Hey everyone, I have had a crack for about a month now, and since it is my first amp I am continually amazed at how awesome music sounds. However I have begun to notice quite a bit noise when there is no music playing. Is this normal? I usually cant tell when music is playing, unless it gets really low and then I can hear the humming in the background. Would this be fixed with the speedball upgrade? I use Decibel for a music player, HRT MSII DAC, blue jean rca, beyerdynamic dt990 600ohm.
Background hum
- Thread starter fullmetal
- Start date
Leaving it on should never be a problem unless something has failed. Vibrating could mean that a tube is drawing too much current. Start by taking the voltage measurements and let us know if anything seems way off. As Grainger mentions it could be a solder joint that opened up, or it could be a tube going south.
Funny that I found this thread just now, I was thinking about the background hum in my amp as well. It is very low though still audible if there is no music at all and during silent passages with very few instruments. I don't think there is something wrong however, I just wanted to know if there is a hum present in these amplifiers or if they should be dead quiet? The latter seems a bit unnatural since I know how much my guitar amp hums.....
My crack with speedball and stock tubes is very very quiet into shorted inputs, no hum at all. With some of the 6AS7 there is a tiny bit of hum, it can be made worse by adding a 6SN7. But even at it's worst it is still hardly discernible and when you ply music I do not notice it except between tracks or very quiet passages.
I had a bad tube that had a raised noise floor on one channel.
Just listening to mine now I realised that if the source on my pre-amp was the iPod I'd get a slightly raised noise floor that isn't there with my dac. It could be a number of things until you've eliminated some steps - have you swapped the input cable around (l/r to r/l)? That at least narrows down the fault to the amp.
Dac > Speedball > 600Ω headphones is dead silent on mine.
Just listening to mine now I realised that if the source on my pre-amp was the iPod I'd get a slightly raised noise floor that isn't there with my dac. It could be a number of things until you've eliminated some steps - have you swapped the input cable around (l/r to r/l)? That at least narrows down the fault to the amp.
Dac > Speedball > 600Ω headphones is dead silent on mine.
Yes, to be sure of the noise floor you have to remember that it can be coming in ahead of the amp. So the best way to listen to the noise floor is with the inputs shorted with shorting jacks. That way you will only heard noise generated by the amp.
Fullmetal, have your tried different tubes? That would be one important test to make after you make the voltage checks. If a simple tube swap doesn't solve it - since your problem is dominant in one channel you should probably go over the solder joints concentrating on the connections on the side with the noisy channel. It makes the most sense to solve this problem explicitly rather than hoping that installing the upgrade will solve it.
Fullmetal, have your tried different tubes? That would be one important test to make after you make the voltage checks. If a simple tube swap doesn't solve it - since your problem is dominant in one channel you should probably go over the solder joints concentrating on the connections on the side with the noisy channel. It makes the most sense to solve this problem explicitly rather than hoping that installing the upgrade will solve it.
Would you believe it?
I just switched off my pre-amp power supply and power amp (both Naim) for the first time in months and bongo. One channel with a raised noise floor on my input tube... Grr, I only had that E80CC in for a few days as well, it was working perfectly. Both the Crack and Naim system are connected to the same mains but the crack was turned off at the time, could it be coincidence?
Luckily my faithful CV4003 is still working a-okay.
I just switched off my pre-amp power supply and power amp (both Naim) for the first time in months and bongo. One channel with a raised noise floor on my input tube... Grr, I only had that E80CC in for a few days as well, it was working perfectly. Both the Crack and Naim system are connected to the same mains but the crack was turned off at the time, could it be coincidence?
Luckily my faithful CV4003 is still working a-okay.
Maybe this can help... I finished my build the weekend before this past one. I built the Crack stock with the excpetion of using Mills resistors in place of the stock cement/wirewounds and used an Alps Blue Velvet volume pot. The amp is, for all intents and purposes, silent. I was and still am incredibly impressed with the lack of any preceptible background noise. I havent shorted the inputs to check whether the background is actually "black", but in terms of normal listening, there is nothing there. For all intents and purposes, it's silent (Speedball must be really impressive).
My point is that the amp, in stock form, is capable of a near silent background during normal listening (including quiet passages and pauses in the music). I use the word near as a qualifier only because an auidophiles description of silent may be different from mine, but you get the point I think. So follow the advice of the more knowledgable folks who have offered suggestions.
For the record, my main phones are Beyer 990's (250 ohm).
My point is that the amp, in stock form, is capable of a near silent background during normal listening (including quiet passages and pauses in the music). I use the word near as a qualifier only because an auidophiles description of silent may be different from mine, but you get the point I think. So follow the advice of the more knowledgable folks who have offered suggestions.
For the record, my main phones are Beyer 990's (250 ohm).
Grainger49
New member
I expect that the sensitivity and impedance of the phones used will affect the level of noise you hear. That is, in addition to the tubes as Doc mentioned already.
Apologies for the slight thread-jack.
When I turn on the crack with the E80CC in I get a inrush type hiss in the right channel, then it dies down completely before the same happens on the left a second or two later (but the hiss stays at a noticeable level). Is this indicative of something?
I've noticed that in general when I power on one channel usually comes up first and also when powering down, I guess this is normal? Could the E80CC have suffered in some manner because of this?
I quite liked the sound of it and am considering replacing it, is it a lost cause though or just a bad experience? My other tubes seem perfect fwiw.
When I turn on the crack with the E80CC in I get a inrush type hiss in the right channel, then it dies down completely before the same happens on the left a second or two later (but the hiss stays at a noticeable level). Is this indicative of something?
I've noticed that in general when I power on one channel usually comes up first and also when powering down, I guess this is normal? Could the E80CC have suffered in some manner because of this?
I quite liked the sound of it and am considering replacing it, is it a lost cause though or just a bad experience? My other tubes seem perfect fwiw.
I just finished my speedball upgrade yesterday and with the exception of soldering one of the 2907A transistors where one of the 2222A was suppose to go everything is working. I discovered my mistake shortly after doing it and set it right. However, my amp is no longer as "black" quiet as it was before. There is definitely a low background hum that seems to be unaffected by the volume control and a pronounced buzzing that comes in between 75-100% volume. I've had a good look and most of the ground contacts and the soldering seems solid. Any thoughts on where I should start to troubleshoot?
Thanks.
Mark
Thanks.
Mark
If the transistors got power before the mistake was discovered, I would start by replacing the 2N2907 and 2N2222 that were installed in the wrong places. They may have been damaged and that could be creating the noise. Other than that the other idea would be to go over all of the new solder joints that were created with the upgrade with a hot iron and reflow them.
Grainger49
New member
If you didn't power it up before swapping the transistors rewet all the solder joints for the Speedball upgrade connections to and from the circuit and to and from the circuit board first. If that doesn't help then try the boards themselves.
