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#1
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"Un-Choking " a Fender Princeton
I'm trying to understand something that Gerald Weber said in the
October '05 issue of Vintage Guitar in response to someone's question as to the function of the choke in a power supply pi filter. He said,"... A choke resists changes in current, so to some degree, it suppresses the output-stage dynamics. ..." The Fender Princeton 5E2 is a single ended circuit. It seems to me that any changing current through the tube will result in a changing voltage at the primary of the output transformer and hence across it to the secondary and on the load if the pwer supply fed an ideal constant current into the primary of the output transformer. I don't understand how it "suppresses the output-stage dynamics." Best regards, Joe |
#2
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Sorry for the typo. The the last part of the next to last sentence
should read: .... and on the load even if the power supply fed an ideal constant current into the primary of the output transformer. |
#3
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Joseph Meditz wrote:
I'm trying to understand something that Gerald Weber said in the October '05 issue of Vintage Guitar in response to someone's question as to the function of the choke in a power supply pi filter. He said,"... A choke resists changes in current, so to some degree, it suppresses the output-stage dynamics. ..." The Fender Princeton 5E2 is a single ended circuit. It seems to me that any changing current through the tube will result in a changing voltage at the primary of the output transformer and hence across it to the secondary and on the load if the pwer supply fed an ideal constant current into the primary of the output transformer. I don't understand how it "suppresses the output-stage dynamics." Best regards, Joe Removing the choke from the power supply of a Fender 5E2 will result in lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Here are a couple of very good references. http://www.thetubestore.com/earfenam.html Written by Eric Barbour http://www.harmony-central.com/Guita...inceton-1.html Cheers, John Stewart |
#4
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I don't know the Fender power supply circuit offhand. But if it has a
choke-input supply, removing the choke would cause a drastic rise in the B+ voltage. This could do many Bad Things - blown caps, melted tubes (depending on the operating point they end up at with a different plate voltage). Don't do it unless you know what you are doing. Just in case, please be aware that the voltages inside even a small tube amp are more than adequate to kill you. It can be extremely dangerous even when the amp is off and unplugged. "John Stewart" wrote in message ... Joseph Meditz wrote: I'm trying to understand something that Gerald Weber said in the October '05 issue of Vintage Guitar in response to someone's question as to the function of the choke in a power supply pi filter. He said,"... A choke resists changes in current, so to some degree, it suppresses the output-stage dynamics. ..." The Fender Princeton 5E2 is a single ended circuit. It seems to me that any changing current through the tube will result in a changing voltage at the primary of the output transformer and hence across it to the secondary and on the load if the pwer supply fed an ideal constant current into the primary of the output transformer. I don't understand how it "suppresses the output-stage dynamics." Best regards, Joe Removing the choke from the power supply of a Fender 5E2 will result in lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Here are a couple of very good references. http://www.thetubestore.com/earfenam.html Written by Eric Barbour http://www.harmony-central.com/Guita...inceton-1.html Cheers, John Stewart |
#5
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John Stewart wrote: Joseph Meditz wrote: I'm trying to understand something that Gerald Weber said in the October '05 issue of Vintage Guitar in response to someone's question as to the function of the choke in a power supply pi filter. He said,"... A choke resists changes in current, so to some degree, it suppresses the output-stage dynamics. ..." The Fender Princeton 5E2 is a single ended circuit. It seems to me that any changing current through the tube will result in a changing voltage at the primary of the output transformer and hence across it to the secondary and on the load if the pwer supply fed an ideal constant current into the primary of the output transformer. I don't understand how it "suppresses the output-stage dynamics." Best regards, Joe Removing the choke from the power supply of a Fender 5E2 will result in lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Weber is an idiot. He also recommends piling tons of capacitance onto rectifier tubes. LV |
#6
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Removing the choke from the power supply of a Fender 5E2 will result in
lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Gerald Weber did not say to remove the choke. What he said was that the amp would sound better if you fed the screen from the output of the pi section but fed the plate from the _input_ to the pi filter. Increased ripple aside, his point was that this would give better dynamic response. Joe |
#7
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Joseph Meditz wrote:
