All things G1176 - the new "repost" thread.

[mnats]

[quote author="caps"]Is the comp actually in line and recorded in the first 5 seconds or did you just insert 5 secs silence?[/quote]
Yes. That is, my clone is in line for the entire recording but on the original source I did add 5 seconds of silence. So you're hearing the entire audio chain up until the slam.

I've posted some additional info here.

 

[Rob Flinn]

MNats

Have you had an opportunity to compare the Lundahl to the OEP transformer?
A friend & I did a comparison between Jakobs rev 7 with Lundahl output transformer but without input transformer to a pair of UREI rev H the otrher day.

The Lundahls are more toppy than the originals. However they do compress in a similar way.

Even with Chef`s rewiring of the transformer they lack a lot ofgain compared to the real things.

 

[matthias]

@ mnats:

very nice and informative page.. !!


is the lundahl output transformer connected in reverse on your pcb layouts, or is this not implemented yet...??


mat

 

[deanp920]

Even with Chef`s rewiring of the transformer they lack a lot ofgain compared to the real things.

That mod does not get the output transformer configured for max output. With the Chef mod, you're still lacking 6 db of output gain AND headroom.

You need to go all the way and reverse the transformer so that you get a 1:2 step-up ratio. At that point everything pretty much falls in line with the original UREI specifications for maximum gain and headroom. If you use the optional input transformer, expect a small loss there(1 or 2 db) compared to the IC input.

The output impedance is 150 ohms in this reversed configuration, and will drive a 600 ohm load to the same levels as stated in the UREI manual. Frequency response remains ruler flat as well.

When I have a little more time I'll repost the instructions here. If someone has them saved from page 44 of the old thread, please feel free to go ahead and repost them here.

Dean

 

[Rob Flinn]

Dean

Thanks for that info. Are the 2 primary & 2 secondary windings both wired in series when reversing the transformer ?

I would like to have this extra gain, since I have found the 1176 quite useful to make up gain lost elsewhere in the signal chain. In the current configuration when the out put is set to 1/2 o`clock on my real 1176`s I get the same gain as the G1176 on full output.

Are the 2 primary & 2 secondary windings both wired in series when reversing the transformer ?

 

[romeojesus]

hi!

before finishing my g1176 a few more questions:

i am using the 5532 as input!

so i can leave out all the components marked with an *, right?

what about the 1000u/35 cap near the bd517?

(somewhere in this thread i read that putting this in gives me lower noise! so i guess it´s optional, but has nothing to do with the
optional lundahl inout trafo??)

what connections between the boards should be shielded?
where do i ground the shields??


thanks

christian

 

[mnats]

The wife wants a new gate for the side of the house so it's chiselling mortises and sawing tenons for the next couple of days...

Have you had an opportunity to compare the Lundahl to the OEP transformer?

No, but I do intend to try this at a later date. My understanding is that the Lundahls are less colored.

Even with Chef`s rewiring of the transformer they lack a lot ofgain compared to the real things.

I didn't use the Chef mod which seems to involve paralleling the input windings but rather the one suggested by Jakob which involves reversing the transformer but keeping both windings wired in series.

is the lundahl output transformer connected in reverse on your pcb layouts, or is this not implemented yet...??

Yes, it's definitely reversed on my pcb. This was one of the main reasons I bothered to make a new version. Because the Lundahl isn't symmetrical you can't just rotate it on the board so you either have to cut traces and use wires or use my layout. I have also posted another version that uses the original output transistors since many people have access to these devices but want/need the other mods.

Are there any other components I can omit other than the 5532 if I will be using the Lundahl on the input.

Look at the schematic in the upper left hand corner. Eliminate everything to the left of R5, the input pot. Looks like the input pot itself is still being used on the Gyraf rather than a T attenuator on the UREI. The components are marked with the original component identifications on my .pdf layout file so you may want to download these to have a clearer idea of which parts to leave off (Gyraf .pdf mostly has component values). That part of my board is nearly identical so it should be clear which components to pull.

so i can leave out all the components marked with an *, right?

I think the parts marked * on Jakob's layout are mostly the optional bypass and filtering capacitors. They don't directly relate to using the opamp or transformer input issue. The two 10k resistors marked * can be left off if using the opamp.

 

[deanp920]

Rob,

Are the 2 primary & 2 secondary windings both wired in series when reversing the transformer ?

Yes, they are. Just make sure you get the polarity right(you don't want phase reversal along with the extra gain), as well as leaving pin 3(can+core) grounded.


Dean

 

[Rob Flinn]

Thanks Dean

I`ll give it a try tomorrow.

 

[mnats]

found it...

[quote author="deanp920"]If you want to try it 1:2, in and out connections should be reversed - by cutting tracks and soldering on some wires..
On the primary, pin 4 should be isolated from the ground plane by cutting the wide ground trace with a dremel tool or utility knife.

