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how to build a pre using S&B TX-102 transformers
how to build a pre using S&B TX-102 transformers
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Old 23rd December 2004, 10:49 AM   #21
Sigurd Ruschkow is offline Sigurd Ruschkow  Sweden
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I just finished a prototype of a preamp with the TX102 and just a single input and output. ELMA 24-position rotary switch was used to switch between the 19 different attenuation levels.

I am using the +6dB mode as I need the extra voltage for my power amp.

The little wire that was needed is silver coated copper teflon insulated wire.

It was very simple to wire everything up.

With the output floating I got lots of hum and noise so I connected input and output ground together, and my system is now more quit than ever - no preamp that creates any noise :-)

Sound is wonderful!!! Soft, round, polished, lots of bass, maybe too much bass for male voices, detailed, with instruments that has clear focus, and the soundstage is excellent!

I also have the Sowther ones in the same box and also wired up to the same ELMA rotary switch.
I can thus check the sound quality between the Sowthers and the TX102s.
I have not tried them yet, though.



Sigurd
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Old 23rd December 2004, 07:30 PM   #22
KevinTams is offline KevinTams  United Kingdom
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Got my Tx102's wired in and running today. I had a similar problem to Sigurd in that I had my -ve's floating, the symptoms were a broadband mush of sound, sort of a white noise, but only at the -10db to 0db windings. I spoke to S&B who advised connecting the -ve's input to output, which I did at the RCA sockets, ..... result

Did I say result, I can't bring myself to turn the thing off now, to finish the job, I just keep playing record after record. And just for the record this replaces my passive pre which was a direct wired Alps "blue" pot and p*sses all over it. The improvements are far from subtle and improvements in all areas, imaging, information, tonal quality.

Thanks to everyone involved in this GP, this rates as a great VFM upgrade.

Kev
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Old 23rd December 2004, 09:03 PM   #23
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
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Konnichiwa,

Quote:
Originally posted by KevinTams
Got my Tx102's wired in and running today. I had a similar problem to Sigurd in that I had my -ve's floating, the symptoms were a broadband mush of sound, sort of a white noise, but only at the -10db to 0db windings. I spoke to S&B who advised connecting the -ve's input to output, which I did at the RCA sockets, ..... result
What must be understood is that you only float the output of the Transformer if there is an external connection between chassis/ground of source(es) and amp.

In my system for example the TV/VCR/DVD Player has earth through the TV aerial and the CD Player has earth trough the mains, as has the phono stage and of coursemy (tube) amplifiers are earthed. As a result I keep the output of the 102 floating and the sound is rather notably improved, even though I was able to minimise any hum coming through the various earth's path.

Hence you best always fit a switch that allows you to select which way, tehn if you ever change anything in the system....

Sayonara
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Old 23rd December 2004, 09:35 PM   #24
KevinTams is offline KevinTams  United Kingdom
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Kuei Yang Wang
Quote:
What must be understood is that you only float the output of the Transformer if there is an external connection between chassis/ground of source(es) and amp.
I'm trying to understand this one. My CDP is a Linn Ikemi, which I assume has the signal grounded to earth somewhere within it's circuitry. My power amps have the signal -ve terminated at the power star point, with this connected to the protective earth through a resistor, ( I think100ohm but don't quote me). So both of the transformer windings should have been earthed, but not through the signal -ve. Given that the fix worked means that something is amiss with my earthing, however I've a black silence between tracks with no hint of hum. The case of my pre will be earthed through the protective earth of the power amp. I'm still using the pre in rough form and still playing music, so I haven't yet wired my earths and -ve's as you suggested, maybe tomorrow if I can take it out and finish it.

I've not yet used my phono in circuit as I'm waiting for Origin Live to deliver my Silver arm, I've just bought an Acoustic Solid Small Royal and am itching to fire it up, so at present no vinyl
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Old 1st January 2005, 10:16 PM   #25
krishu is offline krishu  Europe
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Hi,

happy new year!

I got mine and did already build a simple magnetic pre ... it was soooo easy to do. I chose 0dB configuration and used an alps source selector and an Alps 23step switch. Until now it did not play for more than three records but even now I am satisfied .... an my expectations were huge after all that hype (and the price, of course)

I'll post pictures etc.next week

Cheers
Christian.
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Old 2nd January 2005, 05:30 AM   #26
darkmoebius is offline darkmoebius  United States
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Default Question for Kuei...

Can the TX-102's balanced output drive long interconnects (approx. 8 meters) like normal balanced drivers?

The preceding stage is a parallel TDA1541A dac and the amplifiers are monoblock single-stage MOSFET amplifiers with a load equivelent to the mosfet's gate load - Rterm=120K.


Quote:
Originally posted by Sigurd Ruschkow
I also have the Sowther ones in the same box and also wired up to the same ELMA rotary switch.I can thus check the sound quality between the Sowthers and the TX102s.
Please post your impressions as soon as you get a good feel for the differences.
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Old 2nd January 2005, 07:34 AM   #27
analog_sa is offline analog_sa  Europe
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how to build a pre using S&B TX-102 transformers
Quote:
Can the TX-102's balanced output drive long interconnects (approx. 8 meters) like normal balanced drivers?

The question really is whether the DAC can drive the long interconnects on its own. What follows the parallel 1541?
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Old 2nd January 2005, 04:41 PM   #28
darkmoebius is offline darkmoebius  United States
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Quote:
Originally posted by analog_sa
The question really is whether the DAC can drive the long interconnects on its own. What follows the parallel 1541?
Hi Analog,

I never thought of it that way, but now mentioned - it is incredibly obvious! TX-102'a are passive .
Hence, the preceding active stage provides all the drive/voltage.

The DAC is Tube-Lovers parallel design kit over on Audio Vender's Bazaar. The kit provides three different output stage choices: 6c45 SE, 6DJ8 SRPP and AD844 common based Op-amp output.

Having just re-read the manual, it seems that I can adjust the ouput level by varying the stock 33 ohm I/V resistors. The usuable range is between 20 and 68 ohms, the lower values resulting in greater output. I'll just have to hook my DMM and see what the true voltage range turns out to be.

I was hoping to maintain the purity of the TVC to amp connection(in theory), but I also have a few Burr Brown DRV134 balanced line drivers and INA2134 balanced line receivers here on my desk. I can always use those in a unity gain config to drive the long interconnects.

If need be, which would be best - inserting the line driver before the TVC or after?
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Old 2nd January 2005, 05:01 PM   #29
analog_sa is offline analog_sa  Europe
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how to build a pre using S&B TX-102 transformers
Hi darkmoebius

Call me prejudiced but i would steer clear from the DRV unless absolutely necessary. A 6S45 will be more than capable of driving the TX and the cable.

If you really must use the DRV it should be before the TX- these transformers really like being driven from a low impedance. Assuming zero driving impedance the output impedance after the TX is mostly determined by the dc resistance of the secondary and is low enough to drive a very long cable.
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Old 2nd January 2005, 07:50 PM   #30
darkmoebius is offline darkmoebius  United States
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Quote:
Originally posted by analog_sa
Call me prejudiced but i would steer clear from the DRV unless absolutely necessary. A 6S45 will be more than capable of driving the TX and the cable.
Makes a lot of sense to me. There is something incredibly simple and elegant about the TVC and to add an IC full of resistors, etc. into the picture kind of spoils it literally and figuratively.

I'll just have to see how things work out with all my sources and , if need be, have some of my inputs direct and others via DRV's. In reality, I only have a tuner, DAC, and video sound feed. Vinyl is something for future paychecks.

Quote:
If you really must use the DRV it should be before the TX- these transformers really like being driven from a low impedance. Assuming zero driving impedance the output impedance after the TX is mostly determined by the dc resistance of the secondary and is low enough to drive a very long cable.
Thanks for the explanation. I read and re-read the S&B page, but just wasn't getting the picture(it was 2am last night). Seems like the TX's will do just fine with my setup. If not, I can always add the DRV's to a few inputs that need help.
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