S-5 Electronics K-12M (11MS8) 8 wpc PP Tube Amp Kit ($139) - Page 8 - 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 29th March 2005, 04:11 AM   #71
diyAudio Member
 
gmilitano's Avatar
 
Join Date: Apr 2004
Location: Winnipeg, Manitoba
Default Re: volume pot in shunt mode

Quote:
Originally posted by james_b
GG, since you already removed the DC blocking caps you may be interested in this thread on the Decware forum on running the volume pot in shunt mode with an added resistor

http://www.decware.com/cgi-bin/yabb/...num=1110965291
Funny that you mention this. The original pot that came with my kit was starting to fail so I replaced it with an old recycled pot. Anyway, I do not like how this pot positions (normal listenting level is about 2-3 oclock) so I had already read about doing this on this passive preamp thread:

Passive Preamp

Quote:
Originally posted by bhd812
Hello everyone I am new here to the forums, I am mostly on the headfi.org...yeah I am a headphone guy.

anyway I bought this kit last week and fell in love with it.

I have another kit coming in this week so I can run these as mono's, and I already know how to do it.

the gear I am using the kit in is a Meridian G08 cdp and NORH 6.6 speakers (93db senn)...

any thing else I should be looking into as mods?

thank you and its glad to be here, I can see myself here for a long time.
I too have been very pleased with this kit. I was not expecting this sort of performance for $139.

As for mods, you must visit:

http://www.siteswithstyle.com/VoltSe...Push_Pull.html

I have tried most of VoltSeconds mods. Those mods are very well thought out and they are well documented.

Also, you can visit my site for some additional capacitor mods.

Of the mods I have tried, I would stongly reccomend the snubbers on the filaments and the HV. Also, if your sources do not pass DC, removing the DC blocking caps made the biggest improvement of all the mods I have tried. I also found that upgrading the coupling caps to film/foil caps made a large improvement.

Good luck,
Gio.
  Reply With Quote
Old 29th March 2005, 11:06 PM   #72
diyAudio Member
 
nullspace's Avatar
 
Join Date: Oct 2004
Location: Phila., PA
Hi All --

This past weekend I finished my rendition of this amp, I have the k-502 from AES with 11BM8 tubes, and while I'm very happy with the reults I'm not too keen on the lack of bleeder resistors -- as a first-time DIYer, I'm suitably paranoid about it all.

Voltsecond's CCS mod is one way of rectifying that, and I was wondering if Doc B's C4S kit would work here.

Thanks in advance for your yay or nay.
John
  Reply With Quote
Old 30th March 2005, 12:06 AM   #73
james_b is offline james_b  United States
diyAudio Member
 
Join Date: Jun 2004
Location: Herndon, Virginia
Thumbs up Voltsecond's CCS mode for K502

John,

I have the K502 amp and recently built the CCS mod for it tailored for the K502 amp. Voltsecond was kind enough to discuss it with me and suggested some changes on a few of the components to suit the K502. The K502 uses 200ohm 3W cathode resistors where the S5 used 300ohm, plus my voltage readings across these cathode resistors was only 15V where the S5 had 25V. I corresponded with one other K502 owner who had similar voltage readings on their kit. Voltsecond recommended the following changes:
-do not use an LED
-do not use R5, R6 or R7
-for R2 & R3 use 120k 1/4W [instead of 130k]
-for R4 use 100ohm 1/4W - [instead of 110ohm]
All the other components are the same. He said that would leave enough power later for the balance mod he is working on.
This has been in my amp about two weeks now and I really like it, it does make the sound a little softer and smoother. Just use clipon heatsink clamps when you solder, especially the hex/mos fet, capacitor & diodes.
  Reply With Quote
Old 30th March 2005, 02:11 AM   #74
chromal is offline chromal  United States
diyAudio Member
 
Join Date: Feb 2005
Location: Evergreen, CO
Heh, I figured I'd weigh in here again, I've been mostly silent lately.

I replaced the 300 ohm 3w cathode resistors with 400 ohm wirewound 5w resistors. I wanted to use 500 ohm resistors, but the company I bought 'em from screwed up and included a 50 ohm resistor. I should have followed my rule of buying extra passives with each order.

Anyway, This increase in cathode resistance raised the cathode about 2v, and dropped the zero-signal current through the tubes about 1.25w each. This also caused the B+ voltage to jump up a bit, maybe 5-10v.

I hooked up a function generator and watched the L channel OT secondary across a 4ohm dummy load. Looks like the more-or-less stock amp can go up to about 45khz without any loss in gain, with a half-voltage on the output up around 75khz. (1/2 voltage == -3dB? Highpass Cutoff?) Square wave output gets a bit funky below 1000Hz, and definitely things go south below around 100Hz. I need to do some checks and make sure my function generator is healthy, because the square waves coming right out of it don't look all that square, with sloped plateaus at lower freqs, so, YMMV....

