Hi Guys
well i have tried everythingfrom 4 different cartridges (mm and mc) and 2 different head amp topologys as well as stepup transformers.
Its the cornet octal based on Jim Hagermans 6sl7 6sn7 design. The line stage is srpp 6sn7 and it sounds very nice indeed. Cd's currently sound way better than the record side of things.I Suppose my question is ... is it the 6sn/sl7 tubes that are not suitable?
I wonder if i could add some feedback or will that affect riaa?
If i can do feeback then how is it implemented.
I wont post a circuit because its copyright but having said that I downloaded it from here.
Has anyone had any experience with 6sn7's working well for phono.?
Any help will be appreciated
Many thanks
Nick
well i have tried everythingfrom 4 different cartridges (mm and mc) and 2 different head amp topologys as well as stepup transformers.
Its the cornet octal based on Jim Hagermans 6sl7 6sn7 design. The line stage is srpp 6sn7 and it sounds very nice indeed. Cd's currently sound way better than the record side of things.I Suppose my question is ... is it the 6sn/sl7 tubes that are not suitable?
I wonder if i could add some feedback or will that affect riaa?
If i can do feeback then how is it implemented.
I wont post a circuit because its copyright but having said that I downloaded it from here.
Has anyone had any experience with 6sn7's working well for phono.?
Any help will be appreciated
Many thanks
Nick
duderduderini said:
Fatiguing ? Define the problem closer, loss of level, quality etc. In my case can't rule out the pecularities with my own hearing.
Tube fatigue can imply many things, loss emission, B+ problems and so on down to component level.
In the Radiotron handbook there are many down-stream circuits appro for phono using sim tubes for phono. Both 6SN7 and 6SL7 were used in many 1950'-60's front end circuits and are fine time served tubes. Don't blame them.
I'm seeing something similar in my solid state world right now. I just put in a new cartridge and got the alignment better than I probably ever have, and it's too crisp. IMO, the rather old records I'm fooling with probably *are* fatiguing, and sounded better with the edges knocked off. What are you playing? Also, have you built an inverse RIAA box and checked the curve? Hint- nobody will be the wiser if you alter the curve slightly to suit your tastes.
Phono circuits can be prone to radio frequency oscillation. This manifests as Intermodulation distortion - which produces a hard to define high frequency fatiguing quality. Superficially the music sounds fine.
Of course most of the cheaper cartridges are excessively bright sounding and have their own fatigue issues.
Shoog
Of course most of the cheaper cartridges are excessively bright sounding and have their own fatigue issues.
Shoog
SHoog has hit the nail on the head
Shoog bless you for describing it. The cornet octal phono sounds great but i get this hash in my ear and then tinnitus for a day.. its a peculiarity of my ear..it doesnt happen with cd;s movies etc.. I am sure its the phono stage. Itg is particularly apparent on voives in the upper register and lead guitars for instance.
I am running a regulated power supply and again if it were b+ it would manifest in the line stage would it not?
I love the 6sn/sl7 and I am not blaming them or Jims design for my woes.. its just that i cant at least to this point put my finger on it as to why it does it.
So how do you deal with RF oscillation?
Nick
Shoog bless you for describing it. The cornet octal phono sounds great but i get this hash in my ear and then tinnitus for a day.. its a peculiarity of my ear..it doesnt happen with cd;s movies etc.. I am sure its the phono stage. Itg is particularly apparent on voives in the upper register and lead guitars for instance.
I am running a regulated power supply and again if it were b+ it would manifest in the line stage would it not?
I love the 6sn/sl7 and I am not blaming them or Jims design for my woes.. its just that i cant at least to this point put my finger on it as to why it does it.
So how do you deal with RF oscillation?
Nick
If you haven't got grid stopper add them right on the pins. If your anode load is not mounted right on the pin - move it to the pin or add 10R anode stoppers. Screening cans on the input valves are designed to deal with radio interference.
Another potential problem could be transformer/choke ringing. Excessive capacitive filtering can cause this and will result in radio waves been transmitted inside the case. If using SS rectification - snubbers across the diodes, and a small bit of series resistance in line with each diode will help kill switching noise.
