DIY Audio Projects Forum
 NEW  Bruce Heran outlines the details and construction of his simple DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project.

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 02 Jul 2015, 13:15

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 11 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: 6CY7 Stereo Amp
PostPosted: 24 May 2015, 22:12 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1045
Location: US Pacific Northwest
So lately I have been working on two triode amps based on old television vertical deflection tubes. The first was my 6EM7 Vertical Amp discussed on this forum. Now I have finished the second one. It's a nice little low power stereo amp (1.3W/channel) based on the 6CY7. Here it is:
Attachment:
6CY7 Amp.jpg

Here is it undergoing testing shortly after it was completed.
Attachment:
6CY7 Amp Testing.jpg

And here is a shot of the insides.
Attachment:
6CY7 Amp Inside.jpg

The amp uses a Hammond power transformer and chokes and a pair of Edcor XSE10-8-5K output transformers. I have to say that it sounds really nice. There is just something about triode amps that nothing can beat. The circuit was first prototyped here.

As soon as I get some free time I'll type up project pages for both amps.

So what do people think?


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  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 00:02 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 1545
Location: Chilliwack, BC
Well done! :D

I love "useless TV tubes"; vertical outputs are fantastically linear. Looking great as well.

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


Top
 Profile  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 10:57 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1045
Location: US Pacific Northwest
Just a little more data on the amp. The peak clean power output is 1.3 watts RMS per channel (as determined from watching an oscilloscope). The 3dB frequency response is ≈48 Hz to 30 KHz. A plot of the end to end frequency response is included below with the lines indication the stated bandwidth of just the Edcor output transformers.
Attachment:
Frequency Response.png
This plot is from measured data taken with a signal generator (Zout=600Ω) and a fixed resistive load of 8Ω. The test setup is pictured in the first post. Below is the as built schematic (nearly).
Attachment:
Schematic - as built (small).jpg
I say nearly because after finishing the amp and checking the plate dissipations, I found that the B+ voltages were running a little high. As such I added an appropriate dropping resistor in each B+ line to get the plate dissipations back under the maximum of 5.5 watts each. You can see the modification in this picture.
Attachment:
6CY7 Amp Resistors.jpg
They may not be in the most optimal position in the power supply, but with a nice constant current SET stage it works out just fine.

I still can't get over how good and how loud this amp sounds. It handles everything from classical, to blues, to choral music equally well. And the sound stage is awesome. I will never go back to building common power supply filters for both channels ever again.


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  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 12:21 
Offline
User avatar

Joined: 02 Mar 2009, 12:41
Posts: 820
Location: Vänersborg, Sweden
There are no "useless" tubes (well, some maybe like diodes and some other). When all "normal" tubes have been tested, some experimenting with "odd" tubes can be rewarding.

_________________
Magnus

“If you don't know where you are going, any road will get you there.”
―Lewis Carroll


Top
 Profile  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 14:56 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 1545
Location: Chilliwack, BC
A little NFB will flatten that right out, if you wish to do so.

Or even local anode FB and draw the cathode of the output stage through the secondary, de-saturating it a tad will drop that low end to close to 20Hz :D

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


Top
 Profile  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 16:28 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1045
Location: US Pacific Northwest
Geek wrote:
A little NFB will flatten that right out, if you wish to do so.

Or even local anode FB and draw the cathode of the output stage through the secondary, de-saturating it a tad will drop that low end to close to 20Hz :D
Yes, but it will also greatly increase 3rd harmonic distortion which I cannot abide. Besides, it's only 4dB down at 40Hz and there is virtually nothing in music down that low. And even at 20Hz it's only ≈9dB down which is really not very much considering the variability in human hearing. I almost didn't include the frequency response characteristic because I knew that it would draw out the NFB comments.

I virtually never use NFB in my designs (with the exception of cathode degeneration) because I simply don't like the effects on the harmonic structure. I guess that's why I'm a SET (SE-UL) kind of guy. But to each, his own. :beerchug:

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


Top
 Profile  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 17:04 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1045
Location: US Pacific Northwest
Ok, there is one more thing I really like about this amp. :blush: It's one of those "tube things" that either you care about or you don't. These are all small base 9 pin miniature tubes. The heaters for these tubes are 6.3W for the 6CA4 and 4.7W each for the 6CY7s, for a total of 15.7W. This is compared to 1.9W for a typical 12A*7. What this means is that this amp REALLY GLOWS! In a dim room the glow from the amp really stands out.

You can call it the "Tube Geek" factor if you want, but I really like it.
Attachment:
Tube glow.jpg


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  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 20:09 
Offline
User avatar

Joined: 05 Nov 2010, 21:07
Posts: 689
Location: South East US - Tennessee
Nice set (pun intended), Matt! :)
I can't say that I'm surprised about the performance of the 6CY7. Many good quality amps have been made using various H-drive VTs, so why not a V-drive VT?

:thumbsup:

I do really like the layout, the cabinet AND the nice warm glow!


:beerchug:

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

Science without religion is lame, religion without science is blind. - Albert Einstien
_________________________________
LM380 Bridged Guitar Amp, Oatley K301 Phono Pre-amp, Oatley K272 Headphone Amp, Tube proto-board
Current project: 6V6 "pseudo Champ" prototype
Still to come (On hold): 6CG7/12AX7 Guitar amp (modified FireFly)


Top
 Profile  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 21:06 
Offline
User avatar

Joined: 08 Aug 2009, 03:11
Posts: 1545
Location: Chilliwack, BC
Suncalc wrote:
I virtually never use NFB in my designs (with the exception of cathode degeneration) because I simply don't like the effects on the harmonic structure. I guess that's why I'm a SET (SE-UL) kind of guy. But to each, his own. :beerchug:


One of the best reasons I've ever heard for zero NFB :beerchug:

That gorgeous pic.. into the wallpaper folder it goes :smoking:

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


Top
 Profile  
 
 Post subject: Re: 6CY7 Stereo Amp
PostPosted: 25 May 2015, 22:05 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1045
Location: US Pacific Northwest
Geek wrote:
That gorgeous pic.. into the wallpaper folder it goes :smoking:
Yeah... the 6V6 Lacewood has a nice glow as well...
Attachment:
lacewood_glow.jpg


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  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 11 posts ]  Go to page 1, 2  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: Bing [Bot], Google [Bot], Yahoo [Bot] and 4 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 / Opamp Projects :: DIY Phono Projects :: DIY Cable Projects :: HI-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy