Need P2P Tube easy project
Mar 31, 2006 at 8:29 PM Thread Starter Post #1 of 31

sbelyo

500+ Head-Fier
Joined
Jun 9, 2004
Posts
657
Likes
10
I've decided to try point to point wiring. I need an all tube project for headphones that would be easy for me to start.

I would love to try the bottlehead S.E.X. but it's got those unique output trannys and I don't need the enclosure, or any of the other little things. Pete Millett has that nice once with the sowter output trannys, but that's $200.00 for just the tranny's.

I was hoping for a proven easy OTL design. My cans are in my sig and I may add the 80 Ohm DT770's to the list as well
 
Mar 31, 2006 at 8:48 PM Post #3 of 31

sbelyo

500+ Head-Fier
Joined
Jun 9, 2004
Posts
657
Likes
10
those look cool.... I'm assuming I'll need the 16 Ohm but what wattage is good?
 
Apr 1, 2006 at 9:12 PM Post #4 of 31

sbelyo

500+ Head-Fier
Joined
Jun 9, 2004
Posts
657
Likes
10
Apr 2, 2006 at 8:55 AM Post #5 of 31

dsavitsk

MOT: ECP Audio
Joined
Aug 3, 2003
Posts
2,883
Likes
41
Quote:

Originally Posted by sbelyo
I've decided on this
http://headwize.com/projects/showfil...aarde1_prj.htm

I want to simplify the heater power supply by using a seperate filament transformer and leaving the voltage 6.3 Vac



6.3AC for the heaters should be fine. Check out a Hammond 269AX for a power transformer. Also, look around Pete Millett's site for suggestions on other output tubes. He used basically this design and a few other tubes had a lower ouput impedence, though the 6080 is not too bad. It can be noisy so you may need to try a few. Also keep in mind that the 6dj8 is going to add a lot of gain. If you have a source with a high output V, you could skip the 6dj8 all together, or, you could use a lower gain tube like another 6080. Triode Electronics has some NOS Philips 6080 tubes in stock that are about the nicest I have come across -- good sound, low microphonics. You'll also want a larger coupling cap for low impedence phones.

Other things to tweak the design: a CCS is always good, though not necessary. It may offer more clarity and less distortion at the cost of tubey sound.

It looks like a pretty simple project, though. Have fun. It is a good one to build right from the schematic and then to start tweaking. Read this thread first, though: http://www.diyaudio.com/forums/showt...threadid=30172

-d
 
Apr 3, 2006 at 4:02 PM Post #6 of 31

sbelyo

500+ Head-Fier
Joined
Jun 9, 2004
Posts
657
Likes
10
I'm looking foward to this one. I had some stuff already so I'm making a list of everything else this week. I chose the cheaper Hammond stuff first just to see if I can get it to work first. I'm going to build it on a piece of wood first, and then tweak it. Once I get it where I like it then I'll put it on a hammond chassis with a cover and maybe upgrade the Xformers and choke to the enclosed black ones. I read through that safety link. Good stuff in there, I never though to wear rubber gloves just in case!!

I had one question on tweaking before I start. It's about the C3 cap on the output. What voltage will that cap actually see? I'll start with the 220uf 100V (Elna Silmic II). I figure I could go as high as 470uf but the selection drops off. I have some 470uf blackgates that are 50V

The same goes for the high voltage supply?
 
Apr 4, 2006 at 5:09 AM Post #7 of 31

dsavitsk

MOT: ECP Audio
Joined
Aug 3, 2003
Posts
2,883
Likes
41
Quote:

Originally Posted by sbelyo
I had one question on tweaking before I start. It's about the C3 cap on the output.


The output cap, if everything goes well, won't see a very high voltage. However, you need to plan for everything not going well. For instance, if the tube arcs you could get the whole B+, which, since this thing is connected to your head, could be a real problem. I would make sure that the cap is rated at least as high as the highest voltage in the PS which means 1.414 * the unloaded transformer voltage. While caps don't generally short when they blow, they can.

Thus, the problem with OTL for low impedence headphones. You will probably spend more on caps than on ouput transformers. Solen makes a 200uF/250V cap (http://www.partsexpress.com/pe/showd...number=027-630). You could parallel 2 on each side. You could also use both sides of a BG 220 + 220 uF in parallel.

Quote:

Originally Posted by sbelyo
The same goes for the high voltage supply?


Same as above. At least as high as 1.414 * the unloaded transformer.

-d
 
Apr 4, 2006 at 5:17 AM Post #8 of 31

jbloudg20

Headphoneus Supremus
Joined
Apr 9, 2005
Posts
2,306
Likes
10
Quote:

Originally Posted by dsavitsk
6.3AC for the heaters should be fine. Check out a Hammond 269AX for a power transformer.


Be careful using the 269ax, as it is only rated for 2A on the 6.3 secondary. The 6as7g's heaters are specd at 2.5 amps.
 
Apr 4, 2006 at 5:53 AM Post #10 of 31

jbloudg20

Headphoneus Supremus
Joined
Apr 9, 2005
Posts
2,306
Likes
10
Quote:

Originally Posted by dsavitsk
oops, good catch. I used a seperate filament transformer on my 6080, and you will likely need to do the same.


Yeah I am building the Van Warrde amp balanced (as well as some other extensive mods) and I spent a long time figuring out my transformer issues
smily_headphones1.gif
 
Apr 4, 2006 at 4:16 PM Post #11 of 31

sbelyo

500+ Head-Fier
Joined
Jun 9, 2004
Posts
657
Likes
10
Yeah, I saw that was going to be a problem with the heater current so I figured on using a seperate filament XFormer rated at 6 amps. If you read the addendum on headwize one person used a 10 amp just for the filaments.

