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Heritage Audio Herchild 670 Ardent Edition Stereo Tube Variable-Mu Compressor

$10,999.00
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Description

Heritage Audio Herchild 670 Ardent Edition Stereo Tube Variable-Mu Compressor

Heritage Audio Herchild 670 Ardent Edition Overview

  Heritage Audio Herchild 670 Ardent Edition stereo tube compressor

The Ardent Modifications That Shaped Led Zeppelin III

In the early 1970s, the engineers at Memphis' Ardent Studios quietly modified their Fairchild 670 units with faster attack and release time constants — tuned to better serve the demands of modern tracking at the time. These changes were first put to work on Jimmy Page's acoustic guitar performances for Led Zeppelin III, and remained one of the studio's best-kept secrets for over four decades. Heritage Audio worked directly from the original handwritten modification notes, spending months with the Ardent team to nail every time constant to specification. The result impressed Ardent's engineers so thoroughly that they retired all four of their original Fairchild units and replaced them with Herchild models.

Produced only on request and in strictly limited quantities, the Herchild 670 Ardent Edition is handmade in Heritage Audio's factory in Madrid, Spain. Ownership means joining a list of artists and engineers who have recorded at Ardent — Led Zeppelin, ZZ Top, Stevie Ray Vaughan, Isaac Hayes, R.E.M., The White Stripes, Bob Dylan, and dozens more — all connected by the same modified Fairchild sound now available in reliable, serviceable hardware.

Heritage Audio Herchild 670 Ardent 22 tubes 9 transformers variable-mu

22 Tubes, 9 Transformers, and Program-Dependent Compression

Like the standard Herchild 670, the Ardent Edition is built around 22 NOS military-grade 6BA6 variable-mu tubes and nine custom transformers running at high voltage. This depth of analog hardware ensures the program-dependent soft-knee behavior that defines the Fairchild — compression that starts gently on small peaks and builds progressively toward brick-wall limiting on loud transients, responding to the music rather than a fixed ratio.

Direct front-panel access to the DC Threshold gives you continuous control over the ratio and knee from hard limiting to transparent compression, a feature the original required an internal screw to access. The all-tube sidechain circuit includes a high-pass filter with four selectable frequencies (50, 100, 200, and 350 Hz) to control low-frequency influence on gain reduction — an essential tool for modern mixing and mastering that the original never offered.

Heritage Audio Herchild 670 Ardent Edition LAT VERT mid-side four modes

Four Operating Modes Including Full LAT/VERT Mid-Side Processing

The Herchild 670 Ardent Edition operates in four distinct modes. IND runs each channel independently for dual-mono use. LINK connects both channels with compression driven by the channel with the highest control voltage, giving you true stereo compression. LAT/VERT provides full mid-side processing, compressing lateral and vertical elements of a stereo signal separately for increased mix width, depth, and focus. LAT/VERT LINK does the same using the average control voltage of both channels.

These modes make the Ardent Edition equally powerful as a tracking compressor, a stereo bus processor, or a precision mastering tool. Extremely low distortion and self noise below -82 dBu mean it can sit permanently in the most critical signal chains. As an authorized dealer, Pro Audio Reserve ensures you receive a genuine Heritage Audio product backed by full manufacturer warranty and long-term support.

Highlights

  • Ultra-limited stereo Fairchild 670 recreation with Ardent Studios modifications
  • Attack and release times precisely matched to Ardent's modified vintage units
  • Originally used on Jimmy Page's acoustic guitar tracks for Led Zeppelin III
  • 22 NOS military-grade 6BA6 variable-mu tubes and 9 custom transformers
  • Class A, fully tube-based variable-mu compression
  • Program-dependent soft-knee compression with progressive ratio
  • Front-panel DC Threshold for continuously variable ratio/knee control
  • All-tube sidechain circuit
  • Sidechain filter: Off, 50 Hz, 100 Hz, 200 Hz, 350 Hz
  • Four operating modes: IND, LINK, LAT/VERT (mid-side), LAT/VERT LINK
  • Frequency response: 40 Hz – 15 kHz (±1 dB)
  • Signal-to-noise ratio: 120 dB
  • Self noise: less than -82 dBu
  • THD: less than 1% at any level up to +18 dBu (no limiting)
  • Maximum output: +30 dBu (clipping point)
  • Input impedance: 2 kΩ | Output impedance: 600 Ω
  • 6U rackmount, handmade in Madrid, Spain on request only

