C325bee alignment

[jkasch]

Hello,
I'm trying to determine why my NAD sounds so slow and muffled next to a supposedly inferior HK3480 receiver. I purchased a service manual and the alignment procedure is as follows:

ALIGNMENT PROCEDURES

I. INITIAL

A. LOWEST VOLUME ADJUSTMENT

1. Tune the volume pot to lowest state.
2. Input a high voltage signal such as 5V from CD input.
3. Connect an oscilloscope to L channel binding posts.
4. Observing the oscilloscope, adjust VR301, make the output of speakers become to the lowest level.
5. Adjusting VR302, make R channel output become to the lowest level by same way.

B. IDLING CURRENT

1. Level power on for a minimum of 5 minutes
2. Connect a DC voltmeter toTP1 and TP2, adjust VR22 for 4mV reading on voltmeter.
3. Connect a DC voltmeter toTP3 and TP4, adjust VR12 for 4mV reading on voltmeter.

C. ISC CIRCUIT ORIGINAL ADJUSTING

Adjust the pot VR3 to make the DC voltage of the point of TP10 to the same as TP11

I can figure out A and B, but C makes no sense to me. Also, doesn't 4mV seem low for the idling current? The HK's is 21 mV and it runs cooler than the NAD.

Any help is appreciated. I just barely know what I'm doing here. Thanks.

[Bill_P]

From the manual: The ISC circuit switches the power supply to lower voltage when the load impedance is low, or the temperature on the heatsink is over 80C degree.

The adjustment tunes the threshold of the protection circuit. Connect one probe of your meter to TP10, the other probe to TP11, and tune VR3 for zero volts.

4mv is a voltage, not a current. The current scale factor depends on what resistor value is used to sample the current. In other words, you can't compare the adjustment voltages between two different designs and tell anything about the relative idling currents.

I doubt that any of these adjustments will make much difference in how the amplifier sounds. I used to own a C325BEE and found the sound to be flat, lifeless, and constricted. Nature of the beast, I'm afraid.

[jkasch]

Thanks for the quick reply. That helps a lot.

Since we seem to have a similar assessment of the NAD's sound, do you (or anyone else that cares to chime in), have a recommendation for an integrated in the $1500 range?

[Bill_P]

I replaced the C325BEE with a NAD C372 I found on Ebay. It was broken but only needed new main power supply filter capacitors so my total cost was only $165. The C372 is much much better than the C325BEE and I can recommend it as a replacement. I'm sure there are many other integrated amplifiers that would suit your needs. Buying a used one-generation old amp should save you lots of money.

[jkasch]

Well, the idle current for one channel was 2.3 mV and the other was 5.2 mV. Setting them both at 4.1mV (as close as I could get) really tightened the overall sound. Instead of being dominated by muddy bass, I hear greater clarity across the board.

Placebo or Hawthorne effect? Time will tell.

[sakis]

that is not placebo ....treat your shelf with an other approach ...something like from another school ...

that machine will have to be simply made ... with quality material ... without switching rails and 50 adjustemnt points something like a rotel for example .... listen to a machine like that and i belive that you are simply going to trush the NAD ... or remove 2/3 of the parts from inside to be able to listen some music from it

any amplifier like the dx / or the P3A / or an AKSA / or a symasym .... with even a passive source selector and a potentiometer to control the volume will make loose the ground under your feet next to NAD ...

now if take the best of two schools and use a P3A amplifier from solid state ....and use it with a B1 buffer from pass labs that will make you even more happy and will satisfy you for more than 20 years !!!!!

there is machines good enough in this forum to blow both your soul and ears !!!! enjoy !!!