something to tame the synth...

[Devo-lution]

the situation:

I'm in a new wave band, so on a certain moment I had this thought "wouldn't it be cool to do bass synth stuff on some songs?". So I bought an analog monosynth. Went for the Oberheim SEM and to be honest... I love it's sound and I'd like to use it onstage.

There's one thing to it that I haven't been able to handle adequately yet: It's output is HUGE. If I connect it to my practice combo, it's 5-6 times as loud as my stingray on the same amp settings.

The synth doesn't really have a volume knob. It does have a section to mix the oscillators. In the manual it says to turn one oscillator all the way up and put the secondary oscillator accordingly how you want to mix them. It says "level control" is preferably done on the mixer you're connecting it to or on the gain stage of the device you connect it to.

...

I have a mixer. On lowest input gain settings it's still driving the mixer into distortion.

When I connect it to pedals, same story. These have volume drops, distorted sounds, etc if I connect the synth to it. My plan was to run it through the "return" of my X-blender and use the blend volume knob to bring it's volume to acceptable levels. That way, I'd be able to run it through my bass amp and switch between instruments using the X-blender. I'm able to bring the volume down, but am still hearing some slight distortion.

The only thing that works impeccably, is running it through my Radial JDI to the mixer.

Is this an impendance issue? Is there a pedal or device to tame it? Should I DI it all of the time? At home, It's a no issue, since I always DI it to my mixer. I haven't figured something out to take it to the stage yet, though.

[judas jedermann]

Have you tried to lower the sustain knob in VCA? Usually it acts like volume in ADSR.

[Devo-lution]

Originally Posted by judas jedermann

Have you tried to lower the sustain knob in VCA? Usually it acts like volume in ADSR.

I'll try it this evening.

[Bish42]

Or stick a compressor after it?

[caeman]

Or use an EQ pedal to attenuate down the signal -15db before your amp.

[Damascus]

Originally Posted by caeman

Or use an EQ pedal to attenuate down the signal -15db before your amp.

+1 to this. You'll appreciate the EQ control over the tone of the synth as well. Compressor would be nice, but this will be your easiest and most useful "fix".

[chromium]

The SEM puts out a line level signal, probably in the 10v peak-to-peak range like a lot of the modular synth gear. Most guitar/bass amps, effects, etc.. are designed to work with low level signals in the millivolt-to-1v range.

A potentiometer wired up as a voltage divider would probably work to attenuate the SEM's signal - in other words, something along the lines of a passive volume pedal.

There's also those Ebtech line level shifters, which are made for this purpose: http://www.musiciansfriend.com/acces...-level-shifter

[Devo-lution]

Originally Posted by judas jedermann

Have you tried to lower the sustain knob in VCA? Usually it acts like volume in ADSR.

Nope, doesn't do it... Has no release by the way. Sustain sets the hold level, but the initial attack is still loud.

Manual specifically says it has no master volume or whatsoever.

@ Chromium:

Thanks, what do you mean by the part about the passive volume pedal. Running the SEM through the volume pedal and that way attentuating it?

I suspected it was line level, but given that it also overdrives my mixer when it's set to "line level input" kinda confused me.

[WalterBush]

Hey there! I play in a new wave band, and ran into the same problem with my MicroKorg. I built a mixer pedal and it solved a huge number of problems. I plug the synth into my bass rig, and run with one DI which made setup and soundcheck much, much faster and smoother. I learned from experience which patches I need to turn up or down, and make heavy use of the volume knob on the front of the Korg.

Here's a link to the pedal, it cost me maybe $20 and a couple hours to build. There are commercial equivalents available if'n you're not so handy with soldering iron, but I suspected them of not having enough headroom for a synth, more on that below:

http://generalguitargadgets.com/proj...-mixer-project

I put the mini-mixer into an mxr-type enclosure, and stuck it on the end of my pedalboard. I also use it to mix the high and low frequencies on my bass, split with an '80s-era Peavey chorus so my effects all affect the high end, and the lows keep pumping no matter what wierd pedal I stomp on.

I had a problem with overdriving the mini-mixer until I used an 18v power supply on it. Make sure any components you use are rated for it, and you'll have plenty of headroom regardless of how loud your synth gets. Short of buying a nice commercial mixing board (which defeated the purpose, I was trying to carry less gear, not more) I couldn't find a solution that I was sure wouldn't distort like crazy.

