Not if the two channels are decoupled. Like you said facts are facts. The two output tubes are decoupled by a capacitor across the cathode resistor.
I had a similar experience experimenting with two solid state amps that shared a single battery. I did not use a cap for the battery, and got a mono signal. I used a capacitor across the battery and lo and behold stereo!
Facts are facts. My 300B amp has a 15-40kHz response, very wide stereo separation and soundstage, measurable and audible.
What is your definition of hi-fi? Now we are talking opinion and not facts.
Gabe
Facts!
What i was asking is the amplitude variation across the frequency spectrum....
In your circuit as the frequency gooes down...the crosstalk will encrease...
Because of that i ask the amplitude of the crosstalk at 50 HZ.
By the way...crosstalk is not related to power suply noise!!...
Jorge
What i was asking is the amplitude variation across the frequency spectrum....
In your circuit as the frequency gooes down...the crosstalk will encrease...
Because of that i ask the amplitude of the crosstalk at 50 HZ.
By the way...crosstalk is not related to power suply noise!!...
Jorge
Tube_dude,
Of course not, but the amplitude of cross talk is in relation to any other noise in my statement. In other words, what I meant was that one will hear more noise from the power supply before one hears crosstalk.
As for the measurement I made, it was with 20 Hz, 200 Hz, 1kHz, and 10kHz.
Crosstalk will increase for lower frequencies only if the cathode bypass capacitor is not large enough.
I will measure the 300b again this evening and give you numbers, if you wish. And I will not pad the numbers or lie. If I am wrong I will say so. However, I do not think it will be quite the same with the 2A3.
Oh, I did say I wouldn't add more input didn't I.
Gabe
Of course not, but the amplitude of cross talk is in relation to any other noise in my statement. In other words, what I meant was that one will hear more noise from the power supply before one hears crosstalk.
As for the measurement I made, it was with 20 Hz, 200 Hz, 1kHz, and 10kHz.
Crosstalk will increase for lower frequencies only if the cathode bypass capacitor is not large enough.
I will measure the 300b again this evening and give you numbers, if you wish. And I will not pad the numbers or lie. If I am wrong I will say so. However, I do not think it will be quite the same with the 2A3.
Oh, I did say I wouldn't add more input didn't I.
Gabe
results of testing
OK all,
Here are the results of my test: the amp is a 300b SE amp using a common DC power supply with both filaments in parallel, with a 500 ohm pot connecting the ends, and a 360 ohm common cathode resistor bypassed by a 47µF cap (note, not 470µF as I recommend in the 2A3). Both channels have a non-inductive 8 ohm load. The right channel is driven to full output just before clipping. This is measured at the output.
right channel
20 Hz 15Vp-p
200Hz "
2kHz "
20kHz "
left channel
20 Hz 5Vp-p
200Hz 1Vp-p
2kHz 0.5Vp-p
20kHz 0.5vp-p
So as expected, lower frequencies had more crossover... but WAIT! I put another 47µF cap across the first one. The results?
Right Channel
20 Hz 15Vp-p
200Hz "
2kHz "
20kHz "
Left Channel
20 Hz 2Vp-p
200Hz 0.5Vp-p
2kHz 0.5Vp-p
20kHz 0.5Vp-p
Note that the crosstalk was halved at the lower frequencies. This proves that the audio is being shunted by the cathode capacitor at those frequencies.
Notice the fact that the higher frequencies haven't changed. I suspect that those crosstalk responses are more from the power supply, or even proximity of the audio transformers to each other and to the tubes, than anything else.
Of course, since bass frequencies are omnidirectional as everyone knows, it doesn't really matter.
A 15 volt to 0.5 volt difference is pretty large. I calculated about 39dB (using the 20LogA. 15/0.5 being the voltages used) . Most phono cartridges can not do better than 24dB, the best I have seen at about 29dB, that at 1kHz, dropping to low levels at both ends of the spectrum.
I took pictures of my scope of both responses, with 47 and 94µF capacitance. I will put it on my web site soon.
