Valve Amp Throbbing Hum

[lilmountain]

Stupid question, how do I message members as in the two recommended pros? Can't see an option to do so or is it because I'm too new?

Secondly is it worth me getting another 22de4 rectifier first to see if it's simply a failing tube or do the symptoms suggest it's the amp rather than the tube assuming the 'motorboat' sound is a symptom relating to the power supply?

Thirdly looking the 22de4 up they seem mostly to be from the States with huge postal costs and lead in times. Is there somewhere in the UK that has this kind of stock available or indeed someone on this forum?

 

[Lurch]

@lilmountain
To PM click on username then select 'start conversation' alternatively select Inbox then start conversation, when you start typing the username into the too box the system will start giving you username options, when the one you want appears click on it to select. Than off you go.

 

[rabski]

As above. Re the 22DE4, unlikely to the extent of near impossible. Rectifiers, especially half-wave variants are almost always work/fail. My personal advice would be not to throw any money at it before getting someone to look at it.

Side note to James: a quick pic search suggests a not unexpected set of what looks like four fairly high current diodes on one of the boards

 

[lilmountain]

Hi all, quick update; I've contacted @Juancho and plan to drop it this Friday with a potential 2 week turnaround. I sent David a recording of the hum and his initial assessment was that it wasn't a 'motorboat' thing but feels the issue is fairly straightforward so fingers crossed! Will update on the issue and solution when I get the amp back for completeness of the thread.

 

[Tarzan]

I use a chap in Romford, Essex if that is any good for you?

 

[bencat]

But what do you use him for ? Does he mind ?

 

[lilmountain]

Hi all, this is still with @Juancho but he's confirmed that actually it's dodgy valves, the pre 6SN7's. Bit of a noobie mistake on my part but you don't know what you don't know! Whilst I've got it with him I've gone the whole hog of upgrading the capacitors since I intend to keep the amp for a number of years. He was very complimentary of the sound and quality in general and will take pictures of the innards and upgrades that I'll share on here for anyone following this or future Cayin CS-150a owners.

 

[Tarzan]

But what do you use him for ? Does he mind ?

Wouldn't you like to know sweet cheeks.

 

[toprepairman]

So what was the final outcome with this?

 

[toprepairman]

Still no reply, interesting?

 

[lilmountain]

Still no reply, interesting?

Apologies it’s been a bit manic, I promise I’ll be back with a full response!

 

[Juancho]

Apologies it’s been a bit manic, I promise I’ll be back with a full response!

Also covered here:
This lovely amp was the one with the noise issues reported elsewhere. It was simply the 6SN7s. As soon as I saw the script Golden Dragon on these I knew what the issue was. Funny thing is Golden Dragon make some great tubes and I have 845s, 300bs, ECC 83s and 82s that sound really sweet. I've got a stock Radford tt100 a refurbed sta100 in the workshop at the moment and this amp comfortably outperforms both. With remote, variable feedback, ul and triode modes, I'd say it's one of the top valve amps out there at the moment.

 

[toprepairman]

Ok thanks for the reply.
Never had any problems with 6SN7's so was puzzled by the diagnosis, but then not had any Golden Dragon ones to play with. I shall bear that in mind as and when I run into any.

 

[Juancho]

Ok thanks for the reply.
Never had any problems with 6SN7's so was puzzled by the diagnosis, but then not had any Golden Dragon ones to play with. I shall bear that in mind as and when I run into any

All the good ones I've come across have been from the official Ming Da importer. The faulty 6SN7s were ordered over the internet and the ones in this amp of unknown provenance, so these may well be takes or 2nds for all I know

 

[Psilonaught]

I also recommend David at Essex Amps, he has a vast amount of tube amp experience and is also an authorised icon audio service shop.

 

[lilmountain]

Hi all, so in summary the fault was the valves 6SN7’s but whilst I had it with @Juancho i bit the bullet and invested in upgrading the 8 input and output caps with ODAM V Caps. The sound is incredible even with my relatively modest AE509 floor standers.

The highest accolade for this amp is that @Juancho bought a new one for himself and did the same upgrade!

Since then I’ve been plagued with bad pre stage valves that I’ve raised in another thread. There is also a strange anomaly around the previous deathly quiet of the amp with no music where this is still a very slight hum and odd crackle but only with your ears right up to it. But I’ve let that go given how good it sounds when it’s playing.