Bass goes out when unplugging MacBook charger - Speedball + Crack

[xashy]

Hey everyone! Recently installed the speedball on my crack and I'm have a few hairy and harrowing issues. Firstly, I did not use my crack very much before I installed the speedball, so I can't accurately comment on whether the problems existed before installing the speedball. That being said, I have the following problems:

1) When my macbook charger is plugged in, I have bass in my hd 650s, but i have multiple frequency hums (high pitched buzzing, and white noise static). Occurs in different sockets in different rooms of my house.

2) When my macbook charger is unplugged, I only have a low hum, but I have no bass. Occurs in different sockets in different rooms of my house.


3) when turning the volume pot, I have crackling in my right earphone and generally the left phone goes out very easily.

4) when I fiddle with the headphone jack, i get can restore the sound in my left earphone.

5) with the macbook charger in, I get an additional high pitched buzz (maybe 15k hz?) when sending signal from my audio interface to the crack. I'm using a focusrite saffire 6 as a DAC.

All the voltages are correct and I have gone back and resoldered 10 joints or so. The only resistances that differ from the crack numbers are that terminals 7 and 9 read infinite resistance and not 2.9k ohms. Also, when testing voltages, I had a large blue spark occur at terminal 20 or 21 (voltage is fine after) and a large white spark when testing the voltage at terminal 9. I can post pictures if needed. Any help would be wholly appreciated, as I'm stuck and sad thanks so much guys!

 

[Grainger49]

1) Any computer, mac, PC, cell phone, will inject digital noise into any tubed device if it is too close.  I suggest getting a 6' (2M) cord to connect your Macbook and try it at the full distance of the cord.  This should get rid of the "multiple frequency hums."  Still, there might be a problem with your settings, but a Mac guy will have to help you there.  Just try the suggestions here first.

2) Still might be the computer injecting noise into the Crack. If you have the Speedball and no bass with a different source than the Macbook then that can be addressed.  You should have good bass.  But you need to try a different source with the Macbook off and unplugged.  Try a cheap CD player.

3) 4) First try the Crack FAQ sticky.  There is good information there, no need to repeat it here.

5) Same as 1) Computers are great but also sources of all kinds of noise.

In working with this kind of noise distance is your friend.  Noise dissipates with the square of the distance.  Bottlehead has suggested a 2M (6') cable for use with the BH DAC.  Guess why?

Trust us, the Crack can be truly great, tight extended bass and dead silent.  There are a few thousand out there that are.  Yours can be also.  So have patience with the board.  Try everything suggested and report back.  You will be all smile soon enough.

 

[Paul Birkeland]

Do you have a source to try besides the computer? 

 

[xashy]

Thanks so much for the help guys! I don't have my cables on me right now, but I will try to get some soon. In addition, while checking voltages yesterday, it looks like a I blew the fuse and it also looks like a blown rectifier diode may be the problem. I'm going to replace these with 1n4007s if I can find them at Radioshack ( i think the big blue spark may have taken 1 or 2 of the diodes out). I'll report back after the rectifiers and fuse have been replaced. No smoke from the transformer after the fuse blow, so hopefully it is still working

 

[xashy]

Okay so update. I have replaced 1 UF4007 rectifier diode with a 1N4005 that I believe was blown (another thread said I could probably do this - this is all I could find at Radioshack). Also, I couldn't find a 1 amp slow blow fuse, but did find a .75 amp fast acting fuse, which I am now using.

Altogether, the amp comes on, and the large tube seems brighter than before, but all the LEDs come on and all the voltages are all fine except for the following: A1 - 70, A6 - 75, B1 - 75, B4 - 70. Not sure if these are correct with speedball or not. I did manage to get a cord which allows me to connect my iphone directly (with an audio interface). With this now, I have no bass, but I can hear in both channels when the volume pot is turned high.

With the iphone plugged in, the sound buzz/hum is relatively quiet when at 50% volume, but no bass. I've checked all the grounds according to the stickied post and they are fine.

I have also gone back and resoldered any joints that looked possibly cold. The only other thing I can thing to do is the resistor mod on the volume pot outlined in the FAQ. I tested the large and small transistors as well, and those seem to be fine (all very high ohms, if they can be read at all on their 3 pins). Other than the voltages stated above, I can find no voltages or resistances out of the ordinary, even after following the ground stickied post as well. Any help would be greatly appreciated. Thanks so much guys.

UPDATE:

I went back to take a gander at the 270k ohm resistor and terminal 13. I found that I'm getting a * reading instead of "a climb toward 270k", even on the highest ohm setting on my meter. In addition, when checking the two wires coming of the resistor themselves, I'm getting erratic resistance activity of the resistor. I'm getting a (-)600k reading from the resistor, which is going extremely slowly back to zero. When I switch the test leads, I get the * when doing this.

P.S. sorry for being a complete and utter noob.

