[Moby]

Mic is finished and sounds fantastic...quiet and smooth. I ended up with a clarity caps coupling cap but I would like to play around with this. I am thinking of trying a PIO but it’s not easy to find one that fits. I ordered a couple of nos Cornell-D 1uf 200v that looks like it will fit...or I could go 0.47uf and use a k42. Anyone tried a PIO in that position? Any suggestions? Thanks in advance.

give a chance to NOS Soviet caps if they can fit inside

[Purplenoise]

give a chance to NOS Soviet caps if they can fit inside

Hey Moby, thanks. I have a k42 0.47uf that fits. Do you like those or should I try a k40 instead? I think the 42’s are not as good as k40s but I could be wrong.

[Moby]

Hey Moby, thanks. I have a k42 0.47uf that fits. Do you like those or should I try a k40 instead? I think the 42’s are not as good as k40s but I could be wrong.

I like them both But you can always compare them. Matter of taste IMO

[Bowie]

Sellers report good measurements as far as Vloss and esr. Hopefully they will be ok.

^Good to hear. Smart to go with tested caps. I have a decent stash of old NOS caps and it's ghastly to see how many of them test. Makes you realize why a lot of the audio vets are cynical about people using old caps.

I'm not into going overboard with exotic caps because that market is saturated with audiophollery but rolling caps in the M49 output was a real eye-opener for me. I am cautious to recommend thsi since it might not fit but check the physical measurements on the Mundorf EVO Oil (just oil, not the up-charged variants).

Also, good to hear about the tube!

[Purplenoise]

I like them both But you can always compare them. Matter of taste IMO

Haha true...thank you so much

[Purplenoise]

^Good to hear. Smart to go with tested caps. I have a decent stash of old NOS caps and it's ghastly to see how many of them test. Makes you realize why a lot of the audio vets are cynical about people using old caps.

I'm not into going overboard with exotic caps because that market is saturated with audiophollery but rolling caps in the M49 output was a real eye-opener for me. I am cautious to recommend thsi since it might not fit but check the physical measurements on the Mundorf EVO Oil (just oil, not the up-charged variants).

Also, good to hear about the tube!

Yes, I have had a few that I ended up throwing out but it seems that some of them have a few good years left. Trial and error I guess. I’ll take a look at the mundorf. Thank you so much.

[Purplenoise]

So I tried one of the nos caps I got on the output. A Cornell dubilier 1uf 200v. I believe it is paper in wax but I could be wrong. Vloss and esr is really low.
Very different sound than the claritycaps I had there before. Less direct with softer/rounder highs and a general sense of roundness. It feels darker, more relaxed and “3D”...more natural and real but pleasant at the same time...This sense of “realness” might be, although contradictory, due to less detail and maybe more harmonic distortion that gives the impression of distance and space.
I’ll probably have to break it in a lot more so we will see...
Next will be a sprague metalized paper.

[Purplenoise]

So just to make sure about setting the bias...
At b+118 I found the most “pleasant “ results are at:
A 43v
K 1.5v
H+ 6.3v

Does that sound right? Or am I out of spec? Thanks

[doqmemory]

Has anyone tried Chunger's CU-49 for the M49 using a 7-pin XLR insert instead of the Binder connector?  I would like to try using the same cable/ps setup for a D-269c, so would prefer using XLR.

[TillM]

As far as I know, is there no adapter plate for xlr available.

[shabtek]

As far as I know, is there no adapter plate for xlr available.

Ben aft beezneez claimed to have made an adapter to fit an xlr but has not been in a hurry to share

[Delta Sigma]

So just to make sure about setting the bias...
At b+118 I found the most “pleasant “ results are at:
A 43v
K 1.5v
H+ 6.3v

Does that sound right? Or am I out of spec? Thanks

Sounds like you're right where you should be, provided your load is 100k, your plate current is 0.75mA.

My M49b with 6S6B has an H+ of 6.1V, B+ of 116V and a plate current of 0.73mA. THat's what I settled on for my mic and if I ever remember to print up some labels, I'll tape those values to the inside of the power supply for checks.

[Purplenoise]

Sounds like you're right where you should be, provided your load is 100k, your plate current is 0.75mA.

My M49b with 6S6B has an H+ of 6.1V, B+ of 116V and a plate current of 0.73mA. THat's what I settled on for my mic and if I ever remember to print up some labels, I'll tape those values to the inside of the power supply for checks.

Thank you so much. Yes plate current I believe is somewhere between 0.70 and 0.75 mA. I’ll measure again to make sure of the exact value. Just to double check...the contact points to measure the plate current are the same as measuring the plate voltage right? Thanks again

[sedit1]

Hi,

I’m starting my build and didn’t find any answers, but what are the advantages of using bv11 instead of t49 or are there any?

[Delta Sigma]

AMI's BV11 is a recreation of the real BV11. The T49 is an economical mic transformer that has similar characteristics to the BV11 but is not a clone. I would guess they have different laminations and are possibly wound differently but have the same ratio and inductance.

AMI makes good transformers so I'm sure either would sound good though the BV11 Classic probably sounds a little better.

Personally, I would go with Moby's BV11. I replaced my AMI BV11r iwth a Moby BV11 and couldn't be happier with it.

[Delta Sigma]

Thank you so much. Yes plate current I believe is somewhere between 0.70 and 0.75 mA. I’ll measure again to make sure of the exact value. Just to double check...the contact points to measure the plate current are the same as measuring the plate voltage right? Thanks again

Measure across your 100k load resistor and move the decimal. I measure from plate to ground and subtract that from B+ because there's an easy place to measure. In your case, (118V-43V)/100k=0.75mA.

[Purplenoise]

Measure across your 100k load resistor and move the decimal. I measure from plate to ground and subtract that from B+ because there's an easy place to measure. In your case, (118V-43V)/100k=0.75mA.

Great thanks, I just wanted to see if the math are the same in practice. I have recalibrated to 116v and 43v plate to get to 0.73mA. It’s interesting how different the sound is with such small difference. At 116v 43v (0.73mA) the sound is denser with softer transients. At 118v 43v (0.75mA) it is actually cleaner, more “modern” with sharper transients. Slight but audible. Actually I would prefer 0.73 for vocals and 0.75 for instruments. My voltages fluctuate a little in my room so I hope my findings are accurate and nothing else is at play haha. Thank you again.

[Delta Sigma]

Remember, wall voltages may vary and that will affect passive power supply powered mics. The difference in most areas should be small but if you move it around, it's something to consider.

[Purplenoise]

Remember, wall voltages may vary and that will affect passive power supply powered mics. The difference in most areas should be small but if you move it around, it's something to consider.

Yes of course...I am getting a variac for this exact reason. Even a couple of volts changes affect the sound. Now I should probably do some tests with an oscilloscope and signal generator to see if the plate current of 0.73mA has the same response in 5840 as in ac701 haha...

[Purplenoise]

Can someone please inform of how to connect an AC701. Which pin to which pcb point? I’ll probably have a phaedrus ac701 on loan to try out soon.
I think I saw it here but can’t find it now. I guess since k,a, h+ are labeled the same my question is about the h-( -f) and (g). I would say h- ( -f ) goes to HG and top pin (g) goes to FGRID?
Thank you so much.

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