Poor Man's EQP1A (+MID) Mark 2

[mus1k_freak]

Looks great ian! Count me in for 2

 

[ruffrecords]

Hi Ian,
  i'll probably take two. It just looks so easy to build! Does the guy making the inductors plan to make some for the Helios eq as well?

Regards,

Pierre

I don't know his long term plans.  Both the Pultec and Helios EQs use the VTB9042 so to complete the Helios all that is needed is the bass boost inductor.

Cheers

Ian

 

[ruffrecords]

I finished testing the board. I fitted the correct caps for the inductor based hi boost and it all seems to work. I had to tweak the 16K capacitor to 680pF to get it to peak at the right frequency but other than that it all seems OK. Here is a pic of the PCb with all the pots hanging off on flying leads:

https://www.dropbox.com/s/se5v2jqqhbrpwy5/flyingpots.png?dl=0

The PCB is laid out for 3 pin Molex KK connectors for each of the pots but you can hard wire to the pads as I have done in the prototype/ All the pots connect to the PCB in exactly the same way - the square PCB pad is the counter-clockwise end of the pot, the middle pad is the slider and the third pin is the clockwise end of the pot. I have used regular twin screened mic cable to wire the pots to the PCB. There are 6 positions on the PCB for stand offs so you can mount the PCB back from the front panel instead of directly on the Lorlin shafts. This gives you enough room to get the pots in between the PCb and the front panel for a compact arrangement of controls. You don't have to do this. You can mount the PCB using the Lorlin shafts and fix the pots to the front panel outside the PCB area.

Here is the final schematic:

https://www.dropbox.com/s/taricbromzz4ejv/Lorlin3BandPultecEQ.png?dl=0

I plan to order PCBs on Monday. In the meantime I will start putting together the DIY assembly documentation.

Cheers

Ian

 

[prescott]

Hello!

I will offer the inductors.
For the first try I will offer for this project, but later I may make different kinds.
All depends on the interest.

So please tell me first if you are interested in inductors for this project.
PM me, and I will count how many you guys need, or you can reply to this topic.

I think I will wait 2-3 weeks for the first order, so let's start counting!

Peter

 

[Joechris]

Hi, I would like a couple of PCBs and the inductors. On the schematic it looks like the largest bass boost cap is linked to
the bass boost pot?  Should it be the smallest cap that is linked?.. so its always in parralell with the others?

 

[ruffrecords]

Hi, I would like a couple of PCBs and the inductors. On the schematic it looks like the largest bass boost cap is linked to
the bass boost pot?  Should it be the smallest cap that is linked?.. so its always in parralell with the others?

Well spotted. That is actually an error on the schematic; that link should not be there. I will correct it and repost the schematic.

Cheers

Ian

 

[Humner]

I would be keen on 4 boards + inductors to suit

 

[rock soderstrom]

Hi, I am in for 4 boards and  inductors. Thanks!

 

[kvothe]

In for 4 boards and inductor sets, thank's Ian!

 

[prescott]

Thanks for the interest about the inductors.
The price will be 10 pounds + shipping each.

In 2-3 weeks time I will open a white market store, but until that time I will count the interest here.

Regards
Peter

 

[ruffrecords]

I ordered the first batch of PCBs yesterday. Should be here in a couple of weeks. In the meantime, here is the first draft of the assembly instructions:

https://www.dropbox.com/s/0qnhl32g6th33yw/AsemblyInstructions.pdf?dl=0

Cheers

ian

 

[shot]

As I've already wrote earlier, I'm in for two pcb's
That would require 4 inductors (2 per channel) right?
Thanks!

 

[ruffrecords]

As I've already wrote earlier, I'm in for two pcb's
That would require 4 inductors (2 per channel) right?
Thanks!

Correct. Each EQ uses one VTB9042  or equivalent for the the high boost and one VTB9050 for the mid boost/cut. You can also  build the original poor man's version of the high boost without using an inductor so then you just need one for the mid.. Details are in the assembly documentation.

Cheers

Ian

 

[peterc]

Hi Ian

I'd be in for a pair, at least.

Peter

 

[prescott]

The prototype

 

[electric_diaries]

I would be interested in some inductors when they become available!

 

[ruffrecords]

Updated, and hopefully final, version of the schematic is here:

https://www.dropbox.com/s/taricbromzz4ejv/Lorlin3BandPultecEQ.png?dl=0

Cheers

Ian

 

[shot]

Correct. Each EQ uses one VTB9042  or equivalent for the the high boost and one VTB9050 for the mid boost/cut. You can also  build the original poor man's version of the high boost without using an inductor so then you just need one for the mid.. Details are in the assembly documentation.

Cheers

Ian

I bet you have built both with and without inductor on HF!
What would be your impression comparing those two?
Is the difference audible right away?



Luka

 

[ruffrecords]

Correct. Each EQ uses one VTB9042  or equivalent for the the high boost and one VTB9050 for the mid boost/cut. You can also  build the original poor man's version of the high boost without using an inductor so then you just need one for the mid.. Details are in the assembly documentation.

Cheers

Ian

I bet you have built both with and without inductor on HF!
What would be your impression comparing those two?
Is the difference audible right away?



Luka

They sound quite different. The inductor version produces a peaking response just like the mid section. In fact its frequencies overlap a significant portion for the mid  band range. The peaking response is great for emphasising a defined range of frequencies and if you use it on a mix you can emphasize individual instruments for example. The RC hi boost is a shelving type so it emphasizes a much wider range of frequencies which is useful for adding 'air' to  a mix for example.

Cheers

Ian

 

[shot]

They sound quite different. The inductor version produces a peaking response just like the mid section. In fact its frequencies overlap a significant portion for the mid  band range. The peaking response is great for emphasising a defined range of frequencies and if you use it on a mix you can emphasize individual instruments for example. The RC hi boost is a shelving type so it emphasizes a much wider range of frequencies which is useful for adding 'air' to  a mix for example.

Cheers

Ian

Ian, this is very valuable info!!! Thank you!

And since we're at the topic of sound, could you tell us is, in this design, the tube makeup gain too coloured for mastering jobs, or just gentle and transparent enough not to impose too much of its personality?
I would certainly go for tube output stage, but I'm exploring  options since I'd like to build it as a dual mono unit so it can be used in mastering also...
I know it's too subjective question... but I had to ask... sorry  8) ???

Luka