My turntable will be arriving shortly, and i need to build a phono stage. ( preferably tube )
I really enjoyed building the Bottlehead foreplay, and was satisfied with the results...so i was wondering if anyone had any listening experience with the Bottlehead Seduction?
Does anyone have the schematic on-hand?
-Maz
I really enjoyed building the Bottlehead foreplay, and was satisfied with the results...so i was wondering if anyone had any listening experience with the Bottlehead Seduction?
Does anyone have the schematic on-hand?
-Maz
Well, then let me ask this question :
I'm considering building either the Seduction, pictured here :
http://www.bottlehead.com/et/adobespc/Seduction/seduction.htm
which costs $250 for the complete kit and uses 1 6DJ8 per channel ( tubes included in price ). It's PTP wiring, of course.
vs.
The Hagerman Cornet, pictured here :
http://www.hagtech.com/cornet.html
which i estimate to cost me $205.00 and will require slightly more building ( cutting the chassis, etc ) and which uses 2 12AX7 (ECC83), 1 x 12AU7 (ECC82) , and 1 x 5Y3GT. All on a PCB.
(tubes not included, but i have all of them)
Which would you do?
-Maz
I'm considering building either the Seduction, pictured here :
http://www.bottlehead.com/et/adobespc/Seduction/seduction.htm
which costs $250 for the complete kit and uses 1 6DJ8 per channel ( tubes included in price ). It's PTP wiring, of course.
vs.
The Hagerman Cornet, pictured here :
http://www.hagtech.com/cornet.html
which i estimate to cost me $205.00 and will require slightly more building ( cutting the chassis, etc ) and which uses 2 12AX7 (ECC83), 1 x 12AU7 (ECC82) , and 1 x 5Y3GT. All on a PCB.
(tubes not included, but i have all of them)
Which would you do?
-Maz
Forget the Hagerman,as you should forget every RIAA preamp using those unhappy ECC 83 and equivalents!
Does anyone out there remembers the fact that ECC 83 rolls off sharply at 31 KHz?!? ....meaning that when the whole beauty and charm begins (I'm talking of upper harmonics and transients contained by LP's),here it comes this...this LO-Fi tube and ruins all?!?
With a ECC 88 you're happy all the way ,but you'll have to give it the proper "food" (fancy HT supply!) and,maybe,trying some different types,till you reach Nirvana....
Does anyone out there remembers the fact that ECC 83 rolls off sharply at 31 KHz?!? ....meaning that when the whole beauty and charm begins (I'm talking of upper harmonics and transients contained by LP's),here it comes this...this LO-Fi tube and ruins all?!?
With a ECC 88 you're happy all the way ,but you'll have to give it the proper "food" (fancy HT supply!) and,maybe,trying some different types,till you reach Nirvana....
I appreciate both of your input.
Your points are well made, pedroskova. Costmetically though, it doesnt matter to me. I will build a uniform chassis type in the future, but for now i want the goods. Don't care much about support, as you guys are my free tech support
I'm not sure what to think about CCS loading. I have heard statements that sound like "gives it a more modern sound, vs a vintage sound" ...and i'm not sure that's what i want.
Why isnt every tube amp CCS loaded?
At any rate, i'm leaning towards the cornet, and i'm not sure why. Partly because it takes bottlehead 6 weeks to ship something out. Partly because i have some NOS tubes it uses that i want to put to use. Partly because i've never done a PCB layout..soldering...etc.
Partly because i want to actually construct a chassis myself, with punching, drilling, mounting. Also, its $50 cheaper according to my calculator and i can order the parts as i have the cash...as opposed to the $250 upfront from bottlehead.
Seduction would be way easier, though.
I would like to hear why the Cornet isn't particularly interesting, though...and also my question above about CCS loading.
-Maz
Your points are well made, pedroskova. Costmetically though, it doesnt matter to me. I will build a uniform chassis type in the future, but for now i want the goods. Don't care much about support, as you guys are my free tech support
I'm not sure what to think about CCS loading. I have heard statements that sound like "gives it a more modern sound, vs a vintage sound" ...and i'm not sure that's what i want.
Why isnt every tube amp CCS loaded?
At any rate, i'm leaning towards the cornet, and i'm not sure why. Partly because it takes bottlehead 6 weeks to ship something out. Partly because i have some NOS tubes it uses that i want to put to use. Partly because i've never done a PCB layout..soldering...etc.
Partly because i want to actually construct a chassis myself, with punching, drilling, mounting. Also, its $50 cheaper according to my calculator and i can order the parts as i have the cash...as opposed to the $250 upfront from bottlehead.
