G-PULTEC problems, please help!

[Harpo]

..I'm talking about ECC88 Tubes. In the schematic there are two of them, but the PCB layout just has space for one...

Did you try to Google for 'ECC88 datasheet' ? 

 

[fatheaddrummer]

Haha ;-) Ok, got it!

Thank you! ;-)

Best,
Christian

 

[ding]

I hand wound and inductor for my first one but for my second one I decided to try out an inductor that David from Cinemag agreed to make for me for a very reasonable price. David is an awesome dude! He might put it up on the Cinemag website. Anyways, I was trying to figure the best way to drill up and attach this little guy and I did not know whether to post in the Lab or here but here seemed to be the most obvious place. I decided on 3 options but I can't figure out the best recourse or if there is a better option 4.

Option 1 - Drill all the holes for the pins on the PCB. Attach the inductor on the "pads side" with the pins facing the components. Use a circuit pen to draw some pads to attach the 4 mounting pins to the PCB. I don't know if the pen is necessary or if I can just hold the inductor mounting pins with solder. Solder wires from the pins to the correct pads on the PCB. Lead wires will be short but thats a lot of drilling and I dont have a press.

Option 2 - Drill a single hole on the PCB. Attach the inductor on the "pads side" with a single nylon screw by the center with the pins facing away from the front panel. Solder wires from the pins to the correct pads on the PCB. Lead wires will be a little longer but only 1 hole to drill.

Ooption 3 - Use a breadboard to attach the inductor to. Mount the breadboard on the bottom of the chassis. Solder wires from the pins to the correct pads on the PCB. Lead wires will be a lot longer but the PCB will remained untouched and in case of drill accident unharmed.

Any thought on the best option? Here is option 1.

 

[ding]

Here is option 2. Option 3 is obvious. I will drill on the green marks.

 

[APL]

Don't know if its best option as I have'nt tested it, but I'm going for option 3.

I have built a separate plug in  board as I am initally trying cheaper inductors with the intention of replacing in future with more expensive Sowter on another plug in board.

I did wonder about problems with longer cables,might use screened cables. One advantage  you could possibly move inductors away from interference. I was thinking of mounting them in a OEP mu metal transformer case.

 

[dipfrik]

Finished two of them over holidays. What a nice sounding and easy build!
Need to A-B-C'ing them against the "B" a Drip V2 and the "C" a Recproaudio Kit (PTP pain  8))

Cheers, Sven

 

[sedit1]

Finished two of them over holidays. What a nice sounding and easy build!
Need to A-B-C'ing them against the "B" a Drip V2 and the "C" a Recproaudio Kit (PTP pain  8))

Cheers, Sven

Nice build, please report back when you have done the A-B-C

 

[berkleystudios]

Finished two of them over holidays. What a nice sounding and easy build!
Need to A-B-C'ing them against the "B" a Drip V2 and the "C" a Recproaudio Kit (PTP pain  8))

Cheers, Sven

where did you get those cases? look great with your knobs

 

[berkleystudios]

never mind found them

 

[berkleystudios]

okay I have a pair on the way (should be here within the week hopefully) and I have several BA283 cards sitting around doing nothing. So I wanted to implement them into my G Pultec if that was possible.

attached is just a modified schematic and block diagram. would this be where I would need to attach it to replace the SRPP stage? and would I need to modify the power supply because I would be replacing the tube stage?


( if I should have started a new thread for this, my apologies. Just let me know and Ill remove this post)

Thanks guys!

 

[berkleystudios]

proposed schematic with modded power supply

 

[gyraf]

What gain do you have in BA283?

for 30VAC transformer, your storage electrolytic will need to be 50V (or at least over 42.5V)

 

[berkleystudios]

What gain do you have in BA283?

for 30VAC transformer, your storage electrolytic will need to be 50V (or at least over 42.5V)

should be about 34db of gain. I havent finished the cards yet so i cant say for certain.


good to note. can you tell me why? (curious because I was told just any voltage rating about the V i was working in.)

