Re: PS
Pumpie:
just use it in 5x gain mode ;
that means 10K in line with gates and 47K in feedback path ;
in case that you feel too small gain , just increase 47K
in any case - that drek is /will be yours , so you can do whatever you want ............. except neg gain ........... ( without meaning on phase )
zettelsm said:Yes, I did download and read the Cookbook, (and I thought it was a great thing for you to do). I believe I understand the "how to" part of lowering the gain/voltage swing of Pumpy. But maybe I missed something. I've had the flu for the last couple of days and haven't been in my right mind.
What I am not sure about is "how much" to lower the gain. Or perhaps I don't need to lower it at all. I don't mind using the lower part of the pot or stepped attenuator, so long as I have enough control over small adjustments without always hunting and being too loud or too soft.
I tried a a well-thought-of Chinese 2A3 integrated amp a while ago with my DIY Edgarhorns, and besides being unacceptably noisy, it was too loud at the third click of the stepped attenuator.
So maybe all I need to do is figure out the right range of potentiometer. I remember reading that a lower value is theoretically better for performance
Am I barking up the wrong tree?
Feel free to heap ridicule on my head!
Steve Z
Libby, MT USA
zettelsm said:
Pumpie:
just use it in 5x gain mode ;
that means 10K in line with gates and 47K in feedback path ;
in case that you feel too small gain , just increase 47K
in any case - that drek is /will be yours , so you can do whatever you want ............. except neg gain ........... ( without meaning on phase )
Re: Re: PS
R5/R1 and R6/R3 to 4.7/1 and since R5 & R6 are decreased by 1/2, C1 & C2 are increased by 2X. . . (I did really read the Cookbook -- 101 Ways to Cook Serbian Pumpkin)
After posting my question about potentiometer range, it occurred to me that I could try a couple of cheap stereo log pots in ranges 10K, 25K, 100K and see what I like best before spending $$ for a four-channel. I even have a couple of old ALPS square stereo pots around here somewhere -- and they are Blue!
Thank you,
Steve Z
Zen Mod said:
Pumpie:
just use it in 5x gain mode ;
that means 10K in line with gates and 47K in feedback path ;
in case that you feel too small gain , just increase 47K
in any case - that drek is /will be yours , so you can do whatever you want ............. except neg gain ........... ( without meaning on phase )
R5/R1 and R6/R3 to 4.7/1 and since R5 & R6 are decreased by 1/2, C1 & C2 are increased by 2X. . . (I did really read the Cookbook -- 101 Ways to Cook Serbian Pumpkin)
After posting my question about potentiometer range, it occurred to me that I could try a couple of cheap stereo log pots in ranges 10K, 25K, 100K and see what I like best before spending $$ for a four-channel. I even have a couple of old ALPS square stereo pots around here somewhere -- and they are Blue!
Thank you,
Steve Z
Re: Re: Re: PS
sorry if I missundestood your question.........
anyway - value of pot will not have effect on gain , at least if you are in range of 10 - 100 K ; in any case - stay in lower range of pot value , if you can .......... it's just more convenient blahblah
zettelsm said:
R5/R1 and R6/R3 to 4.7/1 and since R5 & R6 are decreased by 1/2, C1 & C2 are increased by 2X. . . (I did really read the Cookbook -- 101 Ways to Cook Serbian Pumpkin)
After posting my question about potentiometer range, it occurred to me that I could try a couple of cheap stereo log pots in ranges 10K, 25K, 100K and see what I like best before spending $$ for a four-channel. I even have a couple of old ALPS square stereo pots around here somewhere -- and they are Blue!
Thank you,
Steve Z
sorry if I missundestood your question.........
anyway - value of pot will not have effect on gain , at least if you are in range of 10 - 100 K ; in any case - stay in lower range of pot value , if you can .......... it's just more convenient blahblah
I wasn't clear what I was asking, Choky.
I was wondering -- with my very sensitive speakers -- if:
1. I should decrease gain, or,
2. If there is a value of potentiometer that will avoid having all the working range at the bottom, and that will prevent that working range of adjustment -- from too soft to too loud -- being too small.
Or maybe even,
3. Both.
But, after thinking about it last night between bouts of hugging the bucket with the flu, I decided what I should do is leave gain alone at first, and play with some different value pots instead to see if I can get what I want. No sense crippling the F4 by choosing Pumpy gain so low that F4 cannot achieve full output.
Even though I probably listen with milliwatts going to the horns, it would be nice to have the whole 25 wpc available for headroom for transients. Or to listen to my system when I am visiting my neighbor down the road
You're absolutely right -- it's my Pumpy and I can do anything I want!
Thanks for your time and trouble.
Steve Z
I was wondering -- with my very sensitive speakers -- if:
1. I should decrease gain, or,
2. If there is a value of potentiometer that will avoid having all the working range at the bottom, and that will prevent that working range of adjustment -- from too soft to too loud -- being too small.
Or maybe even,
3. Both.
But, after thinking about it last night between bouts of hugging the bucket with the flu, I decided what I should do is leave gain alone at first, and play with some different value pots instead to see if I can get what I want. No sense crippling the F4 by choosing Pumpy gain so low that F4 cannot achieve full output.
Even though I probably listen with milliwatts going to the horns, it would be nice to have the whole 25 wpc available for headroom for transients. Or to listen to my system when I am visiting my neighbor down the road
You're absolutely right -- it's my Pumpy and I can do anything I want!
Thanks for your time and trouble.
Steve Z
zettelsm said:I wasn't clear what I was asking, Choky.
I was wondering -- with my very sensitive speakers -- if:
1. I should decrease gain, or,
2. If there is a value of potentiometer that will avoid having all the working range at the bottom, and that will prevent that working range of adjustment -- from too soft to too loud -- being too small.
Or maybe even,
3. Both.
But, after thinking about it last night between bouts of hugging the bucket with the flu, I decided what I should do is leave gain alone at first, and play with some different value pots instead to see if I can get what I want. No sense crippling the F4 by choosing Pumpy gain so low that F4 cannot achieve full output.
Even though I probably listen with milliwatts going to the horns, it would be nice to have the whole 25 wpc available for headroom for transients. Or to listen to my system when I am visiting my neighbor down the road
You're absolutely right -- it's my Pumpy and I can do anything I want!
Thanks for your time and trouble.
Steve Z
I repeat - you;'ll have no influence on gain and noise , changing pot value ;
you must set gain for your needs ....... dynamic reserve is entirely different issue than gain of Pumpie........ that's dynamic reserve of F4 and Pumpie .........
imagine that you're riding whoompin' 1500mW in your spks , with Pumpie/F4 gain set to 68K/10K .........
in a moment - nasty ZM-like trumpet man just throw all his frustration ( his missus wasn't in mood - last month) , and you have in a moment whoompin' 4K mW in your spk ........
point is that Pumpie/F4 combo isn't surprised with 4K mW demand - neither Pumpie is clipping in input , or output , neither F4 is clipping .......
comprende?
Zen Mod said:
I repeat - you;'ll have no influence on gain and noise , changing pot value ;
you must set gain for your needs ....... dynamic reserve is entirely different issue than gain of Pumpie........ that's dynamic reserve of F4 and Pumpie .........
imagine that you're riding whoompin' 1500mW in your spks , with Pumpie/F4 gain set to 68K/10K .........
in a moment - nasty ZM-like trumpet man just throw all his frustration ( his missus wasn't in mood - last month) , and you have in a moment whoompin' 4K mW in your spk ........
point is that Pumpie/F4 combo isn't surprised with 4K mW demand - neither Pumpie is clipping in input , or output , neither F4 is clipping .......
comprende?
Understood about gain and noise -- R5/R1 and R6/R3 only sets gain. Really!
Guess I am having a major conceptual error -- aka as "brain-fart"-- over how dynamic reserve is totally different issue from Pumpy gain. If Pumpy -- or any preamp -- does not have gain of about 14-15 then it won't drive F4 to full 25 wpc. At least, this is what I thought I understood from Mr. Pass and others on F4 thread. . .
Nice horn example -- is this where expression "horn-y" came from?
Not worried about clipping Pumpy or F4, but thought it desirable to achieve full voltage swing, even if it might not be used with this particular set of speakers.
Sorry -- I'm not usually so dense. Once upon a time I was actually trained in electrical and electronics theory. Too many years sitting in a Control Room watching pretty lights and pushing buttons. . .
Like I said, I can alway change R5/R1 and R6/R3 if the original setting doesn't work for me. Nice thing about DIY.
Steve Z
zettelsm said:
Understood about gain and noise -- R5/R1 and R6/R3 only sets gain. Really!
Guess I am having a major conceptual error -- aka as "brain-fart"-- over how dynamic reserve is totally different issue from Pumpy gain. If Pumpy -- or any preamp -- does not have gain of about 14-15 then it won't drive F4 to full 25 wpc. At least, this is what I thought I understood from Mr. Pass and others on F4 thread. . .
Nice horn example -- is this where expression "horn-y" came from?
Not worried about clipping Pumpy or F4, but thought it desirable to achieve full voltage swing, even if it might not be used with this particular set of speakers.
Sorry -- I'm not usually so dense. Once upon a time I was actually trained in electrical and electronics theory. Too many years sitting in a Control Room watching pretty lights and pushing buttons. . .
Like I said, I can alway change R5/R1 and R6/R3 if the original setting doesn't work for me. Nice thing about DIY.
Steve Z
What's the max output of the average DAC? 2V?
Say if I use a gain of 10 - this will give me +20V / -20V at pumpy output (assuming pot fully open). Single ended output will be +20V
Feeding this into F4 - will cause it to clip - because it's headroom is 18V (single ended)?
Hmmm - I guess whether it will clip or not eventually depends on the DAC (source) input.
Sorry - still learning!
thanks
her shann
hershann said:
(Sound of hand slapping forehead)
Yes, of course! Thank you Her Shann. I had completely overlooked the contribution of the source to driving the F4
Sometimes I think I have an infinite capacity to overlook the obvious. . .
Thanks for clearing up that particular error for me.
