Hi Mif!
great suggestion, I substituted the two resistors with two 47ohm (2w) ones and now I can read 12.3V after the zeners! and it seems also a lot less hot!! ok after some 10 minutes it still gets somehow hot (resistor + last cap) maybe I still have some 75ma that I should dissipate at the res.. should I increse the res even some more?
thanks!
tent:wq
PS: digi01 -> the preamp sounds charming.. now working at the volume pot (actually some resistor based attenuator and fighting with the gain of my tamp which is too hig.. 33..
) and also the cabling I currently have is to undergoing some rework since I get some buzz in the background.. probably going too near to the toroid..
to cancerkazoo,
i think there are two reason caused the hiss.one is components itself,the other is the source.
look at your attached photo,i think you have not set up a volume pot for the preamp.the preamp gain setting is 10,it means 0.1V noise floor will get 1V noise output.you can disconnect the laptop watch if the hiss is gone.
i am always believe the laptop is not a good source for hi-fi.i think you'd better use a external sound card.and you'd better add dummy load(47ohm to 300ohm)for the card without line output.
Zang
i think there are two reason caused the hiss.one is components itself,the other is the source.
look at your attached photo,i think you have not set up a volume pot for the preamp.the preamp gain setting is 10,it means 0.1V noise floor will get 1V noise output.you can disconnect the laptop watch if the hiss is gone.
i am always believe the laptop is not a good source for hi-fi.i think you'd better use a external sound card.and you'd better add dummy load(47ohm to 300ohm)for the card without line output.
Zang
Hi,
what is either side of the pre-amp?The signal level and the power amplifier and the speakers as well as the pre-amp each affect the final SPL at the ears.
One must consider the system as a whole.
That would make sense, I was under the impression that this was a unity gain preamp. ( I thought I read that somewhere)
Is there a way to make this unity, or less? as my TV output is higher than what I want for my amp.
EDIT: I did find that my mains wiring is wrong in my living room (ground loop) because of the preamp, so I run it on an extention cord from the kitchen until I can correct it. But, now when I unplug the input (from laptop) I get noise, any idea what could be causing it now? The kitchen plug has 0v from neutral to ground and 120v from hot to ground, so it is wired correctly.
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Hi Andrew,
I didn't understand this so well.. what do you mean? I'm going to use different surces to be attached to the preamp (cd player, sat receiver, evne an ipod, etc..), then after this preamp stage with gain 10 it will enter my LM3886 stereo gainclone which currently has gain 33.. (860ohm res to ground and 22kohm as feedback) and finally all goes to my ciare speakers, 8ohm, fullrange, 96 efficency.
tent:wq
PS: cancerkazoo is now your buzz away? no hum any more (I mean by powering from the kitchen)?
Hi,
your chipamp can output a maximum ~22Vac to your speakers giving ~108dB SPL at maximum signal.
The maximum input signal to reach transient peak is 22/33 =660mVac.
Using a 10times gain pre-amp. the maximum signal required to give maximum output ~66mV.
Most, if not all modern, sources give way over this output voltage, some could be as high as 2500mVac.
Using excessive gain that has to be attenuated to a useable value has consequences that impacts on the overall performance of the system without any compensating gains in performance.
You probably don't need any pre-amp gain and I suspect all your sources need only an attenuator to drive your system into clipping.
You will need further attenuation just to make the system enjoyable for the majority of your normal listening time.
your chipamp can output a maximum ~22Vac to your speakers giving ~108dB SPL at maximum signal.
The maximum input signal to reach transient peak is 22/33 =660mVac.
Using a 10times gain pre-amp. the maximum signal required to give maximum output ~66mV.
Most, if not all modern, sources give way over this output voltage, some could be as high as 2500mVac.
Using excessive gain that has to be attenuated to a useable value has consequences that impacts on the overall performance of the system without any compensating gains in performance.
You probably don't need any pre-amp gain and I suspect all your sources need only an attenuator to drive your system into clipping.
You will need further attenuation just to make the system enjoyable for the majority of your normal listening time.
Well I perfectly agree, I definitely will need to attenuate my surces: if I'd connect my CD source directly to my LM3886-based power amp I'd sureli fire off my windows!!