It does appear that this amp boosts upper freqs. As I sweep a tone up, the output voltage peaks tend to show some moderate (maybe up to 15-20%) magnitude gain, at least to a point.

Has anyone thought about or tried triode strapping? Does anyone know what the primary:secondary turn ratio is on the OTs?
  Reply With Quote
Old 30th March 2005, 11:39 PM   #75
james_b is offline james_b  United States
diyAudio Member
 
Join Date: Jun 2004
Location: Herndon, Virginia
Default will triode strap soon

I plan on triode strapping my amp soon. I have not found any other posts where anyone has triode strapped the K12M or K502 amp. There was one post where the two OPT's were replaced with Hammond 1609's and wired in ultralinear mode with great results. I figured I would try triode strapping first as the cost of 4 resistors and some wire is much less than 2 OPTs at @ $75/pair. When I went back and looked for this link I found a new post on other mods everyone may be interested in, like replacing the 2 33pf ceramic caps with silver mica caps, so since both amps are similar here it is also.
http://diytube.com/phpBB2/viewtopic.php?t=152
http://diytube.com/phpBB2/viewtopic.php?p=3092#3092
  Reply With Quote
Old 31st March 2005, 07:22 PM   #76
diyAudio Member
 
nullspace's Avatar
 
Join Date: Oct 2004
Location: Phila., PA
Just because you brought up swapping transformers... if you were change out the power transfomer, which Hammond would you pick and how would you know that that one is the right one? I'm more interested in how you'd figure out which one is the right one than actually knowing which one, if that makes any sense.

Thanks, John.
  Reply With Quote
Old 31st March 2005, 07:34 PM   #77
percy is offline percy  United States
diyAudio Member
 
Join Date: Apr 2004
Location: MN
Quote:
Originally posted by chromal
Has anyone thought about or tried triode strapping? Does anyone know what the primary:secondary turn ratio is on the OTs?
Quote:
Originally posted by nullspace
if you were change out the power transfomer, which Hammond would you pick and how would you know that that one is the right one?
I can't find my notes as I never built this kit - which at some point I was going to. But I believe the OPT primary Z is 10k and yes I was going to use the Hammond 1609. I cant remember the power transformer but measure the ac voltage across the secondary and the total current drain of the amp, that should give you an idea of the rating you need. Same for the heater winding/transformer.
  Reply With Quote
Old 23rd May 2005, 05:05 PM   #78
diyAudio Member
 
nullspace's Avatar
 
Join Date: Oct 2004
Location: Phila., PA
Hi All --

I picked up four of the FREDs that Blackie mentioned back when this thread was getting started, and I plan on doing something with them this weekend.

However, I was wondering if someone has a better idea than mine on building the bridge. I was planning on juggling the four FREDs so that the anodes and cathodes lined up, then running a lead from each of the four points back to the PCB. Will this work, or is there a better way to build a rectifier from TO-220AC diodes?

Thanks for the help,
John
  Reply With Quote
Old 24th May 2005, 07:07 AM   #79
diyAudio Member
 
Join Date: May 2005
Location: Usa
Send a message via AIM to killerfishes
On the bord, if i jumped the two pads "unused" to the side of R8 and R17 with a switch would it make the nvb on option of are the pads for some other mod?
  Reply With Quote
Old 28th March 2006, 05:34 PM   #80
MassMat is offline MassMat  United States
diyAudio Member
 
Join Date: Mar 2006
Location: New England
Quote:
Originally posted by killerfishes
On the bord, if i jumped the two pads "unused" to the side of R8 and R17 with a switch would it make the nvb on option of are the pads for some other mod?
The unused pads are most likely meant for bypass caps for the common cathode resistors (R8 and R17) for the push-pull pairs.

Adding a pair of 50uf 25V caps will improve the bass response, although some people might cringe with the mere thought of adding an electrolytic cap into the signal path.
  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
Sub amp/speaker to compliment S5 electronics K 12 G tube amp xxguitarist Tubes / Valves 0 22nd April 2009 02:57 AM
S-5 Electronics Tube Amp Kit dru85 Tubes / Valves 5 10th June 2006 04:16 PM
S5 Electronics 139 $ tube amp Gubby Tubes / Valves 4 19th November 2004 04:28 PM
Four matched 11MS8 tubes - all RAYTHEON percy Swap Meet 0 25th October 2004 04:51 PM


New To Site? Need Help?

All times are GMT. The time now is 12:30 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