Hi
I have a Music Angel Class A Integrated Amplifier EL34 x4 XD500MKIII.
I wonder if anybody as a working circuit diagram most of the one's on here are of other versions of the same amp or modified.
Also can anyone tell me which way the switch on top should be facing and what mode that is? I currently use it set towards the back of the amp.
Thanks
I have a Music Angel Class A Integrated Amplifier EL34 x4 XD500MKIII.
I wonder if anybody as a working circuit diagram most of the one's on here are of other versions of the same amp or modified.
Also can anyone tell me which way the switch on top should be facing and what mode that is? I currently use it set towards the back of the amp.
Thanks
http://www.china-hifi-audio.com/en/...integrated-amplifier-el34-x4-xd500mkiii-p-141
I would think that switch to back would be UL pentode mode. I would suggest not to mess with it unless you know what you are doing.
Its a good idea to read the safety message here:
http://www.diyaudio.com/forums/tubes-valves/30172-safety-practices-general-ultra-high-voltage.html
I would think that switch to back would be UL pentode mode. I would suggest not to mess with it unless you know what you are doing.
Its a good idea to read the safety message here:
http://www.diyaudio.com/forums/tubes-valves/30172-safety-practices-general-ultra-high-voltage.html
hi
Thanks for the help.
Yes I am very respectful of high voltages having got a kick from a CRT in the 1970s.
I presume the diagram is for 1 channel of the amp?
I do not want to touch anything inside but need to ask a few more questions.
First I will tell where I got the amp, it is a reputable dealer in used valve equipment in the UK, so is all checked for working ok.
The problem I have is the 2 valves in the front have been changed for 6n9p where originally 6sl7 the gain seems very high, I am just able to turn the volume to 9oclock is this caused by the two 6n9p valves being high gain? and if I changed them back to 6sl7 would I have to have the new valves biased?
Thanks for the help.
Yes I am very respectful of high voltages having got a kick from a CRT in the 1970s.
I presume the diagram is for 1 channel of the amp?
I do not want to touch anything inside but need to ask a few more questions.
First I will tell where I got the amp, it is a reputable dealer in used valve equipment in the UK, so is all checked for working ok.
The problem I have is the 2 valves in the front have been changed for 6n9p where originally 6sl7 the gain seems very high, I am just able to turn the volume to 9oclock is this caused by the two 6n9p valves being high gain? and if I changed them back to 6sl7 would I have to have the new valves biased?
The XD500 I once owned had 6SN7 or 6N8S in the front amp stages. These have much lower gain than 6SL7/6N9S (20 vs 70).
6n9p is basically a Chinese version of a 6sl7. however I see neither in the schematic.... however it does has 6n8p - a Chinese version of 6sn7.
Are you sure we are looking at the same amp?
Ian
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Hi
I not sure about the diagram.
this one comes from the china-audio website where the amp is advertised?
the amp sounds best with the switch to the back so I guess that is triode mode?
I have a photo of the inside of the amp I got online and it shows 6 voltage trimmers on the circuit board. I presume they are for biasing that's why I asked if I change the front 2 valves would I need to have them biased?
I not sure about the diagram.
this one comes from the china-audio website where the amp is advertised?
the amp sounds best with the switch to the back so I guess that is triode mode?
I have a photo of the inside of the amp I got online and it shows 6 voltage trimmers on the circuit board. I presume they are for biasing that's why I asked if I change the front 2 valves would I need to have them biased?
Attachments
No, you would not need to adjust anything to change any of the tubes except the EL34. The others are biased automatically.
The 6 trimmers are : one each for the 4 EL34's, and two trimmers (one for each channel) for hum balance on the heater 6.3v.
6sn7
Like many valves there are supremely good ones
ant there are highly micro-phonic junk.
Best NOS. are as usual expensive. Chinese are Chinese quality!
I believe there are good Russian military equivalents but can not quote numbers.
You can't just swap valves/tubes like that. Circuit changes are usually necessary.
First, compare the resistor values on your board to those in your circuit diagram.
There are so many 'versions' of china amps... Its just not wise to go forward with swapping valves without knowing what you are doing.
Ian
hi
Yes I have heard that some of the cheaper 6sn7 can be bad.
I have ordered a matched pair of JJ-6sn7 these are modern valves that should not suffer with micro phonics, they are not expensive. I have a pair of JJ-5751 in my phono amp they have a warmer sound than the Sovteks which I need because my speakers are very detailed Tannoy XT6.
Yes I have heard that some of the cheaper 6sn7 can be bad.
I have ordered a matched pair of JJ-6sn7 these are modern valves that should not suffer with micro phonics, they are not expensive. I have a pair of JJ-5751 in my phono amp they have a warmer sound than the Sovteks which I need because my speakers are very detailed Tannoy XT6.
