Category: Dynaco stereo 400

Dynaco stereo 400

30.10.2020 By Gukree

Log in or Sign up. Dynaco Stereo - where to start? Messages: 3, Location: MA. Hello everyone. While visiting a local audio store, I spotted a Dynaco Stereo in their used gear section. I'd never seen one 'in the flesh', but had heard a fair number of good things about it and the rest of the series over the years.

The amp had a mystery wire sticking out of the side, which I later realized had once been connected to a fan of some sort. Also, the vast majority of the component-level work I've done on vintage gear has involved tube equipment. Regardless, I feel good about my prospects of being able to fix this ST, since it was designed to be built as a kit, and lots of documentation is available about it. Also, I have a fair amount of test equipment around here, including a transistor checker.

Anyway, as mentioned earlier, I was able to give it a listening test before purchase, which showed some hopefully minor faults. When powered up for the first time, the pilot lamp came on, as did both of the lamps behind the smoked plastic window, which I later learned are the DynaGuard indicators the switch was turned to OFF, and cycling the switch through the settings has no effect on their illuminationand the relay clicked.

dynaco stereo 400

Once fed with a signal, I got audio from both channels, though some distortion could be heard in the right channel. When I checked the DC offset, the right channel showed mV when first powered up, which later fell below -1mV, while the left channel shows a pretty steady mV. Granted, I didn't give it a full 15 minutes to warm up, but things seemed to get settled in fairly quickly.

In summary, my question is as quoted in the title. As mentioned before, I have little experience working on solid-state equipment in general, though I think it's time I learned how. My guess is that new capacitors are needed, along with whatever drifted resistors there may be, but I'd rather not just shotgun everything or replace all the boards with new ones as shown in my ST restoration articleI like to give the stock circuitry in these things a fair shake if at all possible.

Anyway, here are some pictures of the amplifier: The front panel. Seems to be in pretty good shape overall. The rear panel.After the purchase. Over the next few days. I will be in touch through out these stages with pics and information. This document will be included in the packaging.

I simulate the original packing material. I use a custom made three-layer double wall box. I put two inches of dense Styrofoam across the bottom. I place it into the box on the two-inch bed. Each piece is glued against the walls of the heavy-duty box. I glue a large sheet of cardboard on the top of the thick piece that is used to hold down the item.

I then glue the box flaps to this surface and each other flap. Then off it goes. All have arrived safely. You will have a bit of time unpacking but it will arrive safe. This old amp has the power and the headroom to impress, even today!

dynaco stereo 400

Awesome damping factor and a truly "invisible" sound - very little "signature coloration" if any! I suspect it lays out more than rms per channel. Thanks for asking. I do like to explain this to customers. I usually get these questions about once every two months.

That is my best attribute. Because of my packing, which involves insurance as well, all have arrived A-ok. Please take a brief look at my process.

WAY ahead of it's time!Hey guys, some of you may remember this ad from about a year ago. I listed this amp on eBay and it sold to a gentleman in Texas. We agreed on a price to replace the capacitor with one of his choice and he did so.

Dynaco PAT-5 & Stereo 150 Pre-Upgrade Sound Check

The buyer reported back with a million tests he ran on the amp and said everything else was good and the tubes tested strong. Then, he said the bias adjustments were not present. I had no idea these were missing although after the fact, and once I knew what I was looking at, the photos clearly showed there were no bias adjustments present. I used the amp for years without adjusting the bias, apparently. This is why I stick to solid state equipment.

Dynaco Stereo 400 II Amplifiers

At any rate, this transaction didn't end well and I ended up with the amp back at my house. The photos show the old capacitor in place.

If a buyer is serious, I can email you updated photos showing the new capacitor installed. Below is some information from a Stereophile review from years ago. The glowing Stereophile review below sums up what a beautiful sounding amp this is.

Hi Joe, thanks for reaching out. I don't want to ship this amp again With that said, I wonder if we could possibly use the buddy system on this?

The Stereo 400, Stereo 416, and Stereo 410

I don't keep track of when members are meeting up and things like that, but assuming COVID restrictions ease a bit in the next month or so, maybe we could somehow get the amp to you in Carolina?

