EZ1084EQ NEW BATCH COMING - SEE MY MARCH 27 COMMENT ON PAGE 38

[shabtek]

thanks Jim.
I am in no hurry.
Are the pots +/-? i.e center is flat?--do you think my scheme for a switch with equal resistors work?

 

[Bluzzi]

Yes the pots are center 0 but they are linear so your scheme should theoretically work. Usually one likes switches so a previous setting can be recreated. Probably in a mastering setting you could also customize the min and max and make the positions small db increments for fine tuning.

But I am not sure this is the right EQ for mastering (its always a question of taste!).

Use the EQ for a while with pots and see how you like it and what you end up using it on mostly.

Cheers

Jim

thanks Jim.
I am in no hurry.
Are the pots +/-? i.e center is flat?--do you think my scheme for a switch with equal resistors work?

 

[[email protected]]

Gain Resistor values for 12 position switch
Thanks folks,
I wish it were that easy but I don't think it is. This is what I figured out so far but am open to any corrections or ideas. I can't take the 2 EQ's out of service and fool around with resistor values so I want to get the theory down first and then play.

• The original design varied the gain from -10db to +20db in 5db increments so -10,-5, 0, +5, +10, +15 and +20 therefore a 7 position switch
• I am trying to use 12 positions but keep the same range and have a 0 db position. Therefore -10, -7, -4, -1, 0, +2,+5, +8, +11, +14, +17, +20
• R1 forms a parallel resistor network with R2 through R13 across the input signal
• When you increment the gain switch, you are either adding resistance or decreasing resistance values that you have soldered into R2 through R13. This is where Bluzzi and I differ. I believe when you increment the gain switch you increase the resistance of the parallel circuit. So if I am right, R13 represents the first position (lowest gain) or least resistance and the highest gain is the highest resistance or roughly 1040 ohms . I think this because this resistor network is in parallel with the input source and the rest of the  equalizer.
• I built Unit A using 12 positions and Unit B using 7 positions before I understood what was going on and got the following results:
Gain Resistor Unit A Unit B
R13             36 36
R12             27 27
R11             13 47
R10             20 82
R9             27 150
R8             39 270
R7             56 430
R6             75
R5           120
R4           150
R3           220
R2           330
R1          2200 2200
Gain Results Unit A Volts   Unit A db         Unit B Volts  Unit B db
Pos 1                 0.56            -5            0.56        -5
Pos 2                 0.88            -1.11            0.88        -1.11
Pos 3                 0.96            -0.35            1.44         3.15
Pos 4                 1.2             1.58            2.32         7.1
Pos 5                 1.5             3.52            4.08        13.62
Pos 6                 1.92             5.67            7.12        17.05
Pos 7                 2.48             7.89           12.2        21.73
Pos 8                 3.28            10.32
Pos 9                 4.56            13.18
Pos 10                 6.08            15.68
Pos 11                 8.4            18.49
Pos 12                12.2            21.73


• Unless someone can straighten me out, next weekend I intend to take Unit B and replace R13 with a smaller resistor value and see if my gain goes down for position 1

Can you tell I prefer making this stuff more than using it?
Cheers

 

[Slenderchap]

Not sure this will help or hinder you..... but this is how you do an 11 position +/- 20dB (centre zero) on a 1073.

http://www.audiomaintenance.com/downloads/line_in_gain_values.pdf


Colin
www.audiomaintenance.com

 

[[email protected]]

This certainly helps Colin,
Many thanks

 

[Slenderchap]

That might be a little mis-leading.... that is the way it is done on an ez1073-500 which is gain limited..... you may find that you get the correct scaling, but it is off by a fixed number of dB's.... you would make the correction further down the circuit (maybe the output gain boost 100uF/1k5 combination)..... the point is that it will give you the correct impedance loading for the VTB9046.

Colin

 

[Bluzzi]

That might be a little mis-leading.... that is the way it is done on an ez1073-500 which is gain limited..... you may find that you get the correct scaling, but it is off by a fixed number of dB's.... you would make the correction further down the circuit (maybe the output gain boost 100uF/1k5 combination)..... the point is that it will give you the correct impedance loading for the VTB9046.

Colin

Thanks for pointing that out Colin.

Cheers

Jim

 

[Bluzzi]

New update to the BOM and Build Guide to reflect new values for 11 position Gain switch. Also a Bias procedure description.

Everyone should have gotten an email with link.

Cheers

Jim

 

[no-fi]

D'OH..... so last night I just set my gain switch to 7 position, as I'd been waiting to see if it would increase, but now I'm doing the last bits of mechanical assembly and I figured that was it.... I'd really prefer something a bit finer than the original step controls.

Now I've come back here and read this, I've taken the sticker back off, but am having big problems getting the pins back out..... (It took a bit of a wiggle to get all the pins in place to start)

Is there a simple way to get these out? or do I just keep tapping away patiently at the back of the switch? or do I buy a new switch?

 

[Bluzzi]

I just lent my EQs to a studio for demoing so I can't try it on those. I think I have a spare Grayhill here and I'll try tomorrow and get back to you.

