HiFi, Studio and Broadcast

HiFi Output transformers.

PUSH PULL, Advanced alloys intended for
Triodes, Tetrodes, Beam Tetrodes and Pentodes
@20Hz:15W, 25W, 50W, 100W ( 15, 30, 60, 120 / 20, 40, 80, 160  )

Pri Ω: 200, 625, 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 6000, 7000, 8000, 10000, 12000, 16000, 22000
Sec Ω: 2-4-8

Type number code:
PPUC3k5-50 = PushPull Ultralinear Cathode feedback, 3500Ω  , 50Watt
PP = Push Pull
PPU = Push Pull, Ultra linear
PPUC = Push Pull, Ultra Linear, Cathode feedback
PPC = Push Pull, Cathode feedback

SE = Single End
SEC = Single End, Cathode feedback
SEU = Single End, Ultra lineare
SEUC = Ultra lineare, Cathode feedback

Please, note that complete data and specifications will be added later.

200/800  Ω , 25W, ( Four-six primary windings ) Type PPU-02/08k-
EL 86, ED8000, ECC230, PL84, 12A4 , 12B4, 12E1, 13E1, 6AS7, 5998, 6080, 6082, 6336, 6337, 6528,

200/800 Ω , 100W
7241, 7242 , 6C33,
2k2 Ω , 5W Type PPU-2k-25
PL84, EL86,
2k5 25W
3k 100W
3k5 50W
3k5 100W
4K 15W

4k 100W
8417, T-110-1, KT8876550,
4k5 50W

4k5 100W
845, KT88/6550,
5k 15W,
5AQ5, 5CM6,EL12, EL83,
5k 25W

5K 50W,
5K 100W
EL51, KT88/6550,
6k6 40W
7k 25W
7k 100W
8k 15W
EL2, EL84,
8k 40W
8-9k 100W
EL156, 845, KT88/6550,
10k 15W
AL4,EL3N,EL11,EL33,EL84, EL95
10k 40W

12k 15W,

15k, 15W
24k 15W

Mainly TRIODES are suggested, but of course tetrodes and pentodes can be used just as well:
5W, 10W, 20W (40W )

600Ω ,  20W -150mA
7241,7242, 6336, 6528, 6C33,
1k5 10W

2k 10W
2k5 5W@30Hz,
AD1, PX4, R120, KT66*,
2k5 10W@20Hz

3k 10W

3k5 5W,

3k5 10W

3k5 20W
4k 20W
4k5 10W
5k 5W@30Hz
5V6, 6V6, EL5, EL84, 841, 842,
5k 10W@20Hz

7k 25W
8k 10W
AL1, AL2, EL81,5V6, 841,842,
10k 5W
EL81, 843,
10k 20W
12k 5W
12k 20W
845, T-110-1 ( 32W out )
15K 5W
16k 20W
203, 211/VT4, 238, 845
22k 5W,



Suggested well known tubes/valves:

Pentodes, Tetrodes:ECL86, EL6,EL12,EL34,EL41, EL42, EL60,EL80,EL82,EL86,EL86, EL90, EL96, EL156, EL803,KT55, KT66, KT77, KT88, KT120, PL84, PL509,
Triodes:AD1, DA30, DA60, DA100, DA250, DO30, DET25, PX4, PX25 , RE604. R120,

Pentodes, Tetrodes:6L6G, 6V6G, 807, 813, 6550, 8417, 8552, 8528, 7591,
Triodes:2A3, 6A3, 6B4G, 45, 50, 211, 245, 250, 275, 300B, 845


There is no such thing as an optional/perfect matching load to any valve. It depends upon too many variables, some of which are even changing in unpredictable manners when exposed to the complex signals of music. Other static factors plays a major role to the parameters that influence on the so called matching load. Anode Voltage, for tetrodes/pentodes in particular sg2 Voltage, bias and cathode circuit.
Increasing anode and/or sg2 Voltage will increase the matching load impedance and decreasing these voltages will decrease the matching load impedance, just to mention a few.
Ad to this the natural tolerance of valves min. +/-10% ( in particular pentodes and tetrodes ) and the variable impedance of speakers. ( + 100/ – 50 % or more )
There is an upper and lower impedance of which a valve will operate at its best, however this span is much broader than most valve datasheets seems to suggest and no sharp boundaries can be defined.
Further load matching can be based upon either maximum power transfer or maximum linear transfer.( Lowest distortion )
Triodes in particular are rather tolerant to a variety of load impedance and due to the low ri of triodes they will make a better job of getting the best out of the output transformer.

