Sorry for my not to gread englisch but I will try my best to explain my problem.
I heve bought a music angle XD-SE tube ampliefier with EL34 end tubes. So far so good, it sound's good, but ik could sound bether. Ik have fount the scematic of this amp in an other thread on this forum http://www.diyaudio.com/forums/showthread.php?threadid=59070.
This scematic is nog very eary to read becouse of the poor quality so i opened my amp and drown the scematic form the ciruit boards. This is what i got:
Hier staat de grote verzie
It is not looking verry bad but is could be bether, and there are some strange resistor valuse:
There will probebly be more strange things in the circuit, but this are the things that i can find with my limmeted tube knowledge.
I think i would be best to remove R19, R16, R1. And replace R24, R25 with 100Ohm resitors. And replace the 22 Ohm resitors for 12Ohm ones.
Ill change the 0,33uF capasator's that are in the signal way for JJ capasators and change the potentiometer for an Alps one.
Do you think that this is a good idea for improving the sound? And are there other things that i can remove ore change to improve the sound?
I heve bought a music angle XD-SE tube ampliefier with EL34 end tubes. So far so good, it sound's good, but ik could sound bether. Ik have fount the scematic of this amp in an other thread on this forum http://www.diyaudio.com/forums/showthread.php?threadid=59070.
This scematic is nog very eary to read becouse of the poor quality so i opened my amp and drown the scematic form the ciruit boards. This is what i got:
Hier staat de grote verzie
It is not looking verry bad but is could be bether, and there are some strange resistor valuse:
- R24/R25 3K --> In the most el34 push pull amps they are not 3K but 100Ohm
- The 2 x 22 Ohm resistor between El34 pin 8, Normal 12 Ohm
- R19 - R20 / R16 - R17 --> Together 78K, Normal 1K and some times compleetly removed
- An other strange thing is the feedback from 6N1 throug the R3/R4 resistor devision withr the 10K sery rezistor
- And the circuit of R10 and R11 I don't understand
There will probebly be more strange things in the circuit, but this are the things that i can find with my limmeted tube knowledge.
I think i would be best to remove R19, R16, R1. And replace R24, R25 with 100Ohm resitors. And replace the 22 Ohm resitors for 12Ohm ones.
Ill change the 0,33uF capasator's that are in the signal way for JJ capasators and change the potentiometer for an Alps one.
Do you think that this is a good idea for improving the sound? And are there other things that i can remove ore change to improve the sound?
Glad to hear that your amplifier sonds good 
There are actually quite a few owners that seem quite pleased with the sound of the the M.A. amplifiers.
As you have observed there are however a few unusual component choices, such as the unusually large grid-stoppers. This could be because the builders do not know what they are doing, or it could be that they have reached their choices based on listening tests.
- R24/R25 3K --> In the most el34 push pull amps they are not 3K but 100 Ohm
Yes, large value screen stopper resistors.
- The 2 x 22 Ohm resistor between El34 pin 8, Normal 12 Ohm
Two 22 ohm in parallel makes 11 ohm. Not so bad. Actually the cathode resistors could be 1 ohm or 10 ohm without making much difference. Their main purpose is to create a small voltage drop to measure the current.
- R19 - R20 / R16 - R17 --> Together 78K, Normal 1K and some times compleetly removed
Yes. unusually large grid stopper, and actually a voltage divider network
The resistors do however seem to be of the "ear-friendly" carbon composite type.
- An other strange thing is the feedback from 6N1 throug the R3/R4 resistor devision withr the 10K sery rezistor
The feedback ratio looks very low. May be OK for triode operation, but questionable for pentode mode.
And the circuit of R10 and R11 I don't understand
Probably just a voltage drop of the B+ for the driver stage. Not sure your circuit is exact here.
This guy Lukasz Fikus, seem to share your idea that a lot of components could be removed in some of these amps
http://www.lampizator.eu/AMPLIFIERS/AMPS.html
Myself I am not yet sure, but I was qurious enough to buy the bigger bottle KT88 version a few weeks ago to do some measurements and experimentation. So far I have only listened to some music. It sounds quite pleasant, and responds well to some premium NOS tubes.
SveinB.
Edit: a direct link to Kippy's traced diagram: http://home.xmsnet.nl/bjaspers/100_0623_600.jpg
There are actually quite a few owners that seem quite pleased with the sound of the the M.A. amplifiers.
