During a recent trip to Europe, I bought from a second hand audio shop an ASR Basis Phono Preamp with separate power supply. It is a non-battery version and I believe it was built in 1989 because I saw a label inside the power supply unit with 1989 on it. There are 6 RCA sockets and I think I already get the output pair but what are the other 2 paris for?
I plugged my turntable to one pair of input and there is output but the gain is not enough to drive nomrally although the sound is normal without distortion. I plugged the turntable to another input pair but all I got was hum. I have a manuel but it is in German that I don't know how to deal with the 4 dip switches inside the unit.
Does anyone has an English manuel?
Thanks regards,
I plugged my turntable to one pair of input and there is output but the gain is not enough to drive nomrally although the sound is normal without distortion. I plugged the turntable to another input pair but all I got was hum. I have a manuel but it is in German that I don't know how to deal with the 4 dip switches inside the unit.
Does anyone has an English manuel?
Thanks regards,
I believe this is a real ASR because of the workmanship and the raw materials being used. If I am going to clone, I'll clone a Basis Exclusive rather than an old Basis without battery supply.
I ran through the German manual and I "think" the two pair of inputs are for MM and MC separately. The MC channel will go through an extra gain stage while the MM will go straight to the second stage.
The MM channel should be the one that I tried with low output level because I am using a moving iron cartridge with 47K and approximately 1.2 mV output. I use the word approximately because it is a Grado Statement with original 47K and 0.75mV but retipped by Van Den Hul. After retip, I have to lower the gain of my existing phono amp (DACT) because of excessive output. Yet, this 1.2mV would not be sufficient to drive an ordinary MM phono pre resulting a low output level as described above. This is only my thoughts.
There is gain control on the MC section but the highest impedance is only 1K therefore will not match the 47K of Grado Statement. Can I change the matching resistor in the MC section to fit the Grado?
I ran through the German manual and I "think" the two pair of inputs are for MM and MC separately. The MC channel will go through an extra gain stage while the MM will go straight to the second stage.
The MM channel should be the one that I tried with low output level because I am using a moving iron cartridge with 47K and approximately 1.2 mV output. I use the word approximately because it is a Grado Statement with original 47K and 0.75mV but retipped by Van Den Hul. After retip, I have to lower the gain of my existing phono amp (DACT) because of excessive output. Yet, this 1.2mV would not be sufficient to drive an ordinary MM phono pre resulting a low output level as described above. This is only my thoughts.
There is gain control on the MC section but the highest impedance is only 1K therefore will not match the 47K of Grado Statement. Can I change the matching resistor in the MC section to fit the Grado?
Hi Haenisch,
Can you give me your email address to send the attachment?
My email address is gaomi2001@hotmail.com
Sunny
Can you give me your email address to send the attachment?
My email address is gaomi2001@hotmail.com
Sunny
Thanks Sunsun22
So, this one is all discrete. Probably paralleled symmetrical diff front end, emitter followers into a passive riaa and a simple output stage. Higher res will be essential for cloning but the design philosophy is quite interesting: not a sign of regulation, no servo. One would think these guys are allergic to ICs
So, this one is all discrete. Probably paralleled symmetrical diff front end, emitter followers into a passive riaa and a simple output stage. Higher res will be essential for cloning but the design philosophy is quite interesting: not a sign of regulation, no servo. One would think these guys are allergic to ICs
I wrote an email to ASR and received immediate and informative reply. My guess is right - the outermost RCA socket is for MM input, the middle RCA socket is for MC input and the innermost RCA socket is for output. I can also guess from the German manuel on the gain stage and input impedance of the MC stage but something strange happened.
As mentioned, I am using a 47K with approx 1.2mV output cartridge which is not having enough output to drive the MM section. I only get hum when using the MC input before because I need to switch a dip switch to on position to swap between MC and MM input. When I choose a lower impedance when using the MC section, I get higher out put from the phono amp but mind bearing that my cartridge is 47K!
Can anyone give me a clue?
