The 51r I suggest is not in the source connection. They still have the 10r as specified.
The bypass using the VR gives adjustment of the 10r downwards and if taken to extreme one could end up with or as the source resistor.
The extra 51r are in the bypass route in series with the adjuster.
Each half of the source resistor sees 10r alone, or 10r//100r ~ 9r1, or 10r//[100r+51r] ~9r4.
The range of adjustment for the three schemes is 10r +-0r0 (10r to 10r), 9r1 +0r4,-9r1, (9r5 to 0r0), 9r4+0.2,-1r1 (9r6 to 8r3).
Using the VR alone // 10r risks a set up error.
The bypass using the VR gives adjustment of the 10r downwards and if taken to extreme one could end up with or as the source resistor.
The extra 51r are in the bypass route in series with the adjuster.
Each half of the source resistor sees 10r alone, or 10r//100r ~ 9r1, or 10r//[100r+51r] ~9r4.
The range of adjustment for the three schemes is 10r +-0r0 (10r to 10r), 9r1 +0r4,-9r1, (9r5 to 0r0), 9r4+0.2,-1r1 (9r6 to 8r3).
Using the VR alone // 10r risks a set up error.
Hi Tea Bag
I got exactley (yeah I know shuld be similar but exactley sound better) readings
Same again for my Toshiba pairs at similar values to triode.
Insted of answering the question and then get raped by same professor I have asked a question...
Yea go on and close the loop that difference may be ok
Got both (Toshiba and Fairchild) built and altrough both fantastic I preffer the better dinamics of the Fairchilds.
The 2SJ74 sems a bit to hi for BL do you have V grades ?
I got a couple of batches (good one from Blues) and IDS from 6.8 to 10 ma on both flavors (2SJ 2SK) with sligtley lower 2SK IDS across range.
Jackinnj sorry to ear about water. I would realy apreciate your charth
I tried P3 with a 10 turn pot and about 2 turns in got same smoke
so for now I am living P3 off the borads at present
I got exactley (yeah I know shuld be similar but exactley sound better) readings
Same again for my Toshiba pairs at similar values to triode.
Insted of answering the question and then get raped by same professor I have asked a question...
Yea go on and close the loop that difference may be ok
Got both (Toshiba and Fairchild) built and altrough both fantastic I preffer the better dinamics of the Fairchilds.
The 2SJ74 sems a bit to hi for BL do you have V grades ?
I got a couple of batches (good one from Blues) and IDS from 6.8 to 10 ma on both flavors (2SJ 2SK) with sligtley lower 2SK IDS across range.
Jackinnj sorry to ear about water. I would realy apreciate your charth
I tried P3 with a 10 turn pot and about 2 turns in got same smoke
so for now I am living P3 off the borads at present
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Hi
I have ordered a new batch of transistors and will use EUVL's selection method: look for similarities at the datapoints of 0, 5, 10, 15, 25 ohm. [That is the reason for my starting a table].
Will take a few days.
Otherwise I have another trick up my sleeve.
albert
I have ordered a new batch of transistors and will use EUVL's selection method: look for similarities at the datapoints of 0, 5, 10, 15, 25 ohm. [That is the reason for my starting a table].
Will take a few days.
Otherwise I have another trick up my sleeve.
albert
And a good table it is
What trick is it?
Have you tried cascode and parallel J fets ?
I have tried both Papa cascode make realy big improvment IMO well worth it
Paralel Jfets (2 ) maybe not shure F5 is so good that I will need beter preamp
to be able to give opinion about it certanly does not do any vorse.
What trick?
Hi Bksabath
what I think of is
1) adding a current regulator. That is: an auxiliary JFET with source resistance connected not to input but earth, or a J508 (2,4 mA) or so. This should have a 0,5-0,7 Meg output AC capacitance, so won't spoil the low drain resistance. But with the very high bandwidth possible, it is a challenge.
2) cascode to a lower voltage. If I make this variable, I will slightly influence the transconductance. Main advantage I see is that the JFET will have a lower Vds and hence lower heat dissipation.
Should I, when I am finished I post a separate thread with my build, as otherwise the thread is hijacked?
albert
what I think of is
1) adding a current regulator. That is: an auxiliary JFET with source resistance connected not to input but earth, or a J508 (2,4 mA) or so. This should have a 0,5-0,7 Meg output AC capacitance, so won't spoil the low drain resistance. But with the very high bandwidth possible, it is a challenge.
2) cascode to a lower voltage. If I make this variable, I will slightly influence the transconductance. Main advantage I see is that the JFET will have a lower Vds and hence lower heat dissipation.
When selecting the units (using my 4 1/2 DVM) I saw the numbers racing, especially the tests with 0 and 5 ohms source resistance.
A cascode keeps the power on the unit lower; and by a favorite accident increases the second harmonic.
3) I pondered about a trimpot in the source leg of the JFETS, but I am afraid that reduces the transconductance more than the DC current, but I would have to test it. I am not a person of Spicing this type of thing, real life testing with all mistakes is more fun 🙁A cascode keeps the power on the unit lower; and by a favorite accident increases the second harmonic.
Should I, when I am finished I post a separate thread with my build, as otherwise the thread is hijacked?
albert
Sound realy interesting and way over my head (I am more handy with bolts and spanners)
Cascode did make big (audible) improvment for me.
One thing I would do is have a batch of 2SJ to mesure up same or similar to the 2SK.
