Stereo amplifier

[dynaman]

I know there are better forums for this question, but does anybody know of a relatively simple stereo design that would lend itself well for use with an iPod or some other external player?? I know there are lots of PCB based kits floating around, but I'd like to try wiring it up myself. Looking to get 5-20WPC with a simple gain control. It doesn't need to have absolutely stunning audiophile performance and I don't care if it's SE or PP, but I'd rather not use any exotic or hard to get tubes. I don't have a 'scope so I'm hoping someone might know of a proven design.

Please and thanks!

[Cliff Schecht]

Read over Pete's website: http://pmillett.com/

Lots of projects and Pete takes a very analytical approach to amplifier design in an attempt to break a lot of the hifi myths. Some of the designs use goofball tubes, others aren't too gimmicky and AFAIK they all sound good.

[xtian]

There are some good tube projects here:

http://www.beavisaudio.com/projects/

[Alexo]

I built one of these a few years ago; simple, good instructions, sounds great and perfect for what you're asking:

http://angela.com/stereosingle-endedel3 ... ifier.aspx

EDIT: looks like the pic's of the build didn''t make it through to their new site! Just makes it more diy for ya...

[dynaman]

Thanks for the excellent tips.

I've now realized that space is a consideration. This amp will have its own chassis that will be fitted into another enclosure. I bit the bullet and looked into some compact tubed PCB preamp driver/PI modules that are designed to work well with sources like mp3players/iPods and could mate up to some basic tube output circuits. The required preamp is beyond my scratch build skill level anyway, so this might be the way to go. Pete Millett's design certainly looks interesting and is relatively small.

However, that circuit found on Angela's site that Alexo posted doesn't look like it would use up a lot of chassis space. Angelo, did you have any probs with the operation of your amp? Did you require a separate preamp or can you drive it with just a CD/mp3 player??

[Structo]

Have you checked out DIY Auido?

There is a guy over there that sells a couple different circuit boards.
A single ended one and a push pull.

This is the guy and his website.
http://www.tubelab.com/

I bought a SE board but don't know when I will be able to build it.

It has some semi conductors in it but they are for a constant current source and are not in the signal path.
It gets pretty high marks for a small stereo amp.

[img:624:480]http://www.tubelab.com/images/SimpleSE/New_Boardb.jpg[/img]

[dynaman]

Have you checked out DIY Auido?

There is a guy over there that sells a couple different circuit boards.
A single ended one and a push pull.

This is the guy and his website.
http://www.tubelab.com/

I bought a SE board but don't know when I will be able to build it.

It has some semi conductors in it but they are for a constant current source and are not in the signal path.
It gets pretty high marks for a small stereo amp.

[img:624:480]http://www.tubelab.com/images/SimpleSE/New_Boardb.jpg[/img]

Haha, I just spent an hour looking through his site! Good call! So, he's still in biz??? How was the turnaround time on your board?

[Ian444]

I know there are better forums for this question, but does anybody know of a relatively simple stereo design that would lend itself well for use with an iPod or some other external player?? I know there are lots of PCB based kits floating around, but I'd like to try wiring it up myself. Looking to get 5-20WPC with a simple gain control. It doesn't need to have absolutely stunning audiophile performance and I don't care if it's SE or PP, but I'd rather not use any exotic or hard to get tubes. I don't have a 'scope so I'm hoping someone might know of a proven design.

Please and thanks!

I spent a few years investigating this. Here is what I found. Use a PT good for 175mA min with around 320V B+. PP fixed bias with Russian 6P6S (6V6) tubes from the Reflektor factory 1970's or 1980's vintage (cheap and excellent sound). For OPT's use Edcor, or Z565 from Triode, or anything PP lying around with a prim Z of 3K5 to 7 or 8K. For preamp/PI use a 6N1P-EV (cheap and excellent sound) with a gain stage followed by a cathodyne. The Tubelab.com Simple PP is an excellent cct for 12AT7, and its pretty hard to make a 6N1P sound bad, no matter how hard you try. Run it with Mark Audio 4" full range drivers in sealed boxes (or box of choice) and no NFB in the amp (no NFB gives more gain for the ipod and is not required for single 4" drivers). Let it all burn in for 100 hours. Result will be outstanding. Use metal film resistors and cheap components, caps, etc, that you have lying around. Boutique stuff is not required. It cost me several thousands of dollars to find out I only had to spend in the hundreds of dollars range If you want to follow a proven cct then the Tubelab Simple PP is simple and excellent, can post a schem if you want. It is my "most fi" amp, but not the one I listen to most. The one I listen to the most is the one I described. Can post a schem of the 6N1P stage if you want, same as the Simple PP but different resistor values.