Shoog
Another potential problem could be transformer/choke ringing. Excessive capacitive filtering can cause this and will result in radio waves been transmitted inside the case. If using SS rectification - snubbers across the diodes, and a small bit of series resistance in line with each diode will help kill switching noise.
Shoog
will do
Hi Shoog
will do as suggested.
My psu is tube rectified clc then regulated via 6080 12at7 and 5651 outputing to a crc filter. This is a seperate psu to preamp.
I may have used a few to many caps in phono stage however and will check'
If there is no grid stopper in original schematic then I add one
right? What value (same as anode stopper?)
Much appreciated
Nick
Hi Shoog
will do as suggested.
My psu is tube rectified clc then regulated via 6080 12at7 and 5651 outputing to a crc filter. This is a seperate psu to preamp.
I may have used a few to many caps in phono stage however and will check'
If there is no grid stopper in original schematic then I add one
right? What value (same as anode stopper?)
Much appreciated
Nick
I have run into a number of 6SL7 derivatives that IMHO don't sound that good unfortunately, in particular the standard Russian version and the industrial 6188. You might want to do a little tube rolling as I am quite familiar with several of Jim's designs, and this should not be fatiguing to listen to in the least. Cartridge loading if you are using a high output MC cartridge might also be an issue.
Grid stoppers should be in the 220 - 2.2K range for the 6SL7 family, I've not found anode stoppers to be necessary with tubes in this transconductance range.
Is this a Hagtech pcb or something you wired point to point?
This design is quite revealing and choice of coupling caps and equalizer section caps is critical.. Please tell me you are not using mica here. (There are some Russian micas that might be the exception.)
Another thought is the cathode bypass caps if used. I recently designed a new phono stage with D3A in the first stage and used cathode bias as leds weren't practical for the low bias voltage required. (1.2V/ 20mA) I used Black Gates, but needed large values to assure a flat frequency response below 20Hz - in the end I had to shunt the caps with a 5uF low voltage film cap to get rid of a high frequency glare that defied resolution. Cheaper caps (Nichicon Muse) generated audible and scope visible bursts of distortion on dynamic material - and it wasn't bursts of oscillation in the D3A, it turned out to be a d/a related effect, and was harmonically related to the signal applied across the cap - sounded awful.
You can't use negative feedback in this design, and it frankly shouldn't be necessary.
Do you have a scope to check for oscillation issues in your voltage regulator? (I use somewhat similar designs in all of my projects.) Check the pre-amp as well.
Finally depending on arm and table you might want to consider one the current Grado Prestige series cartridges, even the least inexpensive models perform well and are quite sonically inoffensive in a variety of situations.
Grid stoppers should be in the 220 - 2.2K range for the 6SL7 family, I've not found anode stoppers to be necessary with tubes in this transconductance range.
Is this a Hagtech pcb or something you wired point to point?
This design is quite revealing and choice of coupling caps and equalizer section caps is critical.. Please tell me you are not using mica here. (There are some Russian micas that might be the exception.)
Another thought is the cathode bypass caps if used. I recently designed a new phono stage with D3A in the first stage and used cathode bias as leds weren't practical for the low bias voltage required. (1.2V/ 20mA) I used Black Gates, but needed large values to assure a flat frequency response below 20Hz - in the end I had to shunt the caps with a 5uF low voltage film cap to get rid of a high frequency glare that defied resolution. Cheaper caps (Nichicon Muse) generated audible and scope visible bursts of distortion on dynamic material - and it wasn't bursts of oscillation in the D3A, it turned out to be a d/a related effect, and was harmonically related to the signal applied across the cap - sounded awful.
You can't use negative feedback in this design, and it frankly shouldn't be necessary.
Do you have a scope to check for oscillation issues in your voltage regulator? (I use somewhat similar designs in all of my projects.) Check the pre-amp as well.
Finally depending on arm and table you might want to consider one the current Grado Prestige series cartridges, even the least inexpensive models perform well and are quite sonically inoffensive in a variety of situations.
Hi Kevin
Hi
I am running Brimars in all sockets.. nice tube.
No am not using mica.. some are polypropylene made by wima or sangamo oil in paper
Jim has designed in 220 r grid stoppers.
I have just spent 2 hours getting all the resistors close to the pins.
I have point to point wired it, I didnt know you can get pcb's for the octal version of his phono amp.
