Phantom and 24 for various oldies.... 2448 Power supply PCB!

[Igor]

Needed to rack some old junk, Neumann 695 EQ's and V476 pre's...
As well, friend built "1072" "clone" and needed a power supply.
After searching the web for normal solution, decided to make my own.

Requires 2x25V 15...50 VA toroid. VA depending on application;
for 2xV472 and 2x V695, 25VA more than enough.

48V and 24V grounds are separated-to have more wisdom with other
oldies like RCA modules etc.

24V can be adjusted for 20....30V.

Hi-res pictures, schematic-here:
http://s251.photobucket.com/albums/gg291/diy33609/2448/

BOM:

QTY VALUE              DEVICE             PARTS                                        
Bypass caps:
2   0.1UF           CAPACITOR CERAMIC X7R 50V 5MM PITCH             C4, C5                                        
2   0.1UF           CAPACITOR POLY 100V 7.5...10MM PITCH           C10, C12  
Diodes:                                  
6   1N4004         1N4004 ETC  1A 200..400V   diodes      D1, D6, D7, D8, D9, D10                      
4   1N5400, OR    MR854 ETC 3A FAST DIODE                D2, D3, D4, D5

Electrolitic caps:                                        
1   33...68UF 63-100V 5 MM PITCH LOW ESR     C13                                          
1   47....100UF 63...100V 5 MM PITCH LOW ESR       C20                                          
2   100U 35...50V 2.5 OR 3.5 MM PITCH LOW ESR     C6, C8                                        
1   100U  63...100V 5 MM PITCH LOW ESR      C7      
3   220...1000UF 100V   7.5 MM PITCH     C11, C15, C19                                
1   2200...4700UF 50...63V LOW ESR PITCH 10MM OR AXIAL,
UP TO 50MM LONG C14 (AXIAL PACHAGE MARKED C3)                                          

Resistors:                                        
2   196R                1/4W METAL FILM 1%       R1, R5  
1   47R  22...100R 1W CARBON OR METAL OXIDE 10%       R4
2   TBD                1/4W METAL FILM 1%       R3, R7

R7=7K32 FOR 48V, R3=3K57 FOR 24V

OR, USE R6=10K, R3=5K 25 TURN TRIMPOTS, TOP SCREW

IC's:
1   LM317                         IC1                                                                                                                
1   TL783                         IC2    

2X HEATSINKS

 

[ruffrecords]

I notice from the schematics that on the 48V supply you have decoupled the ADJ pin of the TL783. The Texas data sheet specifically recommends against doing this. Have I missed soemthing?

Cheers

Ian

 

[Igor]

I notice from the schematics that on the 48V supply you have decoupled the ADJ pin of the TL783. The Texas data sheet specifically recommends against doing this. Have I missed soemthing?

Cheers

Ian

Thanx for pointing on this, Ian.

Copy-pasted from TL783 datasheet:

bypass capacitors
The TL783 regulator is stable without bypass capacitors; however, any regulator becomes unstable with certain
values of output capacitance if an input capacitor is not used. Therefore, the use of input bypassing is
recommended whenever the regulator is located more than four inches from the power-supply filter capacitor.
A 1-mF tantalum or aluminum electrolytic capacitor usually is sufficient.

To short the long sentence: it _can_work without bypass capacitors....in other words, use them.

Interestingly, no word about 196R instead of 82R...anyway

and

Adjustment-terminal capacitors are not recommended for use on the TL783 because they can seriously
degrade load transient response as well as create a need for extra protection circuitry. Excellent ripple rejection
presently is achieved without this added capacitor.
Due to the relatively low gain of the MOS output stage, output voltage dropout may occur under large load
transient conditions. The addition of an output bypass capacitor greatly enhances load transient response and
prevents dropout. For most applications, it is recommended that an output bypass capacitor be used, with a
minimum value of:
Co (mF) = 15/VO
Larger values provide proportionally better transient-response characteristics.

But Adjustment-terminal capacitor IS used.

Reasons: by mean of constant (no fast transients, like motors etc) load, which are the microphones,
I care more about less _measured_ noise, than perfect transient response on rapidly changing load...
Protection diodes are on-board.

 

[tomas1808]

Igor, so a single PCB (with the correct toroidal) can power two +24v preamps? I am currently building two 1108 pres, is this able to power both units and also provide phantom for both channels?

Thanks!

 

[ruffrecords]

Hi Igor,

I understand your point about the cap on the ADJ pin for this application. I use a 10uF bypass at the output. I have not found an additional capacitor on the ADJ pin to be necessary. I have checked this out with a 70dB gain mic pre and there is no evidence of any phantom noise.

Have you made any comparative measurements with and without a capacitor on the ADJ pin?

Thanks for pointing out the 196R. A strange value. Care to explain?

Cheers

Ian

 

[Igor]

Igor, so a single PCB (with the correct toroidal) can power two +24v preamps? I am currently building two 1108 pres, is this able to power both units and also provide phantom for both channels?

Yes, this is the purpose of 2448 PS PCB.
BTW, it done with mind to power up old germanium modules with say -30V power supply as well, as many others...
The grounds are separated, etc...