Removing the choke from the power supply of a Fender 5E2 will result in lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Gerald Weber did not say to remove the choke. What he said was that the amp would sound better if you fed the screen from the output of the pi section but fed the plate from the _input_ to the pi filter. Increased ripple aside, his point was that this would give better dynamic response. Joe That is an easy mod to try, anyway. In order to cut down the PS ripple you could safely increase the incoming cap to 40 microfarad, the max spec'd for the 5Y3 rectifier. There is negative feedback already in the circuit, so that will minimize any residual hum. I've built quite a few SE amps this way with good results. That includes those with a 6V6 output. BTW, you can read about my latest effort in the hifi amp realm in the September issue of AudioXpress magazine. PP 6V6's. Very low distortion. And very low cost to build at less than 200.00 USD. Take your pick of several versions. The amp is shown both cathode & fixed bias while the PS is shown as traditional & regulated. All with lots of measurement data while running in various modes. The circuit used may surprise some here. Good luck with your amp. John Stewart |
#8
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John Stewart wrote:
Joseph Meditz wrote: Removing the choke from the power supply of a Fender 5E2 will result in lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Gerald Weber did not say to remove the choke. What he said was that the amp would sound better if you fed the screen from the output of the pi section but fed the plate from the _input_ to the pi filter. Increased ripple aside, his point was that this would give better dynamic response. Joe That is an easy mod to try, anyway. In order to cut down the PS ripple you could safely increase the incoming cap to 40 microfarad, the max spec'd for the 5Y3 rectifier. There is negative feedback already in the circuit, so that will minimize any residual hum. I've built quite a few SE amps this way with good results. That includes those with a 6V6 output. BTW, you can read about my latest effort in the hifi amp realm in the September issue of AudioXpress magazine. PP 6V6's. Very low distortion. And very low cost to build at less than 200.00 USD. Take your pick of several versions. The amp is shown both cathode & fixed bias while the PS is shown as traditional & regulated. All with lots of measurement data while running in various modes. The circuit used may surprise some here. Good luck with your amp. John Stewart I should have mentioned the fixed bias version of the new amp manages just under 15 watts at clipping. JLS |
#10
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Joseph Meditz wrote:
Removing the choke from the power supply of a Fender 5E2 will result in lots of hum at the output. Not recommended at all. Without seeing the rest of the article you have referenced it is difficult to figure out what the author had in mind. Gerald Weber did not say to remove the choke. What he said was that the amp would sound better if you fed the screen from the output of the pi section but fed the plate from the _input_ to the pi filter. Increased ripple aside, his point was that this would give better dynamic response. Joe That is an easy mod to try, anyway. In order to cut down the PS ripple you could safely increase the incoming cap to 40 microfarad, the max spec'd for the 5Y3 rectifier. There is negative feedback already in the circuit, so that will minimize any residual hum. I've built quite a few SE amps this way with good results. That includes those with a 6V6 output. Hi John, Ripple is not the issue here. The question is whether doing this will improve dynamic response. Can you think of any reason why it should? BTW, you can read about my latest effort in the hifi amp realm in the September issue of AudioXpress magazine. PP 6V6's. Very low distortion. And very low cost to build at less than 200.00 USD. Take your pick of several versions. The amp is shown both cathode & fixed bias while the PS is shown as traditional & regulated. All with lots of measurement data while running in various modes. The circuit used may surprise some here. OK. I rarely read Audio Express but will pick up a copy for your article. But I used to subscribe to Glass Audio before I ever messed with a tube CKT but did not renew when they became Audio Express which, IMO, is very poor substitute for Glass Audio. Joe |
#11
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Joseph Meditz wrote: Hi John, Ripple is not the issue here. The question is whether doing this will improve dynamic response. Can you think of any reason why it should? Sound to all of us is a very subjective thing. So I guess it depends a lot on who you would ask in each case. The result will depend as much on the speaker in its box & the listening area as it does on the amplifier! Best to try the circuit changes which are fairly simple to make & then decide for yourself. Instrument amplifiers really are in a different world than one would expect for hifi. A guitar amp is really a big part of the overall affect you are trying to attain. If you were to look at the response of the amp to a step function before & after the mods I doubt you would see any improvement. OK. I rarely read Audio Express but will pick up a copy for your article. But I used to subscribe to Glass Audio before I ever messed with a tube CKT but did not renew when they became Audio Express which, IMO, is very poor substitute for Glass Audio. Joe It seems that the printed page is under attack, I think by the internet. I've been a subscriber to Playboy more than 40 years, Scientific American about 30 years & they are both much smaller than they once were. In my opinion Glass Audio was a better magazine for anyone into tubes but the publisher has to do whatever is necessary to stay in business! There are still quite a few interesting articles published in AudioXpress covering vacuum tube circuits. Cheers, John Stewart |
