modification Optimod 8100A

[wgliradio]

Re: modifacation Optimod 8100A

How was the Vigilante air chain set up? Was it similar to the Aphex Audiophile air chain (Compellor, Aural Exciter, Vigilante, Digicoder) or were there other combinations used??

The Vigilante was designed for use with the Prisms. When I had one, I used with an Ariane, Aural Exciter, Vigilante, Inovonics 705 and a CP-803. It was pretty damn good.

The 8100's HF limiters, unmodified, for all the HF load they can handle, can sound mushy at times. You never had that problem with the Vigilante. It basically is what the Dominator SHOULD have been, it did not pump or suck like the Dominator. The clippers were also very clean and it was super loud.

 

[BROADCAST]

Re: modifacation Optimod 8100A

Hey Bobonthejob,
On card 5,their is no chip behind the clipping control,which chip do you mean?

 

[rrsounds]

Re: modifacation Optimod 8100A

I came to the XT2 game relatively late, about 15 years ago, when I was at Z100 (CE from 1988 to 1996). I tried out (and mangled, er, modified) lots of different processors. One of the things I tried was an XT2 with multiple modifications, as follows:

First, I added in the components to allow control in Band 6. Mr. Orban removed that feature for a good reason: it could sometimes sound very artificial. But, see the following.

I then removed resistors in some of the bands (don't recall which) and even added caps to some in order to slow down the release in all bands to similar, slow speeds. The 'mushiness' and artificiality some associate with the XT2 is, I believe, due to too much limiting activity versus clipping.

The distortion-canceled clipping system in the XT2 was nothing short of amazing, capable of probably nearly 20 dB of drive with low perceived distortion. Using the limiters to carefully feed the clippers was what I was trying to do, rather than using the limiters to create spectral density, which I believe was the intent of the original design.

The final, most complicated mod, and also the most difficult to adjust, was to create individual thresholds for the six limiting bands (in the stock system the thresholds were ganged together on a single control). Since the thresholds were bi-polar, I had to construct a perf board with a variable reference for each of the six bands (accessible from the rear via trimpots) and its inverse, exact opposite voltage, using opamps. The thresholds and input drive were adjusted to give typically between 3 and 7 dB of limiting, sometimes less, depending upon which band you're talking about and which song was playing.

The system was driven by Texars (that had the limiting removed), and the Optimod cards 3 & 4 were replaced with nearly vacant cards (Aphex?) that passed the audio through unmodified to the rest of the Optimod. In essence, I was using the 8100/XT2 almost as a standalone 6-band limiter and stereo generator with only the Texars in front. FWIW, I almost **never** turned up the 'tone controls' in the XT2, but rather used it flat.

At some point i added a dbx compressor (166, IIRC) between the boxes for some RMS 'punch', in an L+R/L-R matrix which also allowed for some stereo enhancement.

There may have been a dolby 740 spectral defacator in the matrix, too, but I don't remember the exact sequence of events. ;-)

Oh yeah, there was always a hint of Yamaha digital reverb, too, before the limiting. Other than that, I avoided additional EQ or sonic enhancement boxes.

I had a home-built composite clipper at the transmitter at Empire, into an Ogonowskified BE FX-50 exciter...

A lot of that went away well before I left in 1996. Wish I had an Ariane then.

Kind Regards,
David

 

[rrsounds]

Re: modifacation Optimod 8100A

I have unpotted all the black modules from the 8100a,and the xt2.
<snip>

Also i have unpotted the "Mr gibbs" module from the Unity 2000 processor.
<snip>

That sounds like a lot of work.

So, now I'm on the edge of my chair.

Are you going to tell us your findings?



David

 

[menotti1]

Re: modifacation Optimod 8100A

david, check your message.got a question fer ya...thanks also,i never care much for the xt at all.loved those texars though...

 

[BobOnTheJob]

Re: modifacation Optimod 8100A

Hey Bobonthejob,
On card 5,their is no chip behind the clipping control,which chip do you mean?

There I go again...relying on my memory. I should have said behind the HF Limiting control on card 6. IC 603 is the chip. It eliminates the HF Limiting & lets the HF clippers carry the load...which they do very well. This opens up the high end...makes it brighter as well as more natural sounding.

A side note...these mods work equally well on the 8100A with or without the XT2.

 

[wgliradio]

Re: modifacation Optimod 8100A

I've screwed with that 4 years ago with another 8100, I don't think the high end is as nice w/o the HF limiters. It's a matter of preference I guess.... to me it sounds too edgy without the HF limiters. The clippers are very efficent, but the whole package sounds better with the limiters.

