I dont think you need any gain, or max 6db
but its easier to get low output impedance with no gain buffer CFB design(cathode follower buffer)
better to look at impedances
impedance of your pot depends on input input impedance of your chip amp
and preamp output impedance should relate to your pot impedance
if you like/prefer Broskies kits, theres a new all in one CFB, with just two tubes(ACF-2)
but its easier to get low output impedance with no gain buffer CFB design(cathode follower buffer)
better to look at impedances
impedance of your pot depends on input input impedance of your chip amp
and preamp output impedance should relate to your pot impedance
if you like/prefer Broskies kits, theres a new all in one CFB, with just two tubes(ACF-2)
I would say its very much design releated, in any case
to judge fairly you also need to know how they use it
and all the rest of their gear
most important is to get reliable and low noise tubes
and make it function optimally and reliably, in the whole design
and in a way that it functions as a unity with your own gear
thats what matters
so, I would look at what you need to run your chip amps
together with your speakers, and what comes out of them
in the end, all that matters is what you hear
first step could be to think, what is it I hear now, and what is it want to hear
and the choose design and components from that
takes practice tho, and luck
my immediate thought was that with a chip amp you might want something with 'good solid body'
not that I ever heard any chip amp
OK, fair enough, I have to say that listening to my LM4780 chipamp I like it MUCH better than my multichannel Class-H+ that I run for home theater.
I don't really feel that I'm "Missing" anything from my music but I do think that my chipamp is more "revealing" than my Class-H+.
The main purpose of my experiment here is to build a simple two channel that delivers 100W RMS to 4+Ω loads with a tube front end.
I have to admit that I have never heard tube equipment on any of the gear I own.
I have listened to tube preamps on solid state and tube power amps in a local store and I like the sound very much.
I am young enough that I have never seen tube equipment in a catalog or on a major store shelf and I am just starting to get into DIY.
I have already built my chipamps and I love the way they sound just driven directly from my PC or my MP3 player but I fear that I am not doing them justice in this application.
I don't really feel that I'm "Missing" anything from my music but I do think that my chipamp is more "revealing" than my Class-H+.
The main purpose of my experiment here is to build a simple two channel that delivers 100W RMS to 4+Ω loads with a tube front end.
I have to admit that I have never heard tube equipment on any of the gear I own.
I have listened to tube preamps on solid state and tube power amps in a local store and I like the sound very much.
I am young enough that I have never seen tube equipment in a catalog or on a major store shelf and I am just starting to get into DIY.
I have already built my chipamps and I love the way they sound just driven directly from my PC or my MP3 player but I fear that I am not doing them justice in this application.
Let me see if I'm following your idea properly.
Use a 50VA isolation transformer on the mains power to supply 120VAC to a full wave bridge rectifier which will run about 170VDC to the elements.
Then use a 6.3VAC transformer from Radio Shack to power the heaters.
How would all this be wired?
I'm very new and I like the Kit Idea a little better so I can learn.
OTOH if I had clear instructions on how to create the circuit you describe I would learn a lot more and build would probably be cheaper.
Thank you for your suggestion.
Use a 50VA isolation transformer on the mains power to supply 120VAC to a full wave bridge rectifier which will run about 170VDC to the elements.
Then use a 6.3VAC transformer from Radio Shack to power the heaters.
How would all this be wired?
I'm very new and I like the Kit Idea a little better so I can learn.
OTOH if I had clear instructions on how to create the circuit you describe I would learn a lot more and build would probably be cheaper.
Thank you for your suggestion.
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You will learn lot's either way.
If you go the route suggested above, you'll have enough support here.
The "FWB" is a full-wave bridge rectifier, used in lot's of projects takes the line voltage and steps it up ~1.4 times and makes it DC. Lot's of schematics on this. You can make it with 4 diodes, or use a pre packaged rectifier. This along with a couple of caps and maybe a resistor composes your power supply. Lot's of examples online for this.
The heater circuit is straight forward. Just wire the heaters in parallel just like normal light bulbs, from the 6 volt transformer. Ideally it would be 6.3 volt but will still work slightly lower or higher.
Maybe someone else can point out a Cathode Follower circuit for you. I might try one myself in my amp.
If you and your helpers state what you are using I would gladly draw a schematic for you. I would literally just be drawing it, so proper values should be supplied by the more experienced members.
If you go the route suggested above, you'll have enough support here.
