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The ZSP-1 has tons of gain. With 2 volts on the input you can expect to get 18 volts on the output with ultra low distortion.
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You have to wonder what he was driving to get ultra low distortion. I would go to a different circuit topology. There is many circuits that are better and even simpler. Probaly could even use most of the expensive parts that came in the kit to minimize costs.
I use series resistors in my filament supply. If you have a radio shack or similar can get them in a heart beat.
You have to wonder what he was driving to get ultra low distortion. I would go to a different circuit topology. There is many circuits that are better and even simpler. Probaly could even use most of the expensive parts that came in the kit to minimize costs.
I use series resistors in my filament supply. If you have a radio shack or similar can get them in a heart beat.
You don't need to design anything. The Aikido preamp will be perfect, you'll only need to buy a few resistors and better coupling caps. Maybe someone here has a 6n1p aikido schematic, if not use Google.
ST70 has HIGH input sensitivity. That means it doesn't take much voltage to drive it. Construct things for fun if you like (and it IS fun!), but if all you want is the music, you seriously need nothing more than an input potentiometer on the ST70. Then you'll have tunes while sorting out the preamp.
6N1P don't draw 300 mA according to the datasheet. Have you measured this ?
1R resistor will not be suitable for parallel setup of 4 heaters regardless of whether it's 300 mA per tube or 600 mA per tube, which I believe to be the correct figure. You need to drop 0.7V or thereabouts and with 4x600 mA current that works out to 0.3R or 0.33R (the closest standard value). 2W resistor might do, but it would be within 15% of maximum rated dissipation so 3-5W might be more suitable.
1R resistor will not be suitable for parallel setup of 4 heaters regardless of whether it's 300 mA per tube or 600 mA per tube, which I believe to be the correct figure. You need to drop 0.7V or thereabouts and with 4x600 mA current that works out to 0.3R or 0.33R (the closest standard value). 2W resistor might do, but it would be within 15% of maximum rated dissipation so 3-5W might be more suitable.
that is true the data sheet says 600ma. .7v/2.4amps= 0.29 ohms
.7x2.4= 1.68 watts. ok thanks for the advice. it is nice to check my understanding of ohms law here.
i think im going to find a different design. i have a high voltage dc power source and chassis and everything so it is still pretty cool despite this dissapointment but i can listen to my amp without a preamp lol. if only i had have known this months ago. all i needed was to build a simple volume pot, but it has been this experience that has allowed me to build the volume in/out box. the price of education these days
Hello,
I learned this doing what you are doing .Happy Sunday.
As discussed the application of Ohms law to the heater voltage will surprise you. If a resistor is placed in series with the heater circuit the voltage across the heater will drop but not as much as this application of ohms law seems to indicate. There is an mpedance not being accounted for. That impedance is the internal impedance of the transformer. When a resistor is added in series there is less current and less voltage drop across the transformer internal impedance. The voltage will go up at the transformer and the voltage at the heater will still be high. That first guess at 1 ohm may be closer to the correct value.
Check out the B1 buffer threads. A buffer does not need to be sand, can be tubes too.
DT
All just for fun!
I learned this doing what you are doing .Happy Sunday.
As discussed the application of Ohms law to the heater voltage will surprise you. If a resistor is placed in series with the heater circuit the voltage across the heater will drop but not as much as this application of ohms law seems to indicate. There is an mpedance not being accounted for. That impedance is the internal impedance of the transformer. When a resistor is added in series there is less current and less voltage drop across the transformer internal impedance. The voltage will go up at the transformer and the voltage at the heater will still be high. That first guess at 1 ohm may be closer to the correct value.
Check out the B1 buffer threads. A buffer does not need to be sand, can be tubes too.
DT
All just for fun!
G'day chopchip,
I have also built one of these kits and am very pleased with the end result.
1. To address the over-voltage I installed 1N5822 diodes as shown
2. The preamp is designed to drive amps with an input impedance of 100k or higher. So you may need to increase the value of the output coupling cap.
3. I also built mine using the alternative schematic supplied with the kit.
I'll PM some more info.
Cheers,
Alex
I have also built one of these kits and am very pleased with the end result.
1. To address the over-voltage I installed 1N5822 diodes as shown
An externally hosted image should be here but it was not working when we last tested it.
2. The preamp is designed to drive amps with an input impedance of 100k or higher. So you may need to increase the value of the output coupling cap.
3. I also built mine using the alternative schematic supplied with the kit.
I'll PM some more info.
Cheers,
Alex
They are considerably less linear so they will drop close to 0.7V no matter what, 300 mA or 600 mA per heater.
