Thoughts Of Modifying My First Tube Amp.

[dantwomey]

I've only owned my very first tube amp for a couple of days now and my DIY nature is already turning my thoughts to how I can modify/improve it. Although I've got a few electronics/speaker projects under my belt now I've never touched tubes before so I have quite abit of reading to do. That aside, do any of our more experienced tube forum members want to throw a few ideas around where I might makes some gains here?

Regards,
Dan

[gingertube]

Tel us what the amp is and we may have a few clues to pass along.
Cheers,
Ian

[dantwomey]

845 based SET integrated. The website is LS845-1.

Regards,
Dan

[Hartono]

Be careful, those voltage bites

[SY]

What is it that you're specifically trying to improve? Or is this just a matter of, "I can't keep my hands off this, please tell me something to do which will keep me occupied?"

If you're attacking a commercial design, it first helps to understand it. If you can't point to any resistor at random and say what it does, you ought to keep your hands out of it until such time as you do. Presumably, the guy who designed it had at least some minimal level of competence, so you're not repairing or correcting obvious errors.

MOST importantly, you need to have the right tools (sig generator, scope, voltmeter) and basic knowledge of how to avoid killing yourself while working on high voltage circuits.

I'm not trying to be harsh here, I just don't want you dead or with a smoking pile of expensive parts where there used to be a functioning amp.

[DigitalJunkie]

The first bit of advice:
Be careful!!

This amp has a high B+ voltage.
Read up on High Voltage Safety

[Miniwatt]

You do realise what gigantic voltages are in that amp?
Not something for a beginner.. Watch out for those caps..

[dantwomey]

Originally posted by SY
What is it that you're specifically trying to improve? Or is this just a matter of, "I can't keep my hands off this, please tell me something to do which will keep me occupied?"

If you're attacking a commercial design, it first helps to understand it. If you can't point to any resistor at random and say what it does, you ought to keep your hands out of it until such time as you do. Presumably, the guy who designed it had at least some minimal level of competence, so you're not repairing or correcting obvious errors.

A commerical product is usually a compromise between cost of components, manufacturing costs and what product price the market will support.

My approach to date has not been to redesign anything but to replace certain components with better quality 'audiophile' grade components that wouldn't have been commericially viable. An excellent example of this is my participation in the extremely popular Marantz CD63 & 67 mods. I followed this thread and performed most of these mods on my CD67.

I have the experience and tools mentioned below. And, I always jokingly say the NICE thing about working with high voltage is that if you make a mistake you know INSTANTLY!!!!!!!!

MOST importantly, you need to have the right tools (sig generator, scope, voltmeter) and basic knowledge of how to avoid killing yourself while working on high voltage circuits.

I'm not trying to be harsh here, I just don't want you dead or with a smoking pile of expensive parts where there used to be a functioning amp.

The two things I would probably like to look at is any reasonable power supply improvements I could make and perhaps some better quality components (ie. replace C103 with a Hovland or Jupiter) in the signal path.

Regards,
Dan

[SY]

I'm probably not the right one to help you with fashion accessory questions but no doubt lots of others will chime in.

As far as power supply work, what's the inadequacy in the power supply that you're trying to fix? I'll stress again, if you're not VERY experienced with high voltages (there's probably 700V or so on that B+ rail), don't even THINK about messing with this.

[Bas Horneman]

And, I always jokingly say the NICE thing about working with high voltage is that if you make a mistake you know INSTANTLY!!!!!!!!

Not necessarily. Most likely you will be dead.

Jupiter

Probably not a good choice because of the heat (very likely) under the chassis.

But yes caps are the most obvious choice for "fashionable accesoires" However I was suprised (positively) when opening up a Chinese built commercial amp when I saw the good quality parts.

PS. The 300B tubes according to the schematic sure don't look like 300B's in the picture.