Quad C Core Output Transformer

Value Line Output Transformers (last update 1/1/2016)

Preface

We are lucky to secure a batch of limited quantity vintage British made C cores (silicon steel, amorphous steel and amorphous nickel-steel alloy C cores). Some of them are NOS and some of them are pulls. It might look a bit worn or rusty due to age but it still functions perfectly. We have taken this into consideration of the price (cheaper) as compared to a full price (especially amorphous) C core that is sky high in price in the market. Please do not order the amorphous C core transformer if you cannot tolerate this. 

Amorphous cores are meant for medium to high frequency use. Amorphous cores (worse if is or added nickel) are easily saturated and therefore the low frequency response will not be as great as the Z11 or Z6 cores. Due to such magnetic properties, designing such audio transformers requires extreme care, and larger cores are required to achieve good low frequency response.

In order to overcome this limitation, the best way is to increase the core size, and therefore dual C core and quad C core are called for in TRUE high fidelity design that excels both in extended refined high frequencies, dense and warm mids and deep impactful bass. 

Why do we need a quad core one might ask? It increases the core volume by 400% (4 cores!) to give more headroom. With the 4 cores covering N-S-E-W of the bobbin, it is actually fully utilizing instead of wasting the flux produced by the coil for increased efficiency and better sound! Imagine retrieving back of the original signal/energy lost back to your system. 

In addition, we prefer the vintage British made C core too, like many of the excellently made British HIFI gears. Nowadays such high quality C cores are hard to find and expensive to source. We will not dig further into the advantages of amorphous core. You can read more of them in the internet.

I’m keeping a few pairs for myself for various circuits before it runs out, are you? 

Lead time is around 2~4 weeks. Customization services for different applications, circuit topology, air-gap, configuration or different tubes are available.

Quad Core

QCAMOPT-L01---(3.5K OPT for 300B)                    - $449/matched pair

QCFEIP-S01-------(1:5.8 input/pre-out)                  - $329/matched pair

QCAMOPT-M01---(2.5K/5K OPT for 2A3/45)           - $209/matched pair (no longer have stock, email to check for availability)

(limited standard units left, cannot offer customization for QCAMOPT-M01 size, 2.5K/5K OPT can still be done using the QCAMOPT-L01 cores)

Double Core

DCAMOPT-X01---(8K/16K OPT for 211/845)           - $659/matched pair
DCAMOPT-L01---(3.5K OPT for 300B)                      - $329/matched pair

DCAMIT-L01------(1:2.25 interstage for 211/845)     - $329/matched pair

DCAMC-M01------(8H/300mA choke)                        - $129/piece

Single Core
SCAMOPT-M01--- 3.5K: 8 Ohm - $269/matched pair
SCAMOPT-M02--- 6.6K: 8 Ohm - $269/matched pair

QC – quad core, DC – dual core, AM – amorphous, FE - ferrous

NOTE: please email us if you need other specifications.

Looking for transformer casing -> Matching Transformer Cases

Transformer Details

Amorphous Quad C Core Output Transformers (nickel-steel alloy) – QCAMOPT-L01

This is made using 8 pieces of C-core per transformer, having 16 pieces altogether for a pair of high end amorphous quad C core nickel steel alloy output transformer for tube amplifier. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: single ended and push pull
• Primary impedance: 3.5K (standard), other impedances per request.
• Primary inductance: 35H @ 100Hz,
• Primary current: 150mA maximum
• Primary DCR: 98 Ohm, Secondary DCR: 0.45 Ohm (@ 8 Ohm tap)
• Leakage inductance: 6mH, leakage capacitance: 14nF
• Frequency response: 30Hz – 30kHz
• Weight: 2.5KG per piece
• Size: 95mm x 80mm x 105mm
• 3.5K / 4-8-16 Ohm

Amorphous Quad C Core Output Transformers (nickel steel alloy) – QCAMOPT-M01

This is made using 8 pieces of C-core per transformer, having 16 pieces altogether for a pair of high end amorphous quad C core nickel steel alloy output transformer for tube amplifier. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

(limited standard units left, cannot offer customization for QCAMOPT-M01 size, 2.5K/5K OPT can still be done using the QCAMOPT-L01 cores)

• Available types: single ended and push pull
• Primary impedance: 2.5K: 4-8 Ohm, 5K: 4-8-16 Ohm (standard), other impedance per request.
• Primary inductance: 28H
• Primary current: 150mA maximum
• Leakage inductance: 35mH, leakage capacitance: 114nF
• Frequency response: 30Hz – 30KHz
• Weight: 1.5KG per piece
• Size: 70mm x 80mm x 70mm
• Suitable for: 45, 2A3, 6P1, 6P14, 6V6 and etc

Quad C Core Input / Pre-Out Transformers (steel) – QCFEIP-S01

This is made using 8 pieces of C-core per transformer, having 16 pieces altogether for a pair of high end quad C core steel input or pre-out transformer (parafeed). 

This is suitable as an input / pre-out transformer between source and amplifier, pre-amplifier and power amplifier for galvanic isolation, noise reduction, increase/decrease gain, impedance matching and ground loop breaker.  If you use it as step-up, please ensure your source impedance is low enough to drive 600 Ohm load. 