Hi Ian
I can't remember where I downloaded them from? I just did a general search for schematics for a Music Angel XD-SE and downloaded all the ones that looked likely.
I know you said not to swap valves but I had to give it a try as I have not the funds to pay a technician to replace valves for me.
I was not getting the full benefit of the amp with the volume so low.
I put a matched pair of JJ- 6sn7 in the plate current is 58.5 and it says the TC 1.7 presume that is the triode current.
I have run them for about 2 hours so far kept checking to see if anything was getting hot that is not suppose to get hot.
Now I can turn the gain to 11oclock and the sound as opened up a lot.
Barry
I can't remember where I downloaded them from? I just did a general search for schematics for a Music Angel XD-SE and downloaded all the ones that looked likely.
I know you said not to swap valves but I had to give it a try as I have not the funds to pay a technician to replace valves for me.
I was not getting the full benefit of the amp with the volume so low.
I put a matched pair of JJ- 6sn7 in the plate current is 58.5 and it says the TC 1.7 presume that is the triode current.
I have run them for about 2 hours so far kept checking to see if anything was getting hot that is not suppose to get hot.
Now I can turn the gain to 11oclock and the sound as opened up a lot.
Barry
Hi Barry
I expect that the cathode resistor is probably 39k Ohm if that schematic you found is anywhere near the truth. It is worth looking closely at the resistors on the circuit board and figuring out their values - with the color codes.
The 6sn7 is not a 6sl7. They are in fact quite different. You're lucky that "swapping" them out did not cause any immediate damage.
If you want to keep the 75k ohm anode resistors (check to see if they really are this value), then for 6sn7 you could consider changing the tail resistor to 22k ohm. Make sure the resistor is 2 watt non-inductive. Mills or Caddock is a good choice for this resistor, but carbon film will probably also be ok. You of course need to do this on both channels.
Personally I like to run the 6sn7 at higher current, and with a CCS (constant current source) in the tail for this kind of duty. But this will require a few more changes than you will probably feel comfortable with right now.
Also - the 300k B+ dropping resistor in that schematic can't be right either, so I simply don't trust that schematic at all. Again - you're lucky...
Ian
I expect that the cathode resistor is probably 39k Ohm if that schematic you found is anywhere near the truth. It is worth looking closely at the resistors on the circuit board and figuring out their values - with the color codes.
The 6sn7 is not a 6sl7. They are in fact quite different. You're lucky that "swapping" them out did not cause any immediate damage.
If you want to keep the 75k ohm anode resistors (check to see if they really are this value), then for 6sn7 you could consider changing the tail resistor to 22k ohm. Make sure the resistor is 2 watt non-inductive. Mills or Caddock is a good choice for this resistor, but carbon film will probably also be ok. You of course need to do this on both channels.
Personally I like to run the 6sn7 at higher current, and with a CCS (constant current source) in the tail for this kind of duty. But this will require a few more changes than you will probably feel comfortable with right now.
Also - the 300k B+ dropping resistor in that schematic can't be right either, so I simply don't trust that schematic at all. Again - you're lucky...
Ian
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Hi
Sorry its been so long here is an update on my Music Angel DX-SE 500 mk111 amp.
The el34 valves where the original Music Angel brand ones I presume from when it was made. So I change them for some Russian Electra Harmonix they have a plate current of 32. When I came to bias them I found that I had to set them quit low 27ma because there seem to be a lot of variation IE they went up to 34 after 2 days in the end I decided to change the trim pots because they seemed quite loose I ordered another set and now they seem to be holder there setting 30ma. I will try to send some photo of the inside of my amp the ones I put on here originaly where from web sites.
Barry
Sorry its been so long here is an update on my Music Angel DX-SE 500 mk111 amp.
The el34 valves where the original Music Angel brand ones I presume from when it was made. So I change them for some Russian Electra Harmonix they have a plate current of 32. When I came to bias them I found that I had to set them quit low 27ma because there seem to be a lot of variation IE they went up to 34 after 2 days in the end I decided to change the trim pots because they seemed quite loose I ordered another set and now they seem to be holder there setting 30ma. I will try to send some photo of the inside of my amp the ones I put on here originaly where from web sites.
Barry
Hi
I decided because my amp is quite old now to do some test on it the first being the heater voltage, I looked at the speck sheet for my el34s and it said heater voltage between 6v and 6.7v when I checked it was 4.3vac this was on all el34 pins 2-7 with no valves in place is this the right way to test it?
Barry
I decided because my amp is quite old now to do some test on it the first being the heater voltage, I looked at the speck sheet for my el34s and it said heater voltage between 6v and 6.7v when I checked it was 4.3vac this was on all el34 pins 2-7 with no valves in place is this the right way to test it?
Barry
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