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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 2nd December 2019, 08:06 PM   #31091
wrinkle is offline wrinkle  United Kingdom
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Beautifully worked out, but when I follow Damir's links for the 200W version it is usingthe following transistors:
2SK134C
2SJ49C,
These are 140V, 7A, 100w devices.
Semiconductor: 2SK134 (2SK 134) - SILICON N-CHANNEL MOSFET TRANSISTOR... - UK (GBP)
not trying to suggest buying from there, but it was the first useful google link I found
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Old 2nd December 2019, 08:08 PM   #31092
wayne is offline wayne  United States
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John Curl's Blowtorch preamplifier part III
MOSFET transistors are plenty reliable as the above calculations show. At under $2.00 in quantity 24 of them will get you 350 Watts and never break. Broken units are much more expensive in shipping and reputation compared to a few $ upfront. Nothing like a little overkill for DIY.
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Old 2nd December 2019, 09:41 PM   #31093
Tournesol is online now Tournesol  Belgium
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Quote:
Originally Posted by dadod View Post
When I started this amp it was just for me and laterals are quite expensive (I needed six power amps to drive open baffle Orion loudspeakers). That is how all started, and Richard asks for two 200W version finished boards.
Damir
Quote:
Originally Posted by wrinkle View Post
Beautifully worked out, but when I follow Damir's links for the 200W version it is using the following transistors:
2SK134C
2SJ49C
I do not understand anymore. The 2SK134C/2SJ49C would not be Laterals?
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Old 2nd December 2019, 10:22 PM   #31094
scottjoplin is offline scottjoplin  Wales
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Yes, they are laterals
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Old 2nd December 2019, 10:53 PM   #31095
Bonsai is offline Bonsai  Europe
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I would consider all output power calculations worst case with something like 45 degrees phase angle.

I have a LTspice tool somewhere and it is amazing how quickly things get out of hand with inductive loads. I use 6 pairs x 250 watt devices for that very reason on my 240 watter
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Old 2nd December 2019, 11:13 PM   #31096
syn08 is offline syn08  Canada
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Anybody knows (looking mostly for data, not opinions) what would be the absolute worst case (from a design perspective) for a speaker impedance? I have among others a pair of Infinity Kappa 100 "amp killers" that drop under 2ohm (actually, 1.8ohm) somewhere in the bass, but the phase angle is almost zero there. I've seen other such pathological (but great sounding) speakers so I concluded that, as a rule of thumb, designing for half the nominal impedance is covering the worse case (either low impedance module, or a large phase angle) although for most cases it is an overkill. Designing for both low module impedance and 45 degrees of phase angle is IMO a double overkill, in particular in DIY. With the notable exception of something like the Apogee Scintillas, which dip under 1ohm - I call these "coned shorts".

Last edited by syn08; 2nd December 2019 at 11:17 PM.
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Old 2nd December 2019, 11:29 PM   #31097
billshurv is online now billshurv  United Kingdom
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John Curl's Blowtorch preamplifier part III
Apogee Acoustics Scintilla: Impedance a measurement of the true horror of the scintillas. You want to own them just to have an excuse to build a monster amp that can handle them (or is that just me?)


Of course the original full range was even worse


Bass Panel = 1.86 ohms
Midrange Ribbon = 0.14 ohms
Tweeter Ribbon = 0.88 ohms


From the factory the mids had a transformer, but meh, real men can driver that
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Old 3rd December 2019, 12:35 AM   #31098
Max Headroom is offline Max Headroom  Australia
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Can anybody measure R/C/L and RF characteristic impedance of say 3m length of Cat5 wired as four parallel pairs (speaker cable) please ?.
Thanks in advance.
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Old 3rd December 2019, 12:38 AM   #31099
RNMarsh is offline RNMarsh  United States
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Quote:
Originally Posted by syn08 View Post
Free lesson:

You are welcomed.

P.S. 2SK1340 is a transistor that is ridiculous to be used in such a power amplifier. It has 100W maximum power dissipation, Icmax=5A and Vdsmax=900V

Thank you all. So. we are back to what i said in #31055 and 31059.

Exicon Lateral MOSFETS - Our Product Range

The dual device/package.


THx-RNMarsh

Last edited by RNMarsh; 3rd December 2019 at 12:44 AM.
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Old 3rd December 2019, 12:41 AM   #31100
Mark Johnson is offline Mark Johnson  United States
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John Curl's Blowtorch preamplifier part III
I enjoy the Pass Labs reaction: meh, use 1 pair of vertical MOSFETs per 30W rated output, just pay the money and you get the reliability. And your reputation isn't soiled by field failures & angry (ex)customers.
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