Parts Express is easy go to place for Avel Lindberg transformers.
If he means 30 -0- 30 AC voltage
and your shooting for 100 watts
Good rule of thumb is 2x VA (Volts Amps) or 2x Wattage for transformer.
So your looking for 200 VA or 200 watt transformer.
They use to have a 180 VA , 250 VA and 330 VA 30 - 0 -30
transformer at parts express.
Seems now they only carry = 30 - 0 - 30 250 VA
which would be more than good for a chip amp.
Rectified voltage unloaded be 30 x 1.414 = 42.42
then take out 1.2 volts for rectifier drop.
41.2 volts +/_
Its a chip amp so 25- 0-25
also be fine since to much voltage
means to much power at 4 ohms.
30 -0-30 is really pushing it at 4 ohms
Either way shoot for a healthy heatsink.
Id assume or dont know if the " crush" amps
are 8 ohms only as combos.
Then you could really push voltage
but only at 8 ohms.
Not sure i dont expect more than 60 watts
from a chip a doo
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Ahh cool
So was a good guess
and makes more sense.
You can run voltage little high
if only 8 ohms.
But it looks like 2 chips bridged.
So definitely 8 ohms min.
Bridged / floating load
Each amplifier sees half the load.
So 8 ohm load, each amplifier
is actually running 4 ohms.
Its a Tradeoff with bridged.
You get more voltage swing on output for power.
But each amplifier basically draws more current.
So 4 ohm load be really stressful.
Each amplifier actually powers 2 ohms.
And chip amps cant push current like that.
Or depends on how much voltage your feeding it.
You can hit or exceed the max current of the chip.
I wouldn't run to much voltage with a bridged amp.
you could run 30 -0-30 transformer
or even 25 - 0 - 25 transformer to not push the chips
to far. 25 volte rectified with drop be about 34 volts +/_
rails. Its bridged so wants current.
A 25 -0-25 330 VA transformer be option too.
or 250VA.
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Excellent!
Hadn't read last 50 or 60 posts 😱 because thread kept jumping all over the place, goalposts were changed everyday, etc. but now was chiming in you stop here and build something
Serious.
Among other reasons, because trying to build the perfect amp on first try can be very frustrating, and that after a LOT of work to get everything, so my suggestion is, Just start the engine running:
1) get the
* power transformer : 28+28V 150-200-250VA
* diode bridge: suggested GBJ2510 or a 6A 400V bridge and worst case any generic chassis mounted 35A 200-400V bridge, simply because it became a standard and
* filter caps: 4700uF@50V needed for the datasheet/Orange bridged TDA7294 amp.
The apparently useless 1000uF@50V caps shown in parallel actually mean those are placed close to the Chipamp board to decouple it.
Build that power supply.
No doubts there, it's a simple circuit, it will be kept for sure, can feed 1 or 2 TDA7294, what's not to like?
No doubts, not wasted money or effort.
I bet there are Ebay "universal" PSU boards to hold bridge and caps for peanuts.
For now mount PT and the rest on a piece of wood.
2) for now get a working assembled generic TDA7294 board from EBay, mount it on a heatsink, put the whole pie: supply and amp on a piece of wood and wire it together.
You'll need some kind of DIY metal bracket to mount input and speaker jacks, power switch, fuse, mains connector, etc. without committing yet to a chassis and even less , a cabinet.
3) presto! Now you have a working amp, connect current preamp and speaker and hear it .😱
That is the sound you'll get, basically (can be tweaked but that comes later).
It's 90% of what you asked for, not bad huh?, only problem is it will put out mere 25-30W RMS into your 16 ohm speaker.
SO WHAT? 😄
Test all you want, tell us what you hear, record a couple YT videos and link them here.
4) why not straight build the Orange clone board?
Only because I do not 100% trust user "back engineered" designs, have seen way too many wrong schematics floating around, , even a small error can ruin your day; and even less Hobbyist designed PCBs (even large Companies tweak and retweak many times) so PLAY IT SAFE and start with a commercial, built by many one.
After (reduced) project is up and running, you go on with the full one.
Keep us updated.
Hadn't read last 50 or 60 posts 😱 because thread kept jumping all over the place, goalposts were changed everyday, etc. but now was chiming in you stop here and build something
Serious.
Among other reasons, because trying to build the perfect amp on first try can be very frustrating, and that after a LOT of work to get everything, so my suggestion is, Just start the engine running:
1) get the
* power transformer : 28+28V 150-200-250VA
* diode bridge: suggested GBJ2510 or a 6A 400V bridge and worst case any generic chassis mounted 35A 200-400V bridge, simply because it became a standard and
* filter caps: 4700uF@50V needed for the datasheet/Orange bridged TDA7294 amp.
