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 18 Oct 2017, 11:44

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 26 posts ]  Go to page 1, 2, 3  Next
Author Message
PostPosted: 22 Jul 2012, 19:55 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1352
Location: US Pacific Northwest
The basis for this amp was a stack of 6AS5 power pentodes that I got for $2 each. This is a little power tube initially developed for automobile radios. As such, it's not very powerful and runs off of fairly low B+ (150v max). Typical operation is 2.2w into the output transformer with 10% THD. I was determined to improve on this performance.

Now why, you may ask, do I call this "The Amp that Never Ends". Well, I started this project about 14 months ago. It was initially going to be a directly line powered little amp with solid state rectification. I wanted to keep the cost minimal. So I put together a nice little chassis and went to work. My initial design didn't go well. You can read about it here. So I ordered a power transformer from Edcor and then tried again. Of course, in the mean time I redesigned the amp power supply to clean it up. I also prototyped the amp and decided to make some changes in the design. To make a long story short, I'm on my third power supply design and my fourth amplifier design. But I think I finally got it right.

Take a look.
Attachment:
Profile 1.jpg
The chassis is black walnut with a strip of lacewood inlay. The power switch is on the back and the standby switch is on top. I used a 6CG7 (just a 9 pin version of the 6SN7) for the driver tube. I decided that to tackle some of the distortion I would run the tube in pure UL. In spite of what the spec sheet says I was sure that I could do this and it actually paid off much better than I could have expected. The amp sounds very nice.

Here is a picture playing it's first music.
Attachment:
First Music.jpg


However, there is a reason that I called this a Micro-power UL amp. Peak output power is just 1.0W per channel into 8Ω. Input sensitivity is just a little over 1.0v peak for full power out so this can be driven by almost any line level input. I had to sacrifice power to get performance out of this little tube, but it was worth it. It's a neat little amp.

The schematic is fairly straight forward. It's a simple class A operation with a nice clean driver and no NFB except for the unbypassed driver tube cathode.
Attachment:
Schematic_amp.jpg

The power supply is a little more involved with separated filters for the two power tubes and the driver stage. This approach really helped give this little amp a really wide and deep sound stage. I was pretty impressed with the performance in this respect. Here is the power supply schematic.
Attachment:
Schematic_ps.jpg

I do however seem to be cursed with making the same mistakes over and over again. Once again I have produced a design with a lot of components to stuff inside a fairly small chassis. Take a look at the insides.
Attachment:
Insides.jpg

This amp has been a long drawn out effort. But perseverance finally payed off. The amp is low power, but with some sensitive speakers like the Fostex FN126En I think it will make a nice background amp. Maybe even for my office at work.


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


_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 25 Jul 2012, 13:26 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1352
Location: US Pacific Northwest
Wow; 103 views and not a single reply. This amp must suck.

Sorry guys, sometimes you don't know when your own baby is ugly. :(

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 25 Jul 2012, 16:08 
Offline

Joined: 05 Jun 2012, 13:10
Posts: 196
Location: Darboy, WI, USA
It looks great! Congrats on getting it to the point where you're 'done'!

-Ross

_________________
Thanks,
Ross in Wisconsin


Top
 Profile  
 
PostPosted: 25 Jul 2012, 17:17 
Offline
User avatar

Joined: 23 Jul 2010, 17:03
Posts: 54
Location: North Carolina,USA
Matt it doesnt suck!Your wood work is wonderful and your use of available realestate looks good too! Wish we could hear it. Are you gonna build speakers to match it?
David

_________________
BLACKRIVER-It's not Grandpa's amp...but it's close!


Top
 Profile  
 
PostPosted: 25 Jul 2012, 21:25 
Offline
User avatar

Joined: 05 Nov 2010, 21:07
Posts: 702
Location: South East US - Tennessee
Matt, as usual you have built a fine looking amp :thumbsup:

Simple elegance, to say the least!

:wine: Cheers!

_________________
The key to a successful build is to keep the smoke IN the circuit.
-Les

We cannot solve our problems with the same thinking we used when we created them. - Albert Einstien
_________________________________
LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board


Top
 Profile  
 
PostPosted: 26 Jul 2012, 00:51 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4714
Location: Australia
Some how I missed the early posts. I agree with the others your wood work is excellent. As an electronics engineer you would have made an top carpenter! Because you have so much under the bonnet it gets a bit crowded with a result the top plate may look a little barren. In a way, I think, this adds to the "petite" look and feel of the amp. Lets not forget there is only a 1W tiger lurking in the brush.

