Thanks. More of a tube rush sound as the hum through the woofers is slight. The tube rush sort of hiss is strange? Hiss is a ground issue? I know a 60hz hum is grounding, but hiss?
I know the unit is two years old. Perhaps the seller will pay for it.
This is amp sounds amazing on my Harbeth 40.1 speakers! Wow. |
I just received a used unit here on the Tom. I hear a lot of hiss and hum out of my speakers and my system has been dead quiet with all the other amps I have owned. Is this hissing noise and hum somethinhpg you guys hear? I hear it at moderate to loud volumes. |
How did you bleed off gain at the inputs? Speakers are 84db effecient and my tube preamp I am not sure about. It is not high gain however.
The top cover is warm, however I am talking about the heat sinks on the back of the amp only. These sinks get very, very hot. |
Devil boy, my heat sinks get so hot I cannot keep my hand on them for even a second when I crank the volume. Do you find this to be true? burning hot.
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Understand. The heatsinks are only warm at low volumes, but very, very hot at high volumes. At idle, just warm. |
George knows I have owned, modified, and built LDR passive units so I know them well. I also know they would be a great match with this amp. Problem is I a/b'd my DIY preamp against a Tortuga LDR and my active was just more pleasing. I love George's LDR also. However, this was with a different amp and speakers. It may be time to try that comparison again as things have changed.
My preamp does not send out a spec of DC as I measured one, twice, and even a third time over a span of time.
I have written Goldmund and hope to fix the issue myself. |
With my volume control at 9 the music is at 80db at 10:30-11 the music plays at 90db or so average weighted C scale. No real noise to speak of until I get to 11AM and then it starts be become loud. If I play my music under 85-90db all is well. If I turn the volume up to 2 or 3 the noise is quite loud through the speakers with no music playing obviously. I hear a moderate buzz combined with loud hissing. The hissing sounds like tube rush, but I hear none of this with all other amps I have paired with my DIY preamp.
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George, my speaker is 84db and the input impedance on the Job amp is 51k. Amazing sounding amp. I have read that older units had a grounding issue that caused the noises I am having. |
Thank you very much srosenberg as this is a mighty fine idea. I was thinking of just using Rothwell attenuators, but they may degrade the sound? I have not used the Rothwells before. I love this little amp. Best value in high end along with the Lightspeed attenuator. |
Seems the Rothwells do change the sound in some not so great ways. Great LSA idea. |
I wonder what the input impedance of the Rothwell devices are as George makes a good point. I believe the input impedance of the LSA is 20k and that is not a good match for the output impedance of my tube preamp. |
I am sure my rig is passive friendly, but I really want to keep my self designed and built tube preamp. The output impedance of my preamp varies with the volume setting. I use a shunt style stepped attenuator made by Khozmo. I measured the output impedance over the volume range I listen to and it changes from 360 ohms to 1k ohms. According to George this may be to high for proper matching with the Rothwell attenuators.
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George read my post above yours and give me your thoughts on the Rothwell. Hard to part with my preamp as it was a three month DIY project. They sound fantastic together. I do want to reduce the hiss and think you are absolutely right about too much gain.
I can also reduce the gain in my preamp by changing out the plate resistor value I suppose. |
