baadc0de

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #40 on: November 10, 2011, 05:02:44 AM »
I have now done some work on a parallel resonant boost version. The table below lists for each frequency the simulated Q for the original cut,  for the series resonant boost (using the same L and C values) and for the parallel resonant boost (again using the same L and C values).
...

What about having a double rotary (either two separate or two deck) with two sets of capacitors and a switch to select which set to use?


ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #41 on: November 10, 2011, 07:01:47 PM »
I have now done some work on a parallel resonant boost version. The table below lists for each frequency the simulated Q for the original cut,  for the series resonant boost (using the same L and C values) and for the parallel resonant boost (again using the same L and C values).
...

What about having a double rotary (either two separate or two deck) with two sets of capacitors and a switch to select which set to use?

I had thought of using different L and C values for boost and cut and exploiting the fact that we have a 2 pole 6 way switch on the existing EQ PCB to to contain the two sets of capacitors (I am aiming for using the existing PCB rather than designing a special one just for mid cut/boost). Having two switches  is more expensive so we should aim to avoid it if possible. I feel bad enough about using the inductor for mid cut without adding extra switches too ;)

One thing we could do is accept the differences in Q between boost and cut caused by using the same LC values at each frequency. This is what the classic Helios Type 69 EQ does - and its cut Q is much higher than its peaking Q. The ratio between series cut Q and series peak Q is exactly 6:1 in the poor man's Pultec. So we could aim for a nominal Q of 1 for the boost which would give a nominal Q of 6 for cut. The advantage of this approach is that we potentially have 12 frequency settings. The other reason I think this is probably a good way to go is that the MEQ is designed to overlap with its peaking lo and hi EQ and so produce the classic Pultec bump. We don't need to do that at the Lo end because we already create the Pultec bump from simultaneous Lo boost and cut. We cannot do it at the Hi end because we have a shelving Hi EQ rather than a peaking one.

So, I'll warm up the calculator and work out a set of LC values on this basis. That's about as far as I think I want to go with the inductor and I want to return to thinking of other ways of doing mid boost/cut without using an inductor.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #42 on: November 12, 2011, 08:39:40 AM »
OK, here's a design for a mid boost/cut modification the the poor man's Pultec. It has a set of 12 frequencies, a boost/cut switch and needs an on/off switch. Detials in the attached pdf.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

rmaier

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #43 on: November 12, 2011, 10:05:12 AM »
PDF worked for me.
Thanks Ian. I have a feeling I'll be in touch again soon....
Do you have many eq boards left?

Ralph
"Even if you don't know where the destination is of the sounds that you originate, it's worth getting it right at the start." - Rupert Neve

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #44 on: November 12, 2011, 10:57:11 AM »
Do you have many eq boards left?

Ralph

Yes, I have quite a few left.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

rmaier

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #45 on: November 12, 2011, 12:51:07 PM »
Hahaha. In that case, please send me two more. Sorry about the frequent trips to the post office, but you'll have to stop being so generous with your work.

Cheers,

Ralph
"Even if you don't know where the destination is of the sounds that you originate, it's worth getting it right at the start." - Rupert Neve

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #46 on: November 13, 2011, 09:02:36 AM »
Hahaha. In that case, please send me two more. Sorry about the frequent trips to the post office, but you'll have to stop being so generous with your work.

Cheers,

Ralph

My pleasure Ralph and thanks for volunteering to be the first to try out the mod. I'll post your PCBs on Monday.


Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

erikb1971

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #47 on: November 16, 2011, 05:51:48 AM »
I am always a bit of a visual guy so... am I correct that with three boards it should be able to build something like the attachment?
We are getting way past relatively easy

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #48 on: November 16, 2011, 06:54:43 AM »
I am always a bit of a visual guy so... am I correct that with three boards it should be able to build something like the attachment?

The mid is switched from boost to cut rather than having separate boost and cut pots - you can do either but not both at the same time like you can with the hi and lo. So I envisaged the mid as one pot and one frequency switch plus a toggle labelled boost/cut. You could use separate pots for mid boost and cut but you would still need to switch between them.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

erikb1971

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #49 on: November 16, 2011, 03:37:16 PM »
see.. that is why I should have pictures :-)

so something like this or should it still have the on off switch?
We are getting way past relatively easy


MatthisD

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #50 on: November 16, 2011, 04:07:44 PM »
Yes you need the switch because;

"It also means that the
minimum boost is not quite no boost at all so I have included a switch in series with the pot to allow
the mid boost/cut to be switched right off"

see.. that is why I should have pictures :-)

so something like this or should it still have the on off switch?

erikb1971

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #51 on: November 16, 2011, 04:11:14 PM »
yeah I had read that.. that is why is was in there in the first place... somehow I thought I had mistaken that since I completely overlooked the cut/boost switch! Tnx!
We are getting way past relatively easy

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #52 on: November 16, 2011, 04:13:13 PM »
see.. that is why I should have pictures :-)

so something like this or should it still have the on off switch?

As Mathis said you need an on/off switch but you could incorporate it into the boost/cut pot if you wish.

I would  have the cut boost switch configured so UP id boost and DOWn is cut but that is just a personal prerefence.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

erikb1971

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #53 on: November 16, 2011, 04:18:07 PM »
aahh smart.. a three way switch!
We are getting way past relatively easy

erikb1971

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #54 on: November 16, 2011, 04:57:43 PM »
Ian, would you mind if I started a feeler to see how much interest there is in dedicated mid boards? I am definitely going to build a version with the mid, and incorporate it in another project, but I would feel a bit silly about adjusting the standard boards, having to buy extra standard boards and then you running out of them again...

If not, 4 standard boards for me please :-)
We are getting way past relatively easy

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #55 on: November 16, 2011, 06:09:26 PM »
Ian, would you mind if I started a feeler to see how much interest there is in dedicated mid boards?

That's fine by me. The modifications to the PCB layout will not be very hard. I assume you would want the inductor on the PCB as well. If there is enough interest I am happy to design such a PCB.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

gemini86

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #56 on: November 17, 2011, 01:15:41 AM »
I really like the ON-off-ON switch... keeps it clean...
- Rodney

"...you better call Kenny Loggins, 'cause you're in the danger zone."

baadc0de

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #57 on: November 17, 2011, 04:54:51 AM »
Ian, would you mind if I started a feeler to see how much interest there is in dedicated mid boards? I am definitely going to build a version with the mid, and incorporate it in another project, but I would feel a bit silly about adjusting the standard boards, having to buy extra standard boards and then you running out of them again...

If not, 4 standard boards for me please :-)

If there will be a mids board, I'm definitely in for 4

erikb1971

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #58 on: November 17, 2011, 05:45:42 AM »
feeler for the mid boards: http://www.groupdiy.com/index.php?topic=46575.0

@Baadc0de: noted you for four!

@Ian: would it be possible to use two mid boards and reserve one for boost and one for cut?
We are getting way past relatively easy

ruffrecords

Re: any ideas for adding a sweepable mid to the Poor Man's Pultec EQP1-A ?
« Reply #59 on: November 17, 2011, 12:38:31 PM »
@Ian: would it be possible to use two mid boards and reserve one for boost and one for cut?

Are you thinking of doing both mid  boost and mid  cut at the same time?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


 

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