Jim Gamble EX56 schematics
- Thread starter Balijon
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jensenmann
Well-known member
Ask at Desch Audio, they offer that console for sale. Maybe they have schematics, too.
IIRC Gamble turned into Crest, so a request at Crest headquarters may be another option.
IIRC Gamble turned into Crest, so a request at Crest headquarters may be another option.
Balijon
Well-known member
THX Jens,
I tried to contact Desch Audio several times, by email and phone, but nothing. Are they still in business?
grT
I tried to contact Desch Audio several times, by email and phone, but nothing. Are they still in business?
grT
Balijon
Well-known member
dcollins said:
With the risk of starting a flaming war again on digital conversion...:
Jim states that at lower-level signals the relative distortion of the A/D converters increases. This is due to the fact that there are relative less bits 'active' to describe the signal-waveform. On this point I agree with Jim Gamble, the effect is of course more dominant on a 16-bit system than on a 24-bit system.
I don't understand his 'phase-shift above 2k4' remark. But of course a DC-coupled system-chain introduces less phase-shift than a chain with decoupler-capacitors.
Jim used in the EX56 only MKT-capacitors in the audio chain and the complete channel stages are DC-coupled with servo's.
Theo
Andy Peters
Well-known member
dcollins said:
My favorite paragraph from that article says, "The firmware for the Altera chip (100 programmable gates on one chip, one on each DCX module), took eighteen months to perfect, including the State Machine."
If it took me 18 months to perfect a tiny CPLD, I wouldn't have a job. I think it would take me about 18 hours to design, code, verify, implement and document that design.
One suspects that since Gamble's an analog guy, he probably did all sorts of asynchronous hooey in his code, which probably changed from implementation run to implementation run, and it glitched, and the other bad things that happen with that sort of design paradigm. He probably didn't simulate the design, which was probably done in Altera's bad old schematic-based design environment.
Anyway, back to my 10,000 flip-flop FPGA design, with two asynchronous clock domains, high-speed data deserializers, and for added aggravation, an embedded micro.
-a
Balijon said:
The LSB resolution (quantization distortion) is a popular complaint about digital conversion, but ignores the dithering affect of internal noise floors greater than the LSB resolution, oversampling processing, etc. The quantization distortion was real back with early low bit rate (12 bit and 14 bit) systems, but the modern stuff works well, as our ears already advise us.
for another perspective on digital http://people.xiph.org/~xiphmont/demo/neil-young.html here's a guy saying 24/192 is unnecessary.
Jim is not a digital expert, and his comments are arguably self serving (or innocent misunderstanding). His consoles are an interesting experiment in digitally controlled analog using DPOT technology (AFAIK), to avoid that evil digital domain, but his choices for non-digital media are severely limited, making this grand experiment moot as far as practical use, beyond mixing for live sound. While even live sound is becoming infected with digital processing for loudspeaker crossovers, and delay compensation, etc. (class D power amps are arguably still analog).
JR
Balijon
Well-known member
Thanks for sharing this link John.
Most interesting view on 'ism's' and reality context.
I am interested in how Jim applied the D/A's as DPOT's in the EQ sections. I have seen solutions with using multiplying DAC's for volume pots that are more clean than VCA's. (like the Hoef-Automix HF-16)
In the meantime I am still hunting for the 'old-all-analog' EX56 schematics.
Theo
Most interesting view on 'ism's' and reality context.
I am interested in how Jim applied the D/A's as DPOT's in the EQ sections. I have seen solutions with using multiplying DAC's for volume pots that are more clean than VCA's. (like the Hoef-Automix HF-16)
In the meantime I am still hunting for the 'old-all-analog' EX56 schematics.
Theo
Attachments
Balijon said:
I don't know about all of his consoles, the one I saw some circuits from used conventional digital pots, so these look like regular analog pots to the analog circuits they are in, but can be controlled by a digital word.
There can be obvious issues with DPOTs in general from zipper noise, and/or if pot settings jump too fast or take large steps, and I have even seen reports of subtle glitch issues at major digital code transitions. Some DPOT applications synchronize pot changes with audio path zero crossings (like the dig controlled mic preamps) to manage both zipper noise and glitch energy.
I have seen a few schematics in confidence but am not free to share anything... I don't think I even saved what I saw. My recollection is it looked very very expensive to do that way.
JR
PS If you are seriously considering buying one, it seems a fair question to ask Gamble if you could then get access to schematics. Surely a console of that complexity will require repairs and support.
Balijon
Well-known member
JohnRoberts said:
There are two main generations of Jim Gamble consoles: The 80's 'all-analog' EX-series and the later (90's) 'digital-controlled-analog' DCX-series.
The article you linked with the DPOT's is mainly about the later DCX-series.
The EX-series was the US competition to the UK Midas PR04/PR40-series from the same timeframe. They were mainly used by large touring-companies and major bands that could afford them..
I expect the EX56 to be a very conventional (simple) analog design, he used rare opamps from Analog-Systems (like the MA-362 & MA-374) that run +/-24V.
I send Jim an email with my request, I expect he will help out or redirect me.
grT
dcollins
Active member
- Joined
- Mar 27, 2006
- Messages
- 37
Balijon said:
I'm afraid that a digital system using dither doesn't behave any differently wrt low-level signals that an analog one does. Although it's a popular misunderstanding.
I wonder if his 2k4 claim was in ye olden days before oversampling? In those systems the HF phase shift was enormous, but there is a question of how audible it really was. If you listen to old CD's like Dire Straits, the group-delay is positively off the charts, but the sound is good......
DC
audiomixer
Well-known member
I did one show on that board - back in the days....
it was definitivly a console to remember. I did really like the sound of it. was thru a BSS Omindrive into a large clair bros pa, usually not the best sounding equipment, but hey, this combo rocked!
- michael
it was definitivly a console to remember. I did really like the sound of it. was thru a BSS Omindrive into a large clair bros pa, usually not the best sounding equipment, but hey, this combo rocked!
- michael
Chrisfromthepast
Well-known member
- Joined
- Mar 5, 2018
- Messages
- 268
Necrobumping this thread.
I heard a gamble eh56 last weekend as the systems tech, and I loved what I heard.
I was curious about the topology. Does anyone around here have insight into the preamp and bussing sections?
I heard a gamble eh56 last weekend as the systems tech, and I loved what I heard.
I was curious about the topology. Does anyone around here have insight into the preamp and bussing sections?
