DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 24 Feb 2018, 22:34

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 59 posts ]  Go to page 1, 2, 3, 4, 5, 6  Next
Author Message
PostPosted: 12 Apr 2013, 02:25 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4836
Location: Australia
Because of my continual bantering of Oatley to produce a K272X which had filament batteries and powered by 18V the K272C has been developed. The K272B will probably never see the light of day being a big improvement over the K272A but not being an 18V amp and not having separate filament batteries. I liked the "B" having seperate filament resistors and thought it sounded very good in a headphone amp I built up. I think Oatley had the K272B PCBs produced but just not packaged as kits at this point. My suggestion to them was to sell the PCB for the "B" only at a reduced price and let the constructor supply his own parts. I have no answer back on this at the moment.

Blow the trumpets and roll the drums the K272C is here. I believe it will go into production. I have been sent what I think is a prototype or first run compete unit. Looks good. Big filament batteries and 18V ready. It may be a week or so before I have it as a complete portable HP unit but I am very excited to try it. I still have the K272B and as I said love it.

Oatley have included in the kit the OPA2134 high performance Fet front-ended OPAMP chip. Two leds monitor battery health. One led will indicate when the 18V is fallen to 14V by first growing dull then finally going out. Another led, monitoring the filament voltage, goes out when the filament batteries fall to 1.4V (from just over 3).

The biggest improvement is the 18V supply. Some K7272s hissed and I think it was because the driver chip (OPA2134 or PT2308) was running on too lower voltage. Also with the higher voltage across the driver chip a greater dynamic headroom should be available. I would have liked the tubes to also have a 18V HT but it appears from the cct. that there is only 9V across the tubes. Oh well.
Attachment:
K272C.jpg


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 12 Apr 2013, 10:17 
Offline

Joined: 21 Oct 2012, 00:40
Posts: 9
Cool! I'll be first in line to get one of these guys.


Top
 Profile  
 
PostPosted: 12 Apr 2013, 17:47 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4836
Location: Australia
atanguay wrote:
Cool! I'll be first in line to get one of these guys.

I have asked Oatley for a release date and price. As soon as they get back to me I will post the result. Also I have asked if the tubes, with some mods to some resistor values, can also be run at 18V. This should be possible with the change of three resistors.

_________________
Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 16 Apr 2013, 16:56 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4836
Location: Australia
I have just been informed by Oatley that the K272C will be available for purchase in 14 days - 1st of May 2013. I am still trying to get an answer if the tubes are now on 18V. The storage cap just prior to the tubes is marked 10V??

_________________
Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 20 Apr 2013, 03:09 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4836
Location: Australia
My wife through a steel can at me and said "build an amp in this". The steel can sat around for a few weeks then I got the K272C prototype cct. brd. I started to think "can I do this". I will save you a few dozen thought processes and move you to the present.

I'm going to build what I call a nood (Nu*de) build and it is a headphone preamp based on the K272C. What it is is that though the headphone amp will be contained in the steel can you will have to pop the top to connect to the amp. The cct. brd. (quite pretty) will sit on a varnished and polished ply base with the headphone jacks and switches exposed. The batteries will be slung underneath. Hard to explain and future photos will fill in the gaps.
Attachment:
CanAnd.jpg
Attachment:
CanAndII.jpg


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 20 Apr 2013, 10:19 
Offline

Joined: 21 Oct 2012, 00:40
Posts: 9
That's going to look really cool. I like the idea.


Top
 Profile  
 
PostPosted: 21 Apr 2013, 08:27 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4836
Location: Australia
The cct. brd. was pre-assembled so my job was to fit it to some sort of case. In this build the case would only ever house the nood cct. brd. and by popping the top you could connect what ever device you wanted. The PCB sits on a twice sanded and varnish light wooden plinth. I originally wanted the cct. brd. to sit on sticky feet but due to the fact I mounted the phono jacks too wide, thus raising the cct. brd. to high to fit in the tin, I had to swap to slit rubber grommets. This may have been a blessing as the final result is far superior to the original idea.

Two 9V batteries (18V) hang under the plinth in battery clips and phono jacks are double-sided-taped to the bottom of the plinth. I have once more employed my "safe on" technique which ensures no chance of leaving the device on and packed away. Have the PCB being able to be removed easily from the can means you can check the two battery level leds and therefore know when to replace batteries. I'm pleased with the whole build. Studs will be added to the bottom of the tin so the can will sit still and upright.
Attachment:
FinisI.jpg
Attachment:
FinisII.jpg
Attachment:
InCan_I.jpg
Attachment:
InCan_II.jpg


On a very brief listen I was impressed with total warmth and bass weight. I need a lot longer listening time for a better assessment but this one (K272C) feels and sounds like a winner.


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 21 Apr 2013, 22:54 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4530
Location: Winnipeg, CANADA
Nice. I was wondering how you would fit the headamp in it the metal can.

Cheers

_________________
[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


Top
 Profile  
 
PostPosted: 22 Apr 2013, 00:49 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4836
Location: Australia
The earlier images really did show how this whole little project hangs together. The lid is under the preamp doubling as a stand.
Attachment:
K272C.jpg


This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.


_________________
Projects: "Sanctum" - 12AU7 and 6AS7 direct coupled headphone amp | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "Mimic Carbon" - carbon resistors and PIO caps. MM phono preamp
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 22 Apr 2013, 11:25 
Offline

Joined: 21 Oct 2012, 00:40
Posts: 9
What's the plan for the end? How about laser cut black acrylic? 8-)


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 59 posts ]  Go to page 1, 2, 3, 4, 5, 6  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Google Adsense [Bot] and 7 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy