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#41
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Lord Valve wrote: Despite what you may have seen from a couple of the know-it-alls on this NG, don't do it. Audiophools rarely stress their gear, and consequently rarely consider what may happen to it when it is operated beyond design parameters - as guitar amplifiers *routinely* are. You risk a condition known as high- tension flyback if you run a tube guitar amp into a higher than rated impedance; this will fry your power tube socket, along with the tube in it. Lower-powered amps are certainly not immune to this, judging by the number of tube sockets I've replaced in Fender Champs and small Gibsons over the years. Get the correct impedance speaker. Lord Valve Expert Yes, we hear what you are saying and without any load on the amp the anode to anode signal voltage can be maybe 2,000Vrms instead of a maximum of say 500Vrms with a load of below 20 ohms is at the output. The majority of guitar amps are set up for maximum power into a load which is slightly less than what SHOULD be used anyway so that the typical operation is to have a small amount of class A% power in the total class AB power. So changing from say 4 ohms to 8 ohms is never going to cause a problem of overloading. However, the speaker will have a resonant frequency where the Z of the speaker is very high at some bass F, and 50+ ohms would not be uncommon, so regardless of what sort of speaker is fitted there will be an impedance at bass which is way above the rated Z of 4 or 8 ohms which is only valid for the mid F, say at 400Hz. The inductive nature of the voice coil will have the Z rising at 6dB/octave above a pole at say 500Hz, so by 5kHz, the speaker Z has gone very high, and as you know ppl run their amps with treble and brightness turned right up, so that the amp is overloaded by HF before the bass F cause overloading. The resulting distortions are much favoured by rock'n'rollers, and when the wave forms become clipped the HF content is even greater, and there is even more risk of arcing. So regardless of what you say Lord V, there is always a risk of arcing at the tube sockets because there is so little ever done to prevent it, like say having diodes connected from each anode to ground, to prevent the Vswing ever moving negative with respect to 0V, and thus prevent Eamax ever swinging more than twice the supply voltage. There is never ever any Zobel network connected across the output so there is a HF load on the amp. Guitar amp makers rarely ever do anything to prevent over voltaging the tube sockets and OPT insulation because they don't give a **** if an amp blows up because its going to then need replacing, and they like the new business, any way they can get it. So after considering what LV has siad, and has NOT said, and what I have brought to folk's attention, I would maintain that changing from a 4 ohm speaker to 8 ohms is OK. The amount of class A power is increased, although maybe the overall power is reduced, which won't alter percieved volume levels much. The tubes won't be subject to such high peak currents and should perhaps last a few gigs longer. Patrick Turner. |
#42
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Ian Iveson wrote: zyx wrote I have an epi valve jr combo with 8" speaker that is 4 ohms. I want to try it on a 12" speaker which is 8 ohms. Jam away? A bit risky. Anode voltage may rise higher than some parts can cope with reliably. As a general rule, SS amps don't care too much about a higher load impedance, and valves are tolerant of a lower one. SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, so risk of arcing in SS amps is not a problem. Sensible SS guitar amps have diodes from the output to the rails to prevent swings on the output ever going more than the rail voltage peak value, since this can occur with the inductive load of a speaker, and cause instant death to the output bjts with reverse flow currents. Tube guitar amps under discussion don't have any precautions to limit anode voltage swings way above what happens with 4,8, or 16 ohms. Low value loads on tube guitar amps means much earlier death for the tubes, as evidenced in amps used for heavy metal / grunge band use where the guitar sound is a continuous stream of square waves during gross output tube saturation. NEVER use a lower than recommended load on a tube amp. If you do, send the bill for new tubes to Ian who will pay because he advises its OK. Patrick Turner. cheers, Ian |
#43
Posted to rec.audio.tubes
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Stevenson = CRIMIINAL LIAR
"Eeysore the ****WIT POMMY **** " "Arny Krueger" Ironically, if one takes Phil's advice and searches alt.guitar.amps for posts about flyback spikes, you find him dodging the same basic question you asked about generating 5 Kv spikes around 2/25/2003, for example. ** Massive, silly LIE. There are no relevant posts there from me around that date. UTTER ******** ! http://groups.google.com/group/alt.g...2b685575212897 ** Shame how the date is the 19th, not the 25th as stated. Shame how the issue is not the same one alluded to by Arny. **** the HELL OFF & DIE you POMMY ASS !! ......... Phil |
#44
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Eeyore wrote: Ian Iveson wrote: zyx wrote I have an epi valve jr combo with 8" speaker that is 4 ohms. I want to try it on a 12" speaker which is 8 ohms. Jam away? A bit risky. Anode voltage may rise higher than some parts can cope with reliably. Oh puhleeze ! Is that nonsense or what ? As a general rule, SS amps don't care too much about a higher load impedance, and valves are tolerant of a lower one. Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will drive a 1 - 2 ohms load very well, yet many SS amps do it admirably. Graham Tube amps can be load matched to allow any low value load to be connected since there is an OPT which may have adjustable configurations of windings. Even many crummy old tube amps had matching for 4 or 16 ohms by paralleling or seriesing the two secondary OPT windings. This allowed a range of anything above 2 ohms, because the 4 ohm load may have given a match for class A, and the 2 ohm would be tolerated since the load is still an OK class AB load. The typical low levels used with hi-fi permit some load mismatch, but not in guitar amp world, a world of plectrum demons. SS amps have no such matching OPT or other device, and need current / voltage limiting. What is NEVER fitted to an SS amp is an intelligent circuit that detects if the load is below 2 ohms and TURNS THE AMP OFF even if it is used at low level. This safety option would save all the amps who expire when connected to shorted speaker cables or to fried/faulty speakers/crossovers. The makers of SS amps have had 40 years to fit decent active protection but they prefer you buy a ****ing new amp, rather than have the old one continue for too long. Tubes will also glow red and thermal out if the load is too low, but it just takes longer for it to happen. If an OPT is destroyed in the process, it can be very expensive! Patrick Turner. |
#45
Posted to rec.audio.tubes
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Stevenson = POMMY CRIMINAL LIAR
"Eeysore the Raving CRIMINAL LUNATIC" " " Normal operation ( for a guitar amp) is the case. " Ok - so *how easily* ? ** The question has been answered. Do your own tests if you want proof. Do a GG search on " alt .guitar.amps" on the topic of "flyback spikes " for confirmation the phenomenon is well known. So you're just making it up ( you can't or refuse to explain it ). ** What an UTTER non sequitur !!!!!!!! So go-on, what causes the 5kV ? ** So you have no idea what the term " flyback spikes" refers to ? I know exactly. But you do now accept that they really exist in valve amps ??? If the load's disconnected for sure. ** Err - what about inductive loads ?? Like guitar speaker cabs ?? Finally did a little Googling - did we ? No need. ** But I bet you did so anyhow - LIAR !! Now, how did *YOU* get 5kV flyback spikes. What was the load ? ** A quad box, 4 x Celestion 12 inch, wired series /parallel. An 8 or 16 ohm dummy load with series inductor of a few mH simulates the above. How hard was the amp being driven ? ** Full overdrive / clipping. Just like most guitarist play their Marshalls for hours on end. What was the input signal ? ** A slide guitarist with his Gibson SG demonstrated in one case. A sine wave bench gen does nicely too. BTW : I don't expect a VILE CRIMINAL LUNATIC like Graham Stevenson to accept a single word of this. He did not ask me in order to find out the facts. Having done NO such tests himself - he has not the SLIGHTEST clue about it. He will never do any either. ........ Phil |
#46
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Patrick Turner wrote: Ian Iveson wrote: zyx wrote I have an epi valve jr combo with 8" speaker that is 4 ohms. I want to try it on a 12" speaker which is 8 ohms. Jam away? A bit risky. Anode voltage may rise higher than some parts can cope with reliably. As a general rule, SS amps don't care too much about a higher load impedance, and valves are tolerant of a lower one. SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, Not to mention diodes fron output to supply rails too. Graham |
#47
Posted to rec.audio.tubes
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Stevenson = CRIMIINAL LIAR
Phil Allison wrote: "Eeysore the ****WIT POMMY **** " "Arny Krueger" Ironically, if one takes Phil's advice and searches alt.guitar.amps for posts about flyback spikes, you find him dodging the same basic question you asked about generating 5 Kv spikes around 2/25/2003, for example. ** Massive, silly LIE. There are no relevant posts there from me around that date. UTTER ******** ! http://groups.google.com/group/alt.g...2b685575212897 ** Shame how the date is the 19th, not the 25th as stated. You said " around that date.". Which it is. 15 From: Phil Allison - view profile Date: Tues, Feb 18 2003 10:08 pm Shame how the issue is not the same one alluded to by Arny. It is exactly...... " ** There are often MAJOR inductive spikes with a nominally **correctly loaded** amp when run very hard into real speakers or simulated reactive loads - I have measured up to 5 kV peaks on the tube plates with a 100 W Marshall with 8 ohms plus 5 mH. " Graham |
#48
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Patrick Turner wrote: Eeyore wrote: Ian Iveson wrote: zyx wrote I have an epi valve jr combo with 8" speaker that is 4 ohms. I want to try it on a 12" speaker which is 8 ohms. Jam away? A bit risky. Anode voltage may rise higher than some parts can cope with reliably. Oh puhleeze ! Is that nonsense or what ? As a general rule, SS amps don't care too much about a higher load impedance, and valves are tolerant of a lower one. Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will drive a 1 - 2 ohms load very well, yet many SS amps do it admirably. Graham Tube amps can be load matched to allow any low value load to be connected since there is an OPT which may have adjustable configurations of windings. I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers. Have you ever seen a 2 ohm tap btw ? Graham |
#49
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
"Eeysore the ****ing Pommy ****head " Patrick Turner wrote: SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, Not to mention diodes fron output to supply rails too. ** Ahhh - the diodes are to catch those pesky flyback spikes, yet again. The ones this ASININE POMMY ****HEAD denies exist. ROTFLMAO !!! What an absolute hoot this Stevenson Criminal Nutter is !! ........ Phil |
#50
Posted to rec.audio.tubes
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Allison's boomerang came back