As far as the output caps go... The electrolytic in the schematic is rated at 100V and the polypro is rated at 250V bypassing the electrolytic.

I have plenty of 0.22uf polypro's rated well above 250V and I can get two types of audio caps @ 100V in 220uf and 470uf. I'm just curious If I could run a 50V electrolytic without any problems? I have some left over blackgates rated at 50V
 
Apr 4, 2006 at 5:14 PM Post #12 of 31

dsavitsk

MOT: ECP Audio
Joined
Aug 3, 2003
Posts
2,883
Likes
41
Quote:

Originally Posted by sbelyo
I have plenty of 0.22uf polypro's rated well above 250V and I can get two types of audio caps @ 100V in 220uf and 470uf. I'm just curious If I could run a 50V electrolytic without any problems? I have some left over blackgates rated at 50V


Personally, I would not trust my life to a cheap tube manufactured 40 years ago and an underrated cap just to save a few bucks. Maybe someone else will tell you different, but I won't. What you might do is ask over at DIY audio and someone with more expertise may be able to tell you whether my concern is within the realm of possibility or not.
 
Apr 4, 2006 at 6:13 PM Post #13 of 31

rickcr42

Are YOU talkin' to me?
Joined
Jun 21, 2001
Posts
13,874
Likes
14
Quote:

Personally, I would not trust my life to a cheap tube manufactured 40 years ago and an underrated cap just to save a few bucks.


I would.Ever here of NOS tubes ? ever hear of paying a premium price for superior sounding tubes made not only forty but even fifty years ago ?

there was never a problem with "old tubes" just the parts that surrounded them.Both the tubes AND the original circuits had it more right than most so called "modern" designs and if you check every single "new" VT circuit you will find it in an early amp or tube manual.

I have a pair of 6F6 tubes that whip every modern 6L6 or 6V6 I have heard and a pair of 7189 tubes that best all the EL84 types out there except for the original Mullards and they are not only OLD but pulled from old equipment so used as well

Modern passives in combination with NOS tubes is hard to beat unless you go to the "designer" tubes that cost way more than they should for not bewtter but equal sonics
 
Apr 4, 2006 at 6:25 PM Post #14 of 31

dsavitsk

MOT: ECP Audio
Joined
Aug 3, 2003
Posts
2,883
Likes
41
I think you misunderstood me. My comment had nothing to do with sonics or value, or even reliability.

I wouldn't trust my life to a new tube either. There just aren't any new manufacture 6080's (though there are new 6as7g's) and my experience has been that many of the ones available are in less than good condition.

Anyway, this isn't a new vs old concern, it is a high voltage strapped to my head concern. Others should do as they choose, but for me, I can look in a tube and see that there is not much more than a tripped over cord seperating parts at high voltage from my head, so I'd err on the side of caution.

When a tube amp is on the other side of the room, the worst case scenario is that it blows up some speakers and maybe starts a fire. But, when one is strapped to it, there is an added danger that one is on close enough proximity to touch it. Further, tubes become more fragile when they are hot, so a powered tube that is fragile strapped to ones head equals extra caution for me.
 
Apr 4, 2006 at 6:55 PM Post #15 of 31

sbelyo

500+ Head-Fier
Joined
Jun 9, 2004
Posts
657
Likes
10
I'll just stick with the spec'd values for now. Here's the schematic:
waarde2.gif

PARTS LIST (AMPLIFIER)

P1 - Potentiometer 100 k logarithmic stereo (ALPS RK-27112)
R1 - 1M ohms, 1 Watt carbon resistor
R2 - 33 ohms, 0.5 Watt metal film resistor
R3 - 47K ohms, 1 Watt carbon resistor
R4 - 820 ohms, 1 Watt carbon resistor
R5 - 4k7 ohms, 5 Watt wire-wound resistor
R6 - 3k3 ohms, 10 Watt wire-wound resistor
R7 - 10k ohms, 0.5 Watt carbon resistor
C1,C2 - 220 uF, 400 V electrolytic capacitor (Nichicon)
C3 - 220 uF, 100 V electrolytic capacitor (Nichicon)
C4 - 0.22 uF, 250 V MKT (DDR stock)
V1 - E88CC (Brimar)
V2 - 6AS7G (RCA)
waarde3.gif

PARTS LIST (POWER SUPPLY):

P2 - 1k trimpot (Piher)
R8,R9 - 6.8 Ohm, 1 Watt carbon resistor
R10,R11 - 180 Ohm, 0.25 Watt metal film resistor
C5,C6 - 22 nF, 1 kV MKT (DDR stock)
C7,C8 - 100 uF, 450V (F & T)
C9 - 1 uF, 250 V MKT (Philips)
C10 - 22000 uF, 25 V (Sprague Powerlytic)
C11 - 10 uF, 63 V (Philips)
C12 - 100 uF, 35 V (Roederstein)
IC1 - LT1084CP (Linear Technology)
D1,D2 - 1N4007
D3..D6 - P600A (50V, 6A)
T1 - 220:2 x 115 V, 30 VA isolation transformer
T2 - 220:9 V, 50 VA transformer
L1 - Inductor 10 H, 90 mA, 270 Ohm (Triad)

So a better set of questions are:

1. If something failed, what is the maximum voltage the power supply caps would see? Same goes for the output caps in the amplifier section.

2. Or are any of these capacitor values over spec'd?
 

Users who are viewing this thread

Top