please tell me how to up grade music angle kt88 amplifier ?
i bought a chinese made music angle kt88 tube amplifier from ebay store at $ 430 usa dollars , it is a 2 power supplys and 2 mono block which combined in a box, good sound , full of power 65w,
please tell me how to up grade it and replace the kt88.
thank you.
i bought a chinese made music angle kt88 tube amplifier from ebay store at $ 430 usa dollars , it is a 2 power supplys and 2 mono block which combined in a box, good sound , full of power 65w,
please tell me how to up grade it and replace the kt88.
thank you.
Without seeing the circuit I can ONLY ASSUME its similar to the EL34 Music Angel. See this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=59070
I found that the phase splitter was the limiting part of the circuit due to poor choice of phase splitter design AND a production fault.
I also had good results from tube rolling - ditch the chinese 6N8P and substitute a 6SN7 (I used modern production Electroharmonix Gold). Input tube on the EL34 version was a 6N1P - I substituted a "Winged C" Svetlana. I also found that JJ EL34s were far superior to the standard chinese EL34s. I haven't tried the JJ KT88s but have heard from someone who has that they are very good.
I redesigned/rebuilt the phase splitter by replacing the anode load resistors with equal value resistors and substituted a LED referenced cascode current source in place of the tail resistor and while I was at it I doubled the current in the tube. ALL of the Music Angel circuits I've seen (and I have the EL34 PP and the 845 SET models) run the 6N8Ps at very low currents.
Can you post a schematic - probably available at the "eaudioguy" website.
Cheers,
Ian
http://www.diyaudio.com/forums/showthread.php?s=&threadid=59070
I found that the phase splitter was the limiting part of the circuit due to poor choice of phase splitter design AND a production fault.
I also had good results from tube rolling - ditch the chinese 6N8P and substitute a 6SN7 (I used modern production Electroharmonix Gold). Input tube on the EL34 version was a 6N1P - I substituted a "Winged C" Svetlana. I also found that JJ EL34s were far superior to the standard chinese EL34s. I haven't tried the JJ KT88s but have heard from someone who has that they are very good.
I redesigned/rebuilt the phase splitter by replacing the anode load resistors with equal value resistors and substituted a LED referenced cascode current source in place of the tail resistor and while I was at it I doubled the current in the tube. ALL of the Music Angel circuits I've seen (and I have the EL34 PP and the 845 SET models) run the 6N8Ps at very low currents.
Can you post a schematic - probably available at the "eaudioguy" website.
Cheers,
Ian
Thanks Skorpion,
Hififactory,
The circuit is not the same as the Music Angel EL34 so some of my comments above are not relevant.
Actually its a YAW.n "Yet Another Williamson". There is more information on upgrading the Williamson design around the net than you can probably get through in a year.
Make sure you are running in Triode Mode for a start. On the switch which selects Triode / Tetrode Mode the position which is quieter (but more refined) is the Triode position. You CAN switch between the two with the amp running BUT its perhaps not a good idea to do it at full power.
On the schematic bottom right hand side you will see a 100K potentiometer and "-> A" this is the output tube bias adjustment.
Just one adjustment for both tubes so it important to use matched pairs. You would want to do both channels so its best to buy a matched quad. Each KT88 has a 12 Ohm resistor in the cathode.
Exactly 1 volt across a 12 Ohm resistor means 83 mA bias current and I am guessing that that is the correct bias setting.
Check first - measure the high voltage at the KT88 anode. For 35 Watts dissipation divide 35 by the high voltage reading to give the bias current to set. Multiply that current by 12 to get the voltage reading across the 12 Ohms cathode resistor and then adjust the bias potentiometer to give that reading. For long tube life you may want to set for 32 or 33 Watts rather than 35.
The value of the KT88 grid 1 resistor is 221K Ohms and this means that you should NOT run more than 35W anode dissipation even though the KT88 is capable (with smaller grid 1 resistance) of a maximum of 42 Watts.
Cheers,
Ian
Hififactory,
The circuit is not the same as the Music Angel EL34 so some of my comments above are not relevant.
Actually its a YAW.n "Yet Another Williamson". There is more information on upgrading the Williamson design around the net than you can probably get through in a year.
Make sure you are running in Triode Mode for a start. On the switch which selects Triode / Tetrode Mode the position which is quieter (but more refined) is the Triode position. You CAN switch between the two with the amp running BUT its perhaps not a good idea to do it at full power.