I have a scope but havent used it. I suppose the fact that the line stage section of my preamp (srpp) sounds so good led me to assume the psu is ok (correct me if I am less than right).
There are no bypass caps.
Lastly i have just ordered an Ortofon MC25FL.. too late for a grado unfortunately.
I will see if the rf detailing that shoog suggested bears any fruit.
I stress again I am v impressed with Jims design. I believe I am getting some form of harmonics/ distortion superimposed. No doubt the scope will show that.
Well its 3am here in Oz and in true Geek tradition I will soldier on and solder on till the sun comes up.
Nick
Hi
I am running Brimars in all sockets.. nice tube.
No am not using mica.. some are polypropylene made by wima or sangamo oil in paper
Jim has designed in 220 r grid stoppers.
I have just spent 2 hours getting all the resistors close to the pins.
I have point to point wired it, I didnt know you can get pcb's for the octal version of his phono amp.
I have a scope but havent used it. I suppose the fact that the line stage section of my preamp (srpp) sounds so good led me to assume the psu is ok (correct me if I am less than right).
There are no bypass caps.
Lastly i have just ordered an Ortofon MC25FL.. too late for a grado unfortunately.
I will see if the rf detailing that shoog suggested bears any fruit.
I stress again I am v impressed with Jims design. I believe I am getting some form of harmonics/ distortion superimposed. No doubt the scope will show that.
Well its 3am here in Oz and in true Geek tradition I will soldier on and solder on till the sun comes up.
Nick
Nick,
Unfortunately you may be wrong. Because the input signal is so small, and the due to the nature of some cartridges any radio pick up/oscillation may constitute a large proportion of the input signal which is been amplified as a whole. In the case of a line amp this is not the case and such artifacts may be swamped and go completely unnoticed.
Again, unfortunately, it may be extremely difficult to scope out a power supply for instability because your not just dealing with voltage - but current as well, and this doesn't show up on a scope. I used to think that simply throwing bigger inductors and caps at a power supply could solve all problems. Recent reading and experience have led me to believe that quite the opposite might be the case. Also - not all regulators sound nice (though i would guess that your tube based implementation probably sounds excellent).
Good hunting.
Shoog
Unfortunately you may be wrong. Because the input signal is so small, and the due to the nature of some cartridges any radio pick up/oscillation may constitute a large proportion of the input signal which is been amplified as a whole. In the case of a line amp this is not the case and such artifacts may be swamped and go completely unnoticed.
Again, unfortunately, it may be extremely difficult to scope out a power supply for instability because your not just dealing with voltage - but current as well, and this doesn't show up on a scope. I used to think that simply throwing bigger inductors and caps at a power supply could solve all problems. Recent reading and experience have led me to believe that quite the opposite might be the case. Also - not all regulators sound nice (though i would guess that your tube based implementation probably sounds excellent).
Good hunting.
Shoog
The more you know the less the better
The header is a quote from Billy Connellys Grandmother or at least that what he said in one show at the opera house that I went to.Having said that it seems all goes a murky grey when dealing with tubes. You learn one thing.. then you find out all to often how much you dont know.... Enough of the tube grown philosophy.
Shoog, the psu is an adaptation of a circuit dubbed the lsdy powersupply that has been modified by a chap.. heres the url if you want to see the article
http://eshop.diyclub.biz/article_info.php?articles_id=3
It is fairly similar to a ciruit published in a HP test instrument manual so i hope that its ok... i mean its quiet enough and i would be at a losss to better it anyway.(unless you wish to share any designs)
I am readying myself to build some 300b monoblocs and i have done some research on the input caps topic. Many suggest no cap but straigh t to an inductor or if you use a clc initially then the first value of c should be like 5uF. Then theres the concept of ppropylene caps rahter than electrolytics..apart from their sheer size, there is little to detract from a ppylene cap.
I might reduce the value of the caps i have in the phono stage from 47uf in nichicon to 22uF in rubycon i have ,47uf caps strapped across them as well at this point....
So where to from here
Any other suggestions? I might give Mr Connellys grandmother a call... maybe she knows
Thanks to all
The header is a quote from Billy Connellys Grandmother or at least that what he said in one show at the opera house that I went to.Having said that it seems all goes a murky grey when dealing with tubes. You learn one thing.. then you find out all to often how much you dont know.... Enough of the tube grown philosophy.
