audio filter question | Poal: Say what you want.

[–] • 0 pt

thanks for input ill avoid it until I find or can design build what I want. why I posted it I knew you could see it for what it is.

My main objective was focusing on signal conversion and using a tube to let me amplify signal enough to meet amplifier's max input voltage gain needing no more than 25% and producing far more rated output with one crisp ass input signal outputting clean tonality, and musically blissful tubes are known for. I personal think they are better but that is my opinion.

So what I gather off your last post ill have to put a Low Pass before or after speaker line impedance is changed to remove any frequencies above say 120hz, then using a voltage regulator, smoothing filter and some capacitors, I can properly power the tubes preamp, run signal through to a Class D output modified to be RCA.

To answer the other question about the outputs I would need 8 channels for the front and 3 channels in rear maybe more as not sure on how many channels that depends on if I run a 3way component or just a set of 2/3 way coaxial's in doors for fill. I prefer doing a complete rear sound stage like the front so passengers can enjoy the same music as the front so possibly 7 channels in rear so between 11-15 channels when completed and depending on how far I got in rear. super complexity would come if I wanted to make each channel seperate which I taking a wild guess would require a High/Low pass filter network for each channel so they were define for a purpose. if I have to do that I would need up front 1 Mono, 3 Stereo Channels Mid-Bass, Mid-Range and Tweeter, Rear would need 1 Mono and 1-3 stereo channels. i would place outputs like so

In theory I suppose I'm trying to do similar as that "Nama" amp. they are using high and/or low level running through tube preamp and using the class d solid state eff to boost speakers.

I'm trying to convert the high level input into a signal to run through a tube preamp then through a Class D amplifier that outputs a RCA signal instead of outputs for speakers where I want to build a amplifier tube Line-Out Converter for the amplifiers that will power the speakers. might be far fetched but it is a interesting idea and I'd like to see how it affects the performance of amplifier classes. I know there are plenty of Converters but they are tubed and if something and be tubed then lets tube it

thanks for input ill avoid it until I find or can design build what I want. why I posted it I knew you could see it for what it is. My main objective was focusing on signal conversion and using a tube to let me amplify signal enough to meet amplifier's max input voltage gain needing no more than 25% and producing far more rated output with one crisp ass input signal outputting clean tonality, and musically blissful tubes are known for. I personal think they are better but that is my opinion. So what I gather off your last post ill have to put a Low Pass before or after speaker line impedance is changed to remove any frequencies above say 120hz, then using a voltage regulator, smoothing filter and some capacitors, I can properly power the tubes preamp, run signal through to a Class D output modified to be RCA. To answer the other question about the outputs I would need 8 channels for the front and 3 channels in rear maybe more as not sure on how many channels that depends on if I run a 3way component or just a set of 2/3 way coaxial's in doors for fill. I prefer doing a complete rear sound stage like the front so passengers can enjoy the same music as the front so possibly 7 channels in rear so between 11-15 channels when completed and depending on how far I got in rear. super complexity would come if I wanted to make each channel seperate which I taking a wild guess would require a High/Low pass filter network for each channel so they were define for a purpose. if I have to do that I would need up front 1 Mono, 3 Stereo Channels Mid-Bass, Mid-Range and Tweeter, Rear would need 1 Mono and 1-3 stereo channels. i would place outputs like so |front-left | front-right | | front-sub | | rear-left | rear-right | | rear-sub | In theory I suppose I'm trying to do similar as that "Nama" amp. they are using high and/or low level running through tube preamp and using the class d solid state eff to boost speakers. I'm trying to convert the high level input into a signal to run through a tube preamp then through a Class D amplifier that outputs a RCA signal instead of outputs for speakers where I want to build a amplifier tube Line-Out Converter for the amplifiers that will power the speakers. might be far fetched but it is a interesting idea and I'd like to see how it affects the performance of amplifier classes. I know there are plenty of Converters but they are tubed and if something and be tubed then lets tube it

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[–] • 0 pt

I think you're diving into a deep project here, so my advice would be to first learn about vacuum electronics and how they work, what kind of voltages you need, and how they respond to things like filament voltage fluctuations and differing noise profiles. Do this before you commit to using antique electronics in your project - there are better and cleaner ways of doing what you want, and tubes won't add anything to the audio stream if they're operated in the correct range. Literally, if you're getting coloring in the audio your circuit is broken. Fix it.