[judas jedermann]

Originally Posted by Devo-lution

Nope, doesn't do it... Has no release by the way. Sustain sets the hold level, but the initial attack is still loud.

And if you set VCA decay shortest possible, does it help with initial attack volume peak? I guess it is instrument/line level problem like Chromium suggested. I´m just curious.

[crapusername]

Ehx signal pad?

[RickenBoogie]

No solution, but I find it odd that Oberheim would leave off a volume control. ALL my synths have one, and I use a mixer between synth and bass rig. You need some sort of pad, and maybe an eq pedal will do it. good luck.

[Devo-lution]

Originally Posted by judas jedermann

And if you set VCA decay shortest possible, does it help with initial attack volume peak? I guess it is instrument/line level problem like Chromium suggested. I´m just curious.

I'll try this evening .

@ Rickenboogie. It's possible to bring down the volume level if you turn both oscillators only halfway or less in the mixer section. The manual states that you should turn them almost all the way up for optimal performance.

Lehle has some a/b pedals that claim to be suited for high and low impedance signals. Will this help?

[chromium]

Originally Posted by Devo-lution

@ Chromium:

Thanks, what do you mean by the part about the passive volume pedal. Running the SEM through the volume pedal and that way attentuating it?

Yeah - exactly that. That EHX Signal Pad mentioned above should work the same.

If you already have some other pedals around that provide a gain adjustment (like the eqs mentioned, etc), try 'em out before buying something... you might find one that responds better to the hotter signal and works to attenuate it.

[Devo-lution]

Originally Posted by judas jedermann

And if you set VCA decay shortest possible, does it help with initial attack volume peak? I guess it is instrument/line level problem like Chromium suggested. I´m just curious.

It doesn't do much up until the sustain is almost all the way down. Then the volume starts to drop and the sound starts getting really percussive (more drumcomputerish than synthish).

Something that I'm also going to try is to use the oscillator mixer to bring both oscillators and the external input 1 preamp (korg monotribe) to the same volume level as my bass guitar.

Yesterday I brought both oscillators down halfway so that they were about as loud as the korg monotribe and this didn't affect the sound much in my opinion. If this does the trick, I'd only need an AB/Y pedal to be able to switch between bass and synth.

Saturday I'll be running it through the tube amp + 2x15 and see how it sounds at band practice ...

[Devo-lution]

Originally Posted by chromium

The SEM puts out a line level signal, probably in the 10v peak-to-peak range like a lot of the modular synth gear. Most guitar/bass amps, effects, etc.. are designed to work with low level signals in the millivolt-to-1v range.

A potentiometer wired up as a voltage divider would probably work to attenuate the SEM's signal - in other words, something along the lines of a passive volume pedal.

There's also those Ebtech line level shifters, which are made for this purpose: http://www.musiciansfriend.com/acces...-level-shifter

Been searching on gearslutz and found some similar topics of people who couldn't connect their SEM to effects. The SEM is indeed in the same range like a lot of the modular gear. Some people were saying that it's output is about five times as high as a normal line level signal.

Someone compared it to the Moog little phatty and concluded that the output of the SEM is much higher.

My mixer has a maximum input of +6 dBV (1.8 V)... Probably that's why it overdrives.

Solutions they gave on gearslutz were the same. Ebtech's thingies, passive attentuators or ignoring the advice in the manual to turn the oscillators all the way up in the osc mixer section of the synth.

Many thanks, everyone!

[chromium]

Originally Posted by Devo-lution

My mixer has a maximum input of +6 dBV (1.8 V)... Probably that's why it overdrives.

Yeah, for some reason the consumer grade mixers are kinda hit or miss with this. I've been using a modest old Yamaha MX12/4 that seems to provide enough headroom to deal with synth/modular levels, and so it just depends...

If Oberheim states to turn the oscillator levels up all the way it's only because that mixer sits in the signal chain before the filter and vca, and that would yield the best signal-to-noise ratio. It might even have some effect on the overall sound/timbre, but in live use I doubt any of that would even be perceptible.

Originally Posted by RickenBoogie

No solution, but I find it odd that Oberheim would leave off a volume control.

