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Old 26th April 2010, 05:25 AM   #1391
Salas is online now Salas  Greece
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Quote:
Originally Posted by ra7 View Post
Mine is up and running too... first impression is very quiet background and very melodious! Its late here and I can't crank it up. More tomorrow.
And pics please. Never seen the phono also. Gotcha!
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Old 27th April 2010, 03:55 AM   #1392
ra7 is offline ra7  United States
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U got me there man! The phono stage was built on a breadboard and underwent several changes (as u and I know) but then I moved and had to dismantle the board. Since then, I have got my hands on the dl103 and am working on the breadboard again. This time starting with your simplistic NJFET design - the 37V version. I'll post there once I finish it. You know I got the LEDs to work in that design on the breadboard but still messed it up in the B1

Anyway, back to the B1. Its up and running. I haven't finished all the inputs yet and the output is sitting outside the chassis. I'll post pics as soon as I'm done. I listened for a while this evening and it sounds wonderful. Dark, is the first thing that comes to mind. Everything is dark and silent in the background. Also, the bass is so powerful and has plenty of slam and I was quite surprised by this as I already have plenty of powerful bass. Is the shunt supply playing its part here? And the vocals are simply beautiful. All in all, superb sound. I didn't think introducing another component would have such a positive effect, but it did and I couldn't be happier.
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Old 27th April 2010, 05:04 AM   #1393
Salas is online now Salas  Greece
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Quote:
Originally Posted by ra7 View Post
Is the shunt supply playing its part here?
Its the DC coupling and all other stuff carefully married. Was developed as a whole.
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Old 27th April 2010, 10:14 PM   #1394
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Default ...and then I found AndrewT's post #524

Quote:
select Idss to be similar.
The B1 is designed to run the active device at Idss. That requires the CCS device to pass the same or similar Idss.
If you have a pair of 8.15mA and 8.23mA then that is a selected pair. they are within 1% Idss. You could use <2% tolerance Idss. I suspect you could even use <5% tolerance Idss, but I do not know which should be the higher and which should be lower. There are science reasons for NOT running the active device at well above it's Idss but some builders are reporting that they prefer the sound when the active device is running at >100% of Idss. I will ALWAYS run <=100% Idss. I will NOT try >100% Idss.

But, that selection MUST BE DONE at the SAME temperature. This must be checked when both jFETs are supplied and measured at the same time and they are thermally coupled together.
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Old 27th April 2010, 10:20 PM   #1395
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Default which helps me find an answer to these questions:

Please confirm:

The matched jfets are Q5 & Q6 in the schematics of post 874.

From the builder's guide:

"Select the pair to have similar Idss and the lower run then biases the upper one."

Which one is lower? Q5 or Q6? I can install devices with identical Idss. Is it better for one of them to be lower? ...or the same?

...a little more help and we'll be having a beer.
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Old 27th April 2010, 11:34 PM   #1396
Salas is online now Salas  Greece
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Totally matched is best. If one is slightly weaker, then use it as the CCS S&G connected one that goes to B- (That is the one which we call ''lower'' if you view the pair as given schematically).
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Old 28th April 2010, 11:34 AM   #1397
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Good day to all!

To clarify by using the output relay as reference:

The matched jfets are 2 pair labeled "4x 2SK170BL" aligned with middle of the board off the end of the relay.

The "lower", "weaker" of the matched pair is closer to the extended center line of the relay.

Sorry if I am being too analytical.
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Old 28th April 2010, 11:44 AM   #1398
AndrewT is offline AndrewT  Scotland
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Yes, those 4 jFETs are the amplifiers.
Yes, the middle pair are the CCS and the outer pair are the source followers.
If you have slightly lower Idss and want to use them in the CCS position then the middle pair are where you locate the lower Idss jFETs.
Remember to keep the selected pairs together, either the left pair or the right pair.

If you look at the PCB traces you will see the G & S connected together indicating the CCS duty.
Print off the PCB layout, big enough to fill an A4 sheet. Makes it easy to see where everything goes.
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Last edited by AndrewT; 28th April 2010 at 11:46 AM.
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Old 2nd May 2010, 09:16 PM   #1399
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hello,

Salas, I have a question for you or anybody who could help me. It is about the delay start circuit of the DCB1. If I put an smaller capacitor (I actually have a 100uF one) can I make the relay to mute the circuit sooner? I mean when you turn it off.

I need the relay kick in it a bit earlier for a Lightspeed attenuator experiment I am doing with the buffer.

Thank you very much for your help, guys. I really appreciate it.

Regards,
Regi
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Old 3rd May 2010, 12:56 AM   #1400
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Default Done!

Click the image to open in full size.

I'm finally done wiring them up. Is it ok to leave AC ground floating or should I tie it down to something.

Thanks,
JG
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