BV12-style Transformers

[Spencerleehorton]

Just to let you guys know on some of the specs of my versions:

At 20Hz the inductance at different signal levels is as follows:

10mV rms  65H
100mV rms  155H
1V rms        350H

So mine came out pretty good.
If i got a pre order of about 5-10 units i could do some.

regards

Spence.

 

[Spencerleehorton]

if this is a serious consideration for everyone, i have a transformer company i can talk too to copy my version and make and test each one so its fully professional, if not i can wind them and give the DIY feel to each one.
Let me know if anyones serious and what price is a good price to aim for?

 

[micaddict]

if this is a serious consideration for everyone, i have a transformer company i can talk too to copy my version and make and test each one so its fully professional, if not i can wind them and give the DIY feel to each one.
Let me know if anyones serious and what price is a good price to aim for?

This feeler I will "allow" here, for the time being.  Reason one: it actually is about BV12-style transformers. Reason two: I have a weak spot for Spence.

Spence, thanks for the offer. This may be interesting. You know I admire you for taking the DIY principle of this forum very seriously. But the factory option might guarantee more consistency from one to the other. (?) In any case, if your prototype gets copied, it will still largely be  your thing. I'd like to hear the opinions from others about this.

And there's a second matter worth discussing. Correct values are one thing and it's the main reason I started this thread. But some will also want the "correct" laminations, alloys and such. Others may care less about this or even welcome improved sonics over the original. This is a tricky one, however.  E.g. the Cinemag Nickel/Cobalt CM2461 was made as an upgrade over the original BV8 and it is indeed a great transformer, with improved fidelity. But on the other hand, it lacks some of the character of the original BV8 versions. Opinions on this are welcome, too.

 

[Spencerleehorton]

Which ever way people want it, I'm pretty sure i can accommodate them, the dude who designs the stuff is seriously good at what he does and can tune the character in once the specs have been hit.
My involvement here within this forum is only ever to understand and to get something that sounds great.

 

[micaddict]

Don't ever leave, Spence!

 

[Spencerleehorton]

i dont plan on it dude!

 

[dmp]

Feels really weird to have to leave a part of the circuit out (C17) to get it to spec.

This is just so weird. If I understand the circuit correctly, leaving out the capacitor entirely completely removes the negative feedback that creates the freq response. You wouldn't even need the tertiary winding if you leave out c17.
Do you have the frequency sweep data?

Here is the freq sweep when I measured mine:
https://groupdiy.com/index.php?topic=50021.msg646101#msg646101

If you read through the whole U67 thread you see a lot of comments on the transformers / getting the authentic sound. One that stood out to me was wave and tskguy built identical mics except one had the AMI and one had the IOaudio tx, and he said "Our 2 mics are so close they could be a matched pair. "

 

[Spencerleehorton]

well i've been doing some drum recording with just 2 x U67, one with the Sowter 1304 in it and the other which has my TXF, both sound pretty damn decent, if i'm honest i would only probably add a SM57 on the snare, U47FET on kick, C12a on toms and be done with it. U67 through an 1176 blackface just to tickle it a little and i'd be sitting back being very happy with a great drum sound.
I can post up some sound clips if anyone wants?

 

[Delta Sigma]

This is just so weird. If I understand the circuit correctly, leaving out the capacitor entirely completely removes the negative feedback that creates the freq response. You wouldn't even need the tertiary winding if you leave out c17.

Still tertiary winding connected to C3.

I used 100pF, 10pF and nothing for C17. Comparing the three, no C17 felt the best to sing into but 10pF sounded the best to me. No C17 still sounded great but I was left with the feeling that it would be less versatile. I have a Beesneez K6 capsule, Hilumin Telefunken EF86 and Max's BV12.

It was mentioned here and I've seen it mentioned elsewhere that Beesneez capsules are dark. Both my CK12 and M7 capsules from them sound big and bright. I did, however, compare my M49 with M7 to an old recording of a Beesneez Arabella with their K7 capsule and the Arabella sounded darker in comparison.

My DU67 with K6 wouldn't be classified as bright, but knocking down that feedback cap certainly keeps it from sounding dark.

I should mention that I don't have a lot to compare to... I bought all Beesneez because the Canadian dollar is pretty weak making US and EU purchases hard to swallow.

Also, if removing C17 gives you the sound you're looking for then you won at DIY!

