Strange new vibrato circuit in DR Reissue

[nickb]

Yes, this circuit is due to ROHS and CdS being on the banned list since July 1st 2007. Solar power cells don't use CdS, way too low efficiency besides ROHS.

In point of fact, solar cells can be made with Cadmium Telluide and the efficiency exceeds mono si. Cadmium telluride photovoltaics - Wikipedia, the free encyclopedia

These are specifically allowed under RoHS: Restriction of Hazardous Substances Directive - Wikipedia, the free encyclopedia

I guess it goes to show that the whole process is subject to political whim.

Yup, that board seems excessive. I bet the justification is exact modelling of the original ( overlooking the +/- 50% or so tolerances of the original of course)! Welcome to progress. Don't get me started on CF vs incandescent...

[ribo1989]

I bought the optocoupler from Tube-Town and its looks like a Fender but I am not sure. I ordered two genuine Fender optocouplers and I will try them one after the other.

Meanwhile I replaced the stock V5 with a Tungsol 12AX7 and the tremolo intensity increased a little, but still too shallow. I checked the voltages around the circuit and they are OK.

Regards.

[bob p]

When I first looked at Pedro's photo of the board, I thought about making a tongue in cheek comment that such a complicated solution could only be the result of an EC mandate. Yikes! I was only going to make that comment as a joke, but it turns out that the joke is real.

Wouldn't it be simpler just to go back to a tube-based oscillator?

One thing about all of this ROHS stuff really bothers me -- the unintended consequences of good intentions. Looking at that board, it seems that the workaround to avoid the tremolo bug requires an awful lot of parts. It makes me wonder if the adverse environmental impact of all those parts in aggregate might outweigh the environmental impact of just one tremolo bug. We already know that once you factor in the cost of mining, manufacturing, and disposing the hazardous chemicals in batteries, the carbon footprint of a Toyota Prius is bigger than a gas-powered Hummer.

[Chuck H]

We already know that once you factor in the cost of mining, manufacturing, and disposing the hazardous chemicals in batteries, the carbon footprint of a Toyota Prius is bigger than a gas-powered Hummer.

I'm glad to read that someone else is privy to this info. My brother related this to me (and he's a smart guy) so I assumed he had his facts before sharing. Startling reality. The point behind the Prius turns out to be marketing. Not environmental responsibility. And we, as humans, seem to miss the point repeatedly before catching on. We'll be the death of us!

[Enzo]

The problem with arguments like that is that they take one factor and extrapolate the whole circumstance from it. I think it is not so simple as adding up some disposal costs. Maybe we take the carbon footprint argument at face value, but whole lots of folks bought their prius with more than carbon footprints in mind. There is the whole drain America first crowd. I am sorry, I mean the whole reduce dependence of foreign oil imperative. So even if we don;t save any carbon, if it means we burn less gasoline, that is one plus. There is something in favor of the Prius et al for either end of the political spectrum. Save the atmosphere or save the gas imports. And for many people, footprint be damned, it costs less to fill its tank.

I would like to see actual research on this total carbon idea, it sounds too pat. I have no dogs in this fight on either side.

[Chuck H]

Agree. And since I haven't done any research for myself, which would need to be exhaustive to be comprehensive, I can't argue the validity of the Prius vs Hummer as to environmental impact. Your point about reducing the need for imported oil products is valid. But my dog in this fight would definitely be the overall carbon footprint. It seems like current trends favor finding reasons to invalidate or at least minimize the issue. But I still believe that it's a matter of some gravity.

[bob p]

Sorry Pedro, but I can't resist the temptation to hijack your thread.

> Drain America First.

Does anyone actually believe that all of the oil reserves in the US were “just discovered”? As in: “They were here all the time and we just never noticed them before.”

Or is it more likely that they've been left undeveloped on purpose, as part of a policy to deplete the world's resources from other/less friendly nations while leaving our reserves intact? Strategically, it's wise to deplete the oil reserves of your enemies and to leave your own reserves intact, not tapping them until the oil sands of the Middle East are dry and Middle Eastern leaders (those without nukes, anyway) have become marginalized by economics, and you're left holding what's left.

It's likely that the recent paradigm shift to deplete our own reserves is a result of the economic pain that we've recently experienced in sourcing energy from abroad. Why? Because international oil trade is denominated in dollars, dollars are being printed to the point that they become fiat, and the dollar loses it's purchasing power on international markets. When the dollar loses purchasing power in currency exchange, our only recourse is to pay a lot more for imports, which in turn demands that we return to developing goods (energy) from within our own borders. This is basic macroeconomics.

