Vari-Mu Compressor Project

Slightly tweaked Altec 436c


Analag

How does it sound?

Jakob E.

It has a big but very controlled sound, this should be used for sounds you want to give definition and presence in a mix. Even if it's at a low volume.

Analag

Interesting indeed.

What are the in and out transformers?

How do you select input tubes?

Jakob E.

Pardon my squinty eyes:

Are input tubes 5965?

Is V3, static grid bias, really -12V?

Seems to me, 200-250V and -12V on 5965 puts you way down in the cutoff range, fraction of a mA. At that point, you may have enough bias current to pass signal. But when the rectfiers drive the grids more negative, won't the input tubes starve and be unable to drive the output tubes to nominal level?

What is not shown in the schematic is that this voltage is variable by mean of a pot. I like to go beyond theory and experiment with things.

Analag

Could you comment something about the transformers?!

What`s the effect of C3 on the output transformer ?

Seems to me that C3 is there to prevent direct current through the windings.

The purpose of the -12V supply is not obvious to me, since the way the 10K pot is wired ensures that the negative bias doesn't make it to the other end of the pot. Either I'm overlooking something or there's an error on the schematic.

Some means to trim the balance of plate currents in V1/V2 wouldn't be a bad idea.

Incidentally, the 5965 is a computer tube with a sharp cutoff characteristic. It's similar to my beloved 12AV7 :grin: It's also easy to find and inexpensive, at least here in the States.

Datasheet

Yes I make the correction to the schemo but never bothered to repost.
The 5965 is really nice I bought a load of the GE JAN clear top and RCA types.

Analag

Funny coincidence, just a few weeks ago I was thinking of trying out a 12AV7 or 5965 in an Altec-type compressor circuit. The plate curves look promising for that kind of service, and as of this writing that family of tubes is still cheap and not hard to find.

What I had/have in mind is not very unlike what you posted, but I'm thinking of direct coupling to the output transformer as well as a different output tube type. I'm also thinking an interstage xfmr would give better results than R-C coupling between the stages, in this type of circuit.

[quote author="analag"]What is not shown in the schematic is that this voltage is variable by mean of a pot.[/quote][quote author="analag"]Yes I make the correction to the schemo but never bothered to repost.[/quote]
Dude, you might be building yourself some great sounding "stuff," but you should think about getting your act together. :razz:

~ Charlie

5687's are $3.90 and have an excellent transient response, the 6N1P's are also on my favorite list. Big cathode tubes are current hungry but they make up for it in SLAMability. Eliminate the caps if you can, wish I could hear it
My act is together, dude, how bout yours. Checked out your site. Kinda anonymous aintchya.

Analag

hi
i have a 436b here.. it pretty nice...
i'd be interested in trying this design but...
can you please link to the latest schemo with all the changes noted?
that would be really cool..
that way i can print the schemo and work offline :wink:
thanks
ts

[quote author="analag"]
My act is together, dude, how bout yours. Checked out your site. Kinda anonymous aintchya. [/quote]


with all due respect, charlie isnt the one here who consistently posts schematics with errors. I built the acoustic 360 preamp he helped to backwards design and it works quite well. Id be hesitant to try building any schem you have so far posted here based on your comments.

dave

A couple of times, I've sat bolt upright in the middle of the night, realizing that some schematic/sketch I posted may have had an error. I've gotten out of bed to power up the computer and post a correction. I know that's an extreme example, but I think most of us here take pains to present accurate information.

No offense, analag, but the "never bothered to repost" comment and your subsequent, unwarranted snipe against Charlie are two things that do not inspire much confidence. And unless the name on your driver's license is "analag" and you happen to look exactly like Haile Selassie, you hardly have grounds to criticize anyone here for being "anonymous."

You present interesting ideas here but honestly, I have to wonder if these brilliant designs of yours really exist outside of the simulator. And considering the arrogance you often display, and your style of writing, I know I'm not the only one here who thinks you might be just another incarnation of "Doc Holliday."

?vaporware?

or

for real?

seriously :?

later
ts

Well I'll be a SON OF A B...CH, I really got you going didn't I. Brother my designs are real. As a matter of fact I'm running my simulator and building my FETCODED design right now, I just took a break to check up with my cybernetic boys. Only to find Dave lecturing me. I can appreciate a friend (I can call you that, can't I) who takes the time to offer me advice on improving my so called deficiency in credibility, ethics, arrogance and the list goes on. My name is Rowan by the way. In the winter I do look almost like my avatar. I love to consider circuits when I go jogging, which is every other day (got to slow down the aging process you know how that is). I am getting ready to post some pics of my designs, my studio, but not of me. and I will fix the schematic.

Yours Sincerely,
Rowan S.

[quote author="analag"] I am getting ready to post some pics of my designs,
Yours Sincerely,
Rowan S.[/quote]

Hey Rowan,
Looking forward to see that!!! :thumb:

I mean, back it up BRA. :green:

[quote author="analag"]My name is Rowan[/quote]

Hey, I know a dude from CT named Rowan who also has an attitude problem! You ever worked around Hartford?

Peace,
Al.