Help! Upgrade a Music Angel KT88 - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 20th June 2008, 09:05 PM   #21
diyAudio Member
 
Join Date: Feb 2007
Location: victoria canada
There is not connection to ground for the power supplys either. Seems like everything is floating. The schmetic I got from the guy who does the warrenty work shows no gnd either.
  Reply With Quote
Old 25th April 2009, 08:04 PM   #22
jompo is offline jompo  France
diyAudio Member
 
Join Date: Jan 2009
Default triode/UL switch

Hello,

I did not understand how exactly to disable the triode/UL switch on the Music Angel KT88 (I have attached shematic).

Thank you for help,

Joel
Attached Files
File Type: pdf music_angel_kt88_schematic.pdf (83.3 KB, 430 views)
  Reply With Quote
Old 25th April 2009, 11:17 PM   #23
pointy is offline pointy  United Kingdom
diyAudio Member
 
pointy's Avatar
 
Join Date: Mar 2009
maybe a choke.........................?
  Reply With Quote
Old 29th April 2009, 02:11 AM   #24
jompo is offline jompo  France
diyAudio Member
 
Join Date: Jan 2009
Default triode/UL switch 2

I think I got the response for my question about disabling the UL/triode switch on the Music Angel KT88 on this diyaudio thread

"remove the wire(s) from pin 4 (1 wire per tube). Connect pin 3 and 4 with a 100 ohm resistor (or with the resistor on the way from relay to pin 4). Also remove the 2 power connections to the relays".
  Reply With Quote
Old 3rd May 2009, 10:56 PM   #25
jompo is offline jompo  France
diyAudio Member
 
Join Date: Jan 2009
Default Re: triode/UL switch 2

Quote:
Originally posted by jompo
I think I got the response for my question about disabling the UL/triode switch on the Music Angel KT88 on this diyaudio thread

"remove the wire(s) from pin 4 (1 wire per tube). Connect pin 3 and 4 with a 100 ohm resistor (or with the resistor on the way from relay to pin 4). Also remove the 2 power connections to the relays".
An additionnal picture of the modifications I made.
Attached Images
File Type: jpg triode-mod-kt88-music-angel.jpg (98.4 KB, 748 views)
  Reply With Quote
Old 12th May 2009, 12:00 PM   #26
diyAudio Member
 
Join Date: Apr 2009
Send a message via MSN to annolsen2009 Send a message via Yahoo to annolsen2009
I see the Music Angel KT88 is similar to XiangSheng Music Cruve D2020-KT88.

http://www.xshn.com/en/display.asp?id=5
__________________
I like tube amplifiers and music.
  Reply With Quote
Old 24th July 2009, 09:44 PM   #27
RCruz is online now RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Hi All

I am now starting to "cure" onr of these amps... It is in stock form and I must draw a schematic before anything because I believe these amps circuits are very variable.

I am not an experieced tube modder so I will need all the help available.

Is it possible to remove the feedback without major surgery ?

Hope I am not beeing too boring... again....

Ricardo
__________________
RC
  Reply With Quote
Old 24th July 2009, 10:11 PM   #28
diyAudio Member
 
Join Date: Dec 2007
Send a message via AIM to kyleaudio
this link might be helpful to you, not sure how good it is tho. http://lampizator.eu/AMPLIFIERS/CHIN...reworking.html
  Reply With Quote
Old 25th July 2009, 01:48 PM   #29
RCruz is online now RCruz  Switzerland
diyAudio Member
 
RCruz's Avatar
 
Join Date: Sep 2006
Location: Wallis
Blog Entries: 1
Thank you

I have seen this before but as there is no explanation for the actions taken, I must design a schematic and do these mods on paper so I can understand every mod.

Ricardo
__________________
RC
  Reply With Quote
Old 24th August 2009, 11:34 AM   #30
diyAudio Member
 
Join Date: May 2009
Hi guys .... I'm new here and I too have an Music Angel KT88 which I'm modifying.

things I did;

- disconnected the switch at the back
- done the hardwired triode mod between pins 3 and 4 on all KT88's
- set the bias on all 4 to 35mA as a test but now I notice that the power-supply transformers are getting a bit too warm .... and I don't like it really.
before the bias was set to 25mA ... everything stayed a lot cooler.

But now ....
because I started to get .... only after a while, say about an hour or 2 when the tubes are heated up very well ..... a kind of high whistling noise in the right channel only when I'm playing the amp on really low volume.
Even when I mute the input ... I can still hear it ans it's a rather irritating high pitched tone. It differs a bit in volume too .... somethimes it even disappears for a second or 2. It looks like a kind of oscillation ...
I also had a lot of "microfonie" on the small tubes. When I gave a very little tick on the tubes .... with a pen or so .... it was very audible in the speakers.
So I thought .... old tubes .... let's change them.

I already changed valves 1 and 4 ... the phase turners ...the ones labelled on the amp and in the schematics as 12AU7.
I swapped them with a pair of balanced NOS Sylvania 5963 tubes and this worked fine .... at least the microfonie problem is gone.
I was supprised a lot when I noticed that the originals were 2 different tubes .... one was a 5963 ... the other one a 5965 ... can you imagine ..

With the swap of the other 2 valves ... 12AT7 ones .... something went wrong.
12AT7 printed on the amp and in the schematics .... seemed to be that the original ones were Shuguang 6N1 tubes ... printed that way on the tubes.
I swapped them with a balanced pair NOS Philips JAN 12AT7WC and things started to go wrong. Didn't look on the prrint on the tubes themself ... my mistake ...
From the first moment there was a difference in volume between left and right channel ... after about 2 hours orso the right channel stopped working.
I bought the tubes in holland .... I myself live in Belgium .... and the man from the shop mailed me and said that the 6N1 and the 12AT7 are not the same .... they are not 1 one 1 swappable !

So the philips tubes are send back and I'm now waiting for a pair of russian 6n1p-EV tubes. I hope everything will work fine then.

But ... in the mean time ... I plugged the old 6N1's back in place and still .... when the amp is heated up well .... I do still hear that irrating high noise in the right channel .... so if somebody can help me with this problem ....
you're wellcome
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
music angel kt88 vitalstates Tubes / Valves 1 27th February 2008 04:31 PM
Please tell me how to upgrade Music Angel KT88 amplifier? hififactory Tubes / Valves 26 29th December 2007 03:04 PM


New To Site? Need Help?

All times are GMT. The time now is 06:52 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2