Seduction would be way easier, though.
I would like to hear why the Cornet isn't particularly interesting, though...and also my question above about CCS loading.
-Maz
I said "impressive," not "interesting." Anyway, I'm unimpressed for a few reasons:
1. 12AX7s. Not a great tube in the first hole for reasons of noise and bandwidth.
2. 12AU7 CF. There are much better tubes for that application. Transconductance is everything.
3. Passive EQ. Hey, I use passive in my own preamps, but the particular way this is implemented here will assure you that the EQ will drift out of spec as the tubes age. And will need retrimming each time the tubes are replaced if you want to maintain EQ accuracy.
But these are pretty minor quibbles. And the way this is set up, a CCS will definitely cause the EQ to be off-spec. If you retrim, the sensitivity of EQ to tube parameters will be even worse. And CCS will reduce the bandwidth.
1. 12AX7s. Not a great tube in the first hole for reasons of noise and bandwidth.
2. 12AU7 CF. There are much better tubes for that application. Transconductance is everything.
3. Passive EQ. Hey, I use passive in my own preamps, but the particular way this is implemented here will assure you that the EQ will drift out of spec as the tubes age. And will need retrimming each time the tubes are replaced if you want to maintain EQ accuracy.
But these are pretty minor quibbles. And the way this is set up, a CCS will definitely cause the EQ to be off-spec. If you retrim, the sensitivity of EQ to tube parameters will be even worse. And CCS will reduce the bandwidth.
Voltsecond ccs'ed the seduction(his own design) and remarked that the change was huge and all for the better. Mr. Joppa designed the RIAA network to accept the ccs with no changes(the riaa curve is barely effected). IMO - if you want to build a chassis, build one that accepts both the foreplay and the seduction circuits, with a second chassis that houses the two separate PSU's. Best of both worlds.
CASCODE
If I were gonna build a phono preamp I would build somthing like this http://thunderstoneaudio.nav.to/
The main thing is a nice FET cascode with a high gm tube.
Robert Morin
If I were gonna build a phono preamp I would build somthing like this http://thunderstoneaudio.nav.to/
The main thing is a nice FET cascode with a high gm tube.
Robert Morin
Goes To Show...
Hi,
Everyones' demands and expectations are different of course but...if you care about vinyl a correct RIAA correction (no pun intended) is first on your list.
A correction that is going to deviate from that norm whenever the tubes age or when you use a different brand is just not cutting it in my book.
And, having to trim filter caps and Rs in that department requires more knowledge than the average DIY posesses let alone let alone the assumption of them having a decent inverse RIAA network.
CCS will reduce the bandwidth noticeably on a 12AX7A input tube
for the simple reason that it optimises gain.
Nothing ever comes free and tacking on a CCS on a phono preamp that was not designed for it is definitely going to mess up the deviation from RIAA correction.
If the guys at bottlehead haven't realised this yet then I question their ability as designers.
While I agree that there are better tubes out there, a manufacturer, even only just for a kit or two, is rather restricted in his choices.
If and when the operating points + the RIAA correction are chosen carefuly neither noise floor nor bandwidth are limited at all.
Let's not forget that this RIAA filter is there to reduce highs and boost bass so if we obtain a 30KHz+ open loop here, we're O.K. when using some active EQ.
For passive EQ filters a tube such as the wideband 6DJ8 may be a better choice.
I'm not saying it's easier to use a 12AX7A but hardly any more difficult than taming the equally silly 6DJ8 in this application.
Meaning that both need a thorough understanding of their idiosyncracies to sound fine.
:cool
Cheers,
Hi,
Everyones' demands and expectations are different of course but...if you care about vinyl a correct RIAA correction (no pun intended) is first on your list.
A correction that is going to deviate from that norm whenever the tubes age or when you use a different brand is just not cutting it in my book.
And, having to trim filter caps and Rs in that department requires more knowledge than the average DIY posesses let alone let alone the assumption of them having a decent inverse RIAA network.
CCS will reduce the bandwidth noticeably on a 12AX7A input tube
for the simple reason that it optimises gain.
Nothing ever comes free and tacking on a CCS on a phono preamp that was not designed for it is definitely going to mess up the deviation from RIAA correction.
If the guys at bottlehead haven't realised this yet then I question their ability as designers.
While I agree that there are better tubes out there, a manufacturer, even only just for a kit or two, is rather restricted in his choices.
If and when the operating points + the RIAA correction are chosen carefuly neither noise floor nor bandwidth are limited at all.
Let's not forget that this RIAA filter is there to reduce highs and boost bass so if we obtain a 30KHz+ open loop here, we're O.K. when using some active EQ.
