Thanks Dave. I'd reloaded XP and couldn't find my copy in my files.planet10 said:
William, if my 12B4A cct doesn't come up OK for you (it should it's really simple and Dave did a good job of it), email me through the forum and I'll send it to you. It's quite easy to play with the op-points too, if you have a lower B+ etc or want a bit less gain. The tubes are cheap too.hihopes said:
There seem to be a couple of you recommending this 12B4A circuit. Am I right in assuming that a fair number of you have actually tried it? How about some "reviews", from happy (or unhappy) users? I really would like some opinions of its sound, even if they are pretty subjective. (After all, the enjoyment of music is a subjective thing, is it not?
Perhaps it would help if I tell you what I am looking for.
Firstly, I am very pleased with the clarity of my system using a passive pre (stepped attenuator). The sound stage stretches back to infinity and there is no grain or grit in the sound. There is the most beautiful integrity of and separation between instruments. Each one has its own complete sound without overlapping or getting mixed with the others. However, as most of you probably know, in passives, there is a lack of dynamics and liveliness. In my case, the bass and high treble also sound a bit lacking.
A friend of mine recently brought over a tube pre he has just finished, and even playing straight from a Marantz SE63 without any external DAC, I was quite amazed at what it did for my system. Life, sparkle, openness, presence - mind blowing bass impact - with complete control! My tongue was hanging out! I was on thempoint of building a solid state pre and I was stopped in my tracks.
But - it is not a very simple design, and it has another side to it that I don't particularly want to introduce into my system. The separation between instruments is blurred by it. At first, I thought it was merely the lowish end source to blame, but I subsequently heard it in his system, with good transport and DAC and picked up the same problem there.
SO - my thought process said - yes, there is much to recommend this pre - but what if I were to build something elegantly simple. Wouldn't I get a purer sound, even if I might have to sacrifice a little of that slam? (Not too much, of course)
In short, champagne sound on a beer budget.
Does this make sense or am I, like the Bangles, only dreaming?
Perhaps it would help if I tell you what I am looking for.
Firstly, I am very pleased with the clarity of my system using a passive pre (stepped attenuator). The sound stage stretches back to infinity and there is no grain or grit in the sound. There is the most beautiful integrity of and separation between instruments. Each one has its own complete sound without overlapping or getting mixed with the others. However, as most of you probably know, in passives, there is a lack of dynamics and liveliness. In my case, the bass and high treble also sound a bit lacking.
A friend of mine recently brought over a tube pre he has just finished, and even playing straight from a Marantz SE63 without any external DAC, I was quite amazed at what it did for my system. Life, sparkle, openness, presence - mind blowing bass impact - with complete control! My tongue was hanging out! I was on thempoint of building a solid state pre and I was stopped in my tracks.
But - it is not a very simple design, and it has another side to it that I don't particularly want to introduce into my system. The separation between instruments is blurred by it. At first, I thought it was merely the lowish end source to blame, but I subsequently heard it in his system, with good transport and DAC and picked up the same problem there.
SO - my thought process said - yes, there is much to recommend this pre - but what if I were to build something elegantly simple. Wouldn't I get a purer sound, even if I might have to sacrifice a little of that slam? (Not too much, of course)
In short, champagne sound on a beer budget.
Does this make sense or am I, like the Bangles, only dreaming?
hihopes said:
Why not something like this?
It 's simple, inexpensive, low gain, and will smoke most garden variety cathode followers.
hihopes said:
How about this: http://diyparadise.com/etude.html
He seems happy with the 12B4
, Essentially ths same circuit, though I do believe a slightly different operating point
I've used mine quite a lot, both SE and differential in all sorts of configurations; CCS, OPT and choke loaded. Superb tube the way I've used it, ie with a very clean passive supply.hihopes said:
I've given up trying to describe the sound of gear, as I've never found it to be possible to convey even the slightest accurate description of what something sounds like to me. There are too many variables, especially the way we all hear individually.
Mine was only removed from system when the S&B transformers were included. But it may go back in as I'm going to go active with the system and use a varation on the 12B4A stage for a buffer in the passive line level xovers.
If you place a good passive at the input of the poweramps, ie minimal lead, and you have plenty of gain and drive from your sources, I've generally not found an active to be better. Most passives, not using transformers, I've found to be compromised by their installation, more than the topology.
The last thing you could say my system was lacking in is slam, full horn loaded from about 30Hz up, so the 12B4A stage won't let you down there if your system is up to it. And it will happily drive most loads without even the thought of cracking a sweat; with a suitable OPT, it makes a nice low power (~1.5W) poweramp.
planet10 said:
~5K
There is a writeup here:
http://www.enjoythemusic.com/magazine/equipment/0902/levinson.htm (Part 1)
http://www.enjoythemusic.com/magazine/equipment/1002/levinson.htm (Part 2)
audiousername is correct that 5k would be the first choice, but a bit lower, say 3k5 would probably work OK too, for a bit more distortion. I used them in PP with some 7k1 Dyna ST35 OPTs and it was very good for a lash together quick test. I used CCS loaded ECC99's to drive iirc.planet10 said:
Thanks for the suggestions. I have looked at the Etude as a possibility, but as I mentioned earlier in the thread, output transformers, chokes etc. are a bit of a problem. I have a transformer builder who can hook me up with just about anything I specify in a basic power transformer, but he has no idea about output transformers and a lot less about chokes. Is/are there differences between output transformers and power transformers? Don't output transformers have serious drawbacks?
