Hello All,
I am designing a 45 +45 watt stereo amplifier using the lm4780 and I trying to decide what transformer to use. I will need +-35V rails so this is what I came up with.
1. Will a 24-0-24 150VA toroid transformer be sufficient for my project or shall I increase the VA rating?
2. Are there any major differences between the toriod and "box(not sure what they are really called)" transformers configs? I would like to go with the box configs since they seem smaller in size.
2. Does anyone know of any good websites that sell transformers?(its seems that there are few out there.)
Thanks guys
I am designing a 45 +45 watt stereo amplifier using the lm4780 and I trying to decide what transformer to use. I will need +-35V rails so this is what I came up with.
1. Will a 24-0-24 150VA toroid transformer be sufficient for my project or shall I increase the VA rating?
2. Are there any major differences between the toriod and "box(not sure what they are really called)" transformers configs? I would like to go with the box configs since they seem smaller in size.
2. Does anyone know of any good websites that sell transformers?(its seems that there are few out there.)
Thanks guys
Make sure you use 8 ohm speakers with that voltage.
Many people seem to choose minimum 160VA for 50W x 2.
But I have seen MANY kits proclaiming 100W and only having a 100VA toroidal included( no way)
make sure you have between 10000uF to 20000 uF of filtering caps per rail.
(this is my opinion about what i have read on these forums and simple maths and common sence, others may differ)
Tang
Many people seem to choose minimum 160VA for 50W x 2.
But I have seen MANY kits proclaiming 100W and only having a 100VA toroidal included( no way)
make sure you have between 10000uF to 20000 uF of filtering caps per rail.
(this is my opinion about what i have read on these forums and simple maths and common sence, others may differ)
Tang
Hi,
low values of combined smoothing and decoupling located at the chipamp seem to do very well for good sound quality. This is particularly applicable to high sensitivity speakers.
I suspect the overriding reason for this, is very good mid and treble performance, where much of the current demand is very transient.
I know that sustained bass power will draw down the voltage (with it's attendant high ripple) on small caps more than on big caps.
If one wants good bass response and good power delivery then I suggest that a separate chipamp be used for the bass driver, and leave the relatively light loading of mid and treble to a chipamp tuned to give it's best for that range of frequencies.
Then that gives the flexibility/option to tune the bass chipamp and driver to give best performance for the low frequencies in the signal.
That way you get the best of both worlds.
low values of combined smoothing and decoupling located at the chipamp seem to do very well for good sound quality. This is particularly applicable to high sensitivity speakers.
I suspect the overriding reason for this, is very good mid and treble performance, where much of the current demand is very transient.
I know that sustained bass power will draw down the voltage (with it's attendant high ripple) on small caps more than on big caps.
If one wants good bass response and good power delivery then I suggest that a separate chipamp be used for the bass driver, and leave the relatively light loading of mid and treble to a chipamp tuned to give it's best for that range of frequencies.
Then that gives the flexibility/option to tune the bass chipamp and driver to give best performance for the low frequencies in the signal.
That way you get the best of both worlds.
from everything I've read around these parts, it seems that builders such as Peter Daniel recommend at least 220 VA, and usually choose more in the range of 300 VA. naturally, choose what works best for you. 150 VA will power it, but adding a more powerful transformer will add to the sonics.
recommended transformers, again, are a matter of opinion, but i see a lot of recommendations for Plitron, followed by Avel if you're on a tighter budget.
sites to buy stuff:
plitron power transformers: http://www.plitron.com/shopping/sho...id=3&cat=Standard+Power+Toroidal+Transformers
partsexpress.com is one place to get avel transformers
additionally, you can also get Hammond transformers from parts express, which are boxy. google may provide better results, not sure.
-Jared
recommended transformers, again, are a matter of opinion, but i see a lot of recommendations for Plitron, followed by Avel if you're on a tighter budget.
sites to buy stuff:
plitron power transformers: http://www.plitron.com/shopping/sho...id=3&cat=Standard+Power+Toroidal+Transformers
partsexpress.com is one place to get avel transformers
additionally, you can also get Hammond transformers from parts express, which are boxy. google may provide better results, not sure.
