Mezmerize DCB1 Building Thread - Page 11 - diyAudio
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Old 25th December 2010, 05:21 PM   #101
Salas is online now Salas  Greece
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Quote:
Originally Posted by bkdog View Post
but is there a complete circuit of the Mez somewhere with part designations which relate to the PCB?
The boards have no designations like R1, R2 etc but they have the actual component values and semiconductor types printed. So its tell tale what goes where.
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Old 30th December 2010, 07:27 PM   #102
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hey all, I'm about to put in my order for some mez parts but have 1 question. I intend to hotrod mine a little bit, so I'm going to get some 6.2R wirewound resistors (for a little over 300ma current) but will the 120 diodes be ok? I was going to order some mur860 or stealths but I would have to bend the pins to make them fit the mez board since they are to-220 trying to fit into a do-41. Should I do this? or can I safely hotrod the mez with the 120s? does the "ultrafast" recovery time make that much of a dif?
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Old 30th December 2010, 07:37 PM   #103
Salas is online now Salas  Greece
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Those are 1A diodes the 120. They will take it if the ambient is low. I remember builds running like that from members shown around, but 200mA is safer. I would say keep it to 8R2 though, its enough.
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Old 30th December 2010, 07:40 PM   #104
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I use To-220 diodes in the same holes as well, it's a little more dangerous if the cathodes wack each other, but electricians tape over I think one of them cure's this.
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Old 30th December 2010, 08:06 PM   #105
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ok ordering parts now. I'm gunna use prp resistors in signal for now until I have some money to try the texas components resistors. pics coming soon!

Last edited by particleman14; 30th December 2010 at 08:16 PM.
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Old 4th January 2011, 09:33 PM   #106
ramallo is offline ramallo  Europe
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I'm listening the DCB1 Mezmerize, great sound, a clean and very open stereo image. I have a bit of hum when my ear are close to a speaker (My speakers have 96dB 1W/1m), but is a very provisional installation without pot (Just a jumper) and fair wires, I'll try to find the hum when I have really finished the DCB1.

In other hand, I'm thinking in hot rod a bit my unit, simply by adding up to two 68 Ohm resistors more in parallel with the existing ones (Now two of 68 Ohm 1W). what is the good mA value for the DCB1? what is the safe value for the stock diodes (MUR120)?.

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Old 4th January 2011, 09:42 PM   #107
Salas is online now Salas  Greece
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The diodes you got have 1A nominal spec. It depends on your sinks where you can go. Can I see a picture to estimate? Congratulations by the way. Tiny hum you will solve. There is no issue when you will ground well and keep the Tx away from the inputs. Even on FFT. We also know from members feedback in systems with horns etc.
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Old 4th January 2011, 10:26 PM   #108
ramallo is offline ramallo  Europe
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Hi Salas,

This is a photo of the DCB1, The chassis is all aluminum 40mm high, 330mm wide, the covers and the back panel are 3mm thick, the front and sides 10mm. The transformer is a 2x12V 50VA

Click the image to open in full size.

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Old 4th January 2011, 11:54 PM   #109
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The way you use the chassis as a sink you can go 4x68R no problem. That will be about 120mA, but check the drop across the resistors for trimming current more equally between polarities. It usually differs. You can even go near 200mA and it will sink OK. ICCS=VRset/Rset.
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Old 14th January 2011, 02:47 AM   #110
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Default Mezmerize build

Hi:

Sorry if this is in the wrong place for this post, I can't find a thread dedicated to building the Mesmerize. I am getting ready to build one, but I have an itch to use something other than a rotary switch to activate the input relays. I have always liked momentary-contact pushbuttons a la Quad 34/44 preamps. So, without really knowing what I'm doing I came up with the following circuit. I would appreciate some feed-back, like for example "that won't work" or "that might work" or even "there's a much better way to do that".

First let me apologize for the graphic, I just downloaded the geda schematic editor and this is my first time using it.

The circuit uses a 40174 hex D-type flip-flop. Each switch is connected on one end to a voltage source. (The 4000-series chips can use up to +15V supplies so I am thinking I will just steal some +12V from the regulator on the pre-amp board; alternatively I could add a 5-volt regulator.) When, for example, SW1 is closed it applies a high voltage to input D1, and also to the CLOCK input (through a diode to insulate it from the other inputs). The low->high transition on the CLOCK line causes output Q1 to go high, which drives transistor Q1 through a base resistor. The transistor switches on, and completes the circuit from input 1 on CONN1 (coming from relay coil) to ground through pin7 on CONN1. (Yeah, I know I have an extra ground symbol there.) When another switch is closed, output Q1 will go low and the other output will go high.

One concern I have i that, at least on paper, the chip needs a few nanoseconds of set-up time between a change on the inputs and the transition on the clock line. I figure a small RC circuit on the clock line could introduce a small delay, with maybe a series small-signal diode that wouldn't conduct until the voltage reached Vf. I think it would just need a few pF and a small resistor for the delay (10 or 20 nS should do it).

Does this look like it would work? If so, I also want to include indicator LED's; should they be in series with the relay coils or parallel? I think this could easily be built on a piece of veroboard, perhaps with the switches and LED's on the back to mount to a front panel.

Any and all feedback appreciated.
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Last edited by nezbleu; 14th January 2011 at 02:53 AM. Reason: replace attachment
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