[kelvinwsy]

Just wanted to share with everyone the results of my experiments on using Tube Speaker Amp to drive Headphones. Here goes
1. Bought 2 units of ART Headtap - why 2 - wait ....
2. Load matching 10 Watt 10 ohm resistors.
3. 1/4 inch phone jacks - No TRS - Not stereo 4 pcs
4. 1 piece Female 4 pin XLR connector
4. Wires 16 ga gold plated OCC wire.
 
Amp - Audiopax Stereo 88 power amp - KT88 1 per channel, 12Ax7 driver 1 each channel. 15 watt RMS 8 ohm/4ohm
Output impedance 3.7 ohm
 
I drive the Amp with my Ibass Dx100 - Hdp R-10 (Japanese version)optical  to the Centrance Hifi M8 than 1/4 inch to RCA to Amp Rca Input
For the Power Amp as follows:
Load each speaker terminals in parallel with the 10 watt , 10 ohm resistor - Still trying to upgrade to Vishay non-inductive. Meanwhile found suitable power resistor on Ebay. Big cement covered 10Watt resistors.
Rigged up (DIY)) Banana Plugs - 16ga OCC gold wire to 1/4 inch phone jack to Input of ART Headtap - 1 per channel. ( you need 2 Headtap)
Rigged up (DIY) 1/4 inch phone jack - 1 per channel to a Female  4 pin XLR - then I plug in my Sennheiser HD800 with a balanced 4 pin XLR plug
 
Volume can be adjusted with HDP R10 or M8 My Latest expt. listening to my HD800 as I type this- HDP R10 Can also drive the Power amp on its own directly.!!!
 
I have experimented step by step so as not to take a risk and blow up my HD800 by using disposable Earbuds,B. Every step I was careful.
Even tried 1 ART HEADTAP in stereo  mode with a wire rig Left and RIght speaker output of Power AMp to 1/4 inch TRS - ie. Negative terminal of L and R channel joined Common to Sleeve of 1/4 inch TRS plug
Nothing Blew up - BUT NO SOUND - Whole Amp sound got earthed. But your amp may blow up. Mine just DID NOT
Went back to 2 ART Headtap -  Slowly set volume to Zero and slowly adjusted everything step by step Up in volume
 
SQ - A bit of grain or tube rush in the background. - I prefer the tube smoothness to Solid State and Op Amp sound in my opinion. HD800 never sounded richer in the mid bass!
 
Disclaimer - The above is MY PERSONAL Experience. If you do try anything on your own, it is entirely at our own risk and choice. Tube Amps are High Voltage and HOT HOT.
I am not responsible for anyone's effort or trials. The above is my tests on my OWN equipment at MY OWN RISK ENTIRELY.
 
 
Happy Listening

 

[zilch0md]

Thanks for this detailed report - it sounds as if you are a scientist at heart.  Good work!

 

[davidsh]

^Question is whether you need the 10 ohm resistors? It might be wise to measure the load of the headtap, perhaps it might be around 8 ohm by itself.
Looking at schematics it seems to me the headtap just put resistors in series to decrease output, and a resistor between + and ground to keep the speaker load low.

The series resistor could likely explain the richer mid-bass too.

 

[kelvinwsy]

You guys are right there. I opened up at Headtap to check out the PCB . Will measure it again. But the advantage of the 10 Ohm Parallel resistor is that if I do anything STUPID, the HD800 will not blow up or if the AMP shorts a TUBE. The 10 ohm parallel circuit takes a lot of the output current away from the Headtap. I have read everything on this thread. I may still build a ROBINETTE resistor network but the Headtap was on offer at 35bucks. So safety and convenience first and foremost!
 
BTW I have also built a DIY harness - 2 rca to 1 female 4 pin XLR cable - `hook up my HD800 balanced cable to my other ACTIVE 45 tube Preamp - damn thing sounds wonderful but NO Headphone jacks. Fantastic sound quality. A bit like a 45 tube version of the Sonett. It is not really a balanced amp but close enough. I am in the process of customizing an active TUBE Buffer for the HD800 - still deciding on the Tube configuration. (I measured and made sure ZERO DC Voltage! did not want to fry my HD800s- 12dba gain - volume is about 1.30am - I know a bit too low gain)
That is why I am customizing another Tube buffer stage to step up the gain.
 
Happy Listening

 

[Chris J]

The chances of hearing noise with that much gain are somewhat high...

