} Heritage Audio Herchild 660 Mono Tube Variable-Mu Compressor Limiter — Pro Audio Reserve
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Heritage Audio Herchild 660 Mono Tube Variable-Mu Compressor Limiter

$2,995.00
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Description


Heritage Audio Herchild 660 Mono Tube Compressor Demo

  Heritage Audio Herchild 660 mono tube variable-mu compressor

Fairchild 660 Sound at Half the Weight and Price

Less than 1,000 original Fairchild 660s were built. A functioning vintage unit commands $15,000–$25,000 and weighs over 30 pounds. The Herchild 660 delivers identical variable-mu behavior — 11 tubes, 5 transformers (AMI input, CineMag output), all-tube sidechain — at 16.23 lbs and a fraction of the cost. Built in Heritage Audio's factory in Spain using NOS 6BA6 variable-mu tubes and custom transformers spec'd to match the original.

Front-panel DC Threshold (original required internal screw adjustment) gives continuous control over ratio and knee from hard limiting to transparent compression. Sidechain filter with four selectable frequencies (50, 100, 200, 350 Hz) reduces low-frequency influence on gain reduction. Six attack/release time constants exactly duplicated from the original.

 Heritage Audio Herchild 660 program dependent soft knee compression

Program-Dependent Soft-Knee Variable-Mu Compression

Variable-mu tube gain reduction starts with a gentle ratio on small peaks and progressively increases to brick-wall limiting on loud transients. The compression curve responds to the music itself, not a fixed threshold — creating the buttery, natural dynamics that made the original a staple at Abbey Road (EMI owned multiple 660s used on Beatles vocals).

High-voltage operation ensures no audible thumps. Extremely low distortion and noise: THD <1% up to +18 dBu output, self noise <-82 dBu, SNR 120 dB. Input impedance 2 kΩ, output impedance 600 Ω, max output +30 dBu. Frequency response 40 Hz–15 kHz (±1 dB). Single XLR input/output.

 Heritage Audio Herchild 660 handwired Class A 3U Spain

Handwired Class A, Built to Outlast the Original

3U rackmount. Standard IEC AC power. Controls: AC/DC Threshold, Input Gain, Time Constant (6 settings), SC Filter (Off/50/100/200/350 Hz), Metering. Hand-assembled using same construction techniques as vintage British modules Heritage Audio is known for. Modern components eliminate the maintenance headaches of 1960s units.

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

  • Faithful Fairchild 660 recreation — 11 tubes, 5 transformers
  • NOS 6BA6 variable-mu tubes, AMI input transformer, CineMag output transformer
  • All-tube sidechain circuit for precise control
  • Program-dependent soft-knee compression (ratio increases with signal level)
  • Front-panel DC Threshold: continuous ratio/knee control (hard limit → transparent)
  • Sidechain filter: Off, 50, 100, 200, 350 Hz
  • Six attack/release time constants (exact original settings)
  • High-voltage operation eliminates audible thumps
  • Input impedance: 2 kΩ | Output impedance: 600 Ω
  • Max output: +30 dBu (clipping point)
  • Frequency response: 40 Hz–15 kHz (±1 dB)
  • SNR: 120 dB | Self noise: <-82 dBu | THD: <1% up to +18 dBu
  • 1 x XLR input, 1 x XLR output
  • 3U rackmount, 16.23 lbs
  • Handwired in Madrid, Spain

Heritage Audio Herchild 660 Specifications

Specification Details
Compressor Type Tube variable-mu compressor/limiter
Number of Channels 1 (mono)
Circuit Design Class A, handwired
Tubes 11 tubes (NOS 6BA6 variable-mu)
Transformers 5 transformers (AMI input, CineMag output)
Sidechain Circuit All-tube
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)
Input Impedance 2 kΩ
Output Impedance 600 Ω
Maximum Output Level +30 dBu (clipping point)
Controls AC/DC Threshold, Input Gain, Time Constant, SC Filter, Metering
Time Constants 6 attack/release settings (original Fairchild specs)
Sidechain Filter Frequencies Off, 50 Hz, 100 Hz, 200 Hz, 350 Hz
Analog Input 1 x XLR
Analog Output 1 x XLR
Rack Spaces 3U
Dimensions (W x H x D) 19" x 5.25" x 7.87"
Weight 16.23 lbs
Power Source Standard IEC AC cable
Manufactured Madrid, Spain

