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New project. Valve headphone amplifier.

 

Re: New project. Valve headphone amplifier.

Post by Techmate » Wed Jan 29, 2014 12:50 am

Top stuff!! :aad
All that's missing now is an uber fancy case and a £600 price tag - you'll be a millionaire by the end of the year.
I reckon I'll be making one of these amps myself, I like listening to music on headphones, and a little valve amp glowing away will be brilliant!
Thanks for sharing.
John

 
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Re: New project. Valve headphone amplifier.

Post by crackle » Wed Jan 29, 2014 9:54 am

I bet it makes you jump with all that silence and a music track starts suddenly. :qq1
Well done, nice little project for others to follow. :aad

Mike

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Wed Jan 29, 2014 10:39 am

Crackle wrote:I bet it makes you jump with all that silence and a music track starts suddenly. :qq1

Yes!!

To be honest, when I first plugged the headphones in I thought there was no output because I expected some noise. However touching the input sockets proved it was OK. Playing various CD's, especially old recordings originally in analogue shows the hiss on the recording although this is only slight in many cases. I'll put it through it's paces over the next few days. I have some really good Dave Brubeck jazz recordings which will show what sort of dynamic range it has.

The rebuild will start when I have a proper chassis (quite soon I hope) but in the meantime I'll just enjoy using it. It's quieter than my regular Hi Fi amp (1973 Akai 5200).


Rich

 
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Re: New project. Valve headphone amplifier.

Post by Refugee » Wed Jan 29, 2014 12:08 pm

I have been using a CD source with a variable output and I can hear noise from the CD player.
I have to put a resistive divider in the line and turn the CD up to drown it out.

 
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Re: New project. Valve headphone amplifier.

Post by rob t » Wed Jan 29, 2014 12:31 pm

Refugee wrote:I have been using a CD source with a variable output and I can hear noise from the CD player.
I have to put a resistive divider in the line and turn the CD up to drown it out.

Here in lies a problem if you build/ buy a high quality transparent amp and speakers , you WILL start to notice faults with source components which poorer quality stuff would mask .(a slippery road to audio phoolery)
Rob T

 
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Re: New project. Valve headphone amplifier.

Post by Refugee » Wed Jan 29, 2014 12:48 pm

I can't be on that slope :bbc
I got the mono blocks out of a skip on a very rainy day for free and the rain had seen to the valve numbers.
I know what the numbers were :aaj :aak

 
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Re: New project. Valve headphone amplifier.

Post by Michael Watterson » Wed Jan 29, 2014 2:49 pm

Refugee wrote:I have been using a CD source with a variable output and I can hear noise from the CD player.
I have to put a resistive divider in the line and turn the CD up to drown it out.


That sounds like an earphone output, not a line output.

 
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Re: New project. Valve headphone amplifier.

Post by Refugee » Wed Jan 29, 2014 2:56 pm

The DC player does not have a line out so I just have to load it up with 30 ohms.

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Thu Jan 30, 2014 7:47 pm

sideband wrote:I have some really good Dave Brubeck jazz recordings which will show what sort of dynamic range it has.


...except that my son has got my Brubeck CD so I then remembered another that has an exceptional dynamic range....the original London cast recording of Phantom of the Opera from about 1987 I think.

Well I wasn't disappointed.... rumbling bass from the organ and cymbals equally audible...very impressed. It also shows up bad recordings.....I've noticed that a lot of CD's from the 90's seem to be over processed. Just out of interest I tried one of those 'That's what I call Music' CD's. Well it's not what I call music and definitely not to listen to on headphones. Hard bass (like someone thumping the side of a cardboard box) and scratchy treble and even digital noise in some places...like a rapid popping noise....horrible.

No I'm not becoming an audiophool :aae but I do know Hi Fi and the difference between good and bad recordings. This amp shows up both.


Rich.

 
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Re: New project. Valve headphone amplifier.

Post by Michael Watterson » Thu Jan 30, 2014 8:30 pm

If I had a pair of sensible ears ...

http://www.head-fi.org/t/51288/dsps-con ... o-binaural
On Linux
http://sourceforge.net/projects/bs2b/

Why when so much music is listened to on earphones don't they do Binaural mixes and offer both? Stereo is only really good on speakers and oddly though I have only one really usable ear I can appreciate good stereo on Speakers rather than mono, but on headphones mixing to mono works best for me as the left ear is too deaf even for best hearing aid.

You know your hearing is getting bad when 1927 2K + 2K moving Iron mono sounds better than stereo earbuds ... but maybe they really do?

