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Review of New S-5 K-16LS Kit

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After building, troubleshooting (thanks to those who helped) and burning in of the new s-5 16 Wpc stereo amplifier kit, I want to share my thoughts for anyone who may be interested. The kit is straightforward and easy to build and comes with pretty good instructions. I decided I wanted to hear its sound mostly stock before I upgraded poly film capacitors or anything like that. The modifications I did make include:
-metal chassis
-3 prong power supply grounded to the chassis with toggle switch
-AC cooling fan
-Bigger filter caps (220 uF, 220 uF, 100 uF instead of 220, 100, 22)
-270K bleeder resistors on filter caps
-bypassed capacitors on RCA inputs with wire
-Gold-plated chassis mount RCAs and binding posts

I included the fan because I'd heard that other s-5 power transformers got pretty hot. I think this PT is a beefier one than with the k-12 and the fan is probably not necessary.
First impressions of the sound are that it has a noticeably different tone than my several run-of-the-mill solid state amplifiers. Sound is warmer and more vibrant. With the input source paused, there is very little noise and no noticeable hum even at full volume. I didn't even add any snubber capacitors yet, but I'm already satisfied. I did attach the tone control option from s-5, which I'm glad I did, as different styles of music and different recordings require some adjustment to sound good. With the proper adjustment of the tone controls, bass, treble and mid are all satisfactory. With my Klipsch Heresys, full volume exceeds comfortable listening level and bass is ample.
Keep in mind this is my first experience with tube audio and I have never heard other tube amplifiers for comparisson. Thus, I'm probably not the best person to review an amplifier for tube enthusiasts. But, I would say that, at a total investment of under $400, the amp sounds noticeably better than the $350 solid-state amplifier it is replacing.
 

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its good to see a review of tis kit-there was another one on http://diyaudioprojects.com/, but that was mainly about the results of a scope test- a description of the sound quality would of been a plus.

diyaudioprojects is a great resource (and good reading), to be fair they did ask for experiences with this kit to be shared and compared.

however a 2nd opinion was needed in my view as I think the kit is good value!
 
Here are Bruce's measurements of the S-5 Electronics K-8LS Tube Amp Kit. As far as we are aware, these are the only measurements of the new kits right now. As you mention, it is important not to pass judgment based on just one set of measurements.

We have had a small handful of subjective emails, some good and some bad. Here is a link to some subjective comments about the K-8LS kit:

http://www.diyaudio.com/forums/showthread.php?postid=1310309#post1310309

These comments seem to confirm the poor response in the bass region.


dubdub said:
its good to see a review of tis kit-there was another one on http://diyaudioprojects.com/, but that was mainly about the results of a scope test- a description of the sound quality would of been a plus.

diyaudioprojects is a great resource (and good reading), to be fair they did ask for experiences with this kit to be shared and compared.

however a 2nd opinion was needed in my view as I think the kit is good value!
 
Just Ordered One

This will be my first build. Wondering if anyone has any advice?

I am lucky enough to have access to a machine shop so I'm going to make a chasis out of aluminium.

I was thinking of making some transformer covers too. I know this is very extravagant for a cheap kit but I have access to free metal so I figured why not...

I would be interested to hear peoples ideas on chasis design.

I am going to use some decent RCA's and binding posts.

I was thinking of using chasis mount valve sockets then wiring these to the PCB. Can anyone foresee any problems with this?

Also any other weird and wonderful ideas... Throw them my way.

I want to make the most extravagant ridiculous cheap *** amp I can.
 
Hey Ben10

I just finished the same S-5 K16LS Kit. I upgraded all of the caps, it reduced the hum considerably. I have to agree, for a cheap little kit, these sound good! My next brain fart will be to get rid of the silicone in the power supply with center tapped hammond transformer, and a 5u4gb tube. Another item I added was a 8 henrie choke in the power supply.
I didn't get the optional tone control, but instead the pre-amp kit. I have a very small listening room, and it will blow you completely out!
Even using cheap Jensen MOD speakers...

I am still amazed at how clean and in depth the sound is! My only other experience with tubes has been guitar amps, no hi-fi.
 
The chasis I am using is being custom made by a friend of a friend who owns a metal fab shop. It's all aluminimum and is 13X13 inches at the base. The base is 3 inches in height. The back 5 inches of the base will stick up an additional 6 inches. So the first 8 inches (front to back) is your standard 3 inch box. But the back 5 inches steps up to form a backboard on and in which I can put things. In the flat base the main board of the amp goes with tubes thru holes - standard style On the back, step up part I am installing the tone and base contol board, placing the transformers, installing some retro VU meters, and installing all switches, illumination indicators and pot knobs. I am relocating all volume, tone and bass pots of course and adding a 4 way stereo rotary switch to change between inputs. On the tone /bass control there is a tube. That sticks out with the top pointing to you, 90 degress from the other tubes sticking up.

I'm going for a retro, industrial sort of look. Attached is a sketch.
 

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Regarding the comment about heat etc. The heat will go up away from the back - I also did a cardboard mockup to make sure the hand burning thing would be ok. You make some good points and may be ultimately proven right but I'm forging ahead. One thing I can do if needed is put in a fan. Still 90% of the heat in this amp is right off the top of the tubes. As they are out in the air the heat should not build up in that back area. And I do plan to have the back covered with a grill.

Regardng the request for a schematic, I had it in an earlier post.

Here's a link :

http://www.diyaudio.com/forums/attachment.php?postid=1501947&stamp=1210002142

Hope it works. Any easy suggestions for improvement appreciated.
 
Hi everyone,

I built a K-502 from AES some months ago. The schematic looks quite similar to the K-16LS although it is a simple PP amp (not parallel).
I did a few cheap modifications that improved the overall performance:

- Get rid of the bridge rectifier and replace it with four Fast Recovery or Schottky diodes (I used cheap UF4007, but Schottkys might be a better choice). I also added some snubber caps across the HT and filament supplies. Makes the amp more quiet.

- I paralleled the HT cap (C10 in your schemo) with a Solen 22uF PP film.
Hugh improvement in detail (Highs, but also in bass - maybe a case of placebo, since I have no switch to go back and forth). Even if Placebo, I liked this mod very much.

- I replaced all coupling caps (the 0.22uF films) with Solen 0.22uF PP film (cheap). Higher quality (like Auricaps etc. might give further improvement).

- Replaced the stereo potentiometer with an ALPS Blue Velvet Stereo pot. No obvious sound improvement, but hopefully more reliable.

On the contrary, bypassing the cathode resistors (R12 and 25) with 220uF low ESR electrolytics did not help for my ears - actually sounded worse?!?

These are a few simple and very cheap modifications I have done that helped a lot. Especially the diodes help to quite the amp down.
The cap mods made some sound improvements.
I was so happy about that amp that I did not feel bad to give it to a very close friend who likes it very much. If this is how a low quality tube amp sounds - how much better can a high quality amp be?
This amp actually made me enjoy listening to music so much that it was hard to turn it off in many cases.

I hope you enjoy your K-16LS as much.
Regards,
Martin
 
SY,

If one had a great big pile o' 6005's and were considering to do a point-to-point build of this amp, what mods might you suggest. :)

The only major difference I'd throw in would be a 8k primary OPT with 8-16-32 ohm secondaries. Pentode mode only. I figure 4k ohm primaries should be OK.
 
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