Have you tried a magnet?

We'll find a way don't worry.

Cheers

jim

D'OH..... so last night I just set my gain switch to 7 position, as I'd been waiting to see if it would increase, but now I'm doing the last bits of mechanical assembly and I figured that was it.... I'd really prefer something a bit finer than the original step controls.

Now I've come back here and read this, I've taken the sticker back off, but am having big problems getting the pins back out..... (It took a bit of a wiggle to get all the pins in place to start)

Is there a simple way to get these out? or do I just keep tapping away patiently at the back of the switch? or do I buy a new switch?

 

[no-fi]

noooooo!!!! don't waste a greyhill of your own on my account!


it was my silly pushing forward and following the older build instruction on my HDD instead of looking to see if there had been an update or any action on the forum since I had last checked.

yeah I tried a magnet, but I only have fridge magnets here.. no luck with that. so have given up for now and moved on.

I suppose that I have output level controls on almost everything I'll ever plug into this anyway, so extra gain steps aren't the be all and end all. maybe if I decide I need a 2nd one, I'll have a go at fixing up this one then.

PS, I haven't looked at the schematics of this, but is it possible to replace the stepped input volume switch with a pot? I figure the EQ gains aren't switched anyway so even if I wanted to use them for critical stereo work, they're not going to be perfectly matched anyhow. And a fully variable gain control might be nice for tweaking the driven sound.


In happy news, I finished drilling the case and mounting everything today (except the XLR ins and outs... I forgot to make sure I had a set of those before easter started... oops) plus I've wired up everything else, and can confirm that my eq powers up and lights its bypass switch in both bypass directions, and nothing gets really hot to touch in a few minutes of power on.

Tomorrow is no longer easter, so I'll be able to pop down to the shop and pick up my XLRs first thing in the morning. woo! then I can have some expensive EQ fun. And once that's done, all I'll need to do is work out a blanking plate for the 2nd xlr hole set in the back, and work out what kind of knobs to put on it.


PS, don't know if anyone noticed this yet, but the Q switch seems to foul with the base plate strengthening ridge. If you don't do anything, it puts a fair bit of pressure on the baseplate (and that little switch! and the front panel screws!) and stretches the baseplate out of shape... So I filed a little gap in mine just where the switch is, and everything seems a lot happier to go together now.

PPS, I also had an issue where I only had 25mm countersink bolts lying about in my parts boxes, to mount the output transformer - and you really need a set about 40mm long to go through and take nuts on top...  But I noticed that when I use them they are long enough to go through the first set of holes in the transformer mounting, then when I screw down the lid, it holds the transformer firmly in place as well.. I thought I'd have to wait another day for a farnell order before I could put the lid on, but this discovery made me really happy.

thanks so much for making this project I'm really excited to try it out tomorrow!

I just lent my EQs to a studio for demoing so I can't try it on those. I think I have a spare Grayhill here and I'll try tomorrow and get back to you.

Have you tried a magnet?

We'll find a way don't worry.

Cheers

jim

 

[Bluzzi]

Many are living (and have lived) and perfectly happy with the 7 position switch.

The other idea is to use "vibration" to get the piece out. An electric razor maybe? The idea is to hold the vibrating item in contact with the Grayhill. Have someone hold the board upside down while you squeeze Grayhill to vibrating object (hey whatever you use is your secret  ).

The pin may not fall out but it may at least just stick out enough for you to use needle nose pliers to grab it.

The new Build Guide has just come out so its not your fault.

Not sure about the Q Switch as on both my prototypes the Q switch has a gap between it and the bottom panel. Could you post or send me a picture?

I think instead of an input pot for gain it may be better to use a pot on the output as an attenuator. I can look at the original schematic and see where it goes.

Dan has blanking plates for his cases now. Maybe ask him to send you one? On the other hand who looks in the blank of units? Once you hear this EQ you will never see the back again!

Keep us in touch with your progress.

Cheers

Jim

 

[no-fi]

Well, got it all hooked up yesterday night, and it seems to basically work, but there's some funnyness. probably need to check all my switch soldering. My guess is I've done some shorting.. and trying to play with the switches with no knobs really does in my fingers...  Ordering some collets now, hope to have them by the weekend, and the shorts fixed.

I took a picture when I did the filing, but not sure how I can show it actually fouling now I've filed it.. will post the pic when I download from my camera next. the bottom of the case was obviously pushed down at one point by the Q switch.. there seems to be clearance between the bottom of the rack and the bottom of the panel - this switch pushed the panel down so one part of it was level with the bottom of the panel... if that description makes sense?

 

[Bluzzi]

Well, got it all hooked up yesterday night, and it seems to basically work, but there's some funnyness. probably need to check all my switch soldering. My guess is I've done some shorting.. and trying to play with the switches with no knobs really does in my fingers...  Ordering some collets now, hope to have them by the weekend, and the shorts fixed.

Can you describe the "funnyness"? When you put the EQ on "Normal" bypass the Gain switch should function (signal passes by active circuit and bypasses EQ section). Do you still hear the same thing?

