There are magnetostatic hybrids too. I have a diyer friend who restored and modded an Eminent Technology LFT-8 older pair that sounds quite clean. Utilizes magnets in push-pull. Has a tighter membrane than an LRS+ that's crossed to a woofer around 180Hz. Well blended, better blend than in an Apogee Centaur in my experience, but you can still hear there's a cone taking over.
Soo mine is taking chape. Its going to be fun trying it out. Will start setting all levels again when idling for a while. Its now set up for the Ortofon MC 20 and its stepup transformer. 82ohm 40dB.
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Turned out well. Pilot lights combined with the needle voltmeter on the PSU look good. Nice detail the inputs hardwired short. So you set it for MM gain taking over from the Ortofon SUT?
Salas you are right. Set up with MC20 mkII super low and with SUT STM-72.
Great detail ang soundstage but I have some hum and will try to hunt it down.. Any suggestions?
Great detail ang soundstage but I have some hum and will try to hunt it down.. Any suggestions?
Yes but the amplification is not enough without it. I have also terminated input to see if hum comes from cart or sut add there is still some but not alot. I ca live with that but always nice to track some noice down.
I have tried to lift some earth bindings in raw psu but no success.
I will try to look at the scope to have some more clues...
I have tried to lift some earth bindings in raw psu but no success.
I will try to look at the scope to have some more clues...
Most possibly the interconnect wires (especially from cart to SUT) pick some hum. 40dB SUT + 40dB phono is 80dB so too big a magnifying lens.
Suggestions, first separate the PSU box further if it sits rather near to the phono box. Also place the phono away from power amps or other strong gear. Try lift one of the two PCB to green ground lug wires. Maybe the channels shields are already met in the SUT and there's a loop forming. You can also try lift one leg of the one of two 1R on the raw PCB.
40dB setting with input shorted normally brings inaudible hum with UFSP. Unless you got super sensitive loudspeakers with some high gain power amp.
Suggestions, first separate the PSU box further if it sits rather near to the phono box. Also place the phono away from power amps or other strong gear. Try lift one of the two PCB to green ground lug wires. Maybe the channels shields are already met in the SUT and there's a loop forming. You can also try lift one leg of the one of two 1R on the raw PCB.
40dB setting with input shorted normally brings inaudible hum with UFSP. Unless you got super sensitive loudspeakers with some high gain power amp.
I had the opportunity to listen to the Eminent Technology LFT-8, and I think that the key problem with such hybrids is the polar characteristic of the bass, which in this case works up to 180Hz in a closed box - but it doesn't mimic the dipole polar characteristic of a magnetostat, and it's audible in my experience. My hybrid has a sub-bass with a passive membrane located opposite the active bass and thus helps in a more natural integration with the dipole (of course at the expense of a worse impulse, but it is active, so it is easier to tune it).
Btw. Ultra now works with my hybrids and that sounds great to me.
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👍 Its a good sign when a new phono does well across different loudspeakers.
Hello again. I have tried it all not any difference in lifting ground and not either in lifting one 1R in RAW did any difference. I also tried to this with SUT and also with input grounded and they did both have the audible hum at medium/high listening levels. No hum if RIAA is turned off. Hope for some more things to try. And another thing I wonder about is: When setting Ubib i needed to adjust it to 32V to be able to reach 4volt at measuring point. How much is this suppose to drift within its interval? Have seen 3,7 to 4,3 volt after (3-4hours) some playing and idle time.
@Salas In the process of measuring the resonant frequency of my cart, I noticed a significant difference in subsonic energy between the FSP and another tube phono stage I have. The FSP clearly has more bandwidth but the increased level of LF seems less desirable?
What do you think?
What do you think?
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I think that the two phonos have different low bass and subsonic response by design. With more cut there's more phase shift in the audible bass and upper bass frequencies to low mids. In FSP and UFSP it is intentionally mild although there's still -20dB between 100Hz bass region and the 8.5Hz arm & cart resonance in your graph. You can make it steeper by smaller value C3 if you prefer. Suitability depends a lot on speakers size and room modes you got.
Thanks that makes alot of sense. 20dB is still 10X less voltage then probably fine. I also have the KAB fluid damper (not currently installed) and would be interested to see its impact.
I'll likely leave as-is but if going smaller, would you see the next reasonable value would be 0.047uF for C3?
I'll likely leave as-is but if going smaller, would you see the next reasonable value would be 0.047uF for C3?
Yes its next reasonable, and I have used that value in situations of higher Q loose bass reflex speakers and not well damped tonearms. C3 makes a CR high pass in combination with the 1Meg R7 of course but if you will utilize it don't make R7 smaller than 470k because the driving network impedance to C3 R7 is 47k. Its at 1:20 now but 1:10 impedance ratio is still acceptable.
Hi, 32V rail is normal for MM setting that's OK. Drift is normal to happen with the 2SK369s but when in MM mode not so much due to increased source degeneration resistor value when switched to the 40dB mode. Those Jfets are genuine from Tea right? I also hope there's no evidence of oscillations on the rails and outputs.
About your hum nuisance you mainly need a custom lower gain MM mode with that high gain SUT I believe. I will see about what values to advise you change. Meantime rub TT RCAs with contact cleaner, also the NOS SUT's input RCAs and its output interconnect RCAs to remove oxides if there. Also see if there's continuity between the two box frames via the umbilical. If there's a shield. We want that one way grounded at PSU box side. No other scenarios with grounding since it wasn't a matter of lifting the mains ground you said earlier.
@ForsbackaKalle
This is 34dB custom MM gain mode for you: R20 replace with 220 Ohm. Rail voltage adjust it to 28V. VR1 on phono board increase it to maximum Ω value for extra voltage drop (trims voltage between C7 and GND to lowest). T.P. might not be able to reach below 4.3V and that's expected. Switches normally set as to select the standard MM mode. Good luck.
This is 34dB custom MM gain mode for you: R20 replace with 220 Ohm. Rail voltage adjust it to 28V. VR1 on phono board increase it to maximum Ω value for extra voltage drop (trims voltage between C7 and GND to lowest). T.P. might not be able to reach below 4.3V and that's expected. Switches normally set as to select the standard MM mode. Good luck.
Thank you so much. So helpful. Hope to live after your example.
I will try your suggestion out.
I did clean some SUT RCAs and also shielded input connection inside the box. Maximized air gap from other transformers. And got a better result.
This thing really works well. Much detail and dynamic. Im really happy I buildt it. Now its really acceptable.
Will come back after testing 34dB custom mode.
I will try your suggestion out.
I did clean some SUT RCAs and also shielded input connection inside the box. Maximized air gap from other transformers. And got a better result.
This thing really works well. Much detail and dynamic. Im really happy I buildt it. Now its really acceptable.
Will come back after testing 34dB custom mode.
By the way have anyone tried Denon DL 301 mkII. I happen to get a good deal of that one and wonder if it could be a good match?