Salas,
I put 10 ohm 10w resistors between the bridge and the cap as you suggested. Now down to 52v. Fired it up today with everything in the open on a board. No noise at all. Sounds like a little too much treble and a little thin. The kind of thing I find in stuff that has not been on for more then a few minutes. Still what is there sounds promising considering I have not done any tweaking.
Thanks to you and Tea Bag for bringing this phono preamp to us.
John
I put 10 ohm 10w resistors between the bridge and the cap as you suggested. Now down to 52v. Fired it up today with everything in the open on a board. No noise at all. Sounds like a little too much treble and a little thin. The kind of thing I find in stuff that has not been on for more then a few minutes. Still what is there sounds promising considering I have not done any tweaking.
Thanks to you and Tea Bag for bringing this phono preamp to us.
John
Nice it works without a problem. Make sure you got the right gain and load for your cartridge first, then tweak VTA and make C2Y value higher if still thin after a couple of days. Its not tilted toward treble by nature of design, so see to overcome that by tweaking if it will persist. What is the cartridge and what gain you built by the way? What C2Y and C3 used?
Hi Salas
Sorry to ask whats probably been well documented somewhere in this thread already but, what are the design values for RIAA network components?
I prefer to measure and trim my components to as close to design as possible and then work from there if further trimming needed - Ive got a DE-5000 LCR meter so lets make it work right....
Sorry to ask whats probably been well documented somewhere in this thread already but, what are the design values for RIAA network components?
I prefer to measure and trim my components to as close to design as possible and then work from there if further trimming needed - Ive got a DE-5000 LCR meter so lets make it work right....
Good job U ask at 03:45 Am here GMT do this after o9:00 and tread police will tell U to read the tread from start.
So while public library whit free aces to OAP is closed I join in and say good question
handy to have 3 decimal places figures but IMO so as one can approximate the right way
I not a real fan of exact values for those considering how much twiddling of twidable knobs goes on in the studios
Real importance is in matching the 2 channels so please give us formulae as well as I prefer to play whit the capacitors values on a fixed/measured resistor set
So while public library whit free aces to OAP is closed I join in and say good question
handy to have 3 decimal places figures but IMO so as one can approximate the right way
I not a real fan of exact values for those considering how much twiddling of twidable knobs goes on in the studios
Real importance is in matching the 2 channels so please give us formulae as well as I prefer to play whit the capacitors values on a fixed/measured resistor set
Hehe yeah I getcha Bksabath..., Ive already read this thread once thru and it did my head in... Salas etal in this thread are gentlemen here and appreciate the sheer size of this thread and are willing to help ... A big suckup in advance advance
Fully agree that channel matching is way more important and thats what I got the LCR meter for. I dont want obsess over abs values etc but I would like to confirm design values and know if the bits I got are either converging or diverging away from design...
I also preferentially use polystyrene as once values are selected they are usually VERY stable over time and likely to stay close to optimal (essential for the RIAA network). From experience it doesnt matter if you have a bunch of 1 or 10%, as 1 and 2.5% etc are just selected from manufacturing runs anyway and out of range are sold as 5 and 10%.... Of course this only really applies for competent manufacturers...
I use online RIAA calculators, which brings us back tooo.... has the input stage output impedance been factored into R14 or is it low enough to ignore... if so I could just plug in R14 and recalc RIAA caps ..
Ive got the GroupBuy boards, just putting together components, so this my driver for these questions..
Hello, the RIAA components are R14, R5, R6, C1, C2, and C2Y (HF trim cap) with values as listed in the pdf guide. They do take into account the input stage's source impedance and the Miller capacitance HF loading of the second stage.
Yes agreed. There are at least 0.9pF offset when using the TL-21, I have a few ref polystyrene caps (over ea decade and 3 units at each decade) that Ive had calibrated by a buddy at local university EE dept... its worth the effort. I keep them in a safe them all together in the box and in a thermally stable location...
Legally defensible traceable calibration was my job for >20yrs old habits linger.
I had elongated and reinforced my TL-21 to make it handier since one original short wire became erratic. Can also grab those speaker air core big coils now.🙂 The TL-22 SMT pincher is nice though. Can help with many small through hole components too. It just takes to note the deviations vs the body slots and to run the calibration routine each time when changing the Kelvin(ish) leads type used.
Attachments
I have same problem with my TL-21. I already replaced crocks since the original were really poor quality and they did not lock tightly.
The tools we use are only as good as the way we use them. ie maintenance and a clear understanding of its limitations are essential when pushing the limits
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Its because very short and soft so they soon get tired mechanically by trying to grab biggish capacitors etc. I changed with sturdy jacket microphone wire and hefty crocks. All sense and shield connections used as in the original configuration of course. Not an easy operation, the thicker cable was a tight fit.
I'm also very gentle user and always keep all my equipment in perfect shape. I'm fully agree with Salas.
Salas,
I built it for 58db. The cartridge is a Lyra Argo, using 100 ohm loading. No capacitor in C2Y and 47n for C3. Added the 100n polystyrene last night at C2Y, but did not have time to listen to it. This is a fun project with all the potential tweaking the sound.
John
I built it for 58db. The cartridge is a Lyra Argo, using 100 ohm loading. No capacitor in C2Y and 47n for C3. Added the 100n polystyrene last night at C2Y, but did not have time to listen to it. This is a fun project with all the potential tweaking the sound.
John
Using no C2Y initially can partially explain some tendency to treble. It may take yet another 100pF in the end. 15.2nF=C2+C2Y is the recommended neutral to start with in the manual.
"C2Y treble trim. If you got a 0.5% or better LCR meter measure each C2 15nF 1% nominal cap and note its exact value. Measure to find a C2Y trim cap so C2+C2Y=15.2nF. Gives almost neutral RIAA curve.
Use the most tonally balanced input load value for your cartridge in combination. If you don't have such a meter, install random C2 1% and 200pF up to 5% C2Y.
By listening, if the treble is dull exchange for 100pF. If its bright exchange for 300pF. You may use 50pF intermediate value piggyback on C2Y if you can hear differences.
Its an opportunity to tune your phono preamp to the tonal balance of your TT and speakers. Verify VS listening to other audio sources."
Let us know what value(s) you ended up with.
"C2Y treble trim. If you got a 0.5% or better LCR meter measure each C2 15nF 1% nominal cap and note its exact value. Measure to find a C2Y trim cap so C2+C2Y=15.2nF. Gives almost neutral RIAA curve.
Use the most tonally balanced input load value for your cartridge in combination. If you don't have such a meter, install random C2 1% and 200pF up to 5% C2Y.
By listening, if the treble is dull exchange for 100pF. If its bright exchange for 300pF. You may use 50pF intermediate value piggyback on C2Y if you can hear differences.
Its an opportunity to tune your phono preamp to the tonal balance of your TT and speakers. Verify VS listening to other audio sources."
Let us know what value(s) you ended up with.
I got a chance to listen to it today. Definitely moving in the right direction. I am going to let it run in for a while, plus the cables I was using do lean slightly to the bright side. I may add a little more to C2Y over the next couple of weeks. Right now I am using the stock capacitor 15nF supplied by Tea Bag plus the 100pF from the kit. I don't trust my meter too much. It says I am at 15.2.
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By this trend you report after adding the first C2Y we can conclude that there is no peculiar curve error in your build. It reacts normally. Congratulations. Keep us posted, pictures are welcome too.
hi
i cannot find sk369 in korea 🙁
i put in 170 but it make no sound. output buffer work tho i know.
369 alternative? i want to listen today! 😀
i cannot find sk369 in korea 🙁
i put in 170 but it make no sound. output buffer work tho i know.
369 alternative? i want to listen today! 😀