I thought my Paris amps were low power at 2.5W put you have gone where no man fears to tread. Good Idea splitting the final stages of the PS for better channel separation. Don's 6C33C amp splits from the power tranni (I'm listening to the amp now) and yes a detailed and wide sound stage. How easy was it for you to do that - a small RC network,done.

Good work Matt and it looks a real gem. You will hate me for saying this but "what next"?

_________________
Projects: "Tutu" - 150W Tripath T3 monoblock | "Silver Supreme" - 6L6GC-12AT7 SE UL power amp | "retro-4040" - 40W Chip amp LM3876T
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 26 Jul 2012, 17:59 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1352
Location: US Pacific Northwest
Thanks for the nice comments guys. I made my comment about the amp kind of "tongue in cheek" when no one had commented after three days. Now I feel kind of guilty about it. :blush: I really wasn't fishing for comments.
mwhouston wrote:
... "what next"?
Actually there are 9 projects in the queue right now. But the first on the list is an experiment in chassis design. The circuit is just the modified 6EM7 schematic, but the chassis will be vertical. Small footprint, sloped front, and tubes in a "stacked" configuration. The idea is to be able to put the amp on the back of a desk or on a narrow book shelf.

This is the style of chassis I want to use on my 807 triode strapped amp but I need to try it on a smaller scale before I go for the big one. If it works out half as well as I think it will, it should look great.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 26 Jul 2012, 18:10 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4714
Location: Australia
Suncalc wrote:
Thanks for the nice comments guys. I made my comment about the amp kind of "tongue in cheek" when no one had commented after three days. Now I feel kind of guilty about it. :blush: I really wasn't fishing for comments.
mwhouston wrote:
... "what next"?
Actually there are 9 projects in the queue right now. But the first on the list is an experiment in chassis design. The circuit is just the modified 6EM7 schematic, but the chassis will be vertical. Small footprint, sloped front, and tubes in a "stacked" configuration. The idea is to be able to put the amp on the back of a desk or on a narrow book shelf.

This is the style of chassis I want to use on my 807 triode strapped amp but I need to try it on a smaller scale before I go for the big one. If it works out half as well as I think it will, it should look great.

To assist "us" busy builders and share hopes, dreams and desires with others there is the Bucket List thread. Matt why not prioritize a list and post it. After a big listening afternoon and night with my friend Don's 6C33C I'm about to update mine. Guess what the entry will be?

Matt it looks like you used Edcor OPTs which ones (model) did you use?

_________________
Projects: "Tutu" - 150W Tripath T3 monoblock | "Silver Supreme" - 6L6GC-12AT7 SE UL power amp | "retro-4040" - 40W Chip amp LM3876T
Website: retro-thermionic


Top
 Profile  
 
PostPosted: 26 Jul 2012, 19:56 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1352
Location: US Pacific Northwest
mwhouston wrote:
... why not prioritize a list and post it.
Maybe I'll do just that. My projects tend to jump around a lot on the priority list but it would be good to maybe list them all out. One that I'm looking forward to is a class A triode amp with the output based on the 6336 dual triode. I got several of these tubes and only one is required for a stereo amp. I got confirmation from Brian at Edcor about the saturation current on the output transformer I want to use. I'm looking at about 8.4W per channel into the output transformer, so about 6.7W per channel at the speaker. Pure SE class A triode operation should sound really good. I've also been doing a lot of prototyping equipment lately to do quick assessments on potential designs. I should post some of that stuff as well.
mwhouston wrote:
Matt it looks like you used Edcor OPTs which ones (model) did you use?
The outputs are Edcor XSE10-8-5K just as listed on the schematic. These Edcor XSEs have kind of become my "go to" output iron for low end amps. For only $17.22 USD each (plus shipping) they are really hard to beat.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 26 Jul 2012, 22:13 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 4714
Location: Australia
"The outputs are Edcor XSE10-8-5K just as listed on the schematic. These Edcor XSEs have kind of become my "go to" output iron for low end amps. For only $17.22 USD each (plus shipping) they are really hard to beat."

Matt I agree with the selection. Where possible I try to use the XSE15-8-5K but where space is tight e.g. Paris Duo the 10W OPTs fit well. And cheap. Any ideas of what the max saturation current is?

_________________
Projects: "Tutu" - 150W Tripath T3 monoblock | "Silver Supreme" - 6L6GC-12AT7 SE UL power amp | "retro-4040" - 40W Chip amp LM3876T
Website: retro-thermionic


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 26 posts ]  Go to page 1, 2, 3  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot] and 5 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