I have another HF trick that I have to go pull notes on with Card 6 that allows bright highs while leaving the HF limiters to take edge off WHEN it needs it. The Card 6 I was using was an older 6 and I don't know if the same applies to all Card 6's

 

[BROADCAST]

Re: modifacation Optimod 8100A

Granted,the prisms with the 8100 sounded bright,but artificial(some say like trash can lids)!
The problem was that the prisms and 8100 sounded inconsistent between different audio material,also distortion on some midrange forced you to back down on the clipping.
The prisms were very unstable,to me they were over rated.

The xt2 was a work of art,the xt sounded dull due to heavy limiting of band 6,after the early upgrade to alter the thresold of limiting it was better,but still soft sounding.

Strapping band 5/6 on the xt2 was far better,but on some audio,you still wanted band 6 to limit less.

One thing to remember is that the xt2 band 6's clipper is approx -6db from xt2's total output,whereas using the 8100's by itself,the smart clipper sets the hf clip point,less the hf limiter setting.
This is why when using the prisms before the 8100a gives a brighter sound.

One mod for the xt2 is to use a dual opamp and a few resistors and pot,to make a clipper bias offset.
This works by keeping the +/- 1.8v bias with the pot counter clockwise,then turning the pot clockwise,increases the clipper bias to say +/-2.5v,as the opamp circuit is unity gain,thermal bias tracking is still assured.
As Bob Orban explains,raising band 6's clipper threshold increases hf grit,but 1 db less clipping will add more brightness,this would be very similar to the 8200 hf clip control.

Regarding the potted modules,these took my a very very long time to unpot,i have been asked many times how it was done,to this day i have not said how i did it!

I am not sure if Bob or frank would be bothered or not,if i were do divulge!

As we use 50us pre emp here,i was quite suprised how more restricted the hf is using 75us pre-emp and the matching de-emp!

Using the 8200,using the analogue outs with flat setting,i can directly compare switching between 50 and 75us pre-emp,as the 8200 automatically selects the de-emp for flat response,so giving an a/b comparason on the fly!

As i have done numerous mods to the 8100a/xt2,i have catalogued them.
Some people say the tl072 opamp is fine,they forget how many opamps are in series through the 8100a/xt2.
By far the best is the opa2134 opamp for replacement,but with greater power supply demand.
I upgraded the 8100a's supply by several mods,i fitted a alloy plate between and under the pass trannies,and fitted a heatsink on this plate between the pass transistors,then reduced the power supply series resistors(to currnt limit at a higher value),and lastly replaced the 50va transformer with a 100va torroid,with suitable transorb accross the secondary,as protection.
As torroids have low impedance,they can spike the unreg supply on plug in.

This power supply mod allows me to use any suitable opamps without psu going in to shock,and this is with led metered 8100a and xt2!

There are certain key opamps that will make quite a difference,after opamp upgrades the 8100/xt2 is cleaner,no question.

Just one point of interest to me is card 6 ic604/610,this opamp has a fixed gain of approx 28x.
With the opamp(ne5534)having a unity gain slew rate of 13v/us,divided by 28 = 0.46v/us,as this is passing the preemp part of the audio,i would like to see a faster slew rate here.
Changing this for a ad797 here improves the audio,and as the ip impedance is low,the bipolar is preferred here over a fet ip opamp.
I would like to try a bipolar opamp of say 30v/us here!

Changing all 072 filter,and post filter opamps for opa2134's,greatly improves audio detail(and noise).
Some extra decoupling of the cards is also a good thing,i always replace the 100u caps for low esr 105 deg ones,that is a first good start.

As i said one or two 072 replacements makes little difference,but replacing all opamps in the pre and post filter circuits has an additive effect.

I will have to find my list of mods,then post them here.

 

[Parasound]

Re: modifacation Optimod 8100A

Wohoo Broadcast.

That would be great!!


and Unpotting some modules is a lot of work. I've done it with the Texar RCF-1 card, Right after that, i found out that Gentner re-designed it as the RCF-2 card. My RCF-1 had a deffective Master-parc module, but with some help of a RCF-2 i have fixed this.
The 8100, and all of it's replacement cards and Mods, are great hobby items at the moment!!

Great gear!!

 

[BROADCAST]

Re: modifacation Optimod 8100A

Without giving too much away,the mr gibbs module is a smart clipper.
Also internally on the mr gibbs modules output,their is a clipper on the input of a non inverting opamp buffer output!

When you look at the rest of the associated post filter on the Unity 2000's board 8,this would be similar(ish) to card 0,on a 8100a.
The final clipper after board 8's filter also has a clipper,who's bias is derived from the mr gibbs module,this final clipper is to assure any overshoots added peaks,are clipped to the same output of the mr gibbs module.

So roughly speaking,using a 8100a with a pair of prisms,with the hf limiter disabled,would be similar in brightness to a unity 2000,in terms of hf response.

