[Igor]

The choices are then determined by power supply:

ONLY +/- 16 [ 500 series rack] use AD711 etc for input amp and 5534 for output
511 rack with additional +/- 24 use OPA 604

That's right. IC options for both input/output amps will work with OPA604 on +/-24V ONLY.
AD711: can be replaced with low offset, low distortion, fast JFET opamp.
Again, OPA604 can be used on both +/-16 and +/-24V.
IMHO, it is really good sounding IC opamp.

You can only use the orig amps if you have the +/- 24 as well as +/- 16

Mmmmmm.... I never tried them at +/-16V and vote for using "original" amps on +/-24V ONLY.

[Peterson Goodwyn]

It looks as though there are not enough holes for the diodes on the input amp board (D2&D3). I see only 3 holes for 4 leads. What am I missing?

This kit is spectacular, btw

[Igor]

It looks as though there are not enough holes for the diodes on the input amp board (D2&D3).
I see only 3 holes for 4 leads. What am I missing?

Please, check the picture.
These diodes should be placed close to output transistor (thermal compensation).
Avoid shorting between diodes and transistor.

[Peterson Goodwyn]

Got it! Thanks

[nielsk]

Are these available?

[bruce0]

Well I am finally getting around to building these, and I have a couple of questions.

The schematic in the FEELER (the only schematic I could find) says there is an attenuator option, I can't find it.

The circuit board specifies a Cinemag option, what is the cinemag transformer recommended or specified. (I would prefer transformer balanced input, So I want to choose that option).

What attenuator is appropriate, does it fit?

There are a lot of little op-amp boards hear, but it does not appear that there is a lot of op amp sockets to put them in.  Which should I build.

Is there any sort of guide beyond the photographs....

Is there an official schematic?

I need to order the input trafo and attenuator, and then I am off to the races.

[mulletchuck]

Bruce, i'd probably build it just like the VP2x's, meaning shortest component(usually diodes) to tallest (transformers/switches).

[gzpz]

Hi
Are these 51x-f76 kits available?

[bruce0]

Thanks mulletchuck, I will build it short to tall.... But I want to put the attenuator and input transformer option in and I don't have information on the type of input trafo needed.

Not sure if you are familiar with this kit but it comes with a variety (4 or 5) op amp cards, and I am sure that I am not supposed to populate them all... I found a note in the materials that says that the kit includes enough to build 2 of them for the two amps, but which two should I use is not clear... it could be a preference thing if so I will just pick two at random?

There is no room to mount an attenuator that I can see.  I assume it is a 600 ohm T attenuator, but does it replace the make up gain control, or do I fit it somewhere else?

Anyone build one of these?

[mulletchuck]

Bruce0, i have my two kits that I haven't started building yet.   Igor does say that you can skype with him if you need help.   I've also chatted with him over Facebook chat.   But i haven't started my build yet either.   I know chunger also has a pair he is either building, or waiting to build, or they came pre-assembled. 

[edanderson]

Update: last version docs, everything is here:
http://ij-audio.com/downloads/51XF76.zip

Download the files, take 10 min to meditate on all this, than,
after you catch the logic, take some time to read schems.

INPUT TRANSFORMER OPTION:
1   CINEMAG,  0-12 CLONE,  OR OEP_A262

----OR

INPUT BALANCED LINE RECEIVER OPTION
1   THAT1246   OR INA137 OR SSM2143, DIP-8      IC2
------------------------

OUTPUT TRANSFORMER:

1   LL1524(1517), API OUTPUT, ETC               T1 

C100, R101, R84: OUTPUT TRANSFORMER'S LOAD AND ZOBEL NETWORK;
DEPENDS ON TRANSFORMER TYPE

seems like you can use the original O-12 input and B11148 output from hairball.  line inputs from cinemag and jensen have the same pinout but are cleaner / different character.  same thing with output -- plenty of choices, all up to how you want it to sound.

ed

[bruce0]

Edit:

Ed, do you mean that the pinouts on ALL of the Cinemag's are compatible?  My problem is I can't figure out which one might do the trick.  The "CMLI-4x150D" appears to be able to do the stepdown, but I can't find a PC mount version, the "CMLI-600/600C" (doesn't appear to do the step down) maybe a "CMMI-2CPC" wired backwards?  Any ideas here?  I am going to contact cinemag and see if they can enlighten me.

bb

Ed, Thanks so much.  I actually was just perusing that material (but for my addled brain it wasn't 10 minutes, it was all day, and included a lot of research on the OEP, Cinemag, HAIRBALL and MNATS sites)

I understand that you created the C-3837-1 on hairball? The  C-3837-1 on hairball seems to have a 500:200 impedance ratio, but it says it is a reproduction of the 0-12.  Is it usable both ways? Do you know what input level it can handle at 30HZ (or any frequency for that matter) within some THD range?

The original 0-12 UTC was 200:500, but I don't know how it was used in the 1176.  I did find a schematic on the MNATS site that shows the C-3837-1 wired with the step down RATIO. and shows how to wire the attenuator, but I cannot find the same information in the schematic for the F76, which omits any attenuator. 

Assuming that I have this right the the possible part numbers are:

Transformer part numbers APPARENTLY usable with the F76 (I have not tried these, but since it took all day to figure it out, this might help someone trying to do this project).

A262A2E or A262A2C (C is with Mu metal can) from OEP
C-3837-1 or CM-3837-1 from Anderson Altran Hairball
Cinemag transformer (says it is usable, but I have not found a part number (they don't appear to have a low impedance PCB mount 1:2 ratio transformer)

I did find a note in the build thread that says if I do use an attenuator I need to drill out the backplate, but I don't yet see where it goes.  The space is so tight in this module that I cannot imagine where I would add one of those nice big hairball T attenuators, but gosh it's an option, and i want to do it.

