Suggestions sought for tube preamp

I'm thinking about a DIY, stereo, line-level, tube preamp. I not looking for a kit, but I would like more than just a schematic, like: a basic BOM, build instructions, and an active on-line support group/forum. The preamp would replace, and hopefully, be an up-grade for my Mac c-27.

Any ideas, thoughts, experiences, etc. would be very welcome.
 
My thought is that almost all modern domestic audio systems do not need a line level preamp. Exceptions are those with very long interconnects, or poorly engineered sources or amplifiers with unusually high/low (respectively) impedance outputs/inputs or significantly nonlinear impedances (sometimes found in the more expensive 'high end' gear).
 
Phono source: one lomc phono set-up and a good phonostage; doubt if I would ever have any interest in a moving magnet cart, but, if I did, I would use a separate phonostage. Other sources: one sacd/dac player, but expect that there may additional digital sources in the future; one head headphone amp, one tuner. one tape deck/recorder.

Amp is Macintosh mc-2015 (105/channel).

Size: I expect a finished preamp to be approximately 17" x 12" (+/-). All components are in close proximity. I would expect the build cost (high level audio components, nice chassis and hardware, good tubes, etc.) to be in the vicinity of USD 1500-2000. Optional tube upgrades could increase the cost.

Why tubes, I would like to upgrade my current Mcintosh c-27 preamp and would like "tube sound" in my system. If, at some time in the future, I wanted to up-grade, or add amp power, I would likely choose solid state.
 

kaputt

Banned
2011-09-04 10:35 pm
Berlin
Ok. We are getting somewhere. The question of needed gain/attenuation needs to be answered. And also what you refer to as "tube sound".
"Tube sound" comes up regularly but I am not sure what people connect to that. The same tube amplifier can sound distinctly different when let's say a CRCRC filtered anode supply is replaced for a LCLC supply giving the same voltage.
 
My current preamp has two amps: 14db through the volume control and an additional 6 db related to tone control. As any phono gain would be created and controlled through a separate phonostage, I assume the gain requirements would be in around 20 db.

"Tube sound" is something I cannot, at this stage, discuss with any certainty. It is something that I will have to work-at as I research this project.
 

kaputt

Banned
2011-09-04 10:35 pm
Berlin
20dB is a lot of gain for a preamp, but why not. Where is your volume control knob usually positioned? Where does it rest for the maximum volume you would ever use?
If your answer for maximum volume ever needed is "all the way clockwise!" than 20dB of gain is what you need.
 

wdecho

Member
2014-10-28 11:45 am
@ kaputt - doubt if I need 20 dB; I'm not close to tapping the gain limit of my c-27; but don't yet have a good feel for an optimum level - time will tell. But, it's certainly better to have too much rather than too little power.

@ wdecho - thanks for the leads, I'll digest the information and may have some follow-up.

@ mcandar - I'll certainly check into the kits that you suggest. My experience with kits has been that it's a little like "Paint-by-numbers." You get a bag of components, solder them on a pcb, and hope for the best. I just finished a DIY, JFET phonostage where I sourced virtually all the components, and tested and matched all critical pieces; Also, I was able to selected peripherals like coupling caps. The entire project, from research to completion, took over six months; and I enjoyed the involvement, learned a lot, and ended up with a very nice phonostage. Certainly better than I could have bought for the same money.

I appreciate all the thoughts.
 
@ mcandar - I'll certainly check into the kits that you suggest. My experience with kits has been that it's a little like "Paint-by-numbers." You get a bag of components, solder them on a pcb, and hope for the best. I just finished a DIY, JFET phonostage where I sourced virtually all the components, and tested and matched all critical pieces; Also, I was able to selected peripherals like coupling caps. The entire project, from research to completion, took over six months; and I enjoyed the involvement, learned a lot, and ended up with a very nice phonostage. Certainly better than I could have bought for the same money.

I totally understand as i much prefer to build my own. I can highly recommend a 4P1L preamp, i built one to drive my F4 amplifier and couldn't be happier with it. Its loosely based on the siberian gen 3 in that its filament biased using Rod Coleman regulators, but i used constant current plate loads and a capacitor coupled output on mine.

Some info here http://www.bartola.co.uk/valves/dht-pre-amplifier/siberian-gen-3-4p1l-pre-amplifier/ and here http://www.diyaudio.com/forums/tubes-valves/190857-4p1l-dht-line-stage.html
 

kaputt

Banned
2011-09-04 10:35 pm
Berlin
@ kaputt - But, it's certainly better to have too much rather than too little power.

I don't see it as that simple. Tubes with lower mu most often have lower Rp which makes it possible to use transformer outputs. Personally I don't want to use coupling capacitors so for me that is important. For you it might not be an issue. Also with low Rp tubes you can use an autoformer for volume control at the output. This might also not be an issue for you.
So from that perspective it doesn't make sense to ME (and possibly only me) to build a preamp with 40dB of gain and attenuate with a potentiometer by 48dB and wreck sound with that filter created there and an output capacitor.

As always, just my opinion and there are many different ways to get happy.
(And it's not about power but gain. And you want a low output impedance.)
 
I totally understand as i much prefer to build my own. I can highly recommend a 4P1L preamp, i built one to drive my F4 amplifier and couldn't be happier with it. Its loosely based on the siberian gen 3 in that its filament biased using Rod Coleman regulators, but i used constant current plate loads and a capacitor coupled output on mine.

Some info here http://www.bartola.co.uk/valves/dht-pre-amplifier/siberian-gen-3-4p1l-pre-amplifier/ and here http://www.diyaudio.com/forums/tubes-valves/190857-4p1l-dht-line-stage.html

This looks very interesting. Thanks.