Nelson Pass said:It really helps if you have any kind of distortion analyzer
for setting this up. There is a specific bias voltage/current/
gain/load sweet spot, and the figures I gave are approximate
due to part variations.
Thank you very much Mr. Pass.
It is realy a great pre.
I'am currently hearing the Folia by Jordi Savall, and there are some Castagnette playing. Trust me, it is so realistic that you could guess out which Wood essence they are made...
Unfortunately I don't have this equipment to test ( Not long ago I ebayed aScope, still learning how to use it).
As for the sweet pot, it is amazing how the changes suggested by Zen Mod made the difference.
But for now I'am very happy.
Please Mr. Pass, may I call you Papa, please just this time.
manuel
Manu said:
if you don't have siggene you can use any sine source you can find ....little pc utils from net,burn that to cd or directly from (presumably dreky ) sound card to DUT..........
then-observing current and voltage across sayed jfet ,crank up volume on input (toss entirely that volume on output) and look for symetrical clipping ;to achieve that ....tweak current through stage and voltage across........
there is yours sweet spot.
regarding Nadija....
is it Nadija or Nadja .........?
send Zdravo to her from Sasha
and-keep that photo away of all these old farts
Zen Mod said:
if you don't have siggene you can use any sine source you can find ....little pc utils from net,burn that to cd or directly from (presumably dreky ) sound card to DUT..........
then-observing current and voltage across sayed jfet ,crank up volume on input (toss entirely that volume on output) and look for symetrical clipping ;to achieve that ....tweak current through stage and voltage across........
there is yours sweet spot.
regarding Nadija....
is it Nadija or Nadja .........?
send Zdravo to her from Sasha
and-keep that photo away of all these old farts
Zrado from Nadija (the i make this name so beautiful - No I am not Breton (wimpy) and she's not Nadja) to you.
I have to thank you very very much for your help.
I will try what you suggested with the scope ( the scope scares me a little - the last time I tested my Aleph 5 with is it ended with 5 blown Mosfets and a nice source resistors light show). May be I will need some help, but you're here no?
Manuvic
Congratulations Manu! Your experience with Jfet Boz will be helpful.
Tonight I just collected almost all the necessary parts...well, I discovered that there's no small 10 ohm resistor in my junkbox. But I have 27 and 22 ohm ones. So I think I am going to use two 27 ohm ones in parallel. I also bought "eau de toilette" I needed just a metal can. And it has a nice aroma!
Regards,
Vix
Tonight I just collected almost all the necessary parts...well, I discovered that there's no small 10 ohm resistor in my junkbox. But I have 27 and 22 ohm ones. So I think I am going to use two 27 ohm ones in parallel. I also bought "eau de toilette"
I needed just a metal can. And it has a nice aroma! Regards,
Vix
Attachments
Hi Vix, it was a great day indeed... Thanks the help of Zen Mod I have found a sort of sweet pot with my system. If a can manage it I could certainly find the ultimate sweet point...
But I am now enjoying...
As Nelson Pass says the pre need a fine adjustement to your system ("There is a specific bias voltage/current/
gain/load sweet spot"), and then, I can confirm it is worth the effort. It is a remarquable pre.
For recall my setup is now:
Source res: 22R
PSU 17 V
May be the 2K2 hare to be adjusted.
Please build it and post your impressions.
manu
PS (Twitchie): Every time I see the name Toronto It reminds me of Glenn Gloud, my master, the greatest Musician ever. Really.
But I am now enjoying...
As Nelson Pass says the pre need a fine adjustement to your system ("There is a specific bias voltage/current/
gain/load sweet spot"), and then, I can confirm it is worth the effort. It is a remarquable pre.
For recall my setup is now:
Source res: 22R
PSU 17 V
May be the 2K2 hare to be adjusted.
Please build it and post your impressions.
manu
PS (Twitchie): Every time I see the name Toronto It reminds me of Glenn Gloud, my master, the greatest Musician ever. Really.
Indeed, thanks for leading the way Manu - I mocked up the circuit with a protoboard to make sure my values were correct and all I'm getting is alot of distortion as well - the music is also present, but at very low volume (compared to the noise).
I measured 6.33V across the jfet and a few others (didn't record them though) - although I'm playing into a LM1875 gainclone for testing ... probably not the best for high-gain circuit.
I'll try other Rs values and see if 22 is the magic number for me too
I'll be sure to post some pictures when I get it running.
Stephen
I measured 6.33V across the jfet and a few others (didn't record them though) - although I'm playing into a LM1875 gainclone for testing ... probably not the best for high-gain circuit.
I'll try other Rs values and see if 22 is the magic number for me too
I'll be sure to post some pictures when I get it running.
Stephen
I found that I could eliminate all the 'noise' but not all the distortion by switching to a 9V battery instead of a cheap regulated supply (LM337).
I also find that the 20K pot I have on the input does not have any effect on the volume
Any ideas? I tried 10 ohm and 20 ohm Rs and going to 10, attenuates the output slightly (is that supposed to happen?)
