Sensation Quirks

virtue · « **on:** 23 Aug 2010, 04:40 am »

Guys,

I noticed a faint "rustling sound" through the speakers when adjusting volume on my Sensation (more noticeable when no musical content is present). One other customer noticed this sound and I heard it again today from a second. The sound cannot be heard when the POT is not moving.

Also, if you hard-shut down the the amp without first turning off the amp on the front panel, the computer gets confused and may not come back properly.

We will be finishing the manual this weekend and noting these "quirks." There is no way for us to change this behavior.

Our amps are fantastic in many, many respects. If you must have perfection, please take advantage of the money-back return policy, 30 days from delivery.

I've nearly bankrupted myself several times dealing with more significant issues that we did not catch prior to production. Thankfully, this is not one requiring me to fall on the sword.

You will decide whether this is a show-stopper for you, or not.

Very best,

Seth

kylek · « **Reply #1 on:** 23 Aug 2010, 05:47 am »

Does the noise occur only when the remote is used or also when the volume is adjusted manually?

dboulet · « **Reply #2 on:** 23 Aug 2010, 06:29 am »

I've noticed the rustling noise when turning the volume knob manually on my Sensation, but always thought that it was caused by the microphonic effect of the tube in the buffer.

Wind Chaser · « **Reply #3 on:** 23 Aug 2010, 06:40 am »

Quote from: dboulet on 23 Aug 2010, 06:29 am

I've noticed the rustling noise when turning the volume knob manually on my Sensation, but always thought that it was caused by the microphonic effect of the tube in the buffer.

I'll bet the farm that you are correct on that one!

virtue · « **Reply #4 on:** 23 Aug 2010, 07:31 am »

I only have the tube buffer version. It occurs when I hand-crank or when I use the volume control. Definitely strange. I found myself looking around for a crunching leaves in the living room. With music on, it's barely noticeable. But yeah, strange.

cgreynes · « **Reply #5 on:** 23 Aug 2010, 07:48 am »

Mine is ok. My wife and I still love it. Did not hear any unusual sound when cranking up the volume with or without music. I have a M451 with 80w ps. No upgrades yet including tube buffer. Speaker is 87db sensitive.

Wind Chaser · « **Reply #6 on:** 23 Aug 2010, 08:12 am »

Quote from: virtue on 23 Aug 2010, 07:31 am

I found myself looking around for a crunching leaves in the living room.

Fresh air is nice but you might want to close the window.

tw_switzerland · « **Reply #7 on:** 23 Aug 2010, 08:55 am »

Seth,

Maybe only tube buffered versions show this noise.

When you switch off the tube buffer, is the volume pot silent then?

If it was the tubed version only, maybe Gary would know a solution to that problem.

Thomas

dba · « **Reply #8 on:** 23 Aug 2010, 09:53 am »

I'm not sure if this issue (loathed to call it a problem) should be solved ...

Why?
...if the issue is resident with or without the tube buffer and the occurrence is during spl setting, unless you're using your amp as a pseudo pitch device as a budding DJ, it shouldn’t detract from the listening experience.

I say this coming from the other end of the spectrum of having reviewed many amps that cannot cope with mains derived noise or do so in such a way that they negatively effect the audible spectrum while listening - its certainly something for Seth to put on the short list to 'better' in future products however, we all like a challenge

So far, i've not heard anything i wouldn't expect with my tubeless M901 except slight 'air' - but i expect this as i use highly sensitive Planars

momini1 · « **Reply #9 on:** 23 Aug 2010, 12:26 pm »

Yes, I've heard it, too -in fact, just a minute ago when I turned it on the for the day. Sort of like a scratchy volume control but it seems to only be in the first 1/2 of the volume knob sweep. I don't think I ever noticed it before the Dodd mod. For me it's a non-issue as I don't hear anything when a source is employed. The amp is dead silent once the volume is set.

PSB Guy · « **Reply #10 on:** 23 Aug 2010, 01:55 pm »

No issues here with an unmodified M901, FWIW...

Cornelis

Mariusz · « **Reply #11 on:** 23 Aug 2010, 03:28 pm »

I have noticed it on the buffer version however, non-buffered version has no issues. Need to do some investigation befor I jump to conclusion.

Mama Virtue · « **Reply #12 on:** 23 Aug 2010, 03:48 pm »

In regards to the "computer/power" stand-by issue, if you are following the sequence below, you have probably never encountered an issue with it. If you are in a hurry and miss one of the steps, it seems that the stand-by "issue" may or may not occur, it's quite random.
From what I've found our protection circuit keeps the unit in protection mode until the capacitor fully discharges. about 2 minutes is a safe number.
When the protection is activated the amp will stay in "pre power" standby in which only the red lights will be on and the power switch will be un usable. This protection mode keeps the power relays from activating in order to keep the amplifier safe.
Here's the power down sequence and the power up sequence is the exact opposite.

Power Down:
1. Turn off front power switch
2. Turn off back power switch
3. Unplug power supply from wall, let it discharge fully
4. Unplug power supply from Sensation
5. Switch to batteries or whatever you shut the unit down for (switch
the Tube buffer on/off?)

Power Up:
1. Plug batteries/power supply into amplifier
2. Plug power supply into wall
3. Turn on rear power switch on the amplifier
4. Wait for the standby circuit to stabilize (about 3 seconds)
5. Turn on amplifier using front power switch.
Let me know if you have any questions.

ebag4 · « **Reply #13 on:** 23 Aug 2010, 04:18 pm »

Not exactly the same but possibly related. I have a Dodd DIY Tube Buffer, with a 5751 tube I was experiencing the same type of noise described when changing volume with either the remote or manually. I picked up a Amperex 7308 and now the buffer doesn't make any noise at all when changing volume, FWIW.

Best,
Ed

CSI · « **Reply #14 on:** 23 Aug 2010, 04:51 pm »

I think the tube may be the key and, particularly, a 5751. In an exchange with OzarkTom yesterday he pointed out the 5751's will be noisier in the circuit because of their lower gain. I didn't hear the "rushing" sound until I put in a 5751 (no problem with the stock JJ or a Mullard). I also have a very slight hiss noticeable even with the volume down and the Sensation in mute. I have to be within 6 inches of the speaker to hear it. My wife hears it from the next room but she is notorious for being able to hear a mouse peeing on a blotter at 60 paces.

Since the rushing noise only happens when the volume is adjusted and in no way interferes with the music, and since the Sensation sounds, er, sensational - particularly with the 5751 tube, I'm ready to declare this a feature, not bug.

dboulet · « **Reply #15 on:** 23 Aug 2010, 10:45 pm »

I tried switching the tube buffer off, and the rustling remains. Also note that I'm using the stock JJ tube.

As others have said, the amp is silent once the volume is set, so the issue doesn't really bother me too much.

kylek · « **Reply #16 on:** 24 Aug 2010, 01:19 am »

Was the volume control modified with the tube buffer installation? Is it possible that mounting the switch on top of the board somehow introduced DC into the pot?

tabrink · « **Reply #17 on:** 24 Aug 2010, 02:01 am »

I had that sound with both my buffered and unbuffered. So I quit using that particular POT.

virtue · « **Reply #18 on:** 24 Aug 2010, 02:19 am »

looks slick, darth vader!

tabrink · « **Reply #19 on:** 24 Aug 2010, 02:35 am »

Best of both worlds as I can still use my slick hunka hunka Virtue remote