First, a response. Second, my take on the Illdigger mods.
I guess it is unfortunate that all of our advances and years of technological development have led us here.
By extension of some of the arguments being made, we might as well go back to wax cylinders. It seems that even if one were to change one or two components from the original amp it might adversely affect the sound and hamper the musician's ability to be inspired. How do we even know if a working, original amp still sounds today the way it did when it was new? We don't, and should not use that as a guide.
The merits of playing a real mechanical/electro-mechanical instrument vs. playing a digital simulation or sample are not being argued here. The real instrument is better from a musical experience- period. Real instruments allow nuance and infinite resolution of dynamics. If you hit a key really really hard on a Wurly, it will respond accordingly. Often, the reed may even break. On a digital simulation, it plays the sound for velocity 127. You may hit the key even harder next time, but its still 127 to the computer. Eventually the key will probably break off. Of course-- real pianos sound better. Real pipe organs sound better. When the guitarist complains to me at the gig because I ask for help moving all these heavy old keyboards around I tell him when he replaces his guitar with an iPad I'll leave the heavy stuff home.
BUT, in order for the real instrument to do what it is supposed to, it must be properly maintained and set up. If the piano must be in tune and sound good, a Nord can and will outperform a real Wurly if it is compared to a real piano that has not been maintained. Same with a real piano. Same with a real pipe organ. Often this is the case, unfortunately, and the digital electronics win out. And, in all fairness, some of the new stuff is quite excellent- despite it not being the real deal.
One of the most obvious examples of all this is a Rhodes Stage piano. It doesn't have any active electronics. Only 2 passive pots and a cap. Depending on how it is set up, it can sound VASTLY different. Thin, round, even, uneven, clanky, clinky, barky, bell like, thunky, crappy dynamically, great dynamically, good sustain, poor sustain. It's all in the setup. The Wurly, although different, has many of the same properties due to the mechanics and setup. Again, I will restate that the sound of each individual piano probably has more to do with the setup of the reeds, pickups, and action than an original amp (properly working) vs. a new amp. The electronics either get the sound out of the piano or hide it beneath noise and artifacts. Again, a properly operating vintage amp does not contribute appreciable distortion (unless pushed too hard- but then the speakers also contribute to the distortion) - but it is still NOISY regardless. Hard clipping is hard clipping in the solid state world, and is generally considered offensive.
Sorry, but removing hissy noise and AC hum does not lessen a musician's experience, it improves it. In our experience, not one client has ever wanted to go back to the original amp after hearing ours properly installed. In the 10 year history of production, now with nearly 1000 amps in the field, we have only ever had one person return an amp to us for a refund, and that was without a clear reason. If that one person didn't like the sound of our amp, which may be the case, then that person is the 0.1% outlier in our data set. Of course, there are probably 1000s more out there that have not purchased our amp because they don't like it. But perhaps they haven't heard one live in person, they bought a new amp from somewhere else and they are happy with it, have heard an improper or poor installation, or tried it on a piano that was really bad. Or maybe they have preconceptions or misconceptions about the sound- how it sounds, or how it should sound because it isn't an original stock factory amp. Or maybe they just plain old don't like it. Maybe they think it is too expensive. That's fine, and, there are other options. Everyone can do what they wish. But I will always defend our product and our reputation if I feel it is being misrepresented or criticized unfairly.
If a new amp or component or whatever is designed properly, it will not change the desired character of the sound. It will only remove the undesirable side effects. If a person likes side effects, stick with the original. Can't help anyone here. I don't think side effects are a musical source of inspiration, however, unless one likes timing their music with AC line frequency artifacts or puffing vibrato. Maybe avant garde types?
