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Cheap Raal Direct Drive Amp


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Well cheap compared to all the monster amps out there :D

So correctly done, one would do the Uberamp2-Raal edition, which results in something really big,heavy and lot of heat. And a custom and large chassis, and a pile of $$$

This is a bit cheaper and easy enough for just about anyone to do.

From the Ti Opa541 datasheet, showing paralled opamps good for at least 7 amps rms of output into anything including a dead short...

Designed to be mounted directly to the heatsink, amp board right angle to the heatsink. All wires to the board directly soldered, 4 oz copper highly recommended.

Power supplies are a minimum of 24V at 10 amps, like this, but more current not a bad thing. You need a pair of these!

https://www.mouser.com/ProductDetail/MEAN-WELL/UHP-350-24?qs=YCa%2FAAYMW011AuZKubw9Sw%3D%3D

So by the time you get done, about $400 in parts. Better than spending $4500 on an unknown made in croatia thing with inside pictures deliberately hidden.

.02uf is a film cap, 10uf are mlcc caps, .1 ohm resistors are caddock

https://www.mouser.com/ProductDetail/Caddock/MP930-010-1?qs=%2Fha2pyFaduhEz86YdyVUnzk8BCJOExJuzQrioCIidHi6TdsKxEEAVg%3D%3D

 

raalopamp.jpg

raalopamp - CADCAM.ZIP

Edited by kevin gilmore
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Kevin,

Pardon the stupid question - from a W/ch perspective, what are you projecting this thing to be capable of with the above-referenced power supply?  My bubba math says something like 100W, Just looking to get an idea of heat sink requirements.

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Posted (edited)

I would think that a minimum of 50 watts of heat per channel seems reasonable. 

a dissipante 3U seems like it would work. probably 1 size down would also work if there is enough room for the switchers.

Edited by kevin gilmore
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3 hours ago, kevin gilmore said:

I would think that a minimum of 50 watts of heat per channel seems reasonable. 

a dissipante 3U seems like it would work. probably 1 size down would also work if there is enough room for the switchers.

I like how a heatsinked 3U chassis is now the modest build answer

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i have 5 on the way, but i don't know how many i'll blow up yet.

you should use allpcb though, it's like $1.99 for new customers to order these

Edited by justin
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Mouser #: 595-OPA541AP
 
Mfr. #: OPA541AP
Desc.: Operational Amplifiers - Op Amps Operational Amplifiers - Op Amps Hi-Power Monolithic Op Amp
  4 $21.40 $85.60
4 Shipped 06-Aug-20 57782631
 
Mouser #: 80-T354G106K035AT
 
Mfr. #: T354G106K035AT
Desc.: Tantalum Capacitors - Solid Leaded Tantalum Capacitors - Solid Leaded 10.0uF 35.0V10%
  10 $1.28 $12.80
10 Shipped 06-Aug-20 57782631
 
Mouser #: 710-860160575031
 
Mfr. #: 860160575031
Desc.: Aluminum Electrolytic Capacitors - Radial Leaded Aluminum Electrolytic Capacitors - Radial Leaded WCAP-ATLL 35V 1000uF 20% Radial
  4 $1.29 $5.16
4 Shipped 06-Aug-20 57782631
 
Mouser #: 581-SR212A200JAR
 
Mfr. #: SR212A200JAR
Desc.: Multilayer Ceramic Capacitors MLCC - Leaded Multilayer Ceramic Capacitors MLCC - Leaded 200V 20pF 5% C0G
  4 $0.45 $1.80
4 Shipped 06-Aug-20 57782631
 
Mouser #: 505-MKP20.022/100/5
 
Mfr. #: MKP2D022201B00JSSD
Desc.: Film Capacitors Film Capacitors 100V .022uF 5%
  2 $0.48 $0.96
2 Shipped 06-Aug-20 57782631
 
Mouser #: 71-RN55C6501B
 
Mfr. #: RN55C6501BB14
Desc.: Metal Film Resistors - Through Hole Metal Film Resistors - Through Hole 1/10watt 6.5Kohms .1% 50ppm
  2 $0.61 $1.22
2 Shipped 06-Aug-20 57782631
 
Mouser #: 71-RN55C-B-10K
 
Mfr. #: RN55C1002BB14
Desc.: Metal Film Resistors - Through Hole Metal Film Resistors - Through Hole 1/10watt 10Kohms .1% 50ppm
  10 $0.999 $9.99
10 Shipped 06-Aug-20 57782631
 
Mouser #: 709-UHP-350-24
 
Mfr. #: UHP-350-24
Desc.: Switching Power Supplies Switching Power Supplies 350.4W 24V 14.6A W/ PFC
  2 $67.31 $134.62
2 Shipped 06-Aug-20 57782631
 
Mouser #: 684-MP930-0.1
 
Mfr. #: MP930-0.10-1%
Desc.: Thick Film Resistors - Through Hole Thick Film Resistors - Through Hole 0.1 ohm 30W 1% TO-220 PKG PWR FILM

 

Qty 4

Edited by justin
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oops..one mistake. the tantalum caps (10uf) should probably be ceramic such as RCER71H106MWK1H03B

or use the tantalum ones and bypass with a .1uf c0g under the board such as RDE5C1H104J2K1H03B

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2 hours ago, justin said:

i have 5 on the way, but i don't know how many i'll blow up yet.

you should use allpcb though, it's like $1.99 for new customers to order these

Really? You think they will do 5 of these at 4oz copper for that price? That would be the bargain of the century! I will give them a try. Thanks very much.

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This might be a silly question but I have never worked with SMPS’s before. Are the two power supply modules connected together to provide +-24V DC and then connected in parallel to both channels or is each module dedicated to each channel 

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