My latest headphone project

[dewdude]

Hey guys,

I don't think I've posted over here before. I've always been pretty happy with the cans I own and not too worried about upgrading.

Anyway...I just wanted to share this project with you guys. I recently became a member of the tube-amp owners club, annd sadly, being the type of vintage amps they are, no headphone output.

So after some research, I came up with a little box with 8 ohm 20watt non inductive dummy loads, a 100ohm resistor feeding a double-ganged pot.

This little box did the trick. I get amazing relatively clean (clean for tubes) sound.

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[JimmyNeutron]

Hmmmmm... interseting. So you take the powered tube amp outputs and plug them into your box and the signal gets sent to your headphones? Cool. What amp are you using, and how does it sound?

Jimmy

 

[BmWr75]

Nice.....I might want to build one of those. Might you provide a bill of materials and schematic? Thanks.

 

[dewdude]

Yes. The powered output from my amps feeds in to the box. The 20watt 8ohm resistors act like a dummy load...putting the proper load on the output transformer. I'm sure this also helps to reduce the power level. The 100 ohm resistor drops the level a bit more and naturally the volume control does fine tuning. I could probably get away with removing the 100 ohm resistors...but I decided not to to avoid blowing headphones when volume is up.

Looking at my reciept, I spent about $36 at Radioshack on everything...but my power resistors somehow didn't show up (although they put them in the bag) and I bought a couple pairs of banana plugs, so id have to recalculate. However, the resistors were about $4 each and the banana plugs were about $3 a pack. So its stll probably around $36 for parts.

10 minutes to drill and mount things in the box, and it took me about an hour (after a couple brews) to wire up and make everything fit.

Ill draw a schematic after work.

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[dewdude]

As promised, here is a schematic.

This is just as it stands now. The 100K pot is actually too large of a value for the job, but it was the only double-ganged in RS's inventory. I also should of gotten a larger project box as the resistors are too close together.

If I do mod this, it will either be in to a larger box, or adding another resistor to lessen the range and make it a bit more smoother. I haven't begun to try that out, but will soon.

 

[Rex Aeterna]

what box is that? that's pretty cool. i might get that to replace the one i'm using. this is useful also for tube amps cause most tubes are transformer coupled.

i just use my headphone straight off the speaker outputs myself. no resistors or nothing. works very well on my part. powering my 600ohm 240DF and 600ohm 240 sextetts lp off the outputs. i don't own any tube amps so using resistors for impedance matching is not really needed on my part.

is that also a balanced TRS female jack? i didn't know radioshack sold those. i need to look harder next time when i go there.

 

[dewdude]

Its a project box I picked up at radioshack.

Honestly, EVERYTHING I needed to construct that is available at radioshack. The bananaplug binding posts, volume box, trs jack...it just took a bit of digging.

I suppose you could call that a balanced trs jack as its got three conductors, but in this case, its being used in a stereo configuration. Radio Shack calls it stereo.

But, 10 minutes with a power drill and an hour soldering and making things fit. I used a piece of rs's project circuit board as a bit of a terminal strip.

I did in fact, build this for a pair of console tube amps. So you're right on the what its useful for. I suppose you COULD run this on solid state, but you gotta remember, the more power you're pumping out the hotter the resistors will get. Those are 20 watt non-inductive power resistors...my tubes are around 10 watts...but if I hooked them to my 100wpc denon, cranked them up, id have a melted box and burned resistors.


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[Rex Aeterna]

i didn't know project boxes were sold at radioshack still...i think i need to take my time from now and take a look around to what they actually carry. usually when i go places i'm in and out.

i'll have a look next time i go. i know from my experience TRS jacks can be used with 4-core cabling as well. my sextetts had a 4-core balanced cable with a balanced TRS jack. the 2 negatives were soldered together as a shared ground in the jack so i'm guessing i can do the same with a female 1/4'' with bare wire at the ends and hook it directly to speaker outputs.

it's a nice job you did on the box.


