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 27 Oct 2020, 02:12

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 2036 posts ]  Go to page Previous  1 ... 8, 9, 10, 11, 12, 13, 14 ... 204  Next
Author Message
PostPosted: 05 Jun 2009, 18:42 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4591
Location: Winnipeg, CANADA
hi cannst77,
Is you avatar photo your oddwatt build? Feel free to posts some photos of your build, I would love to see it.
Cheers,
Gio

_________________
[ 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: 06 Jun 2009, 03:52 
Offline
User avatar

Joined: 17 May 2009, 23:48
Posts: 34
Hi Gio, thanks for your interest! Here are some pics, but please bear in mind this is my first attempt at building anything. The layout was meant to be based on Bruce's OddBlocks, but the internals were stupidly designed on PCBs at the bottom of the case :eek:

Anyway, lesson learnt, and this will be redone with everything attached to the top using less wire, and more common sense :)
Attachment:
Monoblock pics-4995.jpg
Attachment:
Monoblock pics-4959.jpg
Attachment:
Monoblock pics-4930.jpg


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



Top
 Profile  
 
PostPosted: 06 Jun 2009, 05:54 
Offline

Joined: 27 Dec 2008, 04:48
Posts: 25
Location: QLD, Australia
Cannst77,

Thats a really nice job no matter what you say, well done, thanks for posting the pics, nice to see.

Ian.


Top
 Profile  
 
PostPosted: 06 Jun 2009, 15:04 
Offline
Editor
User avatar

Joined: 28 May 2008, 21:53
Posts: 4591
Location: Winnipeg, CANADA
Yes, very nice work. :up: Is the fan for the LM317? The heat sink seems like it would be large enough.
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: 07 Jun 2009, 04:47 
Offline
User avatar

Joined: 17 May 2009, 23:48
Posts: 34
Thanks for the positive comments guys :D

The fan was just a precaution really. It is blowing into the case directly at the SMPS (from a Wii power pack) and LM317, but the air leaks out the gaps in the front, so it cools everything. You are completely right though, and it is totally unnecessary and rather noisy to boot. It will not be in use on the finished amp (unless I add a speed control to turn it down). After the limited use it has got so far, the air seeping out of the front has still been cold, so I don't think anything is getting hot in there.


Top
 Profile  
 
PostPosted: 08 Jun 2009, 01:24 
Offline

Joined: 26 Oct 2008, 13:48
Posts: 70
Location: Central California coast
I'm sure it sounds as good as it looks - very nice :up:
I hope mine turn out that nice :dice:


Top
 Profile  
 
PostPosted: 12 Jun 2009, 14:15 
Offline

Joined: 12 Jun 2009, 14:03
Posts: 11
Location: Bombay, India
hey there from bombay, india :D

i built this amp (EL84 version) for my dad as a 60th birthday gift. i had prototyped a mono channel of it as a mess of circuit boards and wires, and was extremely impressed by the sound.

however, in this version, something has gone horribly wrong - the voltages check out fine, tubes light up etc etc. but there is no sound save a very loud hi-pitched sound to be heard after the tube-warm up delay.

this sound is LOUD. i guess at about 2-3 kHz - and, weirdly enough, is independent of the volume knob and whether there is an input at alll. snce it shows up on both channels, i've figure it has to be something baout the circuit and maybe the CCS. moving around wires doesn't change anything. voltages check out fine too. any ideas?


Top
 Profile  
 
PostPosted: 12 Jun 2009, 16:05 
Offline

Joined: 12 Jun 2009, 15:43
Posts: 87
Location: College Station, Texas
It sounds like exactly the same problem I had when I first started up my amp (KT77 version). The problem was that the "negative feedback" from the secondary winding of the output transformer back into the 6SL7 driver stage was actually positive feedback. It just required reversing the roles of the grounded and the "live" wires on the secondary winding on the output transformer to cure the problem. I can confirm that it was LOUD!

However, I notice that in the EL84 version of the OddWatt circuit, at http://diyaudioprojects.com/Tubes/EL84-Push-Pull, there is no analogous negative feedback, and so with that circuit, the positive-feedback problem I encountered could not arise. Are you perhaps using the KT77 circuit, with feedback, as in http://diyaudioprojects.com/Tubes/KT77- ... l-Tube-Amp?

Chris


Top
 Profile  
 
PostPosted: 12 Jun 2009, 18:32 
Offline
Project Author
User avatar

Joined: 04 Jun 2008, 20:59
Posts: 4256
Location: Arizona, USA
Hi, It is quite likely that the feedback circuit is wired backwards (if you used one). It will cause that problem. An additional thing to check is the grounding of the speaker outputs. A bad ground connection can cause similar problems. Another possibility is that the output (from the speaker terminals) is 180 out of phase with the input signals. This can occur depending on how you wired the anodes and screens on the output tubes. A possible way to check (only if you don't use feedback) is to make sure the speaker connections are not grounded at all and that there is no alternate path that the sound from the speaker side of the transformer can get back to the amp. Essentially a floating output. In any case it is virtually certain that there is some positive feedback occurring. Please write back or PM me if this doesn't solve the problem.

Hi Chris, I'm glad to see you are still out there and active on the Forum.

Good listening
Bruce

_________________
Some of my DIY Tube Amplifier Projects:


Top
 Profile  
 
PostPosted: 12 Jun 2009, 21:18 
Offline

Joined: 12 Jun 2009, 14:03
Posts: 11
Location: Bombay, India
chris, bruce, thanks for your inputs... this is the EL84 version of the oddwatt, i'm souped it up a bit with a switch to go between the stock voltage on the schematic and 200V (extra winding on the power toroidal). also, there's a couple of switches to go between pentode, triode and ultralinear as well as for the 4/8/I6 ohm output. g2 is wire with a hundred ohm 2W resistor. but there's isn't a feedback loop per se, as chris correctly pointed out, so something else is the matter here. i will try implementing your suggestions; i sure hope i can get it working soon, cause i loved the sound of this thing back when it was just a couple of boards and wires everywhere :mrgreen:

will upload pictures of my work soon. thanks again.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2036 posts ]  Go to page Previous  1 ... 8, 9, 10, 11, 12, 13, 14 ... 204  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Google [Bot] and 11 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