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Old 1st August 2005, 04:20 AM   #1
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Default Looking for first SS amp idea, have PS

Hello, This is my first post to this forum. I've built a number of tube amps from scratch so I'm not a total newby but don't have any SS experiance. I already have a chassis and 36VDC power supply from a Oregon Audionics stereo amp. The power trans is a Western Transformers wti#1820/code#977 into a bridge rectifier and then to two Sangamo 15,000mfd at 60VDC caps. The power trans and the caps are fine and that's where I'm getting the 36VDC. Well, each cap has 18VDC across it. The heat sink has 4/channel Motorola 2N5630. The amp looks like a pro sound amp and I can't find any info on it except that the company's founder now works for Fosgate. Can anyone direct me to a proven DIY design that could make use of this PS and heatsink? I've been looking at the Krell thread and while I know that PS won't work for that amp I'm hoping that someone has board available for a similar amp project. All my speakers have fairly high eff so I don't need that much power.
Thanks in advance for any help, this is a very cool site, John.....
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Old 1st August 2005, 04:41 AM   #2
Stocker is offline Stocker  United States
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Do a search on this forum for "gainclone" and stand back.

If you don't mind the power waste, the Pass Labs forum has some high-quality, proven designs in the form of the Aleph and Aleph-X series.

Try those for a start.
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Old 2nd August 2005, 09:03 AM   #3
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Stocker, Thanks. I think I might look into the DoZ also. I think my donor amp was about 100w/ch so it should have enough guts for 10watt/ch class A. Does anyone reading this know if DoZ will work at 36VDC? I really don't need another 75-125watt/ch SS anp as I have two I like now. A little class A sounds like it might be fun.
John..........
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Old 2nd August 2005, 11:08 AM   #4
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Quote:
Originally posted by whatsnext
Stocker, Thanks. I think I might look into the DoZ also. I think my donor amp was about 100w/ch so it should have enough guts for 10watt/ch class A. Does anyone reading this know if DoZ will work at 36VDC? I really don't need another 75-125watt/ch SS anp as I have two I like now. A little class A sounds like it might be fun.
John..........
Hi whatsnext.

I run mine at around 32 volts (~24 Vac) and that seems OK. Rod's schematics show 35VDC. There were some lengthy threads about the DOZ about six months ago. Do a search. There were a few modifications to ensure reliablilty. A little class A sounds good and feels hot.

Rod's recommends a CRC PSU, so you will probably drop a volt or 2 across R if you mod your PSU a little.

Good luck
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Old 2nd August 2005, 10:15 PM   #5
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Hi whatsnext,

I'll second Greg in trying out the DoZ. It is a great little amp that will run perfectly well at 36V. This weekend I just lowered the voltage from my DoZ from 40V to 30V and although the output is reduced by 50%, in combination with my Buschhorns (Fostex Fe108ES rated at max 8W RMS) there is no subjective difference. Might be even a little more detailed because of more careful matching of the bias from both channels. Even though the dissipated power is down from 136W to 'only' 78W it still runs hot. Just takes a little longer to become too hot to touch... Did not do any modifications to limit current rush since I am a little bit afraid of the power-on thump that results from the mod in combination with the Fostex drivers.
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Old 2nd August 2005, 10:38 PM   #6
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Thanks guys. The DoZ looks like it's going to be 'it' then. At ESP's site he shows 40 volts after the PS so I'm going to build it as is and see how it goes.
John..........
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Old 3rd August 2005, 04:07 PM   #7
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whatsnext,

Of course there is a reason why I downscaled to a lower voltage, the most important being that mr. Elliott recommends not to use 40V anymore but keep a maximum of 35V due to the SOA (and therefore reliability) of the endstage. Furthermore, this amp really gets hot so prepare for big (!) heatsinking or just scale down the PSU a bit. It is designed for sophisticated and nice amplification. For partylevels shop elsewhere. HTH.
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Old 3rd August 2005, 04:46 PM   #8
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Thanks Doc, Most of my speakers play loud enough, for me, when driven by a SE EL84 amp. I'm going to try hardwiring one channel of the amp and see how my PS responds to it. If it holds up I'll try stereo. The heatsink on this amp is allready pretty large but if it gets too hot fabbing up a larger one should not be an issue. The whole back face of this chassis is one big sink but bolting on a bigger one is pretty straight foward. I just bought some of the output devices. Once they get here we'll see how it goes. I'm sure I'll have more question.
John......
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Old 3rd August 2005, 06:36 PM   #9
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John,

Good luck and fire away the new questions when they pop up!
I am sure you will enjoy the simple but effective design of this amp. Did you go for the MJ15003 or the 3055 transistors?
Btw. Just to warn you: in the schematic C3, the decoupling cap between endstage and loudspeaker is not drawn. It can cost you dearly when you forget to include it in your enthusiasm to connect a speaker and listen to some tunes. Ask me how I know.
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Old 3rd August 2005, 07:03 PM   #10
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Doc, What blows up? The amp or my VOTTs? I found 24 of the 2N3055 for $16.00 delivered. Seemed cheap enough. Are the MJ15003 so much better?
John.....
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