One of those cheap Chinese preamp kits from Aliexpress using 6J1 Pentodes is a good start. Those kits are terrible, but they'll teach you about tubes and how they work when not run optimally. Just don't use those with your good audio gear, they can have strange things on the output when turned off. Get a good meter and maybe even one of those meterscopes so you can poke around. (Don't buy 12AX7 tubes from there. Just don't. Go to hamtubes.com or someplace and get them.)

If you're really intending to use tubes in the preamp, then don't worry about anything before or after this circuit - that's all not relevant. As long as you give it the input it needs and get the output you want, the rest of the information can be worked out as you install it. There are plenty of circuits out there using things like the 12AX7, 14N7, etc...just look around. Just make sure you pick the circuit for what you want, as various tubes are rated for different kinds of amplification or oscillation, as well as various types of rough or normal service, and microphonics, etc.

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[–] • 1 pt

here is my starting point if you dont mind looking over it and commenting on it

Design Overview Speaker-Level Input to Line-Level Output (Impedance Conversion):

convert the high impedance (speaker-level) signal into a low impedance (line-level) signal suitable for RCA outputs. the first stage of the circuit must handle the high-voltage, high-impedance signal and safely convert it to a lower impedance (typically 10kΩ or less for RCA line-level).

Transformer-based can be used here. A step-down transformer with a 1:10 ratio for example. using a transformer is preferable to minimize noise and distortion, especially in a noisy automotive environment.

Voltage Regulation and Stabilization for Tube:

The 6SL7GT tube requires 6.3V for its heater (filament), and the anode (plate) voltage needs to be regulated around 150V to operate in Class A configuration. Since my vehicle's electrical system provides 14-14.7V, I need a voltage regulator and power supply circuitry to convert this down to the necessary voltage rails for both the tube filament and plate. For the tube heater: A DC-DC converter or linear regulator can be used to step down 14V to the 6.3V required for the filament. For the anode: A boost converter or step-up transformer can step up the voltage to the 150V required for the plate, ensuring stability and minimal distortion.

Class A Thermionic Tube Amplifier Stage:

the signal is passed through the Class A tube amplifier stage. The 6SL7GT tube is used here as a voltage amplifier to boost the line-level signal and provide the desired output range. In Class A operation, the tube remains in the active region throughout the signal cycle, providing clean, distortion-free amplification.

Output Stages (Multiple Channels):

Your circuit will provide multiple RCA outputs channels Buffered output stages are needed here to ensure that the impedance of the output doesn't affect the signal. Op-amps can be used after the tube to drive multiple RCA outputs with adequate current. Gain control can be implemented either through potentiometers to adjust the output for each channel to match the desired voltage levels.

Failsafes and Protection:

To prevent damage to the tube or the circuit from voltage spikes, include Zener diodes or transient voltage suppressors (TVS) to clamp high-voltage spikes. A fuse on the input voltage and the output RCA lines can prevent damage to the circuit and the connected equipment. proper heat sinking and ventilation are important for reliable operation. Additionally, use thermal cutoffs PTC thermistors in the heater circuit to prevent overheating. current-limiting resistors or active current-limiting circuits to protect the tubes from excessive current draw.