Have you made any comparative measurements with and without a capacitor on the ADJ pin?

Thanks for pointing out the 196R. A strange value. Care to explain?

Aha. Some years ago played with TL783's and tried some combinations

 

[r2d2]

hello
only as further info
if R6 and R2 (trimmers) are placed
the R3 and R7 (TBD) are not needed ?
and a "bridge" have to be placed @ R3 and R7 ?
peace!

Resistors:                                        
2   196R                1/4W METAL FILM 1%       R1, R5  
1   47R  22...100R 1W CARBON OR METAL OXIDE 10%       R4
2   TBD                1/4W METAL FILM 1%       R3, R7

R7=7K32 FOR 48V, R3=3K57 FOR 24V

OR, USE R6=10K, R3=5K 25 TURN TRIMPOTS, TOP SCREW

 

[Igor]

hello
only as further info
if R6 and R2 (trimmers) are placed
the R3 and R7 (TBD) are not needed ?
and a "bridge" have to be placed @ R3 and R7 ?
peace!

No need to short. Use one of them: trim pot in case of adjusteble out,
fixed resistor for looong life (trimpots sometime going wrong after 3-5 years).

Or trimpot, or fixed value. NOT both together.

(BTW, if somebody watched the movie "In Bruges", there was an excellent joke about R2D2
Martin McDonagh is my second favorite now, after Alejandro Jodorowsky.

 

[Igor]

Hehe, no, no way, me and star wars? Completely anti! Cynicism, black humor, art-house -  yes.
Clerks, Addams Family, Jay & Silent Bob, from Russian writers- Pelevin, Aleshkovski, etc.
Sometimes in aestetic mode Nabokov and Jodorowski.

 

[jandoste]

Hehe, no, no way, me and star wars? Completely anti! Cynicism, black humor, art-house -  yes.
Clerks, Addams Family, Jay & Silent Bob, from Russian writers- Pelevin, Aleshkovski, etc.
Sometimes in aestetic mode Nabokov and Jodorowski.

No Andreï Tarkovski? lol lol

 

[Igor]

Yes, but.... Would you mind Beatles in your play list? No. But tell me somebody haven't grew up on this music

 

[r2d2]

....Addams family ?
...so funny ! ..expecially uncle "Fester" .. the scientist...  ;D

checked for parts "googling" around..
but the axial 4700-50/63v low esr , really not easy to find ,  
possible an alternative about ?
peace.                                                                                                      

Hehe, no, no way, me and star wars? Completely anti! Cynicism, black humor, art-house -  yes.
Clerks, Addams Family, Jay & Silent Bob, from Russian writers- Pelevin, Aleshkovski, etc.
Sometimes in aestetic mode Nabokov and Jodorowski.

 

[Nele]

but the axial 4700-50/63v low esr , really not easy to find , 

there's also a footprint for a radial version

 

[r2d2]

Thanks "Nele"
i have small space
an axial will be perfect
peace.

but the axial 4700-50/63v low esr , really not easy to find , 

there's also a footprint for a radial version

 

[Nele]

i have small space
an axial will be perfect

I think it should also be possible to use a radial cap and bend it flat againts the board, providing the leads are long enough, as is usually the case.

Adios,
Corneel

 

[Igor]

Depending on how much current you need, this cap can be 2200.....4700 uf, 40...63V.
This 3300x40V (just for example) can work here:
http://il.farnell.com/vishay-bc-components/2222-021-17332/capacitor-alum-elect-3300uf-40v/dp/1771936

Some other Farnell part Nr's:
http://il.farnell.com/jsp/search/browse.jsp?N=500004+1000224+5610494+5610534+5610580+5087827+5586161+5087885+5586183+5087944+5586197+5156380&Ns=PRICE_PLS_017_PRICE1|0&Ntk=gensearch_001&Ntt=capacitor&Ntx=mode+matchallpartial&locale=en_IL&appliedparametrics=true&getResults=true&originalQueryURL=/jsp/search/browse.jsp%3FN%3D500004%2B1000224%26Ntk%3Dgensearch_001%26Ntt%3Dcapacitor%26Ntx%3Dmode%2Bmatchallpartial%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Den_IL%26catalogId%3D%26prevNValues%3D500004%2B1000224

Don't go for Multicomp caps, use Vishay/Nichicon/IC/BC etc.

Yes, Uncle Fester is my favorite from this family....

 

[r2d2]

about C10-C12  - 01uf capacitor
it is poly-ester ?
or polypropylene , polystyrene
peace

 

[mrclunk]

Any old metallised polyester film is fine.
e.g Wima MKS2

 

[r2d2]

many thanks "mrclunk"
peace

ps
in the image uncle fester have "fan" with diy....

 

[r2d2]

with a 30VA toroidal main transformer
it's possible add some 5V or 2V led ?
(as "power on" status , switches on-off etc....)

or better a 50 VA?

and for protect old vintage "stuffs"
from electric overload and possible damages

may be a fuse (at v. out) a good protection for the vintages ?  :

peace