Turtlerock Forum

has anyone heard the chameleon labs 7602?

$699 US for a 1073 clone

aaaaaaand its made in china!

I wonder what attention to dedail re transformer quality pcb layout discreet components, etc

Well nothings sacred when it comes to recording gear and if these sound close to the real deal I wonder if Tom will drop the price of the real deal Neves by introducing some cost cutting procedures without compromising build quality?

Interesting that the powers supply provides +24 V, + 48V and -24V.
The original 1073 doesn't need or use -24V rails.
So what's up here?

why would a power supply use +24 and not -24 (if i'm reading what you said is right?)

also why is the ADL presonus pre running on 600v

is it hype or something that is really fantastic?

Hi Mark,

The voltage rails used in a circuit are a function of that circuit's topology i.e. whether the circuit is Class A, Class A-B etc etc. Original Neve mixers used Class A and so only required a single positive voltage rail. If a device pretending to be "Neve-like" uses a negative voltage rail of the same value as the positive rail, the inference is that that device is using op-amp circuitry that is not Class A i.e. not Neve-like at all.
You mention an ADL Presonus which I haven't looked at - this is presumably a box designed by ADL but put out by Presonus? Does it have valves?

Howard.

just to clarify what Howard has added.

the Power supply requirement in terms of voltage are dependant on the circuits topology. Class A doesn't necessarily need to run off a single supply rail but can run off bi-polar supplies ie + and - 34V as used in Avalon gear. However the early Neve modules did just run off one single rail of +24V.
So what is chamelion labs doing with the -24V voltage present of their PSUs if the Unit is a Neve "clone" that doesn't need it. One possibilty is nothing! I know of one other manufacturer who make Neve clones who provide a -ve rail on their PSUs. However in this case the PSU is a generic type that can also power other units that they make that do need the -ve rail. They just opted to manufacture one PSU unit that could be used right across their product range and in the Neve clone the -ve rail is simply not connected.

But who knows what Chamelion Labs is doing.
Maybe they have something up their sleeve.

What gets me is why can't manufacturers just design their own products, what ever happened to innovation?

thanks howard

yes the presonus/adl does have valves

also the chameleon labs does claim to be class a

Hi Mark,

It could be, as Rob points out that the device is running Class A off a dual-rail power supply - the easiest way of knowing is to look at a circuit diagram for that particular device. Or, that they have indeed used an all-purpose PSU and aren't actually using the negative rail in this particular circuit.
You have to assess what you think the bona-fides of this particular company are. Unfortunately, the be!@#$%^& "3 LEDs behind the valve" farce make one pretty suspicious about what goes on inside various boxes.
A valve requires a so-called HT rail i.e. "high tension". We would think of this today as high voltage - typically around 300V. Why this ADL Presonus is running such a high voltage escapes me for the moment. They may be using some esoteric biasing around the valve. Again, a look at the the circuit diagram would tell you what is going on.

Howard.

thanks all, you too rob, you must have answered whilst i was typing away.

here are the specs for the adl
never believe what you read until you investigate it!

+/-320 it seems
see http://www.presonus.com/adl600blk.html for the block diagram

specs below

Input Impedence


Microphone Selectable, 150/300/900/1500 Ohm
Balanced Line 2KOhm
Instrument 100KOhm
Maximum Input Level
Microphone (1500Ohm, +20dB Pad out) +5dBu
Microphone (1500Ohm, +20dB Pad in) +25dBu
Balanced Line +30dBu
Instrument +30dBu
Gain Range
Microphone (1500Ohm, +20dB Pad out) 18dB to 72dB
Balanced Line -12dB to 40dB
Instrument -5dB to 42dB
Noise Floor (all inputs, minimum gain) -95dBu (A-weighted)
Microphone Equivalent Input Noise (EIN) -125dBu (A-weighted)
Frequency Response 10Hz to 45KHz +/- 1dB
Maximum Output Level +23dBu (@ 0.5%THD+N)
Output Impedance 600 Ohm
Tube Complement (per channel) 1-12AT7A, 2-6922
General
Power (Factory Configured) 115 or 230 VAC / 100Watts
Dimensions 3.5" (H) X 17.0" (D) X 19.0" (W)
Weight 28 lb

At the input to the preamplifier is a custom designed input transformer. The transformer is fully encased in a Mu-metal enclosure yielding excellent noise characteristics and magnetic shielding. The transformer interfaces the balanced inputs from the Microphone or Line inputs to the tube preamp circuits. On the primary side of the transformer are circuits for +48V phantom power, microphone impedance, 20dB Pad, and Line input. All of these are switched by sealed relays for reliability. Also, the relays are located at the point where the switching is required. This minimizes the signal path length and helps to keep noise low.

The combination of a 12AT7A triode and a 6922 triode form the principle gain stage of the preamplifier. This stage gives the ADL600 its "open and airy" sound. This is primarily due to the circuit topology and the wide power supply rails applied to the this stage, +/-320VDC. A high endurance Grayhill rotary switch and 1% metal film resistors are used to set the gain of this stage in 5dB steps. Poly film pulse capacitors are used for inter-stage coupling to maintain the highest sonic clarity. The preamp stage drives the High Pass filter circuit and the Output trim. The High Pass filter can be bypassed or set to 40Hz, 80Hz, or 120Hz. Poly film capacitors are used for the filters also. The filters are 1st-order and provide 6dB/octave roll-off. The Output trim potentiometer feeds the input to the second 6922 triode. This is the output driver and drives the Mu-metal shielded output transformer. A DPDT relay allows for output phase reversal at the primary side of the output transformer.

A DPDT relay switches in the Instrument jack at the input to the 12AT7A triode bypassing the input transformer.

Power Supply

At the heart of all high quality microphone preamplifiers is the power supply and the one in the ADL600 is exceptional. It starts with a filtered A.C. input receptacle and ends with a power supply that far exceeds the load requirement. Fast switching diodes are used instead of standard recovery 60Hz diodes in the regulated high voltage supplies. The custom designed Mu-metal shielded toroid power transformer was designed to be over-rated by a factor of four. This ensures superior load regulation and minimizes the transformer flux leakage. All of these factors yield very low noise at all the supply outputs and very good load regulation.

Have any of you heard the Peavey VMP2 in action. Seems to be along the lines of the Presonus ADL600 but at half the price. Around 2002 they were going for $1000 US new I don't think they make em any more ,but one went on eBay for AU$850 last week.

Also remember that the rails that an external P/S supplies arn't the only ones that can be used, DC-DC converters, switchmode inverters etc. (And more realistically a 0-48v power supply can be used like a -24-0-24 and 48v power supplies are getting much cheaper as a lot of networking gear is starting to need them).

Hi Mark,

Thanks for all the information. If you click through to the Presonus site on the link you provided, you can start to disentangle some of what they are up to - I don't think there's anything funny going on. There are an array of voltage rails coming out of the power supply: +/-320V, +48V, +/-12V, +5V and +18V. Let's work through them and see what's what.

First off, the +48V is obviously used for phantom powering the mic inputs. The documentation they provide says that the +/-12v and the +5V are used in the meter controller circuits - fair enough. The block diagram shows 3 valves stages per channel - the first is the 12AT7A and the next 2 are 6922s. You'll notice that the 2 x 6922 stages are only using a +320V rail whereas the 12AT7A is using +/-320V. All valves are apparently using +18V filament rails.

These rails to the valve stages are a bit unusual. Filament voltages in the old days were typically 6.3V and the plate voltage around +300V. So, Presonus are supplying +320V to the plate and +18V to the filament. Just how the -320V is being applied would require examining a circuit diagram. I haven't got a valve applications guide handy, so I can't look up esoteric designs for triodes. Perhaps someone else will enlighten us on this. It may have something to do with improving the noise floor.

In any case, I don't think Presonus are up to anything too odd. You certainly wouldn't bother winding a transformer for -320v unless you had a good reason for doing so. Of course, you could always try emailing them and ask them to explain their rationale.

Two points to make: they say that the transformer is overrated for this application - it would want to be because the power supply is complicated compared to a run of the mill box. US designs seem to most often assume that 240V = 210V and that 60Hz = 50Hz, neither of which assumptions are valid or helpful. The result is generally that - over a very long time - the transformer works too hard and one day fails.

The other point is that, according to the Presonus documentation, the signal is actually routed through all of the valve stages - something that can't automatically be taken for granted in this cynical age. This is something that should be able to be heard, so there you go all you audio buffs - audition a Presonus and your ears will tell you the difference.

Howard.

The -320V rail to the 12AT7A stage may be part of the switchable gain control to this stage.

thanks howard

you make it very easy to understand

from what i've read and obviously from the ADL badging its anthony demarios baby, and presonus are in charge of manufacturing/marketing/distro.

not sure if its a smart move from anthony, he was a market leader in his feild/catagory in the early 90s but never really capitalised on his position
also his products should have sounded a little better for all the hype

i think rick still owns his la2a knock off
which sounds nothing like an la2a
apparently you have to mod them (rick will tell you what to do)
to make them sound better, although i have never used one once modded

specs seem for the ald600 seem pretty darn good although you would have to have rocks in your head to part with that sort of money and be left the resell value of a presonus!

kinda like those ssangyongs with the merc engines,
you get a bit of mercedes but you've still got a ssangyong!
but with the presonus adl you are paying a merc price

Why, how much is it? I'm not really up on Presonus.. they had some 8 channel thing didn't they - did that sell well?

The price is US$1999

Seems like a lot... how much is/was ADL-badged product?

ADL CL 1000 Comp Limiter $1500 US
ADL 1500 Stereo Comp Limiter $2995 US
ADL 1600, the Opto stereo comp $2399 US

heres where i read that it was 600v

is this correct or incorrect based on the blopck diagram
ie can +/-320v be refered to as (600v peak to peak)


The Presonus ADL600 utilizes extremely high voltage power rails (600V peak to peak) delivering 75dB of gain, over 30dB of headroom, and extremely wide frequency range of 5Hz to 80kHz within 0.5dB. The combination of Anthony DeMaria's preamplifier design and PreSonus' state-of-the-art manufacturing process achieves a new standard in hand-made, high-voltage tube preamplifiers

Hmmm, Mark you seemed to think that ADL didn't have sound quality that lived up to the prices being charged...

Regarding the 600V claim: they are talking in shorthand. Yes, they are meaning that the voltage swing from +320V to -320V is 600V - obviously it is a bit more but the usable voltage available for a sinewave moving from full positive excursion to full negative excursion may be around 600V. I guess that's where they get the model number from.

anothony has never actually made his own stuff , he subs it out and gets it put together out of his shop ( smart way of not actually owning a factory)
gml does the same. ( manley factory built)

if presonus made him an offer he could not understand i am sure he would have taken it.

anothony makes his bread as a day to day tube tech.
i am sure he knows excactly what he is doing

Ah-ha. That would explain why his product range has always seemed relatively small.