Art DjPreII Phono Preamp , some question about it

thinker10 · 16th October 2007, 09:44 PM

Hi,

How can it work either from 7 to 12V DC or 9 to 12V AC ?

The wall wart they supply is 9V AC and 1000mA

Why AC ?

Maximum input level is 40mVrms @ 1kHz

Maximum gain is 45db @ 1kHz

Maximum Output level is +6dBu (1.4Vrms)

They don't mention input sensitivity.

I assume the nominal level is -10dBu or less since the max output is only +6dBu.

I don't have schematic yet , I hope they say yes.

Thank You

oddetc · 20th October 2007, 04:26 AM

please let me know I just got one of those as well.

Gordy · 21st October 2007, 07:34 PM

I do not know the circuit so I will take a guess...

If the first component on the circuit board is a diode then it will flow DC or rectify the AC. If so the next component is likely to be an electrolytic capacitor and then some form of voltage regulator with a minimum input requirement of 7 Volts.

Still guessing... if it requires about 7 Volts then the regulator is likely to be something like a 7805 which has an output voltage of 5 Volts and requires an input of at least 7 Volts.

If the circuit runs from a single 5 Volt supply then it will need to be offset / biased around half of that Voltage (i.e. 2.5 Volts DC) to give equal positive and negative swings. If it is operating on an offset of 2.5 Volts DC it will need a capacitor at the input and the output to block the flow of the DC Voltage, allowing only the required alternating voltage signal to enter and leave the circuit.

Just a guess.

Sherman · 21st October 2007, 09:07 PM

I'm with Gordy. I think they have a diode inside, filtering and a voltage regulator to give the final DC voltage required by the circuit.

Bottom line though is that it is an extremely good phono pre for the price. Adjustable gain, adjustable input capacitance and good sound. I use one with a passive pre to control a variety of amps and output level is definitely sufficient.

thinker10 · 23rd October 2007, 01:01 AM

But with very high output MM cart like a Shure M44-7 it overload madly even at the lowest -10dB setting.

The overload is only 40mv @ 1kHz

Thanks

16th October 2007, 09:44 PM	#1
thinker10 diyAudio Member Join Date: Nov 2003 Location: Canada	Art DjPreII Phono Preamp , some question about it Hi, How can it work either from 7 to 12V DC or 9 to 12V AC ? The wall wart they supply is 9V AC and 1000mA Why AC ? Maximum input level is 40mVrms @ 1kHz Maximum gain is 45db @ 1kHz Maximum Output level is +6dBu (1.4Vrms) They don't mention input sensitivity. I assume the nominal level is -10dBu or less since the max output is only +6dBu. I don't have schematic yet , I hope they say yes. Thank You

21st October 2007, 09:07 PM	#4
Sherman diyAudio Member Join Date: Feb 2004 Location: Chicago area	I'm with Gordy. I think they have a diode inside, filtering and a voltage regulator to give the final DC voltage required by the circuit. Bottom line though is that it is an extremely good phono pre for the price. Adjustable gain, adjustable input capacitance and good sound. I use one with a passive pre to control a variety of amps and output level is definitely sufficient. __________________ --Sherman

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
new phono stage or old preamp with phono?	flohmann	Analog Line Level	2	2nd October 2008 09:51 PM
Question about phono preamp schematic	jn2630	Tubes / Valves	11	3rd January 2008 01:36 AM
Electret mic preamp - will phono preamp work?	darthmullet	Analogue Source	6	12th October 2007 07:32 AM
QUESTION ABOUT Rin IN ¨EL CHEAPO¨ PHONO PREAMP	federico moreno	Analogue Source	8	3rd March 2006 05:30 PM
Phono preamp question	ionutg	Analogue Source	6	22nd February 2005 08:28 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

20th October 2007, 04:26 AM	#2
oddetc diyAudio Member Join Date: Oct 2007	please let me know I just got one of those as well.

21st October 2007, 07:34 PM	#3
Gordy diyAudio Member Join Date: Nov 2006	I do not know the circuit so I will take a guess... If the first component on the circuit board is a diode then it will flow DC or rectify the AC. If so the next component is likely to be an electrolytic capacitor and then some form of voltage regulator with a minimum input requirement of 7 Volts. Still guessing... if it requires about 7 Volts then the regulator is likely to be something like a 7805 which has an output voltage of 5 Volts and requires an input of at least 7 Volts. If the circuit runs from a single 5 Volt supply then it will need to be offset / biased around half of that Voltage (i.e. 2.5 Volts DC) to give equal positive and negative swings. If it is operating on an offset of 2.5 Volts DC it will need a capacitor at the input and the output to block the flow of the DC Voltage, allowing only the required alternating voltage signal to enter and leave the circuit. Just a guess.

23rd October 2007, 01:01 AM	#5
thinker10 diyAudio Member Join Date: Nov 2003 Location: Canada	But with very high output MM cart like a Shure M44-7 it overload madly even at the lowest -10dB setting. The overload is only 40mv @ 1kHz Thanks

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)