AR2,AR2 said:
I am not sure in understand, please explain.
AR2 said:I did had a brief listen at BAF but I wouldn't take that seriously. Now I had it set up and I had my X BOSOSZ to compare to. It is unbelievable difference. Do not take me wrong - I still like my X BOSOZ, but I was just speechless once I heard amount of top detail from Pumpkin. I was amazed how come that I didn't miss all that detail before? I do not know but it is like Pumpkin has opened whole another dimension on the top of the spectrum. It is very detailed and bright amp. When I say bright not in the negative way, and amazingly there is still very strong and deep bass.
My pumpkin is still based on make shift XBOSOZ power supply while I am waiting for Shanty boards. This pumpkin has special value! It was constructed by Choky, Anatech, Magura and myself. I am afraid to change it since it might loose its international flair.
There is a special shielded wire that Magura and Anatech called Wire from Hell, but they still succeeded in completing it for the BAF.
I will be trying different caps in output to see how it will affect sound. I would strongly advise to try this preamp for F4 or any other amp. It is just unrealistically good.
[/B]
That is one glowing rave
Dinesh
ZenMod, I know that you can't remember the open loop gain / close loop gain, of the circuit, but is it possible that it can be explained howto calculate it.
The thing ís, that maybe somebody want to increase the gain, which is 100k / 10k = 10x of 'standard' circuit (R1, R3, R5, R6) give's this gain. I increased the 100k(R5, R6) to 147,5k, and decreased the R1, R3 to 6,8k giving me approx. 20x of gain... eg. the
swings around 40v with an input of 2v in my case.
I can't remember the excact, 'max' voltage which the F4 can handle... But if one look forward to attach, an not so gain-strong phonostage perhaps, giving out.. say 1v, the F4 will only be feeded with 10v on standard, and around 20v in my setup... If the F4 need's... let's say around 25-30v for full throttle, the thing is still missing something to drive it to the max.
I know, that all such adjustment's has a backside, but i hope you got my idea, to conclude the stuff in the revissed cooking-book, BUT this is just an idea i have.
My DAC, gives around 1,6v out, so i think my setting's on is perfect for that, giving around a voltageswing of 34v (16v on standard )...
Jesper.
The thing ís, that maybe somebody want to increase the gain, which is 100k / 10k = 10x of 'standard' circuit (R1, R3, R5, R6) give's this gain. I increased the 100k(R5, R6) to 147,5k, and decreased the R1, R3 to 6,8k giving me approx. 20x of gain... eg. the
swings around 40v with an input of 2v in my case.I can't remember the excact, 'max' voltage which the F4 can handle... But if one look forward to attach, an not so gain-strong phonostage perhaps, giving out.. say 1v, the F4 will only be feeded with 10v on standard
, and around 20v in my setup... If the F4 need's... let's say around 25-30v for full throttle, the thing is still missing something to drive it to the max.I know, that all such adjustment's has a backside, but i hope you got my idea, to conclude the stuff in the revissed cooking-book, BUT this is just an idea i have.
My DAC, gives around 1,6v out, so i think my setting's on
is perfect for that, giving around a voltageswing of 34v (16v on standard )...Jesper.
ZM, anybody,
C4/C5 & C11/C12 are the output caps, I know you have said use your fav. But, I do not have a "fav". I am thinking of using
Black Gate N 47mfd 50V available in partsconnexion for $10, bypassed with 1mfd Vishay MKP 416-420 available on Digikey for a buck.
Why 47mfd? Well, my pumpkin will also be doing double duty of a headphone amp. I thought a larger cap will help with lower impedance cans. Or is this not a good idea?
What do you guys think of this choice? Any other suggestions?
Thanks,
Dinesh
C4/C5 & C11/C12 are the output caps, I know you have said use your fav. But, I do not have a "fav". I am thinking of using
Black Gate N 47mfd 50V available in partsconnexion for $10, bypassed with 1mfd Vishay MKP 416-420 available on Digikey for a buck.
Why 47mfd? Well, my pumpkin will also be doing double duty of a headphone amp. I thought a larger cap will help with lower impedance cans. Or is this not a good idea?
What do you guys think of this choice? Any other suggestions?