Unfortunately, we've reached a point where the financial cost of increasing energy prices on the economy is finally being realized, and the realization is compelling policy makers to trade off strategic decisions for economic ones. No, it's not as if that oil was there all along and nobody ever realized it. It was left undeveloped as part of a strategic plan.


> The problem with arguments like that is that they take one factor and extrapolate the whole circumstance from it.

There are two ways to approach the problem. One is to extrapolate and one is not to extrapolate. Extrapolation isn't bad. It makes an attempt to consider all of the contributing factors in a detailed analysis. Not extrapolating probably isn't as good. Non-extrapolators tend to close their eyes to every factor that doesn't involve personally paying for your own gas at the pump.

The non-extrapolators like to focus on what they can see immediately before them; they prefer to take little else into consideration. Without extrapolation, one's vision becomes myopic and one tends to care only about self-centric things like how much it costs you to fill up your car at the pump. Non-extrapolators can look at a Prius and see a car that's cheap to fill up, and what they spend on gas may be all that they care about. Unfortunately limiting the analysis to “my-wallet” is inherently myopic and inaccurate; it fails to take into account other important contributing factors.

Unfortunately, that approach tends to filter out inconvenient facts. As an example, here in the US we have tax subsidization for the production and purchase of electric/hybrid vehicles. The result is that the purchaser never pays the true cost of the car when they purchase it. Because of subsidies, they use some of their money and a lot of other peoples' money to purchase a vehicle whose retail price has been artificially depressed. Think about that commercial for the Chevy Volt, where the dumb girl says that she can't remember the last time that she went to a gas station to fill up her Volt, that she's forgotten where the gas cap is located, and that she was going to take all of the money that she's saved on gas and spend it on a trip to Hawaii. The reality of the situation is that she's dumb if she can't remember how to refuel her vehicle, and that we taxpayers are footing the bill for her trip to Maui because our tax money gave her a car at an artificially low purchase price. Of course Volt owners like this paradigm; it's the transportation equivalent of the free lunch. On Maui. What could be better than that?

Unfortunately, the artificially low purchase price of the vehicle and the low cost of filling up at the pump renders the true cost of the vehicle invisible to the operator. That tends to inappropriately skew peoples' opinions in the wrong direction.


> I think it is not so simple as adding up some disposal costs.

Disposal costs aren't the only factor that gets ignored. There's a huge insertion loss that occurs when manufacturing electric cars.

I cringed when I drove past a Freeport McMoran mining operation in Colorado, where an army of diesel powered heavy equipment had flattened a mountain foothill, reducing it to a hole in the ground. A never-ending parade of ginormous 4000 HP Caterpillar Mega-Trucks hauled away raw ore for processing, each vehicle having a Gross Operating Weight of 1,375,500 pounds. That's right -- they were moving 1.3 million pounds of gross weight at a time. And the parade never ended; the convoy of trucks kept running 24/7. It reminded me of how an ant colony moves earth to make an anthill, but on a much larger scale.


http://robertkaplinsky.com/wp-conten...ruck_small.jpg

The problem with rare earth batteries is that they are made from components that are ... well... RARE. You have to mine a tremendous amount of earth in order to provide a concentrated supply of rare earth elements. Battery disposal isn't the only problem. Battery production has to be “extrapolated” if you want to understand the total environmental cost of operating a Prius or a Volt. I don't expect that the average car owner is particularly well versed in thermodynamics, so the changes to the enthalpy and entropy of the system likely escapes them. Maybe this perception would change if people saw a picture of a Prius next to the giant mining truck and the even more gigantic hole in the ground. I don't see much that's green in those photos.

Setting aside the thermodynamic inefficiencies and the tax subsidies, even a simple break-even analysis like this one is enough to give me pause when considering the environmental impact of “green” battery powered vehicles. It seems that a lot of people don't particularly enjoy math, so they avoid simple calculations, like the break-even analysis between a gas powered Honda Civic, a diesel-powered VW, or a battery powered car. When you're mathematically challenged, you don't plot TCO curves and look for intersections, and you don't do thermodynamic calculations. You tend to focus on pump-dollars and TV propaganda. I think it's dangerous to hide the true cost of operating one of these electric/hybrid vehicles with all sorts of price-depressing subsidizations and tax-trickery. Focusing on pump-dollars makes it all to easy for people to make the wrong decisions for the right reasons.


> So even if we don;t save any carbon, if it means we burn less gasoline, that is one plus.

