Warm Audio WA-84

[Emmathom]

@mrgrooves666
here is the capsule...

 

[Emmathom]

I would be very careful with C4 - electrolytes are in some situations a VERY Bad Idea when you connet them to an Audio Transformer

Reason - Some Audio Transformers react to a DC Current and form a Filter.

Example ; tc-electronic used a Very high quality Transformer in their old 19" Parametric EQ (Land-Line Version), that had a Bandwith 5-200KHz. when feed with a 10µF Filmcapacitor in series with a 600 Ohm Driver + loaded with 600 Ohms on the secondary and a Filmcapacitor between it and the next stage. It only took a few mA. of DC current through any of the two coils and you had a 1KHz. Bandpass filter with 80dB/Octave ...!

So a Tantalum Capacitor usually has between 0.1-1% of the Leakage Current of a good quality Electrolyte Capacitor => Far better suited as C4 ...!!!!

And before I get loads of flak - a Film Capacitor would be the absolute best as C4 - but I don't see enough space inside your microphone for that ....

One thing that can totally ruin the idea of using a Tantalum in a similar circuit - is if it hasn't got at least 33% of it's rated DC voltage across it - as this WILL make it distort the Audio (or any other AC voltage) ....

Per

Thanks Admiral-dk for your explanations about capacitors + audio transformers...
as you guessed there isn't enough space for a film capacitor as C4 (except maybe for a MSK2 wima but not sure at all) so I'm gonna leave this mic in state cause it sounds not bad at all as it is now...
often the best is the enemy of good !

I notice that a tantalum capacitor (in that case) must "see" at least 33% of it's rated volatge across it

 

[Mr. Moscode]

Wima makes some small 50 volt polypro film caps that work well in the audio path. I've used them up to 4.7 Mfd. I would stay away from 'lytics and tants. Try these first if they fit the case. Mouser or Digikey has them.
Good luck.

 

[Emmathom]

Wima makes some small 50 volt polypro film caps that work well in the audio path. I've used them up to 4.7 Mfd. I would stay away from 'lytics and tants. Try these first if they fit the case. Mouser or Digikey has them.
Good luck.

MKS2 ? or another ref ?
can find MKS2 1uF (1uF tantalum is used in the signal path) rated at 50v and 5mm height I guess... > no minimum height is 8,5mm for 5mm spacing
I'll see if it can fit...
Thank you

 

[Jim Boom]

Warm Audio uses assembly houses in the PRC. The transformer in their KM-84 repro has been made by Cinemag and shipped to Beijing for a few years now. That transformer with 6mil lams is responsible for the major part of its sound. It’s in the Iron!

 

[Emmathom]

Warm Audio uses assembly houses in the PRC. The transformer in their KM-84 repro has been made by Cinemag and shipped to Beijing for a few years now. That transformer with 6mil lams is responsible for the major part of its sound. It’s in the Iron!

ok... and ? what do you think of its sound ?

I must say that I'm not a professional nor I'm working in a big studio : I do mobile recordings of classical + baroque + tradional -brittany - music in my region and I can't afford expensive gear

Before the WA-84 I used a sE8 cardio pair wich is not bad at all ! and a sE8 omni that I replaced lately by a Griffon GMS-120 pair (does anyone of you know this brand ? it's a young guy designing his own stuff alone and his mics can be found all aound studios in the world)

Besides I build my own pre (tube / AOP / bjt) and I'm beginning building my firts own mics with Soliloqueen's flat 47
Best Regards

 

[k brown]

ok... and ? what do you think of its sound ?

I must say that I'm not a professional nor I'm working in a big studio : I do mobile recordings of classical + baroque + tradional -brittany - music in my region and I can't afford expensive gear

Before the WA-84 I used a sE8 cardio pair wich is not bad at all ! and a sE8 omni that I replaced lately by a Griffon GMS-120 pair (does anyone of you know this brand ? it's a young guy designing his own stuff alone and his mics can be found all aound studios in the world)

Besides I build my own pre (tube / AOP / bjt) and I'm beginning building my firts own mics with Soliloqueen's flat 47
Best Regards

WOW - Griffon asks a whole lotta dough for mics built around Primo EM273 electrets!
https://www.retrosonicproaudio.com/product/griffon-gmt-120-omni-condenser-microphone-pair

 

[Emmathom]

Yes k brown... fortunatly I paid my pair less than 936€ ! they are maybe a bit expensive for what you get on paper but they sound nice

 

[k brown]

Yes k brown... fortunatly I paid my pair less than 936€ ! they are maybe a bit expensive for what you get on paper but they sound nice

Would be interesting to compare them with the Line Audio Omni1, which uses the same capsule (though heavily modified).

 

[Emmathom]

Would be interesting to compare them with the Line Audio Omni1, which uses the same capsule (though heavily modified).

wow ! sooooo much mic brands around the world ! Ididn't know Line Audio and hope (lol) it doesn't sound as good as Griffon because of the price 150€ / each ! if so, I resell my Griffon tomorrow !

 

[Emmathom]

Reading this website I am totally convinced that building his own large capsule mics is a challenge (for a beginner) that can be achieved with advices & method... but for small capsules it seems to be far more complex (less less space to work in and lots of mechanical constraints) so for me no other way than buy mics from companies...

 

[Emmathom]

Would be interesting to compare them with the Line Audio Omni1, which uses the same capsule (though heavily modified).