So I was wanting to build a pre-amp to a) select sources via switch pot, b) attenuate volume via attenuation pot and c) I tought that using this also LM based pre-amp would improove sound.
At the end you probably would like to suggest me to use some less gain pre-amp? or maybe to rething the current gain of my power amp maybe? or just bypass pre-amp?
Thanks in advance,
tent:wq
It is very very low now, but I can still hear it with my ear up to the horn. (klipsch). It also increases when the interconnect is removed from the source.
But I have a feeling it will be a little better when in an enclosure and a chassis ground (and resistor?) is used.
I need to track down the mains power issue (6v between neutral-ground and 30v between hot-ground)and there is no ground behind the wall plate there.
i think you need not change the gain.you can adjust the levels with attenuator.the preamp with gain 10 is a average value.
for low gain setting,you have to apply deep feedback to the opamp that is no good.
the UCP preamp was designed for work under tough applications.it is not only for driving chip based power amp but also for driving solid & tube based power amp.some power amp have an low or nonlinear input impedance so that usual sources can not drive the input perfect.the preamp allows use of such devices without worry about impedance issue.
can you test below configuration?
(1)CD player ->attenuator->LM3886 poweramp
(2)CD player ->attenuator->UCP preamp->LM3886 poweramp
(3)CD player ->UCP preamp->attenuator->LM3886 poweramp
the outputs on a source are often lower sound quality than fixed outputs.some sources have nonlinear output impedances which are not perfect for driving a power amp directly.
Zang
yes,the preamp with gain 10.
you can modify the gian via adjust R5,R7,R6,R8.the preamp is a two stage device,voltage gain + buffer stage.for make this unity gain,set R7,R8 as 0ohm is a simple way.
Well,
I just ordered the board, the parts to stuff the board from mouser, and the stuff to stuff a PSU board I had left over from a gainclone project - basically the Carlos Filipe circuit.
The board was $20
Components to stuff UPC and PSU(including 2 OP2227P) $35
still need a xformer, and misc jacks, plugs, fuse holders etc along with enclosure, pot, and anything else I neglected to mention. probably another $100 or so.
All in all I am looking forward to this project for about $155...maybe less if I can repurpose an enclosure I have kicking around.
I just ordered the board, the parts to stuff the board from mouser, and the stuff to stuff a PSU board I had left over from a gainclone project - basically the Carlos Filipe circuit.
The board was $20
Components to stuff UPC and PSU(including 2 OP2227P) $35
still need a xformer, and misc jacks, plugs, fuse holders etc along with enclosure, pot, and anything else I neglected to mention. probably another $100 or so.
All in all I am looking forward to this project for about $155...maybe less if I can repurpose an enclosure I have kicking around.
Hi all,
I finally got some time to continue this project.. now populating my 6 channel pre amp with three of those pre-amps using LMs...
The attenuator is in good shape now..
Currently I'm struggling not having Hum and noise.. unluckily I do not know if I'm doing some earth ground wiring wrong or my implementation with PSU and toroids is wrong......
Anyway what I wanted to ask was: I was thinking also about putting a headphone jack in the box...))) Do you have a suggestion on how I could implement a headphone in this implementation? Something not too complicated..
Thanks,
tent:wq
I finally got some time to continue this project.. now populating my 6 channel pre amp with three of those pre-amps using LMs...
The attenuator is in good shape now..
Currently I'm struggling not having Hum and noise.. unluckily I do not know if I'm doing some earth ground wiring wrong or my implementation with PSU and toroids is wrong......
Anyway what I wanted to ask was: I was thinking also about putting a headphone jack in the box...
))) Do you have a suggestion on how I could implement a headphone in this implementation? Something not too complicated..Thanks,
tent:wq
Banned
Joined 2002
An externally hosted image should be here but it was not working when we last tested it.
VERSUS
The PSU board I have leftover from my chipamp.com project is the one I want to use for the UCP. I notice that there is a difference in the Carlos Fillipe circuit with the chipamp.com version having a +PGND and a -PGND.
How would I properly hook up the UCP to this PSU board?
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