Poor Man's Pultec EQP1-A Build Support Thread

[gemini86]

your cap values may need adjustment, but yes.

 

[Hank Dussen]

is possible to use:
5k instead 4k7
50k instead 47k
500k instead 470k?

As Gemini says: cap values will be slightly different. See the spreadsheet Ian posted halfway the previous page.

 

[ruffrecords]

Here are the results of my measurements of the HF response of the poor man's EQP1-A. I made them some time ago but lost them. Fortunately I found them this morning. As expected there is a small broad bump with max boost and cut

Cheers

Ian

 

[dirtyhanfri]

Hi, I bought a pair of Lorlin 6 pos. switches, well, actually 12 pos., but you can limit them to 6 positions.
Are those usable on this project?

Also I`ve noticed that the switches doesn`t have a pin in "C", just a hole, should I open them and solder a little piece of wire to it or somenthing like that?

And L1 will be fine just making a bridge?

Thanks

 

[dirtyhanfri]

Another question...

The Pots have to be normal or reversed?

 

[ruffrecords]

Hi, I bought a pair of Lorlin 6 pos. switches, well, actually 12 pos., but you can limit them to 6 positions.
Are those usable on this project?

Probably not. You need two pole 6 way switches. I think the ones you have are single pole 12 way

Also I`ve noticed that the switches doesn`t have a pin in "C", just a hole, should I open them and solder a little piece of wire to it or somenthing like that?

Again, that is most likely because they are single pole 12 way types. I am afraid you have purchased the wrong type of switch.

And L1 will be fine just making a bridge?

Yes.

Cheers

Ian

 

[ruffrecords]

Another question...

The Pots have to be normal or reversed?

Normal.

Cheers

Ian

 

[dirtyhanfri]

Thanks ruffrecords

Surely I`ve bought the wrong switches  :-\ well, trial and error way

Another thing, I understand in the low pcb C1 & C1 A are for 20 Hz Cut, and C12 & C12 A are for 20Hz Boost, and so on, am I ok or wrong? (Actually I Think I`ve populated one of the low boards mirror`ed)

 

[ruffrecords]

Another thing, I understand in the low pcb C1 & C1 A are for 20 Hz Cut, and C12 & C12 A are for 20Hz Boost, and so on, am I ok or wrong?

Which side you use for boost and which for cut is entirely up to you. However, the wiring schematic showing how the switch PCBs are wired together (which I have now added to the first post in this thread) does assume the Lo Cut capacitors start at the C1 position. These are fitted from C1 to C6. The Boost capacitors then start from C7 (for 20Hz) and continue up to C12.

I have also added a link to the PCB layout to the first post in this thread.

Cheers

Ian

 

[MatthisD]

I can't decide on whether to build dual mono unit or a stereo unit. For a stereo unit with a single set of controls I believe this monacor switch for frequency selection should work; http://www.electricalmate.co.uk/proddetail.php?prod=11480

Also for the Boost/Att control it seems that, from what I can gather log pots(mono or dual) will not match closely enough for decent stereo operation in which case a 2pole/12position stepped switch like this perhaps would work; http://www.electricalmate.co.uk/proddetail.php?prod=11470

I'm sure most people would prefer dual mono units, but I might sacrifice individual channel usage for the convenience of simultaneous control.
If you can recommend alternatives to the switches above please do.

Matt

 

[ruffrecords]

I can't decide on whether to build dual mono unit or a stereo unit. For a stereo unit with a single set of controls I believe this monacor switch for frequency selection should work; http://www.electricalmate.co.uk/proddetail.php?prod=11480

Yes, you need a 4 pole 6 way and that switch fits the bill and it has a keen price too.

Also for the Boost/Att control it seems that, from what I can gather log pots(mono or dual) will not match closely enough for decent stereo operation in which case a 2pole/12position stepped switch like this perhaps would work; http://www.electricalmate.co.uk/proddetail.php?prod=11470

For repeatability, stepped pots are preferable and for stereo matching they are almost essential. 12 positions should be plenty. Of course there is a one pole 12 way version of the Lorlin for anyone who wants to do single channel switched pots.

Cheers

Ian

 

[dirtyhanfri]

For repeatability, stepped pots are preferable and for stereo matching they are almost essential. 12 positions should be plenty. Of course there is a one pole 12 way version of the Lorlin for anyone who wants to do single channel switched pots.

Cheers

Ian

How could I calculate the resistor values for 12 pos. pot? What`s the formula?

Also I have some non shorting switches, how bad would it be to use them?

Thanks


D.Hanfri

 

[dirtyhanfri]

Ok, I`ve found the resistors value for the stepped switches in the second post..., sorry for the question

I`ve been also buying parts for the psu and I got 4 IN4007 instead of IN5007. The guy at the shop told they`re equivalent, but I`d like to be sure.

And for the 47pF cap, it`s only 63v. will this work or should I get a 100 v. cap?

Thanks

 

[ruffrecords]

Ok, I`ve found the resistors value for the stepped switches in the second post..., sorry for the question

I`ve been also buying parts for the psu and I got 4 IN4007 instead of IN5007. The guy at the shop told they`re equivalent, but I`d like to be sure.

1N4007 diodes will be fine.

And for the 47pF cap, it`s only 63v. will this work or should I get a 100 v. cap?

That should be 47uF (microFarads) - sorry that's my poor writing. It does need to be 100V working as the voltage across is is approximately 75 volts so a 63V will not do. The other capacitors in the PSU are 220 microFarads. They need to be at least 400V dc working types.

Cheers

Ian

 

[dirtyhanfri]

Great.

Thanks!

I`ll post some pics later

 

[dirtyhanfri]

Should the caps of the psu be electrolityc?

The only electrolityc I got is the 100uF and I put the - leg down as we look the schem, is this ok or not?

And a Pair of pics.

Thanks to everyone sharing info on this project and to ruffrecords for designing it.

 

[dirtyhanfri]

The tube gain stage (waiting for tubes & sockets)

 

[ilfungo]

sorry dirtyhanfri
where I can find the tube gain stage PCB?
Thanks

 

[dirtyhanfri]

sorry dirtyhanfri
where I can find the tube gain stage PCB?
Thanks

I got them from ruffrecords, but don`t know if there`s any left....

 

[ruffrecords]

Should the caps of the psu be electrolityc?

The only electrolityc I got is the 100uF and I put the - leg down as we look the schem, is this ok or not?

Yes, all the PSU caps are electrolytic.  In all cases the - leg is connected to 0V. The 220uF from the cathode of the bottom triode to ground is also electrolytic - it should be 50V working type or better.

The 4.7uF from the top triode cathode to the transformer is NOT an electrolytic. It should be a 450V working metal film type.

Cheers

Ian