Audiophile Tube Output Transformers
Whether you are into the clean, free spirited “Single Ended” tube output or high efficiency, high power, “Push-Pull” audio, Hammond has the output transformer for you.
Hammond has been producing tube output transformers continuously for over 75 years, constantly improving and tweaking their performance. The output transformer is one of the most critical components in an audiophile amplifier. These excellent designs have survived the years and have enjoyed a recent resurgence along with the tube industry.
Please note, Hammond specifications are at FULL OUTPUT power. Many “newbies” to the industry use frequency specification data at milliwatt ranges to inflate their claims. Check carefully when comparing manufacturers specs. Hammond uses -1db roll off points to ensure a typical HAMMOND conservative rating, again at FULL OUTPUT POWER.
To ensure a long life and maximum versatility these units are built to and tested at a Hi-Pot rating of 2,000 VAC RMS.
Hammond transformers are of EI laminated design, and do not offer toroidal designs due to their inability to handle tube imbalance and high manufacturing cost.
More importantly, Hammond’s designs are “ear tested”. After a new design has passed their extensive testing, it’s got to sound good too, before they put it on the market! From Bach to rock & three watts to 280 watts, DigiKey most likely has your Hammond output transformer in stock.
Single Ended Tube Output Transformers
These high-quality units are designed for maximum versatility. Designed for both triode or pentode operation - Class A operation. All units include an optional use - 40% screen tap (a proven pentode “sweet spot”) for “Ultra-Linear” operation. The ratings shown are at full power and rated plate current. Available in 25-75 watt models (1627-1642 Series). The lamination iron used is a high quality (M6) grade, silicon steel, for low loss and the lowest possible distortion at bass frequencies. A factory set core gap ensures against core saturation at full ratings. All single-ended output models include multiple interleaved windings to maximize high frequency response. These windings are machine wound with high quality copper wire. If you do not need hi-fi ratings or are restoring older equipment using single ended audio output - refer to the economical 125SE Series optimized for single ended - universal - general purpose use. Available in 3-25 watt models.
Push Pull Tube Output Transformers
These high quality units are also designed for maximum versatility. All units include an optional use - 40% screen tap (a proven pentode “sweet spot”) for “Ultra-Linear” operation. They are designed to be used with most all power output tubes available today. The ratings shown are at full power and rated plate current. Hammond has also added an epoxy potted series to their line for the ultimate in tube output transformers. Available in 10-280 watt models (1608-1650 Series). If you do not need hi-fi ratings or are restoring older equipment using push-pull audio output - refer to the economical 125 Series optimized for push-pull - universal - general purpose use. Available in 3-15 watt models.
HAMMOND Interleaved Windings
The reason for Hammond sparkling high frequency performance is the use of interleaved windings between the primary and secondary. The number of interleaved windings is optimized to the size (wattage) of the unit. All high fidelity output models (both single ended and push-pull) include multiple interleaved windings to maximize high frequency response. These windings are machine wound with high quality copper wire The multiple interleaved secondaries are wound (series or parallel connecting them) to match to 4, 8 or 16 ohm load impedances. The primaries of each model (including the “single-ended” series) include Ultra-Linear taps at the 40% point.
Tube Output Transformers - Aesthetics
Hammond has also paid close attention to the “look” of their units as they are as much on display in some designs as the tubes themselves. Hammond’s high-fidelity units are manufactured with high grade laminations (M6) and machine wound with high quality copper wire. The core is varnished and oven baked to ensure quiet operation - even at high ambient temperatures. Then the end bells are bolted on. These end bells are finished in a tough, low gloss, black powder paint finish to resist scratching.
Transformer Overview Summary
1627-1642 Series
Features
-
“Over designed” for high fidelity, single ended, Class-A, tube output circuits (triode, tetrode or pentode tubes).
-
Enclosed (shielded), four slot, chassis Type “X” mounting.
-
Frequency response at least 20 Hz. to 20 Khz. at full rated power (+/- 1 db max., ref. 1 Khz.)
-
Insulated flexible leads 8" min.
