Everything is about money, money and money nowadays. With the ever rising living cost, coupled with poor money management of you know who, added with GST, it is harder and harder to survive nowadays.
What can we do if we still want high performance with little money involved? Well, you've got what you ask for today! When people talks about tube preamp, the first thing that associates that with high quality is tube preamp with output transformer, WOT Preamp as some call it.
Wait a minute. Output transformers are expensive, aren't they? Tube preamp or linestage output transformer are expensive too, right? Especially the high performance ones! Well, you are right! Or, you were right, till we offered the ALOS series of output transformers.
I believe this has slipped some of our follower's eyes. It's alright. We are re-introducing this baby here again. It is being disguised as Head-Phone output transformer, that's why it slipped most eyes that wanted a tube preamp output transformer. Take a look below!
ALOS Output Transformer link
| ALOS-75HP | Power: 2W(20Hz) Single Ended Bandwidth: * Pentode: 20-65kHz -3dB * Triode: 10-60kHz -2dB Primary: 7.5K; Secondary: 0-150-300 Ohm Core: 35H360 (H14) EI66 Pri. DCR: 506 Ohm(B-P) Sec. DCR: 38 Ohm (0-300 Ohm) Primary Inductance: 50H(40Hz, 5Vrms) Primary Current: 40mA (50mA max) * Matched in actual operating conditions. * DCR <1%, Primary Inductance <5%. |
U$99/pr |
Yes, you got it right! It is only U$99/pr. Of course, with such price, you can't expect too much out of it too, but the specifications are very decent, and decent enough to be used in not just low cost tube preamp where it can be considered as high performance tube preamp where the preamp output transformer actually boasts of 10Hz - 60KHz @ -2dB frequency response in Triode mode.
Tell me, how many speakers actually can reproduce such frequency response? Very few. And for those who owns these speakers, they don't mind paying for our higher end output transformers with better specs anyway.
This low cost tube preamp output transformer has a highish primary impedance of 7.5K with a handsome primary inductance of 50H. It comes with primary current of 40mA too. That is good enough for most of the preamp tubes out there, or even small power tubes. If you use tubes with low Rp (plate impedance), you can actually widen the already quite decent bandwidth.
The secondary comes with 2 taps, and is configurable to single ended output or balanced output. The 150 Ohm tap is the center-tap, the 0 Ohm and 300 Ohm taps are the +/- taps. Now this gets even better, right? It is now a low cost high performance balanced tube preamp with output transformer! I bet a lot of the commercial can't even come close to your design if you do it right.
The output impedance can be configured to 150 Ohm or 300 Ohm, which is low enough for most power amplifiers, even solid state versions. What about the gain of this tube preamp output transformer? x = gain.
- Z2/Z1 = x2
For 150 Ohm output, x = SQRT of (7500/150) =7 (7:1 step down)
If you power amplifier needs 2Vrms for full power, then anything tube with a gain of 7 or more will be sufficient for this low cost tube preamp. I can already think of many in my mind - 5687, 5842, 6C45, EL84, EL83, 6DJ8, 6922, 7119, E88CC, EC88, C3M, C3G, and many, many more...
With the low pricing of ALOS-75HP, one can even buy 4 units and make it a true 4 channel preamp! They can drive 2 monoblock power amplifiers and 2 subwoofers, or 4 monoblock power amplifiers for bi-amping! Fun right?
So, why wait, go ahead and order 4 units from us for your low cost high performance tube preamp project!
P/S: do not forget that this can be used as headphone output transformer too!
J&K Audio Design
4/14/2015
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