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#1
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
I bought an Eico 2080 Integrated Amplifier on eBay. It is very similar to the Eico ST-70. I'm not a big fan of tone controls. I also wanted to try a really cool remote volume control kit designed & sold by Mikkel Simonsen (unfortunately, he doesn't hang around R.A.T. these days). Mikkel's kit includes a time-delayed mute and power-on (e.g. B+) function on a small PCB that runs off of the filament supply. Best thing about it is that I can turn my amp on and off across the room from my lazy ass using the remote (e.g. when the phone rings). I removed the PECs and other tone control stuff from the Eico. I fashioned a rack-mountable faceplate, painted with lettering. I didn't use the ALPs control from Mikkel's kit (it was a bit big for this app) but instead removed a 50K pot from a broken SS amplifier. My design goals: 1) Present a reasonable impedance (200K) to the phono output and other inputs; 2) Isolate the balance from the volume as best as possible; 3) Provide a buffered output for Tape or Line out 4) Mute the circuit on command by forcing the input to the main amplifier stage to ground; do it in such a way as to avoid a click when changing states. The original tone circuit used the 2nd stage (12AU7 like) of a 7247 / 12DW7 in a CF configuration. I wanted to sub a 6CG7 for improved linearity. The original 7247 CF was set to idle at 4 ma. I kept the same component values for the 6CG7, although its specs are a little different. Before I implement it, I had a few questions: A) Is a 200K balance pot too low a value? B) Any problems with the position of the mute switch in the circuit? C) Any problem with the tap-off point for the Tape Out? D) Any other apparent problems? Thanks to anyone who cares to respond with advice. Jon |
#2
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
Jon Yaeger wrote: I bought an Eico 2080 Integrated Amplifier on eBay. It is very similar to the Eico ST-70. I'm not a big fan of tone controls. I also wanted to try a really cool remote volume control kit designed & sold by Mikkel Simonsen (unfortunately, he doesn't hang around R.A.T. these days). Mikkel's kit includes a time-delayed mute and power-on (e.g. B+) function on a small PCB that runs off of the filament supply. Best thing about it is that I can turn my amp on and off across the room from my lazy ass using the remote (e.g. when the phone rings). I removed the PECs and other tone control stuff from the Eico. I fashioned a rack-mountable faceplate, painted with lettering. How many old tube amps do you bugger in any given calendar year? And are people gullible enough to pay more than scrap price when you are done, or do you just have a pile of them building up in your garage?? |
#3
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
Bret Ludwig wrote:
Jon Yaeger wrote: I bought an Eico 2080 Integrated Amplifier on eBay. It is very similar to the Eico ST-70. I'm not a big fan of tone controls. I also wanted to try a really cool remote volume control kit designed & sold by Mikkel Simonsen (unfortunately, he doesn't hang around R.A.T. these days). Mikkel's kit includes a time-delayed mute and power-on (e.g. B+) function on a small PCB that runs off of the filament supply. Best thing about it is that I can turn my amp on and off across the room from my lazy ass using the remote (e.g. when the phone rings). I removed the PECs and other tone control stuff from the Eico. I fashioned a rack-mountable faceplate, painted with lettering. How many old tube amps do you bugger in any given calendar year? And are people gullible enough to pay more than scrap price when you are done, or do you just have a pile of them building up in your garage?? And how many times have you fell on your ass since you were a kid? Sounds like you are good at it still. Bret, what a wuss you are!!!!!!! Yeh, Its John Stewart |
#4
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
.... and in this corner ...
"Bret Ludwig" wrote in message oups.com... Jon Yaeger wrote: I bought an Eico 2080 Integrated Amplifier on eBay. It is very similar to the Eico ST-70. I'm not a big fan of tone controls. I also wanted to try a really cool remote volume control kit designed & sold by Mikkel Simonsen (unfortunately, he doesn't hang around R.A.T. these days). Mikkel's kit includes a time-delayed mute and power-on (e.g. B+) function on a small PCB that runs off of the filament supply. Best thing about it is that I can turn my amp on and off across the room from my lazy ass using the remote (e.g. when the phone rings). I removed the PECs and other tone control stuff from the Eico. I fashioned a rack-mountable faceplate, painted with lettering. How many old tube amps do you bugger in any given calendar year? And are people gullible enough to pay more than scrap price when you are done, or do you just have a pile of them building up in your garage?? |
#6
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
How many old tube amps do you bugger in any given calendar year? And
are people gullible enough to pay more than scrap price when you are done, or do you just have a pile of them building up in your garage?? Those who know, do. Those who do not know, carp. Bret, you get closer and closer to joining the "big three idiots" here with these sorts of posts. Comes to it, Phil, Andre and you would have one helluva circle-jerk, and maybe would leave the rest of us alone. I noted with some interest your post in RAR+P about a crystal detector set (alone) capable of driving certain Klipsch speakers. That is not a difficult trick to duplicate, depending on the diode you use for the purpose. Some of the Galenium-Arsenide crystal & tickler devices you can get even today will put out enough power through an appropriate transformer to run a speaker if, as you say, you are close to a 50,000+ source. But what you will discover is that the audio bandwidth is about 2Hz, perhaps less. Enough for voice and a bit of instrument... maybe. I have a little crystal (POK-ETTE Radio) set with a built-in speaker (about 1") that does largely the same thing, but from a "modern" germanium diode, so the output power is far less. Everything you need to do this may be gotten he http://www.xtalman.com/ Start with the Philmore Detector if you haven't the talent to roll your own cat's whisker. It was the standard-of-the-industry back when. Now, if you really want to do something rare and unusual.... OOPS... it might take some actual work rather than carping on your part, try an FM _CRYSTAL_ radio: http://www.vmarsmanuals.co.uk/newsle...timeshobby.pdf Peter Wieck Wyncote, PA |
#7
Posted to rec.audio.tubes,rec.antiques.radio+phono
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crystal detector set, was ( Proposed Eico Tone Control Mod)
In article .com,
" wrote: Bret, you get closer and closer to joining the "big three idiots" here with these sorts of posts. Comes to it, Phil, Andre and you would have one helluva circle-jerk, and maybe would leave the rest of us alone. I noted with some interest your post in RAR+P about a crystal detector set (alone) capable of driving certain Klipsch speakers. That is not a difficult trick to duplicate, depending on the diode you use for the purpose. Some of the Galenium-Arsenide crystal & tickler devices you can get even today will put out enough power through an appropriate transformer to run a speaker if, as you say, you are close to a 50,000+ source. But what you will discover is that the audio bandwidth is about 2Hz, perhaps less. Enough for voice and a bit of instrument... maybe. Why would the audio bandwidth be restricted to "2Hz"? I am assuming you meant 2 kHz, not "2 Hz". The audio bandwidth can be anything you want, it depends only on the loaded Q of the tuned circuits, which is not the same thing as the coil Q. The J.W.Miller set mentioned in the original post has a wide audio bandwidth. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
#8
Posted to rec.audio.tubes,rec.antiques.radio+phono
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crystal detector set, was ( Proposed Eico Tone Control Mod)
"John Byrns" wrote in message ... In article .com, " wrote: for voice and a bit of instrument... maybe. Why would the audio bandwidth be restricted to "2Hz"? I am assuming you meant 2 kHz, not "2 Hz". The audio bandwidth can be anything you want, it depends only on the loaded Q of the tuned circuits, which is not the same thing as the coil Q. The J.W.Miller set mentioned in the original post has a wide audio bandwidth. Regards, John Byrns Loaded Q, and the frequency... (Arithmetic selectivity..) Pete |
#9
Posted to rec.audio.tubes,rec.antiques.radio+phono
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crystal detector set, was ( Proposed Eico Tone Control Mod)
Why would the audio bandwidth be restricted to "2Hz"
Sorry, miswrote. But to get the kind of power to drive a speaker per the description, the audio bandwidth gets restricted to about 2KHz... my mistake. At least in my *direct* experience. Peter Wieck Wyncote, PA |
#10
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
Jon Yaeger wrote:
I bought an Eico 2080 Integrated Amplifier on eBay. It is very similar to the Eico ST-70. I removed the PECs and other tone control stuff from the Eico. What is a PEC? thanks... |
#11
Posted to rec.audio.tubes
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Proposed Eico Tone Control Mod
in article ,
at wrote on 12/27/05 5:18 PM: Jon Yaeger wrote: I bought an Eico 2080 Integrated Amplifier on eBay. It is very similar to the Eico ST-70. I removed the PECs and other tone control stuff from the Eico. What is a PEC? thanks... Printed Electronic Circuit - a precursor to modern ICs. Tended to drift all over the place . . . |
#12
Posted to rec.audio.tubes,rec.antiques.radio+phono
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crystal detector set, was ( Proposed Eico Tone Control Mod)
In article .com,
" wrote: Why would the audio bandwidth be restricted to "2Hz" Sorry, miswrote. But to get the kind of power to drive a speaker per the description, the audio bandwidth gets restricted to about 2KHz... my mistake. At least in my *direct* experience. This doesn't make much sense, to get the kind of power required to drive a speaker requires proper impedance matching, but the bandwidth is independent of proper matching. Can you explain why proper matching should require unusually narrow bandwidth? There is one reason I can envision, which is a narrow band antenna system, which I suppose the typical short wire antenna would qualify as. Regards, John Byrns Surf my web pages at, http://users.rcn.com/jbyrns/ |
#13
Posted to rec.audio.tubes,rec.antiques.radio+phono
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crystal detector set, was ( Proposed Eico Tone Control Mod)
but the bandwidth is
