Soundskulptor STS stereo tape simulator

[Holger]

My version:

White powder coated front panel engraved by Frank/NRGRecording, case is from modushop.
JLM Meter Buffer and AC/DC. Volker's broadcast bypass PCBs.

 

[blue_lu]

holger, how do you like it? care to post some samples?

 

[Holger]

It's a special but useful device, especially for the price.
Currently I don't even have time to work in my studio, so no samples from me for the moment, sorry.
IIRC there are some sound examples flying around.

 

[baadc0de]

So, we've seen a stereo... a quad... what about an octo tape simulator?

Well, here she is:

This was easy to get together electronically, and a major pain to get together mechanically - no fault to sound skulptor though, JP was ace with my questions and provided me with a new set of switches after a few died at soldering.

I like what it does.. I'm hoping to tracking drums with it soon. Should be nice

 

[Spiritworks]

Nice. You should make those cases/front panel available.

 

[Hank Dussen]

What are these 'half' holes?

 

[baadc0de]

The "half" holes are an improvement left for some day when I'll take a crack at it. Basically it's a 50% wet/dry mix enable disable toggle. In my testing of the STS I found I liked what it does sometimes in a half-half mixture more than in 100% wet. I first wanted to have a wet-dry pot, but that would eat up more space and there's not a lot of it as it is.

I'll be sure to get a PDF up if anyone wants it, but this really isn't comfortable for 2U, I would really recommend 3U. It's really tight and actually doesn't have enough space at the bottom to clear all the contacts I think.

 

[pietro_moog]

so, guys, how it sounds?
this thing seems to be a direct competitor to Portico 5042.
i heard some people comparing these and they say:
- the lack of transformers is noticeable, Portico is way smoother
- there's an opamp instead of a discrete circuit for gain stage. the sound is weak.
- the inductor curves are not-so-right

they says it sounds more like distortion than tape
is that true.
can this thing be subtle and nice like Portico?

 

[baadc0de]

I can't compare the two as I don't have the portico. It is a distortion box too and I doubt that it's emulating true tape sound, however, its saturation process is not useless at all. If you push it really hard with vocals at 30ips, you will get excessive sibilance distortion, however, set it to 7.5 and it reinforced and smoothed a weak, sibilant rap vocal - not subtle at all and definitely useful. I think it's better than plugins for what it does, however I'll save my true verdict for tracking drums, which is what this has been bought and built for. I hope other people can chime in and expound on the matter, it would be interesting to hear what others think about it.

 

[Tubefreak]

Currently a modified version of the STS is on my desk. I'm gonna build a custom case for it and then do some final tests and post the results here. A short list of some of the mods: in/out transformers (Neve, Pikatron), fully independent switching of the voicing and the coils, added voicings and coil options, (partly) bypass option for the diodes (to get coil saturation without diode limiting), changeable low pass filter, improved PSU, etc.

The stock version sounds good! Easy to build, well documented and more then great support! Sound on Sound did a side by side audio comparison with the Portico, but unfortunately the files are only available for subscribed clients    But they liked it a lot too.

Best upgrade for the STS imho is to bypass the diodes or stick a resistor in front of it. This decreases the limiting of the diodes and adds life to the saturated sound. The low pass filter could indeed be improved too, it's starts around 17khz and goes down sharply. If you are gonna build one, recalculate the low pass filter in the end with the inductors at 22khz or even higher.

Maarten

 

[baadc0de]

Having done all these mods, how much do you think the unit improved?

 

[Tubefreak]

Transformers = +30% - this improved the overall sound quality, not must have but still very fancy
Diode bypass switch = +50% - this greatly improved the dynamics when saturating, must have imo
Extra voicing (9 in total) = + 50% - the 6 extra voicings offer a greater variety of subtle voicings, great for mastering and 2buss work
adjusted low pass filter = +10% - not a must have at all, just nice to have.
improved PSU = +25% - mine had some hum, with more cap stabilisers this was gone

In total +165%   ;D

 

[baadc0de]

Transformers = +30% - this improved the overall sound quality, not must have but still very fancy
Diode bypass switch = +50% - this greatly improved the dynamics when saturation, must have imo
Extra voicing (9 in total) = + 50% - the 6 extra voicings offer a greater variety of subtle voicings, great for mastering and 2buss work
adjusted low pass filter = +10% - not a must have at all, just nice to have.
improved PSU = +25% - mine had some hum, with more cap stabilisers this was gone

In total +165%  ;D

Well, that sounds like something I must do. It would be just one stereo unit first and see how good it works from there..

I already have a 3rd party PSU in there, so no hum

Could the voicings be done on a rotary switch? Very interested in how you did the diode bypassing.. I feel the STS is a bit too constricted indeed, well, that it could use some limit bypassing.

Regarding transformers, you just bypassed the in/out balancing done with THAT chips and spanked some 1:1 transformers there?

