Cheap Raal Direct Drive Amp

[kevin gilmore]

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, 2020 by kevin gilmore

[n_maher]

Color me interested.

[dingding123]

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

[kevin gilmore]

Takes out the 6db bass boost filter.

[n_maher]

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.

[kevin gilmore]

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, 2020 by kevin gilmore

[justin]

can we call it The Unbalanced RAAL Driver

[swt61]

I was hoping for Gertrude.

[kevin gilmore]

Gertrude sounds like a great name.

[justin]

RAAL-star would also work

[justin]

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

[RudeWolf]

Just Peltier cool that shit.

[themystical]

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?

[justin]

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, 2020 by justin

[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, 2020 by justin

[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

[themystical]

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.

[justin]

nope, i ordered 2oz for a prototype

[n_maher]

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

[Jon L]

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

[themystical]

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 

[kevin gilmore]

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

[themystical]

1 hour ago, kevin gilmore said:

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

Thanks very much Kevin 

[Sherwood]

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

[johnwmclean]

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