[Structo]

I got it within a week and he was even on vacation!

His website is pretty fun to read as well.

The Hi Fi crowd are even crazier than we are.

[Ian444]

I sort of wandered over here from the hifi crowd, I have a lot of respect for you guys, seems building a good guitar amp is a lot harder than building a good hifi amp! And to make life more difficult, some things that make a hifi amp sound good make a guitar amp sound bad! Or the other way around...

Yep George from Tubelab is well known on diyaudio for his pyrotechnic tube testing techniques and hi power tube amps. He knows his stuff, and has a good reputation, which he truly deserves.

[dynaman]

Heh, Ian, I blew thousands on hifi as well. My (relatively cheap) $400 phono cartridge didn't sound any worse through the fancy monoblock amps I made with....cheap Xicon caps. I tried other brands, but was just as pleased with the low-grade components I picked up from my local electronics store. I guess my hearing isn't what it used to be.

Anyway, I'll snoop around some more on Tubelab. Glad to hear that Tom got his stuff quickly, cuz this amp is not for me and I don't want to caught in a pinch.

I'm hoping Alexo will chime in a bit more about his amp cuz I've found some build pics of the same circuit and it seems to be pretty popular. More importantly, folks have squeezing that amp into fairly small chassis with no ill effects. I just shoehorned a two channel Plexi sorta thing with 4X6V6 into a Marshall Class 5 chassis, so I think I can cram four octals and three trannys into a little Hammond box and hide it in its final resting place.

Ian, I'd be obliged if you'd give me a glimpse the circuit you spoke of. I'm not looking to mass produce someone's proprietary design - I'm just doing a favor for a repeat customer. Hell, ifn y'all seen what this amp will ultimately go in, you'd prolly roll your eyes and tell me to use a circa '83 Panasonic boombox.

[Ian444]

I don't think there's anything proprietary here, except copyright on the Simple PP PCB design. Not sure what you wanted to see, so here's the whole lot.

Simple PP schem

6N1P input stage

crazy 6V6 amp with 6N1P and Chinese trannies/chassis

[dynaman]

I don't think there's anything proprietary here, except copyright on the Simple PP PCB design. Not sure what you wanted to see, so here's the whole lot.

Simple PP schem

6N1P input stage

crazy 6V6 amp with 6N1P and Chinese trannies/chassis

OK, I was just wondering if what you mentioned in your first post was the same as what I viewed when surfing the Tubelab site.

Regardless, viewing your "elevated" Russkie 6P6S amp was worth the price of admission. The tubes look....Orwellian. Like some 1/16 scale Russian "War of the Worlds" alien invaders that are working for their much larger Chinese counterpart. I fear your amp is a harbinger of things to come.

[Ian444]

Funny that a few people have said leave that amp like that, rather than fit octal bases, just cause it looks strange/good.

Who knows, regarding Russian/Chinese, my missus reckons its the quiet ones you gotta watch. For now, it is nice that they never really stopped making tubes, leaving us a legacy of millions of NOS tubes that mostly work well, even so many years later.

Thinking again, back on topic, I believe some ipods are a bit low in output level compared to a standard signal source, so gain may be a problem. Might be best to borrow customers ipod to see how it drives your own stereo and get an idea if gain may be a problem or not. The tube hifi designs rely on a decent input signal to minimize non-linearity by using the least required gain to get a good result, as you probably already know anyway...having been through the mill so to speak.

[piperbob]

Check the Bottlehead site. I have built their preamps and power amps and am really happy. Two of their amps have a headphone jack too.http://www.bottlehead.com/store.php