 

[micaddict]

Still tertiary winding connected to C3.

I used 100pF, 10pF and nothing for C17. Comparing the three, no C17 felt the best to sing into but 10pF sounded the best to me. No C17 still sounded great but I was left with the feeling that it would be less versatile. I have a Beesneez K6 capsule, Hilumin Telefunken EF86 and Max's BV12.

It was mentioned here and I've seen it mentioned elsewhere that Beesneez capsules are dark. Both my CK12 and M7 capsules from them sound big and bright. I did, however, compare my M49 with M7 to an old recording of a Beesneez Arabella with their K7 capsule and the Arabella sounded darker in comparison.

My DU67 with K6 wouldn't be classified as bright, but knocking down that feedback cap certainly keeps it from sounding dark.

I should mention that I don't have a lot to compare to... I bought all Beesneez because the Canadian dollar is pretty weak making US and EU purchases hard to swallow.

Also, if removing C17 gives you the sound you're looking for then you won at DIY!

I don't blame you for tweaking the thing to your liking. More power to those who brew their own. 

I will add, though, that a healthy (stock) U67 should not sound dark. The Neumann plots don't suggest this, either. (And I have an original, so I know.) Old ones that need service might be dark, but it can go the other way with old ones, too (when certain caps start to fail). A U67 does "behave" in a relatively dark way. That's the magic of the U67. The clever circuit (with all the feedback in place) sort of dynamically tames spikes/nasty transients. This may be responsible for the "darker" feel some experience.
It would seem to me that lifting a feedback cap (at least partly) kills that magic treat. It will then "just" be another tube microphone.

Also, I've asked Ben about the K6 and he said it specs identical to the Neumann. Now Max claims the same about his tranny, so that doesn't take us much further. However, people who use other brand capsules (including original Neumann) have reported the same darkness as you have.

 

[Recording Engineer]

I'd be interested in a pair, Spencerleehorton

 

[Spencerleehorton]

well so far that 1 x micaddict, 1 x TLRN and 2 x Recording Engineer. if your happy with £30 each plus shipping, msg me and we will sort out dosh and i'll start to order some bits.
having a few more people would be good but at least we can start this ball rolling.

[email protected]

regards

Spence.

 

[Spencerleehorton]

well the conclusion ive come to with both my U67's now is that one sounds pretty good, bottom end is reasonable, mid range pretty good, top end a little hyped, it has a cheap capsule in it, so changing capsule would sort it i feel.
The other i have has a capsule made by eric off this forum, i paid about £150 for it and have never really been happy with it.
When compared with my TXF and cheap capsule it doesn sound very good at all, on its own it sounds very vintage, but along side something else you can hear the muddy mid range and top end. by the way this one has the sowter 1304 in it.
So im going to do another test with taking out the sowter and use my TXF as ive wound another variation.
If the capsule comes to life its most definitely the Sowter 1304 which isnt playing ball.
I hoping it is as it then proves my TXF is better than the sowter!!! (gets big head!!!)

 

[micaddict]

well so far that 1 x micaddict, 1 x TLRN and 2 x Recording Engineer. if your happy with £30 each plus shipping, msg me and we will sort out dosh and i'll start to order some bits.
having a few more people would be good but at least we can start this ball rolling.

[email protected]

regards

Spence.

LOL I can't recall ordering one. But if one for me would help, I won't spoil the party, Spence. 

I'm in no hurry, tough, and it might be useful to explore the other option (transformer company), as well. Let's hear some feedback first.
As long as we can make it happen before Brexit becomes final ... 


Henk

 

[micaddict]

BTW are you still in contact with our Hungarian friend TLRT?
We have some more kowledgeable members in the eastern parts of Europe. Moby comes to mind, And o3misha?

Wait, here's an old tranny thread:
https://groupdiy.com/index.php?topic=52099.0

 

[emrr]

Still tertiary winding connected to C3.

I used 100pF, 10pF and nothing for C17. Comparing the three, no C17 felt the best to sing into but 10pF sounded the best to me. No C17 still sounded great but I was left with the feeling that it would be less versatile.

