Pumpkin preamp - ordered by Steen , official making thread

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#1,064
Magura said:



I know :bawling: but that's all due to my wussy fellow designer, he wasn't up to the task 😀


Magura 🙂
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why you didn't asked ?

either increase current through input LTP , or increase values of theirs drain resistors ........... or slightly decrease source resistors of outputs .....that last is maybe best solution

edit :

ya didn't say anything about sound........ ?
 
#1,068
Zen Mod said:



why you didn't asked ?

either increase current through input LTP , or increase values of theirs drain resistors ........... or slightly decrease source resistors of outputs .....that last is maybe best solution
Click to expand...


It's in the tube for future playing around. As for now I'm waiting for the boards.
I though did some playing around with my previous prototype, and 200mA seems to be the point of diminishing returns.

I can't be bothered to make a birds nest, when I know that boards are coming soon.....and besides that I have other things to play with ATM 😀

Magura 🙂
 
#1,069
For the Pumpkin - assuming the max output cap of 10uF - I guess it will still not be adequate for a headphone with input impedance of 300ohm as the LP filter will still be loping off a huge chunk of the bass.

Thinking of using the balanced output to do double duty to drive a balanced headphone too. I guess the only for this is to add an electrolytic :xeye:

her shann
 
#1,070
hershann said:
For the Pumpkin - assuming the max output cap of 10uF - I guess it will still not be adequate for a headphone with input impedance of 300ohm as the LP filter will still be loping off a huge chunk of the bass.

Thinking of using the balanced output to do double duty to drive a balanced headphone too. I guess the only for this is to add an electrolytic :xeye:

her shann
Click to expand...


you can find decent electrolytics in range 100-220 uF, and you can bypass them with something nice , in range of 1-2u2 ;


just hang them ( electrolytics)on inner side of present output caps , solder 47K from output side of caps to gnd ( for bleeding those big caps ) , connect da cans and enjoy .

as I said - I tried my proto Pumpie with AKG K270 Studio ........ 😉

nota bene - do not forget to power off power amp, when you are in mood for headphones ........ :devily:

naaaaaaaah......

I'm ill like a dog ........ flue almost gets me completely ..........
 
#1,076
Zen Mod said:



you can find decent electrolytics in range 100-220 uF, and you can bypass them with something nice , in range of 1-2u2 ;


just hang them ( electrolytics)on inner side of present output caps , solder 47K from output side of caps to gnd ( for bleeding those big caps ) , connect da cans and enjoy .

as I said - I tried my proto Pumpie with AKG K270 Studio ........ 😉

nota bene - do not forget to power off power amp, when you are in mood for headphones ........ :devily:

naaaaaaaah......

I'm ill like a dog ........ flue almost gets me completely ..........
Click to expand...

Pardon my poor comprehension - so you mean -ve leg of electrolytic to output of film cap and +ve leg of electrolytic to resistor which is then connected to ground. So the electrolytic is not actually parallel to the film cap at all.
 
#1,078
hershann said:


Pardon my poor comprehension - so you mean -ve leg of electrolytic to output of film cap and +ve leg of electrolytic to resistor which is then connected to ground. So the electrolytic is not actually parallel to the film cap at all.
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Your drawing is not excactly correct! The Electrolytic cap must be in parallel with the outputcap. Said in another way; you can replace the outputcap, with the electrolytic (and add the resistor as Mr. ZM said)

🙂

Edit: And bypass the electrolytic with your faverourite filmcap ofcourse😉 I beleive there is provided for that on the Shunty boards...

Edit Edit: I would use at least 220uF, and even that, I feel is too small. I usally go for 1000uF for headphone applications like that.
One good combo that I can recommend is 470uF Panasonic FC bypassed with a 1uF Rifa PHE426 polyprop. At least that is the best sounding "cheapo" combo that I have ever heard😉 Using a smallish cap on the output of a Headphone amp does cut the lower octaves somewhat😉
 
#1,079
Biggest Burleska
Click to expand...

Yup I was trying to be clever. I know that inductance isn't important for DC so my point is that an inductive resistor is actually better in the power supply as it might (theoretically ) filter out a teeny bit noise and ripple. So part of point was that those who would blindly replace resistors with a "better" non-inductive one might be wrong...

I will never try to be "clever " again...promise...
😀
 
#1,080
Variac said:


Yup I was trying to be clever. I know that inductance isn't important for DC so my point is that an inductive resistor is actually better in the power supply as it might (theoretically ) filter out a teeny bit noise and ripple. So part of point was that those who would blindly replace resistors with a "better" non-inductive one might be wrong...

I will never try to be "clever " again...promise...
😀
Click to expand...

Naah, dont think so. First you were right, then you were right again!!!!😀 Use the most inductive resistor that you can find for CRC arrangements"!!!"
You better play "clever" some more😀

🙂
 
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