Telefunken V376 - adding phantom power & more... ?

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Anonym

Well-known member
Joined
Jul 1, 2005
Messages
46
Hi,
I'd like to add phantom power to my Telefunken V376. Searching on the web I found the following circuit by Jensen-transformers:

Standard Microphone Preamp Input Circuitry

Is there any reason not to use this one ?

Concerning the resitors: is a 1/4W the minimum, or the exact required type ?

I'd like to use my mixer's power supply for starters, at least for the phantom power. If I want to make use of a voltage divider also to get the 24V required by the preamp, what value should the resitors have ?


best regards,
anonym
 
Is there any reason not to use this one ?

No.

Concerning the resitors: is a 1/4W the minimum, or the exact required type ?

Always minimum.

I'd like to use my mixer's power supply for starters, at least for the phantom power. If I want to make use of a voltage divider also to get the 24V required by the preamp, what value should the resitors have ?

You can't use divider for supply voltages - they're wastefull and completely dependent on load current. Use a regulator (that will accept that high an input voltage and dissipate the needed power) or build a powersupply.

Building a powersupply is easier than building that pre frontend.

Jakob E.
 
Thanks for your fast answer.

For now I will continue using my wallwart as a power supply. Or do you think building a power supply would be kind of a good exercise before doing the frontend ?

Is there a certain powersupply you would specially recommend me to build ?
 
Use a linear power supply instead of your wallart (switching power suplly) all audio aplications will benefit from a linear PSU.

Synthi.
 
[quote author="Anonym"]Thanks for your fast answer.

For now I will continue using my wallwart as a power supply. Or do you think building a power supply would be kind of a good exercise before doing the frontend ?

Is there a certain powersupply you would specially recommend me to build ?[/quote]
Power supplies are really easy to build... (they were my first build about 9 months ago)
If you are after a 24v and 48v supply.. have a go at this..
http://www.vintagedesign.halmstad.net/diy/psu.pdf
This will also give you a supply for a 6v relay if you want one
 
Thanks for your answers.

I hope this question's not too stupid, but I can't see where the 220V are put on any powersupply I found on the web...

I've looked at JLM's page and found the DI and the Go Between Kit which seem interesting, too. As I'm not really into diy yet, kits might be a good start for me. Any objections, anyone ?

Are there any websites or books you'd recommend me for getting the basics of audio electronics ?

[quote author="CJ"]Get a wallwart from wallmart and listen to "Hello Wall" thru your new 376. :razz:[/quote]

Sorry, I don't understand this one :oops:
 
Um....

You prob. would not want to put 220V AC on any power supply you saw. ... unless you want smoke and bad smells :green:

You will need some kind of transformer to step down (set up) the voltage from 220V AC to a lesser value, depending on the value you need on the PSU.

I think in your case if you were using a JLM PSU you would need 24Vac, this you get by uses a transformer that goes from 220Vac to 24Vac, this in turn is connected to the PSU and comes out regulated DC on the other end.

JLM's design is great because it is variable. By using trim pots you can adjust the Vdc to be what ever you need it to be, from 2V - 37Vdc, in your case you prob need 24Vdc to power the unit (I might be wrong, I just know alot of the old German stuff ran on 24V)

It would also give you a 48V rail for Phantom on top of the bipolar, which from the sounds of it is what you need.

Joe's kits are great, I have not built one myself, but have one in a rack I got from a friend,a nd many others here swear by them, just do a search.

The other thing to consider is the go between kits, esp. for Phantom, as it has been posted before Joe was able to mod the kit for user to slow ramp the phantom, which is what you want on the older German pres that were not designed to take phantom straight on.

If you are new to DIY I strongly recommend you look at Joe's kits :thumb:

I hope that helps.

Cheers

Matt
 
[quote author="matta"]You prob. would not want to put 220V AC on any power supply you saw. ... unless you want smoke and bad smells :green:[/quote]

well, no, thanks... :wink:

You will need some kind of transformer to step down (set up) the voltage from 220V AC to a lesser value, depending on the value you need on the PSU.

I think in your case if you were using a JLM PSU you would need 24Vac, this you get by uses a transformer that goes from 220Vac to 24Vac, this in turn is connected to the PSU and comes out regulated DC on the other end.

JLM's design is great because it is variable. By using trim pots you can adjust the Vdc to be what ever you need it to be, from 2V - 37Vdc, in your case you prob need 24Vdc to power the unit (I might be wrong, I just know alot of the old German stuff ran on 24V)

It would also give you a 48V rail for Phantom on top of the bipolar, which from the sounds of it is what you need.

What kind of transformer will I need; do you have any links or words I can search for ?

What does the PSU do if it it gets 24V and gives 24V out ?
 
Transformers gives you a workable and non-dangerous 24V AC. PSU electronics converts this AC into stable DC.

Btw: why are you anonym? It's always nicest to know who people are..?
 
The 24V in is AC current, but your PRE needs DC, so the PSU rectifies and regulates the AC into DC.

RE the transformer torridal's are quiter your standard CT styled transformer, but more expensive, but the best for audio use.

Your best bet is to decide what PSU you want to build and then that will dictate what trano and Vac is needed.

Cheers

Matt
 
Well, I chose "anonym" as my nick because I found it fun to sign with it...

Thanks again for your explanations. I'll probably go for the JML Audio kits. Doing my own PCBs as a first step seems a little too much for me.


Cheers,
Pascal
 
I finally ordered, got and built my JLM Audio kits. Though having bombarded Joe with questions, I still managed to have it go up in smoke... :eek:(
at least one condenser blew up, and there are three that look weird now.

I will try to understand why myself, but I would still like your help so I can start repairing it as soon as possible without destroing it again...

when it blew up, I had it connected this way:

1,2 - Mic in
3 - Mic earth

19,20 - Out
21 - Out earth

23&23 - bridged

29, 31 - 24V


When I used it with my wallwart, pins 3 and 4 were bridged. As i could not find why that was i did not do it this time, i suppose that's the error and that's the first thing i will look into.

Thanks
Pascal
 
i realized that the schematic and pinout i had was the one for the v376a... should have looked at it before, it is quite obvious it is not the same circuit - even for me who understands nearly nothing of it... :oops:

i think i will just change the obviously damaged caps and try if it works...

if anyone is interested in the schematics for the v376a i can mail them
 
i have sent it to kubi.

there are two elcaps blown. One is 500µF / 3V, one 1000µF / 15V.

i assume the voltage is just the maximum voltage, so i can take 16V ones as replacement, right?

As i do not find 500µF caps i suppose the best way to go is buying a couple of 470µF ones and take the one next to 500µF ?

is there something else i should look for? there are other thing labelled on the caps, i suppose the "VALVO" is the company, and the 12000 and 12009 are their serials or something. they are also labelled 36P and 27P...

anything stupid so far?

-----------------------

i just tested the caps as well as possible, my multimeter does not support capacitance, and my new one has not arrived yet. the caps that look like shit do not seem totally blown, the 1000µF one even seems to work according to the testing method in my mm's manual. as there are no values for the 500µF one in it and the charging time is very close, i think that one is not ok...

i think i will wait for my new multimeter before doing something

still answers to the above would interest me
 
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