On the schematic bottom right hand side you will see a 100K potentiometer and "-> A" this is the output tube bias adjustment.
Just one adjustment for both tubes so it important to use matched pairs. You would want to do both channels so its best to buy a matched quad. Each KT88 has a 12 Ohm resistor in the cathode.
Exactly 1 volt across a 12 Ohm resistor means 83 mA bias current and I am guessing that that is the correct bias setting.
Check first - measure the high voltage at the KT88 anode. For 35 Watts dissipation divide 35 by the high voltage reading to give the bias current to set. Multiply that current by 12 to get the voltage reading across the 12 Ohms cathode resistor and then adjust the bias potentiometer to give that reading. For long tube life you may want to set for 32 or 33 Watts rather than 35.
The value of the KT88 grid 1 resistor is 221K Ohms and this means that you should NOT run more than 35W anode dissipation even though the KT88 is capable (with smaller grid 1 resistance) of a maximum of 42 Watts.
Cheers,
Ian
hi, thank you
i moded my el34 music angle amplifier 2 days ago. i cut off the 6e2 tube , then, the sound is so wonderful now, it is unbelieveable ......... please try it ....... but be careful ...... make sure ..... step by step .....
now , i want to buy a music angle 845 amplifier, single end design, i found out one in ebay too = ebay store name :
hotproductstore, there are some 845 amps over there .....
with nice photos
thank you
good day
i moded my el34 music angle amplifier 2 days ago. i cut off the 6e2 tube , then, the sound is so wonderful now, it is unbelieveable ......... please try it ....... but be careful ...... make sure ..... step by step .....
now , i want to buy a music angle 845 amplifier, single end design, i found out one in ebay too = ebay store name :
hotproductstore, there are some 845 amps over there .....
with nice photos
thank you
good day
gingertube said:
Hi there...yes JJ88's (in blue/yellow boxes) can deliver the power........however when compared to other "good newish brands" they hold up power well......but at a slightly higher thd compared to GLion types esp in UL mode.
The only thing against..... is the shape of the glass envelope (I don't like it) ....but so are other things in life.
richj
I just boght one of those: http://cgi.ebay.com/Upgradeable-Val...oryZ3280QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Has anyone has schematics or some upgrading tips? Form first sight, schematics must be similar to Music Angel el34
Has anyone has schematics or some upgrading tips? Form first sight, schematics must be similar to Music Angel el34
i got a music angle el34 amplifier from here :
http://cgi.ebay.com/NEW-EL34-PUSH-P...itemZ5827082238QQcategoryZ73369QQcmdZViewItem
they have the solen version too.
you may ask the seller give the infos of music angle el34 amp to you .........
good day
http://cgi.ebay.com/NEW-EL34-PUSH-P...itemZ5827082238QQcategoryZ73369QQcmdZViewItem
they have the solen version too.
you may ask the seller give the infos of music angle el34 amp to you .........
good day
Hi Skorpion,
I haven't heard a KT88 Music Angel just the EL34 and the 845SET (I have both).
There WAS a guy in Oz who was importing these amps and on-selling and he and some audio nutter mates did a listening test to the full range of Music Angels and his view was that the EL34 sounded the best (apart from the 845SET).
I'm not all that impressed with my EL34 version, its OK BUT nothing really special - in Triode Mode (which is the way I always run it) it lacks a bit of gain and I can't drive it to full output with my Preamp. There is a thread here on what I've done to the EL34 so far.
CAVEAT: The reference amp I'm using as a "yard stick" is a parallel push pull EL34 Triode Mode using Plitron PAT4006 Toroidal Output Transformers with no global feedback - Its output transformers alone cost about the same as the entire Music Angel Amp so take the comments above with a "grain of salt".
Despite my "YAW..n" comment in the post above I think the KT88 version would be a better bet for a cheap decent sounding amp with lots of scope for upgrading.
If you've got enough cash the 845SET is the best option BUT its about twice the price.
In ALL of these Music Angel Amps the 6N8P driver stages are the weak link. They are not very good tubes and in all cases they are run at way too low a current. In every case substituting 6SN7 for the 6N8P (even without increasing the current) made an immediate and quite noticable improvement - less "covered", more dynamic and better detail. I used modern production Electroharmonix 6SN7 Golds.