I think I'll soon buy an Omni1 from Line Audio to compare with the Griffon GMS-120 and then decide wich one I keep and resell the other one...
I'll let you know > I'll make audio tests and post them (in about less than a month I hope so...)

PS : I edit an personnal 5mn "test audio file" wich begins by a 30sec pink noise and then samples from different styles of music : pure drums > classical cello solo > modern jazz fusion band > female jazz vocal.
I play that file on my speakers and record it with different mics, each time at same level & same distance so one can compare between them...

 

[living sounds]

Interesting.

I can't contribute anything regarding the WA-84, but somewhat related in the U87ai Neumann uses are very cheap polarized electrolytic cap for DC blocking before the transformer input. I've tested different caps in very accurate clones and found that the "bad" cap in this position sounded much better than objectively better caps (e.g. high quality film) for some reason.

 

[Mr. Moscode]

MKS2 ? or another ref ?
can find MKS2 1uF (1uF tantalum is used in the signal path) rated at 50v and 5mm height I guess... > no minimum height is 8,5mm for 5mm spacing
I'll see if it can fit...
Thank you

Your'e right MKS2B044701KOOKSSD - 4.7MFD/50v, Panasonic makes similar ones at 50 V- ECOV1H105JL -1MFD/50V - THAT P/N may be obsolete but it will find the current ones.

No tantalums allowed in!

 

[Emmathom]

@Admiral-dk I really don't see why an electrolytic such as Muse NP should differ from any other cap !
A cap in good working condition blocks DC and that's it ! or it is deficient...
and if a film cap fits in (electronicaly) then all sorts of caps will do (with different sounding results)
so I'm gonna change C4 (tantalum) for a Muse BP 1uF 50v (will maybe try also with a wima MKS2)

 

[RuudNL]

The original Neumann KM84 was introduced in the mid 60's.
Ans yes, they used tantalum capacitors!
Until now, most KM84 microphones still work without a problem...
(By the way: it will take a lot of effort to destroy a transformer winding with less than 1 mA, so even if the output capacitor gets shorted, there is not enough current to seriously harm the transformer.)

 

[Emmathom]

The original Neumann KM84 was introduced in the mid 60's.
Ans yes, they used tantalum capacitors!
Until now, most KM84 microphones still work without a problem...
(By the way: it will take a lot of effort to destroy a transformer winding with less than 1 mA, so even if the output capacitor gets shorted, there is not enough current to seriously harm the transformer.)

Hi RuudNL ! Let's not forget that that was done in the past (60's - 70's - even 80's) has been done with the component quality & disponibility of this period ! If Neumann created KM-84 today I bet it would be with a different choice of components...
Transistors, resistances, capacitors are far much better made today and you have more more choice !
The "it was better before" is a big mistake IMHO > just have a look at the quality of the last 10 years electronic boards (1-2-3-4-5 layers !) compare to bakelit's one in the 70's !
No, in any case "it was not better before" !
> I have built several Mosfet 2x50w amplifiers this past years with modern boards (2SJ102 + 2SK1058) and it sound far better than any other amps I've heard (specially commercial ones) > signal path is short and goes straight to the power Mos without any artificial or cosmetic stuff and that's the goal for me. Circuit inspired by Goldmund. Just a power ON/OFF switch. No pot. Volume controlled by the player (Foobar or whatever is your player). HR music only (my vinyls have been sampled in 24bits - 88.2kHz via ecc83 pre RIAA + ess ADC)

Back to the thread : I'm gonna change that tantalum by a Muse BP (wich is far more better) or a Wima MKS2 is enough space
Best Regards

 

[RuudNL]

But I still prefer the old Neumann KM84 (with tantalum capacitors!) over the 'modern' KM184!

 

[Admiral-dk]

I haven't ben able to answer the last few days ....

Emma - we can agree that the definition of a Capacitor is that it does NOT conduct any DC Current ....
But if you study Electronics @ any higher Level - you will see that all the Books that are used mentions that this only applies to 'an Ideal Capacitor' - Not Real ones ...!!!
If we look at Ceramic or Film Capacitors, then that is for just about all we deal with completely true - except Microphones with 1GOhm (or more) ....

I have been forced to rectify a product that had way too many Rejects @ the end of the assembly line, where changing from Electrolyte to Tantalum Capacitors reduced the Rejection Rate by more than 60% .... and the only reason that wasn't >98%, was another problem with an IC in the same part of the circuit. I found the Leakage of the Tantalum to be less than 1% of the Best Electrolyte Capacitors I tested @ the time (in 2021). The replaced where 1µF 50V Electrolytes and the much better substitues where 1µF 10V Tantalum. If you wonder about the difference in voltage rating - it has to do with how small you can get the Electrolytes ....

Ruud - the leakage current did not Harm the Transformer in anyway - as changing the Capacitors + placing the correct Resistors in the Circuit as the Manufactor of the Transformer had specified - resulted in the 5Hz-200KHz. Bandwith, without changing the Transformer.
I'm also aware og the fact that the reason this particular Transformer Model is so sensitive to DC Current - is about the small geometry of the Core-Lamination + the Bifilar winding technique used.

Per

 

[Emmathom]

So... in that case (WA-84) you DO advise to not replace the tantalum by a electrolytic, even a BP !
only a film capacitor of the same value (1uF 25v in the schematic) would be ok, right ?