-Jared
Ok guys This is what I have ordered so far through your help.
All I have left to order is the two 10,000uF capacitors. I have been looking for them online all day and can't seem to find good ones.
Does anyone have any suggestions on brand or specific types and where I could purchase one?
Thanks
- 400V 25A Bridge Rectifier
- Littlefuse 4A 3AG Slow Blow Fuse
- AVEL Y236652 250VA 25V+25V Toroid
All I have left to order is the two 10,000uF capacitors. I have been looking for them online all day and can't seem to find good ones.
Does anyone have any suggestions on brand or specific types and where I could purchase one?
Thanks
Where are you buying from?
Do you want to experiment?
Many people seem to love the very expensive black gate capacitors , others like panasonic.
Me , I used the first ones i could get my hands on.
If you can't get 10000uF look for sizes like 4700 or 8200 and double them up.
You probably have your circuits done , but i love this guy's article:
http://www.tnt-audio.com/clinica/ssps1_e.html
Do you want to experiment?
Many people seem to love the very expensive black gate capacitors , others like panasonic.
Me , I used the first ones i could get my hands on.
If you can't get 10000uF look for sizes like 4700 or 8200 and double them up.
You probably have your circuits done , but i love this guy's article:
http://www.tnt-audio.com/clinica/ssps1_e.html
The maximum transformer voltage will be around 18Vac to 22Vac to ensure these 35Vdc caps are not overloaded when mains is at maximum tolerance and loading is light, eg. rail fuses blown, or amp temporarily disconnected.synthius said:
Before ordering, do the calculations for your mains tolerance and your transformer regulation.
I don't think im going to risk it, my graduation depends on this amplifier working perfectly. I am looking at panasonic FC caps with a much higher voltage now.
Anyone know where I could get some panasonic FC 4700uF or 10000uf caps from?? Specifically in the U.S.
I can't find a single website that carries them within the U.S.
Also, do you guys recommend using resistors in parallel to drain the Large caps when powering down the amp? or is this not necessary?
What about your experience with snubber circuits on the rails? My power supply is growing by the day with all the extra components i'm thinking of adding.
Anyone know where I could get some panasonic FC 4700uF or 10000uf caps from?? Specifically in the U.S.
I can't find a single website that carries them within the U.S.
Also, do you guys recommend using resistors in parallel to drain the Large caps when powering down the amp? or is this not necessary?
What about your experience with snubber circuits on the rails? My power supply is growing by the day with all the extra components i'm thinking of adding.
http://www.apexjr.com/capacitorsR.html
12,000Mfd 50V
Snap in Nichicon $1.99
Or bundle a bunch of these together:
1000 Mfd 50V
Electrolytic Nichicon $0.30
As regards transformer VA ratings, my rule-of-thumb is simple: 2VA for every watt RMS I expect the amp to put out. Example: 60W/8R, 100W/4R, stereo needs 400VA.
Can you get away with less?
Sure.
Most commercial designs can and do, but the bigger the transformer the better it sounds until you reach a point of diminishing return at about 2VA per watt.
12,000Mfd 50V
Snap in Nichicon $1.99
Or bundle a bunch of these together:
1000 Mfd 50V
Electrolytic Nichicon $0.30
As regards transformer VA ratings, my rule-of-thumb is simple: 2VA for every watt RMS I expect the amp to put out. Example: 60W/8R, 100W/4R, stereo needs 400VA.
Can you get away with less?
Sure.
Most commercial designs can and do, but the bigger the transformer the better it sounds until you reach a point of diminishing return at about 2VA per watt.
Ok here is what i came up with....it is a mixture of designs i've been researching lately.
Here is the Power Supply I designed for my lm4780 45Watt Stereo Amp.
Can you guys critique my design and offer any suggestions??
Can somebody further explain the purpose of the 2.2k resistors, i know they're used to bleed the caps but am not sure what benefits that has on the PSU.
Thanks
Here is the Power Supply I designed for my lm4780 45Watt Stereo Amp.
Can you guys critique my design and offer any suggestions??
Can somebody further explain the purpose of the 2.2k resistors, i know they're used to bleed the caps but am not sure what benefits that has on the PSU.
Thanks
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