As for the tricked out Wurly discussed having problems with noise on stage, there are various reasons why it might be noisy, even with a new amp, if it even has one. We have never done a MIDI install on a Wurly, so it isn't our work. There are 3-knobbers out there tied in to original 200A amps as well as other 3 knobbers that aren't ours. Maybe a ground went open somewhere inside. Maybe the MIDI system was creating hash and interference due to a failing power supply wall wart. Maybe another connection came loose. Maybe the volume pot was going bad. Maybe the IEC inlet was busted and the ground was intermittent. Maybe it didn't have reed bar shields. Maybe the keyboard player left his cell phone on the top. Who knows? It wasn't right, but it could probably be properly resolved by someone with the right skill set. If all the noise and interference was desirable, they wouldn't have asked to use a backup piano!
Backups are often needed for various reasons. Subs are generally kept on standby for quick swaps when things go south. What if reeds break? What if a key gets stuck? What if the piano gets knocked over and lands upside down? Rain at an outdoor show. What if the original amp blows up? What is the artist has a fit and wants a new piano because the guy running monitors wasn't looking? LOCUSTS!!!!
Nothing is fool proof or bullet proof, but we'd like to take as much precaution and do whatever can be done to achieve the highest possible level of reliability. Old electronics are one of the biggest failure points.
As for the Illdigger mods, here is basically what he is doing, quoted direct [sic], followed by (>>) my comments:
It should be noted that in this rebuild process, it appears that there are no changes to any component values from those originally specified. So he isn't really modifying the design, but rather blueprinting it. The only modification appears to be low noise transistor substitutions.
First, Mr. Illdigger's editorial:
1. You can read all over the net that wurlitzers are noisy and you can’t do anything about it. B.S !
>> Agreed. But there are limits to how far you can go with the original circuit and equipment.
2. all you see on forums is people telling you to just replace the whole preamp/amp board with newly made ones. no offense to these people or the board makers but to me this is HERESY.
>> Disagree, but we make and sell boards. We are admittedly biased. It must be considered also, however, that what is being proposed here by making improvements to the original equipment is also heresy to some.
3. I personaly wouldn’t want op-amps in my wurly.
>> Disagree. A properly designed circuit with a quality opamp SELECTED for the job can and does work better than the original Wurlitzer circuit. Opamps are just great when used properly. Any recorded audio we hear has likely already gone through 100s of opamps. Anything used improperly will be bad. Sadly a lot of audio equipment is also bad.
4. This is a good discrete transistor design and there’s still a lot you can do to lower the noise further.
>> Not really a good design. The front end isn't too bad- it is a marked improvement over the 200. Overall it still has many weaknesses. You can, however improve the noise.
5. It’s just that normal repair guys don’t want to go through all that trouble or simply don’t have the knowledge to do it.
>> True. It is a lot of trouble. And some guys don't have the knowledge.
6. Or they would have to charge too much because it’s a big job.
>> Also true. It takes many hours to do a rebuild cleanly and properly. By the time you pay for labor and parts (especially some of the parts that have been chosen here), a new amp board will actually be less expensive, perform better, and have better long term reliability. It is possible that once Mr. Illdigger does a few dozen rebuilds, and deals with cracked boards, improperly removed boards, improperly shipped boards, other flaky components and intermittent problems that start acting up AFTER he has rebuilt it and sent it back out, and flaky clients, he will likely start telling people to buy a new amp board. Unless he really enjoys that sort of thing, which he honestly might.
And now the technical details, aside the normal repairs, clean up, and recapping he has discussed:
1. Replaced the transistors with modern low-noise ones (drasticaly reduce hiss)
>> Probably 2N5088s or BC550s. These aren't particularly modern, but are solid performers. There are many others...
2. Replaced all signal carbon resistors with high quality film ones ( the red ones, in key spots, especialy the first ones, drasticaly reduces hiss.
>> Absolutely, but the expensive resistors he is using are probably overkill in this application. Any decent metal film will do- very accurate, and lower noise. Thermal noise of all resistors, regardless of type, is the same. There are other mechanisms for noise in different types of resistors with regards to construction and materials.
The first resistors in the signal chain are the most important, because any noise they create will be amplified as the gain is highest from the input. If it's along for the ride with the signal from the pickups, it will be amplified just as much.
For those that care, you can look up the theory and math.
