TVC Linestage (BD-Design)

by GC, Thursday, March 17, 2005, 22:51 (4695 days ago)

Hi,

The TVC has I think S&B transformers which come with this warning:

The input to the TX-102 must be COMPLETELY free of DC offset; the presence of DC current materially degrades the performance of the TX-102 Transformer, both with respect to level handling and frequency response.

Has anyone experienced this degraded performance from using a dc coupled source?

Also, the output impedance of the Twindacplus! is 2.5k ohm and the TX-102 suggests a number closer to 60 ohms. Has anyone noticed any bass roll-off due to this?

Cheers,
Brian

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by GC, Saturday, March 19, 2005, 21:10 (4693 days ago) @ GC

Hi Brian,

With a normal designed DC coupled system the DC voltage will be very low and therefore not much of a problem. The high total impedance with some DC mV will only give very little current (nA).

Don't connect a tube pre-amplifer without output capacitor, then it won't work too well I guess... :)

Also, the output impedance of the Twindacplus! is 2.5k ohm and the TX-102
suggests a number closer to 60 ohms. Has anyone noticed any bass roll-off
due to this?

The load on the other end dictates the load on the input. The higher the input impedance of your amplifier the higher maximal output impedance is needed on the input of the TVC. A tube amp with minimal 50k input (better would be 100k) will not be any problem for the 2.5k ohm.

Ciao,

Bert

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by GC, Sunday, March 20, 2005, 20:41 (4692 days ago) @ GC

Thanks Bert,

The load on the other end dictates the load on the input. The higher the
input impedance of your amplifier the higher maximal output impedance is
needed on the input of the TVC. A tube amp with minimal 50k input (better
would be 100k) will not be any problem for the 2.5k ohm.

The input Z of the power amp I'm considering is 100k.

Another thought, does the TVC convert single ended inputs to balanced output?

Cheers,
Brian

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by GC, Sunday, March 20, 2005, 22:33 (4692 days ago) @ GC

Hi Brian,

Another thought, does the TVC convert single ended inputs to balanced
output?

I don't think so in reality but I might be wrong... I am a speaker builder/designer and learning bits and pieces about electronics along the way, hardly enough knowledge so far to be able to educate people.

Ciao,

Bert

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by GC, UK, Monday, March 21, 2005, 17:18 (4692 days ago) @ GC

Another thought, does the TVC convert single ended inputs to balanced
output?

Cheers,
Brian

Hi there, are the Brian from Basingstoke that came to see me and my Oris system? If so hi, and I'm pleased you made the move!

I obviously didn't put you off then!

Kind regards,

Jonathan

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by GC, UK, Monday, March 21, 2005, 17:26 (4692 days ago) @ GC

Another thought, does the TVC convert single ended inputs to balanced
output?

Sorry I also meant to comment on your notes regarding the S&B TX102's!

The answer to this one is yes, transformers are one way to achieve balanced connections. The S&B TVC is just a transformer, albeit with a lot of different taps on it!

With regards to the TwinDAC and bass roll-off: I think you could be right on this one, as the TwinDAC was noticably lighter in the bass than my valve output stage with its lower output impedance. I think the +6db tap on the S&B' probably helped somewhat though?

Regards,

Jonathan

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by GC, Thursday, March 24, 2005, 00:25 (4689 days ago) @ GC

With regards to the TwinDAC and bass roll-off: I think you could be right
on this one, as the TwinDAC was noticably lighter in the bass than my
valve output stage with its lower output impedance. I think the +6db tap
on the S&B' probably helped somewhat though?

Thanks Jonathan,

I am the one, you should ask Bert for your commission :P

I was looking at the S&B site and I think the +6db helps level but with it comes a reduced BW, more significant at the bass end. With a typ 0.4v average voltage from the Twindac+ the input sensitivity of the power amp must be around 0.4v me thinks?

Cheers,
Brian

PS have you built the new amp yet, the one without o/p transformers?

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TVC Linestage

by GC, Thursday, March 24, 2005, 11:19 (4689 days ago) @ GC

Hi Brian,

Good to hear from you.

I was looking at the S&B site and I think the +6db helps level but with it
comes a reduced BW, more significant at the bass end. With a typ 0.4v
average voltage from the Twindac+ the input sensitivity of the power amp
must be around 0.4v me thinks?

Yes at least 0.4V, possibly more for some extra headroom. And you are right about the 6db tap, it would make matters worse due to the high TwinDAC ouput impedance.

Its the usual compromises and choices I guess. You could increase drive by adding a simple valve stage before the TVC, but this adds more active components to the main (Oris) output. Or you could live with the lower drive to the main output, but compensate with some EQ and higher gain in your bass amps.

PS have you built the new amp yet, the one without o/p transformers?

Yes, Transcendant SE OTL working for a month or so now and sounding very nice. I've not done any side by side comparisons yet with the 2A3, but I will do so soon!

Kind regards,

Jonathan

PS. What amp are you planning on building/buying for the Oris?

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by GC, Thursday, March 24, 2005, 21:39 (4688 days ago) @ GC

Hi Brian,

Since a few months I am listening to another two-stage 300B SET amplifier which is not as tight in the bass and a little bit less dynamic as the BP but in the mid and high frequencies its so smooth and clean sounding. The input sensitivity is also high enough to play my Oris system to extreme loud levels (+6dB on the Django not needed in combination with the TwinDAC+).

At this moment I prefer to listen to that amp more than to the 300B BP.

http://www.diyhifisupply.com/diyhs_ladyday.htm

Don't forget to tell them that I send you there though... :)

Ciao,

Bert

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by GC, Monday, March 28, 2005, 06:10 (4685 days ago) @ GC

Hi Bert,

Which LadyD version you listening to? Seem there is so much option for that amp...
Little off topic, which AER driver that optimize for singular?

Thanks

Hi Brian,

Since a few months I am listening to another two-stage 300B SET amplifier
which is not as tight in the bass and a little bit less dynamic as the BP
but in the mid and high frequencies its so smooth and clean sounding. The
input sensitivity is also high enough to play my Oris system to extreme
loud levels (+6dB on the Django not needed in combination with the
TwinDAC+).

At this moment I prefer to listen to that amp more than to the 300B BP.

http://www.diyhifisupply.com/diyhs_ladyday.htm

Don't forget to tell them that I send you there though... :)

Ciao,

Bert

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by GC, Monday, March 28, 2005, 16:29 (4685 days ago) @ GC

Hi,

Which LadyD version you listening to? Seem there is so much option for
that amp...

The ones with Black Gates, all Silver and Mesh Plate 300B's

Little off topic, which AER driver that optimize for singular?

I am still working on that driver, the AERmkI sounds best balanced but is a bit too shy in the bass. This combination needs a room where the bass normally sounds strong for a good balance (to my taste). Best drivers so far (regarding tonal balance) are the Fostex FE206E with EQ or the Fostex FE207E's.

Ciao,

Bert

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by GC, Wednesday, March 30, 2005, 00:10 (4683 days ago) @ GC

Hi,

Thanks Bert/Jonathan LadyD amp looks interesting but a variation of the "same" amp configuration. This is why I'm looking at a hybrid, something that mixes the highs from both technologies, tube and transistor.

What amp are you planning on building/buying for the Oris?

This amp looks interesting :heart:
http://www.vacuumstate.com/pow_announce_2005.htm

A bit expensive compared to others :^(

Transcendant SE OTL working for a month or so now and sounding very nice.

This amp gets very good reviews interesting what sound you can get from "cheap" valves...

Cheers,
Brian

PS Bert I have the photos but my lady has insisted I tidy the room and re-take them before sending... ;)

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