No problem, as long as it's lowish capacitance. I would suggest 3 very thin wires, twisted. If used balanced it will be humm pickup free, if unbalanced then use two wires for earth, but only ONE of then connected at both ends.
Regards, Allen
I think he used FETs, but a high-gain BJT cascode (with red led) should work too I guess.
(Arhus Triode Festival 2002)
Try googling for low noise CCS, or search on this board.
(Arhus Triode Festival 2002)
Try googling for low noise CCS, or search on this board.
I gather that Allen was until recently using Wima FKP2 polypropylene film and foil caps for the phono EQ. I don't know whether that was mainly because of their ready availability and low price, but I would guess that he found them at least acceptable for the purpose.
Here is a comment of his on the subject.
Alex
Here is a comment of his on the subject.
Alex
Just a slightly OT comment as I own several different sets of SUTs and have to mention that while very good for the money the Cinemag is hardly representative of the performance achievable in a SUT. The Partridge 972, 977 and several Lundahl types will run circles around it. (There are lots of others at progressively higher prices that are even better.)
Currently working on building the RTP3
Vacuum State - High End Hifi Equipment
I have this cct to use as the ccs. I just want to check before I proceed that I connect the -25V to the supply (obviuos) and the 0v connection to 'point c' indicated on the schemtic between the two emmiter resitors of the MAT02?
I have a LOMC so won't be using them but am considering using a 4PDTswitch allowing the 332 ohm to be selected for mm.
2nd question is are two 0,47UF caps in parallel close enough in value to the 1.0 uf caps?
Rhanks for your help
Craig
Vacuum State - High End Hifi Equipment
I have this cct to use as the ccs. I just want to check before I proceed that I connect the -25V to the supply (obviuos) and the 0v connection to 'point c' indicated on the schemtic between the two emmiter resitors of the MAT02?
I have a LOMC so won't be using them but am considering using a 4PDTswitch allowing the 332 ohm to be selected for mm.
2nd question is are two 0,47UF caps in parallel close enough in value to the 1.0 uf caps?
Rhanks for your help
Craig
Attachments
![RTP3_CCS[1].gif](/community/data/attachments/219/219635-96af856a7418ef510099275788791917.jpg)
Hi Craig,
Looks like the "old" RTP3c schematic you linked to only were prepared for a single CCS and not a dual CCS as you plan to use.
The two CCS should not be connected to the zero point. Instead they should be connected to the respective emitters of the MAT02. Between the emitters you have one resistor to set the gain.
The second question. Which 1.0uF cap? The one connected to LM329? It's not critical but why not use a single 1.0uF?
The two 1.0uF coupling caps are critical and should be matched (as every other component in the RIAA correction circuit.)
I recommend to order the instruction CD from vacuumstate.com, the money spend will insure that one get the RTP3 build as intended. Second, use what Allen recommended of components and substitute later. Have fun!
Thanks Kim.
The gain for MC if i understand correctly is 0R therefore no resistors. This dual ccs is to have half the current 9.5 mA flowing in each side.
The coupling caps. I was thinking of using some russian teflon caps.
I agree about the cd. Unfortunately it is no longer for sale from vacuumstate. perhaps someone has one they are willing to sell?
Craig
The gain for MC if i understand correctly is 0R therefore no resistors. This dual ccs is to have half the current 9.5 mA flowing in each side.
The coupling caps. I was thinking of using some russian teflon caps.
I agree about the cd. Unfortunately it is no longer for sale from vacuumstate. perhaps someone has one they are willing to sell?
Craig
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I agree that the components in the shunt part of the correction circuit (between the anodes of the valves) should be chosen to at least 1% and matched between channels to within better than this, but in my opinion the coupling caps after the phone stage (which, incidentally, in the version I used are 0.47 uF) are less critical: with my values the LF corner frequency is around 7 Hz, and 5% deviations for this are unlikely to be audible
Alex
Hi Craig,
The circuit I sent you should be inserted between the -25V unregulated supply and the emitter resistors of the input stage (which are absent for the standard LOMC configuration, in which case the CCS is connected directly to the emitters).
You measure the voltage across each of the fixed 1K0 resistors in the CCS in turn and adjust the pots in series with these: when the voltage is 9.5 V across both of the resistors, the current through each should be 9.5 mA and the total through the tail of the input stage 19 mA.
Alex