The trace connecting C15 to pin 1 must be cut.

On the secondary, pins 6 and 9 need to be isolated by cutting the traces near the pins.

Solder a jumper wire from pin 4 to the solder pad for point Y.

Solder a jumper wire from pin 1 to the solder pad for point X.

Solder a jumper wire from pin 9 to the solder pad for the negative side (output) of C15.

Solder a jumper wire from pin 6 to pin 3.

That should leave the transformer running 1:2, and increase in the signal line amp's gain by 12db.

For what its' worth, I measured the transformer's output impedance, wired stock (2:1), at about 30 ohms. This is encouraging, since, when wired 1:2, the output impedance should still be well under 600 ohms.

EDIT 4-12-04 Instructions above no longer cause phase reversal.

Dean
[/quote]

 

[Rob Flinn]

Thanks Mnats & Dean

 

[Rob Flinn]

Just tried the mod, it works but I`m not getting the 12dB increase. I`m only getting about +4dB ? Any ideas ?


The instructions are not quite right as far as I can tell. I think pins 6 & 9 should be connected but ther is only mention of osolating them in the instrctions.

Mnats I notice on your board this mod is carried out in a slightly different way t o the instructions above.

 

[Rob Flinn]

I think pins 6 & 9 should be connected but ther is only mention of isolating them in the instrctions.


Sorry I think I meant pins 7 & 10

 

[deanp920]

The instructions are not quite right as far as I can tell. I think pins 6 & 9 should be connected but ther is only mention of osolating them in the instrctions.

The instructions are correct.

Pins 7&10 are not mentioned, as they stay connected with the existing trace. Same with pins 2&5.

Pins 6&9 MUST be isolated so pin 6 can be grounded, and pin 9 driven from C15 like the procedure states. That converts the secondary of the 5402 into the primary.

Pins 1&4 are isolated and then jumpered to the x and y points, respectively. That converts the primary of the 5402 into the secondary.

Now you have a 12db increase in output from the stock PCB.

Simple. :grin:

Dean

 

[mnats]

Mnats I notice on your board this mod is carried out in a slightly different way t o the instructions above.

Still a bit bleary-eyed. Damn cold I caught has woken me up again with a cough...anyway, as I recall when I did my board it was just convenient to wire the transformer mirror-imaged from the Dean mod. Doing it that way allowed the OEP pinout to nest there without wire jumpers running all over the place.

 

[Rob Flinn]

Mnats

Your layout looks good. I`m getting a friend to make me a pair of boards so I can do some with the OEP tansformers.

 

[mik]

I've cecked the Mnats layout, it's seems to everything it's ok but the Lundhal out trafo dimension missmatch to the original: they are 2mm smoler , 28mm instead 30 so It will difficout to fitt a lundhal there.
second:
for macth a correct Eurocard dimensio it should be little bit smoler more similar dimension to the Jako's design , this because fotoresit is not so good close to the adge of the board, so the pads can go really bad, even using a good quality boards.
Thank you Mnats for your job
mik :sam:
P.s.
I'm anxiusly waiting for the correct one 'cause I really need it!

 

[mnats]

mik,

Thank you for checking the layout - I really appreciate it. You're right, the pads were .1" short of their correct location. I've fixed the files and uploaded them to my site.

I didn't know the resist was poor at the board edges with the Eurocards. The overall dimensions of the board is identical; I'll try to pull the traces and pads away from the edges but I don't think it will be easy or as quick as fixing the Lundahl problem.

Thanks again for pointing out the problems.

 

[orson whitfield]

Jakob, Dean,

The VU is acting as it should now! :thumb: :green: :sam: And no more huge gain increase when the ratio switch is set to 1:20.:guinness: :!: :grin:
I am calibrating and I notice the output is always a 1/3 lower than input no matter how I attenuate the input volume from my audio generator. THis didn't happen before. BTW, the part that was wrong was the 10M resistor at the top of the ratio switch PCB. Anyhow, what's going on that I can't get the GR meter track calibrated?

 

[fum]

Ok, I'm troubleshooting the second of a pair of 1176's, and am getting to the stumped part, so thought I would post for suggestions.

It's not passing audio yet ( the other works fine, dammit =) ).

At present the problem is in the signal pre-amp section. The voltages are not right, and I can't figure out why. Have gone through looking for shorts, and have checked out the parts values to make sure they are correct. Here's what I got:

The voltage comin off the regulator is right on at 30.3, but post R17 (6.8K), I'm down a couple volts from what should be 25.8, I'm sittin at 23.4V.

so by the time I start measuring voltage at Q2 and Q4, things are not good.

Q4:

E 1.3 (11.5)
B 1.9 (11.9)
C 30.3 (30.3 )

Q2:
E 0 (.5)
B 0 (1.02)
C 2.5V (1.76)

Thoughts? I'm pulling out the hair I don't have :?

ju