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Post by jimwilliams on Mar 7, 2018 15:52:49 GMT -6
I used to build those back in the early 1980's. I used four type 9 tanks with medium decay times, two per channel. Accutronics will do custom work. I had them reverse polarize two of the return coil magnets. Then I connected the two tank return coils in series, that created a hum cancelling design and it was very quiet with a low noise preamp.
I also reverse wired the drive coils and wired them in series. They were put into the feedback loop of the drive amp for constant current drive. In-series the tanks cancelled much of the fundamental frequency and eliminated the "sproing" surf music sounds. It sounded more like a nice plate reverb.
The last circuit was a variable 1/2 to 2/1 expander/compressor circuit wired to a single knob. Straight up was no effect. The expander decreased the reverb time, the compressor increased it. That was the variable reverb time knob.
Then I bought a lexicon.
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Post by jimwilliams on Mar 7, 2018 15:41:43 GMT -6
The battery fits under the Tele control plate, it's already cut out to fit. On the strat it's fitted in the rear spring compartment. The circuit board is small and fits between the Tele volume and tone pots. I use the BurrBrown OPA1642 opamp with very low noise, rail to rail output levels and only 1.5 ma current draw. Batteries last for months.
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Post by jimwilliams on Feb 26, 2018 11:17:46 GMT -6
When I test converters here on my Audio Precision analyzer I also notice some issues not related to the rates but general physics.
The actual performance of the top notch chip sets do quite well at all the published sample rates but the measurements will change. This is not because faster rates are harder, these products are well designed. Industrial converters operate at much higher bandwidths than audio converters and they don't have issues.
When one runs converters at 96k you will measure an increase in THD+noise specs even though the THD doesn't increase with an FFT. This is because the measurement bandwidth has doubled. Then all that increased bandwidth must be extrapolated into a measurement. Noise is not factored out on THD+noise measurements but rather is included, the audio standard for well over 60 years. Therefore THD+noise specs show higher on the AP as well as on the published THD plots from the chip manufacturers at the higher sample rates.
If one considers that all this new noise that is now measured is now placed above 20k hz, it's not something we will hear. Standard AP THD+noise tests have an 80k hz bandwidth, now you see why more crap is measured even though it won't mean much to the end listener.
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Post by jimwilliams on Feb 1, 2018 19:51:26 GMT -6
That mic was used through an Audio Upgrades mic pre on the Vanessa Williams hit, "The Right Stuff".
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Post by jimwilliams on Jan 30, 2018 19:25:49 GMT -6
I built one of those a few years back, same case, same color too. The original transistors are available from Mouser. The schematics from Fuzz Central. I used perfboard and aluminum standoffs to secure it. The octave split is the best part of that thing.
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Post by jimwilliams on Jan 30, 2018 19:19:08 GMT -6
At that price they better rent a storage locker.
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Post by jimwilliams on Jan 29, 2018 15:56:57 GMT -6
Price reduced to $600!
I have a pistol that shoots better flames than that thing. We have some great minds working in the audio field. The problem is a lot of them only do consumer audio now. Only a financial incentive will bring them to do pro audio.
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Post by jimwilliams on Jan 29, 2018 15:39:58 GMT -6
Delta insert sends are -2 dbu. If you need +4 dbu use the direct out jack, but that will be unbalanced. The line in is balanced from -10 to +20 db.
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Post by jimwilliams on Jan 29, 2018 15:34:28 GMT -6
I built my own back in 1980, it was a ton of work. I only did it because commercial stuff was very expensive. I would never do that again. Consoles are 2 cents on the dollar used.
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Post by jimwilliams on Jan 29, 2018 15:29:39 GMT -6
Seems his formula has worked.
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Post by jimwilliams on Jan 26, 2018 11:36:02 GMT -6
The senate will get right on this right after they legalize the illegal immigrants, fix the SS and medicare systems, replace Obamacare, build the wall, re-do NAFTA, and of course, pass another pay raise.
That ought to take another 2 or 3 years?
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Post by jimwilliams on Jan 26, 2018 11:21:45 GMT -6
Modern NAMM is quite tame compared to the 1970's. We called those "the days of lines and noses".
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Post by jimwilliams on Jan 18, 2018 12:17:26 GMT -6
I use Todd Garfinkle's MA Recordings to stress playback systems. "Further Attempts" has an opening track with complex percussion and bells. It rip's a new one on every system that tries to reproduce it.
So far only the best speakers with ribbon or AMT designs can handle it. Dome tweeters simply fall apart every time. Pop music is easy to play back compared to that acoustic stuff.
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Post by jimwilliams on Jan 16, 2018 14:10:26 GMT -6
Depends... left or right handed?
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Post by jimwilliams on Jan 9, 2018 14:49:10 GMT -6
Hi Jim, I always really appreciate your posts! Re: bus resistor -- gotcha. How would you install the OPA1642 or 1602 since they don't match the current socket pinout? 1602's for the sum stages, 1642's in other places if your PSU is stock as it's a POS. Use the Brown Dog dual SOIC to 14 pin DIP adaptors. Open loop gain specs are where summing opamps succeed or fail. The only discrete opamp I know of with good OLG specs at 10k hz is the old Jensen 990, about 85~90 db. The 5534 is 60 db in comparison, 30 db less feedback/distortion correction. API's are around 40 db like the 072 and 741. The better IC's do around 70~80 db OLG at 10k hz. Having a couple more db's of headroom is another benefit of those parts, less clipping throughout the desk and an increased dynamic range with the lower noise floor. No one I know likes hiss. You will also want to ad the small feedback caps across the feedback resistors even if you keep the original opamps. Phase margin, ringing and overshoot is why. You will get better square wave geometry if you do that plus added stability. I'd consider the lack of them a design error. SW tended to use very large resistor values (47k buss resistors) that created excessive thermal noise and reduced crosstalk due to resistor capacitive coupling.
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Post by jimwilliams on Jan 9, 2018 14:33:26 GMT -6
Maybe swap the output transistors to newer, better stuff? On Semi makes a bunch of really nice ones, some TO220 sized and designed for audio.
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Post by jimwilliams on Jan 9, 2018 14:31:21 GMT -6
What opto are they using? I see a lot of Vactrols in newer stuff. I used their dual 5 model in the Rhodes Mk7 pan circuits. Steve at Inward Connections said the current models have been changed and they don't respond like the older ones.
I gave his friend one old one from my stash to test and compare them, waiting for the results...
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Post by jimwilliams on Jan 9, 2018 14:26:25 GMT -6
Anyone know of a source for 200 eproms? I have corrupted ones here and need a copy, the 200 no workie.
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Post by jimwilliams on Jan 9, 2018 14:19:30 GMT -6
Or add a couple of 14 pin Millimax IC sockets and have all the options available? Then you can use some high test chips on a Brown Dog 4136 to dual SOIC adaptor, the old TL075 fet input quad (if you can find one) or the noisy and dirty original RC4136. Plug and play.
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Post by jimwilliams on Jan 7, 2018 15:20:50 GMT -6
I can only use hardware EQ's here. Digital stuff is edgy to me and any boost is an instant issue.
The analog EQ's are also set up pretty well. I use exotic high voltage polystyrene film caps for anything above 2k hz, it does make a huge difference. Even WIMA polyprop's have their sonic issues like stridency.
The exotic silver foil types are even better but cost a fortune to buy. Most have never heard the really good stuff. Mylar box caps seem to be good enough for the masses.
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Post by jimwilliams on Jan 7, 2018 15:12:27 GMT -6
You will need a small value feedback cap across the sum opamp 47k resistor and the fader recovery opamp. Use 10pf NPO mono ceramic to keep the bandwidth up. That will restrict it to below 100k hz and will cancel the buss resistor's stray capacitance that causes ringing/overshoot and any potential oscillations.
Use a 22.1k feedback resistor for the fader recovery opamp as that will return the gain staging to unity. Then shove the master faders all the way up. Dale CMF55's are a great choice.
Use quality opamps to lower noise and improve sonics. Add local .1 uf mono ceramic caps from pin's 4 and 11 to ground. Recommended opamps include the LME series, the OPA1642 fet input and OPA1602 bipolar rail to rail opamps. Those will increase dynamic range and give greater headroom than the standard types. The 1602's draw 3 ma, the 1642's only 1.5 ma, less than an 072 opamp so you won't need to worry about that weak power supply.
When installed, check the output pin's for any DC offsets. All of those are precision opamps and if the offsets are below about 3~4 mv, short out the el coupling caps.
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Post by jimwilliams on Jan 7, 2018 15:00:27 GMT -6
I use my sets of Caldwell shooter's bags here. They are folded so they fit around the legs very tight. They also discourage any potential thefts.
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Post by jimwilliams on Jan 7, 2018 14:54:26 GMT -6
Plenty of issues trying that out. First is it needs to be run in parallel with the active pickups. That changes/darkens tone and lowers output levels. Next, the "dummy" coil still has magnets and will pick up any ferrous induced movements. It's ALIVE!
Alembic first addressed this back in the 1970's by using a dummy coil without any magnets and a buffer opamp to blend it. Les Paul created the first "stacked" humbuckers on his Les Paul prototypes back in the 1950's. Gibson still sells those as the "P-100's", a stacked P-90 design.
My solution was a dedicated hum cancelling preamp and a dummy coil fitted internally. The preamp is two inputs, one for the active pickups and one for the dummy coil. The dummy was made from a Jap Fender strat pickup, the plastic bobbin types with the ceramic bar magnet and steel pole pieces, all of that was removed. The dummy side of the preamp has frequency response shaping (don't need anything above about 2k hz) and then feeds a trimpot for blending. I get about a -80 db hum null with that circuit, quite respectable.
My Telecasters are as quiet as the Gibson's with covered humbuckers, a joy to play out live. I once offered this design to Fender but they were not interested. I guess hum is part of Fender's appeal?
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Post by jimwilliams on Jan 7, 2018 14:36:01 GMT -6
Aphex 651 direct coupled. Feel that bass...
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Post by jimwilliams on Jan 7, 2018 14:34:49 GMT -6
I use ADA 4898-2 for the expensive seats and OPA1602's for the cheaper seats. Many other things are also done like the power supply, loop gain staging, power transistors, passive resistors, feedback bandwidth, etc. I use one high quality film cap, the rest is direct coupled.
The OPA's are essentially LME49720's with the BurrBrown rail to rail output section. Those will lower the self noise and add extra headroom on top for an increased dynamic range.
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