Gabe
OK all,
Here are the results of my test: the amp is a 300b SE amp using a common DC power supply with both filaments in parallel, with a 500 ohm pot connecting the ends, and a 360 ohm common cathode resistor bypassed by a 47µF cap (note, not 470µF as I recommend in the 2A3). Both channels have a non-inductive 8 ohm load. The right channel is driven to full output just before clipping. This is measured at the output.
right channel
20 Hz 15Vp-p
200Hz "
2kHz "
20kHz "
left channel
20 Hz 5Vp-p
200Hz 1Vp-p
2kHz 0.5Vp-p
20kHz 0.5vp-p
So as expected, lower frequencies had more crossover... but WAIT! I put another 47µF cap across the first one. The results?
Right Channel
20 Hz 15Vp-p
200Hz "
2kHz "
20kHz "
Left Channel
20 Hz 2Vp-p
200Hz 0.5Vp-p
2kHz 0.5Vp-p
20kHz 0.5Vp-p
Note that the crosstalk was halved at the lower frequencies. This proves that the audio is being shunted by the cathode capacitor at those frequencies.
Notice the fact that the higher frequencies haven't changed. I suspect that those crosstalk responses are more from the power supply, or even proximity of the audio transformers to each other and to the tubes, than anything else.
Of course, since bass frequencies are omnidirectional as everyone knows, it doesn't really matter.
A 15 volt to 0.5 volt difference is pretty large. I calculated about 39dB (using the 20LogA. 15/0.5 being the voltages used) . Most phono cartridges can not do better than 24dB, the best I have seen at about 29dB, that at 1kHz, dropping to low levels at both ends of the spectrum.
I took pictures of my scope of both responses, with 47 and 94µF capacitance. I will put it on my web site soon.
Gabe
Re: The Stereo SE...
It's negligable, and likely to be the same as any crosstalk introduced by both channels sharing the same chassis. This simply isn't an issue with a 470MF bypass cap.
Tubedude and Frank - I wonder what you would say about my DHT SE amps where the cathodes of ALL the tubes are directly grounded! Including the preamp tubes. Surely they are "only seperated by the filament resistance"?
Tube_Dude said:
It's negligable, and likely to be the same as any crosstalk introduced by both channels sharing the same chassis. This simply isn't an issue with a 470MF bypass cap.
Tubedude and Frank - I wonder what you would say about my DHT SE amps where the cathodes of ALL the tubes are directly grounded! Including the preamp tubes. Surely they are "only seperated by the filament resistance"?
SHARED CATHODES.
Hi,
That anyone would do that on a monoblock I can still understand,
what I also understand is that Gabe would defend this on a commercial basis.
This is something I would never do for my own use though, guess we just have different understandings of what the better audio is about.
Cheers,
Hi,
That anyone would do that on a monoblock I can still understand,
what I also understand is that Gabe would defend this on a commercial basis.
This is something I would never do for my own use though, guess we just have different understandings of what the better audio is about.
Cheers,
fdegrove,
Commercially?????
I sell kits more for the sharing than profit. In fact, when it boils down to it with all the things I give away with my kits including the support after, I LOSE money. So of what benefit is it to me to defend the rantings and ravings of opoposers especially in light of cold hard technical facts?
So, do you say that military engineers of the 30's and 40's were skimping and looking for commercial value in designing circuits known as reflex circuits, passing many different signals through one compnent to cut down on the size of an electronic device they used?
I do this for the love of the craft. I share freely my experience and expertise for the benefit of all. Otherwise I would have patented and made thousands, if not millions, off of my solid state tube design, instead of freely offering it to the world on my web site! And I would charge $300 more for my kits each. After all, from what I have seen they are better constructed than some of my competition charging more, or as well constructed as those charging double. And if you have bothered to read my customer comments, better sounding, too, with NO stereo compromise.
How dare you! (not meant with as much force as it sounds)
I know, I know... who cares. At least I do, and one other who perouses this site that I know of.
Yup, a fanatic! Just like the main page of this marvellous forum says "By Fanatics for Fanatics".
Gabe
Commercially?????
I sell kits more for the sharing than profit. In fact, when it boils down to it with all the things I give away with my kits including the support after, I LOSE money. So of what benefit is it to me to defend the rantings and ravings of opoposers especially in light of cold hard technical facts?
So, do you say that military engineers of the 30's and 40's were skimping and looking for commercial value in designing circuits known as reflex circuits, passing many different signals through one compnent to cut down on the size of an electronic device they used?
I do this for the love of the craft. I share freely my experience and expertise for the benefit of all. Otherwise I would have patented and made thousands, if not millions, off of my solid state tube design, instead of freely offering it to the world on my web site! And I would charge $300 more for my kits each. After all, from what I have seen they are better constructed than some of my competition charging more, or as well constructed as those charging double. And if you have bothered to read my customer comments, better sounding, too, with NO stereo compromise.
How dare you! (not meant with as much force as it sounds)
I know, I know... who cares. At least I do, and one other who perouses this site that I know of.
Yup, a fanatic! Just like the main page of this marvellous forum says "By Fanatics for Fanatics".
Gabe
Talk about things that are not related!!!!!
Taken WAY out of context, too, since I did say things grew less with more capacitance, and that the one I have on my page for the 2A3 has a cap 10 times bigger! Or did you simply ignore those measurements???
With 470µF guess what? Left channel will be 0.5 p-p, or the lowest it can go without going monoblock.
Tightness of bass has way much more to do with harmonics and damping factor than crosstalk.
Yikes! Please, if we are going to argue, lets argue intelligently and not taking things out of context or ignoring facts. Please?
Of course it is easy to criticize things that haven't been experienced.
Gabe
Taken WAY out of context, too, since I did say things grew less with more capacitance, and that the one I have on my page for the 2A3 has a cap 10 times bigger! Or did you simply ignore those measurements???
With 470µF guess what? Left channel will be 0.5 p-p, or the lowest it can go without going monoblock.
Tightness of bass has way much more to do with harmonics and damping factor than crosstalk.
Yikes! Please, if we are going to argue, lets argue intelligently and not taking things out of context or ignoring facts. Please?
Of course it is easy to criticize things that haven't been experienced.
Gabe
Shared cathode resistors...
I guive up...i am not inteligent enough to argue intelligently with you...I let the jugement about this to the readers of the thread...
Thats is true!!...I will never try it!
PS.Funny...i remenber someone say that the reason for this is only the budget...may be i'm wrong!!
I guive up...i am not inteligent enough to argue intelligently with you...I let the jugement about this to the readers of the thread...
Thats is true!!...I will never try it!
PS.Funny...i remenber someone say that the reason for this is only the budget...may be i'm wrong!!
Stereo.
Hi,
I do, so do other people around here Gabe.
My comment was more directed at Joel than it was at you and after all you do run a business? So the term "commercial" is not really out of place I assume.
Let me make it clear that I have nothing but admiration for you, your website and the goals you set for yourself.
I realise all too well that this is a tricky and very difficult field to work in, after all I've been there too although not exactly in the same way as yourself.
Nonetheless, I also hope your big enough a sport to understand that not everybody has to support the idea.
Cheers,
Hi,
I do, so do other people around here Gabe.
My comment was more directed at Joel than it was at you and after all you do run a business? So the term "commercial" is not really out of place I assume.
Let me make it clear that I have nothing but admiration for you, your website and the goals you set for yourself.
I realise all too well that this is a tricky and very difficult field to work in, after all I've been there too although not exactly in the same way as yourself.
Nonetheless, I also hope your big enough a sport to understand that not everybody has to support the idea.
Cheers,
Tube Dude,
It is your loss.
fdegrove,
It is a "business" only inasmuch as I have a product and sell it to others. I do not stake my livlihood in it nor am even registered as a true business. It is more like "Hey Gabe, would you buy the parts for me and put together a schematic and some instructions so I can build it, and add a couple of bucks for yourself" situation.
I am not asking anyone to support anything, just try it out. But when questions to the functionality or quality are brought up, I feel compelled to reply and show evidence to the contrary.
No one even mentioned that at full power the output was the same from 20 to 20kHz, slight variations within the spectrum notwithstanding, though important. I did not adjust the input amplitude once I set it, either. Yes, the bandwidth is very wide and relatively flat. But I attribute that a bit more to the venerable 300B, and to using the cathode follower, and not to that much that I did. I am sure that you and other realize that all of it is, including the single cathode for both channels idea, 40 years old and older.