Double check your connections to and from the Input XFR as well as output XFR. Make sure you wired the Input XFR correctly if you used the little Fivefish PCB.

I took a picture when I did the filing, but not sure how I can show it actually fouling now I've filed it.. will post the pic when I download from my camera next. the bottom of the case was obviously pushed down at one point by the Q switch.. there seems to be clearance between the bottom of the rack and the bottom of the panel - this switch pushed the panel down so one part of it was level with the bottom of the panel... if that description makes sense?

I won't be near my unit until this weekend when I get it back but remind me to take some pictures and I'll post here. The switch should not be pushing anything drastically. It makes contact with the bottom case panel. The switch is insulated and the contact causes no problems. Did you use Dan's case?
Your explanation is confusing but if I deduce correctly you are saying the bottom panel of the case is getting pushed down enough to be level with the edge of the front panel. Is my assumption correct?

Do you have an oscilloscope and a frequency generator to do some tests?

Don't get discouraged. It sounds like a simple problem to solve. One person came to me with "no-audio" or very little audio passing and I asked him to check the XFR connections. That fixed everything. It was his input XFR wires.

If you have Skype we can try and hook up this Friday if you still need help. Let me know.

Cheers

Jim

 

[no-fi]

Hey wow! That's a very generous offer, thankyou!
The first time I tested it I only had a few moments running a synth through it, unbalanced.
got it hooked up into my fireface last night, and did some proper testing.
1) volume through the eq section is really reduced... Like, I have to crank input volume to full to match hard bypass, even with each band disabled. But in soft bypass, I get a lot of gain.
2) low freq eq seems stuck at fully negative cut.

I've got the schematics now. 1073/1084 neve manual has them. Should be able to trace these things alright.seems pretty straightforward to just ignore the mic pre section of the 1084.and the area these faults can be in looks very isolated....

 

[Bluzzi]

OK that is good actually. You know now that the active circuits are functioning (gain switch works in normal bypass). So the problem is in the passive EQ section somewhere.

Did you build yours with the LP Filter option? Check your jumper on that section. If its improperly placed you will get low signal.

Cheers

Jim

Hey wow! That's a very generous offer, thankyou!
The first time I tested it I only had a few moments running a synth through it, unbalanced.
got it hooked up into my fireface last night, and did some proper testing.
1) volume through the eq section is really reduced... Like, I have to crank input volume to full to match hard bypass, even with each band disabled. But in soft bypass, I get a lot of gain.
2) low freq eq seems stuck at fully negative cut.

I've got the schematics now. 1073/1084 neve manual has them. Should be able to trace these things alright.seems pretty straightforward to just ignore the mic pre section of the 1084.and the area these faults can be in looks very isolated....

 

[no-fi]

got it! ended up using the build guide to work out what areas of the board were what general block, and that was easy enough to use alongside the original 1084 schematics... I traced through a signal... then after a bit of re-soldering all around the 284 section for the H/L EQ bands, it all came good.

I was really loving the sound of this EQ with synths just before, and I'm having fun with rightmark audio analyzer now, looking at the EQ curves and soft vs hard bypass. Back to synths again soon, I think.

 

[Bluzzi]

got it! ended up using the build guide to work out what areas of the board were what general block, and that was easy enough to use alongside the original 1084 schematics... I traced through a signal... then after a bit of re-soldering all around the 284 section for the H/L EQ bands, it all came good.

I was really loving the sound of this EQ with synths just before, and I'm having fun with rightmark audio analyzer now, looking at the EQ curves and soft vs hard bypass. Back to synths again soon, I think.

Another "yay" !

I didn't know it would be good on synths too! I didn't try it so what do I know!

Cheers

Jim

 

[[email protected]]

Hey Colin and Bluzzi,
I have finally completed my two unit build using the gain resistor values Colin came up with. here are the results for an 11 position gain switch. The result is fabulous.
Pos 1 -18.4db
Pos 2 -14
Pos 3 -10.4
Pos 4 -6.5
Pos 5 -2.5
Pos 6 (center) +1.6
Pos 7 +5.5
Pos 8 +9.4
pos 9 +13.4
Pos 10 +17.4
Pos 11 +21.4
Both units are back in service and I am declaring the project complete.
Bluzzi, thanks for a great project!

 

[Bluzzi]

Thanks for posting Bruce. These are fantastic EQs even with a 7 step gain switch as per original. I'll add these values with the ones I came up with and let builders choose from the 3 choices.

The best part of building this project is to have music flowing through it. Hope you have many years of enjoyment with them.

Cheers

Jim

Hey Colin and Bluzzi,
I have finally completed my two unit build using the gain resistor values Colin came up with. here are the results for an 11 position gain switch. The result is fabulous.
Pos 1 -18.4db
Pos 2 -14
Pos 3 -10.4
Pos 4 -6.5
Pos 5 -2.5
Pos 6 (center) +1.6
Pos 7 +5.5
Pos 8 +9.4
pos 9 +13.4
Pos 10 +17.4
Pos 11 +21.4
Both units are back in service and I am declaring the project complete.
Bluzzi, thanks for a great project!