Pumpkin preamp - More Boring Making Thread

Zen Mod · 2007-11-10 11:21 pm

steenoe said:
Me? Ya talking to me?, I am right here Just received the package today and those boards are way to nice to destroy with any solder stuff In fact they are so nice that I doubt that I can part with the set that you are supposed to have I also doubt that you have a bigger pcb collection than mine, I always order 2 sets of boards, one for building, one for collecting I am not getting slow on the trigger, I just wanted (for once) to see how you guys would do on your own That is not goin' too well, to say the least..... He-he...
On another note, thanks a lot to the Dynamic Serbian duo for offering these finely made boards to us starving DIY'ers. They are in fact, magnificent work. Just superb

Steen

if you insist - jormajj found before me what numbers for heatsinks are adequate ,at usual vendors :

Fischer
SK81-50 SA
SK75-50

Austerlitz
KS100.3-50
KS32.1-50E

ya realy like them?

just don't loose eeny weeny parts

Zen Mod · 2007-11-10 11:38 pm

Originally posted by steenoe

Not a chance

Me?, I will swap the 310 thingies with some Toshiba 2SK369V's.
Why?? Just because I have them

you'll have trouble with pinout

and lookout from highish input level

jacco vermeulen · 2007-11-13 7:47 pm

Let's hope the guys at that forum handle Germanium better you, yea Sheetness.

Me sez : "like MKIII", also shunt type, but not the same.
The MKIII also has regulators on the amp boards, like CTC deepthroat.
Shunty good enuf for me, 8 of them.

lykkedk · 2007-11-17 12:19 pm

Hi... And nice weekend to all here...

Official making thread... I allway's like looking at picture's, so here is one more from me.

I am making final assembling of complete :Pumpkin:

. On picture both my newly 'designed'

inputselector + toslink-switch (To switch between 2 digital sources) is to be seen. Right at picture is a dual +5vdc PSU (1 for toslink thing's, and the other for turning relay's on/off)

My inputselector is made completly foolproof (NO COMMENT HERE PLEASE

). One(Me) can switch between 3 RCA input's (sry. ZenMod for not making it complete balanced), and 1 balanced input.

The 3 RCA (unbalanced) input's, also closes the -in connection, on both sides of 4deck alps pot. When balanced in is choosen, the -in connection opens up for that signal too. This is controlled by a normal 4positions rotary selector.
Normally i will use balanced out, but also here i made a switch, which are going to be placed on back of :Pumpkin:

to switch between balanced/unbalanced out.

Just diden't tried it yet... maybee tomorrow ... but have to go now ...

Jesper.

Zen Mod · 2007-11-18 7:59 am

lykkedk said:
Please stop all that O.T. guys... hehe let's get back into battle ...

Anyway, this might be a dumb quistion, but i just got a thought about shortning -out, when not in use, is it ok to short -out to gnd ? or should it just be left 'open' ???

Please bare with me!

Jesper.

short it

lykkedk · 2007-11-18 8:59 am

short it

Thank's man... Actually i just tried it.

If i feed :Pumpkin:

with 2vac sine, then 30vac sine come's out unbalanced, with -out 'open'... with -out closed, it spitzz out 45vac sine... that's a big difference...

JUST don't understand why ??? but nevermind... it work's fine.
I make this unbal/bal selector, so that i got possibility to use with other amp's than my F4...

Jesper.

Zen Mod · 2007-11-18 12:22 pm

lykkedk said:
Thank's man... Actually i just tried it.

If i feed with 2vac sine, then 30vac sine come's out unbalanced, with -out 'open'... with -out closed, it spitzz out 45vac sine... that's a big difference...

JUST don't understand why ??? but nevermind... it work's fine.
I make this unbal/bal selector, so that i got possibility to use with other amp's than my F4...

Jesper.

it's easy to understand - you always need two points to establish any voltage difference ;
with one leg open , you have gnd somewhere, but not really where it need to be ;

when you ground one of outputs ( you know - you can choose which leg you'll ground :devilr:

) you have established both points , needed for current flow......

be careful - using :Pumpkin:

with F4 oriented gain setting - with other amps

carpenter · 2007-11-18 5:29 pm

Zen Mod said:
it's easy to understand - you always need two points to establish any voltage difference ;
with one leg open , you have gnd somewhere, but not really where it need to be ;

when you ground one of outputs ( you know - you can choose which leg you'll ground ) you have established both points , needed for current flow......

be careful - using with F4 oriented gain setting - with other amps

So, the pumpkin does single-ended out. I thought it might, but forgot where I read, or forgot to ask.

Just remember to ground one of the outputs. Check.

If this is supposed to be an inverting amp, do I gound the negative out?

Zen Mod · 2007-11-18 5:47 pm

carpenter said:
So, the pumpkin does single-ended out. I thought it might, but forgot where I read, or forgot to ask.

Just remember to ground one of the outputs. Check.

If this is supposed to be an inverting amp, do I gound the negative out?

where is the fun if I tell you everything?

:clown:

just imagine xformer instead of :Pumpkin:

; both prim and sec CT-ed .

