One of the most critical components in the tube audio are the transformers, audio and power. Below there are some useful information about new and vintage transformers.
Some useful directions for transformer picking.
1:1 ratio Line Level Transformers
Line level transformers can be used for ground isolation between different apparatus or for converting unbalanced to balanced lines and vice versa. For the physics of balanced lines please refer to the link. The practical reason for balanced lines is that you can have the preamplifier, DAC, computer, next to you and the amplifier across your listening area next or between the loudspeakers.
In the picture below there are some line transformers, far left is a pair of high Z Ampex transformers taken from an old four track 1/2 inch tape recorder, in the middle is a pair of UTC LS141 transformers that can serve also as a splitter, next is a pair of Peerless E204 600Ω/600Ω transformers.
All these are old and out of production transformers , my favourites and recommended of new production are Sowter 3575 or 1470 and Lundahl 1684 and 1690 .
Moving Coil Cartridge step-up transformers
In case your phono preamplifier does not support MC cartridges it is certain that you might need a moving coil step-up transformer.
On the left in the picture below there is a pair of Harman Kardon XT-3 Microphone transformers. On the right there is a couple of UTC-016 and LL1681 (on the top) transformers. In the middle on the top there is a pair of Sennheiser microphone transformers and on the bottom is a pair of Lundahl 1922 transformers .
Be sure that there are a lot of X-lent step-up transformers of new production out there. Some that I have tried with good results with the Denon DL 103R cartridge is the LL1681 @ 1/13, the LL1922 connected in 1/8 configuration and also the LL1678 @ 1/16 configuration.
A future experiment will be the Sowter 9990 @ 1/20 ratio.
I have to inform you that I don’t recommended step-up ratios higher than 1/16 as extreme high ratios make problematic transformers. Also keep in mind that a cartridge that produces an output of less than 1/2 mV can not excite properly most step-up transformers.
Also note that you must break free from the madness of seeking vintage shitty and rare transformers just because someone claims that they are the Holy Grail for MC cartridges.
Single ended and Push-Pull Output Transformers
Undoubtedly my favourite output transformers for SE or PP configuration are the Japanese, made by Tamura, Hashimoto, ISO or Tango. They don’t just look nice but they are of the best quality. Unfortunately they cost a king’s ransom but they worth every yen. So if you can afford them, please use them.
I have to add in my favourites list the X-lent, Swedish Lundahl transformers that are a mind puzzling riddle to connect and as beautiful as a SAAB car.
The honourable mention goes to the One Electron UBT-3 transformer which is a killer bargain for its sound quality.
The Bass Reflex Experiment
The experiment started with a box of 35 litres and a port of 8cm diameter x 18 cm length. The drivers used were Fostex FE207E full range and Fostex FT17H tweeter. The cutoff capacitors used were in the range of 0.47µF ≈ 1.5µF. After extended listening the Fostex tweeter was replaced with a Vifa for smoother sound. The conclusion was that there was no need for any tweeter so the Vifa stayed in place just to block the hole. The next trial was with a pair of bullets (phase plugs) that made the sound more focused but in conjunction with the paper cone driver they could make your ears bleed. So off with theme bullets. The last trial was the Dammar varnish (Talens Dammar Varnish Glossy No : 081) that was applied on the inner cone of the FE207E and stayed for drying over night. Alas finally everything sounded as it was supposed to do.
In conclusion the best that can happen in a single driver bass reflex speaker, is the Dammar varnish.
I have to mention that the box was treated internally with sonex acoustical foam.
THE LOUDSPEAKER ODYSSEY
There have been many changes in electronics but the only apparatus that seems to stay the same is the loudspeaker.
This is the Fostex T90A tweeter on a wooden base
The next experiment was with a box of 45 litres in volume employing a port of 8 cm in diameter and 6 cm in length. The box was treated internally with sonex acoustical foam. Dammar Varnish was applied on the inner cone of the FE207E and a Fostex T90A tweeter was employed. The cutoff capacitor was 1.5µF/200V PIO and an L-Pad was used to lower its volume. After extensive listening the tweeter was too much for my taste so it was abandoned.
In case you are interested the difference between the 35 and 45 liter box is that the 35 L has punchier lows than the 45 L that sounds more relaxed at the bottom end.
I could risk to make the analogy of an electric bass compared to a double bass.
On the left is the finished loudspeaker having volume of 45 liters, the port is 8 cm diameter and 6 cm long.
On the right is the stand of the speaker which is H shaped steel 24 X 23 cm, 30 cm high and weighs a ton.
Fostex FF165WK in Bass Reflex Box
Having tried several Fostex models of the FE series, I wanted to try my luck with the FF series .
After some careful thought, the FF165WK driver was chosen and put in a 18 litre bass reflex box tuned at 54Hz, as recommended by Fostex.
The sound was rather impressive, especially at the lower end, but the high frequencies sounded as if the box was covered with a blanket.
The need for a tweeter was eminent and a pair of T90As was handy, so they were added with a first order high-pass filter. That filter was a capacitor in series with the positive transfer line. Several values were tested before choosing.52µF as the final value.
The sound improved immensely, but there is space for more experimentation, so the next step will be the trial for a second order high-pass filter at the 10Khz range and the use of a T-pad.
High Pass Power Filter For The T90A Tweeter
A pair of high pass second order Linkwitz-Riley filters @10Khz were built for the Fostex T90A tweeters to compliment the FF165WK bass reflex speakers (pictured below). The capacitor used is Sprague Atom Vitamin Q 1µF/200V and the T-pad is Clarostat CIT 43 - 8Ω.
The HP filter could be @ 8Khz, build with the values in yellow lettering but an LP filter @ 8Khz is mandatory for the FF165WK as phasing might occur among other artifacts.
Commission On A Tight Budget
Building a pair of loudspeakers on a tight budget is not an easy task especially when you realize that the box costs far more than the driver.
To cut a long story short on the left is one of the bass reflex loudspeakers that employ the Visaton BG20-8 drivers in a 30 lit. enclosure tuned @ 40Hz.
Note that the price justifies the sound of the drivers. There is a distant plan that the place of BG20-8 will be taken by the Fostex FF225WK.
The UREI 813 Experience
No matter what is said for those speakers it’s not enough. Unfortunately is the kind of speakers that will be never produced again. It has endless hours of research on its back and some patents as their Time Aligned X-overs.
I drive these loudspeakers with an 8 watt 300B SE amp. and trust me I get enough db SPL to throw a party.
Their sound is as big as their volume, 325 litres, and that’s are the reason I build a smaller version in an 250L enclosure with a different crossover .
The final product in a 250lit. enclosure using just the UREI 604 driver .
Here is one of the finished loudspeakers with the 604 drivers and the N-1500 X-overs in the 250 liters vented boxes.
These loudspeakers are not the ones that the average music lover would put in his living room but trust me they are the ones that it is worth listening music to.
It is the kind of loudspeaker that brings out the best of good recordings and spares nothing to bad ones. It is a huge and very loud monitor that devours complex waveforms and makes cheap nintendo/reason productions sound as they have to, like shit.
I think there is no reason to mention their strength to the low end of the spectrum that is so vivid that takes your breath away and gives you the feeling of a panic attack if played loud.
They are not as analytical as the Fostex FE207 in the mid range region nor as responsive in fast transients but they are the monitors to listen to your final product after a long day’s remixing.
They are not the kind of book shelve speakers that are used for ambient noise but the ones to let you dive into music.
For the faint at heart, the ones that take in account the WAF factor, a loudspeaker like this one is a good reason for rebellion.
It is usually useful to have a Vu meter indicator for checking the levels in a listening or recording chain as you can visually spot mismatches.
Here is a vintage Neumann U472 Vu meter taken from an old mixing desk and put in an aluminum Hammond box where XLR connectors were added and an external 24 V power supply.
This Vu meter indicates 0 db @ 0.775 V RMS and has balanced inputs. Nowadays there is a plethora of analog Vu meters that are scavenged from old analogue mixing desks or tape recorders, of course there are also several of new production made in England by Sifam and distributed by Canford, so it is fairly easy to get a pair and add them in your setup.
Cables and Snake Oil.
In this picture you see how we saved the snake but put it in service to provide power for a pair of SE mono-block amps (8 Watt each), their pre, RIAA pre and turntable.
The plug and the “snake” are for three phase power line and are rated @ 406A per phase. The phases are divided as follows: one for the amplifiers left channel the next for the right channel and the third phase is used for the pre, RIAA and turntable.
I have to say it was a revelation for dynamics, speed, bandwidth and stereo image the use of such a power cord. :-)
You might think that the story ends with the stupid that spends a kings ransom for cables, but alas, there are morons that pay money for magical and mystic devices.
DIVICES FOR MORONS
WHERE PSEUDOSIENCE THRIVES
As I mentioned earlier, it is not only the stupid that spend a king’s ransom for cables, but, alas, there is a whole list of stuff for morons to get them money for nothing in return.
A short list of gadgets that really exist follows.
1) Cable cooker, as if the cables were spaghetti and need
2) Vinyl records demagnetiser, as if vinyl records were/are
made using magnetic material.
3) Magic chip stickers that improve sound and cure disease.
4) Minuscule, also magic, filters that purify and improve
5) Cryogenic treatment of devices as if they are Timothy
Leary’s much-missed brain.
6) Toy Resonators of any kind (electrical or passive)
promising to save your listening area.
7) Products made with Unobtainium sprinkled with Eludium.
8) Harmonizers and Enhancers for your AC power line.
9) Voodoo Stones called Sonic Purifiers, self explanatory
The list goes on and it will grow as I suspect that some sound aficionados are using Pangolin Scales in order to perceive 7D Holographic sound.
Also be aware of the quacks that refer to quantum physics in order to convince you about their fraud.