What's in the Box

Included Items
Heritage Audio Herchild 660 Mono Tube Compressor/Limiter
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 660 Mono Tube Compressor Demo

  Heritage Audio Herchild 660 mono tube variable-mu compressor

Fairchild 660 Sound at Half the Weight and Price

Less than 1,000 original Fairchild 660s were built. A functioning vintage unit commands $15,000–$25,000 and weighs over 30 pounds. The Herchild 660 delivers identical variable-mu behavior — 11 tubes, 5 transformers (AMI input, CineMag output), all-tube sidechain — at 16.23 lbs and a fraction of the cost. Built in Heritage Audio's factory in Spain using NOS 6BA6 variable-mu tubes and custom transformers spec'd to match the original.

Front-panel DC Threshold (original required internal screw adjustment) gives continuous control over ratio and knee from hard limiting to transparent compression. Sidechain filter with four selectable frequencies (50, 100, 200, 350 Hz) reduces low-frequency influence on gain reduction. Six attack/release time constants exactly duplicated from the original.

 Heritage Audio Herchild 660 program dependent soft knee compression

Program-Dependent Soft-Knee Variable-Mu Compression

Variable-mu tube gain reduction starts with a gentle ratio on small peaks and progressively increases to brick-wall limiting on loud transients. The compression curve responds to the music itself, not a fixed threshold — creating the buttery, natural dynamics that made the original a staple at Abbey Road (EMI owned multiple 660s used on Beatles vocals).

High-voltage operation ensures no audible thumps. Extremely low distortion and noise: THD <1% up to +18 dBu output, self noise <-82 dBu, SNR 120 dB. Input impedance 2 kΩ, output impedance 600 Ω, max output +30 dBu. Frequency response 40 Hz–15 kHz (±1 dB). Single XLR input/output.

 Heritage Audio Herchild 660 handwired Class A 3U Spain

Handwired Class A, Built to Outlast the Original

3U rackmount. Standard IEC AC power. Controls: AC/DC Threshold, Input Gain, Time Constant (6 settings), SC Filter (Off/50/100/200/350 Hz), Metering. Hand-assembled using same construction techniques as vintage British modules Heritage Audio is known for. Modern components eliminate the maintenance headaches of 1960s units.

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

  • Faithful Fairchild 660 recreation — 11 tubes, 5 transformers
  • NOS 6BA6 variable-mu tubes, AMI input transformer, CineMag output transformer
  • All-tube sidechain circuit for precise control
  • Program-dependent soft-knee compression (ratio increases with signal level)
  • Front-panel DC Threshold: continuous ratio/knee control (hard limit → transparent)
  • Sidechain filter: Off, 50, 100, 200, 350 Hz
  • Six attack/release time constants (exact original settings)
  • High-voltage operation eliminates audible thumps
  • Input impedance: 2 kΩ | Output impedance: 600 Ω
  • Max output: +30 dBu (clipping point)
  • Frequency response: 40 Hz–15 kHz (±1 dB)
  • SNR: 120 dB | Self noise: <-82 dBu | THD: <1% up to +18 dBu
  • 1 x XLR input, 1 x XLR output
  • 3U rackmount, 16.23 lbs
  • Handwired in Madrid, Spain

Heritage Audio Herchild 660 Specifications

Specification Details
Compressor Type Tube variable-mu compressor/limiter
Number of Channels 1 (mono)
Circuit Design Class A, handwired
Tubes 11 tubes (NOS 6BA6 variable-mu)
Transformers 5 transformers (AMI input, CineMag output)
Sidechain Circuit All-tube
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)
Input Impedance 2 kΩ
Output Impedance 600 Ω
Maximum Output Level +30 dBu (clipping point)
Controls AC/DC Threshold, Input Gain, Time Constant, SC Filter, Metering
Time Constants 6 attack/release settings (original Fairchild specs)
Sidechain Filter Frequencies Off, 50 Hz, 100 Hz, 200 Hz, 350 Hz
Analog Input 1 x XLR
Analog Output 1 x XLR
Rack Spaces 3U
Dimensions (W x H x D) 19" x 5.25" x 7.87"
Weight 16.23 lbs
Power Source Standard IEC AC cable
Manufactured Madrid, Spain

What's in the Box

Included Items
Heritage Audio Herchild 660 Mono Tube Compressor/Limiter
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