The Hiss of Old Preamps

[ManFromGlass]

I have 2 old Ward Beck mic pres that hiss. Not enough to detract from what they add to the sounds going through them but you can hear it. A tech told me he can add a shield around the internal power supplies, clean up some wiring and that should help.
Considering how many wonderful records that have been made with similar or noisier gear I am thinking why bother.
That being said there may come a day when I record a high number of tracks through the unit and I am thinking the tech’s suggestion is a good one. I doubt I have ever used more than 10 tracks in a song that have been recorded through the units as I mostly work in the box. But perhaps it would be a good thing to be prepared. I’m asking for any thoughts from those of you who record a lot of live tracks - thanks.

[James Perrett]

If hiss is the problem rather than hum then I'm not sure that shielding and moving wires will help. I can't easily find a circuit diagram of any of their modules but I would guess that the only way to reduce hiss would be to modify the circuit to use lower noise components which may also change the sound that you like.

Does the level of hiss change when you adjust the gain? If so, a Cloudlifter or similar would allow you to use lower gain on the Ward Beck preamp.

[Wonks]

The hiss may have been hidden in the past with the lower dynamic range of tape snd vinyl, but with digital, exposed quiet tracks will probably reveal the hiss.

[Philbo King]

If hiss is the problem rather than hum then I'm not sure that shielding and moving wires will help. I can't easily find a circuit diagram of any of their modules but I would guess that the only way to reduce hiss would be to modify the circuit to use lower noise components which may also change the sound that you like.

Does the level of hiss change when you adjust the gain? If so, a Cloudlifter or similar would allow you to use lower gain on the Ward Beck preamp.

Exactly so. Hiss is generally due to thermal noise, diode barrier noise (the sum of individual charge carriers crossing PN junctions), and a few other noise phenomena such as 1/f noise and aging capacitors and possibly cold solder joints.

So... the fix? Start by measuring hiss, reflowing every solder joint, then remeasuring. If there's no change in hiss level, or it is still there but decreased, replace all the capacitors and measure again. If it still is at an unacceptable level, it's time to consider some design changes as James Perret suggested.

You might consider using spectral denoising as a bandaid fix. Reaper has this in the ReaFIR plugin. There is also one in the Izotope plugin.

[sonics]

Don't forget that hiss removal tools are so much more sophisticated than they used to be. A small amount of hiss is really easy to remove from most sources before further processing.

[Wonks]

Is the hiss louder than that of summer lawns?

[ManFromGlass]

As Joni might say now - Tell you when the new hearing aids show up

[ManFromGlass]

Does the level of hiss change when you adjust the gain? If so, a Cloudlifter or similar would allow you to use lower gain on the Ward Beck preamp.

I like using them with an active Royer and have a Cloudlifter but haven’t figured how to get phantom to the Royer.

[Wonks]

You need a booster that passes phantom. The Triton Fethead Phantom does.

https://www.gear4music.com/Recording-an ... hones/3R9K

[Hugh Robjohns]

A tech told me he can add a shield around the internal power supplies, clean up some wiring and that should help.

I'd be surprised if that would help reduce Hiss. Shielding can reduce interference from external (or internal) sources, and in some cases it could reduce magnetic hum from power transformers etc

But hiss is normally due to the active components and thermal noise from passive components, especially in the higher impedance parts of the circuitry. All the Ward Beck (Canadian broadcast desk) modules from the 1980s I've seen have used op-amps. I dont know which, but in the 80s many were relatively noisy. I've no idea what technology is used in your modules or whether it could be upgraded without losing the character you like, but it might be worth investigating.

Considering how many wonderful records that have been made with similar or noisier gear I am thinking why bother.

That would be my view too. If you like the sound, hiss is a part of it... although it would be worth checking your gain structuring is optimised.

[James Perrett]

All the Ward Beck (Canadian broadcast desk) modules from the 1980s I've seen have used op-amps. I dont know which, but in the 80s many were relatively noisy. I've no idea what technology is used in your modules or whether it could be upgraded without losing the character you like, but it might be worth investigating.

The circuit diagrams that I found showed extensive use of NE5534s although I didn't find any showing input stages. I think Neve started using those (when they were still known as the TDA1034) in their mic preamps in the late 70s. However Neve used them with transformers which would help optimise the noise performance.

[Tim Gillett]

Don't forget that hiss removal tools are so much more sophisticated than they used to be. A small amount of hiss is really easy to remove from most sources before further processing.

In a sense, yes. Someone once made the definitive statement on hiss removal tools IMO:

"They work best when they're least needed."

[ef37a]

All the Ward Beck (Canadian broadcast desk) modules from the 1980s I've seen have used op-amps. I dont know which, but in the 80s many were relatively noisy. I've no idea what technology is used in your modules or whether it could be upgraded without losing the character you like, but it might be worth investigating.

The circuit diagrams that I found showed extensive use of NE5534s although I didn't find any showing input stages. I think Neve started using those (when they were still known as the TDA1034) in their mic preamps in the late 70s. However Neve used them with transformers which would help optimise the noise performance.

The NE5534 is a very old op amp but one whose noise performance has only recently been bettered but even the 5534 on its own is not suitable for direct connection to a microphone since its low noise depends on an optimum source resistance and 200 Ohms'ish is too low. The problem was largely fixed early on by using two or more bipolar transistors affront the op amp. I would guess that desk did not use such a configuration.

Some 1:4 mic transformers could help as they would give about 10dB of essentially noise free gain. That however depends greatly on the input resistance of the mic pre amps.

And no, as most have said, dicking about in the PSU is not going to fix hiss. That is caused by resistors and to a degree, active devices.

Dave.

[Hugh Robjohns]

I think Neve started using those (when they were still known as the TDA1034) in their mic preamps in the late 70s. However Neve used them with transformers which would help optimise the noise performance.

Indeed!

The famous Focusrite ISA110 (and subsequent ISA and Red) mic preamp design is nothing more than a Lundahl LL1538 1:5 ratio mic transformer feeding a single NE5534 (with a complicated input attenuator /gain switching circuit).

The transformer provides roughly 20dB of fixed gain and creates an optimal impedance for the bipolar op-amp (around 5k Ohms), while the op-amp itself provides up to a further 40dB of gain in switched steps (usually 6dB increments) for 60dB overall.

In some variants a second NE5534 provides a further 20dB of fully variable trim gain, making 80dB overall.

EIN (60dB gain, 150 Ohm source, no weighting, 20Hz -22kHz bandwidth) is -127dB... which is about -130dB A-weighted and about as good as it gets.

[ef37a]

It is interesting to read the distortion specc' for that transformer? At 50Hz and a primary input of 0dBu it is just 0.2% and will be a lot less than that at mid band frequencies.

That is a hell of a level out of any dynamic mic and pretty potent for most capacitors. This causes one to have 'reservations' shall we say about all those claims for "wonderful transformer warmf"?

Of course, not all transformers are a good as Llundys but even so??

Dave.

[Hugh Robjohns]

It is interesting to read the distortion specc' for that transformer? At 50Hz and a primary input of 0dBu it is just 0.2% and will be a lot less than that at mid band frequencies.

It is a pretty special transformer. The XL version is even better.... and they cost a lot as a result!

That is a hell of a level out of any dynamic mic and pretty potent for most capacitors. This causes one to have 'reservations' shall we say about all those claims for "wonderful transformer warmf"?

Those warmth claims (ie, added 3rd order distortion) usually relate to output transformers don't they? Input transformer characteristics are usually more related to transient softening in my experience.

But yes, you'd need a beefy source and a sensitive mic to reach 0dBu. A capacitor mic with a sensitivity of 25mV/Pa would generate 0dB with a source at about 125dB SPL. Easily achieved with a capacitor mic close on a drum, for example, or even a particularly energetic singist! With an SM58 you'd need more than 150dB SPL to reach 0dBu.

Of course, not all transformers are a good as Llundys but even so??

Many Jensens, Sowters and Carnhills are comparable... but all are frighteningly expensive. The LF distortion performance of cheaper transformers is substantially worse... although some may well perceive that as musically better, of course! ;-D

[ef37a]

"Those warmth claims (ie, added 3rd order distortion) usually relate to output transformers don't they? Input transformer characteristics are usually more related to transient softening in my experience. "

Possibly Hugh but it seems to me that ANYTHING with a transformer in it HAS be described as having those characteristics!

Dave.

[ManFromGlass]

Quick update - I’ve ordered the Triton in-line pre that passes phantom. I’ll let you know how it works out.

As for transformers - I have the WBs mounted in a box. I had the tech add a Hi Z input so I could run a guitar or bass through the WBs. I think I ended up choosing the Sowter over the Jensen but I would have to check. Either way it’s a lovely little swiss army knife in a box now.

[ef37a]

"EIN (60dB gain, 150 Ohm source, no weighting, 20Hz -22kHz bandwidth) is -127dB... which is about -130dB A-weighted and about as good as it gets."

That specification makes me think...the op amp, providing just 40dB of gain will have a vanishingly low level of distortion and of course the transformer perhaps even less.
Perhaps what people are really hearing is the true sound of the microphones through a very transparent amplifier? The "larger than life" effect?

Dave.

[ManFromGlass]

The Triton Fethead Phantoms rock!
Almost too much gain for the Ward Becks with the active ribbon.
No more turning the in and outputs up high so virtually no hiss. I just hear a tiny bit of the hum of ancient electronics.

The down side? Well, in the music store I made the mistake of comparing the Rode headphones on display against the expensive ones. I managed to drag myself out of there without making a purchase but I think they only make sense now . . . . . . . .

[ajay_m]

I may be a philistine here but a noise gate set with the threshold just at the point where it's taking the noise out and with a fairly slow release proved to work well on one channel of my mixer where the input device (Roland sonic cell) had a noticeable noise floor and doesn't seem to add any audible effects.

[ef37a]

I may be a philistine here but a noise gate set with the threshold just at the point where it's taking the noise out and with a fairly slow release proved to work well on one channel of my mixer where the input device (Roland sonic cell) had a noticeable noise floor and doesn't seem to add any audible effects.

Now, I bought a Behringer BCA2000 on the strength of the 2005 SoS review and for a time it was a remarkable bit of kit for the price, in fact nothing quite like it has been made since AFAIK. The device proved to have poor drivers (never got better) and terrible reliability. The mic1/instr channel however had a really good noise gate on it that worked very well with sons Strat copy. More cleaning up buzz than hiss.

Dave.