[Dawnrazor]

Need someone's help, please. For a couple of years now I've been wanting to listen to my headphones from the speaker outputs on my vintage int. amp. First I want to state a fact & it's not easy for me to admit this, I don't understand technical stuff. I'm not good at assembling electronics, I'm not a handy man and it's not about learning how to do these things. I'm in my sixties and know by now that there are some things I'm just not able to understand let alone do. It was the same in school with math. Never got around solving the understanding part past basic math.

So, I'm asking if anyone on this thread is willing to help me out, first by telling me if this "Tap Monitor Level Converter" is safe & worth getting : https://www.parts-express.com/open-...hone-tap-monitor-level-converter--86-245-1116

My vintage amp is a Sansui AU-719 & these are it's specs (from HiFi Engine site) :

Specifications

Power output: 90 watts per channel into 8Ω (stereo)

Frequency response: 10Hz to 20kHz

Total harmonic distortion: 0.015%

Damping factor: 110

Input sensitivity: 2.5mV (MM), 200mV (line)

Signal to noise ratio: 88dB (MM), 100dB (line)

Channel separation: 65dB (MM), 70dB (line)

Output: 200mV (line)

Speaker load impedance: 8Ω (minimum)

Dimensions: 430 x 168 x 395mm

Weight: 16kg

Year: 1980

My headphones : HD600 & HD650, 300 ohms; Grado PS1000 (original), 32 ohms & AKG K340, 400 ohms.


If it's not a safe or good converter, would someone be willing to build an L pad for me that would be safe for my headphones & amplifier. I will pay for all of the parts/ material + your time & of course the s&h.
If someone would be willing to do this please message me.

Thank you,

Bob Gosselin
Milton, NS
Canada

Great. I buy FOUR of these and now they are on sale! Thanks world!

Anyhow love mine but it looks like you are staying with the head phone jack

 

[Mheat122134]

https://www.aliexpress.com/item/Mus...eb57-46f1-bacd-1c2633bf9c07&priceBeautifyAB=0

Has anyone tried something like this for tube amps before? Could someone let me know if it would be safe or not? Thanks.

 

[Nik74]

this is very interesting for me too. Can anyone explain the technicalities of such an application in a way that those of us with less technical knowledge could understand?

 

[Armaegis]

https://www.aliexpress.com/item/Mus...eb57-46f1-bacd-1c2633bf9c07&priceBeautifyAB=0

Has anyone tried something like this for tube amps before? Could someone let me know if it would be safe or not? Thanks.

Without being able to see the trace lines, my guess is that it's just an L-pad to trim down the level enough for headphone use while maintaining a constant load for the amp. My concerns:
- You're still connecting a 4-wire connection down to 3-wire. While the majority of amps have a shared ground on the negatives meaning they are "effective" 3 wire and this is ok... there's a non-zero chance that your amp will go boom
- Most L-pads are simply 4 resistors (2 per side). I count 14 here (5 per side, 4 in the middle). Note that the side resistors are all the same (51ohm). My guess here is that they are running them in parallel to get the equivalent 10 ohm load. This is because: a) more resistors looks "cool", and b) it's cheaper to run a bunch of smaller wattage resistors instead of one bigger one (which is typically the preferred method; debate sound quality another time)

Even though considering the materials this is cheaper than what I could build on my own, this would get a hard pass from me.

If you're a newbie and don't understand anything that I said above, please take a step back and stop thinking about plugging headphones into speaker amps before you blow something up. This is coming from a guy who used to run monoblock amps for his headphones.

 

[Mheat122134]

Without being able to see the trace lines, my guess is that it's just an L-pad to trim down the level enough for headphone use while maintaining a constant load for the amp. My concerns:
- You're still connecting a 4-wire connection down to 3-wire. While the majority of amps have a shared ground on the negatives meaning they are "effective" 3 wire and this is ok... there's a non-zero chance that your amp will go boom
- Most L-pads are simply 4 resistors (2 per side). I count 14 here (5 per side, 4 in the middle). Note that the side resistors are all the same (51ohm). My guess here is that they are running them in parallel to get the equivalent 10 ohm load. This is because: a) more resistors looks "cool", and b) it's cheaper to run a bunch of smaller wattage resistors instead of one bigger one (which is typically the preferred method; debate sound quality another time)

Even though considering the materials this is cheaper than what I could build on my own, this would get a hard pass from me.

