left or right or left...where is the power test screwdriver...arghhh
Well, as the Neon itself is not a current device and it only senses voltage, I think that this arrangement would not compromise any earth leakage device.
Typical high sensitive residual current circuit breakers in-house are in the 6-30mA range while the neon is merely using ~2mA, so no tripping the RCD...
This is how I solved the problem here (as we don't really know where it's live or neutral, particularly on older installations and if one uses an extension cord..., don't know if it is legal though?!
would like to know further more...
thanks
Well, as the Neon itself is not a current device and it only senses voltage, I think that this arrangement would not compromise any earth leakage device.
Typical high sensitive residual current circuit breakers in-house are in the 6-30mA range while the neon is merely using ~2mA, so no tripping the RCD...
This is how I solved the problem here (as we don't really know where it's live or neutral, particularly on older installations and if one uses an extension cord..., don't know if it is legal though?!
would like to know further more...
thanks
To lift the audio ground from PE. A variant of the resistor that lifts small signal from power ground. The purpose is to suppress hum in the case of a ground loop.
Cheers, I have been reading quite a few articles from that site and some of the information is very easy to follow. Some of it gets a bit too techo for a mug like me though!
Previously, I had what seemed to be a substantial amount of hum in my new beastie, but I replaced some of the thinner grounding wires with heavier ones; also inserted the resistor. This has tidied things up quite a bit now and the amp sounds beautiful with the exception of a small residual that becomes evident in-between tracks of any cd. This hum seems to dissappear to some extent when the amp warms up - after about 15 minutes at around 1/4 volume.
Previously, I had what seemed to be a substantial amount of hum in my new beastie, but I replaced some of the thinner grounding wires with heavier ones; also inserted the resistor. This has tidied things up quite a bit now and the amp sounds beautiful with the exception of a small residual that becomes evident in-between tracks of any cd. This hum seems to dissappear to some extent when the amp warms up - after about 15 minutes at around 1/4 volume.
- My next amp will have all componentry on the one board.
- Will only have one Transformer.
- Will have larger gnd tracks.
- Will have the drivers and any bias vbe multipliers mounted double-decker style on top of the output power devices.
- Alternatively bias diodes will be epoxied to the case of the output devices. Or some TO-220 diodes may be used 'double-decker' style.
Hello im newbie in DIY world
I have my 2nd project... Gainclone lm1875
I wanna build 2 amp, with 2 psu, and 2 transformer, but with 1 chassis.
I want to make dual input ( 4pc rca ) and the output are 4 binding post..
Can someone help me to draw the schematic for my ground ?? Or show me the link to answer my problem...
I wanna say thank you first.... And merry christmas too
I have my 2nd project... Gainclone lm1875
I wanna build 2 amp, with 2 psu, and 2 transformer, but with 1 chassis.
I want to make dual input ( 4pc rca ) and the output are 4 binding post..
Can someone help me to draw the schematic for my ground ?? Or show me the link to answer my problem...
I wanna say thank you first.... And merry christmas too
Star grounding your new amp.
Hi there O'Dr. The LM1875 is a great amp. My favourite of the 'all-in-one' TO-220s.
Can I just offer some of my limited experience as an effort to help you find the correct answer? Here it is:
If you can avoid multiple boards do so in order to simplify the task.
Building an amp is achievable with some good planning and a lot of enthusiasm, but always try to find the simplest way to do things.
If you are buying a pair of assembled or kit boards, off the internet, then fine, this will save a great deal of stress, but there is no need to build two power supplies and have two transformers - unless, like me, you already hve two small transformers in your junk box - ex salvage or from the local tip (be carefull with high voltage - get electrician if in doubt).
In my opinion you should avoid using two transformers in this situation because the demand on the transformer is not so big, when you build a stereo from a pair of lm1875's.
Dont worry about expensive toroidal transformers unless you can afford the luxury - they are only marginally better for this type of job.