FWIW, carbon comps are among the noisiest.
3. The combined effect of the new transistors and resistors is very noticable in lowering the background hiss).
>> Yes.
4. replaced the electros with high quality Nichicons
>> Great. Nichicon makes a great cap.
5. All coupling caps replaced by high quality bipolar Nichicon muse capacitors.
>> Not sure there is a real advantage here. The datasheet and technical specs for these audio caps are not much different than Nichicon's regular caps, except for flowery language like "Tighter bass". Maybe they are lower ESR and ESL or have different dielectric absorption characteristics resulting in better frequency response. It isn't obvious from the datasheets. It may just be marketing to sell the same cap as their commercial line at a higher price to audio types.
6. All the ceramic feedback caps were replace by film and polystyrene capacitors (for mojo!)
>> Probably not necessary, unless the ceramic caps are damaged or highly microphonic. Yes, ceramic caps can be very microphonic. 'Mojo' is not a valid reason in my view, although others are likely to disagree.
7. replaced the aux and driver transitors with low noise ones and matched the pair of drivers to fix the crossover distortion some wurly can have getting older.
>> Yes. Keep the signal path as clean as possible as we head downstream. We'd also replace the gain trimmer (R-11) which gets flaky. The crossover distortion definitely gets worse as the amp ages. One of the weaknesses of this design- transistor parameters that drift start causing bad behavior. Better designs avoid this from happening by designing around or compensating device characteristics that drift with time and temperature. The crossover distortion will likely creep back in after a while.
8. replaced all the resistors in the bias/psu with higher wattage and matched where applicable. High quality Draloric 0.1% resistors for voltage reference and bias, to realy put back the wurly up to specs intended by the designer, and not the stock 20% resistors which can be up to 40% appart when they should match.
>> Don't think any original resistors on a Wurly 200A board were as bad as 20% tolerance. All I have ever seen was 5% or better, except for some 10% carbon comps on the HV supply where are not critical. It is possible they drift out of tolerance further than their marked tolerance. Not going to take the time to figure that out. Replacing them can't hurt, but 0.1% tolerance is probably overkill. The transistors vary more than those tight tolerances can likely account for. But again, haven't done and won't do the analysis.
9. brough the tremolo circuit back to spec, changed and matched the oscilator transistors and matched the resistors.
>> If it starts up quickly and oscillates at the right frequency and amplitude, no need to touch the oscillator. But the trimmer that feeds the opto is usually flaky. We would replace that.
10. redid all the power wiring cleaner and with more rubust wire where needed
>> Cleaner absolutely. Never thought the 18AWG wiring throughout the piano wasn't robust enough, however... the fuse blows at 1/2A. If its the right fuse...
11. All signal cables redone with high quality shielded wires routed as far as possible from power cables. (this is realy key to reduce hum, a stock Wurly is full of problems)
>> Maybe if the original wiring is bad. The original 200A audio wire has a foil shield with 100% coverage, can't get much better than that. His final pics also show the original wiring in the audio path still in the piano and being used.
12. The piano was now fully working and very low hiss but a bit of hum still remained low in the background. The stock Wurlitzer is grounded in way too many spots, through the cable shields, the harp etc. Which causes internal ground loops (HUMM..).
>> This is true. Our 200A replacement amp comes with new ground wire and instructions for properly routing it using a different scheme. The transformer, when *physically* inside or part of a ground loop will induce hum from the field it generates. The loop with the transformer inside must be open. The ground can be reconfigured around the transformer without affecting the integrity or safety of the ground.
13. Instead of putting another neon bulb powered from the mains like the original, (Neon bulb induce noise in the circuit by themselves, plus the additional mains voltage in the wires which could induce humm in the audio) I replaced it with a big orange led powered from the psu.
>> We've never had a problem with the neon bulb. But if it is dim, flickering, missing, or blown we will often put an LED in its place and tap power from the amp board. If the original is still good we will leave it in place and clean up the AC wiring.
That's a wrap!
Tim