The "FWB" is a full-wave bridge rectifier, used in lot's of projects takes the line voltage and steps it up ~1.4 times and makes it DC. Lot's of schematics on this. You can make it with 4 diodes, or use a pre packaged rectifier. This along with a couple of caps and maybe a resistor composes your power supply. Lot's of examples online for this.
The heater circuit is straight forward. Just wire the heaters in parallel just like normal light bulbs, from the 6 volt transformer. Ideally it would be 6.3 volt but will still work slightly lower or higher.
Maybe someone else can point out a Cathode Follower circuit for you. I might try one myself in my amp.
If you and your helpers state what you are using I would gladly draw a schematic for you. I would literally just be drawing it, so proper values should be supplied by the more experienced members.
I have a couple of SS FWB rectifiers in my parts bin that will work with those voltages.
I just need a transformer, I'm thinking of this one it should work well with a single 120 and two 6.3's.
Other than that I would really love a diagram for hookup, after I get a basic layout I can start looking at component values.
I just need a transformer, I'm thinking of this one it should work well with a single 120 and two 6.3's.
Other than that I would really love a diagram for hookup, after I get a basic layout I can start looking at component values.
Here are some info about the cf.
The Valve Wizard -Cathode Follower
SYclotron Audio The Heretical Preamp
Hope that help you to build a linestage.
The Valve Wizard -Cathode Follower
SYclotron Audio The Heretical Preamp
Hope that help you to build a linestage.
I really think I am going to go with the Aikido 9pin all in one or the ACF-2 kit.
Between those I have not decided yet.
I'm pretty sure I will be going with the 6CG7 tubes for either one.
The Aikido kits look like they pretty well take all the guesswork out of it as long as you can solder and follow directions.
Between those I have not decided yet.
I'm pretty sure I will be going with the 6CG7 tubes for either one.
The Aikido kits look like they pretty well take all the guesswork out of it as long as you can solder and follow directions.
A little bit of gain - is in the aikido - wont hurt as opposed to a more specific application like a cathode follower buffer.
I built a Pass B1 and while I was properly warned about the fact that it has no gain I wanted to build it and with my speakers and the amp I was running at the time even at wide open it was simply not loud enough.
Impedances are important to consider but for a first attempt at a tube build I would say go with a full aikido for maximum flexibility - the 9 pin is good as far as tube choices. 6CG7's will give you a modest gain of about 9. I typically run 6CG7s in my 9 pin and they sound awesome readily available too both new issue and NOS. A 50K or 100K pot will be sufficient. You can get nice Alps 100K pots from Mouser for about $15.
The all in one kits are nice so that all you really need to add are some RCA jacks, power inlet, fuse, chassis and xformer and you are ready to rock.
I built a Pass B1 and while I was properly warned about the fact that it has no gain I wanted to build it and with my speakers and the amp I was running at the time even at wide open it was simply not loud enough.
Impedances are important to consider but for a first attempt at a tube build I would say go with a full aikido for maximum flexibility - the 9 pin is good as far as tube choices. 6CG7's will give you a modest gain of about 9. I typically run 6CG7s in my 9 pin and they sound awesome readily available too both new issue and NOS. A 50K or 100K pot will be sufficient. You can get nice Alps 100K pots from Mouser for about $15.
The all in one kits are nice so that all you really need to add are some RCA jacks, power inlet, fuse, chassis and xformer and you are ready to rock.
You can't go wrong with an Aikido. A long time ago I bought a cheap chinese ebay preamp kit and it was a waste of money. Later when I learned more I found the chinese circuit was terrible and barely even worked, let alone sound good. Aikidos sound better than you will imagine. Your chip-amp power amp will definitely be your weak link then..
I fully understand the aversion to Chip-Amps in the Tube forums but I am quite happy with my LM4780, Peter Daniels kit is wonderful and I think that a tube front end is just what it needs to warm it up.
The next question is if I go ahead and but the 4ea. EH 6CG7 tubes when I order the Aikido or do I save that money and pick up a "Matched Quad" of cheapies on E-Bay.
I always had the intention of picking up a high dollar matched quad in a gold pin variant or such, I'd just hate to blow up a nice pair in testing.
The next question is if I go ahead and but the 4ea. EH 6CG7 tubes when I order the Aikido or do I save that money and pick up a "Matched Quad" of cheapies on E-Bay.
I always had the intention of picking up a high dollar matched quad in a gold pin variant or such, I'd just hate to blow up a nice pair in testing.
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