resonance/micro phonic sound when tapping on the unit

[Paul Birkeland]

So you are saying that all 12AU7s and all 6080s are microphonic?

This is not a problem I have had with the 12SU7s in my FP 2.

Yes, all tubes will be microphonic to some extent. 

If your Foreplay 2 was a headphone amp, you might notice this.  (I can tap on 12AU7's in a Foreplay when it's driving a Crack and hear this quite clearly)

To the OP - you swapped 6080's between the Crack and your other amp, but likely you have a 12AU7 that is more microphonic than normal.  You can replace it with a different tube, or just recognize that this is normal with a certain percentage of tubes and keep using it. 

[Doc B.]

Everyone, chill.

If you are certain that it isn't a tube, then the next step is to turn the amp over in its base, carefully plug it in, turn it on and take a non conductive implement like a chopstick or plastic pen and tap the components near the area where you noticed the sound coming when you tapped the top. Listen over your headphones for the ringing, you may find a part that is loose and vibrating when you tap it, that is transmitted into your headphone cable or into a tube.

[xcoolhandx]

FWIW mine is dead silent. You buy this already assembled by someone else and you seem to think that this is a problem related to design rather than the obvious solution. Maybe you should be talking to the "bro" that sold it to you, rather than coming here and dissing an extremely successful design. Have a nice life

you are the one that's full of assumptions and then some ,I bought this from someone that had this already assembled and came here to find  solution to a problem I'm having since that's what this forum is for, so please go and do something that have a meaning in life instead of hanging around here and acting all bad,trust me I wouldn't have a problem putting  this together but my eyesight is not all that great anymore
Thank you for your helpful input Sir

[Doc B.]

Let's get back to the troubleshooting issue. Please try what I suggested below and let us know if it helps to narrow down the cause.

[vetmed]

I sincerely hope you are able to fix your problem,and am sorry that you are having problems with your eyesight. However you do catch more flies with honey than vinegar and dismissing very experienced people's advice out of hand is not a good way to start off around here


Peace, love, and happiness

[Mike B]

The guy that built that thing is suspect.

I see an LED propped way up from the board right next to one that is flush.  I see lots of unclipped leads.  I see a lack of solder.  I see a resistor connection that was clipped too short.  I see transistors that are too low.

Yup, I suspect the age old assembly problems.

I can tell you that mine does not ring even if I tap the tubes let alone the plate or the base.

Good luck!

[xcoolhandx]

Everyone, chill.

If you are certain that it isn't a tube, then the next step is to turn the amp over in its base, carefully plug it in, turn it on and take a non conductive implement like a chopstick or plastic pen and tap the components near the area where you noticed the sound coming when you tapped the top. Listen over your headphones for the ringing, you may find a part that is loose and vibrating when you tap it, that is transmitted into your headphone cable or into a tube.

I did what you suggested with no avail ,can't find the source , still pulling to the left (hear more in the left channel)
EDIT; if you want I can take close-up pics of all the soldering ,I also noticed that one of the square PCBs (I think it's called LED and that's what the MikeB was referring ) is tilted-there is little to much solder on  one of the heatsink posts ,don't know if it's this would be the problem

[xcoolhandx]

I was going through the manual today just looking for my culprit ,here is the first thing that didn't look right quote from manual  ;
"Attach the 1/4” stripped end to terminal
13U. Thread the 1” stripped end
through terminal B5, then through
terminal B2. Solder 13L, solder B5"

comparison manual and my crack


 

[Paul Birkeland]

I will again say that this is most likely a microphonic 12AU7, have you tried a substitute?

In my opinion, the amp looks well built. 

In my experience, I haven't had microphonics in tube equipment come from anything but the tubes themselves. 

[xcoolhandx]

I will again say that this is most likely a microphonic 12AU7, have you tried a substitute?

In my opinion, the amp looks well built. 

In my experience, I haven't had microphonics in tube equipment come from anything but the tubes themselves.

I understand what you saying and wouldn't bother posting here ,I'm well aware of all the ins and outs of the valve tube in general ,..let me repeat my self again ..there is imbalance-> I can here more in the left channel then I can here in the right one (no matter what tube I use-TS 7236,5998,GEC 6AS7G,Haltron 6AS7G A1834  and for driver -new JJ ECC82,NOS 1952  Lansdale 12AU7 Black Plate,GE 12AU7 and two other tubes)  that was the main reason for me to investigate what was causing it  ,the tapping was just a tale tale of the right channel being noisy-lack off proper balance between both channels and an example of something not being right  that's why I mention it ,left channel is dead silent
I'm waiting for some 20 gauge wire and will disassemble this thing myself ..half blind ,will give some more slack for some wires especially around 9 pin socket and trim
excess leads

[Paul Birkeland]

Is the channel imbalance present regardless of volume control position?

[xcoolhandx]

no it's not ( I did read the FAQ ) ,sorry I edited my last post

[Paul Birkeland]

OK, if you have an imbalance at low volumes, you can pad the input of the Crack, or decrease the amount of signal coming out of your source.

[xcoolhandx]

NO I don't have imbalance at low volume just like I mention it in my last post
as for imbalance it's not a big difference but you can tell

[xcoolhandx]

there is at list two or three threads in the last two pages mentioning bad right channel ..co-incidents ?