APP Studio Ing's products - APP992 - APP14GE Germanium DOA and other kits

[ppa]

Hi Pier,
some questions about your APP PSU - (maybe it should be posted elsewhere?)

I´m learning by doing, so sorry for newbie questions.
Is a 30VA 2x18V enough for powering 4x312-style pres running at 16V, in addition to 48V?
I don´t understand how the PSU makes +48V from this toroid- but I can see that theres no input for a +48V secondary.
LM317 is only specced to about +37V. Will it be able to handle +48V?
I also want to pretrim the trimmers so I´m not that far off when powering up, but I cant seem to calculate the right values - since LM317 needs more than 10K to make 48V when R6 is 332ohm according to schematic.

Thanks
Rune

Hi Rune,

a 30VA 18Vx2 transformers is a good for 4x312 style preamp.

Regarding the +48V , PSU2 , as many PSU for mic preamp, has an internal voltage multiplier section to generate this voltage from a much lower AC voltage from the trasformer.

Regarding the LM317, that voltage value of 37V is relative to the difference of the V input and the V out at the relative input and out pin of the LM317.
I have designed the PSU2 to have this difference always under 30V (also in the OFF-ON transition).
 

 

[ppa]

II also want to pretrim the trimmers so I´m not that far off when powering up, but I cant seem to calculate the right values - since LM317 needs more than 10K to make 48V when R6 is 332ohm according to schematic.

Thanks
Rune

using R6= 12.5 kohm you have +48.6V , but the advantage of the trimmer is to get the exact value of +48V. The matter is that without trimmer the +48V out is subjected to the 5% of tollerance of the LM317's reference voltage and , moreover at the 1% of tollerance of the resistors.
However, these tollerance are limit values, so, in the real case, probably you will get a value very near to +48.6V. At this point I council you to test the PSU2 phanthom voltage out with no trimmer and using the 12.5 k resistor. If this value is good you can leave the PSU as it is. 

Please, consider that output phanthom gives power to expensive microphones too, for this reason I have put a trimmer inside the circuit to set the exact value of +48V, just to be clear.

 

 

[Rellister]

Hi Pier,

thanks for a good explanation

 

[Dr Gris]

Hi Pier,

the APP992's you sent me are amazing. Makes my new eq' s sound very refined with beautiful transient preservation.
Boosting the highs are so smooth silky.

Kind regards
Magnus

 

[dingo]

hello!Pierpaolo

here some picture with your preamp. MA1
sharing api lunchbox 6B with other preamp.
this MA1 sounds wery good 
on vocals,guitars ,overheads drum,bass, etc. etc.
very nice sounding  preamp and a good alternative to api style preamp!!!

thanks!!
Dingo.

 

[Rellister]

Pier,

please check your gmail.

 

[KrIVIUM2323]

Hello PPA,

you've got a pm. 

Best regards.

 

[kante1603]

Pm sent for APP992 order.

Best regards,

Udo

 

[SubhumanRecords]

I would love 1 kit please...

 

[ppa]

I would love 1 kit please...

PM sent

 

[dubwarrior]

IO board 

--> boards available



This high performances board can be used for many circuits to give them a balanced input and output (with makeup stage) when it is needed.

The IO Board is an input-output card, so it has an input section to unbalance signals from gears and a make-up stage to balance  signals from unbalance sources. Moreover, the IO board has an high impendance FET buffer to interface the make-up stage to very high impedance sources if required.

These very high performances input and out stage are both based on solid state technology and they can run with DOA's and/or IC opamps, so the customer can use many DOA's and IC opamps in the market.
Moreover, the out section has a zone for an output trasfomer to place easily it in 1U rack chassis, just using two screws. Can be used several trasformers (cinemag, jensen, classicapi) on it.

IO board can use all APP DOA's and many other DOA's as 2520, JE990 , JLM99....etc....
so you can choise the sound look basing on the DOA's (or IC opamps).

Just to note that it is also possible use the buffer plus the make-up stage as very high performance instrument amplifier with trasformerless or trasformer coupled out.
By the way it is possible use this board as line amplifier too, or both instrument and line amp.

IO board has a new design for the input stage that does not use any electrolytic cap but only small 1uF polyester caps and a servo DC stage.
Moreover, a servo DC is present in the make-up stage too, to avoid any capacitor on input-output and in the nfb net.

This board was sold in a recent group buy with success so I would like to re-propose it to the market for who want a modern in-out interface.  I have launched a support thread for the IO board  here http://www.groupdiy.com/index.php?topic=46320.0

How much gain those you IO boards have?

regards

rico

 

[ppa]

How much gain those you IO boards have?

regards

rico

46 dB max.

Pier Paolo

 

[dubwarrior]

Thanks

Thats alot, even enough for a Phono preamp with a passive RIAA filter..

regards

rico

 

[ppa]

Thanks

Thats alot, even enough for a Phono preamp with a passive RIAA filter..

regards

rico

I am just designing a phono preamp using two APP992's.

Pier Paolo

 

[dubwarrior]

Thanks

Thats alot, even enough for a Phono preamp with a passive RIAA filter..

regards

rico

I am just designing a phono preamp using two APP992's.

Pier Paolo

That sounds great 

Any Idea when its available?

So i canbuild a preamp for my home HiFi system, with 1 IO Board for CD-Player and with the new(or with the IO and RIAA Filters) phono pre, and a switch..
Then some transformers in the output, a dream come true

;D ;D

Regards

Rico

 

[ppa]

Yes, with two io boards is possible to make a complete hifi line preamp with balanced or unbalanced inputs and outputs.
Regarding the phono preamp I think that for this weekend I should having designed  it,
The phono preamp uses two servos to avoid caps in the signal path, so there are no caps from input to out. My APP992 (and APP2055) has a very low noise and it suitable for MC phono preamps.

Pier Paolo
 

 

[dubwarrior]

This sound great.

exactly what im looking for to build the phone/line pre-amp.

let me know when some pcbs are available, do you sell them here?

Regards

Rico

 

[dubwarrior]

Hy Paolo

Any news abut your phono pre?  ;D

Do you have any recommendations for transformars for the IO Board?


cheers

Rico

 

[ppa]

Hy Paolo

Any news abut your phono pre?  ;D

Do you have any recommendations for transformars for the IO Board?


cheers

Rico

I have just designed the schematic and I going to design the PCB.
After I will have done to design this PCB I will order some PCB for prototyping , at this point, if this phono preamp runs fine, I could give you two of these ones. 

kind regads
Pier Paolo

 

[dubwarrior]

Hy Paolo

Any news abut your phono pre?  ;D

Do you have any recommendations for transformars for the IO Board?


cheers

Rico

I have just designed the schematic and I going to design the PCB.
After I will have done to design this PCB I will order some PCB for prototyping , at this point, if this phono preamp runs fine, I could give you two of these ones. 

kind regads
Pier Paolo

that would be really generous 

About the Line IO boards
Do you have any transformer recommendations?

regards

Rico