Matisse Fantasy waveform output test - 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 8th September 2005, 06:21 AM   #1
diyAudio Member
 
Join Date: May 2005
Location: HK
Question Matisse Fantasy waveform output test

Hi All,

Can anyone know my question ?

1) After I finished the Kit Matisse Fantasy, measured its output signal found a small up surging angle at the raising edge of the square wave, it would occur while the input square wave at 1K Hz.

2) When I tested it were using resistor load at 6 ohm. Is it correct to use a fixed value of resistor ? Or instead to use other type of load ?

3) The sound of it present is very well, what the affect of it would be listened ?

CK
  Reply With Quote
Old 8th September 2005, 07:04 AM   #2
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
Hi,

It sounds like overshot and it is not good that it comes even with resitive load as it indicates instability and will get worse with reactive loads. As I assume that the design is basically sound I wonder if you have changed any component values or such when you built it?

With 1kHz square wave I would expect any reasonably designed amplifier to give a nice square wave with a resistive load.

If you have built according to instructions and it is still there yoy can try tweaking the cap in parallell of the feedback resistor that goes from output transformer to some input tube, usually this is effective for reducing this ringing.

Regards Hans
  Reply With Quote
Old 8th September 2005, 08:36 AM   #3
diyAudio Member
 
Join Date: May 2005
Location: HK
Hi Hans,

This preamp is working fine without any noise trouble and hum. But I don't know is it already reach a top of its performance.

I buy a PCB and install it by myself. All components are exactly follow the PCB indicated.

Do you know this circuit or ever play it before ? I didn't have this original circuit to reference.

I can show you this circuit and values for your reference . Also welcome any suggestion to make it better. What value of cap parellel to the feedback path ? There have 2 feedback path, one located on last stage and second located between first and last stage.

Thanks for your help !
CK
  Reply With Quote
Old 8th September 2005, 02:36 PM   #4
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
Hi,

I didn't realised that it was a preamp you where talking about as you said that the load impedance was 6 ohm, is that really correct?

Anyway if the feedback is only taken over one stage I would be very surprised to find any ringing, maybe the feedback path is longer and including several stages?

In order to offer some assistance I think you need to describe the circuit more in detail and ideally to submit a circuit diagram.

Regards Hans
  Reply With Quote
Old 8th September 2005, 02:57 PM   #5
kmtang is offline kmtang  Canada
diyAudio Member
 
kmtang's Avatar
 
Join Date: Nov 2004
Location: Vancouver
I would recommend to load the output with 20K resistor instead for taking measurement. The output impedance of Matissee Fantasy is around 14K. I paralleled a 28pF capacitor to the feedback resistor to stop overshooting or ringing at high frequency. You may try to use a small capacitor and watch the output of the square wave from the oscilloscope.

By the way, I am wondering what is the grid resistor at the 12AT7. Lot of the schematic listed 47K. However, I firmly believe 47K is not a correct value. It should be 470K instead.

I built this line amp myself and experimented different things in there too.

Johnny
  Reply With Quote
Old 9th September 2005, 02:02 AM   #6
diyAudio Member
 
Join Date: May 2005
Location: HK
THanks all of you !

tubetvr -:

Sorry to make you confusing .

kmtang -:

Do you live in HK or China ?

I counter check to the schematic show that 12AU7 input in series with 510 ohm and before it connected with other 47K ohm to ground.

I use the PCB is LS27 which is provided by LITE AUDIO.

CK
  Reply With Quote
Old 9th September 2005, 03:20 AM   #7
kmtang is offline kmtang  Canada
diyAudio Member
 
kmtang's Avatar
 
Join Date: Nov 2004
Location: Vancouver
Hi CK,

I was born in HKG and moved to Vancouver, BC, Canada in 1997.

I believe the 510-ohm is the grid stopper resistor which is used to suppress chance of oscillations within the circuit.

Why don't you try to replace the 47K to 470K and listen to the differences? It may evern better if you could change the coupling capacitor from 0.47uF to 0.1uF.

The last stage should be 12AT7 unless they modify the circuitry for 12AU7 instead.

Do you mind post the schematic?

Best wishes,
Johnny
  Reply With Quote
Old 9th September 2005, 05:16 AM   #8
diyAudio Member
 
Join Date: May 2005
Location: HK
Hello Tang,

When will you visit to HK and going to Disney ?

Sorry I have typo error on "12AU7". You are right it is 12AT7.

Now I am preparing this schematic for your reference. Unfortunately, I did not have a scanner so need to redraw it again.

When I complete the drawing and posted, I want to consult with you about what values of component should be changed.

CK
  Reply With Quote
Old 9th September 2005, 06:21 AM   #9
diyAudio Member
 
Join Date: May 2005
Location: HK
Complete single channel for your reference.

Due to the oversized image , I only zip it for you.
Attached Files
File Type: zip ls27.zip (21.8 KB, 466 views)
  Reply With Quote
Old 9th September 2005, 12:01 PM   #10
kmtang is offline kmtang  Canada
diyAudio Member
 
kmtang's Avatar
 
Join Date: Nov 2004
Location: Vancouver
Disney in HK is not interested to me at all. I just want to see my family back there if I have a chance. I missed them a lot.

As I mentioned before you may try to replace the 47K to 470K and listen to the differences? It may evern better if you could change the coupling capacitor from 0.47uF to 0.1uF. I used Riken resistors and Jensen copper paper-in-oil 0.1uF for the coupling capacitor.

By the way, the last bypass capacitor in the Power Supply circuit has big impact on the sound as well. I used 3.3uF Auricap. I have a tube regulated power supply in separate chassis. I can even switch it between tube regulated or simply C-L-C-L-C filtering. I found the simple C-L-C-L-C filtering gives me very nice and smooth sound. I found it's fun playing with the power supply.

Johnny
  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
Square waveform test/simulate problem mclarenpingu Solid State 3 2nd February 2008 04:08 PM
BOSOZ Output Waveform Question hifimaker Pass Labs 8 9th April 2007 01:34 AM
SMPS output waveform discontinuities b-ohica Power Supplies 2 29th November 2006 01:24 PM
where is the"Matisse Fantasy DIY" gone reinhard The Lounge 3 17th August 2003 06:30 PM


New To Site? Need Help?

All times are GMT. The time now is 01:13 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