Step down transformer for stereo amplifier

Rega Amplifiers
1. The RX-V795a specs indicate (Max) power consumption of 690 Watts.

Hence your 240V to 120 Volt Transformer should be capable of delivering atleast 690 Watts at 120 Volts

This amounts to 5.75 amperes current at 120 Volts. So 6 Ampere 120 Volt transformer would be fine.


2. Page 25 of the User Manual indicates that the China & general Models have a Voltage selector for 120 VAC & 240 VAC Operation. Check it out on the unit you have. Then you do not need to get an external transfo. Simply change the Voltage selector to 240 VAC operation
 
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vmscbe1974 said:
Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers . Three questions :
1. Brand to be used for the amplifier in India
2. What KVA rating of step down transformer should be used when it’s mentioned as 140 watts on the rear panel of the amplifier
3. Is it wise enough to buy the step down transformer generating no hum in speakers or let go of this amplifier and look out for Indian wattage adaptability.
A confused member .
regards
Srinivasan
Click to expand...
Regarding your requirement, you should opt for an non humming Aulten step down transformer, I am using the same for past 3 months, no issues at all,
I would advise you to check on back side of your amp for compatible voltage transformer, you can share a picture of back of the amp with Aulten executive on Whatsapp @ 9811597709
Trust me it's worth every penny and quality product.
I hope this helps,
Regards
 
Something everyone missed. What is the frequency rating of your AV gear. Is it 50/60Hz or 60Hz? If latter, a simple step down will not help. You need to factor in the ratio of frequency also 50/60 to avoid burn out of your internal trafos.
 
In principle, you are correct, Subbu68. However, in practice, particularly for audio Power Amps, the situation is more forgiving than a pure theoretical look.

a 50Hz transformer is designed with more 'Iron" (core laminations) than a 60 Hz transformer. So a 50 Hz Transformer will work fine at 60 Hz.

However, since a 60 Hz (usually 110 Volt countries) transformer has less core iron, the core will tend to saturate (overload) if operated sustained, at close to Full Load. At less than 80% sustained load there is little concern.

For most of its regular life, an audio power amplifier is usually operated well below 50% of its full power rating (closer to 10% to 25%), on a sustained basis. Full power is delivered for probably less than 1% of its operation.

A 60 Hz designed Power transformer will operate comfortably, and reliably, long term, under these conditions, at 50 Hz.


Interestingly, even today, Japan operates at 50 Hz & 60 Hz simultaneously!
All of Japan runs on the same voltage, however the frequency differs from region to region!

Eastern Japan (including Tokyo), uses 50Hz after purchasing electrical generators from the German company AEG in 1895.

A year later, American company General Electric, provided 60Hz generators for cities in western Japan (including cities such as Osaka and Kyoto).
 
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reubensm said:
rewinding, if attempted, must be done professionally, i have come across quite a few rewound trannies that produce a gentle hum

By far the best rewinding job which i have come across is with one of our FM's amplifier's toroidal tranny. The job done was exactly like the original. I think he got it done somewhere in Pune. I checked the specs of the rewound tranny with the original NAD tranny and they were a perfect match. The tranny was also dead silent.
Click to expand...
The pune rewinding “may” have been done by Torotrans. Its just a guess as they make excellent toroids. Have used them. They dont usually do rewinding and only manufacture but “ may” have done so as a favour.

Manek

IndianEars said:
In principle, you are correct, Subbu68. However, in practice, particularly for audio Power Amps, the situation is more forgiving than a pure theoretical look.

a 50Hz transformer is designed with more 'Iron" (core laminations) than a 60 Hz transformer. So a 50 Hz Transformer will work fine at 60 Hz.

However, since a 60 Hz (usually 110 Volt countries) transformer has less core iron, the core will tend to saturate (overload) if operated sustained, at close to Full Load. At less than 80% sustained load there is little concern.

For most of its regular life, an audio power amplifier is usually operated well below 50% of its full power rating (closer to 10% to 25%), on a sustained basis. Full power is delivered for probably less than 1% of its operation.

A 60 Hz designed Power transformer will operate comfortably, and reliably, long term, under these conditions, at 50 Hz.


Interestingly, even today, Japan operates at 50 Hz & 60 Hz simultaneously!
All of Japan runs on the same voltage, however the frequency differs from region to region!

Eastern Japan (including Tokyo), uses 50Hz after purchasing electrical generators from the German company AEG in 1895.

A year later, American company General Electric, provided 60Hz generators for cities in western Japan (including cities such as Osaka and Kyoto).
Click to expand...
Thats news to me and thats weird to. But this was the scene in 1895. Surely things should have been standardised over time ?
 
The 2 Grids - 60 Hz & 50 Hz cannot be directly connected, so power from 1 grid cannot be shared with the other.

Japan interconnects the 2 Grids via a HVDC (High Voltage DC ) interconnection! The AC from each Grid is converted to High Voltage DC and the DC shared. The DC has to be reconverted to the required 50 Hz or 60 Hz before being fed to the other grid. This is done with Electronics, but obviously can be done for only a limited electrical capacity ....

