Bottlehead Forum
General Category => General Discussion => Topic started by: ambd1 on February 06, 2024, 04:44:49 AM
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Hi all,
I am newbie in this forum, I am from VA. I would like to ask your help deciding between these two very well regarded tube preamplifiers, Moreplay and BeePre2.
My current system is a digital streamer going into a Mini DSP Flex, and the Mini DSP sending a full signal to a Rythmik subwoofer and sending a high pass signal with PEQ to a Apollon NCx500 amplifier, and then to a pair of NHT C3 speakers (6 ohm, 84 db). I also have a technics turntable with a phono preamplifier going into the Mini DSP via RCA.
My speaker cable is Duelund DCA16Ga
My ICS are all Belden 8492 (Yazaki style)
My plan is to place either the Moreplay or the BeePre2 between the Mini DSP and the Apollon amplifier, in that case the signal going to the subwoofer will not be affected by the tube preamplifier. Or, not ideal, I could place the tube preamplifier right before the Mini DSP (working as a proper preamplifier) and sending one pair of RCAs to the Mini DSP and then into the Apollon amplifier.
The input impedance of the Apollon amplifier is 50K
The input impedance of the Mini DSP Flex via RCA is 100K
The Apollon has 4 gain settings, I use it in third setting, but with the gain of the tube preamplifier I could use the second gain setting.
What I am looking for is to add a good amount of tube sound to this system. The Apollon Class D amplifier presents a wide solid soundstage, but vocals and strings do not have the best tone, neither 3d presence, and the sound all in all, is somehow cold and sometimes harsh in the midrange.
So, I would like what preamplifier, between the Moreplay or the BeePre2, would provide more of that tube sound and presence?
I can surely put together any of those two kits, with patience and time. I can solder, I do my own cables and I have done other type of more simple kits before.
As context, my experience with tube amplifiers is not small. I used to have a Conrad Johnson MV50, a 300B SET custom made amp, a 45 SET custom made amp, and a custom made DHT preamplifier around 6v6 (which unfortunately had some microphonic issues).
I just would like to bring some of that 3d imaging and amazing tube midrange to my current setup.
Thanks a lot for your time!!
Alan Brain
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Ideally you would present either of these preamps with your full source signal for optimal SNR. I'm guessing you plan to continue using the Mini DSP for level control?
If you put the preamp where you are wanting to, you'll lose the source selection ability, so that could be a major downside.
I think I'd lean toward the Moreplay for what you're talking about, as it's going to give a stronger tube flavoring and be easier to move around in your system. You also don't have to feed anything that's a particularly demanding load, so the advantages of the BeePre upgrades there aren't as meaningful.
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Ideally you would present either of these preamps with your full source signal for optimal SNR. I'm guessing you plan to continue using the Mini DSP for level control?
If you put the preamp where you are wanting to, you'll lose the source selection ability, so that could be a major downside.
I think I'd lean toward the Moreplay for what you're talking about, as it's going to give a stronger tube flavoring and be easier to move around in your system. You also don't have to feed anything that's a particularly demanding load, so the advantages of the BeePre upgrades there aren't as meaningful.
Thanks. I think you are right in that I do not need to feed anything with a demanding load. Also, in terms of gain, the Mini DSP Flex (working as preamp and crossover now) puts out 2 volts. And with that, and the third gain setting in the Apollon amplifier I am more than fine. So, taking this into account, your rationale about the Moreplay being a better fit for my needs makes sense.
I use the Mini DSP for several functions. I use it as crossover to send a high pass signal to amplifier for mains and full signal to the active subwoofer. I also use it to do some parametric EQ to the signal going to the mains, and also as a DAC. Since the Mini DSP has also a remote that control the 2V output, I use it as a preamplifier.