Oh I forgot to mention about the sound quality. I just switched the ASR on last night at 22:30 that I cannot really give it a "normal" try. The sound quality is not as detail and punchy as the DACT but of course, it was just switched on and the impedance is not correct. Yet, I doubted if I can get a normal output when changing one of the resistor to 47K too?
Any comment?
As mentioned, I am using a 47K with approx 1.2mV output cartridge which is not having enough output to drive the MM section. I only get hum when using the MC input before because I need to switch a dip switch to on position to swap between MC and MM input. When I choose a lower impedance when using the MC section, I get higher out put from the phono amp but mind bearing that my cartridge is 47K!
Can anyone give me a clue?
Oh I forgot to mention about the sound quality. I just switched the ASR on last night at 22:30 that I cannot really give it a "normal" try. The sound quality is not as detail and punchy as the DACT but of course, it was just switched on and the impedance is not correct. Yet, I doubted if I can get a normal output when changing one of the resistor to 47K too?
Any comment?
If the MC section is an add-on in front of the MM, chances are there is no 47k resistor included as a load option. Unless you want to do some soldering you are probably stuck with using the MM input. What is your cart? Low output MM? Lower gain seems a better compromise than incorrect loading.
Yes, the MC section is in front of the MM with no 47K. I wish to solder a 47K in the impedance section but my question is --
I experience some strange things that the 47K cartridge is not having distortion when plugged into a 10 ohmes MC section. The higher I put on the impedance, the lower is the gain. What's the reason?
My cartridge is a Grado Statement but retipped by Van Den Hul. The original output was 47K and 0.75mV but after retip, I need to lower the gain of my existing phono amp and I believe the output is now 1.2mV.
I experience some strange things that the 47K cartridge is not having distortion when plugged into a 10 ohmes MC section. The higher I put on the impedance, the lower is the gain. What's the reason?
My cartridge is a Grado Statement but retipped by Van Den Hul. The original output was 47K and 0.75mV but after retip, I need to lower the gain of my existing phono amp and I believe the output is now 1.2mV.
The reason it doesn't sound really bad in a lower load is probably the very low inductance for a MM cart - 2mH.
The gain/impedance dependancy is not so clear without a circuit.
If the input section is an inverting discrete opamp amp the input resitor will at the same time set the gain which will be inversely proportional to the resistance.
The gain/impedance dependancy is not so clear without a circuit.
If the input section is an inverting discrete opamp amp the input resitor will at the same time set the gain which will be inversely proportional to the resistance.
There are only resistors in the impedance section. I bought this vintage ASR because this is opamp free. I don't like IC too much.
There is a separate power unit with regulators but a very simple one. I'm going to replace it with a much better power supply when able to get this running with my Grado in good setting. Furthermore, since the unit is running on + - 6V, I can easily use 2 x 6V batteries to give it another test.
There is a separate power unit with regulators but a very simple one. I'm going to replace it with a much better power supply when able to get this running with my Grado in good setting. Furthermore, since the unit is running on + - 6V, I can easily use 2 x 6V batteries to give it another test.
You misunderstood me. It is quite clear from your pics there are no opamps. You only need 3 discrete transistors and a few resistors to put an opamp equivalent together. If you then use it in inverting configuration you will get the reverse dependency between input resistance and gain you observe.
If you'd like to have this settled once and for all take a couple of high-res pics, email them to me and i'll only be pleased to draw a circuit.
If you'd like to have this settled once and for all take a couple of high-res pics, email them to me and i'll only be pleased to draw a circuit.
ASR replied that the circuit does ot resemble what ASR is doing today therefore disallow me in putting it in this forum or distributing to others. I need to honor because this is their rights.
Anyway, after warming up, it sounds smoother and more natural than my DACT phono preamp. The DACT has more attack and bass but when compared to this vintage ASR, DACT sounds a bit flavored. Matter of personal taste.
My next step is to change the PSU to a low impedance and quieter design.
Thanks everyone.
Anyway, after warming up, it sounds smoother and more natural than my DACT phono preamp. The DACT has more attack and bass but when compared to this vintage ASR, DACT sounds a bit flavored. Matter of personal taste.
My next step is to change the PSU to a low impedance and quieter design.
Thanks everyone.
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