Tonewise upgrading the SY77 to SY99 specs

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.
baz99
Newbie
Newbie
Posts: 96
Joined: Sun May 25, 2014 9:19 am
Location: Europe

Re: Tonewise upgrading the SY77 to SY99 specs

Post by baz99 » Sat Jul 28, 2018 6:36 pm

Thanks for summarizing the changes, it's much clearer to me now what you did.

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Sun Jul 29, 2018 7:40 pm

No problem.
Herrare umanum est.

User avatar
Yekuku
Active Member
Active Member
Posts: 605
Joined: Tue Nov 18, 2008 11:29 am
Gear: dk'tronics speech synthesizer :P
Location: Greece

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Yekuku » Mon Jul 30, 2018 1:12 pm

Hi Mooger5,
thank you for sharing your opamp adventures, it is an interesting read.
Unfortunately I dont have a SY-77, so there is nothing special that i can contribute.

As I see , the TL072 uses less current than the 4558, so there will be no extra load on the PSU.
What about using higher spec opamps like the MC33078 or the LME49720, do you think that there will be any obvious improvement ?
Last edited by Yekuku on Mon Jul 30, 2018 11:58 pm, edited 1 time in total.
It is all about sharing...

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Mon Jul 30, 2018 10:47 pm

Hi Yekuku, here are some notes based on my findings that I should have posted a few days ago.

Most if not all FET input opamps are more efficient than the BJT types, but at these low levels I think current demand is not going to influence sonics very much. Differences between opamp types are far greater than their power consumption. The TL072 being FET input presents a higher impedance to incoming signals than the BJT RC4558.
Also the slew rate of the 072 is closer in spec to the M5238. Close, but not equal, and I´m counting on it: Higher slew rate means faster transients to me, and faster transients means improved high end response. AS I noted, the SY99 has an extra filter stage between the Sample and Hold and the output stages. This extra stage adds a steeper curve so it serves to better filter out high frequency noise from the DAC and all the switching from the S&H (note the DAC is monophonic and it has to provide four audio channels. Compare that to a higher end K2000 which uses a stereo DAC for every two channels. No multiplexing required). So the extra filter stage was needed in the SY99 due to the higher slew rate of the M5238. Since that stage is absent in the SY77 (due to the poorer high-frequency response of the RC4558 employed), IMO using the TL072 represents a good compromise.
Without that extra filtering, an M5238 in an SY77 could let high frequency garbage pass to the audioband by means of intermodulation distortion, resulting in a less than transparent sound, which would be exactly the opposite of what I´m trying to achieve eheh.

There´s an exception to all of the above, and that is the use of the NE5532. It´s BJT rather than FET, so any improvement based on that difference is lost. It´s also a current hog, at 8mA vs 3mA for the RC4558. Again any improvement due to better efficiency is lost. However the PSU of the SY77 is quite hefty. I think it can stand the waste of a mere 48mA.
The improvement is all in the low noise and the midrange, where the music is. The RC4558 sounds quite grungy and dark when compared to the NE5532. It´s all to do with what you want your synth for, I guess.
I couldn´t hear any difference in the previous tests because of the audio routing. You really have to replace ALL the opamps, not just the L+R channels.

Regarding the new opamps, in this specific context that is upgrading the 77 to 99 specs, I personally don´t see a point in using something audio related that was manufactured after the synth you´re trying to improve went out of production. If you want a synth from a certain vintage, it´s because there´s something about the sound that inspires you, and for whatever reason. So use components that were contemporary, I say. Now to mod it with modern parts... then why not get a modern synth in the first place?
I tried replacing the RC4558 with the NE5532 in the output section of the Moog Rogue and the difference was very noticeable. It´s capable of more timbral subtleties than you´d think. But the Rogue was made in 1981 and the 5532 in 1985. That synth wasn´t designed to sound like that. In the end I decided for a JRC4558 for the extra OOMPH :)
Herrare umanum est.

