SemiSouth power Jfets .......... FW J2

[Zen Mod]

or ....... or ........ or ......

I'm pretty sure that mine diminishing returns point is much sooner than yours

[generg]

We do what we can and you do what you can.....Together we are crazy.....

[Zen Mod]

naah ...... I'm just lurking and leeching around:buehehe:edit :useful book ?

[generg]

Very nice book better than the power amplifier book from Douglas Self that I had! Ten points for Serbia!

[Zen Mod]

........ to serve and protect

[sp300b]

All Power resistors replaced with 0,33 (made in USA - 1 % - black ) in the following mannerUpper - 0,165 OhmsLower - 0,68 OhmsBottom - 0,33 Ohms.Too late to listen music right now.Will report tomorrow about (if any) change,So far, only noticable change is a "" during Power On on right channel (that's little strange ...bias and offset checked before without and with test loudspeaker and offset is steady on around + - 10 mV).Music tested and it's playing on both channels.5 points for generg for reporting test results today - 3 points to ZM not telling us about this game (change the resistors)

[Zen Mod]

.....

- 3 points to ZM not telling us about this game (change the resistors)

ZM & sp300b = Oliver Mlakar & Jovo Stevo Karapandza

[sp300b]

Homework for tomorrow:

why-use-the-kimmel-mu-stage

Good night.

[Zen Mod]

I edited your link - from some reason it was messedanyway - translate this :Svaki Cigo svoga konja hvali ........

[sp300b]

Edited Your edit :sarcastic_hand:Each Gypsy praises his horse

[Zen Mod]

just finished reading commercials

anyway -- better reading is How to gain gain_A Reference Book on Triodes in Audio Pre-Amps.pdf from Burkhard Vogel

as I see it - that's classic mu follower stage , where both SS Jfets can be objected with their respective source resistors as two identical active elements , where value ( say - equal ones , for start) of source resistors are chosen mainly in role of transfer characteristic shaper ;

then "drain " resistor of lower SS ( or lower resistor in centre of totem pole ) is used as core of modulation apparatus for upper half of mu-follower

changing values of these three (groups of) resistors will lean transfer characteristic of upper part of mu-follower output stage to more "triode like" or more "pentode like"

there is also fact that - when decreasing value of lower SS source resistor - we must decrease value of it's respective LTP drain resistor , that way also altering value of OLG of entire amp ........ that way altering amount of NFB ...... that way altering slew/rise/damping factor/etc. ; so - differences are mix of several various factors

in any case - matter of preference , same as bunch of ppl divided in odd vs. even harmonics thd spectra liking/willingness to bear with

I know some who are fans of disconnected Aleph CCS modulation , same as I know some who can't even think of that ( I'll not mention some who aren't able to bear Aleph style amps at all , even if they were willing to flip entire A amp in polarity , from some reasons - somewhere in dark ages )

conclusion - feel free to play with amount of upper part of u-follower contribution , same as nature of transfer characteristic of OS of amp ........ but don't expect others to follow you blindingly in those deepness of twisted pleasure

[AR2]

All Power resistors replaced with 0,33 (made in USA - 1 % - black ) in the following mannerUpper - 0,165 OhmsLower - 0,68 OhmsBottom - 0,33 Ohms.Too late to listen music right now.Will report tomorrow about (if any) change,So far, only noticable change is a "" during Power On on right channel (that's little strange ...bias and offset checked before without and with test loudspeaker and offset is steady on around + - 10 mV).Music tested and it's playing on both channels.5 points for generg for reporting test results today - 3 points to ZM not telling us about this game (change the resistors)

Guys, I have been busy these days, little bit fried on Friday night. I have been reeding these findings with the great interst, but I have to admit, I am loosing you on this. Could we please use the nomenclature used on the board - instead of upper - lower, lets use R... Than everyone can easily look on schematic and find out exactly what we are taking about. Sorry I am a bit slow Best

[sp300b]

