What's balanced input overload voltage for the BP-25?

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dubkarma

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I'm looking for a spec on the BP-25 that I can't find in any published literature or, so far, in any reviews.

What's the input overload figure—in Volts RMS—for the balanced inputs on the BP-25?

I suspect my DAC is overloading the balanced input on the preamp.

The DAC's factory setting is that a digital input of –18dBFS will produce an analogue output of +4 dBu.

However, most commercial CDs and other digital sources that I use typically go past "0" on the DAC's output meters...which may mean that the DAC is outputting as much as 22 dBu or 9.75 Vrms into the preamp. . .

CanadianMaestro

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Re: What's balanced input overload voltage for the BP-25?
« Reply #1 on: 21 Sep 2018, 11:51 pm »
I'm looking for a spec on the BP-25 that I can't find in any published literature or, so far, in any reviews.

What's the input overload figure—in Volts RMS—for the balanced inputs on the BP-25?



Found this: (https://www.stereophile.com/content/bryston-bp25-mc-preamplifier-specifications)

"S/N ratio: 100dB ref. 500mV unbalanced input, 20Hz-20kHz; 103dB ref. 11V balanced input, 20Hz-20kHz"

Read more at https://www.stereophile.com/content/bryston-bp25-mc-preamplifier-specifications#WisD2fYH2sRK4ipA.99

So apparently, the amp can take 11 V balanced in. Whether that's maximum or not....

cheers

dubkarma

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Re: What's balanced input overload voltage for the BP-25?
« Reply #2 on: 22 Sep 2018, 06:25 pm »
Canadianmaestro,

Many thanks for the information. However, the "Measurements" section of the same Stereophile article you cite, suggests that the "ref. 11V" that appears at the beginning of the article is a typographical error.

Compare your quotation:

"S/N ratio: 100dB ref. 500mV unbalanced input, 20Hz-20kHz; 103dB ref. 11V balanced input, 20Hz-20kHz"

with the statement in the Measurements section:

S/N measured 99dB (unweighted) over a bandwidth of 22Hz-22kHz, 82dB (unweighted, 10Hz-500kHz) and 102dB, A-weighted (all ref. 1V) for the line stage."

CanadianMaestro

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Re: What's balanced input overload voltage for the BP-25?
« Reply #3 on: 23 Sep 2018, 11:47 pm »
Canadianmaestro,

Many thanks for the information. However, the "Measurements" section of the same Stereophile article you cite, suggests that the "ref. 11V" that appears at the beginning of the article is a typographical error.

Compare your quotation:

"S/N ratio: 100dB ref. 500mV unbalanced input, 20Hz-20kHz; 103dB ref. 11V balanced input, 20Hz-20kHz"

with the statement in the Measurements section:

S/N measured 99dB (unweighted) over a bandwidth of 22Hz-22kHz, 82dB (unweighted, 10Hz-500kHz) and 102dB, A-weighted (all ref. 1V) for the line stage."

Ouch. I'm surprised
1. nobody edited/checked that article at S'phile.
2. nobody from Bryston has chimed in yet here.

That article's too old to bother e-mailing anyone at S'phile to check.

Good luck with the data hunt.

cheers

bapcha

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Re: What's balanced input overload voltage for the BP-25?
« Reply #4 on: 25 Sep 2018, 03:23 am »
Over voltage is not "overloading". Overloading is a combination of current and voltage. +/- 11V should not be an issue - but the preamp could drive your amp to clipping range (depending on the position of the volume control)

Input impedance is 50K Ohms(RCA) and 25K Ohms Balanced

http://bryston.com/PDF/Manuals/BP25_MANUAL.pdf

James Tanner

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Re: What's balanced input overload voltage for the BP-25?
« Reply #5 on: 25 Sep 2018, 05:54 pm »
The balanced input of the BP-25 is a unity gain buffer. Its output limit is 17 Volts RMS, 24V peak. Since I know of no DAC or other source that can output higher Voltage than that, it's unlikely the BP-25 will ever be able to be overloaded.

I hope the above is helpful, but please let me know if you have any other questions. Thanks for your support of Bryston!

Best regards,
Chris Russell
Bryston Ltd.