The apparently useless 1000uF@50V caps shown in parallel actually mean those are placed close to the Chipamp board to decouple it.
Build that power supply.
No doubts there, it's a simple circuit, it will be kept for sure, can feed 1 or 2 TDA7294, what's not to like?
No doubts, not wasted money or effort.
I bet there are Ebay "universal" PSU boards to hold bridge and caps for peanuts.
For now mount PT and the rest on a piece of wood.
2) for now get a working assembled generic TDA7294 board from EBay, mount it on a heatsink, put the whole pie: supply and amp on a piece of wood and wire it together.
You'll need some kind of DIY metal bracket to mount input and speaker jacks, power switch, fuse, mains connector, etc. without committing yet to a chassis and even less , a cabinet.
3) presto! Now you have a working amp, connect current preamp and speaker and hear it .😱
That is the sound you'll get, basically (can be tweaked but that comes later).
It's 90% of what you asked for, not bad huh?, only problem is it will put out mere 25-30W RMS into your 16 ohm speaker.
SO WHAT? 😄
Test all you want, tell us what you hear, record a couple YT videos and link them here.
4) why not straight build the Orange clone board?
Only because I do not 100% trust user "back engineered" designs, have seen way too many wrong schematics floating around, , even a small error can ruin your day; and even less Hobbyist designed PCBs (even large Companies tweak and retweak many times) so PLAY IT SAFE and start with a commercial, built by many one.
After (reduced) project is up and running, you go on with the full one.
Keep us updated.
It looks like you'll need two transformers - or one with both the 30-0-30 and maybe a 12-0-12 secondary windings for the +5, +/- 15 part. I'm pretty sure you cant just use the 30-0-30 winding there...
Interesting how they do the sequenced / delayed logic levels in analog, to "bring up" the chip amps out of standby and un-mute them.
Here are a few that I found that should work?
Toroidal from Parts Express 25 +/- 250VA
Mean Well SMPS 24vdc (not sure if this is what I need)
Connex SMPS300RE I can choose 24 or 30 +\- and an auxiliary voltage (I’m guessing that would be for the preamp?
Is there any reason not to use SMPS?
If I do choose the toroidal from Parts Express would I need an addition transformer for the preamp?
Lastly, the Orange amps use a conventional PT, not a toroidal. Would it be better to try to find one (and pay more for
One) that fits the exact specifications I need?
The board has what looks like diode rectification. Is this different than that?
Or is this in reference to testing tbs build with a generic board instead of the one I have?
Sound logic!
I do know that he has tested and used the boards for his amp and has sold to others.
I’m not opposed to buying a generic one but I do want to spend the least amount possible.
The datasheet says that you should only use 8 ohms and above in bridged mode. Also the chip can handle up to 10A peak.
https://www.digikey.com/htmldatasheets/production/555092/0/0/1/tda7294.html
https://www.digikey.com/htmldatasheets/production/555092/0/0/1/tda7294.html
You need dual rail SMPS for amplifier.
And same thing 250 watts.
34 to 42 volts +/_
Board seems setup with rectifiers/linear supply
so just use good old linear supply/ transformer
looks like preamp has regulated dual rail also.
So need another transformer for that.
Manufacture do a custom transformer.
That has different voltage taps for power/amp
pre/amp.
people have use switch modes.
Hate them pure garbage for MI applications
buts it been done, they love shutting off mid
performance. If not done right.
Many rated at peak current.
So during performing using high current, specially
distortion type signals with high duty cycle.
You need to make sure its actually rated
for getting punched in the face.
Switch turds, blahhhhh
Close and usable, sort of, but this one is better and cheaper:
https://www.antekinc.com/as-3428-300va-28v-transformer/
28VAC+28VAC main secondary, auxiliary 15+15VAC auxiliary for preamp
.exactly what this amp demands.
All of $52
No.
No
More than one, but main is here you need +/-40V rails or a little less, not 24V single rail
From parts express yes, from Antek no , it matches orange specs.
Yes.
It needs diode rectifiers .
I suggested some.
If board includes them, by all means use them.
If you feel confident, straight build the cloned OR120 board.
I suggested the pre built single Chipamp one because it costs about 10 bucks and after this full build is finished it that board not a waste by any means but good to build an extra/spare 50 W amp using leftovers or revive any old 20 to 50-60W amp you get or ... or ... or ...