Hope this is of some help to you,
Cheers,
Ian
I haven't heard a KT88 Music Angel just the EL34 and the 845SET (I have both).
There WAS a guy in Oz who was importing these amps and on-selling and he and some audio nutter mates did a listening test to the full range of Music Angels and his view was that the EL34 sounded the best (apart from the 845SET).
I'm not all that impressed with my EL34 version, its OK BUT nothing really special - in Triode Mode (which is the way I always run it) it lacks a bit of gain and I can't drive it to full output with my Preamp. There is a thread here on what I've done to the EL34 so far.
CAVEAT: The reference amp I'm using as a "yard stick" is a parallel push pull EL34 Triode Mode using Plitron PAT4006 Toroidal Output Transformers with no global feedback - Its output transformers alone cost about the same as the entire Music Angel Amp so take the comments above with a "grain of salt".
Despite my "YAW..n" comment in the post above I think the KT88 version would be a better bet for a cheap decent sounding amp with lots of scope for upgrading.
If you've got enough cash the 845SET is the best option BUT its about twice the price.
In ALL of these Music Angel Amps the 6N8P driver stages are the weak link. They are not very good tubes and in all cases they are run at way too low a current. In every case substituting 6SN7 for the 6N8P (even without increasing the current) made an immediate and quite noticable improvement - less "covered", more dynamic and better detail. I used modern production Electroharmonix 6SN7 Golds.
Hope this is of some help to you,
Cheers,
Ian
Thanks a lot Ian !
Really helpful comments.
I found the following interesting link: http://www.vt4c.com/shop/program/main.php
/Erling
Really helpful comments.
I found the following interesting link: http://www.vt4c.com/shop/program/main.php
/Erling
Josh,
My reference amp is lovely BUT nothing special schematic wise.
Go to
http://www.plitron.com/
and click on audio output transformers and then Circuit Board for 70 and 100W amps.
I built the PAT4006 (VDV2100) 100W version and then made the following mods:
Triode Strapped the EL34 output tubes, biased at 45mA each (46Watts out instead of 100W) - JJ Electronics were the best of the modern production EL34s
Changed the 12AU7 to ECC99 - big improvement
Changed the Common Cathode Stage, Cathode bypass capacitor to a Blackgate.
Reduced R21 to 2K2 to get a bit more bias voltage and substituted Sovtek 6550 (just what I had on the shelf) biased at 75mA each in place of the EL34s.
- this takes output power back to about 65 Watts
- reduces output impedance
- gives lots of Class A power before transitioning into Class B which helps the cathodyne splitter by maintaining equal loads on anode and cathode to much higher power.
Watch the mechanical layout - I made a mistake of having the output tubes too close to the output transformer. Its fine with skinny EL34s BUT I couldn't fit KT88s at all and the 6550 are a bit close and the output tranny gets very warm, er.. hot in fact.
Also when you build the PCB think about how it will be mounted. I put the output tube cathode resistors (bias measuring points) and the bias adjust pots on the back of the PCB so that I could adjust bias with the amp upside down or on its end on the bench by simply removing the bottom cover.
While these monoblocks are lovely there is still room for improvement BUT this will require a major step up in complexity of the front end/driver.
I've started on a MUCH more complicated monoblocks using the VDV2100-CFB/H output tranny with JJ KT88 and much more complex front end BUT these are only at the metal bashing stage.
Cheers,
Ian
My reference amp is lovely BUT nothing special schematic wise.
Go to
http://www.plitron.com/
and click on audio output transformers and then Circuit Board for 70 and 100W amps.
I built the PAT4006 (VDV2100) 100W version and then made the following mods:
Triode Strapped the EL34 output tubes, biased at 45mA each (46Watts out instead of 100W) - JJ Electronics were the best of the modern production EL34s
Changed the 12AU7 to ECC99 - big improvement
Changed the Common Cathode Stage, Cathode bypass capacitor to a Blackgate.
Reduced R21 to 2K2 to get a bit more bias voltage and substituted Sovtek 6550 (just what I had on the shelf) biased at 75mA each in place of the EL34s.
- this takes output power back to about 65 Watts
- reduces output impedance
- gives lots of Class A power before transitioning into Class B which helps the cathodyne splitter by maintaining equal loads on anode and cathode to much higher power.
Watch the mechanical layout - I made a mistake of having the output tubes too close to the output transformer. Its fine with skinny EL34s BUT I couldn't fit KT88s at all and the 6550 are a bit close and the output tranny gets very warm, er.. hot in fact.