-
For maximum versatility, all units (except the 1642SE & 1638SEA) include a 40% screen tap for Ultra-Linear, tetrode/pentode operation (if desired). The 1642SE & 1638SEA do NOT include this screen tap as they were designed principally for high impedance triode tubes.
-
High quality laminations, (M6) grain oriented silicon steel.
-
Core is gapped to reduce core saturation in Class-A tube amplifier circuits.
-
For general purpose or replacement use in single ended tube output circuits see our 125SE Series.
- RED wire connects to B+
- BLUE/YELLOW wire connects to screen (optional use)
- BLUE wire connects to the tube plate
- The 1642SE & 1638SEA do not include a primary screen tap (as they are designed for triode applications).
Notes: The above examples of possible combinations are to help you narrow down the choices of transformers for your favorite tube types. How you operate the tubes (ultra-linear, bias, plate voltage, operating points, etc.) will change optimum plate load impedance. Only a few of the most popular tubes are shown. A tube manual or tube manufacturer’s technical data sheets should be consulted first, before making a decision on a proper output transformer.
125SE Series
Features
-
Designed for general purpose or replacement use (not Hi-Fi), in single ended, tube output circuits.
-
Frequency response: 100 Hz. - 15 Khz at full rated power (+/- 1db max. - ref. 1 Khz).
-
For full frequency response (20 Hz. to 20 Khz.) - see our 1627-1642 Series.
-
For push-pull output use, see our 125 Series.
-
Open style with minimum 12" long primary & secondary leads.
-
All sizes use butt stacked cores (using 29M6 steel) with an air gap, to reduce D.C. core saturation.
-
Primary impedance range from 2,500 to 10,000 Ohms.
-
Secondary impedance range from 4 to 32 Ohms.
1608-1650 Series
Features
- Please see our NEW & improved versions (easy wire secondary) 1608A-1650A Series.
- Designed for push-pull tube output circuits.
- Enclosed (shielded), 4 slot, above chassis Type “X” mounting.
- Frequency response 30 Hz. to 30 Khz. at full rated power (+/- 1 db max. - ref. 1 Khz) minimum.
- Insulated flexible leads 8" min.
- Manufactured with plastic coil forms for coil support and insulation.
- Typical applications - Push-Pull: triode, Ultra-Linear pentode, pentode and tetrode connected audio output.
- Due to the unique interleaving of the windings BOTH secondary windings must be engaged to meet specifications (see hook-up diagrams below).
- For the “ultimate” in Push-Pull output see our line of epoxy potted output transformers.
1645 Only
- Secondary Connections (Due to the unique interleaving of the windings BOTH secondary windings must be engaged to meet specifications)
- To hook up 4/8/16 ohm secondary loads - see schematic (do not use the white wire).
- To hook up secondary to 70V loads, jumper Blk/Yel wire to Grn wire. Connect load to Blk and White wires.
Notes: The above examples of possible combinations are to help you narrow down the choices of transformers for your favorite tube types. How you operate the tubes (push-pull, push-pull parallel, ultra-linear, class, B+, bias, operating points, etc.) will change optimum plate to plate load impedance. Only a few of the most popular tubes are shown. As more tubes become available we will add them to the list. A tube manual or tube manufacturer’s technical data sheets should be consulted first, before making a decision on a proper output transformer.
125A-125E Series
Features
- Designed for general purpose or replacement use in push-pull tube output circuits.
- For single ended use, see our 125SE Series.
- Frequency response: 150 Hz. - 15 Khz at full rated power (+/- 1db max. ref. 1 Khz)
- Open style with minimum 5" long primary leads.
- Secondary solder lugs for convenient secondary connections (except 125B - uses minimum 5" secondary leads).
- Primary impedances from 1,200 to 25,000 Ohms.
- Secondary impedances from 1.5 to 15 Ohms.
- For smaller sized units (but fewer impedance options) see our multiple impedance 125H Series.
Source - Hammond - Classic Tube Output Audio Transformer Overview
Click Here for all Hammond Transformers
Click Here for all Audio Transformers