Heritage Audio Herchild 670 Ardent Edition Specifications

Specification Details
Compressor Type Tube variable-mu compressor/limiter
Number of Channels 2 (stereo)
Circuit Design Class A, fully tube-based, handwired
Tubes 22 NOS military-grade 6BA6 variable-mu tubes
Transformers 9 custom transformers
Frequency Response 40 Hz – 15 kHz (±1 dB)
Signal-to-Noise Ratio 120 dB
Self Noise Less than -82 dBu
Harmonic Distortion Less than 1% at any level up to +18 dBu output (no limiting)
Maximum Output Level +30 dBu (clipping point)
Input Impedance 2 kΩ
Output Impedance 600 Ω
Time Constants 6 Ardent-specific attack/release settings (faster than standard 670)
Sidechain Filter Frequencies Off, 50 Hz, 100 Hz, 200 Hz, 350 Hz
Operating Modes IND, LINK (stereo), LAT/VERT (mid-side), LAT/VERT LINK
Analog Inputs 2 x XLR
Analog Outputs 2 x XLR
Rack Spaces 6U
Dimensions (W x H x D) 19" x 10" x 8" (482 mm x 265 mm x 200 mm)
Weight 29.3 lbs (13.3 kg)
Power Source Standard IEC AC cable (>200W)
Manufactured Madrid, Spain (ultra-limited, produced on request only)

What's in the Box

Included Items
Heritage Audio Herchild 670 Ardent Edition Stereo Tube Compressor
Power Cable
User Manual
Shipping

Shipping & Returns

  • We deliver all US orders in 3–5 business days
  • Free cancellations
  • Returns accepted within 30 days (unused items)

Order Confirmation

Once your order is placed, you will receive an order confirmation email. This confirms that we have received your order and have pre-authorized your credit card for the purchase. After confirming availability with our suppliers, we will proceed accordingly:

  • If your item is available and ready to ship within 1–2 business days, we will process the charge and arrange for shipment.

  • If your item is on backorder or unavailable, the pre-authorization will be voided and you will be notified by email.

  • Please note: While most items ship out within 1–2 business days, total delivery time is typically 3–5 business days, depending on your location and carrier handling.

Order Shipment

If your item is in stock and your payment has been processed, your order will typically ship within 1–2 business days. Total delivery time is approximately 3–5 business days from the date of order. Once shipped, you will receive tracking information at the email address provided during checkout within 24 hours of dispatch.

If you have not received tracking information within 3–5 business days of placing your order, please contact us at support@proaudioreserve.com.

The Distributor-Direct Advantage

To ensure you receive the most recent hardware revisions and 100% factory-sealed units, Pro Audio Reserve utilizes a Distributor-Direct fulfillment model. Unlike big-box retailers that may ship "floor models" or gear that has been sitting in general-purpose warehouses, your equipment is pulled directly from the primary manufacturer hub, serialized, and dispatched. This process ensures the highest level of quality control for professional-grade recording equipment.

Shipping Policy

We currently offer free shipping within the United States only. If the checkout process on our website allows you to enter a shipping address and complete your order, your location is eligible to receive delivery.

Changing Shipping Address

If you need to change your shipping address after your order has been processed or shipped, we will do our best to accommodate the request. Please note that address changes may result in delivery delays. Any additional costs incurred due to address changes, including carrier fees or rerouting charges will be the responsibility of the customer. No exceptions.

Shipping Times

All shipping times provided are estimates and should not be considered guarantees. Most orders ship out within 1–2 business days from the time payment is processed. However, total delivery time is typically 3–5 business days, depending on your location, carrier performance, and supplier fulfillment timelines.

We work closely with our vendors to ensure timely deliveries, but please note that supply chain disruptions, high-demand periods, or weather events may occasionally cause delays beyond our control.

  • To avoid misunderstandings: The “shipping time” refers to the total time from order placement to final delivery, not just when the item leaves the warehouse.

  • Cancellations: If you choose to cancel your order because it has not arrived within the estimated delivery window, you may be responsible for applicable shipping charges, restocking fees, warehouse handling costs, and other related fees.

  • Chargebacks: Customers who initiate chargebacks due to shipping delays without contacting us first may be held legally responsible for losses. We strongly encourage open communication so we can resolve any delivery concerns directly and efficiently via our Atlanta-based support team.

Delivery Options

  • Threshold Shipping: Your item will be delivered to your front door, porch, garage, or a covered entryway.

 

Why Buy From Us

We get it. You've got a lot of choice when it comes to online retailers.
Here's why we think you should shop with us at ProAudioReserve.

  • Free Shipping USA wide. 
  • 30 Day Easy Returns. Not happy with your product, we'll take it back noquestions asked.
  • Great Service. We pride ourselves on the best service, anywhere.

