Mbira
Well-known member
I think the eq problem is because you are not going into a phono pre now. I imagine once you get the signal boosted, the eq will settle down. I'd suggest to try that first before also building an eq.
Need some suggestions for a preamp for a record player.
- Thread starter Ptownkid
- Start date
Help Support GroupDIY Audio Forum:
Ptownkid
Well-known member
Yeah, from what i've read, riaa eq will do the trick
> it seems like over kill.
It may be. But most of the "affordable" phono preamps are crap.
"Radio Shack sells an okay one" I disagree. It wasn't really good enough for me 30 years ago, which is why I rolled my own.
With modern asian production, it "should" be trivial to make a very-decent phono preamp for $25 retail.... but the TAA review says that they all (up to ~$99 at least) have major (and stupid) flaws. IIRC (i may not), the Rolls had 2dB erro all through the high-end, a really annoying flaw. Some other didn't roll-off the highs at all. The ART has so much subsonic noise that power amps panic.
Having a GOOD phono preamp is a joy. I never regretted rolling my own, but it was a lot of messing around.
I'm really annoyed that there isn't a sub-$99 phono preamp that I can live with. I did hack the ART, to lose the subsonic 1/f noise and get the EQ closer to right, but that shouldn't have been necessary.
> I'm a little put off by the $40 price tag for a pcb
It's Jim's full-time bill-paying hobby. He's doing good work, both at the walnut-box kilobuck end and with ~$99 gizmos like a USB dongle and an affordable phono preamp that does not suck at ALL. Yeah, you are paying for a house in Hawaii rather than a chinese slum like most other affordable audio products. Your choice to pay his price, or not.
> from what i've read, riaa eq will do the trick
Well, duh. Tape heads need tape-head preamps. Even mikes need mike preamps. Magnetic phono needles need an appropriate phono preamp. Historically, this was built into the control/power amp, not in the transport as tape decks do. And at a later stage of history, control/power-amp builders omitted the $10 phono stage (you could just shop rummage sales, find a nice $20 Sansui from 1976, it may have an adequate phono stage). You "can" play records by cranking the gain and slamming the Bass/Treb to the stops, but it ain't right. The phono preamp makes it right.
Rod Elliot's phono stage will be fine and cheap. It will work very fine with a TL072; the 5532 is not necessarily lower-noise in mag-needle use, and the high-end grit in the TL072 is largely masked by the typical phonodisk's flaws (which through the 1980s, would have included a dozen BiFET chips or worse in the mastering signal path). Fun to try both, but if all you have is Radio Shack's Partz Close-Out rack, you can do a fine phono preamp with TL072 and carbon-film.
It may be. But most of the "affordable" phono preamps are crap.
"Radio Shack sells an okay one" I disagree. It wasn't really good enough for me 30 years ago, which is why I rolled my own.
With modern asian production, it "should" be trivial to make a very-decent phono preamp for $25 retail.... but the TAA review says that they all (up to ~$99 at least) have major (and stupid) flaws. IIRC (i may not), the Rolls had 2dB erro all through the high-end, a really annoying flaw. Some other didn't roll-off the highs at all. The ART has so much subsonic noise that power amps panic.
Having a GOOD phono preamp is a joy. I never regretted rolling my own, but it was a lot of messing around.
I'm really annoyed that there isn't a sub-$99 phono preamp that I can live with. I did hack the ART, to lose the subsonic 1/f noise and get the EQ closer to right, but that shouldn't have been necessary.
> I'm a little put off by the $40 price tag for a pcb
It's Jim's full-time bill-paying hobby. He's doing good work, both at the walnut-box kilobuck end and with ~$99 gizmos like a USB dongle and an affordable phono preamp that does not suck at ALL. Yeah, you are paying for a house in Hawaii rather than a chinese slum like most other affordable audio products. Your choice to pay his price, or not.
> from what i've read, riaa eq will do the trick
Well, duh. Tape heads need tape-head preamps. Even mikes need mike preamps. Magnetic phono needles need an appropriate phono preamp. Historically, this was built into the control/power amp, not in the transport as tape decks do. And at a later stage of history, control/power-amp builders omitted the $10 phono stage (you could just shop rummage sales, find a nice $20 Sansui from 1976, it may have an adequate phono stage). You "can" play records by cranking the gain and slamming the Bass/Treb to the stops, but it ain't right. The phono preamp makes it right.