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Fri Jan 31, 2014 3:03 pm

After a considerable amount of searching on the web, I found the original design. I think it's probably the guy who designed it and subsequently submitted the article to Elektor.

However this must be the original and is freely available (whereas Elektor charge)!

He includes some test results and curves.



Rich

 
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Re: New project. Valve headphone amplifier.

Post by Michael Watterson » Fri Jan 31, 2014 3:20 pm

Excellent. I wonder did Elektor pay much? I suppose Ed Dinning knows Elektor's payment terms :)

I will try a version with cheap Russian or Chinese valves and Shaver Transformer for HT and 6V or 12V for heater. Perhaps even trying PCB via toner transfer to copper.

P.S.
Printing at 108% to PDFCreator in B&W makes a nice version for Kindle DX.

 
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Re: New project. Valve headphone amplifier.

Post by Terrykc » Fri Jan 31, 2014 3:26 pm

Note the Elector copyright mark on all the PCB layouts (and visible in one of the photographs).

Also the circuit diagrams are drawn in Elector's distinctive style, suggesting that this is a reprint of the Elector article, rather than the original design that preceded it ...

 
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Re: New project. Valve headphone amplifier.

Post by Michael Watterson » Fri Jan 31, 2014 3:55 pm

And Elektor on the footer. :)

 
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Re: New project. Valve headphone amplifier.

Post by Terrykc » Fri Jan 31, 2014 3:58 pm

Michael Watterson wrote:And Elektor on the footer. :)

Oh yes ...!

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Fri Jan 31, 2014 7:49 pm

If anyone is looking back over this thread and wonders where the circuits have gone....basically to avoid any possible copywrite issues I've removed them and provided a link instead. Maybe overkill but ....you never know who may be watching!



Rich

 
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Re: New project. Valve headphone amplifier.

Post by Mkstevo » Sun Feb 16, 2014 8:08 pm

I built a valve/transistor hybrid headphone amplifier inspired by an Elektor article. The original design used darlington transistors as the output devices, I used standard BC547's connected as darlingtons. I also re-worked some component values to match what I had to hand and to fit on a single sided PCB.

The results were far better than I expected, the sound quality is superb for such a simple design.

The reason I built the hybrid over the full valve unit was that the hybrid is entirely powered from 12V. No high voltage near my expensive headphones! Well worth a build in my opinion.

Elektor's 2009 July/August issue featured the design I tweaked.

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Mon Apr 27, 2015 11:24 pm

I've made a start on the re-build.....watch this space!

 
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Re: New project. Valve headphone amplifier.

Post by Doz » Wed Apr 29, 2015 8:12 am

I've used Bluebell many times. They can get the whole range of Hammond enclosures and transformers.

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Sat May 02, 2015 11:56 pm

I've managed to find a nice chassis to do the rebuild. Haven't started on the metal bashing yet. However when I helped clear out a retired engineer's workshop last year and everything was put in boxes, I found some genuine vintage style tag board so I decided to go down the 'Mullard' route and rebuild it using tag boards. I like to draft out a layout on paper first and this proved quite easy seeing as you only have to work out one channel and then just copy it for the second. One long tag board was enough to take all but a few of the main amplifier components with a smaller one to be used for the power supply.

This evening, I managed to complete the bulk of the amplifier tag board with just a few peripheral components to directly wire to the valveholders. This is what it looks like so far. I've made some wire links on the back of the tag board and also fitted a couple of resistors there as well. Much neater than straggling components across the top of the board. When the chassis work is done, the tag boards will be mounted on plastic stand-offs. As in the test version, there will be a single bus-bar for earthing to the chassis. I suppose it would look neater if using all the same style resistors. However in the true style of home construction, I use what's in the spares boxes within reason
Attachments
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Re: New project. Valve headphone amplifier.

Post by sideband » Sun May 03, 2015 11:15 pm

Tonight I rebuilt the power supply on a second tag board. Once again I drafted out a copy of the layout on paper first...actually I did two layouts in case it was easier to use four separate diodes rather than the bridge. In the end I found it easier to use the bridge so I retained the BY179. So now I have the completed rebuilt power supply and most of the amplifier ready to install into the chassis. Next job is to do the chassis bashing. I've shown how I intend to install the tag boards.....exact positions to be finalised.
Attachments
jsw_sam_2108.jpg
Completed power supply
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jsw_sam_2110.jpg
A few links underneath...neater than strapping wires across the component side
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jsw_sam_2112.jpg
Both boards
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jsw_sam_2114.jpg
The chassis that will be used.
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jsw_sam_2115.jpg
Both boards in their approximate positions.
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jsw_sam_2116.jpg
...and from the side.
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Re: New project. Valve headphone amplifier.