Eeyore wrote: Phil Allison wrote: "Eeysore the Raving LUNATIC" " ** The question has been answered. Do your own tests if you want proof. Do a GG search on " alt .guitar.amps" on the topic of "flyback spikes " for confirmation the phenomenon is well known. So you're just making it up ( you can't or refuse to explain it ). ** What an UTTER non sequitur !!!!!!!! So go-on, what causes the 5kV ? You don't know do you ? Graham I suggest that where you have an OPT which has a large amount of inductance in its primary, that where the anode current is sharply cut off, as is the case in an unloaded pentode amp which is over driven, then there are huge emfs produced unless these are shunted somehow. The simplest way to avoid the phenomenon that Phil Allison and myself and LV say occurs, is to connect 3 x IN4007 in series from each anode to 0V so that the diode cathodes are at the tube anodes, and diode anodes are at 0V. Under normal use there s no flow in the diodes to 0V, but should a large back emf occur, it will try to one end of the OPT primary very +ve while sending the other end very -ve, and THEN THE DIODES CONDUCT and this loads the OPT and shunts the back emf, thus limiting, or clamping the output T primary voltage. I have never seen 5,000Vrms in a wayward unloaded OPT, but I can't say it wouldn't occur. I have seen many amps suffer from arcing because of the rather highish ordinary working voltages including those with B+ rail = 350V and with EL84 etc, but this usually occurs because the sockets/underchassis area is polluted, or damp, or the OPT is dmap after storage in a damp place for 20 years. Amps using EL34 with B+ = 900V and Eg2 = 450V are VERY PRONE TO ARCING between the anode pin 3 and the earthy heater pin 2 on the octal socket. 807 amps with 600V at the anode top cap and only 300V at Eg2 are less prone to socket worries but the OPT is still very prone to arcing if not well insulated or varnished. Patrick Turner |
#51
Posted to rec.audio.tubes
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Stevenson = CRIMINAL LIAR
Eeysore the ****WIT POMMY **** "
"Arny Krueger" Ironically, if one takes Phil's advice and searches alt.guitar.amps for posts about flyback spikes, you find him dodging the same basic question you asked about generating 5 Kv spikes around 2/25/2003, for example. ** Massive, silly LIE. There are no relevant posts there from me around that date. UTTER ******** ! http://groups.google.com/group/alt.g...2b685575212897 ** Shame how the date is the 19th, not the 25th as stated. You said " around that date." Which it is. ** No - it is 6 days earlier & cannot be in the same thread as Arny is saying. Shame how the issue is not the same one alluded to by Arny. It is exactly...... ** The post is NOT relevant to the claim Arny's made above. YOU ASININE, ASD ****ED IDIOT !!. ......... Phil |
#52
Posted to rec.audio.tubes
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From the Mouths of Babes.....
"Patrick Turner" The simplest way to avoid the phenomenon that Phil Allison and myself and LV say occurs, ** Just wanna make sure this does not go unnoticed. is to connect 3 x IN4007 in series from each anode to 0V so that the diode cathodes are at the tube anodes, ** Best use high speed diodes. Watch out for the traps in doing this too. The exact position of fuses or standby switches in an amp's circuit can make this idea very un-safe. ............ Phil |
#53
Posted to rec.audio.tubes
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Stevenson = POMMY CRIMINAL LIAR
Phil Allison wrote: "Eeysore the Raving CRIMINAL LUNATIC" " " Normal operation ( for a guitar amp) is the case. " Ok - so *how easily* ? ** The question has been answered. Do your own tests if you want proof. Do a GG search on " alt .guitar.amps" on the topic of "flyback spikes " for confirmation the phenomenon is well known. So you're just making it up ( you can't or refuse to explain it ). ** What an UTTER non sequitur !!!!!!!! So go-on, what causes the 5kV ? ** So you have no idea what the term " flyback spikes" refers to ? I know exactly. But you do now accept that they really exist in valve amps ??? If the load's disconnected for sure. ** Err - what about inductive loads ?? Like guitar speaker cabs ?? Finally did a little Googling - did we ? No need. ** But I bet you did so anyhow - LIAR !! I didn't. As I said - simply no need. Now, how did *YOU* get 5kV flyback spikes. What was the load ? ** A quad box, 4 x Celestion 12 inch, wired series /parallel. An 8 or 16 ohm dummy load with series inductor of a few mH simulates the above. How hard was the amp being driven ? ** Full overdrive / clipping. Just like most guitarist play their Marshalls for hours on end. What was the input signal ? ** A slide guitarist with his Gibson SG demonstrated in one case. A sine wave bench gen does nicely too. So why didn't you just say this when I originally asked ? BTW : I don't expect a VILE CRIMINAL LUNATIC like Graham Stevenson to accept a single word of this. He did not ask me in order to find out the facts. Having done NO such tests himself - he has not the SLIGHTEST clue about it. He will never do any either. I do accept it. In fact I accepted it when you first posted it if you bother to check. What I said in fact was that if you can create 5kV spikes with the *correct* load, then changing it from 4 to 8 ohms isn't going to change that. Graham |
#54
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Patrick Turner wrote: What is NEVER fitted to an SS amp is an intelligent circuit that detects if the load is below 2 ohms and TURNS THE AMP OFF even if it is used at low level. This safety option would save all the amps who expire when connected to shorted speaker cables or to fried/faulty speakers/crossovers. Actually QSC have a very crude system that does do this. http://www.freepatentsonline.com/4321554.html It's an area I've been looking into myself actually as it can hugely benefit amplifier design by eliminating 'hard' current limiting. Graham |
#55
Posted to rec.audio.tubes
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Stevenson = CRIMINAL LIAR
"Phil Allison" wrote in message
Eeysore the ****WIT POMMY **** " "Arny Krueger" Ironically, if one takes Phil's advice and searches alt.guitar.amps for posts about flyback spikes, you find him dodging the same basic question you asked about generating 5 Kv spikes around 2/25/2003, for example. ** Massive, silly LIE. There are no relevant posts there from me around that date. UTTER ******** ! http://groups.google.com/group/alt.g...2b685575212897 ** Shame how the date is the 19th, not the 25th as stated. You said " around that date." Which it is. ** No - it is 6 days earlier & cannot be in the same thread as Arny is saying. I specified no particular thread, Phil. Time to admit that Graham is right and you were wrong. |
#56
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Phil Allison wrote: "Eeysore the ****ing Pommy ****head " Patrick Turner wrote: SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, Not to mention diodes fron output to supply rails too. ** Ahhh - the diodes are to catch those pesky flyback spikes, yet again. The ones this ASININE POMMY ****HEAD denies exist. ROTFLMAO !!! What an absolute hoot this Stevenson Criminal Nutter is !! None of which has anything to do with loading a 4 ohm tap with 8 ohms. Graham |
#57
Posted to rec.audio.tubes
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Stevenson = POMMY CRIMINAL LIAR
"Eeysore the Raving CRIMINAL LUNATIC" " " Normal operation ( for a guitar amp) is the case. " Ok - so *how easily* ? ** The question has been answered. Do your own tests if you want proof. Do a GG search on " alt .guitar.amps" on the topic of "flyback spikes " for confirmation the phenomenon is well known. So you're just making it up ( you can't or refuse to explain it ). ** What an UTTER non sequitur !!!!!!!! So go-on, what causes the 5kV ? ** So you have no idea what the term " flyback spikes" refers to ? I know exactly. But you do now accept that they really exist in valve amps ??? If the load's disconnected for sure. ** Err - what about inductive loads ?? Like guitar speaker cabs ?? Finally did a little Googling - did we ? No need. ** But I bet you did so anyhow - LIAR !! I didn't. As I said - simply no need. ** Blatant LIE !! Now, how did *YOU* get 5kV flyback spikes. What was the load ? ** A quad box, 4 x Celestion 12 inch, wired series /parallel. An 8 or 16 ohm dummy load with series inductor of a few mH simulates the above. How hard was the amp being driven ? ** Full overdrive / clipping. Just like most guitarist play their Marshalls for hours on end. What was the input signal ? ** A slide guitarist with his Gibson SG demonstrated in one case. A sine wave bench gen does nicely too. So why didn't you just say this when I originally asked ? ** I did say, over and over, it was with a speaker cab and normal guitar amp use. You never asked specific, defined questions previously. Only ones full of ambiguity and smartarse. BTW : I don't expect a VILE CRIMINAL LUNATIC like Graham Stevenson to accept a single word of this. He did not ask me in order to find out the facts. Having done NO such tests himself - he has not the SLIGHTEST clue about it. He will never do any either. I do accept it. In fact I accepted it when you first posted it if you bother to check. ** Then decided to contradict it like all hell - eg: " But you do now accept that they really exist in valve amps ??? If the load's disconnected for sure. " What I said in fact was that if you can create 5kV spikes with the *correct* load, then changing it from 4 to 8 ohms isn't going to change that. ** Which is WRONG. It *does* change things and often for the worse. Depends on specific and individual cases whether a failure will occur. I have already answered you on this. The POINT is that ALL guitar amps that suffer from large voltage " flyback spikes" are an accident just waiting to happen. ........ Phil |
#58
Posted to rec.audio.tubes
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Allison = CRIMINALLY DEFECTIVE LUNATIC
Phil Allison wrote: Eeysore the ****WIT POMMY **** " "Arny Krueger" Ironically, if one takes Phil's advice and searches alt.guitar.amps for posts about flyback spikes, you find him dodging the same basic question you asked about generating 5 Kv spikes around 2/25/2003, for example. ** Massive, silly LIE. There are no relevant posts there from me around that date. UTTER ******** ! http://groups.google.com/group/alt.g...2b685575212897 ** Shame how the date is the 19th, not the 25th as stated. You said " around that date." Which it is. ** No - it is 6 days earlier & cannot be in the same thread as Arny is saying. The date is close enough for me and the thread was about exactly the same topic we're discussing here ! Why on earth would you want to deny it ? Graham |
#59
Posted to rec.audio.tubes
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ARNY = CRIMINAL LIAR
"Arny Krueger" " Ironically, if one takes Phil's advice and searches alt.guitar.amps for posts about flyback spikes, you find him dodging the same basic question you asked about generating 5 Kv spikes around 2/25/2003, for example. " ** No - it is 6 days earlier & cannot be in the same thread as Arny is saying. I specified no particular thread, Phil. ** You specified a date and a * particular * line of content. Both are missing in that link. Where the **** is it ?? Were you LYING or just totally WRONG as USUAL ??? Time to admit that Graham is right and you were wrong. ** Go get totally ****ED you MONSTROUSLY EVIL HYPOCRITE ......... Phil |
#60
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
"Eeysore the ****ing Pommy ****head " Patrick Turner wrote: SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, Not to mention diodes fron output to supply rails too. ** Ahhh - the diodes are to catch those pesky flyback spikes, yet again. The ones this ASININE POMMY ****HEAD denies exist. ROTFLMAO !!! What an absolute hoot this Stevenson Criminal Nutter is !! None of which has anything to do with loading a 4 ohm tap with 8 ohms. ** Not the claim of yours at issue. As you very well know. ......... Phil |
#61
Posted to rec.audio.tubes
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Stevenson = POMMY CRIMINAL LIAR
Phil Allison wrote: "Eeysore the Raving CRIMINAL LUNATIC" " So why didn't you just say this when I originally asked ? ** I did say, over and over, it was with a speaker cab and normal guitar amp use. Rubbish, you only just posted that answer once about half an hour ago. Anyone looking at the time stamps on the posts can see that for themselves. You never asked specific, defined questions previously. They were perfectly clear ! Only ones full of ambiguity and smartarse. And how exactly is that any different from you ? Weren't you smart enough to understand my question ? Graham |
#62
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Phil Allison wrote: "Eeysore the ****ing Pommy ****head " Patrick Turner wrote: SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, Not to mention diodes fron output to supply rails too. ** Ahhh - the diodes are to catch those pesky flyback spikes, yet again. The ones this ASININE POMMY ****HEAD denies exist. ROTFLMAO !!! What an absolute hoot this Stevenson Criminal Nutter is !! None of which has anything to do with loading a 4 ohm tap with 8 ohms. ** Not the claim of yours at issue. Show where I claimed anything else. As you very well know. No. It was you who brought up the *off-topic* issue of 5kV spikes with *correct* loading. Graham |
#63
Posted to rec.audio.tubes
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Graham Stevenson = CRIMINAL LIAR
"Eeysore the Raving CRIMINAL LUNATIC" " So why didn't you just say this when I originally asked ? ** I did say, over and over, it was with a speaker cab and normal guitar amp use. Rubbish, you only just posted that answer once about half an hour ago. ** INSANE CRAPOLOGY ! This post was 10.5 hours ago. " Eg, any Marshall valve amp can easily be made to exhibit +/- 5 kV spikes on the output plates when operating into a speaker cab. " ** This was only 44 mins later: " Normal operation ( for a guitar amp) is the case. " ** Then, 7 hours ago, I combined them for you: " Eg, any Marshall valve amp can easily be made to exhibit +/- 5 kV spikes on the output plates when operating into a speaker cab. LVs phrase " high tension flyback " is a very apt one - cos it don't happen with a resistive load. " " Normal operation ( for a guitar amp) is the case. " Anyone looking at the time stamps on the posts can see that for themselves. ** See CLEARLY what a damn INSANE LIAR you are !!! ........ Phil |
#64
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
"Eeysore the ****ing Pommy ****head " ** Ahhh - the diodes are to catch those pesky flyback spikes, yet again. The ones this ASININE POMMY ****HEAD denies exist. ROTFLMAO !!! What an absolute hoot this Stevenson Criminal Nutter is !! None of which has anything to do with loading a 4 ohm tap with 8 ohms. ** Not the claim of yours at issue. Show where I claimed anything else. ** Here it is: " Utter garbage. The voltage swings on the primary of the output transformer are typically well *under* a thousand volts. They cannot in any case exceed 2 x B+ in normal operation. " Denies the existence of flyback spikes, even in guitar amps. No. It was you who brought up the *off-topic* issue of 5kV spikes with *correct* loading. ** LV mentioned " high tension flyback" . I quoted this remark in my first post. Then gave some actual figures. Not OT in the slightest. You PITA ****ing Dim Wit. ......... Phil |
#65
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Eeyore said:
There are only 2 professional designers here and they are Patrick Turmer and myself. Oh? Just the 2 of you? ;-) Lord Valve is a very experienced tube expert at the practical level but has no design experience AFAIK. Repair experience is probably even more useful, one gets to see all different kinds of amps, topologies and failures. One can get a very good insight about the weak spots in designs by a lifelong career in repairing various audio gear. At least, that's where I came from. And I still do repair every now and then, of MI and SR amps, domestic audio and studio gear. I would take LV's advice about tubes and guitar amps over anyone elses every day, despite the fact that we're hardly friends. -- - Maggies are an addiction for life. - |
#66
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Safe for 4 ohms into 8 ohms?
Eeyore said:
Have you ever seen a 2 ohm tap btw ? Yes. My own OPTs have 2.83 ohm taps, in fact. I use them to drive 2 paralleled Magnepans per channel. -- - Maggies are an addiction for life. - |
#67
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
The RAT's ass mumbled: Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will drive a 1 - 2 ohms load very well, yet many SS amps do it admirably. Graham Tube amps can be load matched to allow any low value load to be connected since there is an OPT which may have adjustable configurations of windings. I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers. Have you ever seen a 2 ohm tap btw ? Where ya been, junior? Two of the "Holy Grail of Tone" amps - the Fender '59 Tweed Bassman and the Fender '65 blackface Super Reverb - have 2-ohm outputs. (So does the famous Ampeg SVT, designed to drive one or two 4-ohm cabinets containing eight 10" 32-ohm speakers wired in parallel, with a switching jack for selecting the 2-ohm tap when two cabinets are used. Try running one of those into an upward mismatch - 8 ohm box on the 4-ohm tap - and watch the fireworks.) Both of the Fender amps drive four 10" 8-ohm speakers wired in parallel. A few times a year - *every* year since I have been repairing guitar amps, and that would be about 40 of 'em years) I've had to fix several of these amps which had the speaker wiring "corrected" to the much more common series-parallel arrangement that produces an 8-ohm load from four 8-ohm speakers. Said "correction" usually performed by some audiophool "expert" who "knew" that tube amps don't drive 2-ohm loads. Of course, as soon as this "repair" was accomplished, the poor *******'s amp started blowing fuses. Seems the sockets were arced. Imagine that. Lord Valve Expert |
#68
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Safe for 4 ohms into 8 ohms?
