Review of New S-5 K-16LS Kit - 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 15th June 2008, 05:51 PM   #21
diyAudio Member
 
Join Date: Jun 2008
Cool Some sugestions

Power transformer only 52 watts, but it loaded on 74.
It getting hot as hell.
Tube 6005 has a blue lights inside, it bad sign, vacuum was lost.
Probably of long storage period.
I made some changes, put other transformer for filament ( took off 30 Watts from the main, anyway it was overloaded, max current 4.0 when it was drained on 0.45x8 + 0.35x2 = 4.5 A ).
I also decreased resistor R12 and R25 to 80 Ohm, in original it was 150, so tube operated in class B, slightly colored to AB2 ( 100 mA / 4 tubes = 25 mA each, when spec for tubes 45 mA for A, and 35 for AB ).
The same time loaded PT again, this time up to 64 watts, I 'm thinking to get rid of this limiter...
Other thing low gain, voice from your CD would not be enought to get 16 watts output. All you can get it's around 2 watts.
I have to think about it.
Kit is very good for begining, push you to think and troubleshoot.
Open for discussion.
  Reply With Quote
Old 10th August 2008, 06:36 AM   #22
zcables is offline zcables  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Seattle
Sorry to dig up an old thread, but I there is good information here.

I finished this kit a while ago, but thought would let it burn in before moding it any. I like the sound quality and it was a pretty easy build, but I have a bit of a noise problem. It's isn't too noticable if the volume stays below 12 o'clock, but it is something I would like to address. It looks like replacing some caps have helped some of you in the past. Which caps helped?

Thanks,
Jake
  Reply With Quote
Old 10th August 2008, 03:22 PM   #23
diyAudio Member
 
bayermar's Avatar
 
Join Date: Oct 2007
Location: Tuebingen
Hi Jake,

if the noise is a buzzing sound it is likely coming from the HV rectifier.
There is a simple fix to that. VoltSecond describes it very nicely on his homepage:
http://www.siteswithstyle.com/VoltSe...Push_Pull.html

If the noise is more like a humming sound it may come from the filaments. You can use a voltage divider on the HV supply generating ~30V to lift the center tap of the filaments to this level (instead of ground).
I used 1M and 100K in series from HV to ground. Parallel the 100k with a 47uF capacitor. Now connect the center tap of the filament winding to the voltage divider (should be around 20-25V at the junction of the two resistors).
This basically eliminates any AC hum on the filaments. It worked very well on my K-502 and my version of Gingertube's Baby Huey.

I hope this helps.

Martin
  Reply With Quote
Old 12th August 2008, 09:04 PM   #24
zcables is offline zcables  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Seattle
It is a buzzing noise that comes mainly from the tweeters like you were saying. Looking over the link, it looks like I should put a 0.01 uF cap across the HV transformer leads. Can you help me with exactly where in the schematics that is?

Click the image to open in full size.
  Reply With Quote
Old 12th August 2008, 09:50 PM   #25
diyAudio Member
 
bayermar's Avatar
 
Join Date: Oct 2007
Location: Tuebingen
Hi Jake,

the capacitor would go across the two connections where the two red HV secondary wires of the power transformer are connected to the PC board. Make sure this cap has a high enough voltage rating (2kV ceramic or 600V film cap).
You can improve further by replacing the bridge rectifier with 4 UF4007 diodes. This will need a little improvisation since there is not much space on the PC board. Take a look at VoltSeconds homepage again.
The version with the snubber network might be even better (called HV snubber Version 2 on his page).
He then shows how to use a single Ultra-Fast diode in combination with the bridge rectifier, this should work also very well with above Snubber network and will improve the situation further.
I do not know how much the filament snubbers help but it is an easy thing to do and VoltSecond shows nice pictures how to do it if you can't figure it out by yourself.
Taken together, these are simple mods that improve the noise of these amps a lot.
Make sure you check and discharge ALL HV capacitors before working on the amp .
Also have a look at the sticky safety post here in the forum if you are not very familiar with high voltages already.
If the buzz is gone you can try to get rid of any hum that is still present but that is usually less annoying (sine wave).
Good luck!
Martin
  Reply With Quote
Old 14th August 2008, 09:46 PM   #26
zcables is offline zcables  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Seattle
Being that I have limited high voltage experience, I am going to perform the mods on my amp under the direction of my EE/HAM father-in-law. I figured it would be the safest way to go, plus he could help me figure out anything if I get stuck. I don't have time to do it until a week and a half from now, but I guess I'll just have to be patient.

I know I'm going to install the first mod (.01uF cap) and maybe more, but I'll cross that bridge when I get there.
  Reply With Quote
Old 21st August 2008, 02:53 AM   #27
zcables is offline zcables  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Seattle
In the original post, one of the upgrades suggested was: -Bigger filter caps (220 uF, 220 uF, 100 uF instead of 220, 100, 22). I might tackle this as well when I fix a few other things, but I am wondering if these have to be polarized, electrolytic caps like the originals? Also, should I stick with the stock 250v?
  Reply With Quote
Old 21st August 2008, 03:28 AM   #28
gofar99 is offline gofar99  United States
diyAudio Member
 
Join Date: Jan 2007
Location: Arizona USA
Hi, The caps could be non-polorized, if you can find ones big enough with enough voltage rating (rather costly as well). Polorized electrolytics are fine for this application. I would use ones of at least 350 volts rating. I use 100 uf in my amp in the third position. The caps are inexpensive, however, I suggest you not use the bottom of the line cheapies. The power supply can be considered the other half of your sound path. You want it to hold up its end of the job. There are a number of good sites on the web that explain this aspect of the power supply. Rather that repeat stuff that is elsewhere, if you want PM me. Recently, I have had good luck with "Ruby" and "JJ" brand caps. You can spend a lot more but the return on the K series of amps is probably not worth the cost.
__________________
Good Listening
Bruce
  Reply With Quote
Old 21st August 2008, 07:37 AM   #29
zcables is offline zcables  United States
diyAudio Member
 
Join Date: Aug 2008
Location: Seattle
I found these 220uf and 100uf caps for the filter caps upgrades. Am I on the right track?

http://www.partsexpress.com/pe/showd...number=020-658

http://www.partsexpress.com/pe/showd...number=020-656

Thanks for all the help and I'm learning more every day.
  Reply With Quote
Old 21st August 2008, 02:42 PM   #30
gofar99 is offline gofar99  United States
diyAudio Member
 
Join Date: Jan 2007
Location: Arizona USA
I Learn a bit every day. Audio, especially dealing with tubes is rewarding and challanging. In spite of modeling programs, computers and lots of literature it still has an element of art involved.

The caps you selected are ones I have used in a number of projects and work well. One of my K-12s uses those exact parts. I'm glad to be of help.
__________________
Good Listening
Bruce
  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
K-16ls kevin.dickerson Tubes / Valves 7 27th April 2011 01:37 AM
K-16LS Help Please Madmen Tubes / Valves 6 10th December 2008 09:26 PM
S-5 K-16LS Kit arrived in Germany !! lufton Tubes / Valves 10 19th November 2008 10:59 PM
K-16LS kit Assembled and Working 123rmp Tubes / Valves 10 14th July 2008 01:21 PM
S-5 16LS tube amp use with 8 ohm speakers 123rmp Tubes / Valves 8 13th April 2008 11:40 PM


New To Site? Need Help?

All times are GMT. The time now is 09:07 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