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Mon Jul 30, 2018 11:16 pm

It´s worth mentioning so far the differences are not night and day, rather 'dawn and day', which means they´re kinda subtle. There´s a definitive improvement but I´m aware to some upon hearing it this might be an excercise in futility.
I don´t have an SY99, I just hear better tone in all those demos. I already asked Knolan if the differences could be due to the FX. No reply so far. If there is an improvement in the dry outputs, then using the M5238 throughout on the SY77 can be done, by DIYing the extra filter stage. Simple circuit, a dual opamp and a couple of resistors and capacitors. Child´s play. The only problem is to disassemble and reassemble the synth every freakin time. There´s a limited number of times I´m willing to mess with the PCB connectors as I don´t really want to stress those solder joints.
Herrare umanum est.

User avatar
Yekuku
Active Member
Active Member
Posts: 605
Joined: Tue Nov 18, 2008 11:29 am
Gear: dk'tronics speech synthesizer :P
Location: Greece

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Yekuku » Tue Jul 31, 2018 11:46 am

Thank you Mooger5 for your informative insights, interesting ideas you have there.
I havent thought that higher slew rate could be a problem, and that lower slew rate could mask "noise artifacts" thus producing "better" output.
If I understand you correctly, hopefully the TL074 are not fast enough ( as the M5238), so they will "filter" the unwanted noise produced by the DAC / S&H, thus there will be no need for the extra filter stage, right?

Haha! I liked the moog rogue story about preserving the vintage character. Once I have spent months of work to modify a sh2000 only to realize when i was done that I had to preserve its original character and removed all the mods.

I am having trouble comparing different op amps as I am not able to hear subtle changes in sonic quality, after experimenting with synths all these years my hearing is not the best . the subtle differences that I have heard was mostly in distortion pedals that were using old/slow opamps , faster opamps sounded different but in most cases not better.

It would be great if you could post recordings made with both original and replacement opamps, so that we can try and tell the difference.
Did you use a spectrum analyzer to compare the output from the opamps, did you notice anything special ?
I couldn´t hear any difference in the previous tests because of the audio routing. You really have to replace ALL the opamps, not just the L+R channels.
Do you mind explaining why?
It is all about sharing...

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Tue Jul 31, 2018 9:09 pm

Yekuku wrote: If I understand you correctly, hopefully the TL074 are not fast enough ( as the M5238), so they will "filter" the unwanted noise produced by the DAC / S&H, thus there will be no need for the extra filter stage, right?
Yep.


I am having trouble comparing different op amps as I am not able to hear subtle changes in sonic quality, after experimenting with synths all these years my hearing is not the best . the subtle differences that I have heard was mostly in distortion pedals that were using old/slow opamps , faster opamps sounded different but in most cases not better.
Pff same here. Now that I´m in my early fifties I think I´ve started to long for the high frequencies that I can´t hear anymore :( . Maybe that´s what´s going on here. I should probably just focus more on the music instead.
It would be great if you could post recordings made with both original and replacement opamps, so that we can try and tell the difference.
Did you use a spectrum analyzer to compare the output from the opamps, did you notice anything special ?
TBF I thought no one would care for this topic so didn´t bother to make any recordings. By I just finished a couple of examples using the SY77 modded with the TL072 and the TG77, unmodded.
I couldn´t hear any difference in the previous tests because of the audio routing. You really have to replace ALL the opamps, not just the L+R channels.
Do you mind explaining why?
It´s already explained a few posts above. It´s kind of confusing. I might try to explain it a little better later.

The audio examples are probably too long. Both use the same settings on the synths, the audio interface and even the same cables.It´s my personal page so I did them a bit "artistic". Aquavox is one of my favourite presets. No added FX.



Herrare umanum est.

User avatar
Yekuku
Active Member
Active Member
Posts: 605
Joined: Tue Nov 18, 2008 11:29 am
Gear: dk'tronics speech synthesizer :P
Location: Greece

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Yekuku » Wed Aug 01, 2018 7:25 pm

It´s already explained a few posts above. It´s kind of confusing. I might try to explain it a little better later.
Well this feels embarrassing, sorry I did not get that right.
I am not familiar with the SY77 schematics, is it due to channel 1&2 audio routing via switching jacks , right?

I just heard your examples and the difference is night and day !
I have no experience on the SY77 or the TG77, is this huge difference only due to op amps replacement?
I am amazed. :shock:
It is all about sharing...

