getting a pop when i power down, help

[parkerfly]

i have a Cayin ta-30 (el-34) hooked up to a passive pre which i run with a Single driver set up. The amp runs 4 el-34's biased at 350 to give it 30 watts.. The amp is set up so that you can take out 2 power tubes and bias it to 700 and it becomes a SEP (4 watts). Everytime i do this (with a pre or without) i get a pop through the speakers after about 5 seconds when i power off. I turn all the volumes down and still get the pop. the pop dose not happen when all 4 tubes are running only when i take 2 out and bias at 700. I built the speakers , interconnects and speaker cables which all work well with my other gear. Am i doing something wrong? can it be fixed?


Any ideas would be helpful.( my technical knowledge is not great)

Thanks.

 

[Gordy]

If you post a circuit diagram the forum members might find it easier to offer advice...

 

[Palustris]

bias it to 700

700 what? A, Ma, V, mV, W?

 

[parkerfly]

Meter is set at 2000(mV) range, the link below explains how to do it. Could not find a schematic, sorry.

http://www.angelfire.com/biz/bizzyb/TA30ADJUSTMENTS.html

 

[richwalters]

Sounds like going through a bout of instability when volts falls in certain amp sections. Otherwise guessing.-> Need CCT diagram to make sense.

richy

 

[parkerfly]

its looking like i am not going to be able to provide enough information or insight to be helped. Thank you for looking, i'll regroup and get more info.