Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
I need to install a 60 Watt paging amplifier on a job. The maximum
load at this time is 42 Watts, however we need to have a slight amount of room to move in the future. So I felt that 60W unit would be a good cushion. I currently have in the shop a nice Technics 100 Watt mono amp that I rebuilt and have no plans for. I would really like to sell this to the customer to use for this application. The problem is though it does not have the 70V output that I need. So I had two thoughts. The first is can I buy a transformer that will have a primary of 4, 8, or 16 ohms and a secondary which will provide the 70V output that I need, and handle at least 60 Watts RMS? The second thought is this: I have a number of 60Watt amplifiers in the scrap pile with good transformers I'm sure. The schematics show these transformers hung on the outputs as though they were a speaker load. I have no idea what the primary impedance could be though on any of these transformers, but I was wondering if it is anything close to typical speaker impedance? If it was then perhaps I could pull one of these from a junker, hang the primary across the Technics amplifier output, (which I think is 8.0 ohms} and then have my 70V output? Has anyone ever done anything like this? Of course I would do a load test on the amp/transformer combination before selling it. Thanks for your thoughts on this. Lenny |
#2
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
"klem kedidelhopper" I need to install a 60 Watt paging amplifier on a job. The maximum load at this time is 42 Watts, however we need to have a slight amount of room to move in the future. So I felt that 60W unit would be a good cushion. I currently have in the shop a nice Technics 100 Watt mono amp that I rebuilt and have no plans for. I would really like to sell this to the customer to use for this application. The problem is though it does not have the 70V output that I need. So I had two thoughts. The first is can I buy a transformer that will have a primary of 4, 8, or 16 ohms and a secondary which will provide the 70V output that I need, and handle at least 60 Watts RMS? The second thought is this: I have a number of 60Watt amplifiers in the scrap pile with good transformers I'm sure. The schematics show these transformers hung on the outputs as though they were a speaker load. I have no idea what the primary impedance could be though on any of these transformers, but I was wondering if it is anything close to typical speaker impedance? If it was then perhaps I could pull one of these from a junker, hang the primary across the Technics amplifier output, (which I think is 8.0 ohms} and then have my 70V output? Has anyone ever done anything like this? Of course I would do a load test on the amp/transformer combination before selling it. Thanks for your thoughts on this. Lenny ** The Technics amp will probably blow up. You cannot use 70V line *step up* trannies with domestic hi-fi amps. Line voltage power amplifiers are specially designed to drive the included step up transformer - which presents a lethal load to most SS amplifiers. BTW "Technics mono 100W amp" leads to no particular model on Google. So what the **** have you really got ?? ..... Phil |
#3
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
In article
, klem kedidelhopper wrote: I need to install a 60 Watt paging amplifier on a job. The maximum load at this time is 42 Watts, however we need to have a slight amount of room to move in the future. So I felt that 60W unit would be a good cushion. I currently have in the shop a nice Technics 100 Watt mono amp that I rebuilt and have no plans for. I would really like to sell this to the customer to use for this application. The problem is though it does not have the 70V output that I need. Klem- You may be able to do what you want, but selling it makes you liable if anything catches fire! Suppose you connect your 100 Watt Technics amp directly to the distribution system. Maximum RMS voltage out of a 16 Ohm output would be 40 Volts. For a 70.7 Volt system, maximum power would be somewhat less than 100 Watts before it starts to clip. Using a 100 Watt (or 60 Watt) constant voltage transformer connected backwards to the amp may work for your purposes, but there might be a penalty in frequency response. Try it and see how it sounds. About forty years ago I did something similar with an amplifier and some constant voltage transformers. It was a jury-rigged background music system using an old Eico FM tuner and Heathkit monaural tube-type HiFi amplifier. Speakers were mounted in cardboard boxes. It worked and sounded quite well, considering! Fred |
#4
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
"Fred McKenzie" Suppose you connect your 100 Watt Technics amp directly to the distribution system. Maximum RMS voltage out of a 16 Ohm output would be 40 Volts. For a 70.7 Volt system, maximum power would be somewhat less than 100 Watts before it starts to clip. ** The most sensible thing to do is use with a domestic stereo amp is use it in bridge mode AVOIDING the step-up tranny entirely. This way, you will easily enough get 70V rms and with very little chance of damaging the amp as the resistance in the distributed speaker system plus cabling is likely to be more than 8 ohms. A simple ohm meter check will confirm this and if it is a tad less than 8 ohms, just add some ohms in series. ..... Phil |
#5
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
"A simple ohm meter check will confirm this and if it is a tad less
than 8 ohms, just add some ohms in series" After all the cock mouth asshole bull**** you spew here, you think DC resistance is the same or any way like impedance ? No wonder you're so ****ing hostile, you're ****ing incompetent and overcompensating. Your turn to eat it mother****. T |
#6
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
"Jeff Urbane is a PITA ****wit " "A simple ohm meter check will confirm this and if it is a tad less than 8 ohms, just add some ohms in series" After all the cock mouth asshole bull**** you spew here, you think DC resistance is the same or any way like impedance ? ** They ARE close relatives you know ..... Obviously any words of wisdom as wasted on this anencephalic oxygen thief. For the curious: The 8 ohms of resistance alluded to by me is in SERIES with any reactive/ inductive or saturating line transformer & speaker load as seen by the bridge mode amplifier. Soooo, no matter what the drive level or frequency, the resulting load Z cannot drop below that number. ..... Phil |
#7
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
You cannot use 70V line *step up* trannies with domestic
hi-fi amps. Line voltage power amplifiers are specially designed to drive the included step up transformer -- which presents a lethal load to most SS amplifiers. You might be right... And I'd certainly be cautious about using a constant-voltage transformer with an amp not specifically designed for it. But I suspect you don't understand how a transformer works -- that is, how it transforms impedances. Let's say a transformer is rated a 4 ohms to, oh, 1600 ohms. One side //does not// have an impedance of 4 ohms, or the other side 1600 ohms. Rather, the transformer has a turns ratio of 1:20, which produces a impedance transformation of the square of the ratio, or 1:400. The transformer would work in //any// application where this impedance ratio was needed, whatever the specific impedances were -- for example, 100 to 40000 ohms. (I'm ignoring considerations such as primary inductance, leakage, etc. The principle is the same.) |
#8
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
"William Sommerwerck" ** Bill - how do we get you to go away and stop ****ING trolling ?? Do we have to track you down to the stinking rock you hide under and get someone to bullet you between the ears ? Would breaking every bone in your body do the trick ? How about sticking a pike up your arse an out your chest ? Would that stop you ? ..... Phil |
#9
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
"Phil Allison" wrote in message
... "William Sommerwerck" ** Bill - how do we get you to go away and stop ****ING trolling? Do we have to track you down to the stinking rock you hide under and get someone to bullet you between the ears? Would breaking every bone in your body do the trick? How about sticking a pike up your arse an out your chest? Would that stop you? I'm curious as to how stating the truth is equivalent to trolling. Is it that just you don't being corrected, perhaps? My understanding is that Australian men are not averse to situational homosexual behavior. Stop by the next time you're in Seattle, and I'll teach you a thing or two. |
#10
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
William Sommerwerck" ** Bill - how do we get you to go away and stop ****ING trolling ?? Do we have to track you down to the stinking rock you hide under and get someone to bullet you between the ears ? Would breaking every bone in your body do the trick ? How about sticking a pike up your arse an out your chest ? Would that stop you ? You ****ing MORON !!! ..... Phil |
#11
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
On May 17, 7:24*am, "Phil Allison" wrote:
"William Sommerwerck" ** Bill - *how do we get you to go away and stop *****ING *trolling ?? Do we have to track you down to the stinking rock you hide under and get someone to bullet you between the ears ? Would breaking every bone in your body do the trick ? How about sticking a pike up your arse an out your chest ? Would that stop you ? .... *PhiI As I said previously the 100 watt Technics mono amplifier has just one output which I believe to be 8.0 ohms. The model number of the amp, for purposes of this discussion is irrelevant. One of the other "junker" amps I have here is also operational and is actually a control amplifier from an old school PA system. Among other circuits present in this unit, microphone etc, there are two paging circuits. One is a 3.0 watt amp which was used for paging to an individual classroom, and the other is a 60.0 watt amp which was used for "all call" or emergency paging throughout the building. The 60.0 watt amp is essentially built around an STK hybrid. It was powered by a + and - 60 volt DC supply. For this application the output of this amp is fed through a1000 uf cap in series with a small coil directly to the primary of the output transformer. The secondary has taps for 8.0, ohms, 25V and 70 volts. The spec sheet for the chip shows a typical connection diagram for test and evaluation purposes. The output load was a speaker load. I don't recall what the speaker impedance was, but it was either 8.0 or 16.0 ohms. Except for using the output transformer primary in place of the speaker load, the test circuit almost exactly mimics the school PA amplifier portion of the intercom system. That's where I got the idea of using a transformer (of this type) in my proposed application. I reasoned that if the primary was anything close to a typical speaker impedance and the 70.0 volt output side was properly loaded then how could this damage the Technics? I had another thought. First let me say that I'm well aware of how DC resistance is related to, but not equal to speaker impedance. Lets say for argument sake I was to measure the DC resistance of the 8.0 ohm tap on the transformer secondary. And lets assume that it happens to measure 2.0 ohms. We know that this tap has an impedance when operating in its normal environment of 8.0 ohms. Now knowing that, if I were to measure the transformer primary and it also measured something close to 2.0, can I assume an impedance close to 8.0 ohms for that primary as well? If not then how would one go about determining this? One other note I thought would be interesting to mention. Not every amplifier manufacturer does this but Bogen seems to on many of their PA amplifiers. They include what seems to be the equivalent impedance in parenthesis next to the voltage output. For instance, the four output terminals of the CHS 60 amplifiers I have here in the shop are marked as follows: 1. 8.0 ohms 2. 25 volt (10.4 ohms) 3. 16.0 ohms 4. 70.0 volt (82.0 ohms). And one final question. Phil, why did you deem it necessary to change the title of this thread? (I'm asking nicely). Lenny |
#12
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
On May 17, 8:59*am, "William Sommerwerck"
wrote: "Phil Allison" wrote in message ... "William Sommerwerck" I'm curious as to how stating the truth is equivalent to trolling. Is it that just you don't being corrected, perhaps? ~~Sigh... what you should have done Bill is to put this information on Wikipedia so Phil can read it, and then claim it as his own knowledge. My understanding is that Australian men are not averse to situational homosexual behavior. Stop by the next time you're in Seattle, and I'll teach you a thing or two. ~~Well, he is also known as Phallus-in, so...... John |
#13
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
"klem kedidelhopper" ** FFS - ****HEAD Watch where you put your ****ing POSTS !!!!!! ----------------------------------------------------- As I said previously the 100 watt Technics mono amplifier has just one output which I believe to be 8.0 ohms. The model number of the amp, for purposes of this discussion is irrelevant. ** That is not for a nut case moron like you to say. Technics do not make mono amps. Post the model number and prove me wrong !!!!!!!!!! That's where I got the idea of using a transformer (of this type) in my proposed application. I reasoned that if the primary was anything close to a typical speaker impedance and the 70.0 volt output side was properly loaded then how could this damage the Technics? ** The 70V transformer primary probably has a DC resistance of about 0.5 ohms At some low frequency, the iron core will saturate leaving you with a 0.5 ohm load on the amp - same goes for the transformers in the distributed speaker system. 70V line amps are SPECIAL - not just any old amp with a step-up tranny tacked on. Fraid it is all way too technical for a steaming great MORON like you. And one final question. Phil, why did you deem it necessary to change the title of this thread? ** Does not look like that on my newsreader. FFS post your reply to the relevant post !! ..... Phil |
#14
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
** The 70V transformer primary probably has a DC resistance
of about 0.5 ohms At some low frequency, the iron core will saturate, leaving you with a 0.5 ohm load on the amp - same goes for the transformers in the distributed speaker system. That assumes the "some low frequency" gets through to the transformer. I remember J Gordon Holt's review -- almost 50 years ago -- of the KLH Nine electrostatic speaker. He pointed out much the same thing, suggesting that a Really Big capacitor in series with the speaker's input (which is a transformer, as you know) when driving it with a transistor amplifier might be a good idea. By the way, core saturation from an AC current doesn't cause the inductance's impedance to "disappear" -- it just reduces it. |
#15
Posted to sci.electronics.repair
|
|||
|
|||
Message to Bill
"William Sommer****** = ****" ** Bill - how do we get you to go away and stop ****ING trolling ?? Do we have to track you down to the stinking rock you hide under and get someone to bullet you between the ears ? Would breaking every bone in your body do the trick ? How about sticking a pike up your arse an out your chest ? Would that stop you ? God I would like to see that so much. ..... Phil |
#16
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