The 8100a remember has bass clipping,and lp filtering,so the bass is more fat.

One of my problems i have had with the 8100a is the false gate triggering under heavy bass with midrage present.(look at the gate light triggering).
This is cured by replacing card 5's r536 from 33k to 100k.
Now when heavy bass line kicks in,the artists singing stays forward more,instead of backing off due to gating freezing the release time,so increasing the master compression falsely.

Now using the 8100a/xt2 is more consistant,especially as you are using the 8100a's dual band as a slow agc(i like release set to 7).

 

[wgliradio]

Re: modifacation Optimod 8100A

I thought you were talking about the 8100 w/o the XT2. Now I understand.

Personally, I always like the 8100 with my multiband stuff before it. Prisms always sounded better surrounded by other stuff to keep them in the zone and with the limiters defeated.

A Compellor/SEP-800/8100-Card 0/Good composite clipper of your choice sounds better than stock 8100/Prisms.

Granted,the prisms with the 8100 sounded bright,but artificial(some say like trash can lids)!
The problem was that the prisms and 8100 sounded inconsistent between different audio material,also distortion on some midrange forced you to back down on the clipping.
The prisms were very unstable,to me they were over rated.

 

[Sgeirk]

Re: modifacation Optimod 8100A

I would personally love to hear one of these heavily modded 8100's y'all are talking about.

 

[Robert Bass]

Re: modifacation Optimod 8100A

I would personally love to hear one of these heavily modded 8100's y'all are talking about.

I am perssonally amazed that you guys are doing all of this stuff in the first place. ;D I always liked the 8100 as is, with ziltch in front of it. But then again, that's because I like natural over loud.

Here's a question though... With all these mods, does the source material play a role? I would suspect it does. IIRC most stations were using carts and records as source material, way back then. When it came to mastering the carts, there was usually some form of audio processing that occured, and depending on the cart type used vs how the recorder was callibrated, things could get interesting. If modified Orban 8100 gear like this is still used today, how does it handle the already clipped audio on most of today's horribly mastered CD's?

R

 

[Sgeirk]

Re: modifacation Optimod 8100A

An 8100, all by itself falls apart, in comparison to it's digital brethren.

With a real good agc out front, like an Arianne, they sound a little more distorted, but can come close in the loudness dept to all but a couple digital boxes.

 

[Robert Bass]

Re: modifacation Optimod 8100A

An 8100, all by itself falls apart, in comparison to it's digital brethren.

With a real good agc out front, like an Arianne, they sound a little more distorted, but can come close in the loudness dept to all but a couple digital boxes.

Not sure about that. I liked the sound of our 8100 by itself, compared with the 8200 by itself. But I suppose a by itself 8100 against another by itself processor from another company, might fall apart. I could understand that.

R

 

[BROADCAST]

Re: modifacation Optimod 8100A

The 8100a barfoot can sound excellent on certain material,easy listening etc.
On some old thin sounding tracks,the xt2 can dynamically equalize the sound with great success,one track for example is Lisa Lisa and cult jam,head to toe.

Some time ago i recorded from the tuner a track called Roxette queen of rain,and put it on http://161.53.122.19:8080/ it is still there!

User = processing
pw = clips

I am sure you recognise the link,i forgot who was generous enough to allow recordings to be uploaded there.

The Roxette track was not processed for max loudness,but the recording has a nice clear detail to it.

Regarding todays hyper compressed material,this of course is terrible,and does cause great problems,namely removal of phase rotator for starters(if possible)!

Sgeirk,i would gladly put a track through the 8100a/xt2,if i have the track of your choice,and upload it to my web space(pref no hypercompressed cd).

Of course i do not know if my settings/mods would be your cup of tea,or not?

Also Sgeirk,what is your taste in music?

One piece of gear i do like is the 222a spatial enhancer,subtle but very effective!

 

[FFoti1]

Re: modifacation Optimod 8100A

Without giving too much away,the mr gibbs module is a smart clipper.
Also internally on the mr gibbs modules output,their is a clipper on the input of a non inverting opamp buffer output!

When you look at the rest of the associated post filter on the Unity 2000's board 8,this would be similar(ish) to card 0,on a 8100a.
The final clipper after board 8's filter also has a clipper,who's bias is derived from the mr gibbs module,this final clipper is to assure any overshoots added peaks,are clipped to the same output of the mr gibbs module.

Sorry, the Mr. Gibbs module is NOT a smart clipper. Also, the final clipper threshold is not set to operate at the same clip point as the Mr. Gibbs module. They are different, and it relates to the name of the module.

-Frank Foti

 

[gtomas]

Re: modifacation Optimod 8100A

Some time ago i recorded from the tuner a track called Roxette queen of rain,and put it on http://161.53.122.19:8080/ it is still there!