In article ,
Patrick Turner wrote: SS amps have a load of NFB and there is a Zobel network which loads the output, and there is no OPT, so no high voltages with no load, and supply voltages are lower anyway, so risk of arcing in SS amps is not a problem. Sensible SS guitar amps have diodes from the output to the rails to prevent swings on the output ever going more than the rail voltage peak value, since this can occur with the inductive load of a speaker, and cause instant death to the output bjts with reverse flow currents. I have had that happen in an amp without the diodes you mention. When it went it made quite a show, the transistors were in TO-3 packages and when it went one stated arcing between the emitter post inside and the top of the package. The arc cut a hole through the top of the package and started blasting out a jet of hot metal and flame sort of like some sort of plasma torch, until I killed the power. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#69
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Safe for 4 ohms into 8 ohms?
In article ,
Patrick Turner wrote: So regardless of what you say Lord V, there is always a risk of arcing at the tube sockets because there is so little ever done to prevent it, like say having diodes connected from each anode to ground, to prevent the Vswing ever moving negative with respect to 0V, and thus prevent Eamax ever swinging more than twice the supply voltage. You are assuming the transformer has no leakage inductance between primary halves, is this a valid assumption for the typical guitar amp? Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#70
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Safe for 4 ohms into 8 ohms?
"Eeyore" wrote in message ... Patrick Turner wrote: Eeyore wrote: Ian Iveson wrote: zyx wrote I have an epi valve jr combo with 8" speaker that is 4 ohms. I want to try it on a 12" speaker which is 8 ohms. Jam away? A bit risky. Anode voltage may rise higher than some parts can cope with reliably. Oh puhleeze ! Is that nonsense or what ? As a general rule, SS amps don't care too much about a higher load impedance, and valves are tolerant of a lower one. Tolerant to a point ! I wouldn't advise it. In fact I doubt any valve amps will drive a 1 - 2 ohms load very well, yet many SS amps do it admirably. Graham Tube amps can be load matched to allow any low value load to be connected since there is an OPT which may have adjustable configurations of windings. I had in mind the 'typical' 4, 8 and 16 ohm taps on most power amplifiers. Have you ever seen a 2 ohm tap btw ? Yep. I have an amp on my bench with a stock Sowter UK transformer. The secondary windings can be connected in series and in parallel for 1,4,8, and 16 Ohms. Iain Graham |
#71
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Safe for 4 ohms into 8 ohms?
"Sander deWaal" wrote in message ... Eeyore said: There are only 2 professional designers here and they are Patrick Turmer and myself. Oh? Just the 2 of you? ;-) Lord Valve is a very experienced tube expert at the practical level but has no design experience AFAIK. Repair experience is probably even more useful, one gets to see all different kinds of amps, topologies and failures. One can get a very good insight about the weak spots in designs by a lifelong career in repairing various audio gear. At least, that's where I came from. And I still do repair every now and then, of MI and SR amps, domestic audio and studio gear. I would take LV's advice about tubes and guitar amps over anyone elses every day, despite the fact that we're hardly friends. -- - Maggies are an addiction for life. - Thanks for your honesty and I think I'll trust LV's advices. I remember long ago that the tubes have speakers rated at 3.2 ohms. 4 ohms sure ain't far from that. Now another question. Can this little 5 watt single ended class A amp (12ax7 and el84) drive a 2x12 speakers? I believe wiring two 8 ohm speakers in parallel will give me 4 ohms? |
#72
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Safe for 4 ohms into 8 ohms?
zyx wrote: "Sander deWaal" wrote in message Eeyore said: There are only 2 professional designers here and they are Patrick Turmer and myself. Oh? Just the 2 of you? ;-) Lord Valve is a very experienced tube expert at the practical level but has no design experience AFAIK. Repair experience is probably even more useful, one gets to see all different kinds of amps, topologies and failures. One can get a very good insight about the weak spots in designs by a lifelong career in repairing various audio gear. At least, that's where I came from. And I still do repair every now and then, of MI and SR amps, domestic audio and studio gear. I would take LV's advice about tubes and guitar amps over anyone elses every day, despite the fact that we're hardly friends. - Maggies are an addiction for life. - Thanks for your honesty and I think I'll trust LV's advices. I remember long ago that the tubes have speakers rated at 3.2 ohms. 4 ohms sure ain't far from that. Now another question. Can this little 5 watt single ended class A amp (12ax7 and el84) drive a 2x12 speakers? Their physical size is unimportant from the perspective of whether the amp can drive them. You will however miss out on any colouration that you might typically associate with such speakers though. Guitar amplification often relies strongly on exploiting the technical 'shortcomings' of traditional amplification equipment in an 'artistic' way. The speakers themselves play a part in this with their 'overdriven' sound. You won't be overdriving a 12" speaker with 2-3 watts though. I believe wiring two 8 ohm speakers in parallel will give me 4 ohms? It will indeed. Graham |
#73
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Safe for 4 ohms into 8 ohms?