klem kedidelhopper wrote: I need to install a 60 Watt paging amplifier on a job. The maximum load at this time is 42 Watts, however we need to have a slight amount of room to move in the future. So I felt that 60W unit would be a good cushion. I currently have in the shop a nice Technics 100 Watt mono amp that I rebuilt and have no plans for. I would really like to sell this to the customer to use for this application. The problem is though it does not have the 70V output that I need. So I had two thoughts. The first is can I buy a transformer that will have a primary of 4, 8, or 16 ohms and a secondary which will provide the 70V output that I need, and handle at least 60 Watts RMS? The second thought is this: I have a number of 60Watt amplifiers in the scrap pile with good transformers I'm sure. The schematics show these transformers hung on the outputs as though they were a speaker load. I have no idea what the primary impedance could be though on any of these transformers, but I was wondering if it is anything close to typical speaker impedance? If it was then perhaps I could pull one of these from a junker, hang the primary across the Technics amplifier output, (which I think is 8.0 ohms} and then have my 70V output? Has anyone ever done anything like this? Of course I would do a load test on the amp/transformer combination before selling it. Thanks for your thoughts on this. Lenny Lenny, the biggest difference in the amplifers is that a PA amp is designed to be used 24/7/365.25. The transformer adds isolation from the amplifer, as well. I see no problem, as long as you're willing to stand behind what you sell and tell them that the transformer was added to match the speaker wiring. MCM sells transformers for this application. We did it back in the '70s to clean up installations done by knowitalls, and their victims didn't want to pay for another amplifier. As far as matching constant voltage speaker system impedance, keep these numbers in mind: 70V = 5000/W which means your 100 W amp would be 50.00 Ohms. 25V = 625/W which means your 100 W amp would be 6.25 Ohms. 100W is in the ballpark of what I would specify for a 60W load, if you beleive that there will be more speakers installed at later date. It could drive up to 120W load, in most installations with no problems. -- You can't have a sense of humor, if you have no sense. |
#17
Posted to sci.electronics.repair
|
|||
|
|||
Audio output transformer
On May 18, 10:50*am, "Michael A. Terrell"
wrote: klem kedidelhopper wrote: I need to install a 60 Watt paging amplifier on a job. The maximum load at this time is 42 Watts, however we need to have a slight amount of room to move in the future. So I felt that 60W unit would be a good cushion. I currently have in the shop a nice Technics 100 Watt mono amp that I rebuilt and have no plans for. I would really like to sell this to the customer to use for this application. The problem is though it does not have the 70V output that I need. So I had two thoughts. The first is can I buy a transformer that will have a primary of 4, 8, or 16 ohms and a secondary which will provide the 70V output that I need, and handle at least 60 Watts RMS? * The second thought is this: I have a number of 60Watt amplifiers in the scrap pile with good transformers I'm sure. The schematics show these transformers hung on the outputs as though they were a speaker load. I have no idea what the primary impedance could be though on any of these transformers, but I was wondering if it is anything close to typical speaker impedance? *If it was then perhaps I could pull one of these from a junker, hang the primary across the Technics amplifier output, (which I think is 8.0 ohms} and then have my 70V output? Has anyone ever done anything like this? Of course I would do a load test on the amp/transformer combination before selling it. Thanks for your thoughts on this. Lenny * *Lenny, the biggest difference in the amplifers is that a PA amp is designed to be used 24/7/365.25. *The transformer adds isolation from the amplifer, as well. *I see no problem, as long as you're willing to stand behind what you sell and tell them that the transformer was added to match the speaker wiring. *MCM sells transformers for this application. *We did it back in the '70s to clean up installations done by knowitalls, and their victims didn't want to pay for another amplifier. * *As far as matching constant voltage speaker system impedance, keep these numbers in mind: 70V = 5000/W *which means your 100 W amp would be 50.00 Ohms. 25V = *625/W *which means your 100 W amp would be *6.25 Ohms. * *100W is in the ballpark of what I beleive that there will be more speakers installed at later date. It could drive up to 120W load, in most installations with no problems. -- You can't have a sense of humor, if you have no sense. Well as it turns out, (and Phil was correct), so call me an oxygen thief, ****wit or whatever else suits your fancy Phil, in that the amp is not a mono amp but a 100 Watt per channel stereo amp. So now I don't want to use this amp for this application. This has all been an interesting exercise but unfortunately I have now run out of amps so I may very well have to buy a 60watt paging amp. Lenny |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Confusing output voltage from transformer | UK diy | |||
Output transformer ambiguity | Electronics Repair | |||
Audio output transformer location | Electronics | |||
Mutli-output transformer | Electronics Repair | |||
wierd transformer output voltage | Electronics |