REDD EQ, Helios 69 and Dick Swettenham

[Junction]

nice work Ian, sounds vintagely awesome 

 

[jplebre]

HOLY!
Like.... where's the "really like" button?

 

[bruce0]

Ian, with custom inductors can I use the Universal EQ board to make this EQ?  I guess I wouldn't get a dip?  I have taken a look at the schematic but I am a little confused by schematic style (I was introduced to electronics after paper!).

Anyway, how universal is the universal, and is it a different animal from this?

 

[ruffrecords]

Ian, with custom inductors can I use the Universal EQ board to make this EQ?  I guess I wouldn't get a dip?  I have taken a look at the schematic but I am a little confused by schematic style (I was introduced to electronics after paper!).

Anyway, how universal is the universal, and is it a different animal from this?

It's hard to draw the universal EQ in any kind of normal schematic style simply because it is a collection of parts that can be put together in lots of different ways. However, looking at the PCB schematic I think I could draw a new version of that which gives a better idea of how the parts could fit together. I am in the middle of writing up how to work out the RC values and I think it would be a good idea to include a description of how it all basically fits together. Having said that, it is still a collection of circuits blocks and the EQ you make with it is limited only by what you can build with these parts. I don't want to say 'this is how it all goes together' and have people think that is the only way it can be built.

Having said that, you probably could build the REDD EQ using the universal EQ PCB but it would be a bit of a bodge.  The switching on the REDD EQ is rather unique so many of the components would have to be mounted directly to the switches. If you really want to try the REDD EQ I would be happy to send you one of the prototype PCBs free of charge - it just needs a couple of links adding under the PCB plus the brilliance boost inductor needs to be glued on upside down and wired in by hand.  A lot less work than modding the universal EQ PCB.

Cheers

Ian

 

[bruce0]

Thanks! Sent postage via paypal with my address. 

Prototype would be great!  After all what is DIY without straps and trace cuts anyway?  And the inductor is no problem I am building my own - I will build brilliance as RM8 like chrion.

I will order some switches and build some inductors.
Looking at schematic "shorting MBB" would transition quieter on Brilliance boost/cut, wouldn't it?

FYI… Neither Mouser nor Digikey stock the EPCOS inductors. Farnell/Element 14 charge a "special" to ship those inductors to US. I ordered some axial Fastron VHBCC series ones Equivalent Q and current Current, slightly higher DCR and a bit longer case. Do you think these would work as well?


Mouser Part          MFG    Inductance  Imax  DCR    Min Q

434-VHBCC-102J-01 -  Fastron        1mH  400mA  4.2    70
434-15-222J -        Fastron      2.2mH  250mA  10    65
434-VHBCC-332J-01 -  Fastron      3.3mH  220mA  12    50
434-VHBCC-103J-01 -  Fastron      10mH  120mA  40    60


http://www.fastrongroup.com/image-show/25/VHBCC.pdf?type=Complete-DataSheet&productType=series

On Uni-EQ - Thank-you … I finally get it, the sections are building blocks... they don't connect.  (I looked at the boards and they really don't  :  Light dawns on Marble Head!)

 

[ruffrecords]

@Bruce,

The Fastron types look pretty close to the EPCOS. DCR is only about 10% higher and Q and current rating are fine so I would say they will be OK.

RM8 core will be fine. The VTB9044 inductor I use is also on an RM8 core.

MBB as a rule should be quieter but I used a BBM on the prototype (Lorlin) and I could not detect any switch clicks on the test recording.

I sent you an email asking for your shipping address because it did not come through with the Paypal payment. Once I have that I can ship your PCB.

Cheers

Ian

Cheer

 

[ruffrecords]

I have checked the new inductor footprint and it looks fine. I have made some other mods to the PCB layout such as adding provision for a series input resistor if a low  impedance source is used, added the usual PAD circuit and a couple of extra mounting holes. I have also spread out the capacitors in the treble boost/cut circuit to allow sightly larger types to be fitted.

I have updated the assembly instructions with the final component values and added the new ones:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/EzTubeMixer/REDDEQ/AssyInsV2.pdf

Cheers

Ian

 

[Strawtles]

Great work Ian!

 

[Gearsix]

Hello Ian, do you think to add this pcb in your emporium?

 

[ruffrecords]

Hello Ian, do you think to add this pcb in your emporium?

Yes, I will. The V2 PCB layout is now done. I just need to check it one more time before committing to manufacture. I expect to place the order later this week with PCBs arriving a couple of weeks after. PCB price will be around 11GBP.

Cheers

Ian

 

[Gearsix]

A little more expensive than the Helios?

 

[ruffrecords]

A little more expensive than the Helios?

Correct. The Helios I got right first time (apart from a very minor silk screen error). The REDD EQ needs a re-layout so I have to pay tooling charges again. Just trying to recover my costs. I have some of the original prototype PCBs which will work perfectly well if you are prepared to make the necessary mods to correct the errors.  You can have one for the cost of shipping if you wish.

Edit. What the hell. I was never in this for money. I'll keep the REDD EQ price the same as the Helios.

Cheers

Ian

 

[ruffrecords]

I have ordered the V2 PCBs for the REDD EQ. Should be here in a couple of weeks.

Cheers

Ian

 

[ruffrecords]

You may remember that the REDD EQ is based on the topology of my Helios 69 EQ design- in fact the first version was little more that a Helios with a switched attenuator for the boost/cut. For some time I have been thinking about a mastering EQ and the Helios lends itself quite well to modifying into one as it already has a stepped Hi boost/cut. From the REDD EQ work I worked out how to step the Helios mid boost/cut (and eliminate the boost/cut switch) and the bass is quite easy to convert to a switched pot.

So, I have put together a document that shows how to work out the resistor values for stepped switching of the Helios mid boost/cut and any similar attenuator based EQ as well as how to mod the Helios bass boost EQ to stepped operation. The mods are quite simple so the existing PCBs can be used. You basically replace the two pots with stepped switched and disable the cut/boost and EQ in/out switches.

Cheers

Ian

 

[Sleeper]

Hi Ian,
You do not fool around do you :-*



You write that the large inductor may have significant resistance that one should " measure the dc resistance of the inductor and subtract this value from the value of the resistor connected to the input."

This would be the 1864ohm resistor. Yes ? 

I've got some switches to draw up

 

[ruffrecords]

Hi Ian,

This would be the 1864ohm resistor. Yes ? 

I've got some switches to draw up

Yes, that's the one.

Cheers

Ian

 

[Sleeper]

I'm doing a bit of shopping for switches on my downtime today.
I'll need some quiet time to diagram that switch. 

For the benefit of everyone who's following the thread and gets a chance to look at the PDF
I'll ask for clarification on some things as I move along.

The stepped cut boost (for 12steps each of cut and boost) requires 2 decks 24 poles right? 
The ELMA at the audiomaintenance store is 66GBP
OTOH there are a lot of chinese 2p24T MBBs on ebay for cheep.  I might go there.

where did you get the 2P12W series71 (2 gang switch)?
I can't find that one anywhere in the US, although I can special order at Digikey.
audiomaintenance has a 1P12W (1gang) and a 3p12w (3gang) and the alternative would be to re-assemble those 2 into a pair of 2gang switches.

Thanks
Kelly

 

[ruffrecords]

@Kelly

The stepped cut boost (for 12steps each of cut and boost) requires 2 decks 24 poles right?

Yes, it you want to do this on the mid band of the REDD EQ. To do it on the Helios mid band requires only a 1 deck 24 pole switch.

where did you get the 2P12W series71 (2 gang switch)?

I got them on special order via a UK distributor. I could not find them anywhere either.

Cheers

Ian

 

[Sleeper]

Have you shipped many of those Helios boards to the US?
Maybe I'll see if Hairball or Classic API would be interested in stocking up on a few... they both carry the 1p12
Do you recall what the minimum was?

1 Deck for the Helios mid...  aaahh  OK  glad I asked
I've had a few glances at the drawing, enough to confuse myself.
I'll have to draw it when I can focus.

Kelly

 

[bruce0]

I got my switches at Digikey, expensive but in stock.