FEELER: M49/50 Bodies

[riggler]

I was working on a cool shockmount that is actually a yoke mount. But no promises on when that would be ready, hands are full a bit! Same deal, costs me too much just to make a pair for myself, but if many people want them then maybe we will do them. I will talk to Eric offline.

 

[riggler]

And Dany and Eric, nice work there! So exciting! I am cutting a pearl in half to be jewels for my 50's. Ha ha. She won't notice it's missing...

 

[chunger]

Hey tskguy and poctop,

I have a new low-cost 34mm capsule mount solution that has a different hole pattern than the current mount tskguy has in his hands.  Shoot me an email and I'll see if I can get you the exact hole spacing for these little buggers.

 

[tskguy]

Pics and speaking test!!!

T49 TX and My hk47 capsule. Tskguyy Riggler body and of coarse Dany's sweet boards. Let me know what you guys think....


https://dl.dropboxusercontent.com/u/55530129/m49%20test2.wav

 

[Melodeath00]

SOunds good to me. WHat tube are you using? The 5850? Is your hk47 the sort of 47/67 hybrid?

 

[tskguy]

Thanks,

I really think It sounds great to! The tube is a Raytheon 5840 sounds pretty nice and transparent.
The capsule has the same hole pattern as a 47 but uses a split backplate design more like a 67.
Eric

 

[micaddict]

Sounds very nice indeed. Effortlessly hifi and big is how I would describe the D-M49 samples I've heard sofar.
In this sample there is obvious popping on full range speakers, but that is to be expected without a screen.
Gotto love the M49.


Henk

 

[riggler]

Having met Eric in person, I can say he sounds somehow larger than life in this sample. I am really surprised at the low end! Really want to hear B versus C.

There is a certain subtle sizzle magic to the high end that is hard to put into words.

Also that T49 must be pretty good. Anyone compare the T49 to the more expensive big brother?

 

[0dbfs]

I've used both and prefer big brother. He does a bv11r which is wound for 5840's.

Cheers,
jb

 

[Melodeath00]

Is tskguy's B or C? I probably just missed it...

 

[rainton]

I also heard the popping on my full range monitors but as micaddict said this is to be expected
without a screen.

Apart from that it sounds extremely nice!
I wonder what the difference is in sound between the T49 and BV11r tranny - and is it worth the more than 300$ more than the T49...

Also - Eric - how much does one have to spend to build with the components you used - like including the PSU?

 

[micaddict]

I've used both and prefer big brother. He does a bv11r which is wound for 5840's.

Cheers,
jb

Interesting point this. How about the following pondering. I remember Klaus Heyne stating that if you turn the U67 circuit (EF86 pentode) into self bias, the sound gets considerably thinner. But with the M49  (AC701 triode circuit) the -b versus -c version (fixed versus self bias) sound difference is negligible.
The 5840 tube is a subminiature, like the AC701. But it's a 6.3 V pentode, ike the EF86. Could this be the reason why Dany's -b version seems fuller sounding than the -c version? And if so, would the -c version (wirh 5840 tube) benefit more from the BV11R tranny?

 

[Melodeath00]

Are you sure M49b versus c sound difference is negligible? As far as I've read, both FLEA and Klaus have stated there's a sound difference, and it's not described as negligible by either source.

 

[riggler]

When I get bodies, I want to experiment with M50b versus c. I know I will have a harder time with noise due to the smaller capsule.

 

[micaddict]

Are you sure M49b versus c sound difference is negligible? As far as I've read, both FLEA and Klaus have stated there's a sound difference, and it's not described as negligible by either source.

OK, negligible was not quite the proper term.
Here are some KH quotes:

"As I mentioned in a previous thread dealing with this issue:
changing fixed bias in U67 and U47 to cathode bias is detrimental to the character of these mics. They "thin out"; and while they become quieter, they also become too sterile and listless and transparent. (Yes, too transparent can be a problem: you look right through the leaves of the tree!)

That's another reason why modifications of U47 mics to run with EF14 tubes are questionable: they often include self-biasing, due to feeding a separate heater voltage to the mic. The tube's sound is already a bit anaemic, even with fixed biasing."


"An old trick in the business to salvage a noisy VF14 used to be switching the bias over to cathode bypass (self biasing).

So I did that once, just for fun. The noise was indeed much better for that particular tube, but the sound of the mic was no longer recognizeable as a U47.

The mid range texture, the thick articulation, were replaced by a crystalline, sparse, very translucent timbre that was anything but attractive.

Then I did that with a U67, just to see. Same thing.
However, with triodes it seems not to be so noticeable: Switching any AC701-equipped mic over to the so called "c" circuitry does not strike me as a step down, tonally, even though the timbre becomes slightly altered in the process.

