Jensen or Mundorf coupling capacitors?

[timm]

Well. Yes. The hum appears to be the dac. I don't have a volt meter. But I can get one. I disconnected everything from the dac - unplugged everything from the wall - hooked it up and got a hum. But not initially.

Going direct to amp there is no problem. No hum etc. also - the hum is intermittent when going dac to the pre. I have decided to change interconnects from the dac when I hook it back up.

[Formerly YB-2]

If were me I would call Cary and read them my post above with all the time-frames and issues.

That said, being in a 'good' neighborhood means nothing about your power. I live in a 'good' neighborhood with all underground service. Adding a SurgeX surge protector/noise reduction unit made a nice improvement in my system.

[timm]

Originally Posted by decooney

When you unplug/plug in your devices (one at a time), have you figured out which one causes humm first? When you find it, measure the voltage on the RCA interconnects, what do you get?

Let me ask a stupid question. When I measure this - red on the pin and black where ? On the metal part surrounding the pin that connects external to the female jack? Measure this with dac off and dac on? With/ without cheater? Do we have an idea what an acceptable measurement might be?
Thanks.

Btw 48hrs running straight - no input no outputs connected and no issue. Adding amp back to do same test.

[decooney]

Originally Posted by timm

Let me ask a stupid question. When I measure this - red on the pin and black where ? On the metal part surrounding the pin that connects external to the female jack? Measure this with dac off and dac on? With/ without cheater? Do we have an idea what an acceptable measurement might be?
Thanks.

Btw 48hrs running straight - no input no outputs connected and no issue. Adding amp back to do same test.

Connect RCAs to the input device, DAC, whatever source it is you are plugging in into your preamp. I use the RCAs as an extender for measuring.

On the other end check ~DC voltage, look at specs on your device. Should show output voltage. You are checking for something real high or low in voltage.

Also, I check the free Line Out output jacks on the SLP98 to see what's coming out. One pin on the center (positive) and other on the outer shield (ground)

[timm]

Thanks decooney. I really appreciate it. Taking baby steps.

Tonight once I added the amp - I started getting a very low level hum in one speaker that flipped to the other when I reversed left and right inputs. This did not go up or down w volume level change on pre. I discovered that my new power cord on my amp (heavy shunyata) was sagging a little in the outlet. I put a rubber vibrapod between it and the cord below which propped it up snugly in the outlet. Low level hum gone from amp. Small success. . Next step - get the volt meter.

[decooney]

Right on! Good for you. Keep up the good work. A lot of times I always start with the stock stuff, even the stock Cary power cords, and go from there. It's strange how some times we all think (me too) we are making it "better", and then add something aftermarket for extra spice and the yet part does not quite fit or work right how we hoped it would... yep, hanging or unseated power cord. I bet that one gets a lot of us. Have fun.

[timm]

So fuse in power supply blew again in the Cary. Just amp connected. Prob ran for 5-20hrs.

So this is not source related.

More info. My amp - sunfire signature does not have a ground plug on the male adapter on the back of the amp. It has impedance of 24k ohm.

The fuse- I'll tell you - it doesn't look blown as I see no break - but a new one powers it back up.

[timm]

A 1 1/4 amp fuse has been suggested vs the 1.

I guess the question for me is - can hooking the amp to the output of the pre wreak havoc and blow something in the external power supply after 20 hours? And based on tests - this only occurs when amp is connected to pre.

Could any external static cause issues. Maybe a stupid question. But I need to discharge myself before I touch anything. I think that's going down a rabbit hole.

[W9TR]

Get a Kill-a-Watt or something similar to measure how much current the 98 is drawing by itself and then in the system. They are about $30 and have a lot of other uses around the house.

I'm guessing that the 98 is oscillating at a high frequency when connected to your other gear and drawing a bunch of current, blowing fuses as a result.

Increasing the fuse size sounds like a bad idea since the preamp runs fine when it is not connected to anything. Something is amiss. The preamp shouldn't draw any more power driving the inputs of your power amp than it does sitting unconnected.

You shouldn't have to use a cheater with any well designed audio gear. Ever.

You might try connecting the preamp ground lug to ground lugs on the DAC and power amps if they have them.

Tom

[timm]

Thanks. Yah. Something is amiss. I troubleshoot all the time in my work and this is as simple as it gets. It used to work ... what changed.

Either something went south in the amp (although my dac direct to the amp has had no issue) or something is bad in the pre - but only occurs when a load or resistance is hooked to it.