If I put the tube preamplifier before the Mini DSP which, as you suggest, I would need to connect a DAC to the tube preamplifier and remove the Mini DSP from DAC functions. If I put the tube preamplifier after the Mini DSP, since the Mini DSP is sending a high pass signal to amplifier for mains and a full signal to subwoofer, then the signal for the subwoofer will not be affected by the tube preamplifier.
I could try both positions and see how it sounds better. But I surely would prefer to have less components in the system.
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My current system is similar to yours in a couple of respects, and maybe my experience will be of some value. My digital steamer is feeding a DAC and my turntable feeds a phono-pre. The DAC and phono-pre both feed my Moreplay. The Moreplay outs feeds a 6-channel EQ. Everything up to this point is single-ended. The EQ's balanced outs feed a Hypex Nilai 500 Stereo Amp, which only has balanced input. The Nilai speaker outs feed my subwoofers speaker level inputs, and its speaker outs feed my speakers.
Regarding the pairing of the Moreplay with Class D, well it's superb. I also have a pair of ACA Class A monoblocks, 15W/channel. I prefer the Nilia to the ACA's.
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My current system is similar to yours in a couple of respects, and maybe my experience will be of some value. My digital steamer is feeding a DAC and my turntable feeds a phono-pre. The DAC and phono-pre both feed my Moreplay. The Moreplay outs feeds a 6-channel EQ. Everything up to this point is single-ended. The EQ's balanced outs feed a Hypex Nilai 500 Stereo Amp, which only has balanced input. The Nilai speaker outs feed my subwoofers speaker level inputs, and its speaker outs feed my speakers.
Regarding the pairing of the Moreplay with Class D, well it's superb. I also have a pair of ACA Class A monoblocks, 15W/channel. I prefer the Nilia to the ACA's.
Thanks for sharing your experience! I appreciate it and it is very helpful.
We, indeed, have a similar system in some elements in the chain. As I mentioned in my last post, I can try both ways and see what sounds better: either place the Moreplay (as you have it) before the EQ (in my case that would be before the Mini DSP Flex), or place it right after the Mini DSP. Each option has its own pros and cons that I would need to explore once the Moreplay is ready.
So, it seems, according to your experience, that the Moreplay is the way to go. In your case, was the Nilai a bit harsh without the Moreplay in the chain? How much did the sound change with the Moreplay in chain? and how did it change?
Thanks,
Alan
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Well, the Nilia is the latest addition so it's only seen duty with the Moreplay Preamp. While the Nilia has yet to be widely reviewed, it's gaining a reputation for being relatively laid back and smooth, for a Class D. I was interested in trying Class D with my Moreplay based on this thread, which might be of interest to you: https://forum.bottlehead.com/index.php?topic=15040.msg136232#msg136232 . I started looking for a good but not crazy expensive (<$1500) class D amp and ran across Alpha Audio's shoot out video that included the Nilia: https://www.youtube.com/live/NdZFAWe1Nxo?si=M8GmQq_vLfJuMTLX . Based on that video, listening to it using headphones, I felt the Nilia had the better sound, fairly close to Alpha Audio's reference amp, the Pass Labs X150.8. Listening to it might give you a sense of the Nilia's character compared to the much more expensive Pass Labs class A/B, and to class D Purifi and ICEpower.
I do have a solid state Schiit Saga preamp that was replaced by the Moreplay. I have been meaning to put it back in for comparison with my Moreplay. I will set that up in the next day or two and report back.
As a side note, I happen to have two Moreplays that I built at the same time, as an experiment to try to determine whether or not the upgrades are audible. One is stock and the other is heavily upgraded (pics attached). I have compared them and I have to admit that the stock unit is difficult to distinguish from the upgrade.