:rofl:

lykkedk · 2007-11-18 6:11 pm

it's easy to understand - you always need two points to establish any voltage difference ;
with one leg open , you have gnd somewhere, but not really where it need to be ;

Woow... ofcause ZenMod... easy to understand, i also know that about floating gnd, but didn't just think of it in this case. I don't know why, but sometimes it's difficult to me to understand thing's in other perspectives than the one's i used to work with...

This is a very good explanation ZenMod, thank you for that.

Jesper.

Manu · 2007-11-18 6:27 pm

Sasha,
I wan't some of these hudgely hugly pcbs too.
Excitement not any more under control.
Pada li snijeg un srbiji like in Betsch?

:clown:

Monkey face

carpenter · 2007-11-18 6:30 pm

Zen Mod said:
just imagine xformer instead of ; both prim and sec CT-ed .

Yes, that's a great analogy.

But what trips me up is which secondary tap to use if I want inverting. We've got + and - inputs and probably only want a + out relative to ground. I think. So my mind tells me to ground the negative tap.

lykkedk · 2007-11-18 7:02 pm

ZenMod:

be careful - using with F4 oriented gain setting - with other amps

Hmmm... Actually i am having BIG problem driving my LeachAmp with :Pumpkin:

... I must say that i never tried it before i attached my inputselector... hmmm donno right if that's the problem ... will learn more next few day's i guess ... it's irritating but fun too

....

I attached my LeachAmp... and the inputselector/pumpkin is a GIANT disortion machine.... GREEEAT hummming reallly great!

I haven't yet tried the :Pumpkin:

with my dreky inputselector and my F4... btw.

Will tell, about problem in few day''s...

Carpenter:

But what trips me up is which secondary tap to use if I want inverting. We've got + and - inputs and probably only want a + out relative to ground. I think. So my mind tells me to ground the negative tap.

I am pretty sure, it dosent matter... but anyway i would choose to gnd the -out...

Jesper.

carpenter · 2007-11-18 7:39 pm

lykkedk said:
....i would choose to gnd the -out...

Jesper.

Thanks for that. Even though I haven't a solid idea as to why, it just seems to make intuitive sense to have a + out relative to ground.

Zen Mod · 2007-11-18 7:46 pm

Zen Mod said:
where is the fun if I tell you everything?

just imagine xformer instead of ; both prim and sec CT-ed .

carpenter said:
Yes, that's a great analogy.

But what trips me up is which secondary tap to use if I want inverting. We've got + and - inputs and probably only want a + out relative to ground. I think. So my mind tells me to ground the negative tap.

take literally what I wrote ;

if you want absolute phase in puritan way then ground + output and use - as main one .

Zen Mod · 2007-11-18 10:59 pm

carpenter said:
When you say, "absolute phase in puritan way", do you mean that preamps don't invert, or they do invert?

It can get complicated very quickly if one has many amplifiers that invert, or don't invert the output signal. Do most amps invert?

woodie - it's not hard to me that I repeat some thing 1000 times , but you must learn to trust own eyes more ......... :clown:

you have + and - inputs ;
you also have + and - outputs ;

they are labeled in that manner with purpose

so - if I wrote drek on forum - because I'm tired or because my brain is in red ......... trust to your own eyes ;

on input ground "-" leg , and use it unbalanced

on output ground "-" leg and use it unbalanced

in that case absolute phase is correct, not as I wrote previously .......

what I meant with previous post (where I wrote that you can ground whatever you want ) is exactly that - ground whatever you want and have phase as you wish .........

:clown:

carpenter · 2007-11-19 12:51 am

I'm currently operating a balanced, bi-amped stereo.

In the interest of economy, I wish to use unbalanced F4 for treble horns.

I wish to use mono balanced F4 for midbass units (dual 12" Eminence per channel) where I can use more wattage.

I've considered using Pumpkin for midbass F4 where I can use the extra gain. For the treble, I can use the electronic crossover, or my xbosoz.

You can see where operating balanced with unbalanced configurations can become confusing.

mpmarino · 2007-11-19 4:28 am

In the interest of economy, I wish to use unbalanced F4 for treble horns

Why not look at the Babaleph J for the horns?

carpenter · 2007-11-19 4:46 am

mpmarino said:
Why not look at the Babaleph J for the horns?

Darn good question. Tell me more.......

mpmarino · 2007-11-19 5:09 am

carpenter said:
Darn good question. Tell me more.......

There's only so much I can say. Nelson's Aleph J or Choky's Babelfish J (almost the same) are both balanced topology. You could probably build yourself a nice 'mini' and keep the whole shebang balanced.

sorry for the OT post

Hey Choky,

Re: fancy pants shunty reg. Is 82v CT tranny the ABSOLUTE MINIMUM for +-36v? I'm seeing what I have 'in drawer'. Greedy boys don't like to spend money

:clown:

edit: Carpenter - my pump boards came USPS registered mail. I had to sign. I see you asked a while back.

Pumpkin preamp - More Boring Making Thread

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