About mesurament I have noticed that caracteristic change a lot with temperature so I was mesuring to get a range around 7 mA and let temperature/ IDS setle a bit.
For the mosfets I did the mesurament at constant 50 C
Your own F5 tread why not?
Sound interesting enoug IMO
Cascode did make big (audible) improvment for me.
One thing I would do is have a batch of 2SJ to mesure up same or similar to the 2SK.
About mesurament I have noticed that caracteristic change a lot with temperature so I was mesuring to get a range around 7 mA and let temperature/ IDS setle a bit.
For the mosfets I did the mesurament at constant 50 C
Your own F5 tread why not?
Sound interesting enoug IMO
Amazing how much you could change (and mess up) such a simple circuit, I starting to worry on how different my F5 may sound from Papa build, it would be nice to have something like Burning amp over here, so yes try the regulator and report back, it is your electrons you playing with after all.
I am thinking that al secrets are hidden in Papa F5 write up. I read the lot at least 50 times and the filing that I missed somethink is still very much my bitter companion at present, I am really tempted to try artificial means to reach a higher energy level (go to get same more cans of whipped cream) and know that the truth is really out there in plain site and Papa is having a giggle.
Maybe he will take pity on us and came up with another "what did I forgot to post this?" revelation.
Still loads of fun and the chance to be little Kid ready to open the Living room door at Christmas every time I plug a new one in.
Same times you get Aunty Jumper same time a new bike
And the Bike is so much better just because of all the jumpers (swetters)
I already asked for F6 F7 for this Crimbo ....
I am thinking that al secrets are hidden in Papa F5 write up. I read the lot at least 50 times and the filing that I missed somethink is still very much my bitter companion at present, I am really tempted to try artificial means to reach a higher energy level (go to get same more cans of whipped cream) and know that the truth is really out there in plain site and Papa is having a giggle.
Maybe he will take pity on us and came up with another "what did I forgot to post this?" revelation.
Still loads of fun and the chance to be little Kid ready to open the Living room door at Christmas every time I plug a new one in.
Same times you get Aunty Jumper same time a new bike
And the Bike is so much better just because of all the jumpers (swetters)
I already asked for F6 F7 for this Crimbo ....
If you are interested to try something a bit "outa-de-box" with those jfets, try connecting the heatsink to the jfets via a strip of copper so the jfets are sandwiched between the strip (goo and tiewrap) to bring them up to about same/similar temp as heatsink - quite a significant change.
Attachments
Did you ?
Did you X the F5 and tried the cascode?
Or Did you cascode the F5 and it did no make any change?
What flavor mosfet did you use on yours?
Any picture?
Please tell as more.
Be nice to know and share opinions.
I am just getting into the F5. I am actually starting with Juma's version using 2sk2013/2sj313. I have the boards made and hope to wire it all up this weekend. My understanding of the merits of the cascode include; control over main transistors operating condition's (Vds,temperature protection), simple limiting of Miller effect, and with F5 specifically, a convenient place for SUSY feedback at base of BJT. NYCOne has done a write-up on Cascoded - X - F5
right fair enoug
Your opinion that cascode is useful for F5X but not for F5 is based on sometink you have not listened to so far.
IMO cascoded version more micro details less harshness maybe less third armonics at the expense of same gain at least this is what I think I am earing.
Mr miller is there on F5 as well as on F5X
Reduction of voltage same again.
Catch my drift?
Your opinion that cascode is useful for F5X but not for F5 is based on sometink you have not listened to so far.
IMO cascoded version more micro details less harshness maybe less third armonics at the expense of same gain at least this is what I think I am earing.
Mr miller is there on F5 as well as on F5X
Reduction of voltage same again.
Catch my drift?
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yes, a simple way to avoid the mis-setting of the adjuster resulting in damaged components.
I quite often insert a slightly higher value resistor where I see that a parallel trimmer could be useful at a later stage. The 11r works in this case, since it gives a fairly close equal adjustment range either side of the standard 10r.
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hey bksabath, I know its boring repetition, but do you mind posting or telling which cascode you are using
there have been several different versions
Are you talking FE or output or both? With cascode, no Miller effect where it is used.
Tinitus
I beliewe SCH was on this tread sorry I can not find exact drawing but I have posted one much similar also on this tread.
I will look for the one I have used and post link asap
The caps I am using and on SCH "lost" are 220uF
I call it "Papa" cascode.
The other one that I am going to try eventualy is the "Borbelly" cascode
with J fets
I believe you are using the cascode yourself.
What are your impressions on sound?
Buzzforb.
FE ?
Sorry what?
NYCONE write up on Balanced Could you post Link to that please.
I beliewe SCH was on this tread sorry I can not find exact drawing but I have posted one much similar also on this tread.
I will look for the one I have used and post link asap
The caps I am using and on SCH "lost" are 220uF
I call it "Papa" cascode.
The other one that I am going to try eventualy is the "Borbelly" cascode
with J fets
I believe you are using the cascode yourself.
What are your impressions on sound?
Buzzforb.
FE ?
Sorry what?
NYCONE write up on Balanced Could you post Link to that please.
Attachments
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Has anyone here Successfully used this P3 in a F-5, and if so, what were your sonic observations in utilizing it? I'm curious! But the only reports I've seen were from B. sabth who didnt have much luck, I dont want to fry any of my Jfets if possible! Thanks!
Russellc
Russellc