I'm into audio restoration and preservation of analog sources - LP's, 78's, tapes, etc..
The problem I have had over the years is excessive gain from my phono preamp driving my sound cards. The audio card mixer can turn the volume down, but cannot do anything with an overload input signal. I started with a Hoontech/STAudio card, updated to a M-Audio Delta card, and now I'm using an ESI Julia in my newer computer, but I still had the same issue.
To solve this problem I purchased some F-Mods from Parts Express. This helped, but couldn't stop wondering if they were adversely affecting the sound. In an attempt to improve, I replaced them with a pair of higher quality Rothwell inline attinuators. But I have read even these affect the sound.
Both of these units use simple resistors. What bothers me is I have always been with the understanding that resistors are not the right way to do it. LC attinuators are the ONLY proper approach. But the only ones I can find anywhere are only for use with fiber optical audio. What am I missing here? Any suggestions?
The problem I have had over the years is excessive gain from my phono preamp driving my sound cards. The audio card mixer can turn the volume down, but cannot do anything with an overload input signal. I started with a Hoontech/STAudio card, updated to a M-Audio Delta card, and now I'm using an ESI Julia in my newer computer, but I still had the same issue.
To solve this problem I purchased some F-Mods from Parts Express. This helped, but couldn't stop wondering if they were adversely affecting the sound. In an attempt to improve, I replaced them with a pair of higher quality Rothwell inline attinuators. But I have read even these affect the sound.
Both of these units use simple resistors. What bothers me is I have always been with the understanding that resistors are not the right way to do it. LC attinuators are the ONLY proper approach. But the only ones I can find anywhere are only for use with fiber optical audio. What am I missing here? Any suggestions?
=Opinion warning=
I think you are chasing the placebo effect. What will make you =feel= the best? What type of cable and connections sit between your phonograph and the pre-amp? What kind of phono pre-amp do you have? It's certainly filled with resistors, capacitors, and active devices that are distorting your audio and introducing noise, inevitably and undeniably so. What about your sound card? How many non-audiophile crappy surface mount resistors and capacitors and chips with microscopic noisy non-audiophile circuitry does the audio pass through before getting chopped up and sampled by the A2D? How much noise and distortion are being introduced by the EMI from the clocks, processors, and switching power supplies inside the audio card and the computer chassis.
In the grand scheme of things, your F-Mods or Rothwells are the best, practically aerospace quality, gold plated, "as close to zero impact" you can possibly achieve, and certainly the most stellar compared to all of the manipulation and corruption happening elsewhere upstream and downstream. If you have enough of a golden ear to really hear a difference in an authentic blind test, then perhaps a different phono pre-amp is necessary so you can tame down the output. You could modify the pre-amp to change it's output level, but that would be performed by adding or altering the existing resistors that are almost certainly not as excellent as in your attenuators.
I think you are chasing the placebo effect. What will make you =feel= the best? What type of cable and connections sit between your phonograph and the pre-amp? What kind of phono pre-amp do you have? It's certainly filled with resistors, capacitors, and active devices that are distorting your audio and introducing noise, inevitably and undeniably so. What about your sound card? How many non-audiophile crappy surface mount resistors and capacitors and chips with microscopic noisy non-audiophile circuitry does the audio pass through before getting chopped up and sampled by the A2D? How much noise and distortion are being introduced by the EMI from the clocks, processors, and switching power supplies inside the audio card and the computer chassis.
In the grand scheme of things, your F-Mods or Rothwells are the best, practically aerospace quality, gold plated, "as close to zero impact" you can possibly achieve, and certainly the most stellar compared to all of the manipulation and corruption happening elsewhere upstream and downstream. If you have enough of a golden ear to really hear a difference in an authentic blind test, then perhaps a different phono pre-amp is necessary so you can tame down the output. You could modify the pre-amp to change it's output level, but that would be performed by adding or altering the existing resistors that are almost certainly not as excellent as in your attenuators.
LC circuits (with at least one termination resistor) are normally used as filters, not attenuators. A resistive voltage divider is a very normal approach to make an attenuator.
I also wonder what kind of phono preamplifier you use, considering that you need a different equalization for 78s and early LPs than for later records. Some model of archival preamplifier with switchable time constants?
I also wonder what kind of phono preamplifier you use, considering that you need a different equalization for 78s and early LPs than for later records. Some model of archival preamplifier with switchable time constants?
Resistors are definitely the correct way to attenuate an audio signal. They are essentially perfectly linear from DC to many 100's of kHz (and usable up to many 10's and even 100's of MHz) when dealing with the sort of parts we use in audio.
