One last question: can anyone suggest a step-up transformer to use on the input that adds some gain? 6dB is fine, but 12dB would be better (and even a bit more would be fine.) Also, cheap would be good as I am just experimenting.
Well, mine is finally complete and up and running, and though it's early days yet, I'm very pleased. I must admit, I was half expecting a "nice" valve sound, but no, it's accurate and defined. The amp has a very low noise floor, when I was first experimenting I heard a small buzz that I've never noticed before, only audible with the volume up full. After checking, I found it was coming from my source, and I'd never noticed it before. Without getting into magazine style hyperbole, all I will say is that this is a very good pre, and I recommend it to anyone.
Attachments
The whole magazine-reviewer thing puzzles me. A preamp is best when it does... nothing. How can one describe that? When I hook my source directly to my power amp, I don't suddenly hear all those wonderful things that reviewers find in expensive preamps. The best I can hope for is a sound that is not audibly different that that direct connection. It's up to the musicians to create the magic, not the preamp!
The reduced noise floor does seem to have some sonic merit. Getting the blaps and buzzes out of my system (where this preamp really helped) made a very worthwhile difference.
The reduced noise floor does seem to have some sonic merit. Getting the blaps and buzzes out of my system (where this preamp really helped) made a very worthwhile difference.
Exactly. I was just listening to a live set played in the studio at BBC 6Music, and I thought the amp had gone wrong, but I was hearing a very, very low level buzz from an unplugged guitar amp. This truly is a good line stage, adds nothing, and takes nothing away. There might be something in these valve things after all! 🙂
well i hope you people don't mind "slumming"a bit, i'd like to share my "dumbed down" version of the unity gain linestage inspired by sys excellent project. i like it alot. i also plan on trying some of the regulation features in the future. preamp is set up to ultimatley accommodate 2 more of the little 2 channel modules for 6 channels total, for possible home theater use.
http://i27.photobucket.com/albums/c161/selfwilly/DCP_0004_0006.jpg
http://i27.photobucket.com/albums/c161/selfwilly/DCP_0003_0008.jpg
http://i27.photobucket.com/albums/c161/selfwilly/DCP_0001_0016.jpg
it's a very basic version without all the regulation or the input tranny, but i do believe it accomplished many of the goals of low(very! just about dead silent with high sensitivity amps and 100db horns)) noise, and excellent sound with no gain. this thing will drive very long cables with little or no sonic compromise.
i constructed the ps(outboard) and preamp using odds and ends around my work space. ps tranny is a old allied 125-0-125 job wired full wave netting about 105 b+ after 3 stages of rc filtering. the box is a rs 5$ job drilled for cooling it doesn't need and sprayed black "wrinkle"
i mounted a tube socket(modified standard tab to a pc mount!) to a perfboard and both channels and ccs(thanks for help sy!) are point to point wired completley on it, making a neat little module.
one note-after some back and forth comparison, i think that it sounds a little better with ac filaments-of course AFTER i had laid out and built the ps with a dc filament module! even after this change it was quiet so i left it ac.
sorry for the thread crash, i like the project and felt inspired to post! even "dumbed down" it's a great sounding little pre.
http://i27.photobucket.com/albums/c161/selfwilly/DCP_0004_0006.jpg
http://i27.photobucket.com/albums/c161/selfwilly/DCP_0003_0008.jpg
http://i27.photobucket.com/albums/c161/selfwilly/DCP_0001_0016.jpg
it's a very basic version without all the regulation or the input tranny, but i do believe it accomplished many of the goals of low(very! just about dead silent with high sensitivity amps and 100db horns)) noise, and excellent sound with no gain. this thing will drive very long cables with little or no sonic compromise.
i constructed the ps(outboard) and preamp using odds and ends around my work space. ps tranny is a old allied 125-0-125 job wired full wave netting about 105 b+ after 3 stages of rc filtering. the box is a rs 5$ job drilled for cooling it doesn't need and sprayed black "wrinkle"
i mounted a tube socket(modified standard tab to a pc mount!) to a perfboard and both channels and ccs(thanks for help sy!) are point to point wired completley on it, making a neat little module.
one note-after some back and forth comparison, i think that it sounds a little better with ac filaments-of course AFTER i had laid out and built the ps with a dc filament module! even after this change it was quiet so i left it ac.
sorry for the thread crash, i like the project and felt inspired to post! even "dumbed down" it's a great sounding little pre.
No thread crash at all, I tried very hard to make things clear enough that people could riff on the basic design without going in blind. Thanks for sharing your version!
i have a question concerning the regulation, particularly the b+. is there a dramatic sonic advantage to be realised in implimenting it? i have been hitting the books and do plan on trying it out, but if my locales domestic electricity supply is very stable to begin with, is there really much benefit? or is the regulation really meant to address inherent instabilities within the preamp ps?
it seems to me(i'm no doubt off the mark!) that the ccs itself would have a stabilising effect, and in my own current measurements show very only tiny changes over periods of like 5-10mins
i don't doubt that the scheme is better, but would like your opinion on obvious and noticable sonic benefit.
it seems to me(i'm no doubt off the mark!) that the ccs itself would have a stabilising effect, and in my own current measurements show very only tiny changes over periods of like 5-10mins
i don't doubt that the scheme is better, but would like your opinion on obvious and noticable sonic benefit.
I think the RCRC filter I showed works fine. Regulation is a nice way of locking things in, but really, it doesn't matter if the plate voltage is 90 or 100. Or, for that matter, 80 or 110...
Schematics are gone. I think they were hosted by Eddy. Is it possible to see them again, or to receive a copy by email?
Thanks in advance.
SB
Thanks in advance.
SB
There is a version of the article, complete with schematics, here:
Compromised URL removed by Moderation
(1.7M pdf download)
Compromised URL removed by Moderation(1.7M pdf download)
Last edited by a moderator:
A little off topic, but the picture off the old iron ring on the front cover of the article looks like it was taken at the old forts on the Marin highlands outside of San Francisco... I have a photo of that ring too, taken in slanting afternoon sunlight.
Here a list of tube (ECC88) I can get for this project from a local guy. Anything worth buying?
Any comments appreciated.
Thanks.
Any comments appreciated.
Thanks.
The Jensen JT11-P1 is available at 79$ single quantity at: www.markertek.com Seem to be a very good price.
I've got all kinds of exotic ECC88s. I found that, within reason, it doesn't matter much which you use. The ones I have had in for the past year cost me about $6.50 each, FWIW. No better or worse than my fancy NOS Bugle Boys, Mullards, CCa...
$79 is good. Ckeck out the Cinemags, though- I think they're still a chunk cheaper and seem to be about identical in performance.
$79 is good. Ckeck out the Cinemags, though- I think they're still a chunk cheaper and seem to be about identical in performance.
Thanks SY for the comments on tube. I'll buy some new tubes then. Can I buy just 2 transfo from Cinemag or do they have a minimum order?
No time to fix the links yet? thanks for your work.
No time to fix the links yet? thanks for your work.
AE, any time now... as soon as I can have an hour at home when my 7 year old isn't demanding something.😀
Here. I put together a detailled schematic of the power supplies with parts information. Take note that some part of this schematic are from me not SY, but I'm using his design.
For example I added a GND loop breaker resistor, a cap accros the main power switch, an EMI filter. I'll also use a delay to start the HV after the heaters started to work, even if it is a low HV supply. Two leds, one is power-on, the other to indicate that the HV is turn On. I may use a two colors led for that and modify the circuit a little bit.
It may be of some use for some members.
For example I added a GND loop breaker resistor, a cap accros the main power switch, an EMI filter. I'll also use a delay to start the HV after the heaters started to work, even if it is a low HV supply. Two leds, one is power-on, the other to indicate that the HV is turn On. I may use a two colors led for that and modify the circuit a little bit.
It may be of some use for some members.
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