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This prototype I believe, is the first Directly Coupled 6AH4GT Single Ended two stage power amp ever built in the history of mankind, at least to my knowledge.I am trying for short wire lengths, and a good neat lay out. The RCA Jack to driver grid wiring is Cardas 19 AWG Ag, doubled-up and under two inches, and the direct couple is the same Ag wire, triple-braided and under three inches.
Amp features a Dennis Fraker LSES ( low stored energy ) power supply. The total DCR from the rectifier tube, through two series chokes, at C2, measures only 19.7 Ohms. Three chokes are configured in a "Y", with an L2-left and an L2 right. All film caps in the supply. Ground buss is 9 AWG, copper and silver.
Having fun, need to wire-in the output transformers, AC hook up ( fuse, thermistor, AC cord, ON-OFF switches ) and it will fire-up soon. Fun to do. I never will breadboard, just design it and build.
Jeff Medwin
Edits: 10/15/14 10/15/14Follow Ups:
Jeff, I for one hope it the sound makes you happy (not me, but you). This thread on the other hand has made my week :)
No binding posts?
Are those terminal blocks better?
Looks interesting so far.
Let us know how it turns out after you get it fired up.
DT,
Edison Price posts are no longer available, the best sounding part of this type. Can use Cardas today, not as good, at a high cost.
Salectric, perhaps the world's ultimate parts critiquer and tweaker, tells me, his favorite is to use the Cardas post, not to put the signal through, but to hold two ring ( or fork ) terminals together, one on another, tightly screwed down to each other.
In that case, why run a long secondary wire under the chassis and pass the entire signal THROUGH a Cardas post??
Why not keep the secondary leads short, always a positive with a SE amp, and terminate to a good terminal block !???
I am real picky about absolute phase, despite what a few may THINK, and so, this arrangement is "right there" on the top of the chassis, with plenty of room for me to unambiguously swap speaker leads to get to hear it correctly as far as being in absolute pahse.
I like this arrangement in theory. It is the first time I am trying it out in practice. I will use XLO brand 1/4 inch fork jacks ( Percy ) as speaker terminations, and a 3/8ths inch socket wrench, to swap phase on speaker leads. Terminals are 10-32nds, 3/4 inch spaced, and I will use 10-32nds brass nuts.
Why not ???
Jeff Medwin
Thanks for the info about the wire upgrade for Altec.
Ordered some this afternoon. Avoided any dark colored wire jackets.
Steve said it would be a major upgrade over my current wires.
If DF likes this wire, I think it will be pretty good on the 811Bees.
Are the OPTs with a single silver secondary or multi tapped?
Hi GEO,Will have to check, sourced from Lowes, Electrical Department, look for
door bell transformers, and best of all ( makes the amp ) they are single tap output transformers.Hey, it doesn't matter much when all else is good and on the money, honey.
Got the AC cord, fuse, and thermistor in this afternoon. Soon !!
Jeff
Edits: 10/16/14
Lowes is fine. Make sure the opts are covered with the new quantum stealth material. The amp will really disappear. With the black components I mentioned, you will have an invisible amp with the sound emerging from blackness!
Edits: 10/16/14 10/17/14
Jeff , I can see the problem here is that you just can't THINK out of the box . This muddy thinking , I feel , will seriously be affecting your MUSICAL enjoyment .
Cardas posts are very poor signal carriers as are the Edison Price posts which you recommend . If you want to put a musical signal THROUGH either of these : THINK AGAIN ! These binding posts are manufactured from brass which due to it's own chemical composition is a poor electron carrier , even when plated with Rhodium , gold or silver . The electron cloud that forms inside all metals when passing electrons , inside brass forms a barrier which acts as a moderator , limiting the flow of electrons . What you are left with is an ohmic result of the skin effect which exists due to the plating used . You could say the electrons are slowed down within the metal , they tend to also lose synchronicity causing timing errors within the musical signal . To avoid this , I would strongly recommend silver . Furutech solid silver outboard posts are now available from Michael Percy , these must be wired to your output transformers with 10AWG Siltech wire using the BEST solid silver solder you can afford . Wonder solder just does not cut it here ! Never have a binding post that passes through the chassis with insulators . This will form a magnetic field causing a shorted turn which will BUCK OUT the musical signal . If you build with anything else then you are building PURE shit which should never be powered on . Don't say you haven't been warned...
Al
Al, thanks for this warning! On your advice I will stop using brass as a conductor. I only hope your advice doesn't fall on deaf ears.
1) You are going to get a white washed bleached out sound. Those input jacks should be black on the inside so as to provide a blacker background. Have someone customize the inside with black carbon fiber. They sound better.
2) Tube sockets. Same applies. Black sockets sound better. The electricity which stimulates the electron flow comes up throughout the pins. You want to keep everything black. The blacker the components, the quieter and blacker the background. The sound will pop out of darkness.
3) Get rid of the white wires. Same reasoning.
4) The six holes in the shape of a V is wrong. They should be in the symbol of a peace sign or a ting and yang design to make listening more harmonious.
