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Scott 299B Restore

So, Dave, I went back and looked over the schematics and, of course, it's all crystal clear after your explanation of the difference between active and passive tone controls. The NFB circuit is evident in the 299B circuit. You see that the X-200 (and 400) controls are basically a filter in the signal path. The former has gain and the latter only attenuation. As they said in the movie, "are we learning now??" Yes.

So, it appears the Fisher X-202B had active controls, like the Scott 299B, but I don't see them in any of Fisher's other designs (X-101, X-202, X-202C, X-200).
Thoughts about why Fisher seems to stick mostly with passive controls? Also, is one scheme generally better than the other, or does it depend? ('it' usually does, I guess)

Thanks!
Dave
 
Dave -- Fisher used active tone control designs in their upper tier units, and passive designs in their lesser models. Therefore, the entire stereo preamp line from the 400C through to the 400CX-2 all use active controls, as do the 202 and 202B integrated amplifier offerings. Of course, the EL34 based X-1000 integrated amplifier uses them, and so does the excellent 202T tuner/preamplifier. When vacuum tube models were in their waning years, the X-202C dropped this more expensive approach, as did the X-200 that followed, with passive designs finishing out the vacuum tube pieces.

The active approach is generally regarded as the optimum way to go, as with it, the slope and boost/cut levels can more precisely controlled, as can the on-center flat performance as well.

Dave
 
Got it. It does seem that Scott used active controls in most of their 222 and 299 series amps, among others. Thanks, Dave.
 
Great thread! It's been a big help to see tips for this amp.
I just got a 299B off Craigslist and have started restoring it. The first filter cap in the B+ was shorted to ground; after changing the power supply caps I started it up gingerly and am getting volume out of both channels. At the moment Channel A lacks high end, but I suspect (hope) that as I go through the amp those issues will go away.
Over the past few weeks I have been mulling over how to best replace the capacitor cans ... stuff them? Replace with new ones? Nope. Though it's tight in there I'm 100 percent sure I'll have plenty of room to wire all the new electrolytics under the chassis; I'll post pictures as I go along.
So far I've replaced C1A/B (20 and 30 paralleled) with a single 47uf/450 F&T axial. I also replaced C2A and C2B with F&T axials, I moved them around a bit where I could find space, then grounded them back to the original cap can grounds to prevent any ground loop issues.
I'll do the same with the rest of the amp, trying to keep things as tight as possible with as little change in lead dress as possilbe. The two 100/100/10 cans with positive to ground should be easy as the replacement caps are tiny. The final can, with two 20/450s and two 25/25s should be pretty straightforward too.
Love this amp. It's a work of art!
 
dcgillespie said:
Dave -- Fisher used active tone control designs in their upper tier units, and passive designs in their lesser models. Therefore, the entire stereo preamp line from the 400C through to the 400CX-2 all use active controls, as do the 202 and 202B integrated amplifier offerings. Of course, the EL34 based X-1000 integrated amplifier uses them, and so does the excellent 202T tuner/preamplifier. When vacuum tube models were in their waning years, the X-202C dropped this more expensive approach, as did the X-200 that followed, with passive designs finishing out the vacuum tube pieces.

The active approach is generally regarded as the optimum way to go, as with it, the slope and boost/cut levels can more precisely controlled, as can the on-center flat performance as well.

Dave
Click to expand...
This is an interesting observation Dave. I noted recently that Mapleshade claims of their Scott 222C mods, 'We bypass all the preamp/tone control active stages and replace them with a vastly better-sounding passive preamp stage.' (http://www.stereomojo.com/ScottMapleshade_222c_Amplifier_review/Scott_Mapleshade222cReview.htm)
 
Diverted,
Glad the thread is helpful. As you can see in my earlier posts, replacing the bias can with individual electrolytics under the chassis is very do-able with a little care. Good luck with it. These are superb integrated amps. I really enjoy mine.
Dave
 
Dave451 said:
Diverted,
Glad the thread is helpful. As you can see in my earlier posts, replacing the bias can with individual electrolytics under the chassis is very do-able with a little care. Good luck with it. These are superb integrated amps. I really enjoy mine.
Dave
Click to expand...
Thanks for all the guidance! I was pretty intimidated at the thought of restuffing cans; glad I don't really need to.
 
Restuffing cans is actually easier than it seems, but it's best to practice with one that you don't need to reuse first.
 