Thanks,
Dinesh
lykkedk said:
lykkkkkgreedydanske
it's hard to please everyone ;
with phono section as that - you can't have all ;
I told you before - you can't go near OLG without sacrifices , just beacuse everything is matter of compromises ;
near OLG , you loose both freq extremes ( not that both are necessary)
what you also loose is amount of X feedback ;
anyway - it's up to you to choose what's best for your ears
in your boots - I'll toss both
and F4 ( as a gift to Magura , just because he doesn't have them 
) and make one nice toob system ...........
anyway - for test - desolder feedback resistors and measure OLG at 1KHz ; you can measure also OLG at 20Hz and 20KHz , while you are at it . I'm sorta short in time , because it will take few mnths that I make my own
; all I have in this moment is just one populated Shunty pcb.let us know what results are
regarding calcs - I remember that my calcs aren't very near measured ; I'm primary toob guy - used to graphs and rulers ,along with calculator ; there must be something I missed for OLG calculus .... those dreky mnfctrrs of 3-7 legged fuses make so small and useless graphs
dviswa said:
Dinesh ;
you package ( +
) , along with others is packed and ready to sending ;I just kissed closed doors of post office today ;
seems to me that you found your fave caps
just go for it .
somewhere - in one of my useless OT threads - I mention that I tried
with cans - with stock (4uF) output caps , cans's impedance was ...... both channels in parallel - so must be no more than 50 ohms........ to cut a ... sound was pretty decent , no flabbyness ....... blabla
think about decreasing output resistors to ~ 22E , from 47 as they are now ;
if needed - we can later try something simple - increasing Iq in output stage(s)
don't forget to take cans off the head , if BG's need little burning in
Zen Mod said:
you package ( +
Thanks a lot.
Thanks, I will.Zen Mod said:seems to me that you found your fave caps
OK, anything else I should be changing?Zen Mod said:somewhere - in one of my useless OT threads - I mention that I tried
to cut a ... sound was pretty decent , no flabbyness ....... blabla
think about decreasing output resistors to ~ 22E , from 47 as they are now ;
Zen Mod said:if needed - we can later try something simple - increasing Iq in output stage(s)
don't forget to take cans off the head , if BG's need little burning in
I was wondering about it too. Let's say I want to double the Iq, what values should I be considering?
dviswa said:
roughly speaking .........
halving all mosfet source resistors ;
so - R11 & R16 to 15~18E , R12/R26 & R17/R28 to 330//240E (all that in Pumpkin)
so - that also need changes in Shunty - besides xformer capable to give ~ 82Vct/800mA minimum for stereo , all heatsinks twice thermally capable ( that applicable for Pumpkin too ) and decreasing R7/R7a to 2E4 (Shunty)
in that case you'll double present current hunger
of Pumpkin/Shunty combo , which is ~140mA/channelso - you'll have preamp drawing 82V x 0,28A x 2 =46VA ......
more than some hifi DrekMKXX SE^2 amps
This is not a problem... no difference between soundsonics of 10xgain and 20xgain
Actually, i am not having trouble, with the gain anymore, it was just an idea i have, that maybee someone else was gainhungry like me
too ! ... I allready adjusted the gain to my need's... I see ofcause that the phono-pre, can't be playing as loud as i would like it to, with a gain of 20x, but it's good enough for now.I realise, that this is not the right place to ask, about howto calculate such thing's as X-feedback OLG, CLG... etc... seem's that anyone else but me, understand's this.
I am going to study these technicue's in future... regarding gain/loop etc... that i don't understand quite well... And maybee (can't promise) i will try the meassuring ZenMod suggested.
Anyway, in next few day's.... sneakpreview of my
inputselector 
Greeadylykkedk.... yes i am
Jesper.
oh I do feel good playing OT with Mr OT himself.....apologies
1. yeah the buzz is with shorted and open inputs
2. buzz stops when switch is flicked off
3. can't measure any ac with dmm it only goes to 3 decimal places on 2v setting, i.e min reading is 1 mv.
4. spks are 96db average , which is why its probably annoying........
I'll get the scope out tomorrow and move stuff around.....seriously, I didnt mean to take your thread OT but thanks for sticking with me....
regards
Ed
1. yeah the buzz is with shorted and open inputs
2. buzz stops when switch is flicked off
3. can't measure any ac with dmm it only goes to 3 decimal places on 2v setting, i.e min reading is 1 mv.
4. spks are 96db average , which is why its probably annoying........
I'll get the scope out tomorrow and move stuff around.....seriously, I didnt mean to take your thread OT but thanks for sticking with me....
regards
Ed
patience mon brave, nothing is fitted in that pic, its all just resting in free space......I just took the pic to show the orientation that works.....
btw we don't have tuna tins that large(well maybe we do but I havn't seen one)...but I'm going to mount the tranny on a bracket in roughly the same place it is shown and turn the ps board round 90 degrees where is has more room.........its not artistic, but hey it works
this is what it looks like when lying flat on the floor in the middle
btw we don't have tuna tins that large(well maybe we do but I havn't seen one)...but I'm going to mount the tranny on a bracket in roughly the same place it is shown and turn the ps board round 90 degrees where is has more room.........its not artistic, but hey it works
this is what it looks like when lying flat on the floor in the middle
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