Browse Categories
Browse by Manufacturer

Hammond 125 Series Universal Single Ended or Push-Pull Output Transformers

Open style with minimum 5" long primary leads, secondary solder lugs for convenient secondary connections. Tables provided with each transformer listing 90 precalculated impedance ratios. Primary impedances from 1,200 to 25,000 ohms, so you can use virtually any output tube, single-ended or push-pull. The three primary wires obey the standard color code for push-pull output tranformers; the blue and brown wires are plate leads, the red wire is the center tap. For SINGLE-ENDED use of the output transformers in the 125 Series, simply use the two blue and brown plate lead wires; just tape off the red center tap wire. We have recently confirmed this hookup information with the technical staff at Hammond. Secondary impedances from 1.5 to 15 ohms. See this page for 125 Series Impedance Table. For more information on using this table check out the commentary on the Simple 6V6 Guitar Amp Project under the How To Section of this website.

For 125 Series

The following is some commentary taken from our How To Section 6V6 Guitar Amp Project on how to read this chart:

If you're using the popular Hammond 125E you'll have to choose which primary impedance you'd like to try; since many are available (between 1.2K and 25K) offering different tonal choices. The 'textbook' primary impedance choice for a single-ended 6V6 is around 5K, athough you might want to try anything between 3K and 8K. Lower primary impedances will give you slightly more power output and more distortion, the classic design 'trade-off'. For hi-fi, a higher than textbook primary impedance is currently fashionable in hobbyist circles, since it offers a more linear sound with less distortion at only slightly less power. For guitar amps, anything goes. The impedance YOU dig is the 'good one', and this is pretty easy to mess around with if you choose the 125E. Even a monkey with a soldering iron might hit the right two solder lugs (there's only six lugs....all found on the secondary side of the coil). Some classic vintage guitar amps apparently used lower than textbook primary impedance output iron by design. Keep in mind that such a choice was usually a few pennies cheaper in the '50s, so maybe that had something to do with it. Look at the top column of Hammond's hookup diagram (found on the packing box of the transformer) and find your speaker impedance (e.g. 8 ohms), then scan down to the closest primary impedance for a single 6V6 (for starters, try "5600" ohms...), then scan over to the left hand column and it'll tell you exactly which two of the available six lugs to hook your dang speaker to, right? For example, if you have an 8 ohm speaker and want to select a primary impedance of "5600" ohms, hook the two speaker terminals to lugs 1 & 5. Isn't D.I.Y. guitar amp building easy? You know it! By the way, the 125E was designed as a 'Swiss Army Knife" push-pull OR single-ended transformer: for single-ended use in this project, use the BLUE and BROWN wires only, hook 'em up to the same circuit points as you would the Fender 10W output iron described above. The BROWN wire of the 125E goes to lug #3 (the plate) of the 6V6GT, the BLUE wire goes to lug #4 (the screen grid) of the 6V6GT. Just 'cap off' the additional RED wire (the center tap...) with a wire nut. Choose the appropriate two lugs on the secondary side of the 125E according to the impedance ratio table included with that transformer. By the way, it doesn't matter which of the two output lugs you designate as positive (+) or negative (-), just hook the two wires to your speaker and it'll work fine.
Voice Coil Impedance 

Connect To:

1.5 ohm 2 ohm 3.2 ohm 4 ohm 6 ohm 8 ohm 12 ohm 15 ohm
1 - 2 27000

2 - 3 18000 24000

3 - 4 16500 22000

4 - 5 10000 13500 21600 27000

5 - 6 8500 11000 18000 22000

1 - 3 5400 7200 11500 15000 21600

2 - 4 4200 5600 9000 11200 16800 22500

3 - 5 3300 4400 7000 8800 13200 17600 26400
4 - 6 2400 3200 5100 6400 9600 12800 19200 24000
1 - 4 2150 2900 4600 5800 8700 11600 17400 21500
2 - 5 1550 2050 3300 4100 6150 8200 12300 15500
3 - 6 1300 1700 2700 3400 5100 6800 10200 12800
1 - 5
1400 2200 2800 4200 5600 8400 10200
2 - 6

1700 2100 3150 4200 6300 8000
1 - 6

1200 1500 2300 3000 4500 5600

Due to the large number of Hammond model numbers it is not possible to keep all items in stock.
We have some Hammonds on the shelf but otherwise we order them as we get orders.
Out of stock items will be shipped approximately one week after you place your order. We can special order any Hammond product for you.  Let us know the Hammond model number and we will quote you a price.

Displaying products 1 - 6 of 6 results
Hammond Output Transformer 125A
Price: $33.00
Hammond Output Transformer 125A
Hammond Output Transformer 125A
Hammond Output Transformer 125B
Price: $35.39
Hammond Output Transformer 125B
Hammond Output Transformer 125B
Hammond Output Transformer 125C
Price: $34.19
Hammond Output Transformer 125C
Hammond Output Transformer 125C
Hammond Output Transformer 125D
Price: $37.19
Hammond Output Transformer 125D
Hammond Output Transformer 125D
Hammond Output Transformer 125E
Price: $37.79
Hammond Output Transformer 125E
Hammond Output Transformer 125E
Hammond Output Transformer 125H
Price: $32.79
Hammond Output Transformer 125H
Hammond Output Transformer 125H

Shopping Cart
Your cart is empty.