No kidding! I could only guess that it was probably a design compromise, since the SEMs were originally offered as standalone units to augment monosynths like the Odyssey and Mini, and you could just run the output back into the host synth's external input and set the levels there. They were also used as building-blocks in Obie's old polyphonic synths - which did include mixer modules:



Kinda funny that the features and control layout of the SEM is the same now as it was some 30-somthing years ago! I haven't tried it, but the new ones are supposedly drop-in replacements for the old ones.

[Devo-lution]

Originally Posted by chromium

No kidding! I could only guess that it was probably a design compromise, since the SEMs were originally offered as standalone units to augment monosynths like the Odyssey and Mini, and you could just run the output back into the host synth's external input and set the levels there. They were also used as building-blocks in Obie's old polyphonic synths - which did include mixer modules:

Kinda funny that the features and control layout of the SEM is the same now as it was some 30-somthing years ago! I haven't tried it, but the new ones are supposedly drop-in replacements for the old ones.

Yeah, supposedly, you can buy the new one without the case and drop them in old 2, 4 or 8 voices. Scouting your picture I only see a few differences on mine. The added midi interface and patchpanel + the knobs to (fine)tune the VCO's are next to each other instead of on top of each other. Seems like oberheim is also re-releasing the 2-voice + keyboard + sequencer. If I had known, I might have waited for that one .

That 4-voice + mini-sequencer yours? Seems like a great synth!

To be honest, I went for the SEM as my first synth based on reviews and because it didn't have any patch memory (I'm a knobs guy) without ever having heard one. Got lucky, since I've grown to like it a lot. It's quite easy to get into, sounds really nice and the VCF really shines.

[chromium]

Originally Posted by Devo-lution

Yeah, supposedly, you can buy the new one without the case and drop them in old 2, 4 or 8 voices. Scouting your picture I only see a few differences on mine. The added midi interface and patchpanel + the knobs to (fine)tune the VCO's are next to each other instead of on top of each other. Seems like oberheim is also re-releasing the 2-voice + keyboard + sequencer. If I had known, I might have waited for that one .

That 4-voice + mini-sequencer yours? Seems like a great synth!

That new two voice synth will be a blast, especially since it includes patch points for everything. IMO the two voice was always the shining star among the SEM-based polys. It came with that sequencer, which would give you two independent 8-step sequences (each running a SEM), or you can assign the second row (adjustable via the stacked knobs) to control each step's timing. The sequencer module also provides noise and sample/hold sources, which the SEM lacks. In the two voice, the noise source was routed to each SEMs ext#2 mixer input, and the s/h to the VCF modulation inputs. Also, SEM #1's output was split off and routed into SEM #2's ext#1 mixer input - so you could optionally feed one SEM into the other for some massive and/or really strange monosynth sounds.

That four voice and sequencer in the pic was kind of in a derelict state when I got it, and the seq wasn't connected at all. I've since gone thru the entire unit and restored it, and wired up the sequencer a lot like the two voice described above. You can choose to run the first two SEMs via the sequencer, and play the remaining two from the keyboard. It also provides the noise and s/h source to each SEM. There is still a problem with patch storage/retrieval that I need to sort out, but like you I'm not real picky about having that capability. It does allow you to store different settings for each SEM in a single patch, though, for some multi-timbral action at the touch of the button.

Of course, one could just buy a Tetra and save all of this grief! All I can say is - buy new/recent synths, unless you *really* enjoy repairing this ancient stuff (or unless you're loaded and can find/pay a tech to do the work). Especially true for old polys. There's lots of stuff that can go wrong in 'em.

Happy patching!

[Devo-lution]

A small update as to give some closure to this topic:

I still have the Oberheim Sem but it turned into my "studio synth" and is mostly controlled by sequencers. Nowadays, I'm using an Arturia Minibrute as my "Stage synth".

I also got the SEM to work on that same mixer that distorted like hell as described in this topic (this mixer is also my studio: Tascam Portastudio, first version). I just run the SEM through a Radial JDI and engage the -15db and -30db pads. This turns the output into a mic-level signal which is gladly accepted by the mixer. Sometimes I only engage the -15DB switch and then the Radial DI seems to be distorting slightly in a good way.

So... Happy ending, I guess. I've got two synths that I love (the oberheim for it's tone and the Minibrute for being very practical).