Any cheap ($25) transformer will do the job, it can be a centre tap or have dual secondary windings (with a little bit of extra work you could use a single secondary as well, but I wouldn't worry about doing that). Voltage should be between 9AC to 18AC, that is [9-0-9], [0-9 + 0-9] right up to [18-0-18], [0-18 + 0-18]
If you use a 9v winding then a 1A secondary will be adequate but as the voltage rises so too will the demand for current which will be as high as 2A for the maximum LM1875 power output of 30W into an 8 Ohm speaker.
So therefore an 18V CT of 30VA will suffice for a 10W/CH/8R and a 36V CT of 70VA will get the little chips running at their maximum output of 30W/CH/8R. The latter will need a good heat sink because the chips will be running relatively hot.
Here is a link to the star grounding issues.
http://www.diyaudio.com/forums/power-supplies/115698-understanding-star-grounding.html
I wish you all the best with your amp and don't be afraid to ask lots more questions if you are unsure. BTW you only need two 3300uF/35V caps for each rail of the 18-0-18 option (four caps total). You could save further capacitance in the 9-0-9 version ie two 1000uF/16V per rail (4 total).
You mentioned four rca's on the input did you mean two rca's (stereo) each rca carries it's own ground from the cd to the amp. I may have mis-understood you, so dont be afraid to get back with more questions.
Merry Christmas Bloke.
Hi there O'Dr. The LM1875 is a great amp. My favourite of the 'all-in-one' TO-220s.
Can I just offer some of my limited experience as an effort to help you find the correct answer? Here it is:
If you can avoid multiple boards do so in order to simplify the task.
Building an amp is achievable with some good planning and a lot of enthusiasm, but always try to find the simplest way to do things.
If you are buying a pair of assembled or kit boards, off the internet, then fine, this will save a great deal of stress, but there is no need to build two power supplies and have two transformers - unless, like me, you already hve two small transformers in your junk box - ex salvage or from the local tip (be carefull with high voltage - get electrician if in doubt).
In my opinion you should avoid using two transformers in this situation because the demand on the transformer is not so big, when you build a stereo from a pair of lm1875's.
Dont worry about expensive toroidal transformers unless you can afford the luxury - they are only marginally better for this type of job.
Any cheap ($25) transformer will do the job, it can be a centre tap or have dual secondary windings (with a little bit of extra work you could use a single secondary as well, but I wouldn't worry about doing that). Voltage should be between 9AC to 18AC, that is [9-0-9], [0-9 + 0-9] right up to [18-0-18], [0-18 + 0-18]
If you use a 9v winding then a 1A secondary will be adequate but as the voltage rises so too will the demand for current which will be as high as 2A for the maximum LM1875 power output of 30W into an 8 Ohm speaker.
So therefore an 18V CT of 30VA will suffice for a 10W/CH/8R and a 36V CT of 70VA will get the little chips running at their maximum output of 30W/CH/8R. The latter will need a good heat sink because the chips will be running relatively hot.
Here is a link to the star grounding issues.
http://www.diyaudio.com/forums/power-supplies/115698-understanding-star-grounding.html
I wish you all the best with your amp and don't be afraid to ask lots more questions if you are unsure. BTW you only need two 3300uF/35V caps for each rail of the 18-0-18 option (four caps total). You could save further capacitance in the 9-0-9 version ie two 1000uF/16V per rail (4 total).
You mentioned four rca's on the input did you mean two rca's (stereo) each rca carries it's own ground from the cd to the amp. I may have mis-understood you, so dont be afraid to get back with more questions.
Merry Christmas Bloke.
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hi there tripmaster...
thank u for answering my question
i already bought toroidal transformer 160va 2x18v
four rca, in my mind would be ( 2pc for my CDP, 2 othe pc for my ipod ) maybe i wanna make some audio switcher with rotary switch...
i was planning for using potentio as well, and already have 50k pot....
and i was planning for making 2 different output, 4 binding post for my speaker, and 1 headphone jack...
wow a lot of mind LoL....
i was reading this thread... but there are many different theory... i dont know which one i should take...
thank u for answering my question
i already bought toroidal transformer 160va 2x18v
four rca, in my mind would be ( 2pc for my CDP, 2 othe pc for my ipod ) maybe i wanna make some audio switcher with rotary switch...
i was planning for using potentio as well, and already have 50k pot....
and i was planning for making 2 different output, 4 binding post for my speaker, and 1 headphone jack...
wow a lot of mind LoL....
i was reading this thread... but there are many different theory... i dont know which one i should take...
Do not use a chassis at this first build stage.
Be very aware that without the chassis, there is nowhere to connect the Safety Earth.
No pets, no children, no nagging wife in the same room.
Build up one channel complete from input RCA to Output speaker terminals.
Find out if your single channel is hum free and buzz free. Thoroughly check it.
When you are happy that it is perfect, build up your second channel and place it alongside.
It too should be perfect.
Now couple the Main Audio Grounds on each of the two parallel assemblies.
Check for hum and buzz. Attach first one channel of source to either input. Then to the other input. Then two source channels to both inputs. Is it still completely hum free and buzz free?
When you successfully get to this two channel hum free state, you are ready to start visualising how to package the perfect amplifiers into a single chassis.
Electrically everything must remain identical.
Physically (magnetic radiation) the "in chassis assembly" will be very different. But, because the electrical side is identical, you will know that any introduced hum or buzz can only be due to magnetic radiation from and to "loops" in the circuits.
Be very aware that without the chassis, there is nowhere to connect the Safety Earth.
No pets, no children, no nagging wife in the same room.
Build up one channel complete from input RCA to Output speaker terminals.
Find out if your single channel is hum free and buzz free. Thoroughly check it.
When you are happy that it is perfect, build up your second channel and place it alongside.
It too should be perfect.
Now couple the Main Audio Grounds on each of the two parallel assemblies.
Check for hum and buzz. Attach first one channel of source to either input. Then to the other input. Then two source channels to both inputs. Is it still completely hum free and buzz free?
When you successfully get to this two channel hum free state, you are ready to start visualising how to package the perfect amplifiers into a single chassis.
Electrically everything must remain identical.
Physically (magnetic radiation) the "in chassis assembly" will be very different. But, because the electrical side is identical, you will know that any introduced hum or buzz can only be due to magnetic radiation from and to "loops" in the circuits.
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160VA Excellent
Don't be sad about that transformer Overdreamer, it is an excellent choice! You will be able to build a heavier duty supply that can be used in many other circuits at a later date. 18 volts is a very versatile supply and can be used for many A-Class or B-Class designs that are out there in circuit form on the internet.
When you build your power supply, you might pop a pair of 10 000uF (10mF) caps on each rail, 4 total, then you can use that supply for almost any purpose at a later date. 35V capacitors are fine but I have found that it is actually better to buy the 63V ones from Hong Kong, four will cost you $12 Australian delivered to your door within a week I would guess. Dont know what that $12 equals in your currency but it will be cheaper than the 35V caps. Do a search on ebay, they are the Rubycon branded ones and they are excellent value for money.
Cheers and bye for now.
Regarding the four inputs yes this is all good and you will use perhaps a double pole double throw (on-on) switch on the front of the amp marked CD/IPOD or whatever the inputs might be.
hi there tripmaster...
thank u for answering my question
i already bought toroidal transformer 160va 2x18v
...
Don't be sad about that transformer Overdreamer
, it is an excellent choice! You will be able to build a heavier duty supply that can be used in many other circuits at a later date. 18 volts is a very versatile supply and can be used for many A-Class or B-Class designs that are out there in circuit form on the internet.When you build your power supply, you might pop a pair of 10 000uF (10mF) caps on each rail, 4 total, then you can use that supply for almost any purpose at a later date. 35V capacitors are fine but I have found that it is actually better to buy the 63V ones from Hong Kong, four will cost you $12 Australian delivered to your door within a week I would guess. Dont know what that $12 equals in your currency but it will be cheaper than the 35V caps. Do a search on ebay, they are the Rubycon branded ones and they are excellent value for money.
Cheers and bye for now.
Regarding the four inputs yes this is all good and you will use perhaps a double pole double throw (on-on) switch on the front of the amp marked CD/IPOD or whatever the inputs might be.
Hi! farmerjack 61,
I have a Transformer with a 12-0-12 / 3 Ampere, rating (centre tapped). Can i use it to build the stereo amplifier, using LM1875? Offcourse two LM1875 will be used and What will be the power for each channel? I want this transformer to be used up to 2.5 Ampere maximum on the safer side becoz, I will be using a fuse of about 2.8Ampere.
Should i use a split rail power supply or a single rail power supply?
Split rail will be around +13 0 -13,(26volts in total approx.), if and when regulated.
Whereas, Single rail supply will be +13 volts only, after regulation.
Which one is better? split rail or single rail supply? Which one gives the good performance and sound quality to LM1875?
Speakers will be 8ohm impedance, each for left and right channels.
Please, help me. All suggestions are welcome, Thanks.
I have a Transformer with a 12-0-12 / 3 Ampere, rating (centre tapped). Can i use it to build the stereo amplifier, using LM1875? Offcourse two LM1875 will be used and What will be the power for each channel? I want this transformer to be used up to 2.5 Ampere maximum on the safer side becoz, I will be using a fuse of about 2.8Ampere.
Should i use a split rail power supply or a single rail power supply?
Split rail will be around +13 0 -13,(26volts in total approx.), if and when regulated.
Whereas, Single rail supply will be +13 volts only, after regulation.
Which one is better? split rail or single rail supply? Which one gives the good performance and sound quality to LM1875?
Speakers will be 8ohm impedance, each for left and right channels.
Please, help me. All suggestions are welcome, Thanks.
Solved. I want to thank you Zang, for all of your effort in explaining the difference. You have gone to a lot of trouble and the pictures are a great help. My amp sounds wonderful now & I think, just-as-good as my mate's Rotel, which was the benchmark for me. I am a Wood-Machinist & Joiner by trade so this amp is a source of great pride for me, and I could not have done it without the help I have received here at DIY.
Cheers my friend.
Cheers my friend.
lm1875
Hi there Noddy.
* I personally use a dual rail p.s. As to which is better I am unsure if there is any difference at all - but you can go either way with your transformer because it has a 24volt secondary - 12+12=24 so If you want to try the single rail supply - go for it, just insulate the centre-tap and leave it out. Then you will have a 70va 0-24v transformer still with 3 amps out.
* The sound quality is just as good or better at the lower voltage due to the lower temperatures inside the chip. To understand the voltage demands just look at the schematic for the chip you use. In this case the signal passes through two silicon junctions each has a voltage drop of .7v so once the signal exceeds 1.4v you will have an output at the speaker.
*I guess that the power output (for 12-0-12) will be about 10-15W into an 8 Ohm spkr.
* Fuses; For your 70VA transformer, I would start with a 500mA slow blow on the primary, and a F2A on each rail. Remember that a fuse only blows after an hour if the current through it equals it's rating. Fuses are a last ditch attempt to stop a fire inside your house.
*Insulate all mains wiring and get a sparky to check it before you switch it on. This is very important as the mains voltages can be lethal.
*"Sound Quality V Rail Voltage" I recently repaired a 5:1 surround sound system powered by 12-0-12, 25VA transformer. it was designed for 16 Ohm speakers and sounded pretty fair before one of the rectifier diodes blew and cosequently the transformer secondary. I had no 12-0-12 replacement on hand and my mate wanted his amp back... so I decided to pop a 9-0-9, 18VA into the 'hole' and it sounded exactly the same as the previous arrangement. The only difference that we could pick was a small decrease in bass response, which wasn't huge to start with.
*Filters; At this stage I wouldn't worry too much about bass and treble filters. Let's leave that for another day - Or may-be you could get one of those cheap Chinese preamp boards, they do seem to be very well built and then you only have to insert it between the rca's and the amp input.
Good luck with your project and dont be put off by all the technical stuff.
Adios amigo
Hi there Noddy.
* I personally use a dual rail p.s. As to which is better I am unsure if there is any difference at all - but you can go either way with your transformer because it has a 24volt secondary - 12+12=24 so If you want to try the single rail supply - go for it, just insulate the centre-tap and leave it out. Then you will have a 70va 0-24v transformer still with 3 amps out.