As you have observed there are however a few unusual component choices, such as the unusually large grid-stoppers. This could be because the builders do not know what they are doing, or it could be that they have reached their choices based on listening tests.
- R24/R25 3K --> In the most el34 push pull amps they are not 3K but 100 Ohm
Yes, large value screen stopper resistors.
- The 2 x 22 Ohm resistor between El34 pin 8, Normal 12 Ohm
Two 22 ohm in parallel makes 11 ohm. Not so bad. Actually the cathode resistors could be 1 ohm or 10 ohm without making much difference. Their main purpose is to create a small voltage drop to measure the current.
- R19 - R20 / R16 - R17 --> Together 78K, Normal 1K and some times compleetly removed
Yes. unusually large grid stopper, and actually a voltage divider network
The resistors do however seem to be of the "ear-friendly" carbon composite type.
- An other strange thing is the feedback from 6N1 throug the R3/R4 resistor devision withr the 10K sery rezistor
The feedback ratio looks very low. May be OK for triode operation, but questionable for pentode mode.
And the circuit of R10 and R11 I don't understand
Probably just a voltage drop of the B+ for the driver stage. Not sure your circuit is exact here.
This guy Lukasz Fikus, seem to share your idea that a lot of components could be removed in some of these amps
http://www.lampizator.eu/AMPLIFIERS/AMPS.html
Myself I am not yet sure, but I was qurious enough to buy the bigger bottle KT88 version a few weeks ago to do some measurements and experimentation. So far I have only listened to some music. It sounds quite pleasant, and responds well to some premium NOS tubes.
SveinB.
Edit: a direct link to Kippy's traced diagram: http://home.xmsnet.nl/bjaspers/100_0623_600.jpg
Something went wrong with the images of the scematic, and i can't edit my post so, here are the good ones.
big version
An externally hosted image should be here but it was not working when we last tested it.
big version
@Svein_B
Thanks for the respons.
The link http://www.lampizator.eu/AMPLIFIERS/AMPS.html explains exacly why i want to remove all the unnessesery components. That is also the reason for this topic.
But is it is dificult to determen what components are wrong or can be conpleetly removed. That is why i need your help and the help of the other forum members to give me a push in the right derection.
Things that i'm going to do first are:
- Replacing R4/R25 with 1K resisors for bether sound in triode mode
- Removing R19 and R16
- Replacing R17 and R20 with 1K resistors
- Removing R1 and R2
- Replacing the potentiometer with a 100K potentiometer from ALPS
- Replacing the 0,33uF capacitors in the signal paths
But if i look at the lampizator site there are more things i can remove for a bether sound. So what are the other options?
Thanks for the respons.
The link http://www.lampizator.eu/AMPLIFIERS/AMPS.html explains exacly why i want to remove all the unnessesery components. That is also the reason for this topic.
But is it is dificult to determen what components are wrong or can be conpleetly removed. That is why i need your help and the help of the other forum members to give me a push in the right derection.
Things that i'm going to do first are:
- Replacing R4/R25 with 1K resisors for bether sound in triode mode
- Removing R19 and R16
- Replacing R17 and R20 with 1K resistors
- Removing R1 and R2
- Replacing the potentiometer with a 100K potentiometer from ALPS
- Replacing the 0,33uF capacitors in the signal paths
But if i look at the lampizator site there are more things i can remove for a bether sound. So what are the other options?
I have drawn the scematic again, but now with the good symbols. So now it will be a little easer to understand.
http://home.xmsnet.nl/bjaspers/100_0631_V2.JPG
An externally hosted image should be here but it was not working when we last tested it.
http://home.xmsnet.nl/bjaspers/100_0631_V2.JPG
Hello,
This is my first post so I hope the picture below comes through.
I also have a music angel el34 push pull amp, specifically the XD 500 Mark III. From your schematics, as well as other on the web, I can tell that every version from music angel is different. My version does not have ANY grid stop resisters, which i found very suprising. I have posted a PDF of the diagram I put together over the afternoon. I will also try to post the power supply stages shortly.
This is my first post so I hope the picture below comes through.
I also have a music angel el34 push pull amp, specifically the XD 500 Mark III. From your schematics, as well as other on the web, I can tell that every version from music angel is different. My version does not have ANY grid stop resisters, which i found very suprising. I have posted a PDF of the diagram I put together over the afternoon. I will also try to post the power supply stages shortly.