The is a screwdriver adjustment potentiometer, right behind each power tube, clearly visible in the pics. You would need to have the bottom off and use a meter to read the correct values. You measure between the ground and one of the pins can't remember at the moment. The is no indicator present, as you can see on the under chassis pic. Aren't the "bias indicators" located in front of the tubes used to take measurements without removing the bottom cover?

Thank you for taking time to explain, Marvel. I sincerely appreciate your time, I understand exactly what you're saying. Have a terrific evening. I believe Marvel did a nice job explaining what's going on The original St had a resistor between pin 8 and ground. Measuring the voltage across it gave you the same numeric value as the bias setting.

Maybe Maynard could help you figure it out with a couple good pics of an output tube socket and pot area.

Dynaco Stereo 400

Yes, this is a very easy adjustment. However, the possible exposure to lethal voltages makes doing it unsafe for inexperienced users. This amp is still available. Lots of interest, but no cash in hand yet.It's a modified DynacoW per channel. I have a review of it from Audio Amateur in aboutand they thought that it was a good amp, but too expensive for what it was a relatively minor modification of a moderately priced amp.

Solid state, pretty good for the era, but no Krell. If it's cheap enough, it might be a deal, but I'd be willing to bet you could get a more modern Hafler with similar power specs and better THD for about the same money. I can't say I've ever heard the Van Alstine mods for thebut an unmodified is a perfectly respectable amp.

IIRC from the review and I'll dig it up if you want me to-- I have AA's 70s CD collection, which is fascinating reading even for non-tinkerers-- it includes tests on both the modified and unmodifiedthe unmodified Dynaco was a class B in Stereophile back then.

Search form Search. Show Munich More Reports. Log in or register to post comments. October 2, - pm. Last seen: 8 years 3 months ago. Joined: Dec 13 - pm. Hi What does anyone know about this amp? Is it a recommended item or to old to be useful? Thanks Alan. October 5, - pm. Last seen: 2 months 2 weeks ago. Joined: Apr 18 - am. DUP actually could be useful here, but here's my shot at it: It's a modified DynacoW per channel. Create new account Request new password. Leave this field blank.

Gordon Holt. Shop Recordings Buyer's Guides More.Dynaco Stereo Power Amplifier. Posted: Mar Sat 22, pm. Hi All, I am new to the forum and joined because I am in need of some help but don't know where to turn. My grandfather passed away in the early 90s and I inherited his Dynaco Stereo Amp. It worked when I got it and then the power went dead.

I would like to have it restored and made functional again. The problem is, everyone I have asked about fixing this says they don't work on solid state Dynacos. Does anyone out there have a suggestion of someone who might be able to fix this for me? Thanks, Brian. Where are you located? We have lots of people who fix things, but round-trip shipping could easily cost more than the repair.

I am located in CT.

What type of work do you do? Are you a company? Feel free to private message me. No, not a companyjust a bunch of people who like old radios. Hopefully, someone in your area will chime in. You might also join audiokarma. My recollection is that these amps used those annoying square fuseholders which would propel the fuse cap across the room or into never-never land when you touched it wrong Posted: Mar Sun 23, pm.

Or post in the "general" section of Audio Asylum asking for a local shop. You don't even have to be a member to post. Those are still used often and parts are available and most shops will work on them. Good luck ET.

dynaco stereo 400

Posted: Mar Mon 24, am.The Dynaco Stereo is a basic power amplifier employing all silicon solid state devices. They include 46 transistors, 47 diodes, 2 silicon controlled rectifiers, and 4 integrated circuits. The series-connected output circuitry is of full complementary symmetry design. The entire main amplifier is direct coupled. It's measured distortion levels approach the threshold of the most exacting laboratory test equipment, not only at the commonly specified full power ratings, but more importantly at very low power outputs as well.

This is the result of circuit techniques which eliminate any discernible crossover notch at low levels, and it contributes in large measure to the Stereo 's freedom from listening fatigue. It's lucid, utterly uncoloured neutrality reveals delicate nuances and musical shadings in the best program material - one result of achieving unconditional stability with varying loudspeaker loads.

Implicit in the design of a superb high power amplifier is the responsibility to include superior techniques of protection for both the amplifier and the speaker load, if long-term trouble free operation is to be achieved. To this end, Dynaco has included more separate protective systems and features than have ever been employed in such a product.

These include an AC line circuit breaker rather than a fuse ; four separate power supply fuses; electronic volt-amp limiting to ensure safe operation of the output transistