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Passive Pre amp to DAC

Docmoggy

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Hello,

Being an engineer - of the mechanical variety - it is a pleasure to finally see lots and lots of data carried out by highly qualified and experience professionals. I must say, I did do a lot of FFT and Laplace Transforms many moons ago, but it was great to see Amir take time to tutor us. Brilliant. I did check out the paper on jitter and it all became clear!

However, my question is about passive preamps. Recently I read an article, by one of those reviewers, that sang like a song bird about coupling a Townsend Allegri Reference pre amp to a MyTek Brooklyn Bridge.

Having just read the review of the Topping pre amp it seems that, at $11,000 for the Townsend, a British brand, is the Topping any less capable in performance at a fraction of the price?

Thanks for reading.
 

Tks

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Tough to say without having the Townsend officially measured. I'd place my bets at Topping doing far better performance wise with off-hand experience how lots of these high priced devices fail once put under the pain of measurements. It's very rare to find a device in the 10's of thousands with respect to amps or dacs that actually bring the performance one would expect.

Especially when you consider the Topping it's up against.
 

AnalogSteph

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I am not sure why one would build a passive preamp based on an autotransformer, but these folks have clearly done it and made it electronically controlled using reed relays:
http://www.townshendaudio.com/allegri-reference-preamplifier/
Specs look good (they better do for the price) but I suspect output impedance can be dubiously high depending on volume setting (I don't see that kind of input impedance happening without a lot of turns, so total winding resistance alone may be well in the kOhms), and the XLRs aren't properly balanced either (at that kind of price an extra pair of input transformers wouldn't have ruined them).

I guess it's cool that something like that even exists, but don't ask me what kind of problem it actually solves. OK, using an autotransformer would tackle the issue of volume pot noise being highest at -6 dB, but in return you get all kinds of other problems. It really smells of "design by agenda".

If you have a DAC-Pre like the aforementioned Mytek, you probably need an extra preamp like a hole in the head anyway. A good fixed line-level attenuator would be worth considering if maximum DAC output and power amp input sensitivity are way different, after all even 120 dB of dynamic range has its limits. But then we're generally talking sub-$100, not the price of a small car.
 
OP
D

Docmoggy

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Mar 13, 2021
Messages
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I am not sure why one would build a passive preamp based on an autotransformer, but these folks have clearly done it and made it electronically controlled using reed relays:
http://www.townshendaudio.com/allegri-reference-preamplifier/
Specs look good (they better do for the price) but I suspect output impedance can be dubiously high depending on volume setting (I don't see that kind of input impedance happening without a lot of turns, so total winding resistance alone may be well in the kOhms), and the XLRs aren't properly balanced either (at that kind of price an extra pair of input transformers wouldn't have ruined them).

I guess it's cool that something like that even exists, but don't ask me what kind of problem it actually solves. OK, using an autotransformer would tackle the issue of volume pot noise being highest at -6 dB, but in return you get all kinds of other problems. It really smells of "design by agenda".

If you have a DAC-Pre like the aforementioned Mytek, you probably need an extra preamp like a hole in the head anyway. A good fixed line-level attenuator would be worth considering if maximum DAC output and power amp input sensitivity are way different, after all even 120 dB of dynamic range has its limits. But then we're generally talking sub-$100, not the price of a small car.
Hello, thank you for your analysis. I am in agreement with it. The more I make the effort to study the subject matter behind audio reproduction the more I realize the cost is immaterial- it is the result that matters! The trend seems to be simple well constructed sensibly designed products that supply measurements backing their claim and subsequently verified by independent sources will be prudent purchases. This has radicalized my traditional audiophile tendencies honed over the years by complete ignorance, it would seem. That is now remedied and out went the fancy stuff in went the real! Sounded much better at less than 80% of the original cost. I’m sticking with my Wilson Audio speakers and I hope Amir doesn’t test them! I’d rather not know. Thank you very much for your time.
 
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