Not guitar wiring but maybe someone can advise?

[Steve_Karl]

I have 3 sets of AKG phones that are 600 ohm and one set that is 32 ohm.
Can someone advise on building a conversion jumper that I can stick on the end of the cable to convert the 32 ohm set to 600 ohm?

Ideally it would be a small jumper cable with a Female mini on one side and a 1/4" Male on the other.
I can solder quite well and have a decent collection of heat shrink tubing.
I just don't understand electronics or the markings on resistors.
I might be able to understand a simple schematic.

If you could link to parts and say buy this and that and put it together like so then it would make it very easy for me.

Thank you!

 

[mayfly]

Hmmm.  I do know something of microphones having built and sold several Neumann U87 types and some ribbon types.  I have several thoughts:

1 - What is the reasoning with making the change from 32ohm to 600ohm?  If they really are 32ohm balanced output mics, then they would drive any audio interface you could imagine.  That's a pretty low output impedance for a mic BTW, unless they are ribbon types which usually have an (untransformed) output impedance of less than one ohm.  If that's the case, then you'd need some serious gain as well as the transformer to get some output.

2 - If you feel you really need to do it, well, the output impedance of those mics is likely coming from a transformer inside the mic body.  If that is the case, you won't be able to change the output impedance without replacing the transformer itself.  You could accomplish this with an outboard box, but for reasonable performance it would have to be an active box. That is, something with a high input impedance and a controlled 600 ohm output impedance, with something like a THAT Co. 1606 driving the output, run by a battery or phantom power.  I suppose you could get a 32/600 ohm balanced transformer from Cinemag or similar (I just looked and they don't have a standard part with that ratio), but if that's the case you'd have to ensure that it would be rated to handle the current from phantom power (if the AKGs need it) and frequency response would suffer.

3 - To help with this, can you post the model numbers of those mics?  Both the 600 ohm version and the 32 ohm version.  With that in hand I can see if there are schematics out there to better advise.

4 - Just had a thought:  are you sure those 32 Ohm mics are not actually 32k Ohm?  Balanced or Unbalanced? Unbalanced 32K seems a bit more likely.  If so, there are loads of off-the-self solutions.

 

[Steve_Karl]

I'm glad to have caught your attention with this. I was hoping you, specifically, be the one to know about something like this.

BUT - Please look one more time ... and sorry ... I should have said "headphones" and not just "phones"

@@@@@@@@@@@@@@@@@

these are headphones
NOT microphones

@@@@@@@@@@@@@@@@@

The motivation is that they're just way too loud when using my Marantz 1060.
Also, they're slightly different in frequency response to the other cans I own -
*** but I'm hoping this change won't change the frequency response? ***

My Marantz 1060 has a very subtle tone curve relative to where the volume knob is set. Straight up at 12:00 is where it begins to get more mid-range.
Between 9:00 and 11:00 it is warmer ... maybe I could call it flatter ... not sure but it's different.

With the 32 ohm phones I can't even get it turned up to 10:00 without out being way too loud.
7:00 is totally off.

Thank you for your kind attention.

Model numbers or the headphones are:

600 ohm models:
2 of these: AKG K240DF (Diverse Field) - extremely flat curve
1 of these: AKG K240M (Monitor) - slightly bass heavy with a dip in the mids ( a lil bit "boom and twiz" )

32 ohm: (much newer)
AKG K240S (Studio) - not as flat as the DF but flatter than the M

 

[mayfly]

Ah!  Well that clears up my confusion.  Seems that I triggered on '600 ohms' and 'AKG' and 'phones' to jump into Microphone land!

ok:  What you need for those 32ohm Headphones is a simple L-pad.  Some 2W metal film resistors should do it.  Give me until the end of day and I'll have a schematic.

Update: 

So what you are looking for is 600 ohm impedance presented to the amp, and (just guessing here from your description) about 6db of attenuation.  Sound about right?

 

[Steve_Karl]

Ah!  Well that clears up my confusion.  Seems that I triggered on '600 ohms' and 'AKG' and 'phones' to jump into Microphone land!

ok:  What you need for those 32ohm Headphones is a simple L-pad.  Some 2W metal film resistors should do it.  Give me until the end of day and I'll have a schematic.

Update: 

So what you are looking for is 600 ohm impedance presented to the amp, and (just guessing here from your description) about 6db of attenuation.  Sound about right?

Yes. Exactly. Let's trick the amp into seeing 600 ohms.
No hurry at all.

 

[mayfly]

Did some quick calculations.  If you really want the 600 ohm impedance presented to the amp, then you're pretty much stuck with -25db of attenuation.  If you can move on the 600 ohms to, say 150 ohms, then we can get you to -15db.

In either case, the pad is simplified to be just a resistor in series with each hot leg.  Here's some calculated values:

_Rseries	_Rinput	_Attenuation
560	592	-25
470	502	-24
390	422	-22
330	362	-21
270	302	-19
220	252	-17
180	212	-16
150	182	-15

Pick the resistor that you think balances your needs the best.

 

[Steve_Karl]

Ya know, I might be thinking about this in the wrong way.
All I really need is attenuation. The ohms really don't matter.

I suspect any stereo volume control will work. A box with a knob on it.
Would you agree?

Something like this?

https://www.newegg.com/koss-vc20-accessories/p/N82E16826263023?Description=koss%20vc20&cm_re=koss_vc20-_-26-263-023-_-Product&quicklink=true

 

[mayfly]

Well, - at $10 bucks you really can't go wrong to try it.  Then at least you can put your receiver volume into the 'sweet spot' and adjust the thumbwheel to get the level you want.

 

[Steve_Karl]

Thanks.
Sorry for making you put on your math hat.