Looks good
and makes more sense with concerns about
exceeding chip ratings with 42 volt rails.
When around 32 to 35 volt rails makes more sense.
Hmmm
25-0-25 was a good call at 330 VA
Why I recommended a 330 watt transformer
which does not follow rule of thumb of Double the power
going in or 200 watts. Again its a tradeoff with bridged amplifiers
you get more voltage swing, but it consumes more current
so you need to up the VA rating.
about what they are using.
to figure VA assuming generic .8 power factor.
formula for VArating = (V secondary x I)/0.8
V = secondary voltage ( 51 V )
I = current ( 6 Amps )
.8 = power factor
According to unlikely but maybe ish tiny transformer
magic sticker
382.5 VA transformer for power section.
Great thing about good old transformers
is you can pull more current than their rating.
Voltage drops, but current keeps coming.
Only problem is they can exceed the wire gauge
current rating and get hotter than hell.
Was not regulated as much in the 70's and 80's
but now days max exceeded transformer rating
was 20% to pass certification. Likely been lowered
since, have not done commercial stuff in awhile.
As you can see Orange used a transformer
with thermal cutoff rated 130c
Just in case this happens.
Oh I bet that little guy gets hot too.
Least they used a E core, which I like as well.
Most manufacturing switched to toroidal cause they are
somewhat lighter/ were cheaper. I like the old school E cores.
Ironical not many used for high power.
So you can get " more expensive" E cores dirt cheap now surplus
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@WhiteDragon Sorry, it won’t let me quote your reply..
Do you know of a transformer that fits those specs? I looked at Antek’s site and didn’t see anything quite right.
Thanks for the detailed response!
Do you know of a transformer that fits those specs? I looked at Antek’s site and didn’t see anything quite right.
Thanks for the detailed response!
Thanks for answering all of my questions!
Can you elaborate on this answer?
I thought 40v would be too high for the tda7294
Also, if I were to seek out a switching power supply, would I Need one with 3-4 outputs? (Power amp and preamp?)
Lastly, can you tell me your opinion of smps? Or rather why it’s not a good idea?
In my mind, it’s smaller, lighter, and more efficient (? Not entirely sure that’s true, but I think I’ve read this?)
Also, would using one mean that the heatsink doesn’t need to be as robust?
Assuming your answers will send me away from using them with this build, do you think they’re okay with Class D? Or can/should power transformers be used for those as well?
Lastly, on heat sinks.. how do I know what to get? I’ve tried to look into those and didn’t know where to start.
Thank you again for your time
I'm worried you don't seem to notice the difference between single supply and dual supply.
TDA7294 needs dual , +/-40V DC supplies.
Or +/-35V to play it safe.
You constantly mention "40V" or "25V" or something like that, which is wrong.
You even bought the relevant PCB so please stop shifting goalposts.
Heatsink cools power transistors and nothing else.
Amplifier cares only about voltage it receives, not where it comes from.
Amp might be fed from batteries, solar panels, a 3 phase alternator wind generator or a bunch of Piezo crystals stomped on by a bunch of horses.
If specs are met, same thing..
These will work fine. In general 160mm wide by 62-75mm high with 25mm to 35mm fins is perfect; 130 mm wide is tight, any less will overheat, so:
https://www.amazon.in/Generic-Aluminum-Heatsink-LM3886-TDA7294/dp/B06WLNMKT5
Or https://www.ebay.com/itm/162006414733
This one would be tight:
https://www.ebay.com/itm/163489881565
In theory two similar to these, one per Chipamp would do, specially for Home HiFi use, but not at all in grueling MI use.
https://www.mypcb.in/products/tda72...ifier-assembled-board-with-heat-sink-12327520
Back to supply voltage: +/- 40V is fine , coming from a 28+28VAC transformer, it's a popular value.
That said, enlarging the very fuzzy Orange transformer label, it seems to say 26.5+26.5VAC for nominal +/-37.5VDC.
Fine. They do not go to the limit.
Even a 2 x 25 or 26VAC transformer will do, so ....
No more excuses, just start building ,😄
Now it's up to you 😄
TDA7294 needs dual , +/-40V DC supplies.
Or +/-35V to play it safe.
You constantly mention "40V" or "25V" or something like that, which is wrong.
SMPS not recommended so irrelevant.
We are way beyond that post, now end goal is to build an Orange 120 power amp .
You even bought the relevant PCB so please stop shifting goalposts.
Absolutely unrelated.
Heatsink cools power transistors and nothing else.