The schematic below is the power stages of my amp.
I am planning on reworking this amp from the power stages back. The first thing that will need replacing is the electrolytic. Music Angel (MA) seems to be using second hand components. My PS caps have physical damages(tears in the insulation) and visable rust even though the rest of the amp is clean.
I have parts on order and will recap the PS with Panasonic TS-ED, change out all diodes to FREDs, and convert to DC filament supply. In a few cases they have the heater wires parallel with the the grid bias and negative feedback wires. I assume this is the source of most of the hum.
The parts will arrive in a week or two and I will let you know how the PS upgrades go. (i am upgrading one channel at a time.)
Erik
I am planning on reworking this amp from the power stages back. The first thing that will need replacing is the electrolytic. Music Angel (MA) seems to be using second hand components. My PS caps have physical damages(tears in the insulation) and visable rust even though the rest of the amp is clean.
I have parts on order and will recap the PS with Panasonic TS-ED, change out all diodes to FREDs, and convert to DC filament supply. In a few cases they have the heater wires parallel with the the grid bias and negative feedback wires. I assume this is the source of most of the hum.
The parts will arrive in a week or two and I will let you know how the PS upgrades go. (i am upgrading one channel at a time.)
Erik
Thanks everyone for sharing the schematic and information. My EL34 is the same as Kippy's. After a bias adjustment, I set the bias to be about 40ma. The resistor is 22 ohm(one for each El34 tube) so the reading is about 0.88V across it. I guess I have one weak tube as the voltage was 0.67v before but the bias adjustment took care of it. The amp sounds pretty good.
I noticed that the version posted by Erick is very different. Some resistors values are in hundred ohms instead of thousands ohms.
I noticed that the ground pin on the power receptacle is not wired. Should I wire it to the chassis? Can I get better performance if I remove the 6E2 magic eye tubes? I am new to this so any suggestions would be appreciated.
I noticed that the version posted by Erick is very different. Some resistors values are in hundred ohms instead of thousands ohms.
I noticed that the ground pin on the power receptacle is not wired. Should I wire it to the chassis? Can I get better performance if I remove the 6E2 magic eye tubes? I am new to this so any suggestions would be appreciated.
Re; Music Angel XD500 Mk III
I'm not familiar with the XD500mkIII, and, indeed it's been several years since
I serviced/repaired a Music Angel Amplifier, but, having said that, if by 'pulsing',
you mean oscillating, surely no valve in an amplifier should oscillate.
This could indicate poor grounding, faulty capacitors, or other problems.
Having just downloaded the circuit diagrams of the XD500mkIII, I'm a little
puzzled to see that 28mV @ 105kHz is present at the speaker terminals-almost 6 times the level at 121hz. Seems wrong to me!
I'm not familiar with the XD500mkIII, and, indeed it's been several years since
I serviced/repaired a Music Angel Amplifier, but, having said that, if by 'pulsing',
you mean oscillating, surely no valve in an amplifier should oscillate.
This could indicate poor grounding, faulty capacitors, or other problems.
Having just downloaded the circuit diagrams of the XD500mkIII, I'm a little
puzzled to see that 28mV @ 105kHz is present at the speaker terminals-almost 6 times the level at 121hz. Seems wrong to me!
As far as I know, removing the Magic Eye Tubes will not make any difference to the amplifier's performance, but I would definitely connect the Earth Pin of the power receptacle to the chassis metalwork. A short lead to a tag fitted under the nearest fixing screw should be adequate. Obviously a 3-wire mains lead should then be used. In the U.K. at least, a double pole mains switch would be considered better than the single pole one usually fitted by the makers.
So, you suggest it's a bad idea to buy it?
I've asked to guy for a film of the amplifier when up and running.
What is the problem when looking at the circuit diagrams? Is it a bad amplifier?
YouTube - M2U00065
That's the amplifier up and running.
What do you think?
I didn't see any difference between the two, to be honest. Do you?
Edit: A friend of mine said it looked like a "Magic Eye". After googling a little it seems like it's just cosmetic, built into the tubes. If i can't stand with it i just guess i have to change tubes. But if one pulsates slower than the other, is it the "Magic Eye's" fault or something else? :O
Edit 2: One think i came to think of. Maybe it depends on the music being played. If there's more stuff going on in the left channel it obviously needs a little more power. And then the left "eye" blinks more than the right one, and vice versa.