REALLY bad legacy problem !:eek:
 
IndianEars said:
The 2 Grids - 60 Hz & 50 Hz cannot be directly connected, so power from 1 grid cannot be shared with the other.

Japan interconnects the 2 Grids via a HVDC (High Voltage DC ) interconnection! The AC from each Grid is converted to High Voltage DC and the DC shared. The DC has to be reconverted to the required 50 Hz or 60 Hz before being fed to the other grid. This is done with Electr onics, but obviously can be done for only a limited electrical capacity ....

REALLY bad legacy problem !:eek:
Click to expand...
That's how Saudi connects to rest of Gulf grid (GCC). We operate at 50Hz in UAE, Qatar, Bahrain, Kuwait, Oman while Saudi is 60Hz. They convert to DC and then 50Hz AC
 
Subbu68 said:
That's how Saudi connects to rest of Gulf grid (GCC). We operate at 50Hz in UAE, Qatar, Bahrain, Kuwait, Oman while Saudi is 60Hz. They convert to DC and then 50Hz AC
Click to expand...
OMG. How do they convert mega watts to DC? I was thinking about it and wonder if it is through a AC motor connected to a DC generator? Or is there some other way. Can't imagine using diodes/rectifiers to operate at such high amperage
 
mbhangui said:
OMG. How do they convert mega watts to DC? I was thinking about it and wonder if it is through a AC motor connected to a DC generator? Or is there some other way. Can't imagine using diodes/rectifiers to operate at such high amperage
Click to expand...
Converter stations. That is behind HVDC transmission. You have these in India - like in Chandrapur. I think it links Chandrapur to Paghde. Similar more links are in India. They use thyristor valves
 
IndianEars said:
In principle, you are correct, Subbu68. However, in practice, particularly for audio Power Amps, the situation is more forgiving than a pure theoretical look.

a 50Hz transformer is designed with more 'Iron" (core laminations) than a 60 Hz transformer. So a 50 Hz Transformer will work fine at 60 Hz.

However, since a 60 Hz (usually 110 Volt countries) transformer has less core iron, the core will tend to saturate (overload) if operated sustained, at close to Full Load. At less than 80% sustained load there is little concern.

For most of its regular life, an audio power amplifier is usually operated well below 50% of its full power rating (closer to 10% to 25%), on a sustained basis. Full power is delivered for probably less than 1% of its operation.

A 60 Hz designed Power transformer will operate comfortably, and reliably, long term, under these conditions, at 50 Hz.


Interestingly, even today, Japan operates at 50 Hz & 60 Hz simultaneously!
All of Japan runs on the same voltage, however the frequency differs from region to region!

Eastern Japan (including Tokyo), uses 50Hz after purchasing electrical generators from the German company AEG in 1895.

A year later, American company General Electric, provided 60Hz generators for cities in western Japan (including cities such as Osaka and Kyoto).
Click to expand...
It is the higher magnetizing current at lower frequency that could cause the overheating and burnout. So even without load the heating continues. Iron loss is not dependent on load. And the associated no load copper loss. There may be some overload factor it in the design that may be holding out.

I was planning a F5 amp project and a major chunk of the cost I found was for the power supply. I think the same applies to commercial amps and receivers. Considering the number of units they sell in USA compared to other parts, would these manufacturers be size the transformers generously? Every gm of copper for the winging and core material multiplied by the units sold would be a good saving ;)
 
vmscbe1974 said:
Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers . Three questions :
1. Brand to be used for the amplifier in India
2. What KVA rating of step down transformer should be used when it’s mentioned as 140 watts on the rear panel of the amplifier
3. Is it wise enough to buy the step down transformer generating no hum in speakers or let go of this amplifier and look out for Indian wattage adaptability.
A confused member .
regards
Srinivasan
Click to expand...
Srini If you had already bought an amplifier then there is nothing wrong in investing in a good step down transformer. I had used step down transformer in the past to use 110v and 100v version amplifier. I have Maxine 2kv transformer and it supports 110v and 100v and using it for the last 10years and absolutely no issues.
 
IndianEars said:
The 2 Grids - 60 Hz & 50 Hz cannot be directly connected, so power from 1 grid cannot be shared with the other.

Japan interconnects the 2 Grids via a HVDC (High Voltage DC ) interconnection! The AC from each Grid is converted to High Voltage DC and the DC shared. The DC has to be reconverted to the required 50 Hz or 60 Hz before being fed to the other grid. This is done with Electronics, but obviously can be done for only a limited electrical capacity ....

REALLY bad legacy problem !:eek:
Click to expand...
And conversion losses ? What % could we put that number down to ?
 
Mumbai trains was conversion from DC to AC traction...

Rather different from the 50 Hz to 60 Hz AC to AC conversion in Japan for grid to grid interconnection.
 
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