"Sander deWaal" Repair experience is probably even more useful, one gets to see all different kinds of amps, topologies and failures. One can get a very good insight about the weak spots in designs by a lifelong career in repairing various audio gear. ** But ONLY if that technician is * insatiably curious* about audio electronics and puts in the time and considerable mental effort to analyse nearly every circuit & component failure scenario they come across. The vast majority of service techs are not allowed ( even if they wanted to) to indulge in such time consuming, non profit making activity when there is other work waiting to be done and a prowling boss to keep happy. Only independent, self employed techs who are not too overworked might do as you suggest, even then only if they have the required technical ability. The typical product design engineer never gets involved with repairs, even to his own designs, gets little or no feedback from the field unless a very serious failure situation arises. They are normally quite unwilling to accept any input or criticism from ANY folk involved in the repair business and especially not from other designers. This of course condemns them to repeating their dumbest mistakes - which are then mass produced, sold to a gullible marketplace and ultimately left to mere repair techs to eventually unravel & attempt to find fixes for. I have many times wished I could deliver some expensive pile of audio garbage back to the doorstep of the utter ass who is responsible for it and say - " you designed this POS - so you bloody fix it " !! ........ Phil |
#74
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Safe for 4 ohms into 8 ohms?
On Thu, 18 Jan 2007 14:34:29 GMT, Lord Valve
wrote: Despite what you may have seen from a loud-mouthed know-it-all on this NG, don't worry. Well, ****-fire and boy howdy, son... First of all, let me apologize for what, last night, seemed like a funny play on your larger-than-life reputation, but today just reads as awful. You're a real gentleman to have let it slide so easily. You're wrong, but you can derive some small solace from the fact that you're wrong for all the right reasons, chief among them being ignorance regarding actual field operating conditions for *guitar* amplifiers. You've also never seen an Epiphone Valve Junior, nor the schematic thereto. Right? Spent more than three decades doing bench repairs, but fortunately never met these Chinese Firecracker Champs. That you're having to repair 'em at all makes me wonder if the repairs are on your dime - my heart goes out to ya either way. Lotta work for little return. It's too late to fix their design issues, but it'd be interesting to know how the external speakers connect. Speaker cabs are wired several different ways. Do these connect the external speakers in parallel with the internal or do the jacks disconnect the internal speaker? Is the jack make-before-break? They could even be connected in series. God dwells in the details. You're obviously seeing a real issue here, but I'll have to stand by my statement that the nominal speaker impedance is the wrong place to be looking. Uhh... I think. Much thanks, as always, Chris Hornbeck "History consists of truths which in the end turn into lies, while myth consists of lies which finally turn into truths." - Jean Cocteau |
#75
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Safe for 4 ohms into 8 ohms?
On Fri, 19 Jan 2007 12:49:27 +1100, "Phil Allison"
wrote: "Sander deWaal" Repair experience is probably even more useful, one gets to see all different kinds of amps, topologies and failures. One can get a very good insight about the weak spots in designs by a lifelong career in repairing various audio gear. ** But ONLY if that technician is * insatiably curious* about audio electronics and puts in the time and considerable mental effort to analyse nearly every circuit & component failure scenario they come across. The vast majority of service techs are not allowed ( even if they wanted to) to indulge in such time consuming, non profit making activity when there is other work waiting to be done and a prowling boss to keep happy. Only independent, self employed techs who are not too overworked might do as you suggest, even then only if they have the required technical ability. The typical product design engineer never gets involved with repairs, even to his own designs, gets little or no feedback from the field unless a very serious failure situation arises. They are normally quite unwilling to accept any input or criticism from ANY folk involved in the repair business and especially not from other designers. This of course condemns them to repeating their dumbest mistakes - which are then mass produced, sold to a gullible marketplace and ultimately left to mere repair techs to eventually unravel & attempt to find fixes for. I have many times wished I could deliver some expensive pile of audio garbage back to the doorstep of the utter ass who is responsible for it and say - " you designed this POS - so you bloody fix it " !! ....... Phil Excellent post, Phil, I congratulate you. As a "repair tech" I've always been amazed at the crap some engineers can come up with... at the same time, impressed with the bullet proof designs of others. And I've used my experience to design lots of equipment over the years - I use the "empirical design and idea theft" methods, picking the best circuits I've seen and modifying them to suit my needs. I would sooner follow an experienced independent tech then an unknown engineer any day. |
#76
Posted to rec.audio.tubes
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Safe for 4 ohms into 8 ohms?
Phil said:
The typical product design engineer never gets involved with repairs, even to his own designs, gets little or no feedback from the field unless a very serious failure situation arises. They are normally quite unwilling to accept any input or criticism from ANY folk involved in the repair business and especially not from other designers. Not typical in my experience. Within the larger manufacturing companies, the relationships between production engineering, research and development, and quality assurance are pretty much standard and optimised. In general, you won't find a problem that they don't already know about in minute detail. Unreliable or defective products are shipped for all sorts of structural reasons: inertia, internal politics, cash flow requirements, etc. Also, for the general consumer market, most new products will be sensibly designed to equal the accepted standards of reliability set by producers as a whole. The higher cost of producing a more reliable product can't be handed down to consumers who aren't willing to pay. Nevertheless, modern mass-produced consumer products, particularly electronics, have hugely reduced the cost of reliability. cheers, Ian |
#77
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Safe for 4 ohms into 8 ohms?