• Area of applications: SPUD (single tube amplifier), pre-amplifier, buffer, and etc.
• Available types: 1:5.8 or 5.8:1; 600: 20K Ohm or 20K: 600 Ohm
• Primary impedance: 600 Ohm, secondary impedance: 20K (can be reversed)
• Inductance: 10H: 80H, DCR: 118: 760 Ohm
• Current: NO DC ALLOWED.
• Secondary inductance: 80H, DCR: 760 Ohm
• Leakage inductance: 0.052H, leakage capacitance: 3.2nF
• Frequency response: 20Hz – 35kHz
• Weight: 1KG per piece
• Size: 80mm x 65mm x 60mm

Amorphous Double C Core Output Transformers (nickel steel alloy) – DCAMOPT-X01

This is made using 4 pieces of C-core per transformer, having 8 pieces altogether for a pair of high end amorphous double C core nickel steel alloy output transformer for tube amplifier. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: single ended and push pull
• Primary impedance: 8K+8K (16K): 4-8-16 Ohm (standard), other impedances per request
• Primary inductance:  50H + 50H
• Primary current: 240mA maximum
• Primary DCR: 198 + 198 Ohm, Secondary DCR: 0.70 Ohm (@ 8 Ohm tap)
• Frequency response: 20Hz – 25kHz
• Weight: 3.2KG per piece
• Size: 100mm x 80mm x 120mm

Amorphous Double C Core Output Transformers (nickel steel alloy) – DCAMOPT-L01

This is made using 4 pieces of C-core per transformer, having 8 pieces altogether for a pair of high end amorphous double C core nickel steel alloy output transformer for tube amplifier. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: single ended, push-pull(customize)
• Primary impedance: 3.5K: 4-8-16 Ohm (SE, standard), other impedances per request
• Primary inductance: 16H @ 100Hz,
• Primary current: 150mA maximum
• Primary DCR: 140 Ohm, Secondary DCR: 0.65 Ohm (@ 8 Ohm tap)
• Leakage inductance: 9mH, leakage capacitance: 12nF
• Frequency response: 30Hz – 30kHz
• Weight: 1.5KG per piece
• Size: 82mm x 65mm x 100mm
• 3.5K / 4-8-16 Ohm

Amorphous Double C Core Inter-stage Transformers (steel) – DCAMIT-L01

This is made using 4 pieces of C-core per transformer, having 8 pieces altogether for a pair of high end amorphous double C core inter-stage transformer for tube amplifier.

• Available types: single ended (standard), splitting (customize)
• Impedance ratio: 1: 2.25(standard), per user request.
• Inductance: 55H: 80H, DCR: 260 Ohm: 540 Ohm
• Current: 100mA maximum
• Suitable driver tubes: 2A3, 300B, 6V6, EL34 to drive 805, 845, 211 tubes.
• Weight: ~1KG / piece
• Size: 60mm x 80mm x 100mm

Amorphous Double C Core Choke (nickel steel alloy) – DCAMC-M01

This is made using 4 pieces of C-core per transformer, having 8 pieces altogether for a pair of high end amorphous double C core nickel steel alloy choke. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: air-gapped choke (various sizes within core permit able values)
• Primary inductance: 8H
• Primary current: 300mA maximum
• Primary DCR: 70 Ohm
• Weight: 1.2KG per piece
• Size: 60mm x 75mm x 90mm

Potted Amorphous C Core Output Transformers (nickel steel alloy) – SCAMOPT-M01 (new)

This is made using 2 pieces of C-core per transformer, 0.01mm lamination thickness, having 4 pieces altogether for a pair of high end amorphous C core nickel steel alloy output transformer for tube amplifier. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: single ended (300B and etc)
• Primary impedance: 3.5K: 8 Ohm  
• Primary inductance: 12H
• Primary current: 100mA maximum
• Primary DCR: 70 Ohm, Secondary DCR: 0.7 Ohm
• Leakage inductance: 3.7mH, leakage capacitance: 10.2nF
• Frequency response: 30Hz – 35kHz
• Weight: 1.5KG per piece
• Size: 80mm x 85mm x 100mm

Potted Amorphous C Core Output Transformers (nickel steel alloy) – SCAMOPT-M02 (new)

This is made using 2 pieces of C-core per transformer, 0.01mm lamination thickness, having 4 pieces altogether for a pair of high end amorphous C core nickel steel alloy output transformer for tube amplifier. The amorphous C core is very thin and extremely brittle. Please do not drop the transformer to prevent damage. Take precaution when installing the transformer.

• Available types: push pull (EL34, 6P3P, KT66 and etc)
• Primary impedance: 6.6K: 8 Ohm  
• Primary inductance: 80H
• Primary current: 150mA maximum
• Primary DCR: 837 Ohm
• Leakage inductance: 3.7mH, leakage capacitance: 10.2nF
• Frequency response: 30Hz – 20kHz 
• Weight: 1.5KG per piece
• Size: 80mm x 85mm x 100mm

Notes: 

• Please do not order if you cannot accept blemished cores. Some can look as bad as pictures but below, some has only minor oxidation. They're only superficial (on the surface) and does not affect the operations at all.
• There may be slight physical outlook variations between what is posted here and what customers would received as batches of cores might have slight different look and sizes.  
• There may be core imperfections and/or slight core misalignment due to the facts that they are refurbished cores. We oversize the core so that this defect will not affect the performance of the units. Please look elsewhere if you cannot accept this.

J&K Audio Design

27 FEB 2014

Product Lists  
Level 0

Level 1: link 1, link 2, link 3

Level 2: link 1, link 2, link 3, link 4, link 5, link 6 

Level 3: depends on type, size and complexity. Email us for details.

Iso-trans: link 1, link 2

* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.  

* Our product lines are always improving and increasing. If you do not see what you want, contact us!  

* Please email for volume discounts, distributor and OEM pricing.