One important question is what sort of load impedance your phono preamp can drive and how that relates to the attenuator values you have chosen. For example a valve phono stage with a high output impedance might not give its best if loaded with say a 10 or 20k attenuator.
One important question is what sort of load impedance your phono preamp can drive and how that relates to the attenuator values you have chosen. For example a valve phono stage with a high output impedance might not give its best if loaded with say a 10 or 20k attenuator.
Thanks for the input. I have been using a low output moving coil cart with a PSAudio Phonolink II as my workhorse preamp. I have just recently replaced the stock Class AB OP amps in that unit with SS3601 Sparkos Discrete Class A upgrades. (have not tried it yet - my system is presently disconnected awaiting a new rack cabinet) I have been feeding that directly to an ESI Julia soundboard in my custom built audio computer. That sound card is so good it has been tested against professional A to D converters and all though not quite as good, they were blown away how close it came. I either restore & clean up used LP's with Diamond Cut audio tools, or I will preserve new LP's at 24bit/192khz before any information has been wiped away. As for 78's, that program can change the speed if necessary and apply an opposing RIAA curve, but for the 78's I have a simple flat phono preamp (no RIAA) for those. I get phenomenal results with the sound. Just trying to make sure I'm doing everything to the best of my ability. Note: I have some before & after samples at the Diamond Cut web site if you wish to hear some of my work. Thanks everyone.
An opamp based preamp will have no trouble driving any of the attenuators you have and that really is the best way to achieve what you want.
If you want to capture vintage recording and do some restoration of the sound it would be best to start over with equipment designed for the purpose. There is a comprehensive book on the subject and you might start there. Look for the Needle Drop Handbook. A flat response preamp with equalization applied digitally is the way to the highest quality sound capture. As there are many different pre-emphasis curves used, the the flexibility and perfect accuracy digital de-emphasis filtering can't be beat. Some of the common tracking distortions can now be mathematically estimated and removed as well. You will want to get the finest line contact stylus possible to minimize the tracing distortion.
Link to the Stereolab software
https://pspatialaudio.com/index.htm
Link to the Groove Sleuth flat response preamp for use with Stereolab software.
Stereolab distortion reduction requires the signal before RIAA equalization is applied.
Look at the HIFI link
http://www.phaedrus-audio.com/
Descriptions of the Stereolab software versions. Go to link and scroll down the page.
https://www.tokyodawn.net/tdr-simulathe-ref/
https://www.phaedrus-audio.com/phaedrus_stereo_lab.htm
Link to the Stereolab software
https://pspatialaudio.com/index.htm
Link to the Groove Sleuth flat response preamp for use with Stereolab software.
Stereolab distortion reduction requires the signal before RIAA equalization is applied.
Look at the HIFI link
http://www.phaedrus-audio.com/
Descriptions of the Stereolab software versions. Go to link and scroll down the page.
https://www.tokyodawn.net/tdr-simulathe-ref/
https://www.phaedrus-audio.com/phaedrus_stereo_lab.htm
Thanks for the Information. I have been Phaedra Stereo Lab in the past to obtain their bass turnover list of various 78 labels that I compare to some other lists.
I have a set of 6 78 tips I purchased several years ago from KAB for $700. Glad I got them then as the price of that set has doubled. Would very much like to find a few truncated tips somewhere...
I do have a simple but clean flat phono preamp from TracerTech that I have been using with Diamond Cut Audio Restoration Tools for nearly 15 years with great results. It does have all the necessary EQ curves - AES, Columbia LP, EMI, ffrr, NAB, etc. (I'll send you a 100 year old sample if you like as an MP3)
It wouldn't hurt me though to go back again there & look around for different technologies & advancements.
Thanks again though for the info.
I have a set of 6 78 tips I purchased several years ago from KAB for $700. Glad I got them then as the price of that set has doubled. Would very much like to find a few truncated tips somewhere...
I do have a simple but clean flat phono preamp from TracerTech that I have been using with Diamond Cut Audio Restoration Tools for nearly 15 years with great results. It does have all the necessary EQ curves - AES, Columbia LP, EMI, ffrr, NAB, etc. (I'll send you a 100 year old sample if you like as an MP3)
It wouldn't hurt me though to go back again there & look around for different technologies & advancements.
Thanks again though for the info.
I did a deep dive into the distortion mechanisms of vinyl record playback about a year ago and presented the results at a local club meeting. I was seeking to digitize a choir recording made by a local church that I had on a record. Unfortunately the distortion I was hoping to minimize apparently happened during the recording or possibly the cutting of the record as it was totally baked in and not a limitation of my playback system.