Reviews
Description

Heritage Audio Herchild 670 Ardent Edition Stereo Tube Variable-Mu Compressor

Heritage Audio Herchild 670 Ardent Edition Overview

  Heritage Audio Herchild 670 Ardent Edition stereo tube compressor

The Ardent Modifications That Shaped Led Zeppelin III

In the early 1970s, the engineers at Memphis' Ardent Studios quietly modified their Fairchild 670 units with faster attack and release time constants — tuned to better serve the demands of modern tracking at the time. These changes were first put to work on Jimmy Page's acoustic guitar performances for Led Zeppelin III, and remained one of the studio's best-kept secrets for over four decades. Heritage Audio worked directly from the original handwritten modification notes, spending months with the Ardent team to nail every time constant to specification. The result impressed Ardent's engineers so thoroughly that they retired all four of their original Fairchild units and replaced them with Herchild models.

Produced only on request and in strictly limited quantities, the Herchild 670 Ardent Edition is handmade in Heritage Audio's factory in Madrid, Spain. Ownership means joining a list of artists and engineers who have recorded at Ardent — Led Zeppelin, ZZ Top, Stevie Ray Vaughan, Isaac Hayes, R.E.M., The White Stripes, Bob Dylan, and dozens more — all connected by the same modified Fairchild sound now available in reliable, serviceable hardware.

Heritage Audio Herchild 670 Ardent 22 tubes 9 transformers variable-mu

22 Tubes, 9 Transformers, and Program-Dependent Compression

Like the standard Herchild 670, the Ardent Edition is built around 22 NOS military-grade 6BA6 variable-mu tubes and nine custom transformers running at high voltage. This depth of analog hardware ensures the program-dependent soft-knee behavior that defines the Fairchild — compression that starts gently on small peaks and builds progressively toward brick-wall limiting on loud transients, responding to the music rather than a fixed ratio.

Direct front-panel access to the DC Threshold gives you continuous control over the ratio and knee from hard limiting to transparent compression, a feature the original required an internal screw to access. The all-tube sidechain circuit includes a high-pass filter with four selectable frequencies (50, 100, 200, and 350 Hz) to control low-frequency influence on gain reduction — an essential tool for modern mixing and mastering that the original never offered.

Heritage Audio Herchild 670 Ardent Edition LAT VERT mid-side four modes

Four Operating Modes Including Full LAT/VERT Mid-Side Processing

The Herchild 670 Ardent Edition operates in four distinct modes. IND runs each channel independently for dual-mono use. LINK connects both channels with compression driven by the channel with the highest control voltage, giving you true stereo compression. LAT/VERT provides full mid-side processing, compressing lateral and vertical elements of a stereo signal separately for increased mix width, depth, and focus. LAT/VERT LINK does the same using the average control voltage of both channels.

These modes make the Ardent Edition equally powerful as a tracking compressor, a stereo bus processor, or a precision mastering tool. Extremely low distortion and self noise below -82 dBu mean it can sit permanently in the most critical signal chains. As an authorized dealer, Pro Audio Reserve ensures you receive a genuine Heritage Audio product backed by full manufacturer warranty and long-term support.

Highlights

  • Ultra-limited stereo Fairchild 670 recreation with Ardent Studios modifications
  • Attack and release times precisely matched to Ardent's modified vintage units
  • Originally used on Jimmy Page's acoustic guitar tracks for Led Zeppelin III
  • 22 NOS military-grade 6BA6 variable-mu tubes and 9 custom transformers
  • Class A, fully tube-based variable-mu compression
  • Program-dependent soft-knee compression with progressive ratio
  • Front-panel DC Threshold for continuously variable ratio/knee control
  • All-tube sidechain circuit
  • Sidechain filter: Off, 50 Hz, 100 Hz, 200 Hz, 350 Hz
  • Four operating modes: IND, LINK, LAT/VERT (mid-side), LAT/VERT LINK
  • Frequency response: 40 Hz – 15 kHz (±1 dB)
  • Signal-to-noise ratio: 120 dB
  • Self noise: less than -82 dBu
  • THD: less than 1% at any level up to +18 dBu (no limiting)
  • Maximum output: +30 dBu (clipping point)
  • Input impedance: 2 kΩ | Output impedance: 600 Ω
  • 6U rackmount, handmade in Madrid, Spain on request only

