Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: Bullpride on June 13, 2020, 06:11:13 AM

Title: Another weird one - Echo Sound when headphones all the way in
Post by: Bullpride on June 13, 2020, 06:11:13 AM

Was hearing some noise so I decided to do the Diode Mod on the Negative Lead.

Figured I would replace the POT (Put in a PEC) while I was at it.

Already have the small speedball board board install.

All voltages check out.
Decided to check the resistances.  Getting 2.5 on 6 and 10 when it should be zero.

Where is my problem?

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: Bullpride on June 13, 2020, 07:50:16 AM

If I unplug one either of the RCAs, it clears up. It seems like I have a bridge somewhere, but I don’t see it. Pics:

https://imgur.com/a/anol09t

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: Bullpride on June 13, 2020, 07:57:23 AM

Moved it upstairs and plugged it into my DAC instead of my ipad.  And Atticus instead of my AKG K545s.  Would the low impedance headphones cause the weird echo/crossover sound I was hearing?   

Everything sounds great now.  No noise, no echo, no buzz.
Should I be concerned about the resistance measurements on 6 and 10, or is that caused by adding the speedball small board?

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: pechelman on June 13, 2020, 08:04:18 AM

Not an expert, but shouldn't 6 and 10 be 2.4kohms in a resistance check? If you were checking dc voltage they should be zero according to the manual I have.

Unsure from the picture angles, but is there center lug on the pot touching the chassis? Also I can't tell but is the led on a3 touching anything on a4?

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: Bullpride on June 13, 2020, 08:32:13 AM

6. 0R
7. 2.9KR
8. 0R
9. 2.9KR
1 0. 0R

According to the manual.

I will check A3 and A4.  Pretty sure nothign is touching under the POT, but I will double. I do know I bent the center and left up a bit last time I was under it. May have been after this round of pics.

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: Paul Birkeland on June 13, 2020, 02:54:23 PM

Quote from: Bullpride on June 13, 2020, 06:11:13 AM

Decided to check the resistances.  Getting 2.5 on 6 and 10 when it should be zero.

Where is my problem?

Do you have an adapter or a cable plugged into the 1/4" jack?  That will change those readings.

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: Bullpride on June 13, 2020, 04:26:29 PM

Yes,  I have an angled 1/4 to 3.5. That would explain it.

Title: Re: Another weird one - Echo Sound when headphones all the way in
Post by: Paul Birkeland on June 14, 2020, 05:24:09 AM

Anyway, an echo can be just the tubes themselves picking up the vibration from the plug being inserted all the way.  This isn't particularly unusual or problematic.  The 6C45PI tubes in the Mainline are particularly prone to this.