UPDATE 2:

When reverting to using the RCA cables I was using originally, I have found that when there is no input connected to the rca, I get a slight hum at 50% pot, but when I connect the iphone, the hum increases slightly in amplitude. HOWEVER, when I put one hand on the chassis AND one on the iphone, the hum goes dead silent at 50% volume. When I play music on the iphone with my hand on the chassis and on the iphone, there is bass and the amp sounds as clean as possible using the $0.50 DAC inside an iphone. However, as soon as I remove my hand from the chassis or iphone, I lose bass and get a low hz hum. The hum increases in volume if I have my hand on the iphone, but no hand on the chassis. There is no hope at all currently for my laptop/DAC setup. Again there is no bass, even with hand touching the chassis when using the laptop/dac combo. There is still crackling when turning up the pot and channels tend to go in and out above or below ~50% pot. The same can be said for another lower hz hum as well. Fiddling with the headphone jack still takes channels in and out. Thanks for reading this far! Haha.

UPDATE 3:

I have restored bass to the headphones/DAC while the macbook charger is connected. I did this by reflowing some joints. All other problems persist. Terminal 13 now reads * instead of the erratic -600 ohms, even at highest voltmeter setting. In addition, "grounding" the macbook with the charger, but not sending power through the charger (by leaving the charger half in) allows me to retain the bass and eliminate the buzz and the static. All I am left with is low hum at 120hz (probably), a sine wavish hum at 200 hz (maybe) and another prominent hum at 400 hz or so.

UPDATE 4:

RCA center pins are now reading 50k ohms each instead of 90-100k. Not sure why. Too tired to try to figure it out at the moment. RCA ground lugs are correctly reading 0 ohms. In total, A1, A6, B1 and B4 are low. Terminals 7, 9 and 13 give * resistances when they shouldn't.

 

[Paul Birkeland]

Your voltages/resistances are not a problem.  What headphones are you using?

 

[xashy]

Hey guys. Thanks for following up.

Concerning the headphones, I am using HD650s.

About the input other than my DAC/laptop:

When reverting to using the RCA cables I was using originally, I have found that when there is no input connected to the rca, I get a slight hum at 50% pot, but when I connect my iphone, the hum increases slightly in amplitude. HOWEVER, when I put one hand on the chassis AND one on the iphone, the hum goes dead silent at 50% volume. When I play music on the iphone with my hand on the chassis and on the iphone, there is bass and the amp sounds as clean as possible using the $0.50 DAC inside an iphone. However, as soon as I remove my hand from the chassis or iphone, I lose bass and get a low hz hum. The hum increases in volume if I have my hand on the iphone, but no hand on the chassis. With the laptop/DAC combo, I now get bass while the charger is plugged in, but an additional high hz white noise when power is flowing to the laptop. When the laptop is only "grounded" with the charger and not actually sending power to the laptop, I don't have the hum and DO have bass.  There is still crackling when turning up the pot and channels tend to go in and out above or below ~50% pot. The same can be said for another lower hz hum as well. Fiddling with the headphone jack still takes channels in and out.

Also, the interference associated with the laptop/DAC is length independent. Still get the same exact hum even 5 feet away or so. When pressing the play button on my laptop, I get an additional high Hz hum in maybe the 1500 hz range, even when the volume on the laptop output is 0. All of these hums increase with volume pot increase.

 

[Strikkflypilot]

All screws tightened properly?

 

[Paul Birkeland]

You either have a loose screw in the amplifier, or you have a ground connection that is poorly soldered. 

-PB

 

[xashy]

Hello again everyone.

I really appreciate the help thus far. I have gone back and tightened up the screws. It turns out the screw at terminal 8 was a bit loose. However, tightening this had no effect on the sound. I went through and rechecked each ground point according to Doc B's guide - all are fine, once again.

The crack itself is dead quiet at 50% pot when there are no RCA cables in the inputs... I'm stilling have the same odd effects with the "grounding" of my iphone and macbook, respectively. This leads me to believe it's still some problem inside the crack/speedball, if two different sources have grounding issues (where the bass goes out, if the source isn't grounded by my hands). Also, I randomly checked the screws on the middle of the heat sink plates on the speedball main PCB - one read *, while the other screw read 0 ohms. Does this make sense? I can't see why they would have different readings. I also rechecked the resistances across the each of the 3 prongs (3 combos) for each of the transistors that are connected to the heat sinks - all read *, as expected.

Also, should I still do an RCA shorting plug test? If so, I was thinking about buying these if they ship to the US:
http://www.takefiveaudio.com/mall/shopexd.asp?id=1416

Thanks so much for the help guys. Soon, I'll either have to give up, or pay up for someone to try to fix it.

 

[Paul Birkeland]

The heatsink screw heads will most likely read 0 Ohms, but it's OK if they don't.

I'd still imagine there's a flaky solder joint or two inside the amplifier causing this issue.

-PB