Simplistic NJFET RIAA

OMG...!!!!!

It works from the fist shot, from the beginning to the end of set up!
I'm listening a like a "live" music now! Amazing....
OK, all compliments will be later....

1. Here is my power setup:
Raw DC in -> (L=49.5v/R=49.5v)
B+ -> (L=32.9v/R=32.28v)
TP1/TP2 -> (L=3.6/R=3.6)
Whatever I did, I couldn't bring B+ to 33v and to have 3.6v on TPs.
I hope its OK to keep it as is.

2. I have some very little hiss at max volume on my tube Pre-Amp (no his when Folded is off or disconnected), but I'm not boxed yet and do not use any RC/CRC or LC/CLC variations on Raw DC either.

3. My 1236 AnTek transformer is making a small crackling noises and once in awhile (5 min or so) it makes scrunch sound (like something sparkles there). Is it normal?

Please see my pictures.
 

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I don't think any noise from the transformer is normal. You shouldn't be able to tell it's on without a meter. Are you sure the noises are coming from the transformer? Were I you I would double-check that all the AC power connections are tight; a loose connector could cause intermittent drop-outs, which you would not see on the DC supply because of the filter caps. I'm not sure what to make of a "scrunch" sound. Is the transformer warm at all?
 
I don't think any noise from the transformer is normal. You shouldn't be able to tell it's on without a meter. Are you sure the noises are coming from the transformer? Were I you I would double-check that all the AC power connections are tight; a loose connector could cause intermittent drop-outs, which you would not see on the DC supply because of the filter caps. I'm not sure what to make of a "scrunch" sound. Is the transformer warm at all?

Transformer is colt (it is 100VA 36-0-36 toroid). All connectors are tight and I'm almost 99% sure that this noise is coming from my toroid.
 
Odd. If you wanted to be sure you could wire up a dummy load (say 100-200 ohms) and see if the transformer makes any sounds when not connected to anything else like the circuit, meter, etc. (Nice case by the way, that front panel meter is bitchin'. What does it indicate? Raw PSU voltage?)

What's between the transformer and the case? Is there a rubber pad there? Any odd smells like something burning or volatiles like from varnish?
 
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Tonight I measured my transformers. They are rated 36V, but I measured 43.3VAC on each of them with no load. Adding a load of about 200R reduced that to 42.8V on both, and a 100R load (actually 97R) dropped them both to about 42.3 volts. I'll measure again tomorrow morning when presumably demand on the local power grid will be higher. But is that a little high? Should I consider a dropping resistor? I was already planning a CRC filter, but the R was just going to be some 0R22 wirewounds I have; if I need to drop a few volts then maybe a little higher resistance is in order.
 
Odd. If you wanted to be sure you could wire up a dummy load (say 100-200 ohms) and see if the transformer makes any sounds when not connected to anything else like the circuit, meter, etc. (Nice case by the way, that front panel meter is bitchin'. What does it indicate? Raw PSU voltage?)

What's between the transformer and the case? Is there a rubber pad there? Any odd smells like something burning or volatiles like from varnish?

You're right and it is simple to test. I'll take it out and test it tomorrow.

That box (I actually have two: one for PSU and one for phono) I got from eBay from Canadian guy:
He is not sale these now, but he might soon.
Yes, I measure 120V AC in to PSU.
 
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diyAudio Chief Moderator
Joined 2002
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Tonight I measured my transformers. They are rated 36V, but I measured 43.3VAC on each of them with no load. Adding a load of about 200R reduced that to 42.8V on both, and a 100R load (actually 97R) dropped them both to about 42.3 volts. I'll measure again tomorrow morning when presumably demand on the local power grid will be higher. But is that a little high? Should I consider a dropping resistor? I was already planning a CRC filter, but the R was just going to be some 0R22 wirewounds I have; if I need to drop a few volts then maybe a little higher resistance is in order.

You will need to drop 10V DC somewhere in the raw PSUs for about 100mA load each. +20% above nominal spec voltage on a Tx...how can you predict correct raw DC range on such tolerances? That is why I added Rdrop positions between bridge and filter cap on the raw PSU new GB board. Everybody should be testing their Tx before putting their PSU together.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
Hi Salas,

Why would Mills wire-wound be good resistors to use as Rsource?

Andy
Rsource run DC current so their excess noise characteristic can surface. Good wirewound types are counter-inductive wound also.
In our case the Rs values are small plus dropping in the tens of mV only so thin film resistors are good also. R13 should be more susceptible.
It runs both JFETS bias current on the highest Vdrop found in this circuit. Putting a KIWAME there would be much worse theoretically than putting a brown MR Mills for instance.

"The lowest noise level is observed in resistors with bulk metal resistive elements: foil and wirewound"
Selecting resistors for preamp, amplifier and other high-end audio applications | EE Times
 
Hi.

I thought about these regarding Q4, Q5 and Q6.

Q4 = 8,51mA
Q5 = 8,62mA
Q6 = 9,35mA

These are about the lowest and highest I got from Alawi in Israel. I bought 12 matched pairs but I have a feeling that some might do better in the Mezmerize. So I have 9 other values to play with - they are all between the above figures.

Caveat: I haven't checked them by myself yet - the xmas work :up:

Regards
 
Just Nice ? Ver very very nice !!!
Alex, can you post more details about it ?

I purchased two boxes like this from Canadian guy used to be on eBay (he does not sale this now, but he might in future). Not cheap, but very nice. It is vented aluminum top/bottom and North Canadian cherry wood.
Very thick front panel (7.5mm), so I was able to CNC it for my gauges.
However, it is not full metal enclosure and I added aluminum foil on wood pieces and made sure they are connected to the bottom and top aluminum parts (Faraday cage). I also used light Danish Oil on wood...
I like it!
 

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