#12
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Joseph Meditz wrote: I'm trying to understand something that Gerald Weber said in the October '05 issue of Vintage Guitar in response to someone's question as to the function of the choke in a power supply pi filter. He said,"... A choke resists changes in current, so to some degree, it suppresses the output-stage dynamics. ..." The purpose of the choke is to filter the hum from the PS that would occur if there was no choke in a CLC pi filter. This sort of filter in the old days consisted typically of 16uF, 5H, 16uF. Your circuit is a single ended class A1 circuit, and unless the output is clipping due to gross over drive, there is no suppression of the dynamics in the output stage at all due to the choke because the SE tube draws a constant current right up to clipping, apart from a small variation due to the second harmonic distortion of the tube. Leave the choke right where it is unless you want to upgrade the PS. In this case the only thing that you can do is replace the C2 with say 100 uF/450V but leave the C1 and choke in the circuit as is. C1 should not be raised in value lest you cause the rectifier 5Y3 to become overloaded by the peak charging currents which will cause it to die. The Fender Princeton 5E2 is a single ended circuit. It seems to me that any changing current through the tube will result in a changing voltage at the primary of the output transformer and hence across it to the secondary and on the load if the pwer supply fed an ideal constant current into the primary of the output transformer. I don't understand how it "suppresses the output-stage dynamics." As far as the tube plus OPT and the load it has is concerned, the C2 of the CLC filter acts as a low impedance at signal F. If the dynamic Ra of 6V6 is 40kohms, and load = 8k, then total dynamic load = say 48k. If C2 = 16 uF, then its impedance = 100 ohms at 100Hz, and such an impedance is low compared to the load connected to it. So if there is 4 watts of power in the 8k load, the signal voltage at the 6V6 anode is 178vrms, and I = 0.022A, so the voltage at the C2 due to signal at 100Hz = 0.022 x 100 ohms = 2.25Vrms, which is tiny compared to the signal voltage across the OPT. At 1kHz, signal at the 16 uF = 0.22 Vrms at 4 watts. There is no mechanism at work to cause compression or limiting other than the natural voltage excursion limits. If the anode signal voltage was 178Vrms, then this = 251Vpeak, and the Ea would have to be around +300V to allow this much voltage swing. Beyond a swing of around 180vrms, the 6V6 will begin to clip. In a class AB PP amp, the Ea of the tubes will reduce at full power from the idle value and so some reduction of the possible Vswing at the anode occurs. Patrick Turner. Best regards, Joe |
#13
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** The Turneroid Autistic ****wit has gone into melt down. Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. .......... Phil |
#14
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Forget the meds today, Phil?
"Phil Allison" wrote in message ... ** The Turneroid Autistic ****wit has gone into melt down. Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. ......... Phil |
#15
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"John Willoughby" ** FYI: Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. .......... Phil |
#16
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On Tue, 30 Aug 2005 01:05:42 +1000, "Phil Allison"
wrote: ** The Turneroid Autistic ****wit has gone into melt down. Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. ......... Phil what started you off this time? |
#17
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bill ramsay wrote: On Tue, 30 Aug 2005 01:05:42 +1000, "Phil Allison" wrote: ** The Turneroid Autistic ****wit has gone into melt down. Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. ......... Phil what started you off this time? I doubt Phil could even begin to answer your question properly. I'll try to be brief. Phil appears to have suffered a mental breakdown. It seems to have occured as a result of my refusal to examine mosfet data with regard to a class A mosfet amp designed by a british female by the name of Sue Parker. ( A google search, 'Sue Parker zeus amplifier' will bring up the links to her informative site. ) I like this fine female. She has the courage to appear with a novel SS design in a world full of men including out Phil A who predictably has called this fine lady a long list of names which are all derogatory, and totally undeserved. It shows that our Phil is a raving mysogenist and nut case. I have posted quite a few posts at aus.hi-fi urging him to see a psychiatrist. His ability to reason has become quite dysfunctional. Over the past few months he has been quite reasonable imho, but suddenly he has plummeted over the edge. If anyone should take a look at the google archives of aus.hi-fi for the last week they will see all the evidence that Phil is quite mentally ill at this time. The crew at aus.hi-fi have wasted no time in abusing this otherwise intelligent and perceptive man when he isn't suffering his mental condition, and several Phil Allison imposters have sprung up to ensure he looks a complete fool and blithering idiot. Patrick Turner. |
#18
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"Patrick Turner" ** FYI: Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. .......... Phil |
#19
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"Patrick Turner" wrote in message ... bill ramsay wrote: On Tue, 30 Aug 2005 01:05:42 +1000, "Phil Allison" wrote: ** The Turneroid Autistic ****wit has gone into melt down. Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. ......... Phil what started you off this time? I doubt Phil could even begin to answer your question properly. I'll try to be brief. Phil appears to have suffered a mental breakdown. It seems to have occured as a result of my refusal to examine mosfet data with regard to a class A mosfet amp designed by a british female by the name of Sue Parker. ( A google search, 'Sue Parker zeus amplifier' will bring up the links to her informative site. ) I like this fine female. She has the courage to appear with a novel SS design in a world full of men including out Phil A who predictably has called this fine lady a long list of names which are all derogatory, and totally undeserved. It shows that our Phil is a raving mysogenist and nut case. I have posted quite a few posts at aus.hi-fi urging him to see a psychiatrist. His ability to reason has become quite dysfunctional. Over the past few months he has been quite reasonable imho, but suddenly he has plummeted over the edge. If anyone should take a look at the google archives of aus.hi-fi for the last week they will see all the evidence that Phil is quite mentally ill at this time. The crew at aus.hi-fi have wasted no time in abusing this otherwise intelligent and perceptive man when he isn't suffering his mental condition, and several Phil Allison imposters have sprung up to ensure he looks a complete fool and blithering idiot. Patrick Turner. For the benefit of those who don't frequent aus.hi-fi. Part of what Patrick says is true. Yes Phil is having a bit of an "episode" as of late, but let's put things into perspective. Most of the grief Phil gets he brings on himself. He has truly lost the plot in the past few days and one can only feel pity for the man. To illustrate just how off the rails he really is he can't even accept an accolade without thinking someone is trying to take the **** out of him. It's sad and rather pathetic really. I don't have a solution to his problem and as Patrick will most likely attest to, it pointless even trying to side with him. All you'll get is abuse hurled at you. Perhaps just not responding to anything he says for a while might get him to calm down to at least some sort of state of rationality. Cheers, Alan |
#20
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"Patrick Turner" ** The Turneroid Autistic ****wit has gone into melt down. Just like " Robby the Robot " the Turneroid Autistic ****wit goes completely haywire with arms waving about and sparks flying inside his mechanical brain when given a command that conflicts with his internal (in his case bizarre) program. What the Turneroid Autistic ****wit is ABSOLUTELY refusing to do is merely look at a data sheet OR do a five minute Google search OR even consider the simple matter of how to identify a common electronic part used in audio amplifiers. I could easily just post the answer but the Turneroid Autistic ****wit stubbornly and INSANELY refuses to ask - his pathetic ego, his bizarre paranoia and his extreme autism refuses to let him. Mr Turner - you are basically a pile of sub human ****. YOU are a mental retard and an autistic pig. I will continue rubbing your ugly nose in those undeniable facts. what started you off this time? I doubt Phil could even begin to answer your question properly. ** The Turneroid is in a state of stark autistic terror over *nothing*. I intend to keep him in that state for a while longer yet :-) . The Turneroid appears to have suffered a mental breakdown. It seems to have occured as a result of my request for him to examine basic mosfet data with regard to a class A mosfet amp design by a pommy woman. Pat is besotted with this dopey female. She has the stupidity to appear with a ridiculous SS design on her own site. Pat Turner is a raving misogynist and nut case - I have posted on aus.hi-fi saying he is beyond help from a psychiatrist. His ability to reason has become quite dysfunctional - even worse than usual. Over the past few months he has been quite reasonable imho, but suddenly he has plummeted over the edge into autistic terror at being presented with something he does not know and should know. If anyone should take a look at the google archives of aus.hi-fi for the last week they will see all the evidence that Pat is quite mentally ill at this time. ............... Phil |
#21
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Joseph Meditz wrote:
I'm trying to understand something that Gerald Weber said in the October '05 issue of Vintage Guitar in response to someone's question as to the function of the choke in a power supply pi filter. He said,"... A choke resists changes in current, so to some degree, it suppresses the output-stage dynamics. ..." ... Your circuit is a single ended class A1 circuit, and unless the output is clipping due to gross over drive, there is no suppression of the dynamics in the output stage at all due to the choke because the SE tube draws a constant current right up to clipping, apart from a small variation due to the second harmonic distortion of the tube. Hi Patrick, OK. You disagree with Gerald Weber's statement. Thanks, Joe |
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