Based on the samples I've heard privately, all with Neumann capsules, and the TLM67 I own with Max's mod, I agree completely with TLRT's assessment.  In my own, I've removed C17 entirely, and it changes almost nothing.  I added the Neumann test position to my PSU, and confirm from measurements that no change of any significance is noted, and 15kHz response is significantly down from spec.  I suspect there are variations in production that have given dmp a transformer which is more correct in response, as he has also added the test jack and produced correct measurements. 

The AMI I heard in samples was indeed brighter and thinner than an unmodified original U67 in good condition. It was brighter than an early '80's U87 in the same test. 

I suspect my sample of Max's transformer is wound 'too well', with the tertiary passing too great a treble response thus leading to diminished treble.  I'm partway down the road to a feedback path mod on my own mic that lands it closer to the sound of the original U67 I've referenced.  I currently have it a bit brighter at a lower upper mid frequency than it should be, and the extreme top could have a bit more than it does, so I may end up with a two stage filter. 

The stock arrangement doesn't sound bad, it just seems overly dark compared to the original.  It's still well balanced and I'd not hesitate using it as-is(was).  The (very) 'bright' mod Max recommended and the TLM circuit both produce greater treble response, as a tangential comment on both the capsule and the basic pri:sec function of the transformer. 

I shudder at the thought of pulling the transformer back out of the mic, to do a swap with another model, and it would seem to need to be an exact fit to work at all.  I wouldn't consider such brain surgery without a substantial body of reports saying a consistently better version has been produced which fits properly.  If you compare pictures of Max's preamp with an original, it is very much a spot-on clone dimensionally in most aspects.   

 

[micaddict]

Based on the samples I've heard privately, all with Neumann capsules, and the TLM67 I own with Max's mod, I agree completely with TLRT's assessment.  In my own, I've removed C17 entirely, and it changes almost nothing.  I added the Neumann test position to my PSU, and confirm from measurements that no change of any significance is noted, and 15kHz response is significantly down from spec.  I suspect there are variations in production that have given dmp a transformer which is more correct in response, as he has also added the test jack and produced correct measurements. 

The AMI I heard in samples was indeed brighter and thinner than an unmodified original U67 in good condition. It was brighter than an early '80's U87 in the same test. 

I suspect my sample of Max's transformer is wound 'too well', with the tertiary passing too great a treble response thus leading to diminished treble.  I'm partway down the road to a feedback path mod on my own mic that lands it closer to the sound of the original U67 I've referenced.  I currently have it a bit brighter at a lower upper mid frequency than it should be, and the extreme top could have a bit more than it does, so I may end up with a two stage filter. 

The stock arrangement doesn't sound bad, it just seems overly dark compared to the original.  It's still well balanced and I'd not hesitate using it as-is(was).  The (very) 'bright' mod Max recommended and the TLM circuit both produce greater treble response, as a tangential comment on both the capsule and the basic pri:sec function of the transformer. 

I shudder at the thought of pulling the transformer back out of the mic, to do a swap with another model, and it would seem to need to be an exact fit to work at all.  I wouldn't consider such brain surgery without a substantial body of reports saying a consistently better version has been produced which fits properly.  If you compare pictures of Max's preamp with an original, it is very much a spot-on clone dimensionally in most aspects. 

Good post, Doug.
Thanks.

 

[dmp]

    Still tertiary winding connected to C3.

Yes, you are correct - it's been awhile since I dug into this circuit.

I suspect there are variations in production that have given dmp a transformer which is more correct in response, as he has also added the test jack and produced correct measurements.

Interesting. 
Good discussion going on here. 

 

[Spencerleehorton]

with this Sowter in there i loose top end around 12khz onwards, bottom end at 60hz drops off, so both ends it drops off.
i want to find out why its doing this as im sure Brian Sowter knows his stuff and wouldnt have designed this to happen?
ive wound anther test txf just to try out something and ive managed to make both the bottom end and top end worse by having generally more winds on and also having the Primary last doesnt work as its got the most turns so DCR is much much higher.
Im going to try out a few other TXF to see what happens to the top end and Bottom end.

 

[Khron]

For 30 quid a pop, i might be tempted to go for a couple myself, although not quite in a very huge hurry, funds are a wee bit tight right now :/

well so far that 1 x micaddict, 1 x TLRN and 2 x Recording Engineer. if your happy with £30 each plus shipping, msg me and we will sort out dosh and i'll start to order some bits.
having a few more people would be good but at least we can start this ball rolling.

[email protected]

regards

Spence.