Post by sideband » Tue May 05, 2015 10:47 pm

Some chassis bashing has been completed. Valve-holder holes punched out, holes drilled for mains transformer and plastic stand-off mounts for tag-boards. Still some holes to mark and drill for headphone sockets, input sockets, mains lead and on/off switch. Now that the stand-off mounts are fitted, I'm not sure about them and may change to more traditional nuts, bolts and spacers. Here are some pictures of progress so far.
Attachments
js640_SAM_2122.jpg
Holes for valve-holders, transformer and stand-offs
js640_SAM_2119.jpg
Valve-holders just dropped into place. Best orientation to still be found.
js640_SAM_2120.jpg
Mains transformer placed in position
js640_SAM_2123.jpg
Position of the boards underneath
js640_SAM_2124.jpg
...and from the other side.
js640_SAM_2121.jpg
With a couple of ECC82's

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Wed May 13, 2015 11:13 pm

Over the last week, I've been busy rebuilding and have now more or less finished it. I completed the bulk of the rebuild on Sunday and managed to try it out. It works as well as the prototype....in fact slightly better which I'll come to in a moment. One slight addition to the prototype....I added the DC heater supply. Search as I might, I couldn't find any more tagboard so unfortunately and going against the traditional construction, I had to resort to a small piece of veroboard for the 12.6V DC supply and also (even worse) a solid state regulator....sorry.

Now the prototype worked well and I stated at the time that there was no hum. Well in fact there was but only when I used my super-duper Philips headphones. The bass response is claimed to go down to 35Hz on those and a slight hum was definitely present on the output. Adding the DC heater supply completely cured it so that's why I added it to this final build. All I have left to do is tidy up the mains input wiring and add a switch. Some sort of enclosure would finish it off nicely but I'm not too bothered.

So how does it sound? Absolutely wonderful is a good description! I put it through it's paces tonight for around three hours with a variety of music from classical to Pink Floyd...and talking of Pink Floyd, 'Welcome To The Machine' from Wish You Were Here sounds incredible with bass that shakes your head....! Classical is clear and crisp to the point where you can almost hear the players of wind instruments taking a breath. Remember 'Stranger on the Shore' by Acker Bilk? You can hear the air blowing through the clarinet....and there really is no noise in the headphones (that I can hear) when there is no input even with the volume control at max. It gives far superior results to the headphone output of the Akai Hi Fi amplifier (that has a low hum and hiss). Probably the most satisfying feature is that it cost less than a fiver to build. Apart from the phono input sockets and the 12 volt regulator, everything else came from the spares boxes. I'd love to compare it with one of the expensive £400 models.
Attachments
js640_SAM_2125.jpg
All modules fitted and wired. The 12.6V heater supply is top right.
js640_SAM_2126.jpg
Close-up of the additional 12.6V supply.
js640_SAM_2127.jpg
The regulator is bolted to the chassis with a mica insulator and a plastic bush for the screw.
js640_SAM_2128.jpg
The main 200V supply
js640_SAM_2129.jpg
The input wiring
js640_SAM_2131.jpg
Top view
js640_SAM_2136.jpg
Working.....

 
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Re: New project. Valve headphone amplifier.

Post by crustytv » Wed May 13, 2015 11:56 pm

Fantastic work Rich and it looks as good as it obviously sounds too. Its been a good thread to follow, I'm not one for home-brew but its projects like yours that almost tip me to the point changing that stance.

 
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Re: New project. Valve headphone amplifier.

Post by sideband » Thu May 14, 2015 9:27 am

CrustyTV wrote:I'm not one for home-brew but its projects like yours that almost tip me to the point changing that stance.


Every-so-often I get the 'building bug'....probably a throw-back from my early years of building radio's when I really used to get a buzz from building something from scratch. It's over 40 years since I built a valve project (not counting the Minimalist Radio) and when this circuit appeared, I felt it was a worthwhile use for a couple of the many ECC82's I have kicking about. Also being output transformerless made it more appealing. I am truly amazed at the quality of this little amp. It has a fantastic dynamic range and puts the headphone output on the main amplifier to shame and is also better than the headphone out on the CD player. Triodes at their best....

I'll tidy up the mains input wiring next and might even try to find a cover for the transformer. Then just fit the bottom enclosure so it's all hidden away from wandering fingers....

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