Poor Man's Pultec EQP1-A Build Support Thread

[MatthisD]

Thanks MatthisD. I think that I'm just over thinking it. That was a stupid mistake on my part 

On the Low board it would be R3=60K (for using U.S. value pots) and jumper R1 & R2?

I had asked this question earlier - Is it better to use two capacitors per frequency to get the necessary value or are two areas provided to use 2 caps to get an odd value (like a value you might not be able to find in 1 cap)?

No problem, thats right for the Lo PCB.

You can see below the capacitor values and choose for yourself whether to use 1 or 2 for each frequency.
http://www.ianbell.ukfsn.org/pics/CapValues.pdf

 

[wave]

Thanks MatthisD. I think that I'm just over thinking it. That was a stupid mistake on my part 

On the Low board it would be R3=60K (for using U.S. value pots) and jumper R1 & R2?

I had asked this question earlier - Is it better to use two capacitors per frequency to get the necessary value or are two areas provided to use 2 caps to get an odd value (like a value you might not be able to find in 1 cap)?

No problem, thats right for the Lo PCB.

You can see below the capacitor values and choose for yourself whether to use 1 or 2 for each frequency.
http://www.ianbell.ukfsn.org/pics/CapValues.pdf

Thanks!
I have downloaded this. I was asking as I want to use some different frequencies on the hi section of the eq. So I'm assuming that it's best to get the value closest to what is needed whether it be achieved with one cap or two.
I appreciate all your help! I'm starting to get it a little more.

 

[wave]

So, if I'm using the US standard 5K, 50K, 500K pots and a 60K for lo cut R3 do I need to change out the Hi Boost R1 and Hi Cut R2?

Dave

 

[MatthisD]

Hi Dave, check the magic .xls file on page 2, it will give you the capacitor values for your pots.
Matt

 

[wave]

Hi Dave, check the magic .xls file on page 2, it will give you the capacitor values for your pots.
Matt

MatthisD,
Thanks for the reply. I have used the capcalc.xls to get the cap values. My question was about the resistor values for Hi Boost R1 (4K7) and Hi Cut R2 (470R). I'm assuming that since they aren't on the capcalc.xls as an value that changes when using the US pots their values stay the same.

Dave

 

[ruffrecords]

So, if I'm using the US standard 5K, 50K, 500K pots and a 60K for lo cut R3 do I need to change out the Hi Boost R1 and Hi Cut R2?

Dave

Probably not. These resistors are designed to set the the maximum boost/cut that can be applied, ensure the input impedance does not drop significantly below 10K ohms and set the frequency at which the the cut and boost response begins to shelve. As such they are not critical but since you have increased the value of all the pots by 6.4% you could increase these two resistors by the same amount to maintain the same ratios.

Cheers

Ian

 

[funkymonksf]

I'm having a hard time understanding the psu pcb for the tube gain stage. Now I understand the bom list Ian offered in the first post, but I am unsure where the connections are on the pcb, as in where do I connect the psu to the tube pcb? Is it the 75v that is b+ and the heater is heater and the unmarked square is the ground?

ALSO..what are people in north America using for psu transformers? If i am correct we need a 120ac to 250vac 25ma & 6.3vac 1.2a? If I found a tranny with higher amps is that okay or will I need to modify my values.? Anyone?

Thank you,
Brice

 

[funkymonksf]

Would this work or is there a cheaper option? http://angela.com/hammondpowertransformer269ax.aspx

 

[ruffrecords]

I'm having a hard time understanding the psu pcb for the tube gain stage. Now I understand the bom list Ian offered in the first post, but I am unsure where the connections are on the pcb, as in where do I connect the psu to the tube pcb? Is it the 75v that is b+ and the heater is heater and the unmarked square is the ground?

Sorry, this is my fault. I did not use a consistent annotation thoughout. You need to tie up the:

tube gain make up stage circuit diagram http://www.ianbell.ukfsn.org/pics/PMTGMsm.jpeg
with the system diagram http://www.ianbell.ukfsn.org/pics/EQSystem.png
and the PCB as follows:

Point A on the circuit corresponds to point A on the system diagram and to pad Pout on the PCB
Point B on the circuit corresponds to point B on the system diagram and to pad Pin on the PCB
Pad PG on the PCB is the local ground connection for Pin and Pout and should be used for the screens of the cables going from Pin and Pout to the EQ  bypass switch.

Point C on the circuit corresponds to point C on the system diagram and to pad In on the PCB
Pad 1G on the PCB is the local ground connection for the screened cable that connect Pad In to the EQ bypass switch and then on to the output of the equaliser itself.

The HT+ on the circuit diagram connects directly to the HT pad on the PCB
The  connections labelled heaters connect directly to the pads labelled  H1 and H2 on the PCB.
The Pad labelled ** on the PCB is the tube gain make up start earth point and should be connected directly to the 0V of the power supply as shown on the circuit diagram.

Hope that clears things up a bit.

ALSO..what are people in north America using for psu transformers? If i am correct we need a 120ac to 250vac 25ma & 6.3vac 1.2a? If I found a tranny with higher amps is that okay or will I need to modify my values.? Anyone?

Thank you,
Brice

Higher output amps is OK, the circuit will just take what is needs and no more.

As to what to use in the US I am sure someone asked this before and they found a reasonably priced toroidal transformer that would be ideal for the job but at the moment I cannot remeber the make.

Cheers

Ian

 

[ruffrecords]

Would this work or is there a cheaper option? http://angela.com/hammondpowertransformer269ax.aspx

Yes, that would work but as I mentioned in my other post I think there is a cheaper/smaller toroid that will do the job.

Cheers

Ian

 

[wave]

As to what to use in the US I am sure someone asked this before and they found a reasonably priced toroidal transformer that would be ideal for the job but at the moment I cannot remeber the make.

Cheers

Ian

I had asked about using this transformer in one of my many emails to Ian

http://www.antekinc.com/details.php?p=638

Dave

 

[ruffrecords]

As to what to use in the US I am sure someone asked this before and they found a reasonably priced toroidal transformer that would be ideal for the job but at the moment I cannot remeber the make.

Cheers

Ian

I had asked about using this transformer in one of my many emails to Ian

http://www.antekinc.com/details.php?p=638

Dave

That's the one!! I knew it began with an A.

Cheers

Ian

 

[funkymonksf]

Thank you both of you!

Dave can you guide me in how you wired the antek transformer for us voltages? I see it has 2x115v primary. I also noticed it only provides 240v, is that enough?

Thanks again

 

[ruffrecords]

240V is plenty.

Cheers

Ian

 

[wave]

Thank you both of you!

Dave can you guide me in how you wired the antek transformer for us voltages? I see it has 2x115v primary. I also noticed it only provides 240v, is that enough?

Thanks again

Sure. What kind of IEC inlet are you using? Is it one with a built in fuse?
EDIT: You just have to tie the 2 red wires together and hook them to the "hot" AC in and the 2 black wires hook to the "cold" AC in. If you tell me what IEC inlet you're using I'll make you a diagram
Dave

 

[funkymonksf]

Thank you! It's just a standard 3 prong north American type and I have a separate fuse holder. I'm sure the diagram will help alot of people. Much appreciated!

Brice

 

[wave]

Here you go

 

[funkymonksf]

I'm sorry keep asking questions, but I'll never learn if I dont. Would you mind making a diagram for hooking up the secondary leads to the psu pcb? I just don't know what to do with the extra wires and voltages ie there are two 6.3v. All help is much appreciated!

Brice

 

[wave]

I'm sorry keep asking questions, but I'll never learn if I dont. Would you mind making a diagram for hooking up the secondary leads to the psu pcb? I just don't know what to do with the extra wires and voltages ie there are two 6.3v. All help is much appreciated!

Brice

Brice,
I'm more than happy to make you a diagram. I didn't get a PSU PCB from Ian as he was out of them. Send me an email so I can send you a pic of what I think the PSU PCB looks like as I don't know if Ian wants me to post a pic of his PCB in here (he sent me a PSU PCB pic in an email and I want to see if it's the one you're using.

email: wave(dot)audio(at)gmail(dot)com

Dave

 

[funkymonksf]

If it is the one he told you of it is the same with 470uf values for the 4 big caps and it needs some diodes of the number 1N4608 or something alike. Any way I'm sure it is the same. My email is Brice**perusse at hotmail dot com. No spaces between words. So if you have an idea any simple diagram regardless of psu pcb would help, mainly I simply have no clue what to do with the extra leads and voltages. Do I join them to the same co nection as the other or cut them and seal them? I don't know but I appreciate your effort.