Those are just the first few things. Amp is dead without addressing those issues first.
no way ever hear a black base then a brown base octal or ux type. brown always sound better. I never buy black connectors or wire other then ac for legal reasons.
PTFE (Teflon) is better still, a rather nondescript colour but I'm not too concerned with fashion. I also like ceramic bases but they are only available in white, which can cause sonic dazzle.
Hi Jeff,
Looks like it is coming along nicely. Can't be too long now until you can switch it on and give us some idea of its sonics.
Cheers.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
Jeff, you may need to qualify your claim a bit. You said "the first Directly Coupled 6AH4GT two stage power amp ever built."
Coincidentally, a few months ago somebody posted on DIYAudio about his Direct-Coupled 2-stage 6AH4 push-pull amp. His schematic is shown at Post #6 at the link below.
Of course, maybe yours will be the first SE version.
It may be a first but will probably be the LAST ! It certainly need s lot of work to put right and bring it up from low to mid-fiThere are no brass fixings and no brass washers . Everyone knows the fixings provide 90% of the sound of an amplifier . By the fixings alone , you may as well scrap it and start AGAIN !!! Surely with a paralleled 12AX7 per channel , you will get the 'choir' effect ? There appears to be an issue with the chassis . It appears to be too big and the top plate appears to be the WRONG colour ! It does not follow the golden ratio either and the sides appear to be made of wood which negates ALL the benefits of a steel chassis . Look at that long run of white wire , the transfer LOSS must be phenomenal . Didn't Dr Halijack tech you anything ? The musical electrons will slow down , may become diverted to other parts of circuitry or not arrive at all causing irrepairable timing errors in the musical signal .
You should have breadboarded first . Never mind... zzzzzzzzzz
Al
Edits: 10/15/14
I think this project won't rise to truly memorable levels until you FENG SHUI it. Remember that all amplifiers have SOUL and they have to WANT to sound good. They should INVITE you, LURE you in, EXCITE and CALM you at the same time.
1. It must be used only in truly FENG SHUI'd homes, with proper control over animals and foodstuffs.
2. Open the windows often or use a good quality air-purifier to keep the air fresh and full of oxygen. OXYGEN is important for ELECTRONS.
3. Have several levels of lighting in your hi-fi room, or use a DIMMER SWITCH to adjust the ENERGY accordingly.
4. Use SOOTHING COLOURS to achieve a good feng shui BALANCE in the internal wiring. Dr. RUDOLF STEINER has suggested a palette of PASTEL colours which may suit.
5. Keep all the DOORS CLOSED during audition to ensure the OPTIMUM ENERGY FIELD in the listening environment. Electrons are restless things, and some may be tempted to wander round other rooms.
Andy,
Q. You mean like the place wherein you reside ??
A. " Well,.... not exactly. "
Jeff Medwin
Some good points made... I think he can add genuine benefit (and value) by adding some small household shrubs to assist with those poorly-placed electron scattering voids . Maybe even some Victorian-style sash windows to compliment the wiring combs on the top of the chassis ?
Al
Nobody has mentioned *C*R*Y*S*T*A*L*S* yet! How do you expect to attain the dizzy heights of audio reproduction excellence without the judicious application of crystals? Huh? I respectfully refer y'all to the Tweakers' Forum, where you may learn the path to truth and understanding.
With a max rating of 7.5 plate watts you will probably be running with 5 watts dissipation. This should put out about 1 to 2 watts with 10% distortion.
If that power is not quite enough, take a look at the 6V6GT in triode as a possibility as well. You can get about 4 watts and it should be pretty easy to implement with what you have. 6V6 tubes sound great.
50 milliWatts to 500 milliWatts is where it runs most of the time on efficient, sensitive speakers. Its all about performance in the first Watt.Jeff Medwin
Edits: 10/17/14
Don't overlook the 1626. They make really awesome 1/2 watt amps.
The 1626 enjoys a following because it's inexpensive. However, the published curves don't look good, and reported distortion numbers are correspondingly high. There are a number of pentodes that will easily surpass this tube when run in triode mode.
--------------------------
Buy Chinese. Bury freedom.
The little 1626 just has something appealing about it. 1/2 watt amps need to have a certain bloom very early on. They look like a micro sized power tube. My first suggestion was a triode 6V6GT. The 45 is the obvious choice in 1 watt amps.
Chip,Better than the 6V6 is a triode-connected 6AQ5, which I have done a few times since 2008, smaller more "explosive" and a kick - a** sounding tube.
I wanted, in addition to a 6AQ5, to do a SE DC 6AH4 amp, as no one has ever done it to my knowledge.
I have heard the tube line-up as a Direct Couple in a 1990s Art Loesch P-P amp I had on hand, a 12AX7 diff amp, DCed into P-P 6AH4GTs.
"How much nicer the tube combo operating as a mini SET will sound", is what I thought as I listened. I am only three hours labor away from discovering what it is like in SE. Exciting !!
Jeff
Edits: 10/17/14
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