Well cheap compared to all the monster amps out there

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 - CADCAM.ZIP

Edited August 3, 20206 yr by kevin gilmore

Color me interested.

Interesting. What's the function of the Flat jumper?

Takes out the 6db bass boost filter.

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.

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 August 3, 20206 yr by kevin gilmore

can we call it The Unbalanced RAAL Driver

I was hoping for Gertrude.

Gertrude sounds like a great name.

RAAL-star would also work

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

Just Peltier cool that shit.

If somebody is going to get these PCB's fabricated, I would be interested in a couple. Please PM me so that we can share costs?

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 August 6, 20206 yr by justin

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 August 6, 20206 yr by justin

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

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.

nope, i ordered 2oz for a prototype

Once we get a confirmed working layout I can order a bunch and distribute as needed.

Does that mean some (many?) of you have/will buy Raal SR1a 'phones?  It certainly offers a nice counterpoint to Staxen.

0507201154a by drjlo2, on Flickr

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 

wired in series for +/-24v and then connected to each channel

1 hour ago, kevin gilmore said:

wired in series for +/-24v and then connected to each channel

Thanks very much Kevin 

I'm interested.  Seems like these headphones are the new hotness.

allpcb rejected the gerbers, the format they support is R274-X, I’m hopeless with this stuff, what do I need to do?