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Old 16th September 2013, 10:53 PM   #1831
OllBoll is offline OllBoll  Sweden
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Thoughts about amplifier gain:

If I've understood correctly in theory the gain of the amp is ( current source in parallel with speaker ) / ( 1/0.4 )

And it is because of this that gain increases with the inductor since the inductor has much higher resistance? Though not massively since the 8 ohm speaker still limits the gain.

So if we simplify and assume that the inductor has a resistance of 100 since we won't use the amp for bass the gain with an 8 ohm speaker would be close to 3 or 9.6 dB if I remember my math correctly.

But that is not what I wonder... what I wonder is that does this mean that if I use an 18 ohm speaker instead the gain jumps up to 6.1, or 15.6 dB?
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Old 16th September 2013, 11:00 PM   #1832
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choke means inductive storage

think twice output voltage , comparing to PSU

meaning - when having resistive or CCS based load part of amp , output voltage amplitude can go just between rails

when having choke - it can go almost twice that

roughly

voltage , same as ground , is elastic term

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Old 18th September 2013, 06:46 PM   #1833
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Quote:
Originally Posted by Michael Rothacher View Post
The input cap is there in Figure 11 in case your SIT has enough gate leakage current to drop some voltage across the input. If you measure the input, and it is at 0V, then perhaps you can go without.
Hi Michael,
I was wondering how to test for gate leakage of your final circuit for the inductor version. If the input cap needs to be there what is the lowest value it could be without affecting circuit if possible.
Thanks,
Eric
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Old 18th September 2013, 06:55 PM   #1834
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You could measure the voltage across Rin (R1) and figure the current. Most of my 2SK82 examples have been a couple of microamps or less.

Does you preamp have AC-coupled outputs?
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Old 18th September 2013, 08:15 PM   #1835
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Hi Michael,
At the moment it is the LightSpeed but eventually I will be using the my B1 which is AC coupled. Oh! I think I see what your getting at. So I won't need the input caps for the L'Amp if my preamp has AC coupled outputs.
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Old 18th September 2013, 08:29 PM   #1836
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Perhaps you won't. Try it. But you'll need a cap in the chain somewhere since the input will not be sitting at or near 0V in that particular case.
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Old 19th September 2013, 01:46 PM   #1837
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Any objections to using a pair of CL-30s on the primarys to protect againt in-rush current? Using seperate transformers for main circuit power and bias circuit.

thanks

Vince
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Old 19th September 2013, 08:09 PM   #1838
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No objections spring to mind.
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Old 4th October 2013, 11:52 AM   #1839
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Here is my SIT Parafeed hybrid power amp manifested in matter.
There are two monoblocks...

UPLSITParafeed.jpg

Last edited by DIYspaceW; 4th October 2013 at 12:03 PM.
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Old 4th October 2013, 01:11 PM   #1840
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more porn , please ..... schm included

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