Also when you build the PCB think about how it will be mounted. I put the output tube cathode resistors (bias measuring points) and the bias adjust pots on the back of the PCB so that I could adjust bias with the amp upside down or on its end on the bench by simply removing the bottom cover.
While these monoblocks are lovely there is still room for improvement BUT this will require a major step up in complexity of the front end/driver.
I've started on a MUCH more complicated monoblocks using the VDV2100-CFB/H output tranny with JJ KT88 and much more complex front end BUT these are only at the metal bashing stage.
Cheers,
Ian
gingertube said:
First of all, I would like to say how much I appreciate all the knowledge collected in this forum, this being my first post and all. Kudos to all those who contribute!
Gingertube,
you mention that substituting the 6SN8-tube with a 6SN7-tube will augment the sound-quality..
At this point I am a little confused; in the specification for the amp and printed on the amp itself "6SL7" and "6SN7" are mentioned, but I kind of get the idea that the amp is delivered with 6N9P and 6N8P-tubes. Is this correct?
Could both these tube-types (6N9P and 6N8P) be substituted with 6SN7-tubes?
Also, would you recommend substituting the 845-tubes?
Answers are highly appreciated
Regards,
eivindjk
eivindjk,
Yes the Music Angel amplifiers I have seen are all delivered with 6N8P and 6N9P rather than 6SN7 and 6SL7. The data sheets show they are equivalent but sound wise they are not as good as the true 6SN7 and 6SL7. Changing these tubes is an inexpensive exersize.
I have not yet tried substitutig 845 BUT on the weekend I fired up the 845 SET for the first time in 3 months and one 845 suffered a heater/cathode going open circuit so I have ordered a matched pair of the 845B. I should have them in about another 2 to 3 weeks. Untill then I can only go by the fact that others have suggested that the 845B is better but needs to be run sightly more conservatively as it does not have the full 100 Watt Anode dissipation rating of the ordinary 845 the amp is supplied with. I biased my amp at 83mA idle with the original 845s. With the 845B I will have to drop that to 75mA. That will drop the nominal output power of 20 Watts back to about 16 watts.
A friend who also has an MA845 is having some problems with his amp. The amps delivered into Australia seem to be designed for 220V mains. Our mains is 240 to 250V and so the High Voltage in his amp is sitting at 915V. The power supply has 2 450V rated electrolytics in series giving a 900V rating. His amp "ticks" for about 30 to 40 minutes after switch on which I am fairly certain is these 450V rated electrolytics not being happy about having 460V across them.
Cheers,
Ian
Yes the Music Angel amplifiers I have seen are all delivered with 6N8P and 6N9P rather than 6SN7 and 6SL7. The data sheets show they are equivalent but sound wise they are not as good as the true 6SN7 and 6SL7. Changing these tubes is an inexpensive exersize.
I have not yet tried substitutig 845 BUT on the weekend I fired up the 845 SET for the first time in 3 months and one 845 suffered a heater/cathode going open circuit so I have ordered a matched pair of the 845B. I should have them in about another 2 to 3 weeks. Untill then I can only go by the fact that others have suggested that the 845B is better but needs to be run sightly more conservatively as it does not have the full 100 Watt Anode dissipation rating of the ordinary 845 the amp is supplied with. I biased my amp at 83mA idle with the original 845s. With the 845B I will have to drop that to 75mA. That will drop the nominal output power of 20 Watts back to about 16 watts.
A friend who also has an MA845 is having some problems with his amp. The amps delivered into Australia seem to be designed for 220V mains. Our mains is 240 to 250V and so the High Voltage in his amp is sitting at 915V. The power supply has 2 450V rated electrolytics in series giving a 900V rating. His amp "ticks" for about 30 to 40 minutes after switch on which I am fairly certain is these 450V rated electrolytics not being happy about having 460V across them.
Cheers,
Ian
I think the MA845 comes with (some form of) 845B already, so it seems from the specs.
What do you guys think of this mod: http://www.lampizator.eu/AMPLIFIERS/CHINA/SET triode amplifier Music Angel 845 Hong Kong.html
/Erling
What do you guys think of this mod: http://www.lampizator.eu/AMPLIFIERS/CHINA/SET triode amplifier Music Angel 845 Hong Kong.html
/Erling
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