Forums - Print Page

Forums
https://www.decware.com/cgi-bin/yabb22/YaBB.pl
OLDER DECWARE GEAR SUPPORT >> CSP, CSP2, CSP2+ >> Hum when using CSP2
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1273875294

Message started by Solidus on 05/14/10 at 23:14:54

Title: Hum when using CSP2
Post by Solidus on 05/14/10 at 23:14:54

Hello,

I have recently bought the CSP2 and although I think the soundquality is great, I have been experiencing hum since day one.

I am using Beyerdynamic DT 990 (600 Ohm) headphones with the CSP2. Ever since I have installed the 6N1P tubes with a 5U4G I am hearing slight hum. I have rolled the front input tube with a 6922 tube but still heard som hum.

By now I have rolled all tubes with a 5Y3WGTA tube and three Mullard CV 2492 tubes. Still with the same result..

Is there someting wrong with my unit or am I just having bad tubes? I have also noticed that the front tube isn't firmly attached into the socket. Could this be a problem?

Title: Re: Hum when using CSP2
Post by Rivieraranch on 05/15/10 at 03:44:30

You may wish to run through all the checks for what could be causing hum. You could lift the ground on the plug. The CSP2 is intrinsically quiet. I know because I have 2 of them. Is the unit subject to a source of high magnetic interference such as computer, etc? Is it plugged into the same fixture as a fluorescent light? You should run through all these checks and then give Steve Deckert a call.

Title: Re: Hum when using CSP2
Post by Solidus on 05/15/10 at 11:55:32

Thanks for the fast reply! Much appreciated.

I have changed my tube setup a couple of times and I have come to the conclusion that: when using two 61NP tubes and one Mullard CV 2492 tube my unit is indeed quiet (as should be). I think it must be a bad tube(s).. I will try to return a Mullard CV 2492 and see what happens.

Will keep you updated!

Title: Re: Hum when using CSP2
Post by Rivieraranch on 05/15/10 at 14:07:48

The input tube has the most overall influence on the sound. You may wish to acquire some JAN SYLVANIA (not Phillips) 6922's for drivers.

The 6922 family is prone to oscillation and microphonics if driven too hard. Sometimes they just fail. I have had JJ's fail after only a few hours and Electro Harmonixes have gone microphonic on me.

Title: Re: Hum when using CSP2
Post by Rivieraranch on 11/08/10 at 02:00:01

I recently encountered a bad batch of 1976 6N1P-EV tubes that hummed like hell. I ran them for 10 hours and they did not quiet down. They maybe never will.

Title: Re: Hum when using CSP2
Post by Juan Antonio on 11/12/10 at 11:23:17

Although this post is old, I'd like to note some points:

The hum also depends on the interaction between the transformer and the cables.

The power cord must be bent backward a little bit to keep away from the transformer as much as you can. The same for the interconnects and the headphones' jack. The shielding of the cables is important too. The higher the headphone impedance the better.

Swapping tubes to identify each noise from each tube too. The front socket is the tool for this. When you find the lowest noise possible from the CSP2, the front preamp tube is the one you should use there.

But you will never totally remove the background AC noise from the transformer . I'm referring to the electrical 50Hz/60Hz noise. The hiss that you hear is mainly from tubes.

Title: Re: Hum when using CSP2
Post by Rivieraranch on 11/13/10 at 17:33:01

You are so right, Tone. One of my interconnect cables had an end plug that was not screwed on tight and that was inducing him. Until I tightened it; then there was no hum. Right now I have a socket saver to determine which tubes are good and which are bad.

Title: Re: Hum when using CSP2
Post by agustinf on 01/04/11 at 18:00:35

Hi,

I am having hum myself in a brand new CSP2plus, and wanted to check if I got the preceding instructions right: people find that rolling tubes help with hum issues? I thought that hum could only come from having several (A/V) devices plugged into the same wall and into themselves (your DVD into the preamp and into the TV, making the TV and the preamp "connected"; and then add apple tv, comcast, Roku, etc. All things I´d happily throw away, but I can´t).

So, can tube rolling be of any help?

Regards
Agustín

Title: Re: Hum when using CSP2
Post by Juan Antonio on 01/04/11 at 23:15:00

Agustín, not only certain tubes, cables are important here as well and its shielding: Good signal/power cords,... Your other devices are inducing hum to your CSP2 as well, specially if you aren't using good receptacles or filter/isolation transformer, etc to isolate it from the others.
Also The problem I see here is that the CSP2 is not absolutely quiet like some people say. They say that it's completely quiet or very very quiet but I don't know if they are referring to a good quietness for a tube amp or.... What is dead quiet, for example, is my solid state SPL Phonitor headphone amp or any decent SS. It's just absolute silence. The CSP2 is just very little noisy when high impedance headphones are used. Just using for example 32 ohm Grado's are quite noticeable. As a preamp is less problematic. Headphones are more sensitive to hum. But even using it as a preamp is a bit noisy, specially when you turn the trim pots up. I even think that every single CSP2 is built a bit differently and unique. Some probably are a bit noisier than others.

Of course, what SS amps can't achieve is the incredible "music" that tube amps deliver. In general tubes are musically way better, warmer, richer, better timbral, etc.

Title: Re: Hum when using CSP2
Post by settembrini2 on 01/07/11 at 17:47:33

Hello,
my experience with the CSP2 is the same: if you use a headphone like the AKG K701/702 with an impedance over 50Ohm (it has 62Ohm), a Beyerdynamic Tesla 1 (600Ohm) or the Sennheiser HD 800 (300 Ohm) you cannot hear any noise-floor, the amplifier seems to be dead quiet.

If you use the new Ultrasone Edition10 with 32Ohm impedance (it's a pity, because that's indeed a very expensive, but unbelievable musical headphone...) or for instance very susceptible highclass InEar-Monitors with an impedance about 16 to 30 Ohm, you can hear, that the CSP2 is rather noisy - compared with my SolidState Burson HA-160, which is really absolutely dead quiet with every headphone or IEM.

I think these hum-problems are typical for all tube headphoneamps... that's the price for their undenieable amenities...

Title: Re: Hum when using CSP2
Post by Juan Antonio on 01/08/11 at 18:18:54

"my experience with the CSP2 is the same: if you use a headphone like the AKG K701/702 with an impedance over 50Ohm (it has 62Ohm), a Beyerdynamic Tesla 1 (600Ohm) or the Sennheiser HD 800 (300 Ohm) you cannot hear any noise-floor, the amplifier seems to be dead quiet."

You cannot literally? Using my 300 ohm headphones is still easily audible in my case. Easily to hear, but far from noisy.

Title: Re: Hum when using CSP2
Post by Damien on 08/21/11 at 22:20:39

I had a hum in my CSP2+ that turned out to be a bad rectifier. (5U4G) One email to Mr Deckert got a new one to me pronto. Now the problem is gone. The bad rectifier was also rattling after a while.