QUAD 22 and Ortofon SPU - advice needed

[OldRecordLover]

I've inherited a QUAD 22/II setup and want to use mono Ortofon SPUs with it - here are their specifications -

Mono CG 25 Di MkII (microgroove)
Output voltage at 1000 Hz, 5cm/sec. - 1.5 mV
Frequency response - 20-15.000 Hz + 3/- 1 dB
Tracking ability at 315Hz at recommended tracking force *) 60 µm
Compliance, dynamic, lateral - 7 µm/mN
Internal impedance, DC resistance - 6 ohm
Recommended load impedance > 100 ohm


Mono CG 65 Di MkII (78s)
Output voltage at 1000 Hz, 5cm/sec. - 1.5 mV
Frequency response - 20-15.000 Hz + 3/- 1 dB
Tracking ability at 315Hz at recommended tracking force *) 60 µm
Compliance, dynamic, lateral - 7 µm/mN
Internal impedance, DC resistance - 6 ohm
Recommended load impedance > 100 ohm

1. I understand that I'll need a step-up transformer - can anyone suggest a suitable one for less than £500 or so? (I've already had one recommendation for an Audio-Technica AT630.)

2. I have two pickup adapters for the QUAD 22 (both new, from eBay) - pne marked 22/47k and the other 22/A . Are either of these suitable or should I get something else - and if so, what type?

I'd be very grateful for any advice - my audio knowledge is very limited, so the simpler the better...

[Barry]

With an output voltage of 1.5mV, it would appear that your Ortofon cartridges have a built in transformer, and whilst the voltage is a little on the low side the output ought not need further boosting. Thus either of the Quad adaptors should be suitable.

What arm are you using, and do the Ortofon cartridges come with a headshell with the bayonet fixing? If so how many contact 'pips' are there at the bayonet: 2 or 4? (Your 'avatar' suggest the arm is an SME 3009, and the cartridges are complete with the Ortofon 'whale''shaped headshell.)

[OldRecordLover]

Thank you, Barry. My arm is an SME3009 (photos in my AOS album) and the SPU has 4 pins.

I'm currently using a Benz Micro Glider SH (output 2.6mV) and need to have the QUAD volume control quite high, so I just assumed that a cartridge with an lower output of 1.5mV would need quite a lot more boosting. I've just noticed this on the Ortofon website -


This cartridge features a 1.5mV output, which makes it suitable for use with a variety of medium-gain moving coil transformers. Ortofon ST-M25 moving coil transformer is designed exclusively for the SPU Mono CG 25 Di MkII and SPU Mono CG 65 Di MkII.

Maybe the ST-M25 would work well with the QUAD?

[Barry]

I have just had a look at the instruction book for the Quad 22 Control Unit (and Quad 11 Power Amplifier). Using the Quad A plug in unit gives the preamp a pick-up sensitivity of 4mV, with an input impedance of 68k (and, presumably, an input impedance of 47k with "22/47k" unit).

I'm surprised you need to have the volume control set quite high when using your Benz Glider with its 2.6mV output, since the 4mV quoted sensitivity is for a full output of 15W from the Quad II power amps. If this is the case then the 1.5mV output from the Ortofon cartridges will be insufficient.

The recommended ST-M25 transformer has a voltage step up factor of 12dB (i.e. a voltage increase of 4x): https://www.ortofon.com/media/148288/st-m25-userguide.pdf , which will boost the output of the cartridge to 6mV. This should be more than sufficient for you to use the volume control at a lower setting.

[OldRecordLover]

Thanks again, Barry - I appreciate your help. I don't understand the technical/electrical side of things but will show it to a relative who does. I will check out the Ortofon mono SUT.