• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

My Experience with "Music Angel" EL34 PP

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Just to finish off on the EL34 Winged C Svets vs JJ shootout in the Music Angel.

First I'm running the thing in triode mode. I had another run on the weekend swapping output tubes. I tried Winged C Svetlana EL34, JJ Electronics EL34, Sovtek 6550 and Chinees (the Bird Symbol??) KT88 all biased at 50mA idle.

Again I thought that the JJs had more detail and better overall frequency (lows to highs) than anything else I tried. Particularly better in the top end. In the Music Angel this was NOT all positive news - the extra detail highlighted inadequacies in other parts of the amp circuit.

As a final check I pulled out my "Menno Bricks" which have been sitting on my shelf waiting their turn for a redesign. These consist of 12AU7 CC/Concertina Splitter driving 4 x EL34 Triode mode Parallel push pull into VDV2100 Toroidal Output Transformers. I had gone only as far as ditching the 12AU7 for ECC99 and then shelved them until such time as I could get round to designing a new front end phase/splitter/driver for them. The JJs in the Menno Bricks really showed their superiority. Also I had forgotten just how good these amps are - not withstanding the wimpy front end and the load being presented to the concertina by parallel triodes. These amps run 485V on the anodes (which did'nt seem to worry the JJs at all) with separate fixed bias to each tube. With all 4 tubes set for 50mA I checked bias volts to each tube, all within a 1 volt of -40V (ie the matched quad WAS well matched).

The JJs ran faultlessly.

SUMMARY:
In a 2nd rate amp the "Winged C" Svets were the go as the JJs were a bit too revealling.
In a top notch amp the JJs won "hands down".

Cheers,
Ian
 
Music Angel XD-SE hum

Hello all,
This is my first post, and I'm a complete idiot when it comes to the inner secrets of audio gear. That said, I'm really enjoying my new amplifier, apart from an irritating hum on one channel. I've also noticed that the volume control seems dirty, as it makes a bit of a crackle when I wind it around.
Any of you wise people have any ideas how I should troubleshoot this? Maybe a spot of servisol in the volume control??

Thanks for you help in advance!
-Peter
 
Re: Music Angel XD-SE hum

Peter Pearse said:
Hello all,
This is my first post, and I'm a complete idiot when it comes to the inner secrets of audio gear. That said, I'm really enjoying my new amplifier, apart from an irritating hum on one channel. I've also noticed that the volume control seems dirty, as it makes a bit of a crackle when I wind it around.
Any of you wise people have any ideas how I should troubleshoot this? Maybe a spot of servisol in the volume control??

Thanks for you help in advance!
-Peter


I use Deoxit to clean 'scratchy' controls. Works well but has a little smell to it. Not really obnoxious but do the spraying and cleaning outside, in the basement or the garage if you can.

How old is the amp? If it is an older amp (even if it is new) it may have a bad coupling capacitor which could be contributing to the noise in one channel. It could also be a bad solder joint or poor ground connection or even a tube.

Try changing tubes from one side to the other and see if the noise follows the tubes.

BTW, if you aren't familiar with tube gear then be extremely careful when poking around inside one. They generally operate on lethal voltages and the caps can often retain a charge for a very long time after the amp is turned off and unplugged.

Read the thread here on safety before opening up your amp.
 
Hi Ian,
Is this the same amp as supplied by DIY HiFi (Ella) do you know? I bought one some time ago, I'm not in your class as to tech expertise but I fitted the optional psu choke and changed all the resistors to kiwame but it still sounded crap to me. I think it had a 6SN7 front end. Now I'm wondering if it came from the same factory and if it had the same initial faults as yours did. I guess I will never know now but your thread was very interesting. The JJ importer here will match tubes before sending if you ever need that facility. It is only across the ditch.
Phil.
 
Problem solved !

My version of the EL34B Music Angels uses a seperate powersupply (seperate winding on trafo) for the 6SN9 (so the supplied scheme is outdated...). With the scope I saw a raw sinus after the first rectify diode where I would espect almost DC. Turned out to be a defective bufferelco (250V/120 microfrad). Replaced it and the hum is gone...
 
valve amp ebay china el34 el84

These amps are great fair play but, theres a big but they take ages to arive, and also there is somefeed back from the amps through the speakers. the other thing is mine packed up after 4 months and then when I eventually got hold of the seller they said send it back and when they get it back they will forward it on to the factory to be reapired, while i foot all the postage charges. It should take about 2 months they say, but I would be suprised if I ever got to see it again, so they may be cheap but as long as you know you get what you pay for.
 

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Re: valve amp ebay china el34 el84

eddiedavies said:
These amps are great fair play but, theres a big but they take ages to arive, and also there is somefeed back from the amps through the speakers. the other thing is mine packed up after 4 months and then when I eventually got hold of the seller they said send it back and when they get it back they will forward it on to the factory to be reapired, while i foot all the postage charges. It should take about 2 months they say, but I would be suprised if I ever got to see it again, so they may be cheap but as long as you know you get what you pay for.

Cheap stuff you end up buying it twice.
 
Hello everyone
Interesting Forum, and a lot of interesting people!

I also have a Music Angel with 6N1-M + 2x 6N9-P + 2x EL34-B

I would like to try the ECC88 on the input stage, because i read it has a great detailed sound (and because i have one...).

Now i see, that the ECC88 has a Va of ony 130V, and the original (6N1-M or ECC85) has 250/300V

Has someone measured the anodevoltage at this point (Anode inputvalve)?

Will i blow up the ECC88?

Other good tubes i should try?

Greetings
Christian
 
I wonder if anyone would offer their services to upgrade one of these amps for those of us that can't.
The sort of thing gingertube is talking about I sorely want done to my amp, but I don't know.
I've got the schematic now though, that should help.
Still need someone else though, I'm useless
 
Re: Music Angel xd500 BK tube amp hum

asoundpainter said:
Just bought this lovely little amp. Listened for approximately 15 hours - decent sound indeed. Then powered up to annoying hum in the right channel. Any suggestions? Please let me know!!

My guess, a bad cap. I'm not certain how many are in the circuit, but one of them is not up to spec on the right channel. You may be forced to replace all of them sooner or later.


I looked as a couple of pictures, and from what I can see, I see ten electrolytics, and five propylenes on the pcbs.

I am not certain what to tell you because you will be hard pressed to enforce some sort of warranty from china. That is the "crapshoot" part of getting them from there.

I wish you luck.
 
Re. ammmoying hum.

Since the amp is new from China, you should open it up and check for any loose wires / shorts / bad soldering. Workmanship is usually a little sloppy on these, and transport may also do some damage.
Also check voltages and bias settings for both channels.


SveinB.
 
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