Thanks in advance
Stephen
Update: I measured voltage across the jfet again and since I switched to the 9V battery, it's very low, so I swapped the 2.2K for 1K and now it's beautifully clear , looks like (as Mr Pass already explained), it will take quite a bit of tweaking to get it right for any given application
Does anyone have a schematic for a very nice and quiet regulated supply? Thanks
I also find that the 20K pot I have on the input does not have any effect on the volume
Any ideas? I tried 10 ohm and 20 ohm Rs and going to 10, attenuates the output slightly (is that supposed to happen?)
Thanks in advance
Stephen
Update: I measured voltage across the jfet again and since I switched to the 9V battery, it's very low, so I swapped the 2.2K for 1K and now it's beautifully clear
, looks like (as Mr Pass already explained), it will take quite a bit of tweaking to get it right for any given application Does anyone have a schematic for a very nice and quiet regulated supply? Thanks
Nelson Pass said:
I wanted to build one analyzer as you guided, but . . .
Will buy one 2nd hand when I arrive home tomorrow . . .
Many new interesting projects here while I have no time till end-year . . .
Half sad, another half happy . . .
I'm leaving China behind 4-year staying. Time is flying.
As usual, bringing only good impressions to my future.
Good bye, Kina . . .
It's getting very late, but I remembered I have Veteran's Aleph P1.7 and took one of the supply boards and jumpered after the third 9.1V zener ...
In summary, it sounds pretty good on the jury-rigged system I'm testing with right now - and I'm back to all stock values, except I have the rail voltage at about 19V and getting about 6.8V across the jfet.
Stephen
In summary, it sounds pretty good on the jury-rigged system I'm testing with right now - and I'm back to all stock values, except I have the rail voltage at about 19V and getting about 6.8V across the jfet.
Stephen
Manu said:
And nobody trust me when I say I am stupid.
Reconnected hot to hot and : Oh Lord!!! This sound. Plenty, full, seductive, and cristal clear.
Danke Meister
Danke Steenoe.
It is realy great.
(But I have to crank the volume allthe way up
manu
Now we are getting somewhere
Nice to see you are making progress. Usually when the preamp is phase-inverting, you will change the phase's at the output of the poweramp to make up for that. (If you think that is necessary).If you have to turn the volume all the way up, maybe the input pot needs adjustment? If this little gainstage has 24dB gain it really should have more than enough gain for a "normal" poweramp. I am still a bit puzzled, does it really have all that gain?
Manu, with your enthusiastic review I think that I will make a quick mockup and connect it to the F4
Mayby a nice little shuntreg is the best thing for this pre's supply. I expect it would result in a very direct and precise sound. A cap-multiplier in front of the shunt is probably in order, this simple thing cant have the largest PSRR in the world.Steen
BTW
Here is a simple Distortion "analyzer" . I didnt build it. I am not sure how usefull it is, but Elliot is usually worth consulting.
http://www.sound.westhost.com/project52.htm
steenoe said:Manu, with your enthusiastic review I think that I will make a quick mockup and connect it to the F4
Steen
Most probably you'll make that quick mockup before I do mine
I'd like to do it this weekend..but I can't promise...
As you probably saw, it will be run out of two 9 v Ni-Mh rechargeable batteries. I measured them and they actually have around 9.5 v. So the pre will be run at about 19 v. I also expect to adjust resistor values. What about inserting a 2 k trimpot in series with, say 1 k Drain resistor, and tweak for best sound? (I don't have a distotion analyzer,my ears will by my guide)
Babowana, I wish you good luck, wherever you're going. By the way, is it going to be a bit difficult to move those big speakers? (it was J-low, right?)
Regards,
Vix
steenoe said:
Now we are getting somewhere
If you have to turn the volume all the way up, maybe the input pot needs adjustment? If this little gainstage has 24dB gain it really should have more than enough gain for a "normal" poweramp. I am still a bit puzzled, does it really have all that gain?
Manu, with your enthusiastic review I think that I will make a quick mockup and connect it to the F4
Steen
BTW
Here is a simple Distortion "analyzer" . I didnt build it. I am not sure how usefull it is, but Elliot is usually worth consulting.
http://www.sound.westhost.com/project52.htm
now we are in R. Johnson's territory ........we trade simplicity of preamp for necessary complexity of PSU
either Noro shunt , sort of super reg , or battery .
battery is least complicated version
Manu said:
Have you tried going back to the initial configuration, now that you have fixed the problem with shorting the "hot" of the two channels?
I think the circuit is intended to have the volume adjustment before - I guess the problem you had with gnd vs hot could have been the one forcing you to have a pot on the output of the preamp.
BTW: Changing the source resistor to 22R should lower the gain to ~22dB, so I guess the problem with turning up the volume is mostly related to the position of your input pot.
You are right about the supply. Just made a quick drawing of the shunt reg and it ended up with more parts than the gainstage
So battery power is the simple solution.
2 normal 9V batteries should do the trick for starters.
I also think that its a very good idea to do as cviller suggests and go back to the original circuit and take it from there
Steen
So battery power is the simple solution. 2 normal 9V batteries should do the trick for starters.
I also think that its a very good idea to do as cviller suggests and go back to the original circuit and take it from there
Steen