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Thursday, October 5, 2017

NOS Tubes Sound

What is true sound of NOS tubes? (Rants warning!)

Most NOS tubes players like to ask among themselves, what tubes do you roll on your amplifier? Or what tubes you like to play? How do you like their sound? 

Often, answers would be the manufacturer of the tubes, such as Western Electric, RCA, GE, Sylvania, Tung-Sol, GEC, and etc; or the model of the tubes, such as 300B, 211, 845, KT88, 2A3, and etc. 

For those with more advanced tubes knowledge, they would go into the year of manufacture, factory location, getter type/quantity, filament suspension style, plate structure, base type, special tube structure support, and such. 

Rarely, do people asks, what transformers are you playing with? People rolls tubes. They do not roll transformers. That's how it is now. I wish, some day, people would start rolling transformers too! 

One of the most important thing, other than the amplifier design itself, is the quality of the transformers, especially the output transformers! Without high quality transformers, no matter how good the tube are, the true sound of NOS tubes, or NOS tubes sound, can never be fully achieved or heard. 

When we talk about transformers, we are referring to things such as power trans, chokes, input / output trans, interstage and driver transformers as the main categories. 

All of them, play very vital roles in a tube amplifier. Don't even talk about NOS tubes sound if your transformers aren't done right in the first place. The quality of transformers will determine the sound quality, voicing, noise floor, linearity, scale, power delivery, transparency, tonality and all the parameters of having HI-FI sound. 

When we talk about transformers, all these below matter, just like NOS tubes.

* capacity
* lamination type and quality
* magnet wire type and quality 
* transformer electrical and mechanical design
* bandwidth 
* safety and longevity 

Something as simple as a choke, also varies in performance and sound. The grade of materials (core, wire, potting method, potting compound, bobbin, insulation, and etc), the design, the DCR, the inductance variances across frequency and load, and etc, are all different, and will affect the sound and electrical performance substantially. If one things that all chokes are built the same, think again. 

Try ordering a choke made with NanoCrystalline core with ultra thin lamination thickness, extreme low DCR design (example 5H 10 Ohm, compared to ordinary 5H 50 Ohm), OCC magnet wire, high grade potting compound/bobbin/insulation, adequately but not extremely oversized core, proper mechanical design (perfect wire strain and alignment), and compare it with a standard choke, one will witness the vast improvements one small thing like that will bring to the sound. 

If this is done on an output transformer, the difference will be much more significant! When we go into more complex transformers, such as the audio signal transformers, the factors impacting the sound increased exponentially, so as the sound. People often thinks about primary inductance as the basis for good low frequency response. That is not all. The primary and secondary winding DCR is very important as well. 

A 3.5K:8 Ohm standard output transformer often carries the DCR of 150-200 Ohm for primary, and ~1 Ohm for secondary. Try ordering a pair made with DCR of 30-50 Ohm for primary, and 0.1-2 Ohm for secondary, and with everything else staying the same, such as the primary inductance and bandwidth (Not all can do so. There's a penalty in price and size.). The result differences will be ultra significant! Hints: increase in dynamics, better power delivery, improve control, increase transparency, lower distortion, and etc). 

What I bring up here is just the tip of the iceberg and to get you to start thinking deeper. There are more than meets the eyes. 

From today onward, start thinking about rolling transformers, on top of rolling tubes. You'd be rewarded handsomely (better ROI in a lot of cases), since rolling tubes can be significantly more expensive than rolling transformers! Don't waste the NOS tubes if you don't play high quality transformers. 


Hear the unheard! Sail the uncharted! 
Long live custom made audio! 

J&K Audio Design

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