Beginner Monoblock

[kt88pppamp]

For a starter project I want to construct a quad (four tube) 6v6 monoblock amplifier. I want no preamp circuitry. I will construct a seperate preamp at another time. What should I do here?

Thanks

[TomMcNally]

To be honest ... I'd start with something simpler if it's your first time building. Shannon's DIYTube Stereo 35 is a great design, easy to build, (both soldering the board and the mechanical work) and sounds great, and the instruction manual is very well done. If you want something more powerful, the ST-70 clone using the transformers and chassis from Triode Electronics is a nice way to go too.

[kt88pppamp]

I would like something simpler to tell you the truth. The one problem I have is my speakers. My wharfdale W60D's I assume are reasonablly efficient (have used a two 6v6 tube amp with them) but since I don't know their wattage per decibal rating, I really don;t know where to start.

[TomMcNally]

I can't find any data on the Wharfedale WD-60s online ... I suppose there is a standard way of measuring speaker efficiency, but most of us aren't going to have the test equipment necessary. I'd do a simple practical test and just drive them with something small ... like an iPod or little transistor radio and see what they do. Depending on your listening requirements (ie: background music or shake the house) you may be able to get away with less than you'd expect.

I've built a bunch of amps ... single ended and push-pull, and a kit that uses four EL-34's in PPP per channel. If you'd like to take a look at the pix and schematics (take a look at the Darlings for something real cheap and easy) my web site is at: http://mcnally.cc/amps.htm

... tom

[WA4SWJ]

Tom,

I'm sorry, I don't want to hijack the thread, I'm just curious how the Darlings sound. They should be pretty simple to build.

Regards,

[TomMcNally]

Hi Ed ...

I've built 5 Darlings using the schematic you see on my site under the pic of the Industrial looking gray amp ... they really are easy - I built one of them in one evening (of course I had some practice) They sound really good for the money (probably well under $ 150 with all new stuff)

You will need some decent speakers, and they do have a very definite point where they "run out of power" and don't get any louder, just distorted. It's a cool bedroom or office amp. I have all the stuff to build another one, just need a little ambition. Some guys have paralleled the tubes for more power, but I don't see the point ... just use a bigger tube ... but it's all fun I guess.

... tom

[kt88pppamp]

Kit building plus reading sounds like the best idea so far. I ordered the book Beginners Guide to Tube Audio. I also found an inexpensive kit, the K-12M. I listen to a lot of records (even 78s) and the line input is 100k ohm. I do not think my turntable can drive it directly (I am using a shure cartrage on my thorens TD-126). Need tube preamp schematic. It has 8 watts per channel, will try with my wharfdales and see what happens.

[mesherm]

kingneb, If you intend on playing records you should be aware that since the 1950's all records have been recorded with the lower frequencies reduced and the higer frequencies increased. RIAA equilization. Assuming you had enough gain to play the output of your phono cartridge directly it would sound tinny at best. All pre-amps for records have a RIAA equlization network in their phono section that returns the phono signal to its original condition. The sound engineers did this because among other this the high level low frequencies make the recording track a lot wider and decrease the available recording time.
You will need a preamp that has an RIAA network in it to make the sound listenable. There are many inexpensive solid state units on the market that will do this. I recommend using one of them until you have your K-12M up and running. Trying to build a tube preamp with RIAA is a job even for skilled tubers. You could also try eventually to pick up a Dynaco PAS 2 or 3 on ebay but for now, if you are new to tubes, I would just concentrate on building the K-12M.
JMHO
Mike

[kt88pppamp]

I performed a basic efficency test on one of my wharfdales. I connected one channel of my discman to it (two AA batteries with about 60% life left). I was impressed, at full volume I got about the same amount of sound as around a 15% turn on the volume control of my 70 watt-per-channel solid state amp. Will 8 watts be sufficient to power these?