KT88 SE Basic or Master Kit - Page 10 - diyAudio
Go Back   Home > Forums > Commercial Sector > Vendor Forums > Vendor's Bazaar

Vendor's Bazaar Commercial Vendors large & small hawking their wares

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 19th February 2012, 05:06 PM   #91
iNSuL is offline iNSuL  United States
diyAudio Member
 
Join Date: Apr 2009
Original bias was closer to 4 volts, so two 2v leds would be better. I started out with those exact ones and moved up to the 2 volts.

Jonathan

Last edited by iNSuL; 19th February 2012 at 05:07 PM. Reason: spell
  Reply With Quote
Old 19th February 2012, 05:10 PM   #92
debk is offline debk  United States
diyAudio Member
 
debk's Avatar
 
Join Date: Mar 2010
Location: Watertown, NY
What was the difference in the sound using the 2V LED's ?

Debra
  Reply With Quote
Old 19th February 2012, 05:34 PM   #93
iNSuL is offline iNSuL  United States
diyAudio Member
 
Join Date: Apr 2009
To me it made it a little colder, more sterile sounding. Highs seemed a bit more harsh. Not by much though, both still sound really detailed.

Jonathan

Last edited by iNSuL; 19th February 2012 at 05:37 PM. Reason: .
  Reply With Quote
Old 19th February 2012, 05:42 PM   #94
debk is offline debk  United States
diyAudio Member
 
debk's Avatar
 
Join Date: Mar 2010
Location: Watertown, NY
I just ordered a few different LEDs. I will have to experiment with it.

Thanks for the information

Debra
  Reply With Quote
Old 19th February 2012, 07:28 PM   #95
diyAudio Member
 
regiregi22's Avatar
 
Join Date: May 2009
Location: Madrid (Spain)
Try combinations of different LED colors, as each one will have a different voltage drop.
__________________
diyAudio, doing it as big as you can, JUST BECAUSE WE CAN!
  Reply With Quote
Old 19th February 2012, 08:50 PM   #96
debk is offline debk  United States
diyAudio Member
 
debk's Avatar
 
Join Date: Mar 2010
Location: Watertown, NY
Just trying to see if I understand this correctly.

If I were to bias the 6n1p with two HLMP-6000, the new bias voltage would be about 3.2V. This would give a slightly higher Plate current. In the original design the current is 4mA, an easy point to read off the curves. Changing to the 3.2mA bias the current would increase to around 5mA if I extrapolated the curves correctly (eyeballing on the computer screen). Would you have to decrease the Plate resistor to keep the plate voltage constant and keep you out of a nonlinear part of the curve. If the 3.2V bias truly gives around a 5mA bias current than the by my calculations the plate resistor should be dropped to around 39K to put you on a linear part of the curve.

I may be way off here, but trying to understand how the circuit works.

Debra
  Reply With Quote
Old 19th February 2012, 09:48 PM   #97
diyAudio Member
 
scott17's Avatar
 
Join Date: Aug 2009
Location: JFK
Quote:
Originally Posted by debk View Post
If the 3.2V bias truly gives around a 5mA bias current than the by my calculations the plate resistor should be dropped to around 39K to put you on a linear part of the curve.
Debra
That looks to be about right. I've read that when biasing with LEDs, a little more current, say around 10mA, helps with the linearity. With this circuit, the current through the 6N1P could be increased to 6mA by paralleling a 68K 2W resistor with the existing 47K. That would be an effective 28K (about), and would also maintain the -4V bias point. At 6mA, if you wanted to go back to a resistor/cap for the bias, the new value is 680R 1/2W.
  Reply With Quote
Old 20th February 2012, 04:16 PM   #98
diyAudio Member
 
regiregi22's Avatar
 
Join Date: May 2009
Location: Madrid (Spain)
Just out of curiosity, is it possible to get the part numbers of the MP oil capacitors?

ASC Capacitors - Products
__________________
diyAudio, doing it as big as you can, JUST BECAUSE WE CAN!
  Reply With Quote
Old 20th February 2012, 07:11 PM   #99
diyAudio Member
 
scott17's Avatar
 
Join Date: Aug 2009
Location: JFK
Quote:
Originally Posted by regiregi22 View Post
Just out of curiosity, is it possible to get the part numbers of the MP oil capacitors?

ASC Capacitors - Products
The capacitors are Panasonic:
DS371506-CA
DS371306-CA
  Reply With Quote
Old 22nd February 2012, 01:22 AM   #100
debk is offline debk  United States
diyAudio Member
 
debk's Avatar
 
Join Date: Mar 2010
Location: Watertown, NY
One more LED bias question. I have done some reading on this circuit. Some are advocating biasing the 6N1P at around 3.2V or so (two 1.6V red LEDs) , instead of the 4V the specified resistor will give you. This bias point should run the tube at a slightly higher current. If you were to do this does the 47K plate load resistor need to be tweaked?

Also has anyone tried replacing the plate load resistor with a constant current source?

Debra
  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
KT88 SE Complete Kit scott17 Tubes / Valves 289 4th March 2013 08:09 PM
AnalogMetric 6L6GC SE amp kit...thoughts about this kit? jmillerdoc Tubes / Valves 2 16th November 2009 02:51 PM
Kt88 Se overdrajv Tubes / Valves 0 16th December 2008 12:26 PM
My KT88 SE project JesseG Tubes / Valves 8 20th April 2008 04:26 AM
Kt88 Se hacknet Tubes / Valves 9 10th September 2004 08:19 AM


New To Site? Need Help?

All times are GMT. The time now is 12:42 AM.


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