caruso preamp pcb boards for sale..

[Serif]

For what it's worth, Ortofon also wants you not to use the 75 microseconds (2120 cps) pre-emphasis during set-up, so, when "Test" is illuminated, that part of the RIAA curve is "turned off." (This is true for pre- and de- emphasis in the GO741, so that test records can be cut and checked that are flat from 1k on up.)

The reason seems primarily to be that one can inadvertently be signaling with positive feedback. If the part of the RIAA pre-emphasis at 75 microseconds is not eliminated, there can be a danger to the drive coils if everything else is not as expected in the setup. Multiple instances of precaution are indicated where humans are involved. (:

In the interest of precaution, with the Ortofon amps and head, one starts the feedback setup with a 1 kHz sine wave at only 100 mV. With the "Test" (no 75 us) and "Power Limit" buttons engaged, one slowly raises the "cutter damping" (i.e., feedback) amount, while watching the monitor meter. If the output starts to rise with more damping, one immediately turns back down the damping and reviews the interconnections.

Only once the feedback polarity is determined to be negatively summing with the program (as intended) does one then switch to the 5 kHz test tone, and this is down at only 10 mV.

The manual explains, "...due to the complex phase relationship the level will start to go up about 1 dB at 5kHz as the damping control is turned up the first few degrees. [However,] Further rotation will result in continued reduction in output."

The stability reserve is the amount of dB above the ideal feedback setting before oscillation of the cutter head results. The red and blue 700 series Ortofon heads typically use about 12 dB feedback, with a 6 dB stability reserve. (This means we take -20 dBu, turn up the feedback until it drops to -32 dBu, and then restore gain at input until we see -20 dBu, again.)


- Stylus Wigglesworth

[Nickou]

So , I had the time this week end to work a bit more on this ( very interesting )project ...
It works ! and it seems it sounds good !!!!

Next week , I ll plug it inside the sal rack to have a better idea , but I won t be surprised if it sounds as good as the neumann ...
Flo , how do I plug the output of your preamp to the sal ?
I plug the output on + and the ground on the - ?
or do I have to balance the ouput before ¿?

more advise with the sal ?

many thanks !

[flozki]

cool.
ha! it will sound definitely better than the SAL thats for sure!

but the main SAL problem are the power amps... distributed on so many
cards so many contacts....

so better get some good amps.hehe
i think in combination with good amps and the rc network you get great sound.

i never thought about replacing any sal cards... so have to check the schematics. i guess its a little bit more complicate because of dc offset for the protection cards. also whole feedback phantom power is missing. etc etc.
i let you know after reviewing schematics.

[JuanPabloCuervo]

for the ones who have the boards already.

i put together a site, blog for the amp.

but in short :

changes and part values for preampboard v10

C403,R401 not necessary.
bridge under the riaa-switch pin
add an output resistor (47-100) between output of opamp and 6.3mm jack socket.

opamps.
i tested with lowcost tl072.opa2134 is great. ne5532 should work perfect and sounds great for its price.

-r309,c316 is the input low pass. set that betwenn 22kHz (hobby) and 50 kHz for professional use.

-C400,402 can be somewhere between 10uF and 47uF to be tested
-R606 head specific (gain for fb-preamp)
-R405,C403 head specific (PI amount) 26 for neumann and sc99. if you are not sure or use a non feedback type.bridge r405 , leave out c403
-C405,R407 is the D-amount. if you are not sure or use a non feedback type.bridge r407 , leave out c405


happy bricolage....

the boards can be modified for Half Speed "0.5x" & "0.75x" Speeds ?

[andybee]

yes you can! (I think so)
You have to double the RIAA condensors, and a switch or relais can
switch it on or off.
I use a modified EQ Curve for Half Speed Cutting...
Good luck!

[Nickou]

Flo ,

Did you had free time to work on the caruso head ?

I have some money back to buy one !!!!


all the best
>Yann

[JuanPabloCuervo]

hello my contribution for a summer holiday project....

i have first batch caruso preamp boards ready for sale.
additionally you need a good and nice +/- 15V powersupply.

Hi,
is caruso here?

can you make an API 500 rack/series compatible pcb boards?
with laser cut acrylic front plate ".cdr file" or optional steel box/face plate?

for:
Chameleon Audio CPS-501
A-Designs 500HR
Empirical Labs EL500
Revolver
API 6b lunch box
API 500Vpr
Purple Audio Sweet Ten
Radial Eng.
etc...

2. do you know power consumption? mA

Thanks.

[andybee]

http://vinylike.de/index.php/caruso/

[djlithium]

When can we expect to see the head available with the electronics and possibly an overhead carriage (thinking full set up for SL1200MKII use type thing) if ever?

[lucien]

Hi,
I've read in the schematics v1.23 PDF file on Vinylike that a new version of the preamp board is scheduled.
Do you know when it will be available?
Thanks.