Guaranteed you will hear noise, noise, and more noise! :eek:

 

[Gary in MD]

Folks:
 
I figured I'd give you an update on the Nikko NA-890 after about a month.  I still love the thing, most of the time.  I tried it without the resistors in the chain (I just connected the tap into the input jacks of the resistor box where the speaker wire was already attached) and it was too hard to control volume, plus there was a bit of added harshness.  So I connected back to the other side, bringing the resistors back into the loop.  Much better.
 
I have been getting some static-like noise periodically, but noticed that if I turn the amp off and let it rest for a few hours or a day, the noise goes away the next time I turn it on... until it comes back a few days later when I've left the amp on for the entire time.  Moral of the story:  turn off the amp when I'm not using it.  It's old, and like all of us old farts, it needs to rest. 
 
I suppose I might make it feel younger/better if I open it up and get rid of some of the dust in the box, but I'm afraid if I open it and try to clean it I'll break something.  Then I'd have to send it to one of you amp builders for refurbishment (and playing around with it, of course).  And I'm not ready to do that yet, sorry. 

 

[zilch0md]

Good one - Don't fix what ain't broken!  

 

[potterma]

  Folks:
 
I figured I'd give you an update on the Nikko NA-890 after about a month.  I still love the thing, most of the time.  I tried it without the resistors in the chain (I just connected the tap into the input jacks of the resistor box where the speaker wire was already attached) and it was too hard to control volume, plus there was a bit of added harshness.  So I connected back to the other side, bringing the resistors back into the loop.  Much better.
 
I have been getting some static-like noise periodically, but noticed that if I turn the amp off and let it rest for a few hours or a day, the noise goes away the next time I turn it on... until it comes back a few days later when I've left the amp on for the entire time.  Moral of the story:  turn off the amp when I'm not using it.  It's old, and like all of us old farts, it needs to rest. 
 
I suppose I might make it feel younger/better if I open it up and get rid of some of the dust in the box, but I'm afraid if I open it and try to clean it I'll break something.  Then I'd have to send it to one of you amp builders for refurbishment (and playing around with it, of course).  And I'm not ready to do that yet, sorry. 

Glad you are enjoying it, Gary.  
 
When the time comes, you'll probably want to have all the contacts cleaned and all of the electrolytic caps replaced, at a minimum...  Your crackling noise is most likely contacts that need to be cleaned (switches, relays, pots).
 
In the mean time, treat her gently!

 

[preproman]

Has anyone heard the Odyssey Kismet?

 

[robrob]

Here's the layout diagrams for a basic headphone interface:

 

Basic Speaker Amp to Headphone Adapter - Single Ended TRS

This type of adapter is only for amplifiers that have their negative speaker terminals tied together (common ground).
 

Basic Speaker Amp to Headphone Adapter - Balanced Output XLR 4-Pin

This adapter will work with single-ended and balanced output speaker amplifiers.

 

[zilch0md]

^ Those are really nice diagrams!

 

[robrob]

Thanks zilch, they were made with the easy to use freeware DIYLC (DIY Layout Creator) I have used it to detail amplifier mods like this 5e3 Fender Deluxe cascaded channel modification:
 

 
I'm working on a layout diagram for the Robinette Box to help with construction.

 

[Velomane]

  Thanks zilch, they were made with the easy to use freeware DIYLC (DIY Layout Creator) I have used it to detail amplifier mods like this 5e3 Fender Deluxe cascaded channel modification:
 
 
I'm working on a layout diagram for the Robinette Box to help with construction.

That would be a most welcome layout. Thanks for taking the time, it is much appreciated.

 

[potterma]

 

Spoiler: Warning: Spoiler!

 

 
I'm working on a layout diagram for the Robinette Box to help with construction.

 

Looks quite useful.  Gonna have to give it a try.  Thanks for the link!

 

[robrob]

potterma, you won't get a true Marshall type high gain stage because the of the 5e3's cathodyne phase inverter but you can still get a nice tube overdrive with the master volume down low. It's like having a true tube overdrive pedal built in. I detail the modification here: http://robrobinette.com/5e3_Cascade.htm
 
The DIYLC layout file is available here: http://images/Guitar/5E3P_Build/5e3p_Tube_Guitar_Amplifier_Cascade_Inputs_Coax.diy
 
The Standard 5e3 Fender Deluxe tube amp DIYLC layout file is here: http://images/Guitar/5E3P_Build/5e3_Tube_Guitar_Amplifier.diy