urgent help needed - Stanton 310B PHONO AMP

[happylad]

Hi everyone , I have just got one of these broadcast phono amp's and need some solid advice . Although it has a handbook with it , Im finding it a bit hard to understand ,there are two set's of trimmmers on the front that are adjusted by a small screw driver .According to the hand book some sort of meter is needed to set the HF response and gain adjustment . I have twiddled with these whilst feeding it a signal from my moving magnet cartridge , I have fed the stanton into my quad 34 pre amp on the Aux but it is very loud ( can only use the first 3 settings on the volume control ! ) If anyone can point me in the right direction with some idiot proof steps or if anyone knows of someone in the Herts. area of the uk who can help I would be very grateful . Cheers

[abril]

Sophisticated bit of kit you have there

Would start off by setting both adj level trimmers at min (should be 36db gain),you'll easily be able to hear the diff between min and max (got earplugs )

Have you got access to a tape deck and test record?

[happylad]

Hi Abril , thanks for the response much appreciated , I have a couple of test records ( shure and hi fi news) and a mini disc recorder and cassette recorder . What type of meter should I use to test the db and on what setting ?

[abril]

Set the level roughly first (the end stop of the level trimmers should do that)

PS
Never seen one before,but I see the manual is in the library.

[happylad]

Hi again , unfortunately the trimmers have no stop end , they just twist round and round . I have a multi meter , in the handbook it says you can set the db with a voltmeter but does not elaborate

[abril]

According to the internal pic I have found they look like multiturns.

http://www.flickr.com/photos/robtweston/2725907256/

[happylad]

So how do I test ?

[abril]

Connect your cassette deck to the tape connectors making sure the channels are correctly connected.

Put the deck into record/pause.

Play a constant tone of some sort (both channels)from the test record (as long a track as possible).

Set the record level control of the cassette deck so that the meter shows about 0db with the tone playing.

Now twiddle the adj level controls of the Stanton - you should see the meter reading of the cassette deck vary.

[happylad]

thats a good idea ! does it have to be cassete or will a mini disc do ? thanks for that tip ! lets hope this is the start of getting this working !

[abril]

Whichever has the best resolution on the metering (no experience of minidisc).

Even better if you have metering like this

[Chris Angel]

I would appreciate it if you would share your experiences setting up and using the 310B. I just purchased a NOS unit my self and other than the manual there is precious little information available on this preamp. I am looking forward to the arrival from California of this really interesting preamp. I was really intrigued by these statements from the instruction manual:

"All IC devices are socket mounted and are easily accessible. All electronic components except the power transformer are commonly available values and types for ease in servicing."

Looks very versatile and solid especially for MM carts. I do not see any resistive loading options though at 36-66db gain it appears to be capable of handling most MC carts. I have read about someone rigging a 50K ohm stepped (variable) pot and of another person in another forum who ---

"removed the power transformer from the unit and mounted it remotely. It dropped the hum level. I added some more capacitance to the power supply and the bass solidified. I re-flowed some solder connections that looked bad. I upgraded some of the caps in the audio circuit."

The schematic is readily available and it looks like Stanton even designed this preamp to be upgradeable. I am sure others know of cap swaps based on the schematic. These plus balanced / unbalanced output, RIAA & NAB bode very well for an interesting, quality unit with some easy potential upgrades.

I am a bit confused on the NAB / RIAA front. I don't see an RIAA setting; only NAB & flat. Is the default RIAA when neither NAB or Flat is selected? It almost must be the case but confirmation would be helpful as the manual does not indicate how the RIAA setting is accessed.

The flat setting will be very useful for me in cases where the NAB setting is not suitable for some of my older 78's or when I want to use digital (computer based) RIAA or 78rpm EQ settings. I will post any additional information I find on the Stanton 310B.

