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 13 Jul 2020, 18:33

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 484 posts ]  Go to page Previous  1 ... 11, 12, 13, 14, 15, 16, 17 ... 49  Next
Author Message
 Post subject: Re: KT120 Oddblocks
PostPosted: 15 Sep 2014, 19:27 
Offline

Joined: 08 Sep 2013, 18:43
Posts: 8
Bruce,
Great review, I'm really inspired now.....where's the "salivating" emoticon?
Good luck with VCAL, I think that's a great idea.

Sourcing for my Oddwatt KT120 is well underway, I'm running with the Antek torroidals for the PTs

I plan to run 2 timing circuits in my build.
The first timer will control an inrush limiter, ie it will short out a 50 ohm resistor in the primary side of the PT after 1 second or so.
The second timing circuit will be used to connect the B+

I suspect I'll switch the B+ as per the oddwatt schematics (ie between the rectifier and the reservoir capacitors) but before I commit, I'm wanting to consider the behaviour of the heaters and the CCS driven bias.

I'm planning to set up the B+ delay for about 30-40 seconds to allow for heating of the cathode.
Some comments I've read re the KT120's, suggest that the heaters take about 1 min to fully warm up.
Just curious as to what others have found?

Secondly, I'm curious about how and how quickly the CCS "reacts" once the B+ hits the plates.
The way I'm guessing it will work, is that (given the grids are referenced to gnd) it will self stabilize in a similar way to a cathode biased amplifier and that it will be pretty quick.
Therefore sudden application of B+ should not cause significant shock or inrush to the overall system .

Your thoughts are most welcome


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 15 Sep 2014, 20:50 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4192
Location: Arizona, USA
Hi, We set the B+ delay at 75 seconds. Certainly more than enough. I'm not sure that the inrush delay is needed. I have been using one of the prototypes for over two years and they work just fine. The tubes still test essentially the same as new. In operation if the tubes are warmed up the CCS acts virtually immediately. As soon as the tubes begin to conduct the voltage across the CCS will increase and thus control the current flow. The tubes can not conduct more than the setting for the CCS. But since they share the current it is important that both tubes be warmed up. If not, one can hog the current. This is not really harmful as it is rather brief, but not desirable. We have been using the basic design for about 8 years now with various other tubes and there does not seem to be any inrush issues or shock problems.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 21 Oct 2014, 19:49 
Offline

Joined: 26 May 2009, 18:51
Posts: 130
Location: Lilburn, Georgia USA
I thought there was a schematic in here for the KT 120 amp and power supply but I must have missed it somewhere. rparsh


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 21 Oct 2014, 20:18 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4192
Location: Arizona, USA
Hi I posted it a few times, and you can find it here: KT120 Push-Pull Tube Amplifier Schematic (Oddwatt Audio OBHO)
As well, I have attached the KT120 Odd Blocks High Output schematic below. This one may have a few small updates from the earliest ones.
Attachment:
OBHO PS May 19, 2013.jpg

Attachment:
KT120 OddBlock Main Circuit May 19, 2013.png

Good listening
Bruce


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


_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
PostPosted: 03 Jun 2015, 16:36 
Offline

Joined: 21 Sep 2014, 12:07
Posts: 33
Bruce,

The transformer p/n is "EMO-813". That number isn't coming up on the Edcor web site. The closest thing to it is the
XPWR264 . A different maker? Or was there a p/n change?

Also, this amp looks like it would be fantastic as a subwoofer amp. In your opinion, would it have enough "umph"? My thought was to build one of these after I finish my 6L6 Oddwatts. I would put a low-pass filter on the input.


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 04 Jun 2015, 12:36 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
Contact Phyllis directly. Their custom-non-public-production numbers are like that.

_________________
-= Gregg =-
* Ratings are for transistors - tubes have guidelines*
Home: GeeK ZonE
Work: Classic Valve Design


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 04 Jun 2015, 21:50 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4192
Location: Arizona, USA
Hi When I OK'd the direct sale of the OEM ones we used they put them in the line up with their usual numbering method so the XPWR264 is the same transformer. You can usually spot the ones we use as most have 10.9 volt heater windings. When you rectify it you get 12 VDC. The exception is the WPWR 083 series ones as they have 8-8.5 volt heaters and I use a regulator on them to get 6 VDC.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 05 Jun 2015, 13:33 
Offline

Joined: 21 Sep 2014, 12:07
Posts: 33
Thanks for that clarification Bruce. Any thoughts on using the KT120 amp as a subwoofer amp? You have stated before that you use subs, but are those the standard solid-state, built-in amp ones? I have 2 passive ones, but I thought I'd solicit opinions before trying out my idea.


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 05 Jun 2015, 21:34 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4192
Location: Arizona, USA
Hi, Yes the amps can be used to power subs. The subs need to be relatively efficient though. Many are in the low 80 dbw range and will not put out as much sound as you would want. I have a pair of 7 cubic foot vented subs with 15 inch drivers. They are about 93 dbw and reach flat to 20 HZ. The KT120 amps have no problem pumping out the bass with them. I would expect that any subs over about 86 dbw would be fine. I have mine set at 70HZ with a 24 db/octave slope.

good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
 Post subject: Re: KT120 Oddblocks
PostPosted: 29 Aug 2015, 16:57 
Offline

Joined: 24 Oct 2010, 07:05
Posts: 307
I'd like to clarify some info from the answers above.
Taking the values from the schematic some posts earlier, paralleled 6.8 and 14 resistors give us 273mA. On the other hand, in a post before that Bruce mentioned 290 mA. The XPWR264 from the Edcor datasheet can handle 360V@350mA. This current is for the power stage, the driver, a divider for heaters lifting... I'm in doubt that using the bridge rectifier and rather big first capacitor gives us such optimistic effectiveness for the secondary current. I estimate it in the region of 450-600mA, depending on many parameters, such as secondary and primary resistance, ESR of the capacitors, the diodes in the bridge... How come the transformer works for the circuit?


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 484 posts ]  Go to page Previous  1 ... 11, 12, 13, 14, 15, 16, 17 ... 49  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Google [Bot] and 21 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:  
cron
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