MBL Amplifiers clipping

martyt -- Mon, 01/19/2009 - 12:53

I have a pair of MBL 8011 mono amplifiers that clip on deep bass notes on analog source only. I find 2 records in my collection that I have had for many years and have played on many systems with no problem, they are Telarc's "The Firebird" and "pictures at an Exhibition" I have now acquired this pair of MBL amplifiers that sound excellent except for the 2 records. My previous amplifiers were the Cary 805 Anniversary Edition that never had clipping problems, the only other change to my system is the Rhea that has about 300 hours on it. I am using two cartridges and 2 arms. One is set at 44 db and the other is set at 68 db using a Aesthetix Rhea phono preamp. If I reduce the gain the problem goes away but the sound also is affected. I have the same 2 recordings on CD and do not have the problem even at a higher volume.
Any ideas are welcome.

brian -- Mon, 01/19/2009 - 13:43

martyt, what are your speakers?

Brian Walsh
Essential Audio ~ Chicago area ~ 773-809-HIFI (4434)

martyt -- Mon, 01/19/2009 - 15:44

Silverline Sonata III

Robert Harley -- Mon, 01/19/2009 - 16:02

It is likely that the two records have warp or eccentricity that generate very low-frequency information that your amplifier is amplifying and driving through the speaker's woofers. Low frequencies require more power, and the sub-sonic energy eats up much of your available amplifier power, causing the amplifier to clip on musical signals.

martyt -- Mon, 01/19/2009 - 20:27

Thanks for the reply Robert. That sounds reasonable, but the Cary amps at 50 watts did not clip, however the bass response was not near as deep as the MBL. The MBL's are the bass champs of all the amplifiers that I have had in the past 30 years. I have a Threshold amp that is 200 watts same as the mbl, and if memory serves me I think it has balanced inputs. I think it would be worth the effort to try, however it is the bottom box of a stack of components that I keep as spares. Some days that's how it goes.

Halcro -- Mon, 01/19/2009 - 22:57

I think Robert's answer sounds probable.
You could cure the problem and improve the overall performance of your system by adding 2 self-powered subwoofers like the Vandersteen 2Wq.
With its passive filter rolling off at 80 Hz, your MBLs will have far more headroom to drive your main speakers whilst the subs will give you better bass and better room response.

martyt -- Tue, 01/20/2009 - 13:15

Thanks for the advice, I don't have room for subs. If I find more records with this problem I will get the higher powered MBL amps. I like the sound.
Marty