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Well, the Nilia is the latest addition so it's only seen duty with the Moreplay Preamp. While the Nilia has yet to be widely reviewed, it's gaining a reputation for being relatively laid back and smooth, for a Class D. I was interested in trying Class D with my Moreplay based on this thread, which might be of interest to you: https://forum.bottlehead.com/index.php?topic=15040.msg136232#msg136232 . I started looking for a good but not crazy expensive (<$1500) class D amp and ran across Alpha Audio's shoot out video that included the Nilia: https://www.youtube.com/live/NdZFAWe1Nxo?si=M8GmQq_vLfJuMTLX . Based on that video, listening to it using headphones, I felt the Nilia had the better sound, fairly close to Alpha Audio's reference amp, the Pass Labs X150.8. Listening to it might give you a sense of the Nilia's character compared to the much more expensive Pass Labs class A/B, and to class D Purifi and ICEpower.
I do have a solid state Schiit Saga preamp that was replaced by the Moreplay. I have been meaning to put it back in for comparison with my Moreplay. I will set that up in the next day or two and report back.
As a side note, I happen to have two Moreplays that I built at the same time, as an experiment to try to determine whether or not the upgrades are audible. One is stock and the other is heavily upgraded (pics attached). I have compared them and I have to admit that the stock unit is difficult to distinguish from the upgrade.
Very interesting, thanks for sharing. Where did you buy the Nilai? Did you bought it already assembled or in kit form? I am considering returning the Hypex (still have a couple of days) and ordering a Nilai, but not sure where.
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I bought the Hypex Nilai 500 Stereo Amplifier DIY Kit from Deer Creek Audio. https://deercreekaudio.com/products/ols/products/hypex-nilai-500-stereo-amplifier
The kit takes maybe an hour to assemble. No soldering required.
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I just remembered your first post mentioned the Apollon adjustable gain. The Nilia has three gain settings, 12, 22, and 28 dB. The Moreplay offers about 9 dB of gain if I recall correctly. I'm using the 12 dB setting on the Nilia and have built in a 3dB pad on my Moreplay to reduce its gain a bit too. My speakers are pretty high efficiency so I don't want a lot of gain.
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I just remembered your first post mentioned the Apollon adjustable gain. The Nilia has three gain settings, 12, 22, and 28 dB. The Moreplay offers about 9 dB of gain if I recall correctly. I'm using the 12 dB setting on the Nilia and have built in a 3dB pad on my Moreplay to reduce its gain a bit too. My speakers are pretty high efficiency so I don't want a lot of gain.
Thanks for sharing where you got the Nilai. I think that I will keep the NCx500 for now since it is pretty good at what it does. Also, in another forum, somebody who has more than 4 Class D amplifiers of this same caliber said that they all need tons of break in, at least 150 hours. And I sort of believe him. Although, I read somewhere that even Hypex said that their amplifier modules do not need break in.
As I move along and improve the sound, I may get a kit for the Nilai from Deer Creek, but I will have to talk to them for a Dual Mono option since my current speakers are only 84db so I would need the extra power the Dual Mono has.
It is very good to know that the stock Moreplay sounds very similar to the upgraded Moreplay. Does the upgraded Moreplay has just better capacitors and resistors? or the upgraded version has a different schematic with a more complex wiring?
Thanks for sharing all this valuable information with me.
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Hmbscot, what are the knobs on your modded moreplay?
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hmbscott .... you need to enter those modded kits into some type of contest .... all are just awesome!
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If you want some help laying out boxes with L-brackets, that opens up a lot of possibilities.
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Paul, I have been admiring your build portfolio. I've reviewed it several times after I discovered it. You sir are an artist! I may take you up on that someday. (edit: I'm a little red faced Paul, I just realized your comment probably wasn't aimed at me, nevertheless I may hit you up for advice some day).
joralieu, I bought four different types and decided I liked these the best: https://www.amazon.com/gp/product/B08L4XYYFV/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
Mucker, your kind words are much appreciated!
Thanks, Scott
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In your case, was the Nilai a bit harsh without the Moreplay in the chain? How much did the sound change with the Moreplay in chain? and how did it change?
Alan,
This evening I hooked my Saga back up and did some listening comparing it and the Moreplay. Cable swapping isn't ideal, and results are interesting enough that I want set them up for up for a proper A/B test. My initial impression is that the differences are not enormous, but may be audible. With the Saga in the chain, the treble region is sharper/harder, but not exactly harsh. I noticed this with a couple of songs with high-pitched, high-volume content, Numb on Portshead's Dummy Album and Adele's Hello on her 25 album. Sound stage and imaging are similar. I was surprised that the Saga is as sweet sounding as it is, which is why I want to do proper A/B testing.
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Alan,
This evening I hooked my Saga back up and did some listening comparing it and the Moreplay. Cable swapping isn't ideal, and results are interesting enough that I want set them up for up for a proper A/B test. My initial impression is that the differences are not enormous, but may be audible. With the Saga in the chain, the treble region is sharper/harder, but not exactly harsh. I noticed this with a couple of songs with high-pitched, high-volume content, Numb on Portshead's Dummy Album and Adele's Hello on her 25 album. Sound stage and imaging are similar. I was surprised that the Saga is as sweet sounding as it is, which is why I want to do proper A/B testing.
Thanks for comparing the sound with the Saga and with the Moreplay in the system. Your experience is really interesting and, for me at least, somehow unexpected as I have read in many forums that the Saga did not bring much to the sound in comparison with a real tube preamplifier, such as the Moreplay. But, as you mentioned, you may need to properly set up an A/B test (taking careful account of gain in both cases) to have a confirmation. I exchanged some emails with Schitt technical people some weeks ago, and they confirm that according to their experience, their tube device that could bring more ¨tube¨ sound to a given system is their Freya +.
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I did a bit of AB testing and the Saga sounds great! I don't hear even a hint of harshness. If I had never listened to the Moreplay I would be totally satisfied with pairing it to the Nilia.
While the differences are subtle, they add up. The Moreplay is more immersive, engaging, and less fatiguing, but it's not soft or mellow. Percussion is sharp, startling, tight. Subtle texture is more distinct and voices better articulated. Instruments are more full and musical especially noticeable with piano, guitar, and bells. High volume high pitched passages are smoother, sweeter, less shrill. It gets me a little closer to experiencing a performance rather than hearing a recording.
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Thanks for doing the AB testing. It is very helpful. Kudos to the Saga, but surely the Moreplay had to produce a more engaging sound. Then, the Moreplay it is for me.
Having said that, I did overlook a complex issue in my system and I would like to ask your help with ideas on how to solve it.
As I explained, I have a Mini DSP being used as DAC, source selector and also crossover, sending one low pass signal with EQ to the subwoofer via RCA, and one high pass signal with EQ to the NCx500 amplifier via RCA, for the main speakers. And surely, I control the volume of the whole system with the MiniDSP volume knob. This knob controls the 2 volt max of both RCA outputs, at the output stage, going from 0 to 2 volts.
In order to introduce some tube sound without much complications, the ideal place for the tube preamplifier would be after the Mini DSP. But, in this case, the problem is that the tube preamplifier will not receive a full signal level but rather a signal going from 0 volts to 1.4 volts (because the MiniDSP is controlling the volume through the volts in its RCA output).
So, the input signal received by the tube preamplifier will vary depending on the volume. And I think that is not what a preamp expects, since most preamplifiers are designed to receive input signals with a predefined voltage and control the output signal to the power amplifier by adjusting the gain of the preamplifier stages.
In short, at low or mid listening levels, the signal sent from the MiniDSP to the preamplifier will be too weak and will probably degrade SNR and distortion performance in the tube preamplifier.
If, on the other hand, I place the tube preamplifier before the MiniDSP, I would need the tube preamplifier to have all the input sources I need, since it would act a source selector, but it would also need to be a unity gain preamplifier of some sorts, because the RCA input of the MiniDSP cannot take more than 2 volts.
I am thinking (but most likely I am missing something) that my best option may be to find, commission, or build a unity gain tube preamplifier with as many sources as I need.
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If, on the other hand, I place the tube preamplifier before the MiniDSP, I would need the tube preamplifier to have all the input sources I need, since it would act a source selector, but it would also need to be a unity gain preamplifier of some sorts, because the RCA input of the MiniDSP cannot take more than 2 volts.
This is what you want to do. 2V is a pretty hefty amount of signal and the Moreplay doesn't have a whole ton of gain. You can also add a couple of resistors to the volume control if you need to in order to set the gain to unity.
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This is what you want to do. 2V is a pretty hefty amount of signal and the Moreplay doesn't have a whole ton of gain. You can also add a couple of resistors to the volume control if you need to in order to set the gain to unity.
Thanks Paul. Yes, you are right, that would be probably the ideal scenario and if the Moreplay is close to unity gain then that is great.
In this scenario, the Mini DSP will receive around 2V or bit less from the Moreplay, and it will work as a EQ, crossover, and master volume control for the whole system. Also, in this scenario, my gain structure on the amplifier side will stay the same, which I like a lot.
I am not so good at modifying schematics but I can ask for advice here on how to deal with those resistors when the time comes. My sources are just two: DAC (together with bluetooth in the same device) and the phono preamplifier coming from turntable. In that regard, the Moreplay has two sources input or just one?
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The Moreplay has three inputs and two outputs. The outputs are both active all the time.
I added an Lpad to my Moreplay to reduce the gain a tad. The Moreplay normally will output 5.5V with a 2V input. I just calculated a new Lpad that will change that to unity gain, 2Vin >>> 2Vout. See the drawing, it specifies the resistor type I used. Mouser caries them, both values are in stock. Paul, please correct me if I got this wrong.
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FWIW, I reduced the gain on my Moreplay a while back using 2W TKD resistors (7.5K and 3.3K) on the stock pot. They are overkill for certain but very effective and less than $10 total. Pic is a visual for reference. For unity gain, it sounds like using Scott's calculated one's in place of the one's I used?? Interesting discussion and thanks (all) for the info about making a unity gain Moreplay.
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The resistor power rating required is quite low. Power dissipation based on a fixed voltage input is V^2/R = Watts. Assuming the highest voltage drop of 5.5V and the lowest resistance mentioned, that's 5.5^2/3300 = 1/100 of a watt. Any larger resistor will dissipate less power.
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The Moreplay has three inputs and two outputs. The outputs are both active all the time.
I added an Lpad to my Moreplay to reduce the gain a tad. The Moreplay normally will output 5.5V with a 2V input. I just calculated a new Lpad that will change that to unity gain, 2Vin >>> 2Vout. See the drawing, it specifies the resistor type I used. Mouser caries them, both values are in stock. Paul, please correct me if I got this wrong.
Hi Scott!
Thanks a lot for taking the time to modify the schematic of the Moreplay for Unity gain. I really appreciate it. And 3 inputs is more than what I need. I will order the kit this week, and I will start putting together the preamplifier next weekend!
If I understood correctly, the only extra pieces I need to buy to achieve unity gain are those two resistors, is that right? because there is an L Pad in the kit I think.
And lastly, it would be good for me to not just solder but understand (even if it is just on a surface level) what is happening in the circuit. Is there any book that you would recommend to somebody to start understanding basic electronic principles for tube amplification?
Once again, thank you and everybody for being so helpful.
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Alan, The two resistors are the Lpad (that term just is the name for connecting resistors to a signal input in that configuration) and yes, they are the only thing you need. You will connect them to the volume pot that comes with the kit. Note that you need two of each resistor, one for the left channel and one for the right channel. The kit doesn't include an Lpad.
Congrats on that choice, I'm sure you will enjoy both the process of building it and listening! And you will be amazed by the incredible value it represents.
One pretty good site to learn about tube tech is The Valve Wizard and this page is a good place to start: http://www.valvewizard.co.uk/gainstage.html. The author is British so some of the terminology differers from American terms.