User = processing
pw = clips

I am sure you recognise the link,i forgot who was generous enough to allow recordings to be uploaded there.

The Roxette track was not processed for max loudness,but the recording has a nice clear detail to it.

Wow, I come a little late to this very interesting discussion

I would also very much like to hear the modded processors/set-ups that everybody here is talking about. I would invite everyone to upload clips to the server http://fserver.redirectme.net using the above login and password. The intention of that server is to be able to hear different processing/processors in the first place, so use it freely. Please use the above URL and not the IP address, as I might have to change the IP address or port number in the future and URL will track that transparently to the end-user...

That being said, I very much like the Roxette recording that you made (and actually asked about it in the Processing clips thread and received at least one more e-mail about it, but I guess you weren't following that) and would definitely like to hear more! That kind of processing is something I like - sounds big, while still sounding nice

So, looking forward to hearing more clips of what you (and everybody else) has under the table!

The mods that I have done to the 8100/XT2 were the basic ones - slowing down release times in XT2, and changing some of the thresholds in the multiband. Unfortunately I didn't (don't) have an 8100/XT2 that is not used on the air, so I couldn't experiment much further. I also tried raising the limiter threshold of band 5&6 to get less HF limiting and more clipping, but like Mike, didn't actually like that. The jocks OTOH didn't like the slower release times in multiband as it provided less level correction and less "fusing" of the sound in the mix, so eventually I returned to the stock set-up. Can't fight the people when they get used to something...


Regards,
Goran Tomas

 

[BROADCAST]

Re: modifacation Optimod 8100A

Hi Frank,
I drew out the Mr gibbs schematic approx 6 years ago,and have now found the schematic.
I sold the unity shortly afterwards,so i am unable to now sweep parts of the box.

I have now been emulating the schematic of the mr gibbs module,that i drew out then,and have been looking at the response.
I have not had chance to add the post cicuitry,that is on card 8 of the Unity 2000,to the rest of the emulation.

The Unity 2000 i had 6 years ago was a early model,and the manual says "Preliminary operating manual on it"!

The input to the module has a clipper,on the input of an inverting opamp circuit,the o/p of the opamp goes to several stages of lp filtering,and phase correction.

There is also a parallel path that has in effect only the clipped only products from the i/p clipper that are lp filtered at approx 2.2khz,then recombined with "main circuit path".

From what i can emulate up to this point,if no clipping occurs,the main audio out frequency is flat up to approx 7khz,at approx -26.5db.(remember this is the o/p of the module,not the rest of the post circuitry on card 8).

If i were to short the ip clipper to ground,this would cancel all main path audio,but pass the full audio through the 2.2khz lp filter,this has the effect of producing an audio level on the modules output of -8.9db.
As this higher level of 2.2khz lp filter gain circuit summs,out of phase,compared with the "main path",this would indicate to me that the effect is to cancel,or reduce clipper induced distortion below 2.2khz.

That is where i compared the Mr gibbs module to a smart clipper,please accept my apology if i am wrong here,as frank,you will know better than me.

I find it very interesting comparing manufacturers methods of getting the desired result,i have huge respect for your inovations.

 

[Sgeirk]

Re: modifacation Optimod 8100A

My taste in music runs the gamut from Oldies to Alternative to dance (mostly drum and bass) to some things that would curdle milk if it were in the same room.

I've used an 8100 w/Arianne in a major market for Oldies with beautiful results...recently. My goal was to "create a sound"...a sound reminiscent of how the songs sounded on the radio when they first came out, but a whole lot more open. It was a success.

My experience with today's hyper-compressed music is that one of today's Oxxxx processors are better suited to the unfortunate task, rather than an 8100, although after a lot of the mods discussed on here, perhaps not.

The 8100a barfoot can sound excellent on certain material,easy listening etc.
On some old thin sounding tracks,the xt2 can dynamically equalize the sound with great success,one track for example is Lisa Lisa and cult jam,head to toe.

Some time ago i recorded from the tuner a track called Roxette queen of rain,and put it on http://161.53.122.19:8080/ it is still there!

User = processing
pw = clips

I am sure you recognise the link,i forgot who was generous enough to allow recordings to be uploaded there.

The Roxette track was not processed for max loudness,but the recording has a nice clear detail to it.

Regarding todays hyper compressed material,this of course is terrible,and does cause great problems,namely removal of phase rotator for starters(if possible)!

Sgeirk,i would gladly put a track through the 8100a/xt2,if i have the track of your choice,and upload it to my web space(pref no hypercompressed cd).

Of course i do not know if my settings/mods would be your cup of tea,or not?

Also Sgeirk,what is your taste in music?

One piece of gear i do like is the 222a spatial enhancer,subtle but very effective!