Need Help: Decware + La Scala or KHorns

[ThomBoh]

Hi all, trying to troubleshoot an issue that's been driving me nuts. I'm near the end of my rope and hoping to hear from anyone here who has used a Decware tube amp with either La Scala AL5s or Klipschorns to see if the problem is with something in my system, or simply just a bad pairing of speaker and amp.

 

I have tried three different Decware tube amplifiers (two different SE84UFO25s, and the new SEWE300B) and have found that with all three of them, when paired with my La Scala AL5s, there is a loud 60 or 120 Hz (maybe both) hum. This hum is independent of gain/volume setting on the amplifiers, always the same volume. I measure this baseline hum at 59 dB in my listening chair using a handheld decibel meter (C weighted). To be clear, tube amps always have some small amount of hum in them, but this is very loud, and these are extremely highly regarded amps.

 

I know this kind of thing is often caused by a ground loop. I think I have ruled ground loops out: the hum is the same regardless of whether or not anything is connected to the inputs on the amps. Even when the only thing connected to power in the room is the amp, and the amp is connected to the La Scalas, I get the same hum as when everything is plugged in and connected together.

 

I have spoken to Steve Deckert about it and he very patiently listened and helped me troubleshoot. He thinks something is amiss, but I've checked all the standard causes. He suggested there's a possibility that the wiring/grounding in my home has something wrong with it. I had an electrician check it out today, and he said everything is good.

 

I'm really totally stumped. The problem is common across three different amplifiers, so I think it's unlikely that they're all defective in exactly the same way, somehow, and the 300B amp is literally brand new.

 

One suggestion Steve has offered, is that his amps always have some level of "inherent" hum to them, but he designs the amps such that for a 100 dB speaker, at listening position, the hum is inaudible or barely audible. He said there's a possibility that my La Scalas are so efficient that the hum is louder than one would want, but he did also say it shouldn't be this bad. For me, the hum is extremely audible.

 

So, I'd like to ask if anyone here has had experience using a decware amp (one of the SE84UFO models, or even the new SEWE300B) on their La Scalas or Klipschorns, and experienced this same kind of unshakable hum? It would be really helpful to know if this is just a bad match of equipment, rather than something I can fix!!

[Khornukopia]

35 minutes ago, ThomBoh said:

I had an electrician check it out today, and he said everything is good.

 

Because all 3 amplifiers exhibit the same hum, I would still suspect something like a bad light dimmer somewhere in the building.

[ThomBoh]

20 minutes ago, Khornukopia said:

 

Because all 3 amplifiers exhibit the same hum, I would still suspect something like a bad light dimmer somewhere in the building.

 

There are unfortunately no dimmer switches 😕 it's a small home that just has simple light switches. But yeah I would love to learn that there's an electrical gremlin lurking somewhere that can be fixed! Also, fwiw, I've never had hum problems with my non-decware amps (Primaluna and naim), but the decware amps are definitely more naturally prone to hum by design.

Edited February 21, 2024 by ThomBoh

[Idontknow]

I had this problem with my Decware Zen too. Contact Steve at Decware and ask him if he thinks you need to connect the two negative speaker terminals with a wire. He explained this in a forum and it worked but contact him first to ask. All I did was literally connect the two negative speaker terminals with a 7" single speaker wire. 

[ThomBoh]

17 minutes ago, Idontknow said:

I had this problem with my Decware Zen too. Contact Steve at Decware and ask him if he thinks you need to connect the two negative speaker terminals with a wire. He explained this in a forum and it worked but contact him first to ask. All I did was literally connect the two negative speaker terminals with a 7" single speaker wire. 

 

Thanks for for chiming in! So I did actually try this a while ago. On the SE84UFO25, if you're using it in normal stereo (e.g. not as a monoblock), this does help. Doesn't eliminate the hum, but does help. Unfortunately, as I learned from discussing this with Steve, you can't do this when using the UFO25s as monoblocks as I do -- but you can run them in balanced differential which fixes everything.

 

Unfortunately, for the SEWE300B amp, connecting the two negative terminals does not do anything for the hum in any scenario. I was really hopeful it would help, as I planned to use the 300B in normal stereo operation... alas.

 

Really hoping that someone here has tried Decware + La Scalas or Klipschorns! The only person I currently know of out there who has used a Decware SE84UFO amp with La Scala AL5 is Andrew Robinson, and he raved about it, but he is unfortunately not reachable to discuss things like this.

Edited February 21, 2024 by ThomBoh

[Khornukopia]

1 hour ago, ThomBoh said:

Also, fwiw, I've never had hum problems with my non-decware amps (Primaluna and naim), but the decware amps are definitely more naturally prone to hum by design.

 

Well, that is helpful information. 

[ThomBoh]

6 minutes ago, Khornukopia said:

 

Well, that is helpful information. 

The way Steve described it to me, if he completely eliminated the hum from his amps, he'd also eliminate some of the sonic signature that makes them so good, so there's a tradeoff there, but his design target is such that a 100 dB efficient speaker will put out a negligible amount of hum at listening position.

 

This hum will be louder at 105 dB, sure, but mine is pretty bad. What I'm trying to determine is whether or not this is completely the inherent hum of the amp (which means that Decware amps and La Scala AL5s and Khorns are just not a good match), or if there's something else going on in my case which is making it worse than it should be

[pnort]

I don't get any noticeable hum with Khorns and an 8600S Elekit 300B amp. LED lights can be a problem. If you have them, turn all of them off just to check.

 

I'm puzzled how "sonic signature" would be enhanced by keeping some hum. Actually not sure what sonic signature is.

[ThomBoh]

43 minutes ago, pnort said:

I'm puzzled how "sonic signature" would be enhanced by keeping some hum. Actually not sure what sonic signature is.

I'm paraphrasing here and I don't mean anything specific by "sonic signature". I hope I'm not misrepresenting what he told me, but what I understood was that to get his specific amps to sound the way he wanted it to, there had to be some small amount of residual hum that is audible from ~100 dB efficient speakers if you go up to the driver, but not from listening position. I don't know enough to debate the merits of that design choice. But if you take that statement for granted, then what I'm trying to objectively determine is if the extra 5 dB of efficiency of my La Scalas is causing that same soft hum built in to the amp to be amplified to an unpleasant level, or if something else is going on outside the amp

 

Unfortunately, no LEDs!

[Idontknow]

Yea, that's the one thing about Decware. They have a lot of hum issues. I messed around with their phono stages and couldn't get rid of the hum nor could the owner of it. Also, the youtube guys have been asleep for years on testing Decware. Wasn't until those reviews came out that customers were on this absurd 2 year waiting list. I sold my Zen and haven't looked back after receiving my modified ST35 and ST70. Decware are nice amps but there's other great amps out there too without these hum issues. 

[Marvel]

My ST-70 had zero hum on my LS, and very little on the 2a3 amp I had. The 2a3 amps had AC balance pots for each amp, but they were still pretty quiet.

 

You might try balanced AC... but the transformer would cost some to try. It's legal and been in the IEC regulations for years.

[Peacemaker]

4 hours ago, Idontknow said:

Yea, that's the one thing about Decware. They have a lot of hum issues. I messed around with their phono stages and couldn't get rid of the hum nor could the owner of it. Also, the youtube guys have been asleep for years on testing Decware. Wasn't until those reviews came out that customers were on this absurd 2 year waiting list. I sold my Zen and haven't looked back after receiving my modified ST35 and ST70. Decware are nice amps but there's other great amps out there too without these hum issues. 

And probably less expensive also. I had a ST70 for a few years and never had any hum issues.

[Flevoman]

I had already mentioned it to you, but I'll mention it here as well. Both my Decware Zen triode from 2014 and my Decware Taboo III were completely silent on my AL5. These two amplifiers belong to the group of the quietest tube amplifiers I've ever had.

[Shakeydeal]

I had a Decware Torii II on a pair of klipschorns a few years ago. While it was not as quiet as my Aric amps, it was nothing like you describe. I think you have a system issue and not an amp issue.

 

 

[hanksjim1]

florescent lights?

 

[jjptkd]

5 hours ago, Idontknow said:

Yea, that's the one thing about Decware. They have a lot of hum issues. customers were on this absurd 2 year waiting list. I sold my Zen and haven't looked back after receiving my modified ST35 and ST70. Decware are nice amps but there's other great amps out there too without these hum issues. 

 

 This is the first I've read about this I almost put myself on that list a few years back when the wait time was 8 months I believe? I cannot image the upset I'd have felt had I waited all that time to receive a hum master. Two year wait time is unacceptable in my book- an 8 month wait was for me back then but to each their own I guess. 

[Shakeydeal]

24 minutes ago, jjptkd said:

 

 This is the first I've read about this I almost put myself on that list a few years back when the wait time was 8 months I believe? I cannot image the upset I'd have felt had I waited all that time to receive a hum master. Two year wait time is unacceptable in my book- an 8 month wait was for me back then but to each their own I guess. 

 

Yeah I wanted to get on the list for a new Torii a couple of years ago. Glad I didn't. My custom Aric Audio 300B amp only took five weeks from commission to receipt. And as good as Steve's work is, I think I made the right decision.

 

[Idontknow]

Kevin does a good job sharing his experiences with less known amps.

http://www.glowinthedarkaudio.com/

 

[richieb]

I also owned a Torii IV and while it wasn’t the quietest tuber I’ve owned there was more “noise” going on than say my

ST35 or QS Horn Monos both of which are dead silent through LS and Jubilees. But there was no overt hum as you are describing.
The absolute forest of tubes on the Torii and enough background noise to annoy me led to selling it. Idontknow is right about the 

Kenny Russell ST35 though, it is an exceptionally nice piece.

 

[Marvel]

Here is the document from Peavey about a balanced electrical system. It's basically a 120 volt transformer with a center tap that the connects to the downstream ground. each of the hot wires are then 60 volts. This is worth reading.

 

 

PWRDIST.pdf

 

 

Are you in your own home or a in a building that has a 208 volt three phase system for the building? If so, the way the 120 line is derived could be the problem.