• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Bose 901 Series II: pop when powered on

n0exit

n0exit

New Member
I just picked up a pair of Bose 901 Series II with equalizer, and when I hook them up to my NAD 3140, I get a loud pop when I turn everything on. I recapped the NAD a couple years ago, and it doesn't pop with my KLH Model 3s. Is it safe to say that the Bose equalizer is the culprit? The equalizer looks pristine on this inside. Or is it something else?

TW6CKAt.jpg
 
Register to hide this ad
Does it pop when the EQ is completely out of the circuit? Is it in the tape monitor loop, or pre-out/main in? If you turn the EQ on by itself first, and then turn on the NAD, do you get the pop?
 
As mentioned by jberger, try taking the EQ out and hooking them up without it. It' most likely the EQ. These work best in tape loops and not after the preamp also.
 
You can also plug the 901 EQ into an AC line and leave it running. That's assuming that the NAD has a speaker relay for protection.

Cheers,

David
 
jberger said:
Does it pop when the EQ is completely out of the circuit? Is it in the tape monitor loop, or pre-out/main in? If you turn the EQ on by itself first, and then turn on the NAD, do you get the pop?
Click to expand...

I haven't tried that yet taking the EQ out of the circuit yet. I just got the NAD going after replacing the power switch and anti-spark capacitor. Then it was only playing out of one channel, and I almost opened it back up before I realized that the bridging button on the back was in bridging mode. I had it in the pre-out/main in circuit.

dshoaf said:
You can also plug the 901 EQ into an AC line and leave it running. That's assuming that the NAD has a speaker relay for protection.
Click to expand...

I'm hesitant to leave it on all the time because the Series II EQ doesn't have a power switch, but I'll try turning it on first. The 3140 doesn't have a speaker relay, but there's a guy on here who has designed one for the 3020 that will probably work.
 
swechsler said:
What does the manual say (assuming someone out there has one)? Back when this was made, switched outlets on receivers/preamps/amps were pretty much universal.
Click to expand...

The manual says to connect the AC of the equalizer to the switched outlet. I'll try it with a wall outlet.

I need to fix the terminals on the speakers though. Two of them are loose, and on one, someone grabbed the end with pliers while trying to tighten the nut, causing the knurled thumb nut to bind on the post.
 
n0exit said:
The manual says to connect the AC of the equalizer to the switched outlet. I'll try it with a wall outlet.
Click to expand...
If that's the case, I wouldn't leave it plugged in all the time. Vintage electronics aren't as robust as modern ones, and I suspect that keeping it running 24/7 will hasten its demise.
 
n0exit said:
The manual says to connect the AC of the equalizer to the switched outlet. I'll try it with a wall outlet.
Click to expand...

I've owned a pair of 901 Series II since new in 1974. The equalizer has always been plugged into a switched outlet on my Pioneer SX-1010. I did have to have the EQ worked over recently, was dropping a channel every so often. I've not experienced the popping sound you mention.

On another note about the sound of the series II 901s... I have had these speakers setup in various different rooms over the years. Most rooms were either not big enough or the room wasn't conducive for reflecting sound as the 901s need. Placement and room size seem to be critical in finding that sweet setup. I can honestly say I now have what seems to be the perfect placement and room that really lets them shine. They are hanging down reflecting off the glass of a 25' solar room that is open to our living room and kitchen. There is NO lack of Bass for the first time! A good friend of mine stopped by recently to hear them for the first time. He is Magnepan owner, actually his theatre has a Magnepan system too. He was thoroughly impressed, especially considering the age of the technology. He wished he lived closer to bring his Magnepan system over and set it up in my house!
 
You must log in or register to reply here.
Back
Top Bottom