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Went to turn on the system yesterday and fired up a CD. Treble is fine but bass is highly attenuated. As if there were tone controls and the bass was all the way down.
The system is an Ah! Njoe Tjoeb CDP, AES-AE3 DJH pre, AES Six Pac amps and Apogee Caliper speakers.
I substituted tubes in the CDP, pre, and the 12BZ7 on the amps. Nothing.
I switched out to another CDP. Checked cables. Even switched in small bookshelf speakers.
I can't find the source of the problem. But since it's in both channels, I'm suspecting the pre-amp. But what in a pre-amp would cause this problem?
Thoughts or suggestions would be much appreciated. Where did all the bass go? I'm stumped!
___
Jeff TOJ
I like it. I like it a lot.
Follow Ups:
Or, if you have a monitor/tape out on your preamp, connect the ICs between the amp and the preamp to the monitor out.
What you are doing here is finding out if it's in the gain stage of the preamp. If so, you should get the bass back. Remember, it will play loud and you will have no volume control. If the bass is OK, then it is the preamp. If not, the problem is in the amp or speakers or both.
Let us know.
"You don't need to be a Weatherman to know which way the wind blows"
Thanks for this suggestion. I was going to be borrowing a pre-amp tomorrow...
The Ah! has an internal volume control, so hooking up directly to the amps was simple (don't know why I didn't think of doing this; it was my modus operandi at one time). The problem was still there.
Late last night I had the spouse listen in (she can tell when I'm distraught). She said it sounded like only the left channel. So this morning, after eliminating the pre-amp as the culprit, I switched amps.
And wow, bass again! All I can now deduce is that the speaker cable out to the bass panel was either corroded or barely connected. Re-connecting it solved the problem.
So thank you again. Eliminating the pre-amp from the equation set me down the correct path.
___
Jeff TOJ
I like it. I like it a lot.
Your speakers are bi-wired are they?
Bi-wired and I checked the wiring. Both tweeter and woofer panels are firing. Just way attenuated bass.
I'm starting to wonder also if some of the caps in the crossover might have blown. But it's in both channels at once. Two days ago life was wonderful.
___
Jeff TOJ
I like it. I like it a lot.
Coupling capacitors can pass high frequencies easily, lower frequencies are more difficult. Perhaps you have a coupling cap that is defective, effectively reducing its capacitance.
We'll have to agree to disagree about global warming until the next global cooling scare comes along
I'll check, but if I remember correctly, the AES pre-amp has no coupling capacitors.
___
Jeff TOJ
I like it. I like it a lot.
It can't be a coupling cap as both channels are affected. It sounds more like a power supply cap. If you have schematics and a VOM you could check the voltages throughout the preamp.
Edits: 03/18/12
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