SY said:
No hard data... sorry.
But apparently it was audible in the phono or line stage for Spectral - which is how it was discovered, I seem to recall.
There are some very nice precision current and voltage sources out now that are *scary* low noise - why not use them??
I use them on the bias for WE417a as the front end of a phono stage, and they make bypassed zeners seem like "active white noise generators"... monster difference.
You could set them up as a mirror if you needed to pass more voltage/current than the device likes to handle directly, I would
expect?
_-_-bear
Re: Re: bias arrangements for P-P amps.
I've seen it used quite often and have taken up the habit on my schemas. Perhaps its rise has come because it can be reliably typed in on a keyboard. Getting an " W" sign to show up in an email or on-line post relies on having symbol font installed, knowing that symbol has an omega character, and hoping it shows up on someone else's computer (ie many Windows guys type in the fractions that come as high-bit characters on the PC -- these show up as gobbledegook on any other box, so you are left guessing what the poster means)
dave
rcavictim said:
I've seen it used quite often and have taken up the habit on my schemas. Perhaps its rise has come because it can be reliably typed in on a keyboard. Getting an " W" sign to show up in an email or on-line post relies on having symbol font installed, knowing that symbol has an omega character, and hoping it shows up on someone else's computer (ie many Windows guys type in the fractions that come as high-bit characters on the PC -- these show up as gobbledegook on any other box, so you are left guessing what the poster means)
dave
LA PIECE DE RESISTANCE.....
Hi,
No one is stopping you from "righting" Ohm, resistance or resistor(s) whenever appropriate....
Naturally you can now be expected to prefer your Single Ended Triode vacuum tube tone to be seved with slam...
Society won't go down the drain by using acronyms but your point is of course well taken.
7D out here.....
Cheers,
Hi,
No one is stopping you from "righting" Ohm, resistance or resistor(s) whenever appropriate....
Naturally you can now be expected to prefer your Single Ended Triode vacuum tube tone to be seved with slam...
Society won't go down the drain by using acronyms but your point is of course well taken.
7D out here.....
Cheers,
Frank,
I don't get your point about S.E.T. S.E.T. is an acronym that is accepted terminology in the audio world. R is not an acronym at all anywhere nor is it an engineering symbol for resistance. It has been used to represent a decimal point in the middle of numerically printed resistance values, but not to replace the omega symbol.
Just in case your S.E.T. comment was a jab because there is a school of thought that "S.E.T." and "slam" cannot be used in the same sentence, most of the time this is of course true, but I am running big 125 watt Pd 805's in such mode on near 100 db efficient array speakers containing 24 drivers per cabinet so slam is what I get in spades. Compared to almost everything else I have listened to, ....I prefer it.
Not being as lazy as some, even I while trying to make a point by example in the temperature comment managed to screw it up, because using improper technical terms is unnatural in my engineering world. What I should have said was it is cold here today at -20T. Since there are three standard temprature scales this information is of course useless information as posted.
I'm gonna go burn this soap box now for it's BTU value.
Happy, stress free holidays.
I don't get your point about S.E.T. S.E.T. is an acronym that is accepted terminology in the audio world. R is not an acronym at all anywhere nor is it an engineering symbol for resistance. It has been used to represent a decimal point in the middle of numerically printed resistance values, but not to replace the omega symbol.
Just in case your S.E.T. comment was a jab because there is a school of thought that "S.E.T." and "slam" cannot be used in the same sentence, most of the time this is of course true, but I am running big 125 watt Pd 805's in such mode on near 100 db efficient array speakers containing 24 drivers per cabinet so slam is what I get in spades. Compared to almost everything else I have listened to, ....I prefer it.
Not being as lazy as some, even I while trying to make a point by example in the temperature comment managed to screw it up, because using improper technical terms is unnatural in my engineering world. What I should have said was it is cold here today at -20T. Since there are three standard temprature scales this information is of course useless information as posted.
I'm gonna go burn this soap box now for it's BTU value.
Happy, stress free holidays.
Hi,
I agree but it is printed on all kinds of resistors by the manufacturers to distinguish between full ohmic ranges and higher precision units : 33 Ohm as opposed to 33R3 as an example.
Even in the case of 33 Ohm, as a single value for instance, you'll find manufacturers printing just 33R on the body of the resistor.
Another reason for them to do it this way besides the fact that it's just shorter is that it avoid confusion between 0 and O when used inbetween numerical characters.
Point is, I think, we all understood what was meant by the R symbol in this particular context....
Either way, I don't think it's worth making an issue out of it...
It wasn't.
And you.
Cheers,
I agree but it is printed on all kinds of resistors by the manufacturers to distinguish between full ohmic ranges and higher precision units : 33 Ohm as opposed to 33R3 as an example.
Even in the case of 33 Ohm, as a single value for instance, you'll find manufacturers printing just 33R on the body of the resistor.
Another reason for them to do it this way besides the fact that it's just shorter is that it avoid confusion between 0 and O when used inbetween numerical characters.
Point is, I think, we all understood what was meant by the R symbol in this particular context....
Either way, I don't think it's worth making an issue out of it...
It wasn't.
And you.
