{"product_id":"helios-1r-stereo-type-69-mic-pre-eq","title":"Helios 1r Stereo Type 69 Mic Pre\/EQ","description":"\u003cp\u003e\u003cspan\u003eThe\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003eHelios 1r Stereo Type 69 Mic Pre\/Eq\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eis built in an aluminum case and has a glossy black front panel with white silk-screened labeling.\u003cspan\u003e  \u003c\/span\u003eThe unit is well constructed and neatly wired using all discrete components (no chips).\u003cspan\u003e  \u003c\/span\u003eIt runs on a 32-volt rail supplied from an internal OEM switching power supply.\u003cspan\u003e  \u003c\/span\u003eThe mic preamp uses a Sowter Type 8666X input transformer based on the highly desirable Lustraphone (Olympic Sound Studios) transformer model.\u003cspan\u003e  \u003c\/span\u003eInput impedance is 1,200 ohms.\u003cspan\u003e  \u003c\/span\u003eA separate switchable secondary winding provides for -20 dB of mic attenuation.\u003c\/span\u003e\u003c\/p\u003e\r\n\u003cp\u003e\u003cspan\u003eFront panel controls for each channel start on the left side with the mic\/line gain switching and a small output-level clip LED.\u003cspan\u003e  \u003c\/span\u003eA toggle switch selects between mic, -20dB mic attenuation and the 10k-ohm line input.\u003cspan\u003e  \u003c\/span\u003eA seven-position Elma rotary switch doubles as both line input and mic input gain control.\u003cspan\u003e  \u003c\/span\u003eThere are -5dB and 0dB line gain positions. \u003cspan\u003e \u003c\/span\u003eThe five mic gain positions start at 20 dB and go to 70 dB in 10dB steps.\u003cspan\u003e  \u003c\/span\u003eOther toggle switches include phase (polarity) flip, EQ cut, mic phantom powering on\/off and the ATT switch, where you can engage a small front panel trim pot for a small range of input level adjustment.\u003c\/span\u003e\u003c\/p\u003e\r\n\u003cp\u003e\u003cspan\u003eThe 3-band passive equalizer section uses a combination of RC and LC tone circuits, starting with an RC-based, 10kHz, 6dB-per-octave shelving filter with +\/- 10dB range.\u003cspan\u003e  \u003c\/span\u003eThe LC-based midrange equalizer has a surprising number of frequency choices on a single knob.\u003cspan\u003e  \u003c\/span\u003eThey are: 0.7, 1, 1.4, 2, 2.8, 3.5, 4.5, 6 and 16 kHz.\u003cspan\u003e  \u003c\/span\u003eThere is a Peak and Trough toggle switch.\u003cspan\u003e  \u003c\/span\u003e(Trough is Brit-speak for cut.) Up to 15 dB of boost\/cut is available on the unmarked +\/- control.\u003cspan\u003e  \u003c\/span\u003eThe starting Q for the midrange is a wide three octaves at 700 Hz; then, by 6 kHz, it narrows to two octaves.\u003cspan\u003e  \u003c\/span\u003eQ is proportionate: The more boost\/cut, the higher the Q.\u003c\/span\u003e\u003c\/p\u003e\r\n\u003cp\u003e\u003cspan\u003eThe LC-based bass section allows up to 15dB boost\/cut, and when the control is fully counterclockwise, the bass EQ section is switched out of the signal path.\u003cspan\u003e  \u003c\/span\u003eThis is good for keeping things ultra-clean.\u003cspan\u003e  \u003c\/span\u003eAnother rotary Elma switch selects 30, 80, 120, 240 and 400 Hz for the bass peaking section.\u003cspan\u003e  \u003c\/span\u003eThe same switch rotates to a 6dB-per-octave shelving filter mode that's fixed at 70 Hz with 3, 6, 9, 12 or 15 dB of roll-off.\u003cspan\u003e  \u003c\/span\u003eIf you like to boost bass and roll-off at the same time, then use the peaking section and select another 12dB-per-octave roll-off filter at 40 or 80 Hz.\u003c\/span\u003e\u003c\/p\u003e\r\n\u003cp\u003e\u003cspan\u003eThe output section is unbalanced and uses an emitter follower circuit and a Philips\/BEC electrolytic coupling capacitor, much like what's in the original Helios design.\u003cspan\u003e  \u003c\/span\u003eSwettenham found that the engineers at Olympic Studios preferred the sound of this circuit compared to the best output transformers.\u003c\/span\u003e\u003c\/p\u003e","brand":"Helios","offers":[{"title":"Default Title","offer_id":44449243693159,"sku":"796","price":0.0,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0658\/8848\/5479\/files\/helios_type_69_1r.jpg?v=1787088284","url":"https:\/\/vintageking.mom\/products\/helios-1r-stereo-type-69-mic-pre-eq","provider":"Vintage King","version":"1.0","type":"link"}