About possible Babelfish J interest

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axelcs

Member
Joined 2003
Hi,
I´m thinking about dimensioning of my Babelfish J while waiting for the boards to come.
Bought two heatsinks from Seifert with 0,125 K/W (according to their brochure), so they get rid of about 200 W/channel.
Could I go with 4 IRF 150 per channel with an 18V transformer (4 x 2 x 24V x 1A = 200 W?)? Do I have to change any values on the base- or daughter-boards … and would one 400 VA transformer per channel be a good choice?
Thanks.
Axel
 
Zen Mod

Zen Mod

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Joined 2003
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axelcs said:
Hi,
I´m thinking about dimensioning of my Babelfish J while waiting for the boards to come.
Bought two heatsinks from Seifert with 0,125 K/W (according to their brochure), so they get rid of about 200 W/channel.
Could I go with 4 IRF 150 per channel with an 18V transformer (4 x 2 x 24V x 1A = 200 W?)? Do I have to change any values on the base- or daughter-boards … and would one 400 VA transformer per channel be a good choice?
Thanks.
Axel
Click to expand...

first .... with 18Vac , resulting in something as 22V5dc rails , it's completely unnecessary going above 3A for Iq , just because you'll hit voltage threshold before you hit I threshold

further , when calculating dissipation , observe that current is flowing through transistor vertical pairs (from +rail to - rail ) , so if you have 3 vertical pairs (if you go for 4 mosfets per channel , why not taking another two ..... ) , you multiply intended Iq/pair with 3

so , let use 25W dissipation per mosfet as example , so 50W per vertical pair - that will give you 50Wx3=150W of heat per channel

(150W of power consumption ..... no less than 350VA xformer per channel and at least 66mF per rail)

for 50W/pair , rail to rail 45Vdc , that's something as 1A1 for Iq ..... giving 3A3 as Iq for channel

it'll result in 25W-ish rms power @8R (voltage threshold) , while 40W-ish @4R load (current threshold)

plenty , if you ask me .......

if you need more power - time is for higher rails , and wise choosing of Iq

so , what are size of room , which speakers and loudness of your listening ?
 
A

axelcs

Member
Joined 2003
Obviosly didn´t understand your comments in post 21...
I have a TMR Standard II, 90dB 6Ohms in 35 qm, normal listening levels, so 25W could be enough:
That means 6 x IRF150 per channel, all resistor as in your schematics (R2, 4, 6 = 0,27R, R1, 3, 5= 180R, R31 ... R36= 0,27R)?
Increasing to 20Vac, the dissipation (+10%) still could be handled by the heatsinks?
Thanks.
 
Zen Mod

Zen Mod

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go with 20Vac secondaries , 3 pairs in output and you'll set Iq as high as heatsinks can handle

in your case - without going to most masculine dissipation per device , you can go with IRFP240 too , easily obtainable from member h_a , in case you already didn't bought quantity to match them by your self
 
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Dukja

Member
Joined 2011
OK, did my homework studying this thread. Here is my newbie talk:

My goal is to get 50W @ 8ohm / ch
1. Rule of thumb for single-ended class A: the output power and dissipated power ratio is about 1:8. Eg. Aleph J has 25W output at 200W dissipation.

2. ZM's post #69: using FW/PL rail voltage 21.5Vdc (+/-21.5V so 43V rail-to-rail), Iq=4A using 1x IRF150/quadrant. Dissipation power=43V * 4A = 172W. Using 1/8 ratio, this will give 20W output.
Question: what is "quadrant"? I guess each channel must have two quadrants since ZM said "42Wrms/8r" in post #69.

3. In ZM's post #21, he said "30V rail - 2A Iq - 50W/mosfet".
Questions: this "/mosfet' means "/IRF150", right? so each "quadrant" has 2x IRF150, right? So that means daughter board is needed to put 2xIRF150 there, correct?

So using the example in Post #69 as a starting point. That means for each channel I need a big square main board (which has 2x mosfet mounting points at two corners). I will need two daughter board. Each daugther board holds two IRF150 and goes to the mosfet mounting point on the main board. I guess that is one "quadrant", since I got 2X IRF150 there, I had 4A Iq. If I use 21.5Vdc rail, I will have 172W dissipation and 20W output from each "quadrant" or daughter board. The total two daughter boards in one channel give me rought 43W @ 8ohm, correct?

For 40W average power, the 8ohm load needs peak volt: 18*1.414 = 25V , or peak current: 2.23*1.414 = 3.1A

Question: I am voltage limited? (25V>21.5V rail) or not yet (25V < 21.5 x 2)?

So if I want to reach 50W, I need to raise rail voltage?

Sorry for the long post and thanks for the help!!
 
Last edited:
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Dukja

Member
Joined 2011
Good morning, ZM! (maybe afternoon, :) )

I forgot to mention my gear. I got a about 85dB speaker (New Philharmonitor from Dennis M.) and listening distance is about 7 feet. Room is about 15x30x7 feet. Usually my listening volume is less than 70dB. With soundtrack, classical music, and a few female vocal music, I don't think my SPL meter ever register more than 90dB. I use some SPL calculation template and it seems with 30W I can get around 95dB before my Aleph 3 clips. That is what I am running now.

So I figure that 50W BJ should let me run up almost 3dB. I just realized that how little amp watt can do with our nonlinear ear. :( So what do you think the best watt route for me? thanks!!
 
Zen Mod

Zen Mod

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:rofl:

Zen Mod said:
meaning that Americans are equally dumb as Europeans , just in opposite direction :rofl:

so , 6L6 , you're Babelfishing Babelfisherman

:clown:
Click to expand...

that was interesting thread .........

so - we can convert your Aleph 3 to Aleph J3 (simple to do) , and you can make somewhat stronger Aleph , so having two great amps in the house

;)

if you click on , you'll find SM for Aleph 5 , which is roughly what you're looking for , regarding power range

look at schematic and read the text

that means - 30-ish volts PSU rails , around 150W of heat per channel

it demands (speaking of Babelfish J V2.) main pcb and two daughter boards , for 3 pairs of mosfet outputs, all that speaking per channel

didn't looked on posts you mentioned above , but if I was writing about quadrants , no other way than it was strictly related to Aleph X , or some other Papamp , being symmetrical in construction ..... meaning - having four quadrants populated with mosfet outputs

that's not the case with these simple Aleph iterations
 
D

Dennis Hui

Member
Joined 2002
Paid Member
Hi Dukja,

Have you seen this thread? :
http://www.diyaudio.com/forums/mult...much-voltage-power-do-your-speakers-need.html

Assuming you are listening with a digital source, you can get an idea how much
voltage swing you are currently using, and hopefully how much larger an amp you
want.

In the event a larger Aleph is required, just build a new one and send your original
Aleph 3 to Zen Mod...for proper disposal. :) :) :)

Cheers,
Dennis
 
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