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Building a Dave Gillespie SE-1 Amp

Wharfcreek said:
I got my pilot light installed. At this point, if I EVER go to RadioShack again it will be too soon! That place has gone so far down hill it actually wrecks my day to go in there. Aside from having virtually NOTHING of any use any more.....the place was playing this God-Awful rap music through some goofy system and had it set up IN THE FRONT DOOR if you can believe that! They actually had a double door and had one side blocked with this 'thing' that was playing something that about turned me 180...never to return. And, I told the guy that as I walked out the door with a small 110V pilot light and 1 pak of 10 ohm resistors. I doubt I'll ever go back..............
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Hey Tom, I had to laugh at your rant. Very familiar to those of us in the UK who use a local equivalent. Our local guys only stock 2 of any component (in their limited range), so if you need 4 resistors, you'll probably have to wait for them to post you the other 2 or 3, FOC, in a huge padded bag. But if you order online at the start, there is a £3 shipping charge. The system is designed to get you to go to the store. Maybe they have a deal with the music promoters?
 
Dandy, glad you found some humor in my rant! I suspect I'm not alone with my feelings here about 'the Shack.....'. But, I'll concede to your situation there in the UK as being worse! I feel for you! At least we have one good parts store here in my area. It's about an hour away and involves travel on a busy main highway around the city of Baltimore. But, if you travel mid-day and avoid the work rush-hour traffic, you can make the trip there, back, and have time in the store, all in about 3 hours. If you're like me, you know a good spot for lunch along the way.....so a trip can double as an 'outing' for a meal. Hey, you've got to make the most of these things!! All I can say is Rat Shack has lost me forever!! Tom
 
Tom -- besides using the correct FB cap, you can always try upping the value of the grid stopper resistor you added, but I wouldn't go over 10K in that position. However, I'd get the original circuit built correctly first, before doing anything to tame the layout of your particular build.

Dave
 
Hello Dave, Tom, and others.. I joined Audiokarma a few months ago when I found a maggie on ebay. Brand new to hacking these things, I was looking for a project and found Dave's thread about the maggie. I ordered all the parts based on Dave's post and finally tore into it yesterday. I followed the plan to the tee.. new opt's, choke, etc. and I am wonderfully astounded at the sound quality. Superb detail and very pleasing to the ears.

I tested the maggie before any mods and it seemed to sound ok, with colored tones, but distortion was evident in low frequencies.

Not sure of what the finished product would sound like, I plodded ahead - testing the difference in sound with every step. The new opt's made a nice difference into 8ohm Onkyo speakers but I went ahead anyway - just had to hear what this thing would sound like after ALL the mods were done.

When completed, I was a bit dismayed at the fact that I had distorted tones (verified on the bench with scope.) I added the grid stoppers (1k) and man!!! This sounds so articulate. I can't find any distortion and the amazing little amp "sings" as Dave put it. For a small room, this amp puts out plenty of power. Any volume level, any type of music just sounds fantastic. I even played some Dolby 2.0 movie clips through it and wow... just wow. I also hooked up a 100w powered sub to add a bass kick since my drivers are only about 5"...

Mine is not very pretty (left everything stock looking) but I would love to tear this down and redo the chassis with some nice paint, etc.. to really make a nice little show piece out of this thing.

My HUGE thanks to all of you who added to the very informative thread and I would encourage anyone thinking about this to DO IT!!! Can't wait do find another project in the tube realm of sound.

-Brian in Virginia
 
Brian, Congratulations!! Great fun, isn't it? Glad you got it working properly and can now attest to the really true quality of this little amp. Dave did a phenomenal job with his re-design!! Funny, I too had the same issue with my first attempt at a build of this amp. And..... with the addition of the grid-stopper resistors, my amp was 'fixed'...... and sang beautifully! It was a great feeling to see the fruits of my efforts pay off......and I'm sure you felt the same way.. Now, if the 'bug' has bit you, you'll be looking for your next project! Good luck......and welcome to AK!!

Tom D.
 
Nice job Cruz! Yours and Tom's have been the only reported cases where HF instability plagued your build -- but obviously it can be an issue in certain builds. I never had any issues in my development model, but no two builds are the same, even if lead placement is identical. The 1K grid stopper has clearly done the trick in both cases. When I get a chance, I'll see what it's installation does to the supersonic characteristics of my own unit and report back.

Glad you got it going and enjoy it!

Dave
 
Thanks Guys!! Now it's been many hours in front of the little amp, and I'm still so pleased with it. I'm thinking about a scratch build of the same amp - this would be my first scratch build. I would love to have one downstairs for listening in the living room. I've added new speakers - Polk RTiA 3's (not high end, but easily in the budget,) and after about a week of listening, I think they sound great with the maggie..

I also just bought a Magnavox 197-20 SE and I'm looking to do a similar re-build of it.. any suggestions for a forum link to some good additions/mods to it? I'd like to change the OPT's to 8 ohm like the 8610 mods, and I'd need to do some calculations, and I want to remove the balance control, tone circuit, add a choke, etc.

Thanks to all of you!

Brian
 
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