Cheers,
Bear, I looked at voltage fluctuations across some cheap red LEDs driven by a rough current source at 8 mA and 20 mA (a 15K power resistor attached to a regulated variable bench supply) with a fluorescent bulb just a few inches away. My scope isn't too reliable below 1 mV, but I couldn't see any 60 or 120 Hz action at that level. That's about 60dB down from the input signal. Add the common mode rejection at the PP output stage cathodes, and I think it's safe to forget about.
No doubt in non-differential stages handling microvolts (e.g., MC inputs), this could still be a factor, but not in a tens-of-volts situation.
No doubt in non-differential stages handling microvolts (e.g., MC inputs), this could still be a factor, but not in a tens-of-volts situation.
Good greif, I don't get how anal some people R.pedroskova said:
I've been an EE for a long time, and none of those I know have any difficulty discerning that R (in context) means ohms. Dave explained it longhand above so I won't bother reiterating.
As for W, well, I'll leave political discussions for elsewhere.
Especially inside a solid (not clear plastic) box.SY said:
@SY
Glad you brought up the idea of using a LED (acronym!) string for bias on a pair of PP EL84/6BQ5's. I've been thinking of that for years... As for as the self generated noise of the LED's, I'd assume if the string was common to the pair, it would cancel out if the pair were well matched. PP EL84 for my brother's PC, that's the idea! So keep us informed! Gotta get the younger generation hooked on tubes, hehe!
-0.3 deg F here this morning!
Wayne
Glad you brought up the idea of using a LED (acronym!) string for bias on a pair of PP EL84/6BQ5's. I've been thinking of that for years... As for as the self generated noise of the LED's, I'd assume if the string was common to the pair, it would cancel out if the pair were well matched. PP EL84 for my brother's PC, that's the idea! So keep us informed! Gotta get the younger generation hooked on tubes, hehe!
-0.3 deg F here this morning!
Wayne
Dear North Americans,
The use of the "R" to spec a resistor is European.
(where the heck do I find an "omega" on a mucrosoft Qwerty keyboard anyhow?? What's the secret key combination?? Grrr)
Don't be quite so isolated and parochial. Read some Euro electronics/audio mags - they're fun! Even in Italian, French and German! I can't read two of those worth a damn, and for one of them I have a 1st grade vocabulary... yippee!!
Sy,
Go for it.
You won't have any overload problems in a mirror, where the current setting device is isolated... but the LEDs ought to be ok I guess.
Myself, if possible I like to look at the noise floor and get it as low as possible in general... in tube amps that may not be so much of an issue as it might in soylent state. ymmv, as always!
_-_-bear
The use of the "R" to spec a resistor is European.
(where the heck do I find an "omega" on a mucrosoft Qwerty keyboard anyhow?? What's the secret key combination?? Grrr)
Don't be quite so isolated and parochial. Read some Euro electronics/audio mags - they're fun! Even in Italian, French and German! I can't read two of those worth a damn, and for one of them I have a 1st grade vocabulary... yippee!!
Sy,
Go for it.
You won't have any overload problems in a mirror, where the current setting device is isolated... but the LEDs ought to be ok I guess.
Myself, if possible I like to look at the noise floor and get it as low as possible in general... in tube amps that may not be so much of an issue as it might in soylent state. ymmv, as always!
_-_-bear
Hi,
Bear,
Just for info:
The asci key combination is ALT + 234 to get an Omega symbol.
I'll type it but I'm sure the forum software will make gibberish out of it:
Ù
One that does show properly is the mu symbol as used for microfarad for instance, the sequence ro type is ALT + 230
µ
It's the same thing really. You'd want as low a noise floor as possible with tubes as well.
Cheers,
Bear,
Just for info:
The asci key combination is ALT + 234 to get an Omega symbol.
I'll type it but I'm sure the forum software will make gibberish out of it:
Ù
One that does show properly is the mu symbol as used for microfarad for instance, the sequence ro type is ALT + 230
µ
It's the same thing really. You'd want as low a noise floor as possible with tubes as well.
Cheers,
What is the consensus here on other, more “modern” methods for biasing?
I am talking about using arrangement such as network with variable resistors or VR Chips for a continuously maintained bias. At least on paper they appear nice, but how do they stack-up sonically compared to the more traditional methods.
I know about one high-end audio company in India, which employs Chip controlled automatic bias for their EL34 PP amp ostensibly to allow uses of unmatched tubes.
I am talking about using arrangement such as network with variable resistors or VR Chips for a continuously maintained bias. At least on paper they appear nice, but how do they stack-up sonically compared to the more traditional methods.
I know about one high-end audio company in India, which employs Chip controlled automatic bias for their EL34 PP amp ostensibly to allow uses of unmatched tubes.
bear said:
The proper way to do it is to type in W in symbol font (symbol font is installed here & on any standard Mac, or Windoz install.
W
fdegrove said:
Use of any character with an ASCII value larger than 127 means you have a very good chance of it not showing up since those are the values that are defined differently on each platform... Franks omega shows up as a U with an umlat above it, the mu shows up. ''µ" option-m on my keyboard... it is just an m in symbol
m
dave
I haven't yet experimented with LEDs to replace cathode bias ohmic references but I have read a bit on the subject. On the issue of noise it appears that not all LEDs are born equal in this regard. IIRC the blue ones are reportedly much lower noise, and some of the worst are the very earliest red ones from back in the 70's.
Very cold. -27T when I packed it in late last night.
Very cold. -27T when I packed it in late last night.
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