Shoog, the psu is an adaptation of a circuit dubbed the lsdy powersupply that has been modified by a chap.. heres the url if you want to see the article
http://eshop.diyclub.biz/article_info.php?articles_id=3
It is fairly similar to a ciruit published in a HP test instrument manual so i hope that its ok... i mean its quiet enough and i would be at a losss to better it anyway.(unless you wish to share any designs)
I am readying myself to build some 300b monoblocs and i have done some research on the input caps topic. Many suggest no cap but straigh t to an inductor or if you use a clc initially then the first value of c should be like 5uF. Then theres the concept of ppropylene caps rahter than electrolytics..apart from their sheer size, there is little to detract from a ppylene cap.
I might reduce the value of the caps i have in the phono stage from 47uf in nichicon to 22uF in rubycon i have ,47uf caps strapped across them as well at this point....
So where to from here
Any other suggestions? I might give Mr Connellys grandmother a call... maybe she knows
Thanks to all
I think your power supply sounds fine. When I said oversized caps I meant in the 1000uf range.
My guess is that its a simple layout issue. I have my cartridge load resistors and caps mounted on the phono sockets - might be worth a try.
Did you get any improvement with the mods you already performed.
Shoog
My guess is that its a simple layout issue. I have my cartridge load resistors and caps mounted on the phono sockets - might be worth a try.
Did you get any improvement with the mods you already performed.
Shoog
I built the Hagerman Cornet Octal from the circuit diagram a couple of years back and it’s sitting here in front of me. I had a number of phonos laying about a bottlehead seduction and ARC SP3. The Cornet sound best of the three. I even took it to a phonostage shoot out hosted by the local tube audio club and it came in second only to the Artemis Lab PH1. That said I’ve moved on to a concoction of my own and the Cornet is relegated as a loaner to friends.
In my experience the circuit is sensitive to the gain stage tubes and follower (duh!). Other points of pain are: R9, C5 and C8. R7 may also play a role but by then I hit the wall with the Cornet.
My Cornet can sound annoying with too much emphasis in the high frequencies. This situation manifested when I put a Sylvania VT-231 in the follower position. This tube gave the impression of adding detail to the phonostage but on the long run shifted the tone to the treble and added some perceive distortion to loud high frequency passages. I finally settled with a RCA 6SN7GTB black-plate. This tube shifted the tone to the midrange and distort less than the VT. You can also try different 6SL7s. The reason I built the Cornet was that I scored a bunch of 6SL7s at a garage sale. I rolled the tubes until the phonestage gave me a well balanced smooth sound using a Sylvania 6SL7WGT and Tung-Sol 6SL7WGT. You mentioned using BIMAR tubes which I’m sure are good tubes but in my experience 6SN7s are notorious for having different tone and the 6SL7 is a rather squeaky tube.
Another soft spot is R9. You may want to try different resistors here. I found that a Kiwami would soften the tone a bit but the best to date is a mil-spec metal foil resistor I found at a surplus store as having a clean neutral sound. The next component I found helpful to try is C8. If rolling the 6SN7 or 6SL7 does not offer relief try a PIO in this position. I settled on a Russian K40Y9 .47uf paralleled with a Russian K72 Teflon. I found C5 to not be so fussy regarding tone but had an impact regarding distortion. I settled with a K72 Teflon.
Finally my PS is nothing like the one in the circuit diagram. I like to use the bare minimum capacitance in conjunction with a tank circuit to minimize ripple. All electrolytic caps are bypassed with K40s or some sort of PIO for the parts box. I found the PS design played a big role to minimize distortion but less on tone.
Hope this help.
cheers
33dot33rpm
In my experience the circuit is sensitive to the gain stage tubes and follower (duh!). Other points of pain are: R9, C5 and C8. R7 may also play a role but by then I hit the wall with the Cornet.
