Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: TIMBO on August 21, 2015, 11:07:32 pm
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Hi guys, got a bit of a bug for this SS stuff.
After hearing the Vase hybrid with a SS preamp, I started to think what it would sound like connected to an old school PA.
I know jack about transistors, so I need all the help I can get.
The preamp looks pretty simple and I know it works.
I wanted to connect to a PA of about the same vintage(70's) and found this http://archive.siliconchip.com.au/cms/A_30285/article.html (http://archive.siliconchip.com.au/cms/A_30285/article.html)
All the transistors are still available which is great.
But as for connecting the two together is a bit of a stretch for me, from what I can see I would drop the driver stage off the preamp and connect the volume pot directly to the input of the PA.
OR if any one has some brilliant ideas go for it. Thanks
(http://i761.photobucket.com/albums/xx254/Timbo-08/005%203_3.jpg) (http://s761.photobucket.com/user/Timbo-08/media/005%203_3.jpg.html)
(http://i761.photobucket.com/albums/xx254/Timbo-08/005%202_1.jpg) (http://s761.photobucket.com/user/Timbo-08/media/005%202_1.jpg.html)
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Are you talking *stitching* 2 existing units together, or building from scratch? Stitching should be easy enough, building from scratch will be a challenge.
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Hey shooter,The PA was a kit from the 70's and I don't think they are available any more.
I would like to build from scratch but it would be a lot of work if it didn't work, I may try it on a bread board. thanks
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I did a lot of transistor stuff back in the80's/90's and noise *issues* was the biggest pain. the same "rules" as tubes for lead dress, layout etc still apply. My best success was bread boarding, but it might take me 10 trys moving this Q1, bending that wire, yadeda. once it was good, I'd etch a board that looked JUST LIKE my breadboard(s) even measuring distance of a wire before it made a 90degree bend.
Good luck, patience IS a virtue :icon_biggrin:
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The SC480 is not much different from a LM3886 chip-amp. Neither has a real "sound". The LM3886 is *much* better protected against stage abuse. You can buy LM3886 kits on eBay for very little money. (Most of the money goes to power transformer and heat-sink.) Or, cut-up a half-decent transistor stage-amp from the pawn shop.
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Thanks guys, As luck would have it a mate was cleaning up some old stuff and found this power amp from one of these http://www.ozvalveamps.org/diason.htm (http://www.ozvalveamps.org/diason.htm) (unknown 3). Could be 40-60w and has the 2n3055 power transistors.
I says that it had a tube preamp. :think1:
It may pay to have a dual preamp. :think1:
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That looks like a way better option than rollin your own from scratch.
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Another option is the "organ amplifier" search on sneezbay. I bought one labeled JC Penney and this thing is a SS work of art with "Made in Holland" Amperex power transistors, Sprague orange caps and some cool germanium driver trans. It's stereo so that adds another dimension for possible designs. I guess about 40 watts x 2. I think I paid 20 buckolas for it.
:icon_biggrin:
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That's COOL. I'll keep a lookout for something like that.
On further investigation of the power amp, I think it would be much better used as it has a high voltage taps that can power some preamp tubes. :icon_biggrin: