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Old 27th November 2007, 05:50 AM   #1
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Default ASR Basis Phono Preamp

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,
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Old 27th November 2007, 06:16 AM   #2
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Scan the relevant page and mail it to me. I will translate it for you.

Greetings Till
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Old 27th November 2007, 07:27 AM   #3
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The ASR units seem easy to clone. Care to take some pictures of the insides?
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Old 27th November 2007, 08:17 AM   #4
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Default Re: ASR Basis Phono Preamp

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?
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Old 27th November 2007, 08:36 AM   #5
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Default Re: ASR Basis Phono Preamp

Hi Haenisch,

Can you give me your email address to send the attachment?

My email address is gaomi2001@hotmail.com

Sunny
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Old 27th November 2007, 10:57 AM   #6
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Default Re: Re: ASR Basis Phono Preamp

Quote:
Originally posted by Sunsun22
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 don't doubt it's real. If you take some pics the rest of us can try to clone
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Old 27th November 2007, 11:25 AM   #7
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The older Schaefer&Rumpf phono-pre models have PMI SSM2019/2142 opamps
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Old 27th November 2007, 12:58 PM   #8
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Default Re: ASR Basis Phono Preamp

Please find the full picture of the phono amp
Attached Images
File Type: jpg asr1.jpg (92.0 KB, 692 views)
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Old 27th November 2007, 01:00 PM   #9
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Default Close up of ASR Basis

Close up of the transistors and dip switches. I am expecting the one on the right is dip1 that takes care of impedance while the other is dip2 takes care of gain and capacitance.
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File Type: jpg asr2.jpg (70.9 KB, 611 views)
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Old 27th November 2007, 04:01 PM   #10
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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
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