My Cornet can sound annoying with too much emphasis in the high frequencies. This situation manifested when I put a Sylvania VT-231 in the follower position. This tube gave the impression of adding detail to the phonostage but on the long run shifted the tone to the treble and added some perceive distortion to loud high frequency passages. I finally settled with a RCA 6SN7GTB black-plate. This tube shifted the tone to the midrange and distort less than the VT. You can also try different 6SL7s. The reason I built the Cornet was that I scored a bunch of 6SL7s at a garage sale. I rolled the tubes until the phonestage gave me a well balanced smooth sound using a Sylvania 6SL7WGT and Tung-Sol 6SL7WGT. You mentioned using BIMAR tubes which I’m sure are good tubes but in my experience 6SN7s are notorious for having different tone and the 6SL7 is a rather squeaky tube.
Another soft spot is R9. You may want to try different resistors here. I found that a Kiwami would soften the tone a bit but the best to date is a mil-spec metal foil resistor I found at a surplus store as having a clean neutral sound. The next component I found helpful to try is C8. If rolling the 6SN7 or 6SL7 does not offer relief try a PIO in this position. I settled on a Russian K40Y9 .47uf paralleled with a Russian K72 Teflon. I found C5 to not be so fussy regarding tone but had an impact regarding distortion. I settled with a K72 Teflon.
Finally my PS is nothing like the one in the circuit diagram. I like to use the bare minimum capacitance in conjunction with a tank circuit to minimize ripple. All electrolytic caps are bypassed with K40s or some sort of PIO for the parts box. I found the PS design played a big role to minimize distortion but less on tone.
Hope this help.
cheers
33dot33rpm
Thanks for the info 33dot33rpm
Hi
I will look into this..
I run carbon resistors throughout the phono section... try getting good resistors in australia before banishing me to the corner.
I tired shoogs suggestions.. it did make a subtle but palpable difference.. smoother being one perception..
The thing is I believe one channell sounds really nice whilst the other suffers the unpleasantness....
I still think this phono stage sounds great so i will instigate all the suggestions of 33 dot.
Only one question..
Where does a clueless fellah from australia find these fabled pios and teflon?
Ok Ok a second question whats a tank psu?
I am beggining to think my psu is overkill and perhaps contributing to the problem...
Many thanks to all of you
Nick
Hi
I will look into this..
I run carbon resistors throughout the phono section... try getting good resistors in australia before banishing me to the corner.
I tired shoogs suggestions.. it did make a subtle but palpable difference.. smoother being one perception..
The thing is I believe one channell sounds really nice whilst the other suffers the unpleasantness....
I still think this phono stage sounds great so i will instigate all the suggestions of 33 dot.
Only one question..
Where does a clueless fellah from australia find these fabled pios and teflon?
Ok Ok a second question whats a tank psu?
I am beggining to think my psu is overkill and perhaps contributing to the problem...
Many thanks to all of you
Nick
Tube rolling does help somewhat
i tried some rolling.. found the smoked glass variants did smooth out sound somewhat. Curiously one channel exhibits this problem. I have tried to attend to layout as much as i can.
If anyone has recommendations re resistors I will take them up. As I said Australia is not the place for audiophile anything.. it exists but expensive.
Thanks
i tried some rolling.. found the smoked glass variants did smooth out sound somewhat. Curiously one channel exhibits this problem. I have tried to attend to layout as much as i can.
If anyone has recommendations re resistors I will take them up. As I said Australia is not the place for audiophile anything.. it exists but expensive.
Thanks
resistor noise
I found this document published by Vishay re resistor noise
http://www.vishay.com/doc?49435
It might be of interest to many
Cheers
Nick
I found this document published by Vishay re resistor noise
http://www.vishay.com/doc?49435
It might be of interest to many
Cheers
Nick
Hi Nick,
Well it makes perfect sense to me that the smoked glass tube would make the phono sound smoother!:^) You didn’t mention that fact that one channel sounds good and the other sounds bad. That would indicate some kind of fault in your circuit. Have you tried running just one channel at a time to the same input of your linestage (don’t forget to use the same channel from your source to the phono)? If the same channel is still treble annoying then you can systematically go through the “bad” circuit.
I would do the obvious first. If after rolling the tubes the same channel is still annoying this would be my procedure.
1) Clean and tighten the tube sockets of the channel in question
2) Reheat all solder joints of the bad channel
3) Swap the B+ of the L-R channels. (assuming you are using duel power supply or split and isolated the B+ somewhere up stream)
4) Swap C8 L-R channels.