Rod Elliot's phono stage will be fine and cheap. It will work very fine with a TL072; the 5532 is not necessarily lower-noise in mag-needle use, and the high-end grit in the TL072 is largely masked by the typical phonodisk's flaws (which through the 1980s, would have included a dozen BiFET chips or worse in the mastering signal path). Fun to try both, but if all you have is Radio Shack's Partz Close-Out rack, you can do a fine phono preamp with TL072 and carbon-film.
PRR what old TAA project did you use? I have TAA from 1970 to the early 80's
My pre is a tl074 based one with output pulldown resistors, passive EQ with polystryenes. Kind of based on the one from a Walt Jung AES paper 79 or 80and the pat5 White Jung one.
Did not cost much but I tested/selected the gain resistors for side to side balance and tested the Caps and resistors for the EQ.
My pre is a tl074 based one with output pulldown resistors, passive EQ with polystryenes. Kind of based on the one from a Walt Jung AES paper 79 or 80and the pat5 White Jung one.
Did not cost much but I tested/selected the gain resistors for side to side balance and tested the Caps and resistors for the EQ.
Ptownkid
Well-known member
[quote author="PRR"]
Well, duh. Tape heads need tape-head preamps. Even mikes need mike preamps. Magnetic phono needles need an appropriate phono preamp. [/quote]
Ok, c'mon now, I never pretended to be an expert, I was just pointing out that I now understand why I don't need eq other than the circuit itself.
I will probably just buy the pcb in question.
When i said seems like overkill, I was tlaking about the one with the power supply and faceplates...I think the battery op is the way to go.
Well, duh. Tape heads need tape-head preamps. Even mikes need mike preamps. Magnetic phono needles need an appropriate phono preamp. [/quote]
Ok, c'mon now, I never pretended to be an expert, I was just pointing out that I now understand why I don't need eq other than the circuit itself.
I will probably just buy the pcb in question.
When i said seems like overkill, I was tlaking about the one with the power supply and faceplates...I think the battery op is the way to go.
> what old TAA project did you use?
Oh, come on. If I say I remembered the 1970s, then obviously I wasn't there.
TAA Vol V Number 4, April 1975, says "4/74" on the cover, with a picture of a phono headshell.
Page 4, PREAMP, Richard R. Moore.
GOOD essay on phono preamp design.
C3 and C1 interact to give subsonic peaking. 5K in series with C1 fixes this, but is a bodge. One trick I used was to wire the (floating!) cartridge in parallel with R6, omitting C1. This does flow many nanoAmps of DC in the cartridge. The other trick was about 5,000uFd at C3, which moves the C3-C1 peaking so far down that we don't care.
I also took R3 well below 15K, and made R4 R5 smaller in proportion.
Since gain has to be high to reduce supersonic error, the suggested 27V supply may be marginal for hot recordings. I used about 36V raw, with R-C decoupler (no regulation!) for about 32V at the rail. 48V would be better. Fiddle R5 to keep the output DC at about 40% of the supply voltage.
Oh, come on. If I say I remembered the 1970s, then obviously I wasn't there.
TAA Vol V Number 4, April 1975, says "4/74" on the cover, with a picture of a phono headshell.
Page 4, PREAMP, Richard R. Moore.
GOOD essay on phono preamp design.
C3 and C1 interact to give subsonic peaking. 5K in series with C1 fixes this, but is a bodge. One trick I used was to wire the (floating!) cartridge in parallel with R6, omitting C1. This does flow many nanoAmps of DC in the cartridge. The other trick was about 5,000uFd at C3, which moves the C3-C1 peaking so far down that we don't care.
I also took R3 well below 15K, and made R4 R5 smaller in proportion.
Since gain has to be high to reduce supersonic error, the suggested 27V supply may be marginal for hot recordings. I used about 36V raw, with R-C decoupler (no regulation!) for about 32V at the rail. 48V would be better. Fiddle R5 to keep the output DC at about 40% of the supply voltage.
pstamler
Well-known member
Walt did a revision of his PAT5 mod changing the EQ to passive, which also eliminated the signal inversion while maintaining the rolloff that doesn't quit. I think it was sometime in 1979, but not certain.
Peace,
Paul
Peace,
Paul
pstamler
Well-known member
[quote author="mediatechnology"]I'll look for the later TAA article and post it if I find it.[/quote]
I think it was just a letter to the editor.
Peace,
Paul
I think it was just a letter to the editor.
Peace,
Paul