* The sound quality is just as good or better at the lower voltage due to the lower temperatures inside the chip. To understand the voltage demands just look at the schematic for the chip you use. In this case the signal passes through two silicon junctions each has a voltage drop of .7v so once the signal exceeds 1.4v you will have an output at the speaker.
*I guess that the power output (for 12-0-12) will be about 10-15W into an 8 Ohm spkr.
* Fuses; For your 70VA transformer, I would start with a 500mA slow blow on the primary, and a F2A on each rail. Remember that a fuse only blows after an hour if the current through it equals it's rating. Fuses are a last ditch attempt to stop a fire inside your house.
*Insulate all mains wiring and get a sparky to check it before you switch it on. This is very important as the mains voltages can be lethal.
*"Sound Quality V Rail Voltage" I recently repaired a 5:1 surround sound system powered by 12-0-12, 25VA transformer. it was designed for 16 Ohm speakers and sounded pretty fair before one of the rectifier diodes blew and cosequently the transformer secondary. I had no 12-0-12 replacement on hand and my mate wanted his amp back... so I decided to pop a 9-0-9, 18VA into the 'hole' and it sounded exactly the same as the previous arrangement. The only difference that we could pick was a small decrease in bass response, which wasn't huge to start with.
*Filters; At this stage I wouldn't worry too much about bass and treble filters. Let's leave that for another day - Or may-be you could get one of those cheap Chinese preamp boards, they do seem to be very well built and then you only have to insert it between the rca's and the amp input.
Good luck with your project and dont be put off by all the technical stuff.
Adios amigo
Yes.
Depends on the speaker impedance and how much capacitance your power supply has. Something like 12 W into 8 Ohm.
You will not be able to control that.
If the transformer is rated for 3 A, you can use a 3 A slow-blow fuse on the secondary side. You don't gain any safety by using a smaller fuse.
Use a split supply. You save on the virtual ground circuit and the output capacitor.
If you regulate it down to 13 V, you will only get 7-8 W into 8 Ohm, instead of 12 W. The regulators will produce a lot of extra heat, extra consumption, and they will increase the cost, size and complexity of the project.
No, you would skip the center tap, so your transformer will have 1x24 V instead of 2x12 V and the regulated voltage could be 26 V, too.
Split supply is better, but the difference is not that big. You basically add a big capacitor to the signal path, and that can or cannot have an influence on the sonic signature.
LM1875
Datasheet specifies +25 to -25 Volts, which is equivalent to 50Volts for LM1875 for Max. power. The rating of the transformer should be 60VA for single chip and 80VA for two chips(as according to the K50 Kit for LM1875).
Please let me know this:
a). What is the ideal voltage in split rail for LM1875 for the best possible sound quality?
b). I want to build two parallel LM1875 configurations in stereo mode. This means, i will be using four LM1875 chips. Please, tell me what should be the Maximum rating of my transformer?
Will it be a 160VA rating transformer? How much maximum current (Ampere) capable should the transformer be for four LM1875 chips in Parallel stereo build, voltage being an 18-0-18 (36) volt max.? I am ready to buy a new transformer, for this.
c). Transformers with 0-18 or 18-0-18 volts Maximum are easily available here. Above this voltage, it is hard to get the transformer, here.
Datasheet specifies +25 to -25 Volts, which is equivalent to 50Volts for LM1875 for Max. power. The rating of the transformer should be 60VA for single chip and 80VA for two chips(as according to the K50 Kit for LM1875).
Please let me know this:
a). What is the ideal voltage in split rail for LM1875 for the best possible sound quality?
b). I want to build two parallel LM1875 configurations in stereo mode. This means, i will be using four LM1875 chips. Please, tell me what should be the Maximum rating of my transformer?
Will it be a 160VA rating transformer? How much maximum current (Ampere) capable should the transformer be for four LM1875 chips in Parallel stereo build, voltage being an 18-0-18 (36) volt max.? I am ready to buy a new transformer, for this.
c). Transformers with 0-18 or 18-0-18 volts Maximum are easily available here. Above this voltage, it is hard to get the transformer, here.