OK.
Im a newbie / beginner; that`s true.
This is not my thread - that is why I wanted to ask you in a PM,
..... I will try to tread carefully ....
I found this other thread where you are concerned with safety in DIY projects.
I then wanted to ask you the following in a PM ( I thought you were the right man to ask )
Ref: post 43 :
link : http://www.diyaudio.com/forums/power-supplies/115698-understanding-star-grounding-5.html
1. I`m planning on using this Mains Entry Module with a 10A current rating.
4304.6090 Schurter | Mouser
The 10A current rating in the spec sheet of this unit is maximum handling?
I can install a 2A fuse in this exact Mains Entry Module - right?
I have asked the same question to the Toroidy company.
2. So you are using soft starters on all toroids that has a nominal power equal or above 100 VA. I guess you are then recommending me using the same for my 400 VA toroidy transformer, then?
3. Do you use / or have used soft starters from Toroidy?
4. Do you recommend me to use lower A in the fuse installed - You stated this a previous answer to one of my questions - why?
Im a newbie / beginner; that`s true.
This is not my thread - that is why I wanted to ask you in a PM,
..... I will try to tread carefully ....
I found this other thread where you are concerned with safety in DIY projects.
I then wanted to ask you the following in a PM ( I thought you were the right man to ask )
Ref: post 43 :
link : http://www.diyaudio.com/forums/power-supplies/115698-understanding-star-grounding-5.html
1. I`m planning on using this Mains Entry Module with a 10A current rating.
4304.6090 Schurter | Mouser
The 10A current rating in the spec sheet of this unit is maximum handling?
I can install a 2A fuse in this exact Mains Entry Module - right?
I have asked the same question to the Toroidy company.
2. So you are using soft starters on all toroids that has a nominal power equal or above 100 VA. I guess you are then recommending me using the same for my 400 VA toroidy transformer, then?
3. Do you use / or have used soft starters from Toroidy?
4. Do you recommend me to use lower A in the fuse installed - You stated this a previous answer to one of my questions - why?
Hello Endre,
How did you make your choice for the Toroidy? I saw they are from Poland. Do they have a good reputation? I could not find a webshop from them. What price is yours? Order directly form their company?
I was planning to use an Amplimo 300VA 2x22V for around 73 Euros, which I thought was a good reputable source for toroids but I am a newbe and really don't have a clue as to what is a good transformer. I am living in the Netherlands, but plan to move to beautiful Norway in the near future by the way...
Any suggestions from you guys? What makes a good transformer?
Frederick Joan
How did you make your choice for the Toroidy? I saw they are from Poland. Do they have a good reputation? I could not find a webshop from them. What price is yours? Order directly form their company?
I was planning to use an Amplimo 300VA 2x22V for around 73 Euros, which I thought was a good reputable source for toroids but I am a newbe and really don't have a clue as to what is a good transformer. I am living in the Netherlands, but plan to move to beautiful Norway in the near future by the way...
Any suggestions from you guys? What makes a good transformer?
Frederick Joan
My choice regarding the Toroidy transformers :
Recommendation from Peter.
Webpage:
Aktualno?ci - TOROIDY.PL Transformatory Toroidalne Producent, Audio, Separacyjne, Trójfazowe, 230/110V, 110/230V, Na zamówienie
Did get the price through email correspondence.
First I was recommended this unit:
( since I was planning on using an amplifier with dual mono supply - like you are now )
Specs:
230 mains
300 VA nominal power ( max power ?! )
2x25 V output ( since I´m using 16ohm speakers , not 8 ohm: then it would be 2x22 V.
Price:
63,50 Euro each
33 Euro - shipping to Norway
This setup was meant to have two separate chassis. I already have the exact pair of the modu shop chassis you found on net.
One for the power supply ---- with umbilical chord ------ One for the LM3875 amplifier.
I´ve been wiggling back and forth on this.
( see previous posts )
But I landed on using one transformer.
With these Specs:
230V mains
400VA
2x25V output
Price:
71,00 Euro each
33,00 Euro - shipping
Will send you a PM shortly ;-) I`m really crossing fingers that your inbox is not full....
PS: found this overview on diyaudio - this made things easier for me to understand - see attached GIF image.
Endre
Recommendation from Peter.
Webpage:
Aktualno?ci - TOROIDY.PL Transformatory Toroidalne Producent, Audio, Separacyjne, Trójfazowe, 230/110V, 110/230V, Na zamówienie
Did get the price through email correspondence.
First I was recommended this unit:
( since I was planning on using an amplifier with dual mono supply - like you are now )
Specs:
230 mains
300 VA nominal power ( max power ?! )
2x25 V output ( since I´m using 16ohm speakers , not 8 ohm: then it would be 2x22 V.
Price:
63,50 Euro each
33 Euro - shipping to Norway
This setup was meant to have two separate chassis. I already have the exact pair of the modu shop chassis you found on net.