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Wed Aug 01, 2018 11:10 pm

Yeah the difference is quite pronounced in the loudness and the frequency extremes, isn´t it? The more I listened to the examples the more I noticed it. This is not one of those "brand X vs. brand Y" shootouts so the levels weren´t matched on purpose. The loudness increase just by swapping opamps is certainly due to the higher input impedance of the 072. Less signal losses between stages. Better SNR, better dynamics, apparently better everything.
However, I do find the TG pleasant to listen to, quite musical. It may sound more tamed in comparision, but the SY now also sounds a tad unpredictable to me...

As for the outputs it´s alright, it sounds confusing. I´ll explain it later.

Cheers.
Herrare umanum est.

User avatar
madtheory
Supporting Member!
Supporting Member!
Posts: 5142
Joined: Mon May 01, 2006 12:45 pm
Real name: Tomas Mulcahy
Gear: Flangebeast Mk1, Plonkotron, Morovdis Arpeggiator, Maplin My First EQ, Jeff Wayne Thunderchild rack, Thermostat, Buck Owens' Moog.
Band: Minim
Location: Cork, Ireland
Contact:

Re: Tonewise upgrading the SY77 to SY99 specs

Post by madtheory » Thu Aug 02, 2018 7:07 am

It sounds to me a bit like the difference between a hardware Korg M1 and the plugin. It's cleaner and more detailed. Nice work!

User avatar
Yekuku
Active Member
Active Member
Posts: 605
Joined: Tue Nov 18, 2008 11:29 am
Gear: dk'tronics speech synthesizer :P
Location: Greece

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Yekuku » Thu Aug 02, 2018 11:54 am

Damn it man, now I am GASing for a SY77!
It is all about sharing...

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Thu Aug 02, 2018 11:07 pm

madtheory wrote:It sounds to me a bit like the difference between a hardware Korg M1 and the plugin. It's cleaner and more detailed. Nice work!
Thanks madtheory. I do trust your ears.

I still like the unmodded version. While it´s no slouch in the dynamics department, I like it how it sounds naturally compressed, against the modded one. With the latter, crescendos just go on forever, to a point that seems out of control. I think some outboard gear will be in order.
Herrare umanum est.

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Thu Aug 02, 2018 11:25 pm

Yekuku wrote:Damn it man, now I am GASing for a SY77!
Well, the GAS is justified, it´s an epic monster synth. I would sell you mine if it wasn´t for the distance.
As you may know I bought it just "because it was there" and it was really cheap. Someone on the local market will make a good deal because I can ask for the current price despite all the improvements and still make a deserved profit because I payed so little.

If you intend to do the mod, then the TG is much, much better to work on :o
Herrare umanum est.

knolan
Supporting Member!
Supporting Member!
Posts: 484
Joined: Wed Jun 14, 2006 1:42 am
Location: Dublin, Ireland

Re: Tonewise upgrading the SY77 to SY99 specs

Post by knolan » Sun Aug 05, 2018 4:52 pm

Hi Mooger55,

I wonder if you could sum up / summaries where you're at with this project, and whether the mod you propose could be implemented with certainty on SY77s to slightly improve their fidelity? As it happens, I have 4 SY77s and 2 TG77s and access to one or two engineers who could comfortably do this modification for me; so I'd certainly consider it on one to start with.


In particular you posted two audio examples - one of a moded SY77 and the other of an unmoded TG77 - and is this mod (using the TL072 I believe you mention) one you're happy with yourself, or is that an interim experiment?


To answer your earlier question as to the differences I've noticed between my SY77s and SY99s, the SY99's just seem a tad 'sharper' - kind of what you demonstrate here - but I haven't done any 'scientific' comparisons- I just noticed this slight difference over the years when playing the same program over each one.

So with a view to improving the fidelity of at least one of my SY77, I'd be delighted to try this mod on at least one, if you were OK with that? To that end it'd be very helpful to have a kind of to-do list on the number and kind of components to access, what boards to affect and so forth. I realise a lot of it is in this thread, but just for safety it'd be great to see your latest definitive steps to affect this modification. Happy to make a donation via paypal by the way.

Thanks,
Kevin.

Mooger5
Expert Member
Expert Member
Posts: 1459
Joined: Tue May 06, 2008 5:11 pm
Location: Lisbon

Re: Tonewise upgrading the SY77 to SY99 specs

Post by Mooger5 » Mon Aug 06, 2018 1:54 pm

Sure. In a few days. This is not a good time of the year.
Herrare umanum est.

Post Reply