Guys, I have been busy these days, little bit fried on Friday night. I have been reeding these findings with the great interst, but I have to admit, I am loosing you on this. Could we please use the nomenclature used on the board - instead of upper - lower, lets use R... Than everyone can easily look on schematic and find out exactly what we are taking about. Sorry I am a bit slow Best

Hi AR2, Sorry. It's counting 3W resistors values starting from Plus Vcc to Minus Vcc. There are 3 of them.Upper - Connected to Source of JFet conected to Plus Vcc = R29Lower - Connected to Drain of second JFet = R30Bottom - connected to source of second JFet = R31

[sp300b]

R29 = 0,165 OhmR30 = 0,66 OhmR31 = 0,33 OhmListening to above configuration I think that the things changed in the wrong direction.Bottom frequency part are seems to me less impressive now, and on other hands offset seems to be more unstable now.My Conclusion - Go back and setR29 = 0,33 OhmR30 = 0,66 OhmR31 = 0,33 OhmThis way most probably, CNY-17 Tracking will do better, Both SS will work with equal Source resistors (means whatever is happening good/bad it will happen in the same manner on both of them), and at the end previously tested combination ofR29 = 0,33 OhmR30 = 0,5 OhmR31 = 0,33 Ohm already sounded the best among the tested combination. OK, I have replaced all the resistors with this last change, but I don't think the resistors type made difference itselfAgree with ZM, most probably it's only a matter of taste (pardon, ears)

[Zen Mod]

that means - approximately - pretty much same amount of modulating upper half of mu - follower (as before any change) , while you decrease somewhat source degeneration of both output Jfetssama si to trazila Baby ........ sto bi rekao Djura u skecu "Locvac na Jelene"- moralo se probati :crazyrocker:btw :

....Agree with ZM, most probably it's only a matter of taste (pardon, ears)

...... my ears are always tasty

[sp300b]

Game Over ! :sporty095_2:R29 = 0,33 OhmR30 = 0,66 OhmR31 = 0,33 OhmVoltage over R30 = 1,20 V ==> I bias = 1,8 A => Offset deadly stable Sound....as expected to be.Gorgeous everything.:beach:Bolje, zdravlje !p.s. ZM - MOX not needed now.

[generg]

please sp300b a little tiny mini description what changed to your earsI will hear again with your values.

[sp300b]

please sp300b a little tiny mini description what changed to your earsI will hear again with your values.

Ears remained the same :sarcastic_hand:Sound wise, seems to me that middle range is more opened and it is more proper balanced in comparison with bass and highs, as I think this is how it should be. Sound stage is more robust and low frequencies are more "easy driven" now. All in all, I think this is what You experienced writting down about Your 0,25 Ohm changes.I don't have 0,25 Ohms to try...but should be somewhere around this. And as ZM explained - in order to have proper tracking CNY 17 must have over 1,2 V on his input....

[Zen Mod]

[generg]

Obvious difference is only in output stage where Pass is using 1,4A and Big resistors of 0,47Ohm (two in parallel). Maybe this makes a difference. I will test BJ2 with lower bias and lower output resistors, for sure, soon...

sp300b are you sure? Less current is astonishing and the tracking or the optocoupler with these low values? .....

[sp300b]

sp300b are you sure? Less current is astonishing and the tracking or the optocoupler with these low values? .....

Not really sure. From the picture, clearly, there are 3 x 2 Power resistors. Who knows how those 0,47 Ohms are connected - parallel or serial ?1,4A could be a sweet point, but generally for class A mosfet bigger is better. Papa Heatsinks on J2 are not capable to provide more than 80 W dissipation per channel. I think that's why he is using 1,4A.Probably will try the same setup with lower bias, but I have to play with resistors in order to put them back in order to be able to set lower bias.From Your experience, seems 1,4 A and 0,25 Ohms are also very good. I could try 3 x 0,33 Ohms...with 1,4 A....Uhhh,,,,game seems not to be over....

[Zen Mod]

some local fucker tried to post schematic on big diya

http://www.diyaudio....tml#post2395204

now - I'm going to delete all important schematics in thread ( meaning on those "almost finished " and finished) ........ and it will be available only via e-mail