independent of proper matching. Can you explain why proper matching should require unusually narrow bandwidth? There is one reason I can envision, which is a narrow band antenna system, which I suppose the typical short wire antenna would qualify as. John: If you want an explanation in the engineering sense, I am not an engineer... but let's see if this does the trick. A priori, I wish to state that I am relating my direct experience with a crystal detector driving a standard 4-ohm nominal relatively efficient audio speaker. NOTE: I did not say "high fidelity". The speaker was a so-called 'full-range' concentric speaker designed for use in cars. The basic explanation is that if the entire bandwidth is concentrated into a very narrow range... without clamping the edges, more powers is concentrated into the 'sweet spot'. Kinda like concentrating a given flow of liquid into a narrow channel. If one needs to pass so many gallons-per-minute, and the channel gets narrow, the speed of the flow gets faster. (I do like plumbing analogies given the Brit "VALVE" designation). When the phenomenon was demonstrated to me, the choice was a specific output transformer that -somehow- did exactly that. It was fed via an R/C arrangement that the demonstrator could vary... as the signal became more 'full range' the volume dropped... like a stone. On the other hand, the antenna in question was about 50' of wire strung over the pavilion joists (Kutztown Radio Swap some years ago), and nothing otherwise special. I am not trying to be evasive, but at the same time, I am reporting my direct observations of a home-brew crystal set without any external amplification driving a single speaker at a volume sufficient to be heard in the setting. Peter Wieck Wyncote, PA |
#14
Posted to rec.audio.tubes
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crystal detector set, was ( Proposed Eico Tone Control Mod)
On 27 Dec 2005 17:18:31 -0800, " wrote:
When the phenomenon was demonstrated to me, the choice was a specific output transformer that -somehow- did exactly that. It was fed via an R/C arrangement that the demonstrator could vary... as the signal became more 'full range' the volume dropped... like a stone. On the other hand, the antenna in question was about 50' of wire strung over the pavilion joists (Kutztown Radio Swap some years ago), and nothing otherwise special. I am not trying to be evasive, but at the same time, I am reporting my direct observations of a home-brew crystal set without any external amplification driving a single speaker at a volume sufficient to be heard in the setting. Let me suggest that the quantity y'all are discussing is the classic "Q", and in its primeval state. The name "Q', currently meaning the ratio of reactive to resistive impedance, originated in this very topic. It originally was very hard to come by, and the trade-off's you've observed were an everyday issue for radio reception. ps: the "Q" was originally short for "quality factor". Sorry; historical sidelight; now back to your regularly scheduled station, Chris Hornbeck |
#15
Posted to rec.audio.tubes,rec.antiques.radio+phono
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crystal detector set, was ( Proposed Eico Tone Control Mod)
On Tue, 27 Dec 2005 17:18:31 -0800, wrote:
but the bandwidth is independent of proper matching. Can you explain why proper matching should require unusually narrow bandwidth? There is one reason I can envision, which is a narrow band antenna system, which I suppose the typical short wire antenna would qualify as. John: If you want an explanation in the engineering sense, I am not an engineer... but let's see if this does the trick. A priori, I wish to state that I am relating my direct experience with a crystal detector driving a standard 4-ohm nominal relatively efficient audio speaker. NOTE: I did not say "high fidelity". The speaker was a so-called 'full-range' concentric speaker designed for use in cars. The basic explanation is that if the entire bandwidth is concentrated into a very narrow range... without clamping the edges, more powers is concentrated into the 'sweet spot'. Kinda like concentrating a given flow of liquid into a narrow channel. If one needs to pass so many gallons-per-minute, and the channel gets narrow, the speed of the flow gets faster. (I do like plumbing analogies given the Brit "VALVE" designation). When the phenomenon was demonstrated to me, the choice was a specific output transformer that -somehow- did exactly that. It was fed via an R/C arrangement that the demonstrator could vary... as the signal became more 'full range' the volume dropped... like a stone. On the other hand, the antenna in question was about 50' of wire strung over the pavilion joists (Kutztown Radio Swap some years ago), and nothing otherwise special. I am not trying to be evasive, but at the same time, I am reporting my direct observations of a home-brew crystal set without any external amplification driving a single speaker at a volume sufficient to be heard in the setting. Peter Wieck Wyncote, PA You need to know what the "R/C arrangement" was doing. Resistors dissipate power and you certainly don't want any of them around when you are trying something like this. You should even consider the resistance of the output transformer. As far as your water pipe analogy, if the station you wanted to listen to was broadcasting white noise it might have some validity. However, most people prefer music or speech, both of which have very little energy above a few KHz. That is why records and FM radio use pre-emphasis; it boosts the highs before transmission so they don't get lost in noise. At the receiving end, they are cut back down to size reducing the noise at the same time. The Q of the tuned circuit used in the receiver has a direct effect on bandwidth as well as efficiency. High Q gives narrower bandwidth and higher efficiency (for the circuit by itself). Coupling a load to the circuit reduces the Q no matter how good the circuit itself is. That is why old receivers used "loose couplers"; the lower loading increased the selectivity. Simultaneously, it also reduced the loudness of the signal received; they were adjustable so the operator could reach some sort of compromise. Since most crystal sets (even using headphones) have trouble receiving less than half the broadcast band at once, I sincerely doubt that they could get a high enough Q to limit the bandwidth to anything like 2KHz, especially while driving a speaker. -- Jim Mueller To get my real email address, replace wrongname with eportiz. Then replace nospam with sacbeemail. |
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