Tube Integrated Amp Kit Project

[kurtbauer]

I'm thinking about building a tube-based integrated amp kit for my office. Can you all give me some pointers on where to start looking. I'd like it to look good and sound very good. I have some experience building/repairing hi-fi equipment but am not an expert by any stretch.

I would also consider an old tube integrated too but am unclear what might be a good basis to start from.

So far I have ruled out building something from scratch. I really don't have the facility to do the mechanical aspect.

Any guidance/thoughts would be appreciated.

Many thanks.

Kurt

[chrisb]

if your power requirements are modest (2 wpc), the Bottlehead S.E.X integrated amp is worth a look.

[crispycircuit]

I've had many integrateds over the years. My favorites are Scotts and then Eico ST 70 & 40, Eico also had Classic integrated that was very nice... These can be modified as your needs and experience grows. Also they hold their value....

[kurtbauer]

Thanks guys, I'll dive into these for a while. I particularly like the vintage stuff but I've heard good stuff about the Bottlehead gear.

This sure is fun.

[Pyre]

If you are looking for a good place to start and something vintage I would recommend a Dynaco SCA35.

There are a lot of mods that can be done to it to make it sound amazing. As long as the transformers are good, the rest of the parts to make it sing are relatively cheap and easy to find.

[talaerts]

The Velleman tube kits look rather nice, in my opinion

[chrisb]

Originally posted by kurtbauer
Thanks guys, I'll dive into these for a while. I particularly like the vintage stuff but I've heard good stuff about the Bottlehead gear.

This sure is fun.

No doubt that certain vintage models are still great performers half a century on, but they're not without their problems;


- If completely original, there may be many parts that have gone far off value or altogether defective (carbon comp resistors and power supply EL caps).
Arguably, some of the parts choices (i.e. material types) of passive parts might be considered sub-par by today's standards, but wholesale upgrading is no guarantee of improving performance or even reliability.

- Pre-amp stages (input switching and EQ/Tone control circuitry) may be significantly more complicated than needed for today's prevalent program sources.


Indeed many of the few currently offered kits or DIY amp projects classified as "integrated" amps are not much more than power amps with rudimentary input selection.
Thanks(?) to the proliferation of digital sources with output levels generally in excess of requirements of most amp's input stages, it's possible to get great performance with circuits as simple as the Bottlehead SEX, or very low parts count "gainclone" or Tripath style SS amps.

Don't forget to consider the loudspeaker and room environment when considering your choice of amp; power requirements , physical size and heat dissipation can all be issues.

Just for fun, you could consider something like this, with a iPod type device as digital media input:

http://www.questforsound.com/tuners/tuners_R601S-S.htm

http://www.6moons.com/audioreviews/tubetuner/r601p.html

[kurtbauer]

Thanks for the suggestions. For what it's worth, I think I'm going the vintage route.

My current leaning is an SCA-35 as I'm have an ST-70 and am currently modifying a PAS3. So I'm comfortable with Dynaco. Pyre, I've found a few mods for the SCA-35 in some inititial searching. Are there any favorites?

That being said, based on crispycirsuit's recommendaton, I will look more deeply into Scott and Eico. It may be good to branch out.

Have a great weekend.

[Pyre]

I don’t think you can go wrong with a SCA-35 as your obviously a dynaco guy. I had one a while back and and did not do to much too it circuit wise but updated a lot of the connectors and such.

Replaced all wiring with siver plated copper
Put in a cap board
Bypassed the tone controls
Replaced the selector switch
Changed the speaker connectors to posts
Replaced the rca jacks with gold plated ones.
Bypassed the balance control and replaced the Volume with an Alps pot
Bypassed all the filters and power switch

Mostly I just took stuff out of the circuit and upgraded the connections. It sounded fabulous when I was done and still looked original on the front.

What are you doing to your PAS3? That’s more in my department I have 3 right now that I have modified in different ways.

[kurtbauer]

Pyre, I'm doing an AVA mod in my PAS3. This will be my first one so I wanted to get something I know SHOULD work. Then if it doesn't it's all on my workmanship. Theoretically, anyway. Haven't started yet but I'm aching to do so.

I've settled on the SCA-35 but I've spent a little time following up on the Scott/Eico recommendations. The HR-81 caught my attention. It seems to be well-supported with info on the Internet. There's a guys who has worked on both so I've asked him his opinion. We'll see what he says. I may try this as well if I can come up with another excuse to that passes muster with my wife.

Still crunching on the Scott front tryng to decipher which models are which and their associated virtues. Looks like there some potentially cool options here as well.

Regardless, I'm on the hunt for a SCA-35 now. In general, I plan to take the path you suggest and then see what else may make sense after that. Looking at one on eBay but it's so hard to tell what you'll get. The good news is there's no time pressure.

Good weekend to all you guys.