Boss SD1 Circuit Explanation

[01downer]

Hi everyone

I came across a site the other day that layed out and explained what every single component on the boss sd1 does and what tonal effects its given roles are
I thought i saved it but didnt and now i cant find the site

Does anyone know what document im talking about and possibly be willing to share it with me? Or even just a link explaining exactly what every component does in dummy terms i.e. r6 will increase or decrease gain. C2 and c3 will affect the bass response etc....


Thanks everyone!

[GibsonGM]

Post the schematic if you can, Downer!  That will get you more action on this thread...

[StephenGiles]

https://www.youtube.com/watch?v=FETtHV-2Ndw   !!!

[baklavametal]

this maybe?
http://www.electrosmash.com/tube-screamer-analysis

[01downer]

Thank you for the responses everyone. I genuinely appreciate it.

The site i seen and am still searching for was just a standard stock current taiwan sd1 that literally listed every component on the circuit and described exactly what it was , why it was there , the role it played and the effect it had on the tone (if any at all)

It was basically as dummy proof as possible.

It was basically just a list, for example:
R6= governs amount of overall gain
C2= plays a role in bass response (also works in conjunction with r6)

The majority of you fellas know way more about this stuff than i do so i was just hoping someone on here knew what site i stumbled upon. Or if not, knew of another site with that information on it?

Thanks everyone

[thehallofshields]

What you have to understand is that the SD1 is Boss' take on perhaps the most popular pedal out there, the Ibanez Tubescreamer. The differences between all of the Tubescreamer variants out there are subtle.

An exhaustive list of each component and a description of what it does is the wrong approach. Useful for modders but not helpful in understanding the circuit.

Better is to break the circuit down and understand each section of the circuit like a block diagram first, and then understand the function of teach individual components.

If you're modding an SD1 in your possession, you'll be wanting to make minor changes to the Clipping and Tone Control sections, and leave the Power and Buffer sections alone.

A poster here has made a comprehensive article. Don't beat yourself up if its too much to take in at once. Just try to soak up the terminology.

http://www.geofex.com/article_folders/tstech/tsxtech.htm

[j-pee]

A poster here has made a comprehensive article.

http://www.geofex.com/article_folders/tstech/tsxtech.htm

Calling R.G. Keen but "a poster" simply ain't down. Starting with that he posted that "post" at his very own website. And continuing with the fact that it is an article... and furthermore that...


DIY pedal culture is not a junkyard where you can grab stuff.
It is a temple of knowledge, and coolness.

no offense, though..

[ElectricDruid]

I'm sure this isn't the article the OP is looking for, but I've had a go at this too:

https://electricdruid.net/designing-a-classic-overdrive/

This is a comparison of the OD-1/TS-808/SD-1 circuits, followed by a walk-through of building something very similar yourself, including a few tweaks and modern overdrive upgrades.

[BJF]

Hi there,

Maybe of use to someone here goes

One could argue that BOSS patented asymmetrical clipping with OD-1. Alledgely the first OD1 s had OP amp buffers- transistor buffers of course draw less current and early BOSS pedals only flashed the LED and only later stayed on or off. BOSS also patented silent switching. At the time Ibanez had a Sonic Distortion that with very little changes could be made into what became the Tube Screamer. The Sonic was similar to distortions at the time such as DOD PreampOD 250 more specifically with two clipping diodes to ground after an OP and advancing Distortion also progressively rolled off bass. It was an OP in non inverting configuration and it had a feedback resistor of 1M Ohm and from inverting input 4K7 via 47nF via 500K C to ground. This was followed by an EQ amplifier with same values as the later Tube Screamer and it could get truely sharp and bright. it had a mechanical foot switch and no LED. However after Ibanez dropped the TS BOSS answered with SOD-1 that was the OD -1 circuit followed by an EQ amplifier albeit with different values and more than twice the boost cut range.
As I recall late 70s BOSS OD 1 was at the local store one year as the store had order from that year's Frankfurt Messe and the following year Ibanez Tube Screamer was also at the store bought from that year's Frankfurt Messe and the SOD1 a year later.
OD 1 is also the first pedal I ever saw that had a lowpass filter after clipping as low as 800Hz! While also highness in the clipping gain at 723 Hz
Ibanez TS of course had a lowpass filter at 723Hz and then boost / cut at 723Hz. Now aligning two bended curves like that either results in a peak or a dip and can never be perfectly flat and when close like this there is a dip and when processing square wave result is no longer square wave but a lot softer.
At the time this type of overdrive changed sound of distorted amplifiers to something more streamlined and the reason that was lies in amplifier eq that generally has lowered midrange to give more treble and bass which wasn't ideal at the time but pre driving with an OD like one of those above partly reduced complexity in the low mids making for clearer chords and putting energy in the midrange making single notes sing: distortion in bass frequencies gives overtones in the low mids and this can cause unclear sound while too much energy in the treble can cause harsh sounds and not enough midrange can cause short sustain. Really this type of overdrive was a great advantage over pushing amps with boosters at a time when many had boosters built into guitars.....  but it took years before I saw anyone running such an overdrive into a clean sound.

Because diodes when they fully clip become low value resistors a peak higher than the forward voltage will pass at gain at gain defined by the forward resistance of the diodes. Specifically for forward voltages around 600mV that is approximately the peak value of a transient of a Stratocaster pick up transients are low enough not to shall we say bleed through whereas  at 1V peak or higher such as with humbuckers transients will be just a bit higher than the forward voltage and yet at low enough level to pass at output at negligible distortion and this results in a sound that is a combination of seemingly clean transients and distorted decay.
Three ways around this are using higher forward voltage or making feedback resistor values really low which will btw cause distortion in the OP amp by loading. OD 1 was considerably better with hotter pick ups due to the asymmetric clipping partly masking that or sue a clipping amplifier that is in inverting mode.
The BOSS Super Overdrive has in addition to the same clipping amplifier as OD 1 a passive lowpass filter instead of the lowpass filter in the feedback of an inverting amplifier as in OD 1 also a boost and cut tone control and while it can get plenty bright still it will soften a square it will also not get as bright as the earlier Sonic Distortion not to be confused with the much later Ibanez SD9

Have fun
Bjorn Juhl
BJF Electronics
Sweden

[bloxstompboxes]

This thread is 9 years old, lol.

[ElectricDruid]

This thread is 9 years old, lol.

Ack, so it is...

BUT NOW IT RISES FROM THE GRAVE AND LIVES AGAIN!!

[GibsonGM]

After 9 years, I just checked out the Bax, and think it might be useful in a booster I want to build 

[Ben N]

Never mind.