EDIT: nevermind. i was bored and decided to unscrew a female cable that came as an extra extension cable for my sextetts and wired 18awg to them. tested with battery first and got signal left and right channel and to see what channel was which so i marked the left channel with black marker on the cable and it works. running it out my speaker outputs of my kenwood kr-720 receiver and man does sound great. headphones i'm using is pair of pioneer monitor 10's. all i have to do is plug the 1/4'' male jack from the headphones into the female 1/4'' jack and plug the wire ends into speaker outputs.

lucky i decided to use my kenwood instead as well cause i can barely get past 9 o'clock where before straight from the jack i had to go all way up to 1:30 to get decent volume(not that i listen loud. it just seems to be pain driving these.)

 

[dewdude]

I believe the inventory varies between shack to shack. I've got two of the close by to work, if one doesn't have what I need I'll pop over to the other one.

Doing the box was easy, somewhat. As you can see I had to cram the resistors in there, not a great idea however, since my amp doesn't work very hard, they don't have any heat build up that I can tell.

As far as four-conductor "trs", there actually is a standard for those. I've seen them used as av jacks with audio on normal stereo pins and video on an extra (with a sensor to detect if its a 4-conductor or 3-conductor plus). Wiring the two pins that would be the shield connector together would make it a 3-conductor. You have to be careful sometimes because they do make trs jacks that have internal switches...so you really need to inspect the part to determine if its 3,4 conductor or something with switches built in. My schematic shows one with switches that open upon insert, this was simply because that was the only jack symbol my cad program had in it.

One thing you didn't see in the photo was the labels I stuck on it. I got of those Brother TZ tape label printers that's PC only for $7 out of Staples a discount bin. I had no reason to own it...so I started labeling things....and did the same to the box, although I need to redo some labels.

But 10 minutes with a power drill and I had everything drilled out. They included mounting hole dimensions for everything except the trs jack, which wound up using some odd in-between size. I didn't measure distance on the binding posts..so the spacing is uneven between them and won't accept the dual/banana plugs....if I redo the box ill likely measure the distance and do it properly...but I re did my cables to use indvidual plugs...so that's not really even an issue.

But I'm proud of that little box, if for no other reason than I built it. Sure, it was the perfect solution to my problem, but it came out looking (and working) like something I bought. Can't argue with that.

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[TerryO]

I built a 10:1 voltage divider for my cans 10+ years ago and run it off the speaker terminals. I simply use the amp's volume control. The 10:1 is just right for my Sennheiser 580's and it cost me about 6-7 dollars at the time. I matched all the resistors to a bit better that 1/2%.

Best Regards,
TerryO

 

[Rex Aeterna]

my radioshack had project boxes and i bought a new cheap solder gun. last solder gun i had was only 25w and this one is 40w....man what a difference. made every quicker and easier.

i bought the biggest one they had since i have fat hands to make it easier to work with. i just reused the extra female 1/4 TRS plug,5-way gold binding posts,and banana connectors i had.

not as fancy as yours since mine is just straight wire,no leds,knobs or resistors. just bare wire wired from 1/4'' female TRS jack to the speaker terminals. it works,but i did not align the left and right speaker posts perfectly at all since i did all by eye.

i would take pic but i forgot where i pic my cam. i will try later.

 

[Rex Aeterna]

heres my crappy DIY box i told you about

i used a project box from local radioshack to make this. i used left over female 1/4'' TRS jacks i had laying around and i reused my 24k gold 5-way binding post and gold plated banana connectors.

the speaker posts ar not perfectly aligned as you can tell since i did everything by eye. i knew it wasn't gonna turn out perfect but it works. now i can plug in any headphone to be used off the speaker outputs if i want. using my Pioneer Monitor 10 on speaker outputs brings them to a new level as well which i am pretty shock cause i was only expecting more gain and that's all. it must be the power they hunger since they use aluminum voice coils instead. it only cost me 7 bucks and couple hours to make(i do things slow and take my time).

