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Old 27th March 2008, 05:46 AM   #1
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Default Anybody did compared tube vs opamp for preamp ?

Hello

Anybody did compared tube vs opamp for preamp or buffer, for musicality and soundstage quality ?

As examples, for tube it would be 12AX7 mu-follower or cathode-follower, and for opamp; OPA627, OPA637, THS4032, AD825 or LM4562.


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Gaetan
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Old 24th February 2011, 06:30 PM   #2
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hI,i would like to know the difference myself ,what better to use an opamp like AD 797 BR or JLH preamp for example or other not opamp based except tube,i hate tubes , i need for an amp project for now its a LM3886 but want to tune it to maximum
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Old 24th February 2011, 07:25 PM   #3
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Why do you need a preamp in front of an LM3886, while you can have all the necessary gain from LM3886 alone?
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Old 24th February 2011, 07:57 PM   #4
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yeah right ,im buildin the 4 x lm3886 in parallel 200w +btl,and on the original pcb i could use and ne5532 but i opted for 797br,and thinking instead of JLH class A Preamp,ill try both,just need to finish the amplifier
--a preamp will give me more control and lower noise--i could opt for dac instead of normal cd player line out and i have a sub that i intend to connect someday,even if i ll use 3 way floorstanders
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Old 24th February 2011, 07:59 PM   #5
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what do you think,it is possible with my project :|,can i do it ?
and i got some big toroid, owh its big weights 5 klo
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Old 24th February 2011, 08:24 PM   #6
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I don't know the schematic your project is based on, but I think NE5532 is wired as buffer (gain of 1), therefore I would stick with NE5532 at first...latter on you can experiment with another opamps which have to be stable at gain of 1. So, you don't need another preamp in front of BPA200. As for transformer, it is a matter of VA, secondaries AC voltage and if it is center tapped or split secondaries, but if you have only one transformer for both channel, you will have some trouble to avoid ground loops.
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Old 24th February 2011, 09:05 PM   #7
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Yes I have. I have a classic PAS2 preamp which last year had one channel low, not caused by tubes. So I bought a disco mixer with 4558 op amps to get by. I replaced all the paper caps in the high gain stage of the PAS2 with plastic film, and of course it was the last one that had the burned wax shell (hidden on the bottom, of course) that had caused it to deteriorate. I then changed the PAS2 plate resistors to metal film, changed the H.V. electrolytic cap, scrubbed and scrubbed to eliminate arcovers on the PCB's, and it now sounded better than the op amp mixer on both my transistor amps, the ST120 with DJoffe bias mod, and the Peavey CS800S. A little less hiss than previously idling, and much less hiss than the disco mixer. However, the volume pot on it is stuck; a new Stereo Cost Cutters OEM pot from the Dynakit bankruptcy reject room. Has to be turned with vice-grip plers. Haven't found any stereo 250k log replacements with the loudness track.
So I bought some 33078 op amps for the disco mixer, which had great slider pots. Quieted the hiss right down, but it had maybe -40db of hum. Long war on hum ensued, grim details on Improving a "Disco mixer" to mid-fi performance. At the end the disco mixer has equivalent hiss, equivalent lack of distortion on top octave steinway piano, and a tiny bit more hum than the PAS2. Have to stand 20 cm from speakers to hear the hum. Have a question going on analog line level thread about changine the RIAA curve parts on the disco mixer for even less hiss (kitchen sink preamp post). Both Pas2 and Disco mixer sound the same into a dynakit ST70 with new output tubes, but ST70 mid range piano is honkier than either transistor amp. Top & bottom octaves sound nice. Looking at a triple twin triode input board for the ST70, but the triodeelectronics.com version is designed for EF86's of which they sell only a poor eastern block copy. (6pi something tube is what I got from them) I'm not into etching PCB's anymore.
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Last edited by indianajo; 24th February 2011 at 09:15 PM.
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Old 24th February 2011, 09:16 PM   #8
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you know youre funny )
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Old 24th February 2011, 11:35 PM   #9
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I used to be a 'tube-guy' thru-and-thru, but when I needed a MC phono preamp, I decided to take a chance on Audio Sector's OPA627-based unit and I was pleasantly surprised. Very transparent and detailed, it sounds like nothing else I've heard before. So now I'm not so quick to slam SS - but I certainly give tubes the nod for ruggedness and ease to work on. In my experience, it certainly is easier to build a good tube unit than SS.
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Old 25th February 2011, 01:29 AM   #10
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Quote:
Looking at a triple twin triode input board for the ST70, but the triodeelectronics.com version is designed for EF86's of which they sell only a poor eastern block copy.
Yes, St. Petersburg made EF86 equivalents are not good. However, you are not restricted to COSTLY NOS to get good sounding EF86s. New Sensor's Saratov, Russia, plant currently makes 2 good varieties: the EH labeled tube is good and not especially expensive. The TungSol labeled tube is not inexpensive, but still remains affordable, and it's very good.

FWIW, I'm fond of the TE replacement ST70 driver board populated with 2X EF86s and an ECC99, as it retains Dyna's small signal topology, while using better pentodes and triodes than those found in 2X 7199s.
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