FirstWatt J2

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Zen Mod

Zen Mod

Official Court Jester
Joined 2003
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massimo said:
If you want to mod the Aleph J, why not replace the bjt CCS too (and get rid of the noisy zener) for the input diff pair and replace it with a simple jfet (Idss 10 mA) as Nelson did in the BA-1 and BA-2 front end?
Click to expand...

why ?

two bjt CCS in Babelfish J is superior to led-bjt CCS in Aleph J , but you can't hear the difference .
 
Zen Mod

Zen Mod

Official Court Jester
Joined 2003
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Paid Member
massimo said:
'cause is simpler, isn't it?
Than, no more noisy zener and cap that can create a turn on bump if too big.

Led-bjt CCS? Where? Not in the Aleph J schem I know. Could be interesting anyway.
Click to expand...

mea culpa - it's zenner-bjt CCS ;

anyway - in that position - you can hardly hear differences between zenner-bjt , led-bjt , zenner-mosfet , two bjt CCS-es ;

difference will be in nature of temp behavior of these , output offset-wise , but certainly not in sound ......... just because every of these CCS iterations is "good enough" .

10uF across zenner in Papa's J is same as 1uF , noise wise . and there is no audible difference in power on thump with or without it .
 
Zen Mod

Zen Mod

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R

rickmcinnis

Member
Joined 2006
Crossover question for use with J2

I suspect this question is directed to Mr. Pass,

I am using one of Dave Slagle's autoformer attenuators on the TAD 4001 past of my speakers.

I am thinking about using a configuration that will present an apprx 40 ohms load to the amplifier.

I cannot imagine it making a difference but thought it best to ask to be sure that this will not result in something going wrong. Forgive that I asked a version of this question before but for a much lower load than this.

If given a choice between a 40 ohms load and an approx 12 ohms load, along with the approx 8 ohms load of the sub 500 hz horn, would you tend to think one would be preferred by the amplifier over the other? It would be nice to be able to use much less capacitance with the 40 ohms version!

Thanks for your patience AND the amplifier. Hope to have installed this weekend.
 
R

rickmcinnis

Member
Joined 2006
THANKS again

The autoformer is being used for 12 dB of attenuation, though it has tremendous flexibility if more or less is needed.

Thanks for the reassurance. Did not want to something stupid to the amp OR delude myself that all is well when it may have been causing strange misbehaviors. (Always embarrassing)

First factory amp I have bought in twelve years.

Couldn't resist ...

please ignore the strange spelling in the title, cannot fix it
 
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rickmcinnis

Member
Joined 2006
I was speaking of a speaker level auto-former

used to attenuate my "over 500 hz" speaker bvy 12 dB. Using a shunt resistance at the prmary to result in the amplifier "seeing" an approx. 30 ohms load. This has the happy consequence of usin less capacitance for the first order filter.

I wondered if this high impedance load would present a problem to the amplifiers output. I did not think it was likely but wanted to be sure.

I suspected Mr. Townsend thought I was talking about a volume control instead of a speaker level attenuator.

Just to be clear.
 
H

HVfanatic

Member
Joined 2008
So checking this thread:

Nelson, did your famous J2 arrive at your expected commercial numbers???

If so, I would be very pleased to see the full schematics. If you leave out the values, it would nevertheless be very interesting, what you took, and which parts to use on which position... (maybe with some of your valuable comments...???)

If we still have to wait, may give us a number 373 of 450... I'm so impatient like a little child...

On the other hand, looking forward to the semisouth devices (MAGURA!!!) I may build the circlotron with them.

Let's see.

Dirk
 
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