Or is it a faulty tube or even the amp? Maybe it could be the amp sending the signal slower/weaker to one of the channels?
That's the amplifier up and running.
What do you think?
I didn't see any difference between the two, to be honest. Do you?
Edit: A friend of mine said it looked like a "Magic Eye". After googling a little it seems like it's just cosmetic, built into the tubes. If i can't stand with it i just guess i have to change tubes. But if one pulsates slower than the other, is it the "Magic Eye's" fault or something else? :O
Edit 2: One think i came to think of. Maybe it depends on the music being played. If there's more stuff going on in the left channel it obviously needs a little more power. And then the left "eye" blinks more than the right one, and vice versa.
Or is it a faulty tube or even the amp? Maybe it could be the amp sending the signal slower/weaker to one of the channels?
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The amp is a reasonably good one.
The price of around $700 may however seem a bit high, especially if some tubes are close to burning out.
You can buy a new MA with KT88 for $600 including shipping (but excl. your country's VAT). The general opinion is that this is a better amp, especially if you roll some of the small signal tubes.
Svein
Well, it's my 1 year old Harman Kardon HK3490 + 1000kr (which is around 145$). It seems like he will drive to my place with the amp so i can quality check it. I think we will split the fuel costs which would be around 400-450kr for me. If i sell my HK3490 today i could get maybe 3500. The price has dropped quite much recently, and with my student discount i can buy one for 3450 at a large scandinavian seller. Maybe i could only get around 3000 for it since the price has dropped so incredibly much since i bought it.
So, if we say my amp is 3000 and then i pay 1000 and 450 for fuel. That's around 650$
If i buy somthing from outside of EU i have to pay the 25% swedish Moms. And then there's the toll fee and such... Would end up at around 1000$ or so probably.
I stand corrected, Rullknufs. Didn't realise that you were speaking of the Magic Eye (or
'Cat's Eyes' as the schematic calls them) As far as I can tell from the You Tube video, they are behaving as I would expect such indicators to perform-i.e. responding to the
variations in sound level in the music, which is of course in stereo. If a sine or square wave signal of the same amplitude was fed into each channel, then the indicated level,
subject to the usual component tolerances, would be the same for both channels, and
the display from the 'eyes' would be steady.
As Svein_B says though, the price still seems a bit high, if a new KT88 equipped MA can be had for $600 +VAT(in the U.K. that would make it $720, or approx.
4930 Swedish Kroner- with 25% tax in Sweden, though, the total price would be $750.
At any rate you'll have to be the judge of which is the better buy
'Cat's Eyes' as the schematic calls them) As far as I can tell from the You Tube video, they are behaving as I would expect such indicators to perform-i.e. responding to the
variations in sound level in the music, which is of course in stereo. If a sine or square wave signal of the same amplitude was fed into each channel, then the indicated level,
subject to the usual component tolerances, would be the same for both channels, and
the display from the 'eyes' would be steady.
As Svein_B says though, the price still seems a bit high, if a new KT88 equipped MA can be had for $600 +VAT(in the U.K. that would make it $720, or approx.
4930 Swedish Kroner- with 25% tax in Sweden, though, the total price would be $750.
At any rate you'll have to be the judge of which is the better buy
Music Angel KT88 Amplifier
I don't have a link to the M.A. XD-SE (KT88) amplifier. The circuit is essentially similar to the EL84 version. They are probably available from China or Hong Kong on E Bay. As noted in my earlier reply
I was simply quoting from Svein_B's post. I do have some printed information
somewhere about the amplifier, most, if not all of which, came from other posts
on this forum 3 or 4 years ago. From memory, a similar circuit to the EL84
version(based on the classic Williamson design) is used, with either triode or Ultra Linear o/p stage configuration selectable via a front panel switch.
I don't have a link to the M.A. XD-SE (KT88) amplifier. The circuit is essentially similar to the EL84 version. They are probably available from China or Hong Kong on E Bay. As noted in my earlier reply
I was simply quoting from Svein_B's post. I do have some printed information
somewhere about the amplifier, most, if not all of which, came from other posts
on this forum 3 or 4 years ago. From memory, a similar circuit to the EL84
version(based on the classic Williamson design) is used, with either triode or Ultra Linear o/p stage configuration selectable via a front panel switch.
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