The Moreplay, and most Bottlehead circuits are triode based and the majority are of the type known as common-cathode, which means the cathode is connected the ground circuit, usually with a low value resistor (hundreds of ohms) that sets it's bias. Bottlehead designs are not simple triode circuits though. They include several sophisticated and in some cases unique circuit designs that set apart their circuits in ways that contribute both their ease of construction, but more importantly, their superior performance.
Here's a bit of terminology can get you started on understanding the material, forgive me if you already know all this, but if you don't, it will really help comprehending the information at the beginning.
Valve - Britt's term for tube.
Common - refers to the ground circuit and basically means grounded. It comes from the fact that all parts of the circuit that a grounded are connected to the same "common" ground. By convention it is zero volts in the circuit and all other voltages are defined in reference to the ground being zero volts. You may also see a term "referenced to ground" which means either connected directly to ground with a wire, or with a resistor. Using a resistor will introduce a voltage offset if current flows (see Ohm's Law below).
Triode - A tube with three connections, Cathode, Grid, and Plate or Anode
- The Cathode is heated to allow it to freely emit electrons.The cathode is held at a low slightly positive voltage typically
- The Plate is held at a high positive voltage and will attract electrons from the cathode
- The Grid is an open mesh electrode between the cathode and plate. By being placed so it's voltage is what the cathode experiences rather that the plate voltage, which the cathode would experience if there were no grid. The grid's voltage is modulated by the audio signal. By doing so it reduces electron flow from the cathode when the voltage dips and increases electron flow when the voltage rises. This causes a modulated current to flow to the plate, and that current passes through a load resistor producing a much larger voltage audio output signal (again see Ohm's Law below to understand the idea of a resistor converting current to voltage).
Bias - refers to setting the zero signal voltage relationships between the cathode, grid and plate. This is a design parameter that sets a tube to operate in a range of voltages suitable for the circuit's function. In the simplest case, bias is set with resistors connected either to ground or the B+ voltage, also called rail voltage or "rails".
B+ - refers to the high positive voltage that's provided by the amplifier power supply. Ideally it will remain a a fixed positive voltage typically in the 150 - 600 VDC range for tube amplifiers, the specific value depends on the operating needs of the tube type used. How well the power supply is designed will have a huge influence on how stable that voltage is under varying load and how free it is of AC ripple and noise. Any variation in B+ will result in unwanted modulation in the output audio signal, which is why power supply design is so critical. BTW, Britts call B+ "HT", short for High Tension. Tension is an old-timey British term for voltage.
Ohm's Law - This is super useful in understanding resistors: V = I X R, Voltage = Current times Resistance. The units are volts, amps, and ohms. This equation can be used to calculate bias voltages etc.
The Power Law - This allows you to calculate power if you know the voltage and current: P = V X I, Power is equal to Voltage times Current. The units are Watts, Volts and Amps.
Combining Ohms's Law and the Power Law allows calculating all kinds of useful things, like power dissipation in wire or resistors, speaker power output, and amp loads etc. One common way to use the combined equations is to substitute for voltage in the Power Law from Ohm's law, which gives this equation:
- P = I^2 X R This can tell you how much power is dissipated by wire or a resistor or a speaker if a constant current source is connected to it. If you substitue for current instead you get this equation.
- P = V^2/R This can tell you power is dissipated if a constant voltage source is connected.
These are the most important equations for understanding what electrical circuits are doing, and as you can see, they are surprisingly simple. But it's quite amazing how deeply your insight can be by learning how to apply them.
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Alan, The two resistors are the Lpad (that term just is the name for connecting resistors to a signal input in that configuration) and yes, they are the only thing you need. You will connect them to the volume pot that comes with the kit. Note that you need two of each resistor, one for the left channel and one for the right channel. The kit doesn't include an Lpad.
Congrats on that choice, I'm sure you will enjoy both the process of building it and listening! And you will be amazed by the incredible value it represents.
