wlinart

BV11 ratio?
« on: August 13, 2018, 05:44:36 AM »
Hi All,

There are a lot of posts about the BV11 transformer, and a lot of confusion. Does the BV11 have a ratio of 7:1 or 10:1?
I mean: look at the different "clones" of the BV11 and there are some which use the 10:1, and some which use the 7:1? Are they both correct? Where there different versions?
Here is a list i compiled of the available options with their ratios:
AMI BV11a/r: 10:1
AMI T49: 10:1
Haufe T-8094: 7:1
Haufe T-8974: 10:1 (both haufe transformers are named as BV11 online? So that may be confirming the 2 versions?)
Cinemag CM-6511: 7:1
Beesneez B-BV11: 10:1
Fab V11: 10:1
Moby bv11 (groupdiy): ? Not sure. EDIT: confirmed to be 10:1
Advanced audio BV11: 5:1 (so probably got nothing to do with the real bv11)

Here is a discussion where Ericbazaar calculated that 7:1 would be the best choice: https://groupdiy.com/index.php?topic=66263.0, but why do most clones have a 10:1 ratio then?
Also in this thread there is mentioned that the BV11 is 7:1: https://groupdiy.com/index.php?topic=66243.80
And here is more mentioning of it being 10:1: https://groupdiy.com/index.php?topic=51862.360

What do you think? 7:1 or 10:1?

Thanks in advance!
« Last Edit: August 14, 2018, 10:49:57 AM by wlinart »


Moby

Re: BV11 ratio?
« Reply #1 on: August 14, 2018, 09:12:35 AM »

Moby bv11 (groupdiy): ? Not sure.

10:1
For microphone transformers,  BV.8,  Bv.11,  Bv.12, etc.. contact me at mobyelectronics at gmail dot com

wlinart

Re: BV11 ratio?
« Reply #2 on: August 14, 2018, 10:49:26 AM »
Great, thanks, but is it the ratio of the real one? Or are there more versions?
It looks like most of the clones are 10:1, except one of the haufe's, and the cinemag. But since Haufe also got an 10:1 transformer, i'm inclined to believe that 10:1 seems more right.

Moby

Re: BV11 ratio?
« Reply #3 on: August 14, 2018, 05:31:55 PM »
Great, thanks, but is it the ratio of the real one? Or are there more versions?
It looks like most of the clones are 10:1, except one of the haufe's, and the cinemag. But since Haufe also got an 10:1 transformer, i'm inclined to believe that 10:1 seems more right.
Actually original BV.11 was made in  lot of versions and ratios, so here it is:

BV 11 = 13 : 1,  14 : 1, 10 : 1 and 7 : 1
M 49; M 49a; M 49b; M 50; M 50a; M 50b
and also,
BV 11 = 7 : 1
M 49c; M 249c; M 50c; M 250c
For microphone transformers,  BV.8,  Bv.11,  Bv.12, etc.. contact me at mobyelectronics at gmail dot com

wlinart

Re: BV11 ratio?
« Reply #4 on: August 15, 2018, 02:02:51 AM »
Actually original BV.11 was made in  lot of versions and ratios, so here it is:

BV 11 = 13 : 1,  14 : 1, 10 : 1 and 7 : 1
M 49; M 49a; M 49b; M 50; M 50a; M 50b
and also,
BV 11 = 7 : 1
M 49c; M 249c; M 50c; M 250c

Wow, this is a great answer, thank you very much! This clears up a lot.
So, as i'm building a M49c, a 7:1 would be more correct.

Moby

Re: BV11 ratio?
« Reply #5 on: August 15, 2018, 05:25:29 AM »
Wow, this is a great answer, thank you very much! This clears up a lot.
So, as i'm building a M49c, a 7:1 would be more correct.
If you build exact clone (same tube same coupling cap) then yes. Of course, If you need 7:1 Bv.11 I do that version also , all together with other ratios.
For microphone transformers,  BV.8,  Bv.11,  Bv.12, etc.. contact me at mobyelectronics at gmail dot com

wlinart

Re: BV11 ratio?
« Reply #6 on: August 15, 2018, 12:04:45 PM »
If you build exact clone (same tube same coupling cap) then yes. Of course, If you need 7:1 Bv.11 I do that version also , all together with other ratios.

I'm building one with the 6s6b-v tube. In this thread they're speaking of a tube output impedance of 4-6kOhm: https://groupdiy.com/index.php?topic=66243.0. There's also mentioning of the different ratio's, and that a 7:1 ratio good is for the 6s6b.
For the coupling cap i've got a 1uF PIO.
 And good to know that you could also make your transformers in a 7:1 ratio, maybe i'll take you up on that offer.

wlinart

Re: BV11 ratio?
« Reply #7 on: August 15, 2018, 02:06:42 PM »
I think i begin to understand it a little bit better:
So if the tube (6s6b) has an impedance of 6k = 6000 ohm, with a transformer of 7:1 the output impedance would be 6000:49 = 122ohm.
With a 10:1 transformer that would be 6000:100 = 60ohm.

With an impedance of 4k:
7:1 => 82
10:1 => 40

The original m49c has a transformer with 200 ohm output or can also be strapped for 50ohm. But the standard was 200 ohm, i think?

So even 7:1 wouldn't be right? But would be closer than the 10:1.
Or did i just ignore the coupling cap, and does this one also have an influence?


 

Related Topics

  Subject / Started by Replies Last post
1 Replies
1226 Views
Last post June 24, 2004, 11:07:43 AM
by sismofyt
6 Replies
1508 Views
Last post June 02, 2005, 02:05:49 AM
by gyraf
7 Replies
1876 Views
Last post January 19, 2007, 11:00:47 PM
by Silvas
7 Replies
2084 Views
Last post May 19, 2007, 01:24:26 AM
by ChrioN