When you see the pictures (except for the 20Hz. Camera is too fast to show a full trace) you will be probably as amazed as I was at the symmetry of the wave. Very clean and low distortion again at full power. Isn't that what hi-fi is about?
While I thank you for it, I am not fishing for compliments or admiration. Nor would I appreciate it if it was condescending or patronizing. I don't think so, not from you.
But I would like for us all to get along better and see more eye to eye, since... and I am guessing here... electronics is the same all over the earth... no?
Smile!
Gabe
It is your loss.
fdegrove,
It is a "business" only inasmuch as I have a product and sell it to others. I do not stake my livlihood in it nor am even registered as a true business. It is more like "Hey Gabe, would you buy the parts for me and put together a schematic and some instructions so I can build it, and add a couple of bucks for yourself" situation.
I am not asking anyone to support anything, just try it out. But when questions to the functionality or quality are brought up, I feel compelled to reply and show evidence to the contrary.
No one even mentioned that at full power the output was the same from 20 to 20kHz, slight variations within the spectrum notwithstanding, though important. I did not adjust the input amplitude once I set it, either. Yes, the bandwidth is very wide and relatively flat. But I attribute that a bit more to the venerable 300B, and to using the cathode follower, and not to that much that I did. I am sure that you and other realize that all of it is, including the single cathode for both channels idea, 40 years old and older.
When you see the pictures (except for the 20Hz. Camera is too fast to show a full trace) you will be probably as amazed as I was at the symmetry of the wave. Very clean and low distortion again at full power. Isn't that what hi-fi is about?
While I thank you for it, I am not fishing for compliments or admiration. Nor would I appreciate it if it was condescending or patronizing. I don't think so, not from you.
But I would like for us all to get along better and see more eye to eye, since... and I am guessing here... electronics is the same all over the earth... no?
Smile!
Gabe
Re: SHARED CATHODES.
Frank,
I swear. In this thread at least, the only feeling I get from you is that you are out to make arguments.
I personally see no need for your >50dB demand of stereo seperation, since it's all going through the air anyway. Cover your right ear, mute the left channel...hear that? My God, it's audible!!!!!
Tim
fdegrove said:Hi,
That anyone would do that on a monoblock I can still understand,
what I also understand is that Gabe would defend this on a commercial basis.
This is something I would never do for my own use though, guess we just have different understandings of what the better audio is about.
Cheers,
Frank,
I swear. In this thread at least, the only feeling I get from you is that you are out to make arguments.
I personally see no need for your >50dB demand of stereo seperation, since it's all going through the air anyway. Cover your right ear, mute the left channel...hear that? My God, it's audible!!!!!
Tim
Curiosity
Gabe:
Just for my own curiosity, and not to fan any flame's or kick it back to rehashing any one else's stubborness, could the center tap in the 5 volt winding be used to create two 2.5 volt filament supplies for the 2 2A3's? I don't have an issue with crosstalk with your Maggie circuit and I'm sure I won't have one with this either, I'm just curious as to why this wasn't mentioned and obviously, why it wouldn't work. It could save me some heart ache down the road to know.
The 6L6 amp I'm working on has fixed cathode bias for each channel and I'm thinking of combining all the two output pairs for both channels under one bias resistor to get the same surrounding effect as the Maggie. Any drawbacks here? The circuit can be seen at the Tube cad site. http://www.tubecad.com/Classic_Articles/index.html
Gabe:
Just for my own curiosity, and not to fan any flame's or kick it back to rehashing any one else's stubborness, could the center tap in the 5 volt winding be used to create two 2.5 volt filament supplies for the 2 2A3's? I don't have an issue with crosstalk with your Maggie circuit and I'm sure I won't have one with this either, I'm just curious as to why this wasn't mentioned and obviously, why it wouldn't work. It could save me some heart ache down the road to know.
The 6L6 amp I'm working on has fixed cathode bias for each channel and I'm thinking of combining all the two output pairs for both channels under one bias resistor to get the same surrounding effect as the Maggie. Any drawbacks here? The circuit can be seen at the Tube cad site. http://www.tubecad.com/Classic_Articles/index.html
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