Dandy,
One day I'm going to try it! There are some good how-to threads on restuffing caps. The Hayseed Hamfest and CE units are terrific, but pricey. I used the JJ units for this 299B and really liked them, but some would rather stick to the vintage look, and restuffing may be the most economical route to it. I liked the way the black JJ cans looked, though; especially if you don't use clamps.
Dave
 
I mostly restuff if there isn't room under the chassis. Otherwise it depends on your view of restoring, and of the cosmetic condition of the unit in the first place.
 
Dandy -- This comes down to the old personal preference again. The original Scott design was based on electronic accuracy, with tone controls that reflect quite excellent flat response when centered. Data and graphs are given to support the performance of their design, which was built to the universally understood and accepted definition of what the term "high fidelity" originally embraced. Today however (as with most things), the old definition has gone out the window, and has been replaced with glowing subjective testimony (of understood personal knowledge) as to what a "vastly better sounding" design sounds like. No support data is given -- just that you should trust their ears.

Their design may in fact sound better to them, and/or even a lot better to a lot of folks today. I'm hardly trying to say that it doesn't, or in any way cast doubt on the Mapleshade product. What I am trying to say though, is that without their offering any scientific data to back up exactly how their modified units compare with the original product, all you have to go on is their testimony as to what they hear. For some, that's fine. For others, keep your eyes and ears wide open!

Dave
 
Dave G--I completely agree. Your second paragraph applies to many other areas in the world today too!
 
And as Dave says, this business of removing tone controls and major wiring modifications just makes me cringe. Unfortunately, some of our members are following the recommendations of other members who purport to be experts in the field of amplifier design. What comes to mind is that Scott "Kinda" knew what they were doing when the designed these wonderful amplifiers.

Some think that adjusting the tone control or using "Loudness Compensation" is heresy. Just because those switches and controls are on the amplifier does not mean that they have to be used. An amplifier is the possession of the user and he/she can adjust as one sees appropriate.

Gosh, I don't mean to sound like an old fart, but keeping these amplifiers in tip-top condition, "AS DESIGNED" is of the utmost importance to me. If nothing else, remember that we will not be the ultimate owners. Some day down the road, another person will own them. We won't live forever and if major modifications are made, however misdirected, they may not be reversible.

BTW, for what it is worth, I use tone controls and the Loudness switch!
 
+1 on tone controls and loudness contour!

I was looking for a cabinet for my 299B (subject of this thread) and talked to one of the principals at the aforementioned company. A very knowledgeable and passionate fellow when it came to the Scott amps and fun to talk with. He offered to modify my 299B, but because of my prior (excellent) experience with the model I intended to keep it stock for and I'm glad I did.

His philosophy seemed to be that you can't possibly measure all that's important with sound because 'sine waves don't tell the whole story' and that much of the really important stuff happens in the brain--i.e., you can hear things you can't measure. I have a hard time with that and similarly am skeptical that, as far as Scott amplifiers are concerned, there are many who would have a better grasp of these designs than did Mr. von Recklinghausen. (I think Dave G's work, particularly on the Fishers, is an exception!). One rationalization seems to be that 'they made compromises to reduce costs'--again, skeptical. Another seems to be "keeping the signal path simple." I suppose there are merits in both ways of thinking, but I usually come out on the side of stock design.

Then again, there are folks who pay $10K for speaker cables and swear that power line fuses sound different depending on which direction they're pointed, so I guess it takes all kinds! Heck, maybe I am an old fart.....
Dave
 
Nothing wrong with old farts. I'm listening to Keith Richards (Talk is Cheap) right now. Late 80s vinyl, but so well performed and recorded.

Kv, I like your reminder that we are not the ultimate owners of this special gear. I sometimes wonder about who had my gear before me. As some of it is 60 years old, they may well have passed on by now. It's nice to think of handing it on in good order one day.
 
Here is a "Secret". Watch for solid state tuners, amplifiers and receivers on sale at "The Auction Site". If you do your homework, many of the solid state follow on items fit the same size "C" cabinet that our LK-72. LK-48, LT-110 etc. equipment. Often, those items go for a song and often have the Scott walnut veneer cabinet.

Got many myself that way...
 
I got a nice Scott tuner cab by buying a 314 (mono) tuner for not much and using the cab for my 350B. Still have the 314, which is quite a nice sounding tuner.
What models of Scott SS gear have this cabinet size?
 
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