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#1
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Variac and New Amp
Hi,
I bought a small Cayin PP amp that puts out 12w per side(MT-12). The unit was made for the Japanese market which uses 100v 50-50hz. On the back of the amp (from the pictures) it looks to draw 120 watts. This would equate into 1.2 amps. I wanted to buy my friends 3 amp variac. Will this get the job done or should I be looking for a 5 amps Variac? Also, will the Variac added any noise or to the output of the amp? Thanks in advance |
#2
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Trader wrote: Hi, I bought a small Cayin PP amp that puts out 12w per side(MT-12). The unit was made for the Japanese market which uses 100v 50-50hz. On the back of the amp (from the pictures) it looks to draw 120 watts. This would equate into 1.2 amps. I wanted to buy my friends 3 amp variac. Will this get the job done or should I be looking for a 5 amps Variac? Also, will the Variac added any noise or to the output of the amp? Thanks in advance Why buy a variac? If someone dials up the wrong voltage, there could be some expensive troubles, like all the heaters going open.... Why not buy a fixed voltage transformer to get from the mains you have to the voltage of the amp you bought? It would need to be rated for about 150 VA at least. |
#3
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Patrick,
This makes great sense. I thought I could always use the Variac for other things. My friend said that they cheap Variac I wanted to buy would add to much noise to the line and kill the sound of my tube amp also. I did located a 500 watt step down transformer. Do you think that this will work without adding any noise the line and making my tube amp sound bad? Here is the url http://traveloasis.com/transformer2.html Thanks in advance. "Patrick Turner" wrote in message ... Trader wrote: Hi, I bought a small Cayin PP amp that puts out 12w per side(MT-12). The unit was made for the Japanese market which uses 100v 50-50hz. On the back of the amp (from the pictures) it looks to draw 120 watts. This would equate into 1.2 amps. I wanted to buy my friends 3 amp variac. Will this get the job done or should I be looking for a 5 amps Variac? Also, will the Variac added any noise or to the output of the amp? Thanks in advance Why buy a variac? If someone dials up the wrong voltage, there could be some expensive troubles, like all the heaters going open.... Why not buy a fixed voltage transformer to get from the mains you have to the voltage of the amp you bought? It would need to be rated for about 150 VA at least. |
#4
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Do you have 115 or 230V mains voltage? If you have 115V, you can use a 115/
15V power transformer with a primary winding connected to mains and a secondary winding connected in series in counterphase (so that the voltage that feeds the amp would be 115V-15V=100V) with the amp power iron's primary. A nice method of stepping voltage down Oh, and the 15V winding should be rated at least at approx. 1,5A (or more). |
#5
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Trader wrote: Patrick, This makes great sense. I thought I could always use the Variac for other things. My friend said that they cheap Variac I wanted to buy would add to much noise to the line and kill the sound of my tube amp also. The variac will work OK, and it won't add the slightest noise to your tube amp, providing there is an earth connection for where you plug in the amp. I did located a 500 watt step down transformer. Do you think that this will work without adding any noise the line and making my tube amp sound bad? Here is the url http://traveloasis.com/transformer2.html That should be perfect if you are going from 120v mains to the 100v required for the amp. I assume you have 120v mains. Patrick Turner. |
#6
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"Krzysiek Słychań" wrote: Do you have 115 or 230V mains voltage? If you have 115V, you can use a 115/ 15V power transformer with a primary winding connected to mains and a secondary winding connected in series in counterphase (so that the voltage that feeds the amp would be 115V-15V=100V) with the amp power iron's primary. A nice method of stepping voltage down Oh, and the 15V winding should be rated at least at approx. 1,5A (or more). I seriously think you advice would confuse our original poster, and place his amp and himself at some risk. Patrick Turner. |
#7
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"Patrick Turner" wrote in message
... I seriously think you advice would confuse our original poster, and place his amp and himself at some risk. Alright. Google "buck transformer" or something like that. I vote for this as well -- it's a permanent solution. Tim -- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @ http://webpages.charter.net/dawill/tmoranwms |
#8
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"Tim Williams" wrote in message ... "Patrick Turner" wrote in message ... I seriously think you advice would confuse our original poster, and place his amp and himself at some risk. Alright. Google "buck transformer" or something like that. I vote for this as well -- it's a permanent solution. Tim Yup it works great the other way to bring newer mains voltage down to the level of antique guitar amps spec too. Doug |
#10
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"I seriously think you advice would confuse our original poster,
and place his amp and himself at some risk." Why? |
#11