If you're a newbie and don't understand anything that I said above, please take a step back and stop thinking about plugging headphones into speaker amps before you blow something up. This is coming from a guy who used to run monoblock amps for his headphones.

Thanks for the response. Though if I can ensure the chain is grounded would such a device pose no other inherent risk? I've been thinking of connecting my Beyerdynamic T1's to a 10W 4/8ohm tube amp, though admittedly I have not done something like this before and don't have the knowledge.

 

[Armaegis]

If you're absolutely certain that your amp has a shared ground on the negative terminals, then you should be ok assuming that the box is wired correctly.
At least the Beyer has a high impedance rating so the less-than-optimal output Z of the box is mitigated somewhat.

 

[kelvinwsy]

Just my five cents worth... Safe ... from my experience YMMV !! of course
I use 2 of the APPJ Tube amp adapter (8watt max) connected to my monobloc Audionote 300b to drive my HD800 and HE560.
2nd photo shows a vishay 25watt 10 ohm resistor i added to reduce the gain further ( ref to Robinette amp resistor network - google it / or on Headfi.org)
3rd picture shows the other hookup i use with my 15watt Audiopax Stereo88 KT88 amp ( for my Turntable system)
APPJ has 3.5mm jack - i can run balanced to my FINAL AUDIO Sonorous VI
Good luck

 

[Mheat122134]

If you're absolutely certain that your amp has a shared ground on the negative terminals, then you should be ok assuming that the box is wired correctly.
At least the Beyer has a high impedance rating so the less-than-optimal output Z of the box is mitigated somewhat.

Pardon the dumb question, but what are the concerns of a direct connection to the terminals?

 

[Mheat122134]

Just my five cents worth... Safe ... from my experience YMMV !! of course
I use 2 of the APPJ Tube amp adapter (8watt max) connected to my monobloc Audionote 300b to drive my HD800 and HE560.
2nd photo shows a vishay 25watt 10 ohm resistor i added to reduce the gain further ( ref to Robinette amp resistor network - google it / or on Headfi.org)
3rd picture shows the other hookup i use with my 15watt Audiopax Stereo88 KT88 amp ( for my Turntable system)
APPJ has 3.5mm jack - i can run balanced to my FINAL AUDIO Sonorous VI
Good luck

What images are you referring to?

 

[kelvinwsy]

here we go

 

[kelvinwsy]

What images are you referring to?

 

[kelvinwsy]

 

[Armaegis]

Wow, tinfoil and duct tape... I'd suggest just buying a used shielded mic cable off craiglist and chop that up to make your wiring. It'd be significantly cleaner, and then you wouldn't have a pile of conductive foil near your amp terminals. Granted, you don't even need that homemade shielding in the first place.

 

[Armaegis]

Pardon the dumb question, but what are the concerns of a direct connection to the terminals?

A vague question, but here's a rundown...
1) Speaker amps have a ton of power relative to headphone amps. If you aren't careful or accidentally bump it, you'll fry your headphones.
2) a speaker amp might have a dc offset which is insignificant to speakers but too high for headphones
3) Speaker amps have four terminals: +L/-L and +R/-R. Headphones typically only have +L/+R/ground. If your adapter takes you from 4 wires down to 3, you better be sure that your amp negative terminals happen to both be ground, otherwise you're shorting two live wire together and that's bad news. Shorting them together and also shorting your headphones to it is a good way to ruin all your toys.

I have mentioned numerous times on this forum and on this thread very specifically that the Robinette box is a dangerous design because it lets people short out the negative terminals with a switch. If you're doing down the path of connecting headphones to speaker amps, then rewire your headphones with a balanced connector (typically a 4-pin XLR) so you'll only ever go from 4-wire to 4-wire. You'll remove a significant amount of risk that way.

 

[kelvinwsy]

Wow, tinfoil and duct tape... I'd suggest just buying a used shielded mic cable off craiglist and chop that up to make your wiring. It'd be significantly cleaner, and then you wouldn't have a pile of conductive foil near your amp terminals. Granted, you don't even need that homemade shielding in the first place.

18ga soft tempered silver in teflon tube underneath foil shield! u be surorised what magnetic flux influence there is frm those bid tube amps. ueh star.quqd Canare cable is one option but.i enjoy silver cable tonal effect