One pretty good site to learn about tube tech is The Valve Wizard and this page is a good place to start: http://www.valvewizard.co.uk/gainstage.html. The author is British so some of the terminology differers from American terms.
The Moreplay, and most Bottlehead circuits are triode based and the majority are of the type known as common-cathode, which means the cathode is connected the ground circuit, usually with a low value resistor (hundreds of ohms) that sets it's bias. Bottlehead designs are not simple triode circuits though. They include several sophisticated and in some cases unique circuit designs that set apart their circuits in ways that contribute both their ease of construction, but more importantly, their superior performance.
Here's a bit of terminology can get you started on understanding the material, forgive me if you already know all this, but if you don't, it will really help comprehending the information at the beginning.
Valve - Britt's term for tube.
Common - refers to the ground circuit and basically means grounded. It comes from the fact that all parts of the circuit that a grounded are connected to the same "common" ground. By convention it is zero volts in the circuit and all other voltages are defined in reference to the ground being zero volts. You may also see a term "referenced to ground" which means either connected directly to ground with a wire, or with a resistor. Using a resistor will introduce a voltage offset if current flows (see Ohm's Law below).
Triode - A tube with three connections, Cathode, Grid, and Plate or Anode
- The Cathode is heated to allow it to freely emit electrons.The cathode is held at a low slightly positive voltage typically
- The Plate is held at a high positive voltage and will attract electrons from the cathode
- The Grid is an open mesh electrode between the cathode and plate. By being placed so it's voltage is what the cathode experiences rather that the plate voltage, which the cathode would experience if there were no grid. The grid's voltage is modulated by the audio signal. By doing so it reduces electron flow from the cathode when the voltage dips and increases electron flow when the voltage rises. This causes a modulated current to flow to the plate, and that current passes through a load resistor producing a much larger voltage audio output signal (again see Ohm's Law below to understand the idea of a resistor converting current to voltage).
Bias - refers to setting the zero signal voltage relationships between the cathode, grid and plate. This is a design parameter that sets a tube to operate in a range of voltages suitable for the circuit's function. In the simplest case, bias is set with resistors connected either to ground or the B+ voltage, also called rail voltage or "rails".
B+ - refers to the high positive voltage that's provided by the amplifier power supply. Ideally it will remain a a fixed positive voltage typically in the 150 - 600 VDC range for tube amplifiers, the specific value depends on the operating needs of the tube type used. How well the power supply is designed will have a huge influence on how stable that voltage is under varying load and how free it is of AC ripple and noise. Any variation in B+ will result in unwanted modulation in the output audio signal, which is why power supply design is so critical. BTW, Britts call B+ "HT", short for High Tension. Tension is an old-timey British term for voltage.
Ohm's Law - This is super useful in understanding resistors: V = I X R, Voltage = Current times Resistance. The units are volts, amps, and ohms. This equation can be used to calculate bias voltages etc.
The Power Law - This allows you to calculate power if you know the voltage and current: P = V X I, Power is equal to Voltage times Current. The units are Watts, Volts and Amps.
Combining Ohms's Law and the Power Law allows calculating all kinds of useful things, like power dissipation in wire or resistors, speaker power output, and amp loads etc. One common way to use the combined equations is to substitute for voltage in the Power Law from Ohm's law, which gives this equation:
- P = I^2 X R This can tell you how much power is dissipated by wire or a resistor or a speaker if a constant current source is connected to it. If you substitue for current instead you get this equation.
- P = V^2/R This can tell you power is dissipated if a constant voltage source is connected.
These are the most important equations for understanding what electrical circuits are doing, and as you can see, they are surprisingly simple. But it's quite amazing how deeply your insight can be by learning how to apply them.
Scott, thanks a lot for the explanation and the links!!! I really appreciate it. I got a little derailed since we started a new project at home. I will surely read the Valve Wizard site.