For passive EQ filters a tube such as the wideband 6DJ8 may be a better choice.
I'm not saying it's easier to use a 12AX7A but hardly any more difficult than taming the equally silly 6DJ8 in this application.
Meaning that both need a thorough understanding of their idiosyncracies to sound fine.
:cool
Cheers,
fdegrove said:
pedroskova said:
I'm confused. Are the two statements talking about different things? If not, then it looks like the RIAA circuit was designed keeping a future CCS in mind (assuming it is possible to design that way), right? Just trying to understand if the two of you are talking about the same thing or not.
pedroskova said:
I'm confused. Are the two statements talking about different things? If not, then it looks like the RIAA circuit was designed keeping a future CCS in mind (assuming it is possible to design that way), right? Just trying to understand if the two of you are talking about the same thing or not.
CONFUSING.
Hi,
No, but how can you keep a correct RIAA EQ and design for the next thing?
What they meant is that to them at least the addition of a CCS does not upset the RIAA correction too much.
Bottom line is, how much deviation do you accept as a user?
Me, I'd rather keep it as close as possible to what was used at the recording process.
Which is what I hinted at when I said:
Hope that clarifies it,
Hi,
No, but how can you keep a correct RIAA EQ and design for the next thing?
What they meant is that to them at least the addition of a CCS does not upset the RIAA correction too much.
Bottom line is, how much deviation do you accept as a user?
Me, I'd rather keep it as close as possible to what was used at the recording process.
Which is what I hinted at when I said:
Hope that clarifies it,
For a get-started circuit, I'd drop the idea of trying to do anything fancy. There's plenty of time for that later on. I'm very happy with my passive-eq tube-FET hybrid circuit with DC servo'ed output, but I wouldn't recomend it to a novice builder, especially because it uses such hard-to-get tubes.
Start simple. Build one of the many PAS-3 variants out there. You're limited to 12AX7s, but feedback EQ is going to be much less dependent on tube parameters. And they sound just fine if you take some care in parts choice (that doesn't mean fashion parts!) and construction.
One step up in fanciness is Joe Curcio's circuits, with which people have had excellent success.
Start simple. Build one of the many PAS-3 variants out there. You're limited to 12AX7s, but feedback EQ is going to be much less dependent on tube parameters. And they sound just fine if you take some care in parts choice (that doesn't mean fashion parts!) and construction.
One step up in fanciness is Joe Curcio's circuits, with which people have had excellent success.
PHONO MADNESS OR CULT STATUS?
Hi,
If Mr.Curcio wants to relive his GA days?
Are those schems public domain?
Anyway, the way I look at those circuits is that they're very well implemented and benefit from very good PSU design.
No doubt in my mind that Mr.Curcio agrees on the importance of PSU design even in the smallest of corners (so people think).
For those still in doubt, I strongly adhere to the philosophy that any circuit is only as good as its' PSU.
Cheers,
/regging the revs.
Hi,
If Mr.Curcio wants to relive his GA days?
Are those schems public domain?
Anyway, the way I look at those circuits is that they're very well implemented and benefit from very good PSU design.
No doubt in my mind that Mr.Curcio agrees on the importance of PSU design even in the smallest of corners (so people think).
For those still in doubt, I strongly adhere to the philosophy that any circuit is only as good as its' PSU.
Cheers,
/regging the revs.
Interesting that you quoted my statement up to a point but left out the next question I asked Here's what I said:
So what you're saying is that it's not possible to build such a circuit. Or, it is, but then the compromise one has to settle for is reduced RIAA accuracy. Thanks, that is the information I was looking for.
Here's what I said:So what you're saying is that it's not possible to build such a circuit. Or, it is, but then the compromise one has to settle for is reduced RIAA accuracy. Thanks, that is the information I was looking for.
When you change to a CCS, you change the source impedance and bandwidth of the stage. If the load is the passive EQ, the EQ will change. The only way to avoid this with a passive EQ is to buffer the driving stage, retrim the EQ to account for the changed source Z and bandwidth, or chuck the passive circuit and go for feedback EQ. As you might gather, I'm pretty lukewarm on retrofitting a CCS. It will not benefit a properly designed circuit.
I would agree in principle with Frank- this is a low level stage with lousy PSRR- noise and stability of the power supply rails are critical. Low noise and accurate EQ are the sines qua non of a good phono stage.
I would agree in principle with Frank- this is a low level stage with lousy PSRR- noise and stability of the power supply rails are critical. Low noise and accurate EQ are the sines qua non of a good phono stage.
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