On the other hand, they are considerably less linear so they will induce some switching noise. Whether this can be actually heard or not is another matter ... And on top of that they will not limit warmup current as well as a resistor would.
On the other hand, they are considerably less linear so they will induce some switching noise. Whether this can be actually heard or not is another matter ... And on top of that they will not limit warmup current as well as a resistor would.
And, I might add to Arnulf's points that the resistor method as mentioned by DualTriode is considerably more hit and miss. Standard Ohms law values just don't work. It's experimental from my experience. I've used anywhere from .06 to .4 ohms to get the result I needed. Every transformer is different.
The drop across a Schottky is pretty predictable. In fact I know a fellow in the UK that markets a board that provides 6.3VDC from 6.3VAC using Schottkys and a regulator. It's pretty nifty and good for 3 amps with standard values.
From Wikipedia:
"In alternating current circuits, additional opposition to current flow occurs due to the interaction between electric and magnetic fields and the current within the conductor; this opposition is called "impedance". The impedance in an alternating current circuit depends on the spacing and dimensions of the conductors, the frequency of the current, and the magnetic permeability of the conductor and its surroundings. The voltage drop in an AC circuit is the product of the current and the impedance (Z) of the circuit. Electrical impedance, like resistance, is expressed in ohms. Electrical impedance is the vector sum of electrical resistance, capacitive reactance, and inductive reactance. The voltage drop occurring in an alternating current circuit is the product of the current and impedance of the circuit. It is expressed by the formula E = IZ, analogous to Ohm's law for direct current circuits."
"In alternating current circuits, additional opposition to current flow occurs due to the interaction between electric and magnetic fields and the current within the conductor; this opposition is called "impedance". The impedance in an alternating current circuit depends on the spacing and dimensions of the conductors, the frequency of the current, and the magnetic permeability of the conductor and its surroundings. The voltage drop in an AC circuit is the product of the current and the impedance (Z) of the circuit. Electrical impedance, like resistance, is expressed in ohms. Electrical impedance is the vector sum of electrical resistance, capacitive reactance, and inductive reactance. The voltage drop occurring in an alternating current circuit is the product of the current and impedance of the circuit. It is expressed by the formula E = IZ, analogous to Ohm's law for direct current circuits."
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that preamp sounds pretty good now that i have this volume control rigged up in front of it. i run the cd player into the volume pot then into the preamp this seems to work wonders it sounds really good now except for that it is still a humbug but the alternate schematic supplied with the kit should fix that.
i guess there is more to buying audio gear than simply plugging it in, components have to be matched.
some people were of the opinion that this design is poor but it sure seems to work fine now. i ordered some diodes to bring down the filament voltage.
i guess i could put some higher value resistors at the input or something so that i dont have to run cables through the extra volume control.
now if only all recordings were of top quality, in my cd collection there really arent that many that do justice to these tube amps.
thanks again for all the helpfull input
i guess there is more to buying audio gear than simply plugging it in, components have to be matched.
some people were of the opinion that this design is poor but it sure seems to work fine now. i ordered some diodes to bring down the filament voltage.
i guess i could put some higher value resistors at the input or something so that i dont have to run cables through the extra volume control.
now if only all recordings were of top quality, in my cd collection there really arent that many that do justice to these tube amps.
thanks again for all the helpfull input
Glad it's working - was it just being clipped by the raw CD level input then? I'm a bit confused as to what has changed.
As for CD quality, you may be surprised how shockingly bad the modern loudness enhanced CD really is.. the most important sonic attribute of a modern DAC is that it clips cleanly.
Oh, this isn't a mere opinion, it's a fact, provided that your schematic is correct. Extremely large anode resistor would work fine if B+ was also extremely high (1000V or more kind of high; this way you'd end up iin the linear portion of tube's operating area), but that (also high value) cathode resistor woudl bias the tube straight into cut-off which wouldn't sound like anything at all.
Given the values in your schematic the B+ is under 300V, and more likely closer to 250V. Input triodes operate with extremely low current (= very non-linear). Those component values would be on the high side for a tube such as ECC83/6N2P, let alone something like 6N1P you are using.
Instead of doubling the number of tubes a better result could be achieved by changing the loadline and operating point.
This design is a fine tube distortion "effect" but fine pre-amp it is not.
alright, ill have to chew on that for a while. im reading the
The Grounded-Cathode Amplifier
Determining cathode and plate resistor values
article from the tubecad journal website and it is going to take a little while to understand it well. i started reading it about 6 months ago and couldnt understand the first paragraph but now i can almost get through the whole thing and not be completely stumped.
ill have to check the values of those resistors again.
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