I went so far as to purchase the Stereolab software, which required I first acquire an Apple computer. This software claims to be able to reduce the tracking distortion from a "needle drop" aka record playback captured with an accurate flat response phono preamp. I went so far as to model the distortion mechanism in Matlab (Octave freeware) and generate test waveform. Unfortunately the software rejects any of my simple test waveforms, so I have not been able to verify its correct operation. I also coded my own distortion reduction script for Octave but I was not able to converge on a version that worked well with music.
I found the Ortofon test record to be useful in evaluating the distortion and tracking performance of my cartridges and as predicted the line contact stylus was the winner. I made a few poorly organized documents with notes on my flat phono preamp design and distortion reduction efforts. Here are docs and a link to one that was too large to upload. The distortion reduction calculations require filtering the phono cartridge output in a way that produces an estimate of the record groove surface profile.
It would be great to listen to your .mp3. I will message you my email address.
https://docs.google.com/document/d/1xSMBUk3VA-K_1iz0FtEaz1TSOQr2PR5LPY1MFGZpu_U/edit?usp=sharing
I went so far as to purchase the Stereolab software, which required I first acquire an Apple computer. This software claims to be able to reduce the tracking distortion from a "needle drop" aka record playback captured with an accurate flat response phono preamp. I went so far as to model the distortion mechanism in Matlab (Octave freeware) and generate test waveform. Unfortunately the software rejects any of my simple test waveforms, so I have not been able to verify its correct operation. I also coded my own distortion reduction script for Octave but I was not able to converge on a version that worked well with music.
I found the Ortofon test record to be useful in evaluating the distortion and tracking performance of my cartridges and as predicted the line contact stylus was the winner. I made a few poorly organized documents with notes on my flat phono preamp design and distortion reduction efforts. Here are docs and a link to one that was too large to upload. The distortion reduction calculations require filtering the phono cartridge output in a way that produces an estimate of the record groove surface profile.
It would be great to listen to your .mp3. I will message you my email address.
https://docs.google.com/document/d/1xSMBUk3VA-K_1iz0FtEaz1TSOQr2PR5LPY1MFGZpu_U/edit?usp=sharing
I agree with you completely on the use of a fine line diamond tip cartridge. Going with a low output moving coil could improve tracking as well. Unfortunately my flat preamp only handles 47k ohm MM cartridges. I use a PSAudio Phonolink II that I recently modified with some Sparkos chips with a moving coil cart for my LP's. It has a very good passive RIAA +/- 0.5db. It will have to do for those.
I can see you are much more technically into it than I am. I do have a new Test LP from Hi-Fi News. I intend on recording the pink noise section to my computer at 24/192 wit all my different cartridges. I plan on utilizing the full duplex capability of my sound card and play each of the samples with the Diamond Cut program while monitoring the WAV file with a True Audio RTA program. (1/12 octave). I will be able to apply multiple filters in Diamond Cut as it's playing until I come up with a flat response. But my system is in pieces! Waiting for a new double bay slanted rack cabinet....
I do have an older restoration posted at the Diamond Cut web site you may find interesting. I used a Stanton 500 cartridge EQ compensation but believe my sample may be more bass heavy. I intend on redoing this song with some modified procedures. Notice all the bass. In 1926 most purchasers never heard it as most of the public were still using crank up Victrolas. Hope I got the URL right.
https://www.diamondcut.com/Downloads/When The Morning Glories Wake Up In The Morning (before).mp3
I can see you are much more technically into it than I am. I do have a new Test LP from Hi-Fi News. I intend on recording the pink noise section to my computer at 24/192 wit all my different cartridges. I plan on utilizing the full duplex capability of my sound card and play each of the samples with the Diamond Cut program while monitoring the WAV file with a True Audio RTA program. (1/12 octave). I will be able to apply multiple filters in Diamond Cut as it's playing until I come up with a flat response. But my system is in pieces! Waiting for a new double bay slanted rack cabinet....
I do have an older restoration posted at the Diamond Cut web site you may find interesting. I used a Stanton 500 cartridge EQ compensation but believe my sample may be more bass heavy. I intend on redoing this song with some modified procedures. Notice all the bass. In 1926 most purchasers never heard it as most of the public were still using crank up Victrolas. Hope I got the URL right.
https://www.diamondcut.com/Downloads/When The Morning Glories Wake Up In The Morning (before).mp3