5) Swap C5 L-R channels
6) Swap R3 L-R channels
7) Swap R5 L-R channels
8) Swap R3 L-R channels
9) Swap R6, R18 L-R channels
10) Keep swapping until the treble problem shifts to the other channel or goes away.
For the Russian capacitors just do ebay and search for “Teflon Capacitor” and K40Y9. I got mine from Alexer1 and KWtubes.
Regarding carbon resistors yes carbon composite do tend to get noisy and drift with time but I have yet to have any noise problems with carbon films. Also note that rule of thumb is to use carbon comps for grid stoppers so go figure.
A tank circuit is to use a choke to resonate @ 120hz (for us American blokes) out of phase with the ripple coming from the rectifier thus reduce the amplitude. This is accomplished by attaching a small capacitor across the choke. Do a web search for tank circuit and you will find some helpful sites to design the circuit. With this setup I only need 200uf total of electrolytic caps to reduce ripple to a value barely detectable on my scope. In my experience too much electrolytic capacitors in the B+ dulls the sound and adds distortion. I don’t like regulated PS because I’m too lazy to design and build them.
As for my final phonostage design I’m using the EF86 family of tubes wired for triode op, passive EQ (gain - eq – gain no follower). The phono lacks gain but is enough for my mm cart. The thing sounds really good and is slated for another shoot out in the near future. I hope it will beat the Artemis PH1.
cheers
33dot33rpm
Well it makes perfect sense to me that the smoked glass tube would make the phono sound smoother!:^) You didn’t mention that fact that one channel sounds good and the other sounds bad. That would indicate some kind of fault in your circuit. Have you tried running just one channel at a time to the same input of your linestage (don’t forget to use the same channel from your source to the phono)? If the same channel is still treble annoying then you can systematically go through the “bad” circuit.
I would do the obvious first. If after rolling the tubes the same channel is still annoying this would be my procedure.
1) Clean and tighten the tube sockets of the channel in question
2) Reheat all solder joints of the bad channel
3) Swap the B+ of the L-R channels. (assuming you are using duel power supply or split and isolated the B+ somewhere up stream)
4) Swap C8 L-R channels.
5) Swap C5 L-R channels
6) Swap R3 L-R channels
7) Swap R5 L-R channels
8) Swap R3 L-R channels
9) Swap R6, R18 L-R channels
10) Keep swapping until the treble problem shifts to the other channel or goes away.
For the Russian capacitors just do ebay and search for “Teflon Capacitor” and K40Y9. I got mine from Alexer1 and KWtubes.
Regarding carbon resistors yes carbon composite do tend to get noisy and drift with time but I have yet to have any noise problems with carbon films. Also note that rule of thumb is to use carbon comps for grid stoppers so go figure.
A tank circuit is to use a choke to resonate @ 120hz (for us American blokes) out of phase with the ripple coming from the rectifier thus reduce the amplitude. This is accomplished by attaching a small capacitor across the choke. Do a web search for tank circuit and you will find some helpful sites to design the circuit. With this setup I only need 200uf total of electrolytic caps to reduce ripple to a value barely detectable on my scope. In my experience too much electrolytic capacitors in the B+ dulls the sound and adds distortion. I don’t like regulated PS because I’m too lazy to design and build them.
As for my final phonostage design I’m using the EF86 family of tubes wired for triode op, passive EQ (gain - eq – gain no follower). The phono lacks gain but is enough for my mm cart. The thing sounds really good and is slated for another shoot out in the near future. I hope it will beat the Artemis PH1.
cheers
33dot33rpm
Tank Circuit
Hi 33 dot
You do mean a parrallel resonant band stop filter tuned to 100Hz? (our supply is 50Hz). Do you deploy any other filtration in the form of clc rc etc?
Thanks
WIll get on to your other suggestions later tonight. I have had a good listen to the phono stage again and I am still not 100% that it only occurs in one chanell (it definitely sounds better on to the other though)but i will go and do the checks you suggested.
Hi 33 dot
You do mean a parrallel resonant band stop filter tuned to 100Hz? (our supply is 50Hz). Do you deploy any other filtration in the form of clc rc etc?
Thanks
WIll get on to your other suggestions later tonight. I have had a good listen to the phono stage again and I am still not 100% that it only occurs in one chanell (it definitely sounds better on to the other though)but i will go and do the checks you suggested.
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