 

[Darryl M]

As promised, here is a schematic.

This is just as it stands now. The 100K pot is actually too large of a value for the job, but it was the only double-ganged in RS's inventory. I also should of gotten a larger project box as the resistors are too close together.

If I do mod this, it will either be in to a larger box, or adding another resistor to lessen the range and make it a bit more smoother. I haven't begun to try that out, but will soon.

Good evening, I've recently bought a Hughes and Kettner amp and it
Has no headphone jack out. It does have 3 different speaker outs with 3 different ohms rattling, do you think this set up you have made would work for headphones out. Thanks very much. I might add a pic of the speaker outs for better info.

 

[Darryl M]

Here are some pics of the speaker outs on my amp. Thanks for any help.

 

[WobblySam]

OK, I'll be the Debbie Downer here and take a dump on your nice project. Don't get irritated at me, blame it on impedance.
For most amps, the design goal is to have the output Z as close to zero Ohms as possible - to avoid frequency response aberrations. It's generally referred to as damping factor with respect to power amps and nominal 4 or 8 Ohm speakers.
Headphones are pretty much the same. Some HP have output Zs in the 3 to 5 Ohm range. This is OK if the Z of your headphones is 75 Ohms and up. With low Z phones (approx 32 Ohms) and especially iem/earbuds which are generally in the 16 Ohm or less range, an output Z of 1 Ohm or less is desired. It's easy to hear - the bass will get boomy or tubby and the mids can sometimes get a little tinny.

On the other hand, if it sounds good to you, forget everything I said and enjoy your system.

Cheers

 

[Darryl M]

Yes. The powered output from my amps feeds in to the box. The 20watt 8ohm resistors act like a dummy load...putting the proper load on the output transformer. I'm sure this also helps to reduce the power level. The 100 ohm resistor drops the level a bit more and naturally the volume control does fine tuning. I could probably get away with removing the 100 ohm resistors...but I decided not to to avoid blowing headphones when volume is up.

Looking at my reciept, I spent about $36 at Radioshack on everything...but my power resistors somehow didn't show up (although they put them in the bag) and I bought a couple pairs of banana plugs, so id have to recalculate. However, the resistors were about $4 each and the banana plugs were about $3 a pack. So its stll probably around $36 for parts.

10 minutes to drill and mount things in the box, and it took me about an hour (after a couple brews) to wire up and make everything fit.

Ill draw a schematic after work.

Sent from my Samsung Intercept with Tapatalk

Hi, sorry if I keep at it but I'm really interested in this, I have a 50watt tube guitar amp and it has to run through a speaker or it will over heat and melt.
It doesn't have a headphone jack so was wondering if I could run something like this plunges into my speaker outs on the amp and headphones into this set up. Thanks.

 

[AdamAnt316]

I've been running a version of Jay's headphone adapter for several years now. I built it pretty much as he did above, except that I changed the volume control to 10K after discussing it with him, and added a DPDT switch (with NO center off!) to allow switching between the headphones and my speakers without having to swap wires around. I've used it with several pairs of headphones thus far, including the following:

• AKG K240 (Sextetts and Monitors), K401 and K272 HD
• Audio-Technica AT-703, Precept PH100 and Signet EP700
• Koss Pro/4AA, Pro/4AAA+ and MV1
• Pioneer SE-30A and SE-50A
• Sennheiser HD650
• Sony MDR-V6, MDR-V600 and MDR-7506

Thus far, all have sounded quite good to me, whether powered from my Dynaco ST-70 or ST-35. The only 'issue' I encountered was with more sensitive/low impedance cans like the Sonys, having to moderate the volume control more than I did with the more power-hungry cans like the AKGs. Here's a schematic diagram of the adapter box I built:

 

[WhiteNoize]

Nice job Adam. I was lazy so when I wanted to turn my maggie 8802 into a headphone amp I went out and bought a HiFiMan HE Adapter which does exactly what you came up with.