"Ian Iveson Colossal ****wit " The typical product design engineer never gets involved with repairs, even to his own designs, gets little or no feedback from the field unless a very serious failure situation arises. They are normally quite unwilling to accept any input or criticism from ANY folk involved in the repair business and especially not from other designers. Not typical in my experience. ** You do not have any - you stinking ASD ****ed LIAR. Within the larger manufacturing companies, the relationships between production engineering, research and development, and quality assurance are pretty much standard and optimised. ** Completely and UTTERLY beside the point. Iveson is totally illiterate. ........ Phil |
#78
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Safe for 4 ohms into 8 ohms?
Phil Allison wrote The typical product design engineer never gets involved with repairs, even to his own designs, gets little or no feedback from the field unless a very serious failure situation arises. They are normally quite unwilling to accept any input or criticism from ANY folk involved in the repair business and especially not from other designers. Not typical in my experience. ** You do not have any - you stinking ASD ****ed LIAR. ASD? You know nothing about what I do, or what I have done, for a living. I'm happy with your ignorance. I said "in my experience" in order to qualify "typical". Your idea of typical is only within your experience, too. You have experience of grubby back-street tinkering. I can understand why you feel bitter, but you are barking up the wrong tree. Within the larger manufacturing companies, the relationships between production engineering, research and development, and quality assurance are pretty much standard and optimised. ** Completely and UTTERLY beside the point. You missed the last sentence of the paragraph, which explained the link, silly. And the other paragraphs which clarified it. Let me make it a bit clearer. In my experience, and to my knowledge, the typical designer doesn't need you. There is adequate provision within the organisation to ensure that designers are aware of the performance of their designs in the field. Iveson is totally illiterate. Not totally. Slightly, sometimes. Takes me a while to do the crossword, but I get there in the end. love and kisses, Ian |
#79
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Safe for 4 ohms into 8 ohms?
Lord Valve wrote: Chris Hornbeck wrote: Despite what you may have seen from a loud-mouthed know-it-all on this NG, don't worry. Well, ****-fire and boy howdy, son... You're wrong, but you can derive some small solace from the fact that you're wrong for all the right reasons, chief among them being ignorance regarding actual field operating conditions for *guitar* amplifiers. You've also never seen an Epiphone Valve Junior, nor the schematic thereto. Right? So - this amp runs a single EL84, giving an output of around 4 watts RMS. One 12AX7. SS bridge rectifier for the HV, as well as one for the heaters. No screen resistor. The entire shebang - including the speaker - *retails* for $139, and can often be had for less than $100, brand new in the box. In short, it's a cheap-ass piece of Chinese ****, a bare-bones minimum design intended to sell for the lowest price possible - less, in fact, than most audiophools spend on a couple of snob-glass preamp tubes. Think any corners were cut? I've had around a half-dozen of these across my bench in the last year. All but one had the same problem: fried socket. Cause: "I hooked it up to my (brand XYZ) speaker cabinet cuz it wasn't loud enough for me to play with a drummer." Said speaker cabinet, of course, was nearly always an 8-ohm box. One was 16. This is a 4-watt amp commonly purchased by the worst gear abusers on the planet: guitar pickers. Since it's only 4 watts, it is *always* played at full-bore output clipping, for max distortion and "blues tone." Its (often short) life is one of maximum stress, placed upon the sleaziest components imaginable. Now, son - you may know what you may know, and it may well be at odds with what I've said, but I have hands-on time with this particular gizmo, and I know for certain it eats tube sockets when operated into a higher than spec load. If you want to show me the math which proves that a bumblebee can't fly, be my guest. I've seen 'em fly, so I'll take your "knowledge" with a grain of salt, if that's OK with you. You don't catch my ass on this NG telling the audiophools about their SET 300B snob designs for a fairly good reason: I know jack **** about 'em. The difference between me and the audio******s is that I can admit it. Lord Valve Expert Guitar Amp Dude Lordy Lord. I agree mostly. But the failures when speakers are changed from 8 to 16 ohms isn't why it fails; failures due to arcing is gonna happen anyway since a speaker presents a high Z at each siode of its power range, and chinese crapologists dunno how to make good ****. And the chinese dunno what they are doing except they try to copy **** and finish up with ****tier **** that you can poke a stick at..... They make 'Goochi' handbags for sheilas, 'Rolecks' watches for the un-wary, and any ****en thing goes as long as some poor ******* buys it. Patrick Turner. |
#80
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Allison's an Antipodean obfuscator.
Eeyore wrote: Phil Allison wrote: "Eeysore the Raving CRIMINAL LUNATIC" " " Normal operation ( for a guitar amp) is the case. " Ok - so *how easily* ? ** The question has been answered. Do your own tests if you want proof. Do a GG search on " alt .guitar.amps" on the topic of "flyback spikes " for confirmation the phenomenon is well known. So you're just making it up ( you can't or refuse to explain it ). ** What an UTTER non sequitur !!!!!!!! So go-on, what causes the 5kV ? ** So you have no idea what the term " flyback spikes" refers to ? I know exactly. But you do now accept that they really exist in valve amps ??? If the load's disconnected for sure. Finally did a little Googling - did we ? No need. Now, how did *YOU* get 5kV flyback spikes. What was the load ? How hard was the amp being driven ? What was the input signal ? Graham Graham, no need to react against Allison's poor manners which are a response to your inability to understand that perhaps 5,000V is possible in a guitar amp without a load. Try measuring one, and you will find out all about. Very much higher signal voltages anode to anode ARE generated by an unloaded pentode/beam tetrode output stage than the normal working loaded voltages. Patrick Turner. |
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