One for the power supply ---- with umbilical chord ------ One for the LM3875 amplifier.
I´ve been wiggling back and forth on this.
( see previous posts )
But I landed on using one transformer.
With these Specs:
230V mains
400VA
2x25V output
Price:
71,00 Euro each
33,00 Euro - shipping
Will send you a PM shortly ;-) I`m really crossing fingers that your inbox is not full....
PS: found this overview on diyaudio - this made things easier for me to understand - see attached GIF image.
Endre
Attachments
I've been using Toroidy transformers myself, at the time when they were able to source amorphous core material: http://www.diyaudio.com/forums/audio-sector/76609-most-advanced-gainclone-amp-yet.html
The specs were as follow:
TS300VA PRI:115V SEC:2x22V w wykonaniu AUDIO z rdzeniem z taśmy izopermowej,
- uzwojenie wtórne przy rdzeniu,
- 50% większy przekrój drutu, drut pojedynczy,
Last two notes mean:
- secondary first, primary on the outside
- 50% higher gauge of secondary, single wire
The specs were as follow:
TS300VA PRI:115V SEC:2x22V w wykonaniu AUDIO z rdzeniem z taśmy izopermowej,
- uzwojenie wtórne przy rdzeniu,
- 50% większy przekrój drutu, drut pojedynczy,
Last two notes mean:
- secondary first, primary on the outside
- 50% higher gauge of secondary, single wire
Thanks Peter.
If I use a 400 V AC transformer ( without soft starter ) in my region; where 230V = Mains Voltage
- I will need to use a 2A or 2.5A slowburn fuse ( by the way also called Time Delayed Fuse; marked with a: T )
, as already described by you, and read by me many many times in your building guide. Thanks.
I will use a non-filtered Mains Entry Module as recommended.
The topic about Transformers / Mains Entry Modules / Soft Starters / Fuses is now a completed chapter for me in this thread.
If I use a 400 V AC transformer ( without soft starter ) in my region; where 230V = Mains Voltage
- I will need to use a 2A or 2.5A slowburn fuse ( by the way also called Time Delayed Fuse; marked with a: T )
, as already described by you, and read by me many many times in your building guide. Thanks.
I will use a non-filtered Mains Entry Module as recommended.
The topic about Transformers / Mains Entry Modules / Soft Starters / Fuses is now a completed chapter for me in this thread.
A 400VA transformer rated for 230Vac will require a T5A mains fuse.
I don't know how many cold starts Peter's 5A fuse on a <400VA 115Vac will survive.
A normal fuse for motors and transformers is roughly 3times the normal full load operating current.
A close rated fuse for your 400VA 230Vac would be around T1.6A, but this will require a soft start.
I don't know how many cold starts Peter's 5A fuse on a <400VA 115Vac will survive.
A normal fuse for motors and transformers is roughly 3times the normal full load operating current.
A close rated fuse for your 400VA 230Vac would be around T1.6A, but this will require a soft start.
Hi Peter,
Could you give me a hand with the calculation of the resistance R3 suitable for the LED which I would like to have? My goal is to have an LED
* in the frontpanel (10mm thick)
* round diameter appr. 3mm
* blue color
On digi-key I found one which seems suitable for me: VAOL-3LSBY1 Visual Communications Company - VCC | VAOL-3LSBY1-ND | DigiKey.
It is a VCC with Vf of 3,5V; max. 4.0V. I thought it would be easy for me with some high school formula's but I still don't get it when I try to recalculate the red LED in your manual.
Can you show me how to calculate?
I was thinking to drill a (stepped) hole in the front panel, isolate the leads with shrinking tube and connect to the PS board with a thin insulated wire. Is there something special I should consider? Should I glue it in the panel?
Thanks,
Frederick Joan
Could you give me a hand with the calculation of the resistance R3 suitable for the LED which I would like to have? My goal is to have an LED
* in the frontpanel (10mm thick)
* round diameter appr. 3mm
* blue color
On digi-key I found one which seems suitable for me: VAOL-3LSBY1 Visual Communications Company - VCC | VAOL-3LSBY1-ND | DigiKey.
It is a VCC with Vf of 3,5V; max. 4.0V. I thought it would be easy for me with some high school formula's but I still don't get it when I try to recalculate the red LED in your manual.
Can you show me how to calculate?
I was thinking to drill a (stepped) hole in the front panel, isolate the leads with shrinking tube and connect to the PS board with a thin insulated wire. Is there something special I should consider? Should I glue it in the panel?
Thanks,
Frederick Joan
Hi John,
Thanks for your suggestion. I have played with it a little bit. Now the question is what source voltage I should use in the calculation. The power supply has a 300VA 2x22V secondary toroid. The resistor is bridged over one of the rectifiers. So should it be 22V or should I multiply by sqrt2 to obtain the railvoltage with 1500 uF of buffering?
Peter uses a 62k Ohm resistor with a red led with Vf of 2.2V. But I cannot get the calculated numbers as shown by the calculator.
