[micaddict]

I'm in trouble again...

Is that the AMI body?

[poctop]

I'm in trouble again...

Is that the AMI body?

did not mean to
best,
DAn,

[poctop]

I'm in trouble again...

Is that the AMI body?

did not mean to
best,
DAn,

Yes this is a body i had received from AMI 1 year ago it was about time i finish this one as i am waiting for another one from Riggler and Eric , Now the objective is to test my reskin lab with original K47 Backplate waiting here and give it a shot
and then the U87 (K67-K87) same experiment........ Stay tuned...
Best,
Dan,
 

[Winetree]

I want to build the M49 "B" round version.
The pictures on page 1 show the building of the "C" version.
Are they built the same?

[micaddict]

M49b here, though not round per se:

http://groupdiy.com/index.php?topic=50834.0

[dmp]

I want to build the M49 "B" round version.
The pictures on page 1 show the building of the "C" version.
Are they built the same?

Very similar - I've been building up the b and you just have to watch for the few components that differ.

[poctop]

I want to build the M49 "B" round version.
The pictures on page 1 show the building of the "C" version.
Are they built the same?

Very similar - I've been building up the b and you just have to watch for the few components that differ.

+1
YeP, if you foow the Silk you wil be alright as it is the same strategy for both b, c
Best,
DAN,

[Edward]

I would need some help with with finishing my M49B.. i feel i am really close but i think something is not right.

I measure:

PSU - H+ 6.1V (DC)
         B+ 120V

MIC - K  6.1V
         A  67.7V (will read higher values when turning R7 but not lower than this...)
         H+ 6.1V
         HG 0.03V

PAD 5 @ MIC reads 120V

PAD 6 @ MIC is 0V, 57V or 116V


Any ideas on what i could try next? 

[Edward]

Sorry to bore everyone with this, but i need some help.

Am i thinking correctly here:

I have 100K plate resistor, 120 - 68 = 52V

Which is too low..

So to adjust the plate voltage to 50V i need to adjust the plate resistor. Right?

How do i calculate that? Or is it trial and error thing..?

[poctop]

Sorry to bore everyone with this, but i need some help.

Am i thinking correctly here:

I have 100K plate resistor, 120 - 68 = 52V

Which is too low..

So to adjust the plate voltage to 50V i need to adjust the plate resistor. Right?

How do i calculate that? Or is it trial and error thing..?

it will really be only if you put a AC701K in there that you will obtain those precise results,
this is why the self bias is a no brainer but the b is much more fun and learning, 
I have 100K plate resistor, 120 - 68 = 52V so this mean 52V drop trough 100K means 0.52ma,  U= RI
52V/100K = i in ma

here is an example,
B+ = 115V
Plate = 53V
Drop across 100k (plate resistor)
= 115-53 = 62V Voltage drop across 100k
that means the tube running at .62ma
We want about 45V on the plate to get to
the specified 0.7ma then
 
the best at this point is to replace temporarly the plate resistor with a pot lets say  250K and try to tweak both bias pot and plate resistor pot until you find the nearest condition , no one uses same tube and this is a related together and the 2 parameter are related, this is the best approach once you find the sweet spot for it you can replace the plate resistor whit with a 1/4 watt resistor ,
try that and keep me posted and let me know what the balance value you find or the nearest , what tube did you used, and make sure you try the mic first.

Let me know,
Best,
dAN,

[Edward]

Sorry to bore everyone with this, but i need some help.

Am i thinking correctly here:

I have 100K plate resistor, 120 - 68 = 52V

Which is too low..

So to adjust the plate voltage to 50V i need to adjust the plate resistor. Right?

How do i calculate that? Or is it trial and error thing..?

it will really be only if you put a AC701K in there that you will obtain those precise results,
this is why the self bias is a no brainer but the b is much more fun and learning, 
I have 100K plate resistor, 120 - 68 = 52V so this mean 52V drop trough 100K means 0.52ma,  U= RI
52V/100K = i in ma

here is an example,
B+ = 115V
Plate = 53V
Drop across 100k (plate resistor)
= 115-53 = 62V Voltage drop across 100k
that means the tube running at .62ma
We want about 45V on the plate to get to
the specified 0.7ma then
 
the best at this point is to replace temporarly the plate resistor with a pot lets say  250K and try to tweak both bias pot and plate resistor pot until you find the nearest condition , no one uses same tube and this is a related together and the 2 parameter are related, this is the best approach once you find the sweet spot for it you can replace the plate resistor whit with a 1/4 watt resistor ,
try that and keep me posted and let me know what the balance value you find or the nearest , what tube did you used, and make sure you try the mic first.

Let me know,
Best,
dAN,

Thank you Dan! Great advice. I will replace R10 with a pot temporarily as you suggested and see how close I can get tweaking that and R7 bias.

My tubes are RCA branded CV3929/5840 tubes.

You wrote in the other M49 thread "and make sure you do have 58-59V on  the R6-R7 node." How exactly do I measure that?

Best Regards,

Edward

[poctop]

Sorry to bore everyone with this, but i need some help.

Am i thinking correctly here:

I have 100K plate resistor, 120 - 68 = 52V

Which is too low..

So to adjust the plate voltage to 50V i need to adjust the plate resistor. Right?

