I could build a squarer circuit with an opamp or a comparator chip, write a simple PIC pogram to use the PWM generator, but for me I just need to hook the amp up to my PC. The FFT analyzer program has a generator that does sine, square, triangle and PWM. I just need to clean off some space on my other workbench. I got home from work at 8 PM tonight, didn't happen. Tomorrow doesn't look good either.
A simple square wave generator can be cobbed up from 1/4 of a CD4093 or 1/6 of a CD40106 (one a quad NAND, one a hex inverter, both Schmitt trigger). You can also use a simple feedbackcircuit with one of the CMOS 555 chips. All run very well off a 9V battery, and can be lashed together "dead-bug" fashion in minutes. The nice thing about such a lash-up is that it's totally isolated.
BTW, I put together a little SE amp using 6LR8s with a shunt regulator to emulate the low dynamic resistance of LEDs - otherwise, with the number of LEDs needed to bias the 6LR8s in triode mode, the light would be too much to bear... If I get time and the circuit actually sounds nice, I'll be trying the same dodge with a push-pull amp.
BTW, I put together a little SE amp using 6LR8s with a shunt regulator to emulate the low dynamic resistance of LEDs - otherwise, with the number of LEDs needed to bias the 6LR8s in triode mode, the light would be too much to bear... If I get time and the circuit actually sounds nice, I'll be trying the same dodge with a push-pull amp.
I thought about that but haven't tried it yet. There was a circuit in an old electronics magazine for an "adjustable zener diode". It was basically a shunt regulator using a 2N3055.
I also thought that I would just try some big zener diodes. I put some 1.5KE11A's and 1N5348's on the list for my next Mouser order, but it likely won't be until the end of August. I will be out of town for most of August, so all of the fun science will end real soon.
The 6LR8's do require a lot of cathode voltage. That would translate to a lot of LED's or a BIG zener diode.
I use a 192KHz external box (EMU1820). I just installed it a few months back for multi channel recording capability. I haven't tried it yet for audio analysis. It is the same basic design as the internal 2 card system that it replaced (EMU1212). The internal driver card is the same for both systems so I can use the old I/O card if I need to.
The old system is going into a seperate PC for experiments like testing amps. I don't like hooking up amplifiers to my main computer. The main computer is on a seperate power system incorporating a UPS. This gurantees some grounding issues and residual 60 HZ in the measurements.
The 10KHz square wave isn't too bad. Frequency response sweeps of the old system itself were within .5 db to about 80 KHz after I modified the filters on the I/O card.
The old system is going into a seperate PC for experiments like testing amps. I don't like hooking up amplifiers to my main computer. The main computer is on a seperate power system incorporating a UPS. This gurantees some grounding issues and residual 60 HZ in the measurements.
The 10KHz square wave isn't too bad. Frequency response sweeps of the old system itself were within .5 db to about 80 KHz after I modified the filters on the I/O card.
To SY -
We discussed shunt regulators vs. LEDs briefly at Burning Amp last year. My reasoning behind trying a discrete shunt regulator is that if the regulator is stable and substantially faster than the current slew rate of the amplifier, any disturbance when the amplifier slews will be minimal. The regulator I'm using simulates well. The truth as usual will be in the listening. I'm not knocking LEDs, I just wanted to try something different.
I'll be brinigng an amp or two of that sort to Burning Amp this year. The thread for the first one can be found by searching for "Mighty Mite" "Mighty Mite" also uses a switching power supply, so it will be just full of little heresies.
Now back to your regularly scheduled programming....
We discussed shunt regulators vs. LEDs briefly at Burning Amp last year. My reasoning behind trying a discrete shunt regulator is that if the regulator is stable and substantially faster than the current slew rate of the amplifier, any disturbance when the amplifier slews will be minimal. The regulator I'm using simulates well. The truth as usual will be in the listening. I'm not knocking LEDs, I just wanted to try something different.
I'll be brinigng an amp or two of that sort to Burning Amp this year. The thread for the first one can be found by searching for "Mighty Mite" "Mighty Mite" also uses a switching power supply, so it will be just full of little heresies.
Now back to your regularly scheduled programming....
I've been thinking that if you use big LEDs for bias and are blinded by the resulting radiance, you might as well wallow in the concept a bit and build an amp using some translucent material like marble - you wouldn't need a pilot lamp. That way, you're not hiding your lamp under a bushel, so to speak. I actually have some marble slabs in the basement looking for a use - marble tile might work as well. A cubical "Shrine" amp made of marble would look mighty fine.
Mr Tubelab,
I have a rusted Fisher X100 that use EL84 for output, I thought it would be perfect for hosting your simple p-p circuit. I may add the led arrays later.
Is it possible to see the simple p-pschematic? otherwise, would you share the value of the resistor values used in first stage VA and phase splitting stage?
thanks in advance
I have a rusted Fisher X100 that use EL84 for output, I thought it would be perfect for hosting your simple p-p circuit. I may add the led arrays later.
Is it possible to see the simple p-pschematic? otherwise, would you share the value of the resistor values used in first stage VA and phase splitting stage?
thanks in advance
I haven't drawn a legible one yet. It is pretty generic stuff. The input tube is a 12AT7. The resistor values are not fully optimized yet. The first stage currently has a furball of resistor that make up the feedback network. The plate load is a 51K. This stage is direct coupled to the phase splitter. Plate and cathode resistors are 24K (maybe too small).
I have had very little time to work on the Simple P-P until lately. I have laid out a new PC board to fix all of those little things that show up when you build the very first one of anything. I have not had the time to make one yet.
It is an unfortunate side effect of todays uncertain economic times that the PC board sales have dropped to near zero. There were two orders this week, none at all for the previous two weeks. I can't justify spending the $1000 plus it takes to get a new board launched until things improve. I will continue the development of this board at a slower rate to spread this cost over more time.
Well for the six surgeries, a new tumor appeared rather quickly, often in a couple of weeks. It has been almost 2 months and none have showed up, so I am beginning to believe that they got it all this time. Work has been a challenge, but I an almost caught up. There have been no glowing tubes since I was home recovering, but things are looking up.
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