The specs for all of these transformers sometimes give pin numbers but not the pin orientation on the can.

I can't find specs on anything but the UTC.  The OEP looks REALLY easy to overload (I found a reference to 1mw at 30HZ with less than 1% THD and 100mw at 300HZ), so maybe I will just do the C-3837-1 and hope the specs are up the O-12, which was easy to overload too it seems but not as bad as the OEP.

In the materials is possible to look at the PCB in my hand, and compare it with the PCB layout in each subdirectory, and there are some text comments in those directories.

It appears that Igor has 2 IC amps - On PCB's included

One for input, which is just a chip on a 2520 board.
One for output and the output has a current boost stage of BC140 BC139.  Sort of like the JLM one but biased differently.

There is an "Input Amp" of his own design.

There is a clone of the original AMP circuits for input and output, and there are comments elsewhere in the board suggesting that he thinks the other choices are better than the original from a sound point of view.

I did not find an Attenuator card, there is a directory to change from grayhill to potentiometer on the attack and release controls.

I think I will do more research on the Cinemag site, maybe I can find a transformer there, they spec the max input levels, and I want this to be "forgiving" when I chain it in.

[spase]

did you still have that full kits for this one?

[gzpz]

Like he said...

I just looked at the schematic and it looks like a great and versatile design.  The drawing makes it easier to understand the 1176 circuit.  If these AREN'T available, they SHOULD be!

[mulletchuck]

bruce0, how are you making out with your build?   i just started mine (2 units) and i'm not understanding how i would connect the In/Out attenuators from hairball.  are they just wired, like in Jeff's kits, assuming you purchase the little PCB that goes with it?  If that's the case, then it looks like 2 are required for the in/out positions.

What's the extra ratio board for which doesn't get populated with all the resistors?   the switches at the bottom of it don't even line up with the faceplate, so is that extra board for if you wanted to build your own faceplate and not use Switches for attack/release?  This project could definitely benefit from some "during" build photos.   

The cable needs to be built with the male and female sides pointing in opposite directions.   Female side faces down, towards the motherboard, and the male side points up, as it sits on the underside of the ratio board.


I just wanted to point out to anyone who recently bought this kit.   DO NOT throw out the unlabeled parts of the PCB that are in this picture:   



They're spacers for when you mount your transformer.    I didn't know this, and they are somewhere in a New York State garbage dump or recycling facility because they weren't labeled or explained.   Now they are explained lolol

[gemini86]

uh oh...somebody must have thrown away the instructions...

[bruce0]

Mulletchuck:

Thank you for the tip on the spacers, I would have thought they were junk too.

I have not started the build, because I have not collected all the parts yet.  I still need the input transformer, I have been mailing back and forth with the fellow at Cinemag, to see what they have that would work.  I will post the part number they give me when I find out.

If anyone knows what cinemag fits, please post the part number, rather than having me torture the folks over at Cinemag as we reverse engineer the pinouts.

I am glad someone else is building this too, because maybe we can help each other and leave some breadcrumbs.  I will take pictures as I assemble mine, and try to post some sort of information on it.

Regarding Attenuators

I am also confused on this, there is no data at all in the materials that I could find.  There is one comment earlier in this thread that refers to needing to modify a bracket, I think this might be because maybe the attenuator replaces the input pot and the hole is the wrong size, or the nut is too thick.  If you look at the schematic it appears that this pot is the output of the THAT 1246.  But I haven't got a clue as to what the little x's signify on the schematic (I did decode a guess that FRATT means from attenuator, and TOATT means to attenuator and att_61 and att_62 must be the attenuator, but what the attenuator circuit is is sort of greek because I don't know what kind of attenuator would have 2 connections to ground (dual T's)... and I wouldn't think that a balanced attenuator would be grounded at all.... maybe this is some sort of code that I (very new to this) have never seen on a schematic.  I am GUESSING that somehow the notion is to put an attenuator before the transformer, install it with wires, in the same hole that the input pot goes in (when I say Pot I mean whatever came with the kit for that input hole on the front panel, I don't know if it is a pot or a grayhill) although the line is balanced so I would think the attenuator circuit would be an H or a U, neither of which are grounded.

That's a guess.... Yep)

Regarding Ratio Card

Not lining up with holes on front panels, apparently there is some notion that this kit can be built not as a 500 module but in a rack.  At least that is what is apparent from Igor's concise reply to this post http://www.groupdiy.com/index.php?topic=43338.msg565065#msg565065

This is further confirmed by the fact that the card comes with a 1U_top card that sort of duplicates the function of the other card.  It also comes with a little card that has 2 xlr connectors and a 15pin card edge connector (like a 1 unit API rack.  I assume this is so you can wire up the card in a 1 U rack.  I will post a list of pictures of what comes in the kit, and update the info as I get through the build.

Thanks for your post, it motivated me to begin doing an inventory of the kit.

My next post is a picture of  picture of the segmented card as it arrives in the kit, labeled as I currently understand it.

[gemini86]

Sorry, no. I was mostly being a smart-ass. My apologies. Generally, I try not to throw away "extra" parts until I have a finished product in front of me.

Sorry again for my non-constructive post.

[bruce0]

Here is what is in the kit, it comes well organized into separate named bags.
Not included are optional input transformers and input attenuator, and output transformer
























Front panel front and back




Knobs



Lbracket



matched fets



Milmax (or equiv) amp pins


Rack mount card? 15/30 pin API to xlr (18volts?)

[mulletchuck]

ok, for the trimmers for the Motherboard:

121 T / W101 = 100R
X103 / 0104G = 10K
127 T / X 202 = 2K
the 100K trimmer was a different color than the others and said "100K" on it.   the other 3 were blue and did not indicate their value.

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