How do i calculate that? Or is it trial and error thing..?

it will really be only if you put a AC701K in there that you will obtain those precise results,
this is why the self bias is a no brainer but the b is much more fun and learning, 
I have 100K plate resistor, 120 - 68 = 52V so this mean 52V drop trough 100K means 0.52ma,  U= RI
52V/100K = i in ma

here is an example,
B+ = 115V
Plate = 53V
Drop across 100k (plate resistor)
= 115-53 = 62V Voltage drop across 100k
that means the tube running at .62ma
We want about 45V on the plate to get to
the specified 0.7ma then
 
the best at this point is to replace temporarly the plate resistor with a pot lets say  250K and try to tweak both bias pot and plate resistor pot until you find the nearest condition , no one uses same tube and this is a related together and the 2 parameter are related, this is the best approach once you find the sweet spot for it you can replace the plate resistor whit with a 1/4 watt resistor ,
try that and keep me posted and let me know what the balance value you find or the nearest , what tube did you used, and make sure you try the mic first.

Let me know,
Best,
dAN,

Thank you Dan! Great advice. I will replace R10 with a pot temporarily as you suggested and see how close I can get tweaking that and R7 bias.

My tubes are RCA branded CV3929/5840 tubes.

You wrote in the other M49 thread "and make sure you do have 58-59V on  the R6-R7 node." How exactly do I measure that?

Best Regards,

Edward

that would be more something like R8-R9 node wich is the polarisation voltage of the backplate,
always good to check, measured between R8-R9 node
not sure if it is not a typo on my end ,
Best,
Dan, <

[Edward]

Hi,

It didn't work out so well with my B version so I tried the C instead..

After adjusting the PSU to 120V/6,1V, without tweaking anything I had a plate voltage of 47V, so spot on!

Cathode was spot on 1,6V as well.

PAD 6 on the mic gave me 0-57-117V.


Time to install my capsule I think

[goneglimmering]

Hey everyone! I'm building the PSU249P and had a quick question. There is something labeled SHLF in the PSU circuit. Can anyone clarify if that is an eq shelf like a low cut filter and if so, has anyone found it useful enough to ad a switch on the PSU to access it more easily?

[Nyquist]

Nothing to do with eq. It is a ground lift.

[Edward]

Hi,

Here is a vocal sample of my (hopefully) finished D-49C build. The sound really is what i was hoping for when i started building this thing. What do you think? 

https://soundcloud.com/kimmopeltola/d-49c-test

[mgronroos]

Silky, buttery, smooth...you want more, Edward..? 

BTW: How many 5840s did you go through?
I'm not done with mine yet, but thinking I may get some more tubes to find a quiet one (I just have 5).

Sounds great!

//Michael

[Edward]

Silky, buttery, smooth...you want more, Edward..? 

BTW: How many 5840s did you go through?
I'm not done with mine yet, but thinking I may get some more tubes to find a quiet one (I just have 5).

Sounds great!

//Michael

Not many, bought a kit of 5 of JAN 5480W and CV3929. This is the third tube that's in there. Burnt in for two days. The tube I had before this one actually was a little quieter but I recently changed the C5 cap and at the same time I swapped the tube.

Thanks for the comments Michael 

[kmozart]

I'm going to give it a shot on this build as well. M49b Version. I used to have the original one, ears ago (I was young, unexperienced,... Sold it... I will regret that for the rest of my life!  ....)
. NEVER forgot the sound, and never heard similar. I built oliver's kit of U47 I'm VERY happy with.
Started collecting the parts. Got the boards, round verson, Paid Spence for the body, got couple of the JAN 5840W an the RCA ones of Ebay. Now looking for the trafo. Would like to go with AMI T49, or BV11R. I can't seem to find where I can buy those. Sent Email to AMI, No response. Do you guys know of any stock/source?
Another question is, there is also BV11A. Is that going to work with 5840? 

What I could not realize is will this boards fit into the TLM49 body?  Can Anybody confirm that? 


Love his tread! lots of good info, just red it all!

THANKS!!

[Edward]

I'm going to give it a shot on this build as well. M49b Version. I used to have the original one, ears ago (I was young, unexperienced,... Sold it... I will regret that for the rest of my life!  ....)
. NEVER forgot the sound, and never heard similar. I built oliver's kit of U47 I'm VERY happy with.
Started collecting the parts. Got the boards, round verson, Paid Spence for the body, got couple of the JAN 5840W an the RCA ones of Ebay. Now looking for the trafo. Would like to go with AMI T49, or BV11R. I can't seem to find where I can buy those. Sent Email to AMI, No response. Do you guys know of any stock/source?
Another question is, there is also BV11A. Is that going to work with 5840? 

What I could not realize is will this boards fit into the TLM49 body?  Can Anybody confirm that? 


Love his tread! lots of good info, just red it all!

THANKS!!

Hi!

Copied from AMIs web page:

BV11A  -  Direct replacement for M49/50, historically correct  -  AC701, AC701K
BV11R  -  BV11A with extended low and low-mid frequency response  -  EC92, EF732, 5840, 6072a and 12AY7WA

So for 5480 tube AMI recommends BV11R.

About availability, I'm uncertain of the current status... Read http://groupdiy.com/index.php?topic=57047.0

/Edward

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