M610 Microphone Pre schematic

[mrclunk]

It works!

Initially the HT was up around 370V so i made some changes to the supply circuit incorporating some of kingstons suggestions. Added another RC stage. HT under load is now around 270V. Heaters @ 6V.

Only had it on for a few minutes with a crappy dynamic mic but seams to have plenty of gain and no drastic low frequency roll off.  ;D

Seems very quiet too, only some weird chirpy / ticking sounds when the gain is fully up. Probably coming from my laptop which was next to it at the time.

Hopefully have some time tomorrow to tweak and test  properly.

 

[mitsos]

Awesome news man! Good job! I think you're the first!! Please let us know how your further testing goes.. and of course, pics please? 

 

[seavote]

nice! more details and pics please.

 

[mitsos]

Meeeestur Cluuuuunk.....?

just remembered this thread today. Any news on your build?

 

[mrclunk]

alas no my friend....

I've a lot on my plate at the mo, but u lot will be the first to know of any progress.

 

[sgmezei]

Hey folks,

First post here! Cool forum!

I am actually repairing a 610 preamp right now and have to replace the gain pot. It is the blue bourns type but the code on the casing is not telling me whether it is log or linear. I have been looking on here to find the schematic but haven't had any luck.

Any help would be appreciated!

Scott

 

[Ego Tripper]

Well, if you know it needs to be replaced, then just desolder/unmount it from the preamp, then measure it's max resistance with the shaft turned all the way to that side. Then, measure it's resistance with the shaft centered in it's rotation. If that value is roughly half the resistance of the initial reading then it's a linear pot. If it's significantly less, (which it probably is), then it's most likely a log taper.

If the pot is physically damaged to the point where this test is not possible, then you'll have to take the pot apart and measure the resistance directly along the carbon track (you're gonna replace it anyways, right?). Or just measure the gain pot from a functional unit, to which you may or may not have access...

Looking at the schematic, I would be pretty surprised if the taper was anything other than logarithmic...

 

[mrclunk]

So i finally had another look at my diy 2610 yesterday. Found the silly mistake that was responsible for the low freq oscillation.
From the junction of R22 and C6 there should be a 100K then a 32pf to ground.

I've still a little mains hum but i'm sure i can iron that out.
sorry to everyone who's pm'd me about this...

updated schematic to follow later.

 

[sgmezei]

Well, if you know it needs to be replaced, then just desolder/unmount it from the preamp, then measure it's max resistance with the shaft turned all the way to that side. Then, measure it's resistance with the shaft centered in it's rotation. If that value is roughly half the resistance of the initial reading then it's a linear pot. If it's significantly less, (which it probably is), then it's most likely a log taper.

If the pot is physically damaged to the point where this test is not possible, then you'll have to take the pot apart and measure the resistance directly along the carbon track (you're gonna replace it anyways, right?). Or just measure the gain pot from a functional unit, to which you may or may not have access...

Looking at the schematic, I would be pretty surprised if the taper was anything other than logarithmic...

Thanks dude. I was definetly being lazy and haven't removed it from the little daughter PCB that it is on. I will do that and see which it is.

Thanks again!

 

[ding]

I've slowly been piecing together our 2-610. 
Just building one channel at the moment as the output transformers £100!
Once i've got it going i'll order the parts for channel 2.

Please could you guys cast an eye on my psu design.
Circut for my PSU.

Its a simple affair, my thinking is get it going first and then refine the supply later if neccesary.
Never 'designed' a valve supply before so your thoughts would be really appreciated. (Also, i'm too young to die!)
I've basically copied the the HT supply from NYD's MILA, the heater supplies from the PM660 and i forget where the phantoms from...

At the moment it'll only be powering one channel but for two channels should i have a separate crc stage feeding each channel for better separation?

Also i've re-draw a version of the 610 schematic but without the eq section. Think it's ok...?

I've some p2p layouts drawn up too, i'll post them once its up and running, bit scrappy at the mo.

best
Paul

Did you ever get this PSU schematic fully drawn out? This would be the perfect PSU for a mila I am looking into building but I am having trouble deciphering some of the handwritten values and I see you have a question mark. Any help would be appreciated.