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Old 2nd October 2001, 07:50 PM   #1
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I am considering purchasing a Dynaco ST-410 200 wpc amplifier to run my Acoustat Spectra 1100s. I am not an expert on amps and I haven't found too many reviews of this amp. Has anyone ever used this amp? Is it a good amplifier? The price would be under $200, and I was wondering if this would be a good purchase?

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Chris
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Old 3rd October 2001, 12:30 AM   #2
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Not a good amp for electrostats.Find a Dynaco ST-416 or get a Hafler DH-500.
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Old 5th October 2001, 04:39 AM   #3
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I have no opinion on ST-xxx amps, but can certify that the Hafler DH-500 is bulletproof. I've seen & heard them on Acoustats, Stax, Quads, the works. They just keep going.

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Old 5th October 2001, 08:36 AM   #4
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The ST-400, ST-410 have only four outputs in series.The maximum rated Ic=16A and the Beta=15~60@8A .The RMS I^2=32 therefore the amp may put out 64W at 2 ohms, 128W at 4 ohms or 256W at 8 ohms before getting into trouble.The ST-416 has double the number of outputs and therefore can do four times the power into low impedance loads.A DH-500 can do RMS I^2=288, or 576W at 2 ohms, over twice what a ST-416 can do.Electrostats can and do drop down to 2 ohms at high frequency.One could install Semelab BUZ900D/905D in a ST-410 and get an RMS I^2=511 for about $120.This would involve re-wiring the output stage to parallel with the FETs.
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Old 10th November 2007, 03:47 PM   #5
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Question Dynaco (Dynasaur) ST-410

I also have a Dynaco St410 (I actually have 3 and a ST416 that is a basketcase)and a pair of Acoustat 1100's. I have recently aquired a Dunlap-Clarke Dreadnaught 1000 but, it needs repair and I am trying to aquire information to repair it. So that leaves me with the Dyna's. My plans for the Dynaco is to double the power supply caps from 10,000mfd. to 20,000mfd. Change the driver transistors from TIP41C/42C to MJE15030/31, and change the outputs from 2N5630/6030 to MJ21193/94. My choices in transistors is based on posts that I have read in this forum and the SAE forum on Yahoo. I have read an article in Audio Amateur about adding servo control to the amplifier ,why? why not? I aslo plan to use the MJ21193/94 devices in the Dunlap-Clarke and an Adcom GFA1. Now back to the Dyna. Can I expect to see an improvement in low impeadence loads with the before mentioned changes to the Dyna? What kind of load can 2 pair of MJ21193/94 devices handle? Same question for 4 pair that would be used in the Dyna 416 and Dunlap-Clarke? Will the protection circuit in the Dyna 410 prevent the amplifier deliver the current required to drive a low impedience speaker? I have seen a post sugesting parallel outputs for the Dyna with the MJ21193/94, why? This is a learning experience for me. Please show me the math. I have built kits in the past but my electronics skill and knowledge doesn't go much farther than a basic electricity class in college, a life long curiosity about what is in the box, and how does it work.
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Old 12th November 2007, 10:36 AM   #6
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The MJ2119X are still only rated at 16A max, and the beta is still only spec'd at 8A.

It doesn't matter what outputs you put in a 410, it doesn't have the heatsink capacity to drive less than 8 ohms (well), much less 2 ohms.
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Old 20th November 2007, 12:05 PM   #7
d3imlay is offline d3imlay  United States
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I used to test the driver boards for the "Black Box 410". Probably tested over a 1000 of them. I hated the circuit, for no good reason. It was developed before there were good high voltage, high current BJT's. I don't see much advantage in changing outputs to the mj21xx.
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Old 22nd July 2010, 05:08 AM   #8
THGTCHR is offline THGTCHR  United States
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Default Dynaco ST-410's

I am a life-long fan of Dynaco gear. However, Dyna's large solid-state amps were fires waiting to start. I blew up two 410's in a week while trying to drive a pair of Infinity RS IIIB's. The 416 was better, but still...

If you want a Hafler designed amp, ditch the Dynas and go with a Hafler DH 500. They are truly bullet-proof. The 500's benefit from larger caps in the P/S, but they are about as stable as big amps get. They sound pretty good too, especially if you upgrade some of the caps on the driver boards and do a few other basic updates. Do that and you will never hear the distinctive "WHAP!" a Dyna amp makes when it dies, or smell the unforgetably pungent odor of smoked electronics.
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