Steve Z
Hey all,
I'm trying to build me own pumpkin and got some q's. Unfortunately junkbox style, so sk170' s and different psu. Psu voltages all check out and I've set currents according to cookbook. All component values according to schematic.
However voltage at output (before coupling cap) stays at a little less then positive rail. Cookbook says it should be at 0V, right? it seems i can't adjust it and have a little voltage to ground at input as well, no relative offset.
Now what to do and where to look? I already looked for schematic with currents and voltages in other thread but don't get the clue.
regards,
Joris
ps sorry to be OT but cooking sausages....
damn now they'r burnt... should cook one thing at a time, either sausages or fets.
I'm trying to build me own pumpkin and got some q's. Unfortunately junkbox style, so sk170' s and different psu. Psu voltages all check out and I've set currents according to cookbook. All component values according to schematic.
However voltage at output (before coupling cap) stays at a little less then positive rail. Cookbook says it should be at 0V, right? it seems i can't adjust it and have a little voltage to ground at input as well, no relative offset.
Now what to do and where to look? I already looked for schematic with currents and voltages in other thread but don't get the clue.
regards,
Joris
ps sorry to be OT but cooking sausages....
damn now they'r burnt... should cook one thing at a time, either sausages or fets.
Still talking about gain & feedback -
I guess the value of R6/R3 determines the amount of negative feedback to determine the gain.
Other than voltage swing / gain - if there any other effect of changing the feedback/gain on the audio signal? Bandwidth wise or distortion wise.
I've read previously that more negative feedback (lower gain) will reduce distortion but will also limit the bandwidth. I assume that with the value of gain chosen for pumpie 4.7-15, there shouldn't be an issue with bandwidth?
her shann
I guess the value of R6/R3 determines the amount of negative feedback to determine the gain.
Other than voltage swing / gain - if there any other effect of changing the feedback/gain on the audio signal? Bandwidth wise or distortion wise.
I've read previously that more negative feedback (lower gain) will reduce distortion but will also limit the bandwidth. I assume that with the value of gain chosen for pumpie 4.7-15, there shouldn't be an issue with bandwidth?
her shann
Manu said:
Take a close look at ZM's picture. The -IN is simply shorted to ground at the header, (connecting the particular input) through a small piece of tinned CU wire, so when the relay of that particular input is selected, it will automatically short -IN to GND. Pretty bright idea, or what...
Zen Mod said:
The twisted X-driver, as they call it, actually does perform wonders. I like it a lot, indeed. If its for sentimental reasons I dont know, but I find the Pumpkin more musical and a tad less "clinical" to listen to. Noisewise the Twisted X driver is the winner. I never experienced anything like it. With the volume at full throttle (no signal ofcourse) there isn't even the least bit of hiss
The Pumpkin is absolutelly good in that respect also, but there is a slight trace of hiss at full output. Not that it matters for all practical purposes at all. That slight hiss, can never be heard with a signal on Having been listening to the Pumpkin for a while now, I must confess that it is my preamp of choice! It simply does have it all: Sweet silky topend details, very nice and warm midrange (voices) and a very firm bottomend! Now thats all pretty much heard before, but the Pumpkin has the very important "Foot-tapping"-effect like a X-BosoZ
I never thought that I would find that combination in one preamp! But here it is. I find it hard to keep my feet still, when using the Pumpkin Thanks a lot, Choky
hershann said:
yup , but not exactly ;
ratio of both sides R5/R1 AND R6/R3 is determining gain
hershann said:
nope
hershann said:
it will reduce distortion, but broaden bandwidth ; contrary to what you read
hershann said:
it will be bandwidth changes , but your ears certainly will not hear difference ......
steenoe said:
.........
The twisted X-driver, as they call it, actually does perform wonders. I like it a lot, indeed. If its for sentimental reasons I dont know, but I find the Pumpkin more musical and a tad less "clinical" to listen to. Noisewise the Twisted X driver is the winner. I never experienced anything like it. With the volume at full throttle (no signal ofcourse) there isn't even the least bit of hiss
Having been listening to the Pumpkin for a while now, I must confess that it is my preamp of choice! It simply does have it all: Sweet silky topend details, very nice and warm midrange (voices) and a very firm bottomend! Now thats all pretty much heard before, but the Pumpkin has the very important "Foot-tapping"-effect like a X-BosoZ
Thanks a lot, Choky
there is no need to thank me ........ and to make me blush ( even if that is pretty impossible
) ;I was interested in exact difference (sound etc. ) between these two sides of same coin...... hehe - even if mine is pretty gray comparing it to certain complexity of chips ......
...... thinking about difference in efforts to make one or another and final results ....in any case - if these chippy dreks are made by Papa's pattie pattie , they can't be bad ..... so easily
btw - I can't find exact schmtc of twisted X without too much trouble ..... (seems that today search func and me aren't in good relation
) have you linkie to exact post ............
hehe - I can bother ya - seems that your shoulder is certainly better - more than one post in a week
EDIT
I found it .......... 4 eyed ZM ......
http://www.diyaudio.com/forums/showthread.php?postid=921115#post921115
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