Based upon these facts it should be recognized that in the design process it is not worth to pay too much attention to load matching. A span of +/- 20% or more from the load alone are likely to appear in practice.
Hence, the load that sounds the best in your ears are quite likely to be the best match. But it will still change as you change your valves, even of the same type and in particular it will change with the speakers in use.

If power valves were perfect and always within a few percent, power supplies were perfect and well defined and speakers were a perfect Ohmic resistance, then we could indeed decide to match for either maximum power transfer or minimum distortion. But since they are not at all such perfect things, we need to address this theorem from a practical point of view. If not we will fool ourselves in to a theoretical optimal solution that does not exist in the real world.

You might wonder then, why do we offer such a broad range of impedance in our transformer range ?
We do this simply to allow the designer to pick the transformer that suits the need in question. Many users wish to design the loading impedance as close to the suggested points in the data sheets. The larger the range to pick from the better the chance are that you find the recommended load or your personal load preference.
In practice a range in doubles like: 600Ω, 1k2, 2k4, 5k, 10k would do fine and if we add 3k3, 4k5 and 8k and perhaps 14k we are all flying. We gave it a little more to allow our customers the best possible choice.

Why do we not offer 16 Ohm speakers loads as a standard option ?

Copper windings that are not in use will affect the quality in a negative way, mainly due to leakage. 16 Ohms speakers are very rare and has not been produced as standard items for more than 30 years.
Very few old 16 Ohm classics are still in use. Hence it would be fairly silly to produce all of our transformers with a permanent quality drawback, just in order to satisfy the few.
If you wish we can produce most of our transformers with a 16 Ohm tap upon request.

In my experience speakers in parallel always sounds better than speakers in series.Hence two 4 Ohm speakers would make a 2 Ohm load and two 8 Ohm speakers would make a 4 Ohm load and two 16 Ohm speakers a 8 Ohm load. As you see there is not much need for a 16 Ohm tap, and we would rather provide you with a 2 Ohm option.

It is always possible to connect an 16 Ohm speaker to the 8 Ohm tap. This will double the effective load as seen from the valves in use. In other words connecting a 16 Ohm speaker to the 8 Ohm tap of a 2500 Ohm transformer will change it to a 5000 Ohm load. This will slightly affect the centre frequency of the transformer and as such move the bandwidth of the transformer slightly upwards.
Keep in mind that It might not always be advisable to move the load of the valves in to twice as much as what the amplifier was designed for. You should do this only if you know what you are doing.

The magical 5000 Ohm load.

5kOhm Push Pull will fit almost any pair of valves, depending upon the working characteristics chosen. Only a few not often used valves will not work satisfactory in to this load.
It is possible to perfectly dial in the 5kOhm load of most LF power valves in a push pull set up.
Here just to mention a few: 2A3, 300B, AD1, PX 4, PX 25, 50, 211, 845, EL34, 6L6G, KT66, KT88, 807, 6V6G.

If in doubt, please consult the data sheets of the valve you intend to use.
A good source for data sheets:


Please, do also note that no valve ( or transistor ), what so ever, provides lower distortion above 30-40Hz than our output transformers. The lower the output impedance from the output stage, the better
you can gain from the low distortion from a well designed audio transformers.
Do also note that our Wattage are specified at 20Hz. At each octave above the specified Wattage the max power increases by a factor of 4.
This means that at 40Hz it is possible transfer 4 times the power stated. However the copper wire will not allow excessive current overload, hence you should not continuously
load the transformers by more than 4 times the specified power (Watt’s) and only between 40Hz- 3kHz.

Distortion 2,3,4,5 harmonics at 20Hz, 60Hz, 300Hz, 1kHz samt 10kHz. 1Watt and full power
Squares shown at 4V pp given load,
Freq at 1W and full power
Phase 20Hz- 20kHz.
Primary DC Ohm, Sec DC Ohm
Primary impedance tolerance +/- 5%
weight, HxLxB


X-pass transformers:





50mA FFR
100mA FFR
150mA FFR
High permeability

2500 Ohm/2-4-8- Ohm

3500 Ohm/2-4-8- Ohm

5000 Ohm/2-4-8- Ohm

7000 Ohm/2-4-8- Ohm

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