Since I wish to include a phono preamp stage as well as an attenuator I believe that the unit will have to be active. My last experience in this area was a Dyna Pas-3 but I do not need switchable inputs, just a phono- in and one "aux" input for the CD player. Since cable length may be an issue I thought of a cathode follower output, so I am picturing two stages for the unit.
Pete
Pete
Hi,
Pete...what if I suggested something I concocted myself?
You can cater for MM, MC cartridges...the volctl anyway you like it, and the aux is a follower that would drive anything bar a dead short?
Heck, there's even a choice between a passive or active RIAA and if you absolutely dislike the 12AX7As you can use 6SL7s instead..?
The thing is ...it does not come cheap, though.
MY MODEST ATTEMPT
Sorry about the self promotion...just seems like the ticket for you...
Cheers,
Pete...what if I suggested something I concocted myself?
You can cater for MM, MC cartridges...the volctl anyway you like it, and the aux is a follower that would drive anything bar a dead short?
Heck, there's even a choice between a passive or active RIAA and if you absolutely dislike the 12AX7As you can use 6SL7s instead..?
The thing is ...it does not come cheap, though.
MY MODEST ATTEMPT
Sorry about the self promotion...just seems like the ticket for you...
Cheers,
Does the ST70 have enough gain for you with your line level sources, eg CDP, DVDP VCR etc?
If it does, then I'd combine the other suggestions, thus;
- make a small enclosure with a selector switch then a volume control and place it beside/under the ST70. Have the selector switch and pots at the rear of the enclosure close to the sockets. Use extension shafts and couplers (try Welborne). This keeps the capacitance after the volume control to a minimum and gets rid of most of the adverse effects of a passive pre.
- build a good phono stage and place it next to the TT. Make sure it can drive the length of cable you require and has about enough gain to match the levels of the line sources. The easy way to calc this is to take the nominal cartridge output level and divide it into 325mV, which is approx the average level of a CDP.
eg: .325/300uV = 1083
20*log(1083) = 60.65dB
This is how I've set up my system with my TT's about 6m to the side of the system.
If you do need gain or have impedance problems (not likely), then build something active.
If you're an experienced builder, I'd suggest building this.
You'll be very hard pressed to better it. Replace the volume control with 50k resistors if you use the passive preamp option outlined above. It's not really that hard or expensive to build and whilst the superreg is great, it's not neccessary. A good passive supply will work fine.
I will wind up with a SET amp so the quality of the preamp will be critical. Your thoughts please.
Don't automatically assume an amp is better because it's a SET. There are a number of PP designs that walk all over every set I've ever heard, top, bottom and the mids. Try it first.
If it does, then I'd combine the other suggestions, thus;
- make a small enclosure with a selector switch then a volume control and place it beside/under the ST70. Have the selector switch and pots at the rear of the enclosure close to the sockets. Use extension shafts and couplers (try Welborne). This keeps the capacitance after the volume control to a minimum and gets rid of most of the adverse effects of a passive pre.
- build a good phono stage and place it next to the TT. Make sure it can drive the length of cable you require and has about enough gain to match the levels of the line sources. The easy way to calc this is to take the nominal cartridge output level and divide it into 325mV, which is approx the average level of a CDP.
eg: .325/300uV = 1083
20*log(1083) = 60.65dB
This is how I've set up my system with my TT's about 6m to the side of the system.
If you do need gain or have impedance problems (not likely), then build something active.
If you're an experienced builder, I'd suggest building this.
You'll be very hard pressed to better it. Replace the volume control with 50k resistors if you use the passive preamp option outlined above. It's not really that hard or expensive to build and whilst the superreg is great, it's not neccessary. A good passive supply will work fine.
I will wind up with a SET amp so the quality of the preamp will be critical. Your thoughts please.
Don't automatically assume an amp is better because it's a SET. There are a number of PP designs that walk all over every set I've ever heard, top, bottom and the mids. Try it first.
Brett; thank you for the reply! The St-70 does indeed have the gain to drive directly from a CD player even though it is Triode wired, it uses a hand wired version of Triode Electric's upgrade circuit and has no trouble driving my inefficient Satellite units. I will certainly try your suggestion. Thanks also for the Wright Schematic, as I said to Frank, it takes time for me to digest so response will take awhile. I understand your comment re- SET Amps and am certain you are right. Lynn OLson certainly agreed when he designed his Amity amps with PP 2A3's. As i stated in an earlier thread, Jack Eliano's DRD amp interested me, but that project is aways upstream so there is time to research.
Will keep you posted as to progress.
Pete
Will keep you posted as to progress.
Pete
Peter Menting said:
I would suggest a passive "preamp" like others have done - you could add a cathode follower or plate follower output if you need a lower output impedance. But I don't think that should be nescessary if the preamp and power amp are placed close to eachother.
For the phono preamp I like this circuit: http://www.geocities.com/bobdanielak/phono.html
Best regards,
Mikkel C. Simonsen
Brett said:
What do you think about this layout capacitance and adverse effect wise: http://stiftsbogtrykkeriet.dk/~mcs/Test-50.gif
The actual size is 10*16cm. I have just built that board to replace an input selector only box.
Best regards,
Mikkel C. Simonsen
I've just taken a couple of pictures of my new "passive pre" - it looks nice to me ;-)
http://stiftsbogtrykkeriet.dk/~mcs/Remote3/
No tubes visible - they are hiding in the phono stage and power amp
Best regards,
Mikkel C. Simonsen
http://stiftsbogtrykkeriet.dk/~mcs/Remote3/
No tubes visible - they are hiding in the phono stage and power amp
Best regards,
Mikkel C. Simonsen
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