AML EZ1073Pre noise figures?

[GalenH]

Hello,
I am trying to find out the Equivalent Input Noise (EIN) for the AML EZ1073pre 500 series preamp. Of course the build quality would influence, but has anyone measured the ein of these preamps with a 150 ohm resistor? The noise figures don't seem to be available anywhere online. The old 1073s supposedly said they had -125 db or better.

Thanks for the help!

 

[ruffrecords]

-125dBu EIN is about right with a 150 ohm source for most Neve mic pres but it will depend on the gain at which you measure it.

Cheers

Ian

 

[GalenH]

-125dBu EIN is about right with a 150 ohm source for most Neve mic pres but it will depend on the gain at which you measure it.

Cheers

Ian

Thanks Ian, I assume that it's likely similar for the amls, of course there would be variables, but they closer they are to the originals, the closer we could imagine they are to that figure. I wish AML would publish specs though!

 

[GalenH]

-125dBu EIN is about right with a 150 ohm source for most Neve mic pres but it will depend on the gain at which you measure it.

Cheers

Ian

One more question Ian, have you heard of people replacing the BC184 transistors with toshiba 2sc3329BL’s?

some say that gets lower noise with the 1073 style preamps. I know this is a bit of a beginner question, but do you know how this would affect the sound other than reducing noise?

 

[ruffrecords]

One more question Ian, have you heard of people replacing the BC184 transistors with toshiba 2sc3329BL’s?

I have not heard of that.

some say that gets lower noise with the 1073 style preamps. I know this is a bit of a beginner question, but do you know how this would affect the sound other than reducing noise?

It is possible but not likely to make a significant difference. -125dBu is only 6dB worse that a theoretically perfect amplifier so the possible noise improvement in most cases is insignificant. There is plenty of negative feedback in Neve designs which significantly reduces the effect of component variants so changing one transistor will make only minute differences to the sound.

Edit: In the old days transistor manufacturers used to publish noise figure curves but you don't see that anymore. However the 2SC3329BL does publish this information and it looks at least as good as the BC 184C. Whether a straight substitution would achieve any measurable improvement is hard to say.

Cheers

Ian

 

[GalenH]

I have not heard of that.

It is possible but not likely to make a significant difference. -125dBu is only 6dB worse that a theoretically perfect amplifier so the possible noise improvement in most cases is insignificant. There is plenty of negative feedback in Neve designs which significantly reduces the effect of component variants so changing one transistor will make only minute differences to the sound.

Edit: In the old days transistor manufacturers used to publish noise figure curves but you don't see that anymore. However the 2SC3329BL does publish this information and it looks at least as good as the BC 184C. Whether a straight substitution would achieve any measurable improvement is hard to say.

Cheers

Ian

Thank you for these thoughts Ian, I think I will leave the AMLs as is, and when i need super high gain low noise preamps i have other options. I appreciate your input

 

[Whoops]

You can reduce a bit the noise in Neve preamps by using transistor with an higher HFE for the first input transistors, it is said that over 600 hfe is higher hfe in this scenario.
When BC184C were available DIY people choose the ones with hfe higher than 600 for the first input transistors.
Nowdays with BC184C being rare the MPSA18 is a great replacement and actually most of them are close or higher than 600 hfe. Be aware the pinout on the MPSA18 is the opposite of the BC184

Read more here:

http://www.jlmaudio.com/forum/viewtopic.php?p=3251

 

[Matt Syson]

Noise figures used to be a hot topic back in the day and quite a lot depends on the gain used as Ian commented, the 'correct' termination and measuring the noise in a consistent way. Most mic amps give the 'best' figures at highest gain. I was used to seeing around -128.5dB EIN with 150 Ohm termination measured 20 - 20KHz with RMS meter chracteristics. Using weighting curves and peak/quasi peak rectification could reveal other issues like LF noises or even power supply related noise with some products which although not quite cheating would allow cross referencing. The definition of 'low noise' for transistors also changes with time as low noise in the 1970's can be a lot worse than low noise in 2000. Noise also depends on the impedances 'seen' by the transistor which transformer ratios attempts to match to yield the best overall. A few designs could hit -129dBu and to enable all examples to officially 'be in spec was often noted as -128.5 dbu. Audix used BC413 and 415 transistors although I expect they wee obsolete years ago. Choices of components used originally sometimes depended on factors other than 'sonics' as equipment reviewers would measure the various aspects. BC109C was often the 'go to' low noise input transistor as it's high Hfe specimens also coincided with than optimal noise area where current noise crossed with voltage noise if I remember correctly.

 

[ruffrecords]

I just discovered Silicon Ark. They do lots of old transistors, capacitors and even some bulbs that might be good for restoring vintage gear.

And the sell tested NOS BC184C transistors:

Electronic Components from Silicon Ark Electronics

and their prices are not crazy high either. I just purchased a bunch of BC184C from the. I will test them on my Peak Atlas when I get them.

Cheers

Ian

 

[Whoops]

either. I just purchased a bunch of BC184C from the. I will test them on my Peak Atlas when I get them.

Please do Ian,
would love to know how they test like

But I've been quite happy in the last 10 years of replacing BC184C with the MPSA18.
The MPSA18 works great and it's quite consistent

 

[ruffrecords]

Please do Ian,
would love to know how they test like

But I've been quite happy in the last 10 years of replacing BC184C with the MPSA18.
The MPSA18 works great and it's quite consistent

The MPSA18 looks like an excellent substitute. I am not one for insisting vintage parts should be used in vintage gear but some folks prefer to. I will post test results once I receive them.

Cheers

Ian

 

[Whoops]

Yes, for sure
It’s great to know

 

[Dan Kennedy]

I've been using MPS-A18's right from the start with the NV series preamps, about 25 years ago. Looked at the BC184, compared it to the then readily available 18 and said ok then. EIN is the same as 1073's. The noise of the circuit is only partially based on the transistors, the resistor values used basically limit the lower limit of the circuit. Wouldn't agonize too much.