OT warning - are those diffusers on the wall ?
Michael,
this is somewhat off-topic but could you kindly confirm (or not) that those 3 conceptual schematics on the wall are absorbers ?
I love the look of them ...
Cheers,
Max
PS: I am referring to the pics in the first / second post of this thread
Michael,
this is somewhat off-topic but could you kindly confirm (or not) that those 3 conceptual schematics on the wall are absorbers ?
I love the look of them ...
Cheers,
Max
PS: I am referring to the pics in the first / second post of this thread
Last edited:
nice!
something like 20x20in for the surface ?
Not that it's utterly important just to give me some scale.
Cheers,
Max
something like 20x20in for the surface ?
Not that it's utterly important just to give me some scale.
Cheers,
Max
Pass DIY Addict
Joined 2000
Paid Member
I don't mean to be critical, Mike - but that room just looks too clean... Glad to see you added the scope next to the amp so it looks more "DIY."
I built a couple of these MoFos. Just stock 19V 193T biased at 1.7A -
And they sound great! (Being a newbie, I'm always amazed when something I've built actually works).
I'm currently driving a pair of Fostex FE167E full rangers. Whose sensitivity is 94dB.
So I'm concerned about the turn on/off thump.
I would also like to be able to drive 4 ohm speakers.
So... way back in post #325 Ralph G said
"For 4 ohms, you will need approx 1.4 times the current for the same power. But also 1.4 times less voltage. If I would optimize this amp for 4 ohm, I would lower the voltage and increase the current.
So I wouldn't go pass the 19V (maybe even a bit lower: more like 17V) but increase the current to at least 3 ampere. This way the heat is still manageable (for a big sink)."
And post #327 xrk971 said
"Nice thing with 24v SMPS, is ability to add a simple IRFP240 cap Mx to allow soft start (no thumps on or off), reduce AC line ripple by -45dB, and have a flat as a board noise floor. Voltage droput gives about 19v of super clean power. Don't underestimate the importance of needing a turn-on delay relay for sensitive compression drivers or 94dB sensitive speakers. With a cap Mx, the turn on is a gradual 10 second long ramp."
My questions are:
Is it ok or is there a way with my stock MoFos to run 4 ohm speakers?
I'm not sure if the choke is the limiting factor. Since the 193T max current is 2A, wouldn't I need to set the bias down below 1.7A, like 1.4A to keep the current under 2A?
Or, if I use a 24v SMPS and use the "simple IRFP240 cap Mx" xrk971 mentioned, and replace the 193T with a 193V, leave the bias alone at 1.7A, would that work? (The cap Mx drops the voltage to 19V)
Thanks!
-Mike
And they sound great! (Being a newbie, I'm always amazed when something I've built actually works).
I'm currently driving a pair of Fostex FE167E full rangers. Whose sensitivity is 94dB.
So I'm concerned about the turn on/off thump.
I would also like to be able to drive 4 ohm speakers.
So... way back in post #325 Ralph G said
"For 4 ohms, you will need approx 1.4 times the current for the same power. But also 1.4 times less voltage. If I would optimize this amp for 4 ohm, I would lower the voltage and increase the current.
So I wouldn't go pass the 19V (maybe even a bit lower: more like 17V) but increase the current to at least 3 ampere. This way the heat is still manageable (for a big sink)."
And post #327 xrk971 said
"Nice thing with 24v SMPS, is ability to add a simple IRFP240 cap Mx to allow soft start (no thumps on or off), reduce AC line ripple by -45dB, and have a flat as a board noise floor. Voltage droput gives about 19v of super clean power. Don't underestimate the importance of needing a turn-on delay relay for sensitive compression drivers or 94dB sensitive speakers. With a cap Mx, the turn on is a gradual 10 second long ramp."
My questions are:
Is it ok or is there a way with my stock MoFos to run 4 ohm speakers?
I'm not sure if the choke is the limiting factor. Since the 193T max current is 2A, wouldn't I need to set the bias down below 1.7A, like 1.4A to keep the current under 2A?
Or, if I use a 24v SMPS and use the "simple IRFP240 cap Mx" xrk971 mentioned, and replace the 193T with a 193V, leave the bias alone at 1.7A, would that work? (The cap Mx drops the voltage to 19V)
Thanks!
-Mike