[happylad]

Hi Chris , regarding the NAB /Flat setting , it's a push button affair with just the two settings ( think I read somewhere NAB = riaa , it sounds ok anyway . I would imagine this phono pre amp would be very easy to upgrade , the whole housing is easy to remove leaving a exposed pcb easily accessible on both side's , it looks very well made to my untrained eye .In the handbook is a list of all component place's and value's.

By the way Abril thats a fantastic tape deck you have there ! . . . . . I want one !

[Chris Angel]

Yes happylad you are correct. My confusion arose because I had recently become familiar with the history of the RIAA phonograph curve. At one time both a NAB eq curve and the RIAA curve existed separately though there was only a difference of 2db or 3db in the roll off at one of the specified frequency points. The NAB curve really caught on at the tail end of the 78 era.
Long before Stanton produced the 310B the NAB and the RIAA were on the same page regarding phono EQ / compression and the RIAA curve was adopted.

The NAB produced test records designed to enable checking the phono chain from turntable to either the tape out of the preamplifier or the phono stage output depending on system configuration.

After reading the 310B manual and the following description of testing it is clear this unit was designed from the standpoint of a using a NAB record to test RIAA conformance and to enable as much adjustment and correction as possible. A NAB test record is so essential to the highest functioning of the 310B that it is labelled NAB and not RIAA, though this also may have been customary in professional audio.

I've found a number of sites that explain what the RIAA curve is and how important it is, but no instructions on checking it. However, I can tell you how to check it.
You will need a NAB disc and a decibel meter. The NAB Test Record NAB-1 is a vinyl record with a series of frequency tones on it from 30cps to 15,000cps. Put the NAB disc on your turntable and connect the decibel meter to your "Tape Output" on your preamp, if it has one. If there's no "Tape Output" the second choice is the "Main Output" with all tone controls "OFF". If you're using a separate phono preamp, then connect to it's output.

Use the 1,000cps tone on the disc for your "reference". Whatever dB reading this tone gives you, this will be your zero or reference tone. All other readings will be considered above or below this mark and labelled plus or minus by so many dB. A perfect system will give the same dB level reading at all the test frequencies. However, in this real world, you will be doing good to have the frequencies stay within plus or minus 2 dB in many cases. If you go outside of the plus/minus 2dB then I recommend trying to correct it. If you're within the 2dB you can try to get it better and see what happens.

Please keep in mind that you are testing the actual functional response of the cartridge, cables, RIAA compensation loop, and preamp. All of these items can be "working properly" and still not give a flat response due to the capacitance and resistance of the cartridge loading. That is why it's so important to check the RIAA playback response with an actual Test Record. The manufacturer of the preamp or cartridge may publish the specs on it's RIAA playback response as being plus or minus 0.00001 dB, and it may in fact meet those specs. But this is the capability of the preamp to play the exact RIAA reverse response curve to the curve on your records. You will never get the NAB Disc to play back that flat. So, for other perfectionists like me, don't drive yourself crazy trying to get the NAB disc to play back flatter than is reasonably possible.

It seems these NAB test records have not been produced in eons but I found the following comments regarding setup using the NAB record and "The Ultimate Analog Test Record".

I use the Ultimate Analog test record.
When I bought my Lathe from Al we ran through the calibration together using a NAB disc.
When I got my lathe home I ran through the calibration on my own using the Ultimate Analog disc. The final values on the amp rack were exactly the same after the subsequent calibration as they were when I brought it home.
Obviously the two discs are not identical. But, they seem to be very close. Otherwise I think I would have derived very different settings after calibrating with the Ultimate Analog.

To summarize a NAB test record or the equivalent Ultimate Audio are an essential component to unlocking the very considerable capabilities of the Stanton 310B.

[mmarston]

Hi again , unfortunately the trimmers have no stop end , they just twist round and round . I have a multi meter , in the handbook it says you can set the db with a voltmeter but does not elaborate

Those are probably 10 turn pots. You may be able to hear or feel a slight click when you get to each end but the shaft will continue turning. A bit cumbersome but they make precise adjustment easy once you get close.

Best,
Mike