I have seen quite a few designs now that look anything from pretty good to pretty amazing, but the one thing the good ones all seem to have in common is GOOD POWER SUPPLIES - some with chokes bigger than their transformers. Have you seen the design with a single 5687 (from Malaysia, I think) - 2 x 30H chokes - an op-amp would probably sound high-end with that PS.
They seem to be able to get the stuff there for next to nothing. My biggest problem is exchange rate. Our currency is currently about 6:1 against the US$, about 8:1 against the Euro and about 11:1 against Sterling. for instance, 1 paper & oil cap would cost me about ZAR200.00 without transport. Decent chokes and output transformers are going to be prohibitive, then there is shipping on top of that. Can one get a really good PS with just CRC filtering? Would it help to take the chokes out of computer power supplies and use them in a PS for a valve pre?
Brett, thanks for e-mailing the schematic. It is crystal clear and totally legible now. I am leaning towards your 12B4 at the moment. Do you (or anyone else) have some suggestions for PS filtering without massive inductors?
I have seen quite a few designs now that look anything from pretty good to pretty amazing, but the one thing the good ones all seem to have in common is GOOD POWER SUPPLIES - some with chokes bigger than their transformers. Have you seen the design with a single 5687 (from Malaysia, I think) - 2 x 30H chokes - an op-amp would probably sound high-end with that PS.
They seem to be able to get the stuff there for next to nothing. My biggest problem is exchange rate. Our currency is currently about 6:1 against the US$, about 8:1 against the Euro and about 11:1 against Sterling. for instance, 1 paper & oil cap would cost me about ZAR200.00 without transport. Decent chokes and output transformers are going to be prohibitive, then there is shipping on top of that. Can one get a really good PS with just CRC filtering? Would it help to take the chokes out of computer power supplies and use them in a PS for a valve pre?
Brett, thanks for e-mailing the schematic. It is crystal clear and totally legible now. I am leaning towards your 12B4 at the moment. Do you (or anyone else) have some suggestions for PS filtering without massive inductors?
One idea that would work well for the supply, would be to design for around 350-400V after the first cap in the supply, then use a CCS (constant current source; cheap and easy) and two VR150 diodes in series forming a shunt regulator to get your 300V B+. Best of all you get more glowing bottles.
I wish I had some way to add a drawing for you.
I wish I had some way to add a drawing for you.
The CCS can the transistor, FET, tube or a hybrid combo. There are quite a few on Gary Pimm's site
Hi,
You could us an IXYS IXCP10M45S ccs on a chip as the current set for the VR shunt regulators that Brett mentioned and kill 2 birds with 1 stone.
Avnet Kopp seams to be the IXYS distributor for RSA.
You could us an IXYS IXCP10M45S ccs on a chip as the current set for the VR shunt regulators that Brett mentioned and kill 2 birds with 1 stone.
Avnet Kopp seams to be the IXYS distributor for RSA.
I'd be interested in knowing which way you went, hihopes. I built the diyparadise simple 5687 as my very first diy project. It sounded great but I had a horrible hum, probably cause I didn't do a good job on layout. Anyway, I am rebuilding it in another chassis with hopes of doing better this time.
Brett - Yeo mentioned that the 12B4A is quite microphonic. Has that been your experience also? I think this would drive me nuts.
I am really looking for a simplistic (but not necessarily overly so) circuit for a line amp with little or unity gain, high linearity, low noise and preferrably balanced in and out. Any ideas?
I'd like to build it as a tube buffer between my DEQX outputs (balanced xlr) and UcD inputs (balanced xlr). I'd like to add just a touch of sweetness to the system, since the DEQX bumped out my tube preamp and the UcDs are nice but a bit too "clean".
Ideally if the circuit was done to unity gain then I wouldn't need to insert similar circuit in front of the woofer amps (<200hz), just the mid and tweeter amps (thus why I wanted simplistic to keep cost down when doing 6 channels). Help??
Brett - Yeo mentioned that the 12B4A is quite microphonic. Has that been your experience also? I think this would drive me nuts.
I am really looking for a simplistic (but not necessarily overly so) circuit for a line amp with little or unity gain, high linearity, low noise and preferrably balanced in and out. Any ideas?
I'd like to build it as a tube buffer between my DEQX outputs (balanced xlr) and UcD inputs (balanced xlr). I'd like to add just a touch of sweetness to the system, since the DEQX bumped out my tube preamp and the UcDs are nice but a bit too "clean".
Ideally if the circuit was done to unity gain then I wouldn't need to insert similar circuit in front of the woofer amps (<200hz), just the mid and tweeter amps (thus why I wanted simplistic to keep cost down when doing 6 channels). Help??
"I am really looking for a simplistic (but not necessarily overly so) circuit for a line amp with little or unity gain, high linearity, low noise and preferrably balanced in and out. Any ideas?"
That's an exact description of my preamp, the Odilon. The whole project is on my website.
cheers,
Joel
http://www.joeltunnah.com
That's an exact description of my preamp, the Odilon. The whole project is on my website.
cheers,
Joel
http://www.joeltunnah.com
hihopes said:
Here is a power supply that shows a CCS followed by a shunt reg.
http://www.raleighaudio.com/hvps_schematic.htm
The supply is a full function supply and all you need is the parts at the top, from the rectifier to the output. The filter capacitance is only 3.6uF so there is lots of ripple - for a purpose. You can read the theory about it here:
http://www.raleighaudio.com/chapter_5.htm
Dave
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