Regards,
Frederick Joan
Thanks for your suggestion. I have played with it a little bit. Now the question is what source voltage I should use in the calculation. The power supply has a 300VA 2x22V secondary toroid. The resistor is bridged over one of the rectifiers. So should it be 22V or should I multiply by sqrt2 to obtain the railvoltage with 1500 uF of buffering?
Peter uses a 62k Ohm resistor with a red led with Vf of 2.2V. But I cannot get the calculated numbers as shown by the calculator.
Regards,
Frederick Joan
You should run the LED from one of the DC rails, not across a rectifier. Either rail, it doesn't matter. If you run it from AC the flicker will be obvious as LED's react instantly, not like a bulb.
You can calculate values but until you actually try it and see it in the room, in its location, you just won't know.
Voltage will be approx, 22*1.414 which is around 31 volts DC. Subtract the LED forward voltage and you get say 27 volts. You need to lose that 27 volts across a resistor at "some" current... and that LED is moderately bright at 1200mcd (millicandela) and so a current of just a milliamp or so may well be sufficient.
R=V/I and so you get 27/0.001 which is 27k.
A dab of epoxy is fine for securing LED's. Do NOT use super glue... it migrates and causes a white bloom.
You can calculate values but until you actually try it and see it in the room, in its location, you just won't know.
Voltage will be approx, 22*1.414 which is around 31 volts DC. Subtract the LED forward voltage and you get say 27 volts. You need to lose that 27 volts across a resistor at "some" current... and that LED is moderately bright at 1200mcd (millicandela) and so a current of just a milliamp or so may well be sufficient.
R=V/I and so you get 27/0.001 which is 27k.
A dab of epoxy is fine for securing LED's. Do NOT use super glue... it migrates and causes a white bloom.
Modern LED's are generally super bright, so you won't want a searchlight beaming out at you. It really is trial and error to get a value that suits you.
You can go as high as you like, just don't go lower than a value that would cause the LED maximum current to be exceeded which if we say is 20 milliamps would be around 1.5k.
(to get it absolutely correct you could fit a series variable resistor, get the brightness correct and then measure the pot and fit the nearest fixed value to the 1k5 + pot value. The 1k5 is still needed with the pot to prevent you accidently exceeding the max current)
You can go as high as you like, just don't go lower than a value that would cause the LED maximum current to be exceeded which if we say is 20 milliamps would be around 1.5k.
(to get it absolutely correct you could fit a series variable resistor, get the brightness correct and then measure the pot and fit the nearest fixed value to the 1k5 + pot value. The 1k5 is still needed with the pot to prevent you accidently exceeding the max current)
Attachments
Thanks Mooly, your response has been really helpful. And AdrewT's remark brings me to the idea to have the variable resistor permanently inside the amp. Of course in combination with the fixed value resistor. Now I will try to find my way in the huge store of digi-key to find the right pot. Any suggestions would be most welcome. I am thinking of a model with a small screw to adjust with a screw driver.
regards, Frederick Joan
regards, Frederick Joan
If used in the amp then a small cheap "preset" is fine. In practice I'm sure the current you settle on will be way below 5 or 6 milliamps which is probably as high as a preset will stand long term.
I never use Digikey tbh... lets see,
3386F-1-104TLF Bourns Inc. | 3386F-1-104TLF-ND | DigiKey
3309P-1-104 Bourns Inc. | 3309P-104-ND | DigiKey
I never use Digikey tbh... lets see,
3386F-1-104TLF Bourns Inc. | 3386F-1-104TLF-ND | DigiKey
3309P-1-104 Bourns Inc. | 3309P-104-ND | DigiKey
Hi Peter,
I have purchased an Avel 250VA 2 x 25V transformer thinking my speakers were 8 ohms. I measured the resistance the other day and they are actually just above 6 ohms. Looking at your table on page 49 of your build instructions (for the LM3875) the maximum supply voltage for 6 ohm speakers is approx. 33 Volts.
From my calculations the rail voltage will be 35 to 39 volts (25 x sqrt2 x 1.1 = 39. 10% mains over voltage. 230 volts mains supply). What are the consequences of using the transformer I have and do I need to do anything to mitigate possible over supply voltage?
Cheers,
Tim
I have purchased an Avel 250VA 2 x 25V transformer thinking my speakers were 8 ohms. I measured the resistance the other day and they are actually just above 6 ohms. Looking at your table on page 49 of your build instructions (for the LM3875) the maximum supply voltage for 6 ohm speakers is approx. 33 Volts.
From my calculations the rail voltage will be 35 to 39 volts (25 x sqrt2 x 1.1 = 39. 10% mains over voltage. 230 volts mains supply). What are the consequences of using the transformer I have and do I need to do anything to mitigate possible over supply voltage?
Cheers,
Tim
There is nothing to stop you fitting a normal potentiometer (easier to mount) if that is what you want. Just a normal linear (not log) single gang 100k.