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I'd like to build a SET. My speakers are high efficiency Altec Model 19. Can somebody recommend a design or a thread for me to start with?
thanks.
Follow Ups:
You're probably thinking about triodes, but it's hard to go wrong with the Mullard 3-3 SE pentode design. I use a modified version of this (different circuitry at the EF86), and it's easily in the top five of all the amps I've heard. It's cheap to build, the cost being determined primarily by choice of tubes and output transformers. The circuit is also an excellent start for DIY. A 6V6 can be substituted for the EL84/6BQ5 with very few changes, and the output stage can easily be rewired for triode mode.
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Buy Chinese. Bury freedom.
Edits: 10/27/15
As people mentioned there are some big holes in your query.
Skill level; If you are a "handy" type of person who likes to make or fix things then you could probably do a good job with a kit. You might be even able to build one from scratch by custom ordering all the parts.
Finances; If you have deep pockets Audio Note Kits are about top of the line. If you want to drop in and not get hosed buy a Single ended console amp from the 60s like Magnavox, Zenith, RCA, etc. and rebuild one of those. And don't dismiss the sound quality of those units. They can sound extremely good, especially if you have not heard a single ended amp before. The amp can be bought for about a hunret buxs and since you are a noob, rebuilding an already "working" amp can be a good warm up for building an amp of higher quality. cheers, Dak
I agree with deafbykhorns, the skill question is a big one. If you select a design that exists as a schematic on the internet, will you be able to lay out a chassis, machine it, then translate that schematic into a parts list/layout/build?
How much you are willing to spend STRONGLY influences your selection.
It is possible to "test the water" without a large cash outlay. The approx. 2 WPC triode wired 6V6 family tubes yield is sufficient for your speakers. It has been said that short of #45 DHTs, nothing sounds better in this power range.
An inexpensive, but high performance, B+ PSU can be built by "full wave" doubling the O/P of a Triad N-68X isolation trafo. High PIV Schottky diodes are every bit as quiet as vacuum rectifiers. ;> )
Eli D.
nt
This 6V6 family is large and I probably don't know all of its members.
In Loctal , you have the 7C5 and 14C5. In 7 pin mini, you have the 6AQ5, 6005, and 12AQ5. In Noval, you have the 6CM6 and 12AB5.
Eli D.
Add 6BW6 to the list which is a 6V6 on a noval base . AFAIK Brimar was only manufacturer of these but are available cheap as NOS
Russian 6P1P is another . This is often sold as 'EL90' and is another 9 pinner and typically costs $1 . May also be worth considering
I'm with Andy though . 4P1L slays just about every IDH tube going...
Al
A Darling would be an interesting place to start. His speakers are more than sensitive enough to accommodate either or both of these tubes and there are a number of alternative designs.
I'm guessing they are minimal (no offense).
Please elaborate on soldering skills, equipment, basic electronic knowledge, experience with HV
Edits: 10/26/15
You will get a mass of answers that will recommend you to use 2a3 or 300b output tubes. That's fine except:
- they are expensive and getting more so, and remember they need to be replaced as well
- they are low gain so you need 3 stages or a high gain input tubeI took the path of using PSE 4P1L outputs because:
- they sound pretty much as good - this is a DHT also
- they have gain of around 9 so you can use 2 DHT stages, e.g. 4P1L first stage as well
- they operate at 250v and 70mA for a pair (18W dissipation) so simpler PSU
- a pair in PSU uses a 3.5K OPT same as a 300b
- they are CHEAP and you can buy a lifetime supply for the price of one premium 300b.
- they can be used in filament bias which eliminates the cathode bypass capResearch all this together with schematics at DIY Audio, thread "4P1L DHT Line Stage". And also same site, "One more 4P1L SE",
More information at www.bartola.co.uk including lots of technical details. Ale Moglia is an authority on all this. While on that site, look at his 01A Gen 2 preamp, which is the best I've ever heard. It's just stunning. And I've built several 26, 10Y, 4P1L etc. preamps myself.
Edits: 10/26/15
Try bottlehead.com They sell great kits a 2a3/ 45 kit. A 300b and a el84 kit well thought out excellent direction and a great help forum. Even if you don't buy a kit join the forum plenty to be learned
Thank you everybody.
I'm a long time scratch build tube guy. I was looking at a 2A3 design I saw at Hand Made Electronics. 6J7 and 2A3. Seems simple enough for a start. Any input?
.....someone mentions the obvious............a 2A3.....or maybe a sweet 45 ....or a 300B..........why is everybody else so far focused on all these minor players? If I was starting from scratch and was willing to work my but off, I'd be a bit P O if I spent all that time on a tube configuration that can't touch the sound of the primary single ended triode options.
Tom B.
The topology of that circuit is fine, a classic really. However, the 6J7 is operated at a very low current and high impedance; it cannot drive the 2A3 Miller capacitance at high frequency - I estimate about -3dB at 14kHz. This was high fidelity in the thirties and forties, and will sound pleasantly mellow - but not high fidelity by today's standards.
The simplest change to improve the high treble would be to replace the resistors that set the driver operating point. I suggest these:
change the 2000 ohm cathode resistor to 600 ohms,
change the 0.25 megohm plate resistor to 0.10 megohm (100K),
change the 1.5 megohm g2 resistor to 530K
(I would also increase the cathode-g2 capacitor from 0.1uF to at least 0.27uF, to be consistent with the resistance changes.)
These values are taken from the RC amplifier table in the back of the RCA tube manual; there may be better options but the above is "tried and true". I will further suggest wiring the output transformer for 2500 ohms - this will match the RCA manual's suggested operation of the 2A3 (and will give you twice the power with deeper bass). The suggested Hammond 125E has been superseded for this application by the larger 125ESE which can handle the DC current much more gracefully; both can be wired for 2500 or 5000 ohms.
By the way, if you do not like the top cap grid connection, the 6SJ7 is similar enough to work with the same resistances. The unspecified hum pot across the 2A3 filament would usually be around 20-25 ohms.
I strongly encourage you to not waste too much time trying to choose the Perfect Circuit, but rather to go ahead and build something.
"I strongly encourage you to not waste too much time trying to choose the Perfect Circuit, but rather to go ahead and build something."
Yessiree! It's all too easy to get totally stuck in a quagmire of indecision, made worse by the infinite opinions and designs presented and recommended on the Internet. Nearly all the popular tube designs sound great when properly executed!
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Buy Chinese. Bury freedom.
Well, now that we know that you are an old time solder slinger it is just a matter of picking your poison if you know how much money you want to spend on the project.
It seems that the power triodes are all the rage nowadays and so one must pay a large price for participating. To me running pentodes like el84 and el34, or beam power tubes like all the 6l6 types will get you very, very close to the triode sound with many more options. I have several amps that I can run a 6v6 to a 6l6 and others that run el34, kt66, 77, 88, 90, 6550, 7027. With a simple switch you can run between triode and pentode or ultralinear for even more listening options. This allows me to utilize all the different power tubes that I have collected over the years. I find that this is not only sonically satisfying but also a ton(e) of fun. cheers, Dak
Look at the 26,56,76 to drive the 2A3
Don't skimp on the OPT, makes all the difference
Edits: 10/27/15
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