thanks for the reply. I drew up a design overview of the project. i got lucky and found a legit class tube amp made by butler audio, though i have no schematics to learn found im sure i can schematics for each design stage for something else and mix them all together. here is my starting point if you dont mind looking over it and commenting on it Design Overview Speaker-Level Input to Line-Level Output (Impedance Conversion): convert the high impedance (speaker-level) signal into a low impedance (line-level) signal suitable for RCA outputs. the first stage of the circuit must handle the high-voltage, high-impedance signal and safely convert it to a lower impedance (typically 10kΩ or less for RCA line-level). Transformer-based can be used here. A step-down transformer with a 1:10 ratio for example. using a transformer is preferable to minimize noise and distortion, especially in a noisy automotive environment. Voltage Regulation and Stabilization for Tube: The 6SL7GT tube requires 6.3V for its heater (filament), and the anode (plate) voltage needs to be regulated around 150V to operate in Class A configuration. Since my vehicle's electrical system provides 14-14.7V, I need a voltage regulator and power supply circuitry to convert this down to the necessary voltage rails for both the tube filament and plate. For the tube heater: A DC-DC converter or linear regulator can be used to step down 14V to the 6.3V required for the filament. For the anode: A boost converter or step-up transformer can step up the voltage to the 150V required for the plate, ensuring stability and minimal distortion. Class A Thermionic Tube Amplifier Stage: the signal is passed through the Class A tube amplifier stage. The 6SL7GT tube is used here as a voltage amplifier to boost the line-level signal and provide the desired output range. In Class A operation, the tube remains in the active region throughout the signal cycle, providing clean, distortion-free amplification. Output Stages (Multiple Channels): Your circuit will provide multiple RCA outputs channels Buffered output stages are needed here to ensure that the impedance of the output doesn't affect the signal. Op-amps can be used after the tube to drive multiple RCA outputs with adequate current. Gain control can be implemented either through potentiometers to adjust the output for each channel to match the desired voltage levels. Failsafes and Protection: To prevent damage to the tube or the circuit from voltage spikes, include Zener diodes or transient voltage suppressors (TVS) to clamp high-voltage spikes. A fuse on the input voltage and the output RCA lines can prevent damage to the circuit and the connected equipment. proper heat sinking and ventilation are important for reliable operation. Additionally, use thermal cutoffs PTC thermistors in the heater circuit to prevent overheating. current-limiting resistors or active current-limiting circuits to protect the tubes from excessive current draw.

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[–] • 0 pt

Speakers are high-LEVEL, as in lots of power. If you're using a transformer, you're going to need to run an output transformer in reverse because you want to match the output impedance of your device. These types of transformers tend to only be a few watts, with bigger ones being unobtanium or very expensive. Just slapping transformer in there without considering what you're talking to is recipe for disaster.

On RCA things - RCA refers to the jack type, not the signal present therein. Yes, in audio, RCA jacks tend to refer to line level I/O, but you can find a lot of things on those, including video and low-level RF. It's best to describe the signal level you want as opposed to the jack type.

If your vehicle's electrical system is providing almost 15 volts, stop. You have a problem.

6SL7GT tubes can be upwards of $50 per, check tubesandmore.com. Bob @ hamtubes.com sells them for less if he has any. The *SL7 is a hi-mu (gain) tube, and may be too hot for what you're trying to do. The *SN7 is probably a better choice here, being a medium mu device. High mu is typically more for phono level inputs, you may find you have too much gain. Remember that you don't need massive amounts of gain if all you need is 1Vp/p input on your device. Don't try and drive it to the max, keep it fully within it's linear range and everyone will sound happy. All of those are octal tubes, and take up space, and have limited shielding options. You're better off using the decent russian 12AX7 tubes here, as you can get shielded sockets with spring-loaded clamps for miniature tubes. Also remember that tubes don't just "take line and give more out," you need to specify your inputs as well. The 6SL7 needs a decent voltage drive to operate, somewhere in the order of 3V peak.

If you're already at line level, you don't need to boost anything. This is what you want for your next amp. You want a voltage follower (buffer amp) at this point providing 1:1 output.

You don't just give them voltage and they work - there's a lot of calculations that you're going to need to do, or other parts needed to properly bias the tubes. A tube uses a resistor on the plate and the cathode to develop the voltage you want during amplification. Tubes are purely a voltage device, and without some biasing it's not going to do anything because you can't get that voltage change without something to cause that change. Yes, op-amps are a perfect choice for break-out amplifiers, but you can get ulta-clean instrumentation amps. Why stick a noisy, dirty, nasty vibraty microphonic tube in there to ruin the sound? Get some OPA1637, they have a THD in the dirt. Adding transformers in here and other conversion devices is going to pop your harmonic distortion up to measurable ranges. Transformers suck, it's why we don't use them for audio anymore.

The rest of the crap is black-box nonsense. It's technically correct, but it's like sending you to the hardware store to get a lightbulb. Which one, they have hundreds.

You're going to get a lot better, more accurate sound by using audio op-amps (or transistors if you're a masochist) for your system. It will absolve you of all of the crap a tube needs to run, and all you'll need is a simple negative voltage converter for the rails on the op-amps.

I have no idea what that article is talking about. Speakers are low impedance - typically 1 to 8 ohms, with more exotic speakers being used in direct drive systems that have an impedance between 8 and 100 ohms. You usually only find that in pocket radios from the past, cars typically ran 3.2 or 4 ohms for their speakers. Speakers are high-LEVEL, as in lots of power. If you're using a transformer, you're going to need to run an output transformer in reverse because you want to match the output impedance of your device. These types of transformers tend to only be a few watts, with bigger ones being unobtanium or very expensive. Just slapping transformer in there without considering what you're talking to is recipe for disaster. On RCA things - RCA refers to the jack type, not the signal present therein. Yes, in audio, RCA jacks tend to refer to line level I/O, but you can find a lot of things on those, including video and low-level RF. It's best to describe the signal level you want as opposed to the jack type. If your vehicle's electrical system is providing almost 15 volts, stop. You have a problem. 6SL7GT tubes can be upwards of $50 per, check tubesandmore.com. Bob @ hamtubes.com sells them for less if he has any. The *SL7 is a hi-mu (gain) tube, and may be too hot for what you're trying to do. The *SN7 is probably a better choice here, being a medium mu device. High mu is typically more for phono level inputs, you may find you have too much gain. Remember that you don't need massive amounts of gain if all you need is 1Vp/p input on your device. Don't try and drive it to the max, keep it fully within it's linear range and everyone will sound happy. All of those are octal tubes, and take up space, and have limited shielding options. You're better off using the decent russian 12AX7 tubes here, as you can get shielded sockets with spring-loaded clamps for miniature tubes. Also remember that tubes don't just "take line and give more out," you need to specify your inputs as well. The 6SL7 needs a decent voltage drive to operate, somewhere in the order of 3V peak. If you're already at line level, you don't need to boost anything. This is what you want for your next amp. You want a voltage follower (buffer amp) at this point providing 1:1 output. You don't just give them voltage and they work - there's a lot of calculations that you're going to need to do, or other parts needed to properly bias the tubes. A tube uses a resistor on the plate and the cathode to develop the voltage you want during amplification. Tubes are purely a voltage device, and without some biasing it's not going to do anything because you can't get that voltage change without something to cause that change. Yes, op-amps are a perfect choice for break-out amplifiers, but you can get ulta-clean instrumentation amps. Why stick a noisy, dirty, nasty vibraty microphonic tube in there to ruin the sound? Get some OPA1637, they have a THD in the dirt. Adding transformers in here and other conversion devices is going to pop your harmonic distortion up to measurable ranges. Transformers suck, it's why we don't use them for audio anymore. The rest of the crap is black-box nonsense. It's technically correct, but it's like sending you to the hardware store to get a lightbulb. Which one, they have hundreds. You're going to get a lot better, more accurate sound by using audio op-amps (or transistors if you're a masochist) for your system. It will absolve you of all of the crap a tube needs to run, and all you'll need is a simple negative voltage converter for the rails on the op-amps.

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