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Old 9th April 2015, 01:07 AM   #1
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Default Budget MM/MC phono board from E/Bay

Has anyone tried this board out?
http://www.audiowind.com/pdf/A-310.pdf
It is available from E/Bay at US$13-00 with free shipping!!.
Can't expect much for the money but it has a pare of OPA2134PA opp amps which have a good reputation for fairly good sound.
What I like about the design is that you can set the input resistance and capacitance through a 2 DIP switches. Plus working of of DC you can use batteries to power it for the quieties operation.

Chhers
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Old 9th April 2015, 01:57 AM   #2
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Have a look at: http://www.lencoheaven.net/forum/ind...?topic=18231.0
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Old 9th April 2015, 11:17 PM   #3
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It looks to be an exact copy of The Beavis HiFi Kitchen Sink Phono Preamplifier:

http://www.beavishifi.com/articles/p...tic-rev0-9.png

The only differences I can see is that the output capacitor has changed from 5.1uF to 4.7uF, and the volume pot is left out.
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Old 9th April 2015, 11:24 PM   #4
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The equalization is in the feedback loop... That's not the best way to do it.
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Old 10th April 2015, 09:27 PM   #5
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It has ideal loadings for old Shure pick ups. How weird. Carbon film resistors will slightly raise hiss levels. Douglas Self suggests trying a 2 uS passive filter after all active designs. If you change the output resistor to 200 R and have 10 nF from the node with 4.7 uF NP to ground it might polish the way is sounds. If you stay with 47 R use 47 nF, on second thoughts that is fine. The small advantage is that 10 nF NPO is easy to get and cheap. 1206 SMD is a good bet, easy to solder. The op amp seems OK. You might risk raising the gain for low output MC, it should be OK. The 220R could be shunted with 100R as a guess for that. The 50 dB seems ideal for the Denon DL110. They are better than people know if the gain is right. I have heard one of the world most expensive turntables threw a Clear Audio stage which is a little bit like this. It sounded great. 30 dB would suit Shure M44-7. You need 40 dB for others. Try shunting the 2K2 with 1 K as a guess. Usually gain that is a bit high sounds good. Even at high gain the hiss should be like a good FM tuner on a broadcast or Revox Tape recorder with mics.
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Old 10th April 2015, 09:39 PM   #6
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Note: OPA2134 is a dual opamp, and this circuit uses only one - but at this price I suspect it is fake.

For a few bucks more you can build your own VSPS with genuine parts and have a much better phono stage, IMO.

All those dip switches might be handy if you are using the phono stage with all sorts of different TTs and carts, but otherwise they are completely unnecessary (again, IMO).

RJM Audio - Printed Circuit Boards
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Old 10th April 2015, 10:17 PM   #7
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I would fit a DIL holder. Try MC33078, NE5532 and perhaps OPA2604. The latter is a hunch, it might like the circuit more than the others. Even try TL072 for fun.

Get the gain you need then short the switches with wire links. This means you can revert if tuning in a new cartridge. You can shunt using a resistor to the upper switch node. That kills two birds with one stone.

Pick up loading is one of the most frusraiting questions. With modern pick ups and good op amps it is less important. Often loading is helping the preamp more than doing the magic people will claim. As hinted the Shures like less loading sometimes( > 68 K ) . Most MC's are happy at 47 K , the same MC could sound fine into 22 R. My Lyra does.

The thing that really matters is gain. 3 dB can move things from good to excellent. The reasons are complex. The MC 33078 likes high gain and sings when it does. I measured a couple in series at gain 1000 ( 10000 @ 20 Hz ) and did not get much distortion. If someone says 0.1 THD is high I suspect 10 % THD on vinyl can happen and will be as intended. Some disco stuff was cut with the old London curve to get extra bass on the record. No doubt 30 Hz 10 % THD is normal for that.
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Old 10th April 2015, 10:32 PM   #8
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BTW. A friend did a very nice loading mod. That is to have a RCA next to the RCA for the input. That offers loading without compromise. The loading in a RCA plug. Rean/Neutrik RCA's are good value. If you fit a 5 pin DIN that could be your gain adjuster ( 2K2 on PCB, no switch, then shunt ) . Use 4 of the 5 pins. You might say DIL socket no way for the op amp. In truth the op amp will be the big difference. To unsolder a 8 PIN DIL is not too bad when certain. Brake the plastic and pull out a socket one at a time. If you have no desoldering tool heat and blow hard. Often it works.
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Old 23rd November 2016, 09:36 AM   #9
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Default Stop Gap Phono Amp - But not to Shabby

Hi, Picked up on this tread because I need a Stop Gap board while my Dino was away getting upgraded. Need something that could adequately drive my Goldring Eroica H cartridge.
We I was very surprised & please about it's sound quality, easily better than say a 651 plus I could load cartridge correctly
Saw the comments about changing the chip & wondered if one of this would be suitable For HDAM Full Discrete Single Op Amp Module Board Replace AD797 OPA627 NE5534 | eBay

Cheers
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Old 24th November 2016, 07:34 AM   #10
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You can also build CNC Phonostage Another Super High End Phono Stage! No expense spared... | Audiokarma Home Audio Stereo Discussion Forums much, better.
I have PCbs.

Regards
Sachin
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