The previous poster mentioned the low frequency phase shift associated with cathode bypass caps. That is of course no excuse not to apply this type of circuit, where applicable. Carefully choosing the right value and quality of this cap will yield phase shift-free results of high audio quality."


Also:

"Regarding preferences:

I would cull the various models and transitions into two main, desirable series, without any preferrential weight assigned between them:

- The first AC701- equipped series has a very fine and sexy sounding transformer, (not to mention the M7 capsule) which mostly makes up for the lower output and noisier specs.

- The two final series (bc, c) are another classic: lowest possible noise floor, wonderful mellowness of response without boredom, and quite universal in its application."

 

[Melodeath00]

Thanks for the reply, micaddict! Now I am wondering if my U47 with EF800 is self-bias or fixed-bias. How does one tell? I feel like I knew this a month or two ago. I'm losing my mind with all the solder fumes, I think....

 

[0dbfs]

I've used both and prefer big brother. He does a bv11r which is wound for 5840's.

Cheers,
jb

Interesting point this. How about the following pondering. I remember Klaus Heyne stating that if you turn the U67 circuit (EF86 pentode) into self bias, the sound gets considerably thinner. But with the M49  (AC701 triode circuit) the -b versus -c version (fixed versus self bias) sound difference is negligible.
The 5840 tube is a subminiature, like the AC701. But it's a 6.3 V pentode, ike the EF86. Could this be the reason why Dany's -b version seems fuller sounding than the -c version? And if so, would the -c version (wirh 5840 tube) benefit more from the BV11R tranny?

Good points to consider and I don't know the specific answers but will pay attention to my 67 and 269 builds to see if those seem to follow the convention. One thing Oliver mentioned regarding the cathode bypass cap is to use a 10uf instead of 20uf with a 5840 (at least in his conversion ckt which is more of a streamlined C version). This is most likely to move the low-end-phase shift lower regarding the NFB in the self bias implementation.

His bv11r is listed as an "historical accurate replacement" which has been optimized for 5840 use. I imagine with some slightly different specs to cater to different impedance and drive capabilities between the ac701k and 5840.

I compared two DIY 49's side by side talking into them. One with a bv11r and the other with a t49. All my 49's will have bv11r's from now on.... Unless Max starts making those too
Right now I've got one with a T49, one with a BV11r, and two in progress with BV11r's. Going to do three more with 11r's.

The difference was hard to quantify for me. It always is but I would sum it up as simply: "Better"
Not that the T49 is any slouch. I loved it before the 11r and will keep the one I have in service.

Cheers,
jb

 

[tskguy]

Hey all,

Nice to see a bit of discussion, While we are on the subject of transformers. I did a bit of digging and found out that Huafe transformers from Germany still make a suitable transformer for the 49C version. Its pricey but still less than the BV11r that Oliver is selling.
Its a HAUFE T-8094 and costs 185 Euro. I asked about shipping and haven't seen a response yet. For those that don't know Haufe built the original BV11 and this apparently is that same transformer. The dimensions and Pins allow it to fit without issue as far as I can tell.
I am most likely putting this in the C version I build in the production body. And yes the version I just built is the B.

 

[rainton]

Hey all,

Nice to see a bit of discussion, While we are on the subject of transformers. I did a bit of digging and found out that Huafe transformers from Germany still make a suitable transformer for the 49C version. Its pricey but still less than the BV11r that Oliver is selling.
Its a HAUFE T-8094 and costs 185 Euro. I asked about shipping and haven't seen a response yet. For those that don't know Haufe built the original BV11 and this apparently is that same transformer. The dimensions and Pins allow it to fit without issue as far as I can tell.
I am most likely putting this in the C version I build in the production body. And yes the version I just built is the B.

That's great to know!!

Probably this has been explained elsewhere before - but can anyone briefly explain once more the difference between fixed bias and self biasing in the b/c versions - and how that interacts with the different transformers? Or post a link to where I could find any information?
That'd be great!

 

[dmp]

Cathode (self) bias means the tube cathode connects to a resistor before ground, while the grid is nominally held at ground. The tube current creates a voltage across the cathode resistor, which biases the tube.  (M49c, M249c, C24, elam250)

Fixed bias generally means the tube cathode is connected directly to ground, and the grid is nominally held to a small negative voltage to bias the tube. The U67 is a good example.
In the M49b, the cathode is tied into the heater current circuit, which makes it appear a little more complicated. But the concept is fixed bias since the greater heater current allows a smaller resistance to be used to bias the tube, and hence changes in the tube operating point (current), have less feedback effect on the tubes operating point.