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Krzysiek Slychan wrote: "I seriously think you advice would confuse our original poster, and place his amp and himself at some risk." Why? Anyone farnarkling around with mains voltage without considerable experience is likely to perhaps electrocute themselves or burn something in the amp. The fact that the original poster asked the question he did indicates his knowledge/experience isn't high. If there is no obvious way to voltage match from 120v to 100v, say by rotating some voltage preset switch on the back of the amp, then I assume that option is closed, so I thought it better to advise some stranger of the simplest and easiest and SAFEST way to achieve a wanted end result, and without the possibility of the variac being turned up to too high a voltage by accident, and not have that noticed by anyone. Patrick Turner. |
#12
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As the original poster I would have to agree with Patrick. I ended up buying
a 500 watt step down/up transformer. I just hope it doesn't introduce noise that is audible in my little tube amp. "Patrick Turner" wrote in message ... Krzysiek Slychan wrote: "I seriously think you advice would confuse our original poster, and place his amp and himself at some risk." Why? Anyone farnarkling around with mains voltage without considerable experience is likely to perhaps electrocute themselves or burn something in the amp. The fact that the original poster asked the question he did indicates his knowledge/experience isn't high. If there is no obvious way to voltage match from 120v to 100v, say by rotating some voltage preset switch on the back of the amp, then I assume that option is closed, so I thought it better to advise some stranger of the simplest and easiest and SAFEST way to achieve a wanted end result, and without the possibility of the variac being turned up to too high a voltage by accident, and not have that noticed by anyone. Patrick Turner. |
#13
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"Trader" said:
As the original poster I would have to agree with Patrick. I ended up buying a 500 watt step down/up transformer. I just hope it doesn't introduce noise that is audible in my little tube amp. Just put it away far enough. I'd say about half a meter or so would be enough. -- Sander deWaal "SOA of a KT88? Sufficient." |
#14
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Hi K & P,
As an Master Electrician of some 28 years I would have to agree with Patrick on this. There's something counterintuitve about connecting the secondary of a transformer in series with the primary and I still have to study a diagram. I see nothing wrong with a properly sized/fused Variac, perhaps somehow locked/restricted to the correct setting. That's how I'd do it and I are an Electrician. After all... - Nothing is so Smiple That You Can't Screw it Up. keithw... PS: For those of you that would like to see a small tutorial on the subject refer to http://www.solaheviduty.com/products...t/bbeconns.pdf H1-4 is the primary of the transformer and X1-4 is the "UNKNOWN" secondary. SO for 120volt primary H1 & H3 would tie together and H2 & H4 would tie together and primary voltage would be applied to H1 & H2. For 240volt primary H2 & H3 would tie together and primary voltage would be applied to H1 & H4. Basically connecting the "Two 120 Volt Coils" in parallel or series. Same applies to the secondary of the transformer "Patrick Turner" wrote in message ... "Krzysiek Słychań" wrote: Do you have 115 or 230V mains voltage? If you have 115V, you can use a 115/ 15V power transformer with a primary winding connected to mains and a secondary winding connected in series in counterphase (so that the voltage that feeds the amp would be 115V-15V=100V) with the amp power iron's primary. A nice method of stepping voltage down Oh, and the 15V winding should be rated at least at approx. 1,5A (or more). I seriously think you advice would confuse our original poster, and place his amp and himself at some risk. Patrick Turner. |
#16
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Trader wrote: As the original poster I would have to agree with Patrick. I ended up buying a 500 watt step down/up transformer. I just hope it doesn't introduce noise that is audible in my little tube amp. It definately won't make things noisy. If anything, the amp should be further isolated from the mains and be quieter. And noise or hum heard will be due to an existing problem in the power supply, or an earth loop from some other gear. Patrick Turner. "Patrick Turner" wrote in message ... Krzysiek Slychan wrote: "I seriously think you advice would confuse our original poster, and place his amp and himself at some risk." Why? Anyone farnarkling around with mains voltage without considerable experience is likely to perhaps electrocute themselves or burn something in the amp. The fact that the original poster asked the question he did indicates his knowledge/experience isn't high. If there is no obvious way to voltage match from 120v to 100v, say by rotating some voltage preset switch on the back of the amp, then I assume that option is closed, so I thought it better to advise some stranger of the simplest and easiest and SAFEST way to achieve a wanted end result, and without the possibility of the variac being turned up to too high a voltage by accident, and not have that noticed by anyone. Patrick Turner. |
#17
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Hi Jon,
Sometimes an amp connected to a variac sounds like crap. I would second this, but would underline the word "sometimes". The most noticable improvement when going from variac to normal mains was with a Klein+Hummel VS-55 amp (6BM8 PP) I had to restore, which sounded like crap at the variac, but got much better when directly connected to mains. Other amps (some with much higher power requirements than the VS-55 mentioned above) showed no or only hard-to-reproduce differences in sound w/ or w/o the (same) variac. I don't have an explanation, either. Tom -- A gleekzorp without a tornpee is like a quap without a fertsneet (sort of). |