Mezmerize B1 Buffer Preamp

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#61
Judging by the feedback we get on the B1 and the DCB1, then the B1 is the much simpler to not make a codswallop of.

Both should be very simple, except for the regulated supplies involving more components to place and solder.

Both will suit SS and/or Valve stages.

If want very simple go for B1.
 
#62
Hi guys,

Im planning on building a Mesmerize B1 Buffer preamp and an Aleph J2, my current Marrantz PM7200 amp has left me in the cold 🙁. I'v read both building threads (not all reply's, but a lot) and got a whole lot of good information. I'm still having some questions, maybe someone on the form can help me answer them.

1. Any advice on Rotary switches with 2 poles 6 positions (buy-able @mouser)?
2. which transformer would you advice, i can get a torroid with 300va 2x18 output or a 500va 2x18 output?
3. the volume pot, i dont have a clue which would be suitable, could you give me any advice on this?
4. the omtron G6H-2-100-DC12 isn't available any more, is the NEC EA2-12NU a good substitute?

i'm not a DIYaudio veteran so please bear with me.
 
#65
A standard Mezmerise draws ~20mA for the Buffer plus the remaining CCS current draw and has to hold closed two relays fed from the negative side of the PSU.
It could manage with a 20VA 15+15Vac transformer.
100VA as Salas has mentioned is massive. 300VA was an aberration.
 
#66
LSK 389

Hello everybody. I'm trying to confirm if it is possible / correct to use the LSK389 with the Mezmerize B1. In the original B1 thread it is mentioned that it is a "waste" for that design as perfect matching is not needed. In the DC coupled B1 I understand it is instead necessary for the 2x2 jFETs of the buffer circuit. Am I right? Does anybody know if it is possible to fit the LSK389 in the Mezmerize boards? Thanks for any help you can give.
 
#68
AndrewT said:
A standard Mezmerise draws ~20mA for the Buffer plus the remaining CCS current draw and has to hold closed two relays fed from the negative side of the PSU.
It could manage with a 20VA 15+15Vac transformer.
100VA as Salas has mentioned is massive. 300VA was an aberration.
Click to expand...

Hi I use 7 VA toroids with good results in all my builds of the Mesmerize. I know it does not feel class A but it sure works OK 😉

BTW is this really correct in english ?

AndrewT said:
If want very simple go for B1.
Click to expand...
 
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#71
Hi everyone,

Slowly building my DCB1 and would like to ask a question regarding the psu part of the board. On the BOM it states that leds could be sourced from mouser part no 593-VAOL-3HCE4 which is what I did.

I then measured the voltage drop through the led pins for each one to match them. All 50 leds I bought measure 2.8V/+- 0.02V. I am not sure if these are the correct leds as I have seen in various posts that they should be more in the 1.8V region.

Can someone please verify if those are indeed the correct leds and if the psu will work with those leds.

Thanks
 
#73
Most probably, as their plastic is green coloured and they light blue when powered. I reordered another batch of 50 hopefuly this time they dont mess up again.

For the time being I use only two of those in the triplet spot (2*2.8V = 5.6) but and for the quintet spot only 3 (3*2.8V = 8.4V) I know that it should be more like 9.4V but I could not resist of testing it even as is.

Positive rail = 9.8V
Negative rail = 8.9V

wondering if I should do the the leg trick on that K170...

DC voltage at the buffer output (after a couple of mins):
Left: 0.1mV
Right: 1.1mV

haven't wired up a source and amp though yet. I guess I will have to restrain myself and wait for the leds to arrive (hopefully the correct ones this time)...

Also the voltage on the relays part of the circuit seems to be 11.75V and not 12V is this close enough for 7812? I thought they are pretty spot on give or take some milivolts but anyway.
 
#74
Your circuit basically works. Without leg trick the "jumpy" high VF Leds push the planned light asymmetry to heavier. But change those Leds eventually. They can even be noisy. Always use a limiting resistor when matching them while using a 9V battery or a PSU. 1K in series. The 7812 has 11.5-12.5V min-max official spec. Use a little flying sink on it.
 
#75
Duh... second batch of 50 leds received from mouser today seems to be the exact incorrect ones as the previous 50 batch ordered. 😡 Contacted their support and waiting for their response.

Hopefully sometime soon I will be able to sort this thing out....
 
#78
The space behind the normal RK27 outline on the Mez board is clear to the back edge, you better check the mechanical drawing of the motorized Alps to make sure there will be no obstruction.
 
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