 

[Harpo]

proposed schematic with modded power supply

You don't want to connect the rectifier the way shown (shorting out the transformer).
The (too high) 30V transformer secondary is AC voltage that gets rectified to 30V*SQRT(2), ignoring the voltage drop in the rectifier giving out a 42.43VDC pk. AC mains voltage isn't a constant and might vary by +/-10% depending on location or time of day and the transformer secondary side will follow with same variation%. The 30VAC is the transformers secondary voltage at rated load and will be higher unloaded (lookup the regulation % at your transformers datasheet, maybe 15%). If AC mains is high and no load connected, this 42.43VDC pk might rise up to 42.43*1.1*1.15=53.67VDC pk and the cap between rectifier and voltage regulator has to be rated for at least this voltage. For a regulated 24VDC out, a 24VAC transformer secondary will leave enough headroom above the voltage regulators dropout voltage in a 10% low mains scenario, only requires 50V rated caps and keeps it way cooler as the differential voltage between input and output of your voltage regulator times current drawn is transfered to heat. Depending on gain/level and connected load impedance of the following piece of gear, a single BA283 may consume up to 150mA of DC power. Your PSU uses a full wave bridge rectifier (form factor K=1.8 ), so the transformer will need at least a VA rating of ((24V*0.15A DC consumption)+1.82W vreg.dissipation+~2W rectifier dissipation)*form factor 1.8=12.8VA. Good luck.

 

[berkleystudios]

proposed schematic with modded power supply

You don't want to connect the rectifier the way shown (shorting out the transformer).
The (too high) 30V transformer secondary is AC voltage that gets rectified to 30V*SQRT(2), ignoring the voltage drop in the rectifier giving out a 42.43VDC pk. AC mains voltage isn't a constant and might vary by +/-10% depending on location or time of day and the transformer secondary side will follow with same variation%. The 30VAC is the transformers secondary voltage at rated load and will be higher unloaded (lookup the regulation % at your transformers datasheet, maybe 15%). If AC mains is high and no load connected, this 42.43VDC pk might rise up to 42.43*1.1*1.15=53.67VDC pk and the cap between rectifier and voltage regulator has to be rated for at least this voltage. For a regulated 24VDC out, a 24VAC transformer secondary will leave enough headroom above the voltage regulators dropout voltage in a 10% low mains scenario, only requires 50V rated caps and keeps it way cooler as the differential voltage between input and output of your voltage regulator times current drawn is transfered to heat. Depending on gain/level and connected load impedance of the following piece of gear, a single BA283 may consume up to 150mA of DC power. Your PSU uses a full wave bridge rectifier (form factor K=1.8 ), so the transformer will need at least a VA rating of ((24V*0.15A DC consumption)+1.82W vreg.dissipation+~2W rectifier dissipation)*form factor 1.8=12.8VA. Good luck.

Thanks Harpo! that is quite a bit of info but I understand most of it! can you go over what the form factor is? that is new to me.

 

[Harpo]

Describes the efficiency of AC current/DC current ratio of the type of rectification used (full wave bridge, full wave bridge with center tap, full wave with center tap, full wave center tap with choke, halfwave, ...) as a result of the different current waveforms.
some simple explanation at http://www.amveco.com/Technical_Notes_3.htm
a little more in depth at http://www.visionics.a.se/html/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html

 

[berkleystudios]

Describes the efficiency of AC current/DC current ratio of the type of rectification used (full wave bridge, full wave bridge with center tap, full wave with center tap, full wave center tap with choke, halfwave, ...) as a result of the different current waveforms.
some simple explanation at http://www.amveco.com/Technical_Notes_3.htm
a little more in depth at http://www.visionics.a.se/html/curriculum/Experiments/FW%20Rectifier/Full%20Wave%20Rectifier1.html

Thanks!

 

[gyraf]

Pultec circuit needs some 20-23dB gain IIRC

 

[gimlay]

Hey diyers

I have a question about the lorlin switches. Im having a hard time getting mine into the board. Would it be ok if i opened up the holes on the board a little with a tiny file or screwdriver? Im worried obout breaking off on off the pins on the switch. I dont want to try and just jam that thing in there. I bought my boards from pcb grinder they seem pretty heavy duty but all the tracces are inside so its hard to know what the best approach is.

Thanks

Gabe

 

[gyraf]

Hi Gabe,

No problem in widening the holes a bit to better fit switches.

The only place you need to worry about this, is when you work on double-sided, through-plated pcb's - where there may be needed through-plating inside the pcb holes.

Jakob E.