Maybe I could do this as an 8 channel 3U unit. Hmm

 

[Tubefreak]

Imo the stock sound of the in/out opamps are fine. I added the transformers to the whole unit without removing any of the other parts. If I would start from scratch, then this would certainly be an option. But I doubt how much difference it will make, it's a colour box after all.

In my unit for each channel I'm gonna make two rotary switches and an on/off for the low pass.
voicing = 9 steps, 3 decks
limiter (=diode) = 5 steps, 2 decks
low pass = SPDT

The voicing switch:
Deck one - Coil H1
1. H1 coil not connected
2. H1 coil connected to ground through an 24R resistor (less bass cut)
3. H1 coil connected to ground (linear saturation)

Deck two resistor R30
1. not connected
2. 120R
3. 200R (less treble cut in 7.5 ips)
4. 120R + 200R parallel
5. 4R (less bass cut in 30 ips)

Deck three negative feedback
1. off
2. 75KR between TP3 and D1

total voicings
1. 7.5 ips (bass boost, high cut)
2. 7.5 ips + 200R (bass boost, flat high)
3. 7.5 ips + H1+24R + 4R (slight bass boost, flat high)
4. 7.5 ips + H1+24R (slight bass cut, slight high boost)
5. 30 ips (bass cut)
6. 30 ips + 4R (flat !!!!!)
7. 15 ips (smile EQ)
8. 7.5 ips with 75K between TP3 and D1 (smile curve)
9. 15 ips + 200R (high boost)

Limiter:
1. D1+D2 off (for no diode clipping = more coil compression and more open sound)
2. D1 on with 2k2 resistor to ground (for assym. soft clipping)
3. D1 to ground (for assym clipping)
4. D1+D2 on with 2k2 resistor to ground (for symm soft clipping)
5. D1+D2 on (for sym clipping) (=stock)

On any stock STS you can cut the leg of the diode D1 and add a switch in between.

low pass switch
1. stock
2. 45R from crosspoint R38/R39 to R40.
this changes the low pass filter, but also adds loads of gain and gives it a more 'modern' overall voicing. Maybe I'll pair this with a change for resistor R42. At 1k6 it offers more gain, which could be a good setting for the stock low pass filter.


Maarten

 

[TomWaterman]

I hadn't realised how similar this was to seomthing I have a colleague working on, especially the diode clipping with the zener stage.

What are the coils in this thing, are they custom? Can we buy them separately?

Mods sound excellent. The SOS clips are still available online even for non-subscribers btw.

-T

 

[Tubefreak]

What are the coils in this thing, are they custom? Can we buy them separately?

There is no identification on them, nor does the schematic make clear what type they are. But if you ask Jean-Pierre, I'm sure he'll let something know. They are in the equation to simulate the recorder/player heads of the tape machine. When you bypass the diodes D1 and D2, then all distortion comes from the coils! Coil leg from H1 which goes to SW1a has a big influence on the sound, both EQ wise and how the distortion reacts. Imo this is the most important part of the STS.

BTW the problems I had with the PSU, was not caused by the standard PSU of the STS. I went for the kit where you have to make your own PSU.

 

[Jonkan]

I like mine stock just fine! I bought the whole kit cause i felt lazy that day  ;D
It sits on my 2bus when doing foh sound most of the time. Im using a digital console, and i find this helps even out the all too fast transients you can get with digital desks.

Could be fun to hear it without diode limiting though. I might put a switch on the back or something.

/J

 

[TomWaterman]

Also diode clipping is Zener here, thinking some interesting clip sounds could be achieved by running germaniums with some leds to up the threshold or perhaps mostfet body diodes etc.

I have been playing with a very similar idea but with small core transformers ala my Fatso.

-T

 

[baadc0de]

Warning: Thread necromancy..

So I'm still very busy and haven't gotten around to modding my STS, but I feel the time may come soon, so maybe we could discuss the mods again a bit. I have decided to use the "half" switches on my octo sts to be diode defeat switches and build a quad unit at some point with all the mods like carnhill transformers, 9-position tone rotary, maybe even some switchable germanium/ordinary diodes and limiter switch, but speaking of that..

Tubefreak:

did you implement the tone and limit rotaries?? Could you maybe make a diagram of the limit switch for us schematic-reading-theory impaired?

Cheers,
B.

 

[Tubefreak]

Hey B.

: my cute little girls keep me busy, so it's still in a rough stage.

If you look at my post, you'll need a three deck rotary switch. For each deck is described what the functional switching should be. In the list of 'total voicings' there is an overview of which combinations between the three decks is needed to get the voicing. Between the brackets is the description of the sound.

Check the original schematic to see what the standard voicings are for 7.5 15 and 30 ips, is a combination of the H1 coil and resistors R30/31 iirc.

It's a bit a tricky to get it right, but should be possible.
Maarten