I had made a phono amp with 5 5670/2C51 yet. however its hums....... i think its because the signal from power transf... I did not seperate them well and only use single solid line. I dont want to deal with it now maybe latter(its a little diffucult for me to re-built).
I still have some 6SN7 and 6J5 and this Time I want to try use them 1 6J5 1 6SN7 for 1 chl . I prefer RC for RIAA and If anyone had scheme or have any hint.
I still have some 6SN7 and 6J5 and this Time I want to try use them 1 6J5 1 6SN7 for 1 chl . I prefer RC for RIAA and If anyone had scheme or have any hint.
The RCA Phono preamp schematic uses 12AX7's and you can sub in 6SL7's (can be microphonic, however), but not sub in 6SN7. I only suggest this as it keeps you in the octal tube family. Otherwise, I'd go for something like a 6DJ8 based design. Check out Vacuum State's web site for schematics of phono sections that are pretty darn good.
I designed a 6SL7 phono stage with 6SN7 follower on the output of it.... I posted it in a folder on a NewGroup a number of years ago... It was in "Yahoo Groups" Some kind of tube group....it's been awhile and i forget exactly...
If you look in one of the schematic folders is should be there....
If I cab find it again..then I will post it here..
Chris
If you look in one of the schematic folders is should be there....
If I cab find it again..then I will post it here..
Chris
I found from tube CAD Journal
a single triode RIAA equalized preamp. Usually a cathode resistor is bypassed with a large valued capacitor, so as to ensure adequate low- frequency response. But if the bypass capacitor's value is reduced greatly, it introduces a shelving function, wherein the high-frequency gain is greater than the low-frequency gain, with the ratio being equal to the bypassed gain over the unbypassed gain or
1 .
Ratio = 1 + (mu + 1)Rk
Ra + rp
The transition frequencies are based on the capacitor's value and the time constants it forms with the triode's rp and its plate and cathode resistor values:
RkCk = 75µS
[(Ra + rp)/(mu + 1) || Rk]Ck = 318µS
Of course, one triode is not going to provide enough gain in most cases, so additional gain stages will be needed.
The overarching liability of this different path to RIAA equalization is the -12dB insertion loss beyond the expected losses, which brings it 1kHz insertion loss down to -32dB. With this equalization network, the near DC and subsonic frequencies are reduced by -12dB, whereas the traditional path retained all of the gain at the bottom of range. Now, -12dB is just too much to pay in most two-gain-stage phono preamps, but it is almost nothing in a three-gain-stage preamp, where the problem is usually having too much gain. Still the advantage of using a portion of the equalization network in double duty either, as a pseudo coupling capacitor or a partial cathode-bypass capacitor, is tempting.
how about it
a single triode RIAA equalized preamp. Usually a cathode resistor is bypassed with a large valued capacitor, so as to ensure adequate low- frequency response. But if the bypass capacitor's value is reduced greatly, it introduces a shelving function, wherein the high-frequency gain is greater than the low-frequency gain, with the ratio being equal to the bypassed gain over the unbypassed gain or
1 .
Ratio = 1 + (mu + 1)Rk
Ra + rp
The transition frequencies are based on the capacitor's value and the time constants it forms with the triode's rp and its plate and cathode resistor values:
RkCk = 75µS
[(Ra + rp)/(mu + 1) || Rk]Ck = 318µS
Of course, one triode is not going to provide enough gain in most cases, so additional gain stages will be needed.
The overarching liability of this different path to RIAA equalization is the -12dB insertion loss beyond the expected losses, which brings it 1kHz insertion loss down to -32dB. With this equalization network, the near DC and subsonic frequencies are reduced by -12dB, whereas the traditional path retained all of the gain at the bottom of range. Now, -12dB is just too much to pay in most two-gain-stage phono preamps, but it is almost nothing in a three-gain-stage preamp, where the problem is usually having too much gain. Still the advantage of using a portion of the equalization network in double duty either, as a pseudo coupling capacitor or a partial cathode-bypass capacitor, is tempting.
how about it
Attachments
I had only 1 12AX7 so ...
and 2 *RCA 6SL7 4 *CEI
but many people saied too noise?
I also have lots of 6ER5 6GK5 6BK7...... maybe good choise but not good in THD
the 2C51 I made is too noise......maybe the problem comes from the line and transformers
I only have 1SEIMS and 1 SYLVANIA 6922 so not enough
bot I have lots of 6N1P
maybe I'll try 6N1P
and 2 *RCA 6SL7 4 *CEI
but many people saied too noise?
I also have lots of 6ER5 6GK5 6BK7...... maybe good choise but not good in THD
the 2C51 I made is too noise......maybe the problem comes from the line and transformers
I only have 1SEIMS and 1 SYLVANIA 6922 so not enough
bot I have lots of 6N1P
maybe I'll try 6N1P
hagtech said:
Hey..thats totally cool!!!!
I noticed your circuit is passive RIAA EQ....nice....
My circuit was active with the feedback loop...
I go through two stages of 6SL7 then direct coupled to a 6SN7 follower then the feedback is taken from the follower output back to the cathode of the first 6SL7 gain stage... I also have small feedback "between" the cathodes of the first two 6SL7 cathodes...
I can say that the octal phono-pre is FAT sounding but still LINEAR and makes the vinyl sound luxurious WITHOUT colorization.....
My best phono-pre was a cascoded 6SN7 ....very dynamic and open....
Chris
I'll just reprint an email I got a few weeks ago...
Thank you so much for the excellent phono stage design. I haven't been able to stop listening to records for a few nights, now. My wife thinks I'm more nuts than ever. It really is boss, sir. I've a renovated Audio Research SP6B preamp, which, as you likely know, comprises a well-regarded phono stage. I've enjoyed it. Until now, that is. I tried to switch back yesterday, just for kicks. Nice product, Mr. Johnson, quiet as a church mouse (with a few tweaks from me, anyway) but it cannot shine the octal Cornet's shoes. And that's a fact.
jh
In 1/04, and 2/04, Audio Express Magazine, James Lin describes a preamp which he calls "Canto Sirena", that's derived from an earlier design of J.C. Morrison, named "Siren Song". The circuit features a 6SL7, as a first stage differential pair, followed by a 6SN7, for the second stage differential pair. The output stage is a 6J5, which is "half " of a 6SN7. The circuit also features passive RIAA equalization. In the article, the author discusses the possiblity of using other tubes, such as a 6N7 substituted for the 6J5, or, of course Loktals, which, as I recall, were in the original "Siren Song.
I'm quite impressed after reading the designers' explanation of his approach to the circuit, including the two-stage, split equalization and his consideration of the "Miller Effect", which is significant in these tubes. As a result, I'm very seriously considering building this, as I'm also sort of a fan of Octal tubes!
Has anyone here had experience (good or bad) with either of these designs, or a similar item?
I'm quite impressed after reading the designers' explanation of his approach to the circuit, including the two-stage, split equalization and his consideration of the "Miller Effect", which is significant in these tubes. As a result, I'm very seriously considering building this, as I'm also sort of a fan of Octal tubes!
Has anyone here had experience (good or bad) with either of these designs, or a similar item?
hagtech said:
I will definitely build this phonostage.
As Hammonds are not readily available where I am, is HT a 270-0-270? Lucky for me, custom wound power transformer are relatively inexpensive?
Also, how much current goes through each triode, two 6sl7 stages and the 6sn7 stage? (sorry, am a newbie and I need to double check my computations).
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