Not burning gasoline is a big plus, but it's important to consider the big picture, not only the little one. Sure, a Hummer burns a lot of gas. But to get the big picture, we also need to consider the environmental cost of scrapping a perfectly good Hummer (which took a lot of energy to produce), along with the cost of manufacturing a completely new car to replace that Hummer. Then we have to compare that sum to the environmental cost of continuing to operate a perfectly good car (Hummer) that already exists. There is a HUGE amount of energy that is consumed by the process of manufacturing a new car. Want to do something good for the environment? Don't keep buying new cars. Keep something that's reasonably fuel-efficient; keep it well-maintained, drive it until the wheels fall off, then put new wheels on it and start all over again. It's best to defer the environmental cost of manufacturing a completely new car entity as long as you can, because manufacturing a new car is itself a very energy inefficient process. Want to do something even better for the environment? Ride a bicycle or take a walk to the store instead of driving that Prius.

[Enzo]

it's important to consider the big picture, not only the little one.

Actually I think that was what I was proposing by suggesting there were a lot of factors, rather than taking ONLY carbon footbrint and extrapolating an entire argument from that one point. You are using the word extrapolate to mean something totally foreign to what I was discussing. And without devolving into rhetoric, no one suggested scrapping "perfectly good" hummers. The idea would be when the hummer wears out, someone might replace it with something more efficient.

Ride a bicycle or take a walk to the store

Yeah well, I live 15 miles from the nearest store, so no thank you. I also live in Michigan and several months of the year, my walk to the store is through snow.

But one thing I DEFINITELY was NOT proposing was to turn this amp thread into a political discussion. And for any responsibility I bear for having done that, I apologize. PLEASE, if we want to discuss this, take it down below to the other stuff section.

[Steve Conner]

As far as I know, the board is a high voltage discrete Operational Transconductance Amplifier (OTA) configured as a voltage-controlled resistor, to emulate the LDR part of the "trem bug". The reason for its existence is RoHS, so it may only be in amps meant for the European market.

Alex, did you really get a MOSFET SSR to work as a substitute? Is it stable with temperature?

[Alex/Tubewonder]

Steve, it's based on Fairchild H11F1M. The brainy part is in emulating combined dynamic response of neon+LDR modulator.

[bob p]

Anyone else out there worried about opto circuits that are based on the Fairchild H11F1M? My experience with the H11F3 in the Neutron circuit is that they're very sensitive to signal amplitude and tend to introduce clipping into designs that don't clip when other optos are chosen.

[Alex/Tubewonder]

Your bad experience is most probably caused by choosing wrong part for your particular application.
H11F1 specifies +-30V breakdown voltage for the internal JFET, while it's only +-15V for the H11F2

[Steve Conner]

Correct... So how do you get it to handle the signal voltage it sees in the trem bug application?

Other problems I've found with the H11F1: The ohmic region is pretty small. "Idss" is about 400uA when the LED is lit brightly, and falls off from there as the LED is dimmed. Above 400uA it loses its linear resistive properties and looks like a current source. This is a form of clipping. Since we are looking at the ohmic properties, Ohm's law implies a signal voltage limit corresponding to the current limit. See Figures 2 and 6 in the datasheet: the maximum linear signal voltage is a few hundred mV, nowhere near what a trem bug requires.

It suffers from Miller effect: a fast-changing voltage across the channel will couple to the gate and modulate the on-resistance. I discovered this when I was using it as a voltage-controlled soft clipper ahead of a power amp. I could never get it to sound good, and ended up going back to diode clipping.

[Alex/Tubewonder]

Of course it's not a direct replacement for the "trem bug", it's part of tremolo circuit emulating bug's characteristics.
Hint: there's a Circuit Idea somewhere on the EDN site using H11F1, an expansion of an older idea from mid 1970s, in a compressor which might work in a stompbox. Uses 2 H11F1 which calls for matching. Makes the whole thing too expensive as these things spread pretty wildly. So I'm not pursuing this any longer, and since I have a thorn in my side courtesy of Fedner so I let it be.
A simple circuit based on the attenuator app in the data sheet controlled with a ca 30% duty cycle SQW works but doesn't sound right, so you'd be back to control waveform problem.

[bob p]

Your bad experience is most probably caused by choosing wrong part for your particular application.
H11F1 specifies +-30V breakdown voltage for the internal JFET, while it's only +-15V for the H11F2

Thanks for your ideas. I'm going to disclaim responsibility for the part selection. The circuit is R.G.'s Neutron Filter, which I built according to his schematic, BOM and documentation. He specifies the H11F3 as the opto of choice (along with 3 other options which are extinct vintage parts like the CLM6000). The consensus among people who've actually built his Neutron Filter circuit is that the H11F3 doesn't perform well -- it clips on large signals. Unfortunately, the other opto options in the bill of materials are parts that are either extinct or difficult/impossible to find. I realize that thread is the wrong place to look for help. Thanks for the suggestion about the H11F1 and the warnings about matching. The circuit uses 2 of them, and I anticipate that matching will be a problem. Sorry for the hijack.