Preamp ideas for F5

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juma

juma

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Joined 2005
evanc said:
...In the schematic the source of the 2sk170 is hooked throughout the potentiometer to the drain of the 2sj74...
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Hi Evan,
your interpretation of the schematic is wrong (JFETs are drawn as if vertically mirrored). P1 is attached to Sources of both JFETs. In order to work, P-channel JFET needs its Drain to be more negative than its Source (and vice-versa for N-channel JFETs).

Google for : "Erno Borbely JFET frontiers"
It's two-part article that will help you understand and use JFETs
 
juma

juma

Member
Joined 2005
evanc said:
...Will this circuit run on 10vdc.? Could i decrease the values of r4 r5 r6 and r7 to drop less voltage there?
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I suppose you mean +/-10V ? You have to precisely describe the circumstances...
As you see, the F5 runs on approximately +/-24V. That's why there are 7812 and 7912 regs to lower the voltage to +/-12V. If you want to use the preamp in the same box with F5 why would you want to supply the preamp with "10V"?

Please be more descriptive if you expect meaningful answers...
 
E

evanc

Member
Joined 2009
Sorry for being too brief, doesn't everyone know all about my system and what I want....? I am thinking about your preamp in the chassis with my DCB1. That runs on +/- 10 volts. I only want to amplify one source that is why I am not thinking of the installing with F5. Anyway thanks for putting up with my lack of knowledge. I'm trying, Really I am....
 
oneplustwo

oneplustwo

Member
Joined 2009
evanc said:
Thank you. I try....
Click to expand...

Do you just love your job? I would imagine it's very satisfying. But also very hard to have someone else take your stuff away!

Back on topic, I'm planning on finishing my DCB1 about the same time I finish my F5. I also have an LCDuino (Amb/Linuxworks) attenuator that might just be a passive solution since it sounds like the DCB1 may not be necessary. I'll try them both and see for myself!
 
E

evanc

Member
Joined 2009
yes, I do love my job....but it is still a job, and only about 1/4 of the work is even worth photos...how many plywood boxes can you get excited about?

I find my f5 dcb1 combo plays loud enough with the cd player and phono, but the ipad/ipod lack drive. This preamp Seems easy enough to implement as an add on.
 
6L6

6L6

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Joined 2010
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Juma, (or other knowledgable people) what is the best (useable?) Idss range of the Jfets in the post#53 schematic?

Also, what happens if the value of the volume potentiometer goes up? Say 50 or 100k?

This circuit is very intriguing. Looking forward to trying it out. (Although I need a handful of j74...)
 
T

TB

Member
Joined 2004
Post #18

Hello, in post #18 by lineup is a mention of use OPA2134 op-amp. Can I use CMoy head amp schematic for this purpose? I use very short patch cables in my system ( 0.5 meters ). Would it be necessary to add buffer or change gain of the (CMoy)amp?
Thanks
 
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