leads, the same bass-3 Middle -3 Treble 2-3 and presence at 1 Using 4x12 25W greenback loaded cabs and a 2x12 iso cabinet for FOH. He had the bigger $1400 version of the gadget that his tech said is used on a few songs. His amp setting don't chop 800-1K anyway if you look at it in Duncan's amp tools. The gadget is basically limiting the frequency response and squashing the signal a little even though you are expanding ( it's never prefect ) it later, then lastly boosting it. I'm not a huge Angus fan but it's an Interesting gadget, but not for $400...

I bought some ne571 and I breadbord this components a little and it works (a little too). I have seeing a lots of schematics that uses ne571 such as delays to understand that pedal, If something usable come up from this scratch It would never be a clone so forget about the values, every single value could be wrong.



That part in the brown box Is the part that I have tried to understand, I know that is a signal booster with treble cut, I thought that It is a 741 inverting opamp but what is that cap in the pin 8?

The input impedance is low because in the I read that it is about 50k, I believe that this is some of that secrets to smooth some frequencies, sounds strange in the pedal world.


Tnx

why 741 ? could it be a ne5534 ? that could be a compensation cap between pin 8 and pin 5. I would say, you are wondering in the dark without the back side of the pcb.

karul wrote: I would say, you are wondering in the dark without the back side of the pcb.

There is some pictures of the big one that shows no components in the dark side, I believe that they do It in the smaller one.

maybe there's no components, but there must be some connections (traces)

karul wrote:maybe there's no components, but there must be some connections (traces)

Perfect, you are all correct, but those connections aren't too hard to suppose, the ne571 is used in the same way in almost all applications and the other circuit portions are two busters, one buffer between the compressor output and the expander input, pre/de-emphasis.

I'm breadboarding this circuit, this preliminary circuit above sounds similar as I've listening in the samples on the internet but without the same amount of gain, I tried to increase the gain in both sides but it brings a terrible noise or just doesn't work.

Tnx

Not verified, but it's a start.

What are R15 and R17 for? No Capacitor vor IC1B? C3 is a little small. No RC-Filter in the supply!

D3????

underwood wrote:What are R15 and R17 for? No Capacitor vor IC1B? C3 is a little small. No RC-Filter in the supply!

D3????

He's just posting a basic idea from looking inside one.....not something that is verified

My attempt, not verified yet.