Amplifier cares only about voltage it receives, not where it comes from.
Amp might be fed from batteries, solar panels, a 3 phase alternator wind generator or a bunch of Piezo crystals stomped on by a bunch of horses.
If specs are met, same thing..
These will work fine. In general 160mm wide by 62-75mm high with 25mm to 35mm fins is perfect; 130 mm wide is tight, any less will overheat, so:
https://www.amazon.in/Generic-Aluminum-Heatsink-LM3886-TDA7294/dp/B06WLNMKT5
Or https://www.ebay.com/itm/162006414733
This one would be tight:
https://www.ebay.com/itm/163489881565
In theory two similar to these, one per Chipamp would do, specially for Home HiFi use, but not at all in grueling MI use.
https://www.mypcb.in/products/tda72...ifier-assembled-board-with-heat-sink-12327520
Back to supply voltage: +/- 40V is fine , coming from a 28+28VAC transformer, it's a popular value.
That said, enlarging the very fuzzy Orange transformer label, it seems to say 26.5+26.5VAC for nominal +/-37.5VDC.
Fine. They do not go to the limit.
Even a 2 x 25 or 26VAC transformer will do, so ....
No more excuses, just start building ,😄
Now it's up to you 😄
Not really 😄
The preamp was never a problem, he has a wide selection of them, very versatile ones, including simulations, all he wanted was an MI type power amp to drive MI speakers 😄
A very clear and detailed goal, but he got a ton of arm twisting , 9 pages of it, trying to convince him to build something completely different.
Oh well.
Thanks everyone!
I'm planning to purchase the transformer and heatsink today, then work on sourcing the components.
I don't see a volume pot in the schematic I shared. Where should that go and what value should I use?
I am going to build it on wood as suggested above and then source a chassis. I am thinking a rack style would be the best way to go.
I have more questions too, I apologize for that. I just need to know answers for own sanity.
1. Does the power amp need to be ground to the chassis? I have seen this with tube amps, but I wasn't sure if that was the case with these.
2. Since I am deciding to put a preamp in the same chassis, should I keep the grounds separate? I have also read about this and I wasn't sure if it was true and if so, can someone explain why?
3. Can someone explain the power supply specs to me?
The Antek transformer is 28v +/- ..is that VAC and then its increased when it goes through diode rectification and turned into VDC?
If I have that wrong, please correct me!
If it is correct, is there a simple way to understand how the diode rectification is changed to set a specific dc voltage?
Thanks again for all of the information!
I'm planning to purchase the transformer and heatsink today, then work on sourcing the components.
I don't see a volume pot in the schematic I shared. Where should that go and what value should I use?
I am going to build it on wood as suggested above and then source a chassis. I am thinking a rack style would be the best way to go.
I have more questions too, I apologize for that. I just need to know answers for own sanity.
1. Does the power amp need to be ground to the chassis? I have seen this with tube amps, but I wasn't sure if that was the case with these.
2. Since I am deciding to put a preamp in the same chassis, should I keep the grounds separate? I have also read about this and I wasn't sure if it was true and if so, can someone explain why?
3. Can someone explain the power supply specs to me?
The Antek transformer is 28v +/- ..is that VAC and then its increased when it goes through diode rectification and turned into VDC?
If I have that wrong, please correct me!
If it is correct, is there a simple way to understand how the diode rectification is changed to set a specific dc voltage?
Thanks again for all of the information!
It’s simple - VDC=1.4xVAC, when there is NO load. What it drops to under load must be tested, because it depends on the load and characteristics of the transformer. With Antek‘s it is pretty uniform, at full DC load (65% of rated VA due to power factor) they drop to about 88% of no load DC.
If you are trying to get around +/-40V you have the right one. 200 VA would be the minimum size to use, 300 may be better. The 200VA will give you +/-35V at 1.8 amps DC load (130 watts). The 300 will give you 2.8 amps when it drops to +/-35, and somewhat more at 1.8 amps. Strictly voltage limited designs (like chip amps) benefit from the larger VA transformer since upping the unloaded DC to balance out the sag may NOT be an option.
If you are trying to get around +/-40V you have the right one. 200 VA would be the minimum size to use, 300 may be better. The 200VA will give you +/-35V at 1.8 amps DC load (130 watts). The 300 will give you 2.8 amps when it drops to +/-35, and somewhat more at 1.8 amps. Strictly voltage limited designs (like chip amps) benefit from the larger VA transformer since upping the unloaded DC to balance out the sag may NOT be an option.