Pumpkin preamp - ordered by Steen , official making thread

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#2,661
Re: Stupid question

njepitt said:


OK, I realise this may be an absurdly stupid question..... I just came back from buying some hardware for putting my Pumpkin together, and was faced with choosing female and/or male XLR sockets to mount on the back panel for inputs and outputs - and looking at them I realised I had no idea which should be used for which.... Now I'm back home I found the post I quoted, which says the outputs (to power amp) should be male sockets, and presumably female for inputs. (In this case from DAC, most likely...) SO: why this way round instead of the other?

(Oh, and apparently I guessed wrong and will have to change some males to females... oh well... )

Cheers

Nigel
Click to expand...

hot/cold or heiss/kalt

same logic as with mains plugs/prongs whatever their name is ;

if XLR is on input side you'll use one with three holes - from sinmple reason that with grabbing it with hands you can't induce any hum or static

that's rule for any case , xlr being on chassis or on cable .

output one is just another one ....... you must remember just input ones as important :rofl:
 

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#2,662
Re: Re: Stupid question

AndrewT said:
for some reason XLR sockets are opposite to the way we do our mains sockets.
Mains output sockets are always female to prevent electric shock.

XLR output sockets are always male and input sockets are always female.
Click to expand...


Zen Mod said:


hot/cold or heiss/kalt

same logic as with mains plugs/prongs whatever their name is ;

if XLR is on input side you'll use one with three holes - from sinmple reason that with grabbing it with hands you can't induce any hum or static

that's rule for any case , xlr being on chassis or on cable .

output one is just another one ....... you must remember just input ones as important :rofl:
Click to expand...

Thanks! (I had followed AndrewT's reasoning, so bought female sockets for output... happily they'll exchange...)

Cheers

Nigel
 
#2,666
This high powered pre and output stage only power amp is catching on it seems! Speaking of catching, we need a catchy name for this approach. "Helper Amp" doesn't do it ;(

The Burning Amps certainly could be used this way, so that will add to the trend. We have tube and SS high ouput preamps. Not to mention (which Papa did..) that many high end preamps put out plenty of juice..

The Benchmark DACs and DAC/pre put out a pretty hefty balanced signal if the jumpers are set for it, due to their background in pro gear.

Come to think of it, doesn't all balanced pro gear work with higher output line level stuff?

MArk
 
#2,672
mostly silicone boobz unfortunately 🙁 wait, is that how it's spelled? :rofl:

I did find some 307A at a flea market... And probably have 807 and some of those 6BG6GA people rave about around here.

Does Edcor count as nice OPT iron? If not, I don't have much.. I do like those Taiwan jobs though...

Power transformers I'll have to check. Some Icelandic sounding name I remember with funny cotton looking hook up wires... and maybe some other things... Definitely some donuts here and there.
 
#2,673
Three questions about parts...

Hi there,

I've started my pumpkin build, doing the shunty first, which is mostly done, and the larger part of the casework. (I'm actually using the shell from an old dvd recorder to save some money... this will have a new front, et cetera, but it's actually a pretty good steel box for the price... 😉 )

Yesterday when I went to the local shop to buy the parts for the two pumpkin boards I ran into several problems at once. I've spent some time searching the usual suppliers on the internet, and I'd be grateful for any opinions on the following:

1. I can't get J309 jfets from any of the usual sources here in Brazil, but I can get J310, at a pretty good price. (Good enough to buy a goodly number to match). I understand from the cookbook that this can be used instead...

2. I can't trace IRF9510 mosfets without importing, which I would like to avoid for cost and time reasons. The cookbook says I can substitute various other model numbers "with somewhat different character in upper register"... Can anyone be more specific about what differences to expect? (ZM??) I also note that IRF9630 is not listed... Likely to be OK, or not OK? (This is what I'm using in the shunty, so if not OK even for the shunty please let me know....)

3. What about Fairchild equivalents? Somewhere on this thread the FQP3P20 is mentioned, and Fairchild lists it a sub for the IRF9610. I also found FQP17P10 listed as a sub for various things like IRF9530S and IRF9533 and so forth, but no direct equivalent for IRF9510. I can probably get the Fairchild models through Farnell-Newark so I'd be interested to know what people think.

4. I'm also wondering about the N-channel mosfets - If I have understood the cookbook correctly then they don't need to be complementary to the P-channel ones in the circuit. (I mean, if Q5 and Q7 are, say IRF9510 or the Fairchild equivalents, then Q6,Q8 can be IRF520 or IRF610 et cetera, and don't have to necessarily be IRF510...)
Is this correct? And as a further question, can anyone give me Fairchild model numbers for the N-channel stuff?

5. (I thought I saw the answer to this somewhere in this thread, but search failed me this time.... ) I like having separate volume controls for left and right channels, and hence no balance control. In this case I need two two-gang pots, since it is balanced, right? Am I OK with 10K log pots? Any model recommendations from forum members who buy stuff in Brazil?

Thanks in advance for any help.
Cheers

Nigel
 
#2,674
Re: Three questions about parts...

njepitt said:
Hi there,

I've started my pumpkin build, doing the shunty first, which is mostly done, and the larger part of the casework. (I'm actually using the shell from an old dvd recorder to save some money... this will have a new front, et cetera, but it's actually a pretty good steel box for the price... 😉 )

Yesterday when I went to the local shop to buy the parts for the two pumpkin boards I ran into several problems at once. I've spent some time searching the usual suppliers on the internet, and I'd be grateful for any opinions on the following:

1. I can't get J309 jfets from any of the usual sources here in Brazil, but I can get J310, at a pretty good price. (Good enough to buy a goodly number to match). I understand from the cookbook that this can be used instead...

2. I can't trace IRF9510 mosfets without importing, which I would like to avoid for cost and time reasons. The cookbook says I can substitute various other model numbers "with somewhat different character in upper register"... Can anyone be more specific about what differences to expect? (ZM??) I also note that IRF9630 is not listed... Likely to be OK, or not OK? (This is what I'm using in the shunty, so if not OK even for the shunty please let me know....)

3. What about Fairchild equivalents? Somewhere on this thread the FQP3P20 is mentioned, and Fairchild lists it a sub for the IRF9610. I also found FQP17P10 listed as a sub for various things like IRF9530S and IRF9533 and so forth, but no direct equivalent for IRF9510. I can probably get the Fairchild models through Farnell-Newark so I'd be interested to know what people think.

4. I'm also wondering about the N-channel mosfets - If I have understood the cookbook correctly then they don't need to be complementary to the P-channel ones in the circuit. (I mean, if Q5 and Q7 are, say IRF9510 or the Fairchild equivalents, then Q6,Q8 can be IRF520 or IRF610 et cetera, and don't have to necessarily be IRF510...)
Is this correct? And as a further question, can anyone give me Fairchild model numbers for the N-channel stuff?

5. (I thought I saw the answer to this somewhere in this thread, but search failed me this time.... ) I like having separate volume controls for left and right channels, and hence no balance control. In this case I need two two-gang pots, since it is balanced, right? Am I OK with 10K log pots? Any model recommendations from forum members who buy stuff in Brazil?

Thanks in advance for any help.
Cheers

Nigel
Click to expand...


that were 3 .... or 5 questions ?

:rofl:

anyway -

1. 310's are perfectly fine

2. for Shunty - use any TO220 mosfets you can easily find - it's completely OK ; they're "just" in PSU regulation :clown:

3. in Pumpie - 9510s are active parts ; 510s are CCS-es (load for active ones ) ; CCS ones are much less critical regarding type ;
anyway - for upper ( active ) ones - try to find/use mosfets with not much greater gate capacitance , because that will result in somewhat lesser gain in high frequencies ....
for CCS ones capacitance is not much of issue
- I dunno exact Fairchild replacements for 9510 , from top of my head ....... I hope someone will jump in .....

4. (or was it 3a. question ? ) hehe

look at 3 ..... up

5. dunno exact brands/types for your neck of wood , but regarding value - 10K stereo logs (one per channel) are completely fine .


I hope I help'd ya ........

😀
 
#2,675
Thanks, ZM... OK, so I'm actually not sure how many question, 3 or 5, but they are all pretty much answered... 😎 Only thing outstanding would be the Fairchild models, but if you say gate capacitance is the key then I dare say I can dig that information out of the Fairchild site...

Many thanks again, and I'll post pictures as things develop.

Cheers

Nigel
 
#2,677
Tea-Bag said:
For IRFs
FQP5P10 P-channel
IRF510A N-channel are the one's I used. Both fairchild.
Click to expand...

I'll search Farnell-Newark for these. (It'll have to be "by hand" since the search function doesn't appear to be working properly on their site...) Any serious difference between IRF510A and plain vanilla IRF510?


Thanks

Nigel
 
#2,678
Another parts question, I'm afraid... The shunty is nearly finished, but I have failed to find the LM336Z-5 regulators, and need to use some kind of substitute. Here's some questions.

1. On the schematic the diode part is connected across C12. The datasheet for LM336Z-5 shows a TO-92 part, where the third pin is the adjustment. I presume this is not connected in the shunty, since the schematic shows a line leading off the diode not connected to anything. Is this correct?

2. The shop suggested using 78L05 voltage regulators in place of the LM336Z-5. This is also a TO-92 part, with Vin, Vout and Gnd, but this doesn't seem to be quite the same sort of thing. On the other hand, if I have understood the function of U1 correctly, the particular part doesn't seem to be critical, and any 5V regulator should work OK, right?

Does anyone have any suggestions?

Cheers

Nigel
 
#2,680
Zen Mod said:
LM336-5 is reference zener ;

IC certainly , but function is as zener ;

put 5V1 zener instead , but try to find real thing as soon you can
Click to expand...


Found it! Well, I was due a little luck with finding parts... I just got back from the local electronics shops, and I found the LM336Z-5 in a smaller place. They also had some IRFP9610 at R$2.50 each (about US$1.20) so I bought the eight they had in the hopes of getting two matched pairs for the pumpkin boards. So all set now except for the J310s, which I can get online from Farnell-Newark in SP, and I still need to find volume pots and a switch to select inputs (I guess a 4-gang rotary switch).

Out of interest (and although it's not important to me now it may help someone else reading this), what is the advantage of the LM336Z-5 over the 5V1 zener you suggest? I was also going to try to find LM4040, which seemed to me to be a reasonably close substitute, since we don't care about adjustment; would it have been OK?

Many thanks
Nigel
 
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