Heritage Audio Herchild 670 Ardent Edition Specifications

Specification Details
Compressor Type Tube variable-mu compressor/limiter
Number of Channels 2 (stereo)
Circuit Design Class A, fully tube-based, handwired
Tubes 22 NOS military-grade 6BA6 variable-mu tubes
Transformers 9 custom transformers
Frequency Response 40 Hz – 15 kHz (±1 dB)
Signal-to-Noise Ratio 120 dB
Self Noise Less than -82 dBu
Harmonic Distortion Less than 1% at any level up to +18 dBu output (no limiting)
Maximum Output Level +30 dBu (clipping point)
Input Impedance 2 kΩ
Output Impedance 600 Ω
Time Constants 6 Ardent-specific attack/release settings (faster than standard 670)
Sidechain Filter Frequencies Off, 50 Hz, 100 Hz, 200 Hz, 350 Hz
Operating Modes IND, LINK (stereo), LAT/VERT (mid-side), LAT/VERT LINK
Analog Inputs 2 x XLR
Analog Outputs 2 x XLR
Rack Spaces 6U
Dimensions (W x H x D) 19" x 10" x 8" (482 mm x 265 mm x 200 mm)
Weight 29.3 lbs (13.3 kg)
Power Source Standard IEC AC cable (>200W)
Manufactured Madrid, Spain (ultra-limited, produced on request only)

What's in the Box

Included Items
Heritage Audio Herchild 670 Ardent Edition Stereo Tube Compressor
Power Cable
User Manual
Shipping

Shipping & Returns

  • We deliver all US orders in 3–5 business days
  • Free cancellations
  • Returns accepted within 30 days (unused items)

Order Confirmation

Once your order is placed, you will receive an order confirmation email. This confirms that we have received your order and have pre-authorized your credit card for the purchase. After confirming availability with our suppliers, we will proceed accordingly:

  • If your item is available and ready to ship within 1–2 business days, we will process the charge and arrange for shipment.

  • If your item is on backorder or unavailable, the pre-authorization will be voided and you will be notified by email.

  • Please note: While most items ship out within 1–2 business days, total delivery time is typically 3–5 business days, depending on your location and carrier handling.

Order Shipment

If your item is in stock and your payment has been processed, your order will typically ship within 1–2 business days. Total delivery time is approximately 3–5 business days from the date of order. Once shipped, you will receive tracking information at the email address provided during checkout within 24 hours of dispatch.

If you have not received tracking information within 3–5 business days of placing your order, please contact us at support@proaudioreserve.com.

The Distributor-Direct Advantage

To ensure you receive the most recent hardware revisions and 100% factory-sealed units, Pro Audio Reserve utilizes a Distributor-Direct fulfillment model. Unlike big-box retailers that may ship "floor models" or gear that has been sitting in general-purpose warehouses, your equipment is pulled directly from the primary manufacturer hub, serialized, and dispatched. This process ensures the highest level of quality control for professional-grade recording equipment.

Shipping Policy

We currently offer free shipping within the United States only. If the checkout process on our website allows you to enter a shipping address and complete your order, your location is eligible to receive delivery.

Changing Shipping Address

If you need to change your shipping address after your order has been processed or shipped, we will do our best to accommodate the request. Please note that address changes may result in delivery delays. Any additional costs incurred due to address changes, including carrier fees or rerouting charges will be the responsibility of the customer. No exceptions.

Shipping Times

All shipping times provided are estimates and should not be considered guarantees. Most orders ship out within 1–2 business days from the time payment is processed. However, total delivery time is typically 3–5 business days, depending on your location, carrier performance, and supplier fulfillment timelines.

We work closely with our vendors to ensure timely deliveries, but please note that supply chain disruptions, high-demand periods, or weather events may occasionally cause delays beyond our control.

  • To avoid misunderstandings: The “shipping time” refers to the total time from order placement to final delivery, not just when the item leaves the warehouse.

  • Cancellations: If you choose to cancel your order because it has not arrived within the estimated delivery window, you may be responsible for applicable shipping charges, restocking fees, warehouse handling costs, and other related fees.

  • Chargebacks: Customers who initiate chargebacks due to shipping delays without contacting us first may be held legally responsible for losses. We strongly encourage open communication so we can resolve any delivery concerns directly and efficiently via our Atlanta-based support team.

Delivery Options

  • Threshold Shipping: Your item will be delivered to your front door, porch, garage, or a covered entryway.

 

Why Buy From Us

We get it. You've got a lot of choice when it comes to online retailers.
Here's why we think you should shop with us at ProAudioReserve.

  • Free Shipping USA wide. 
  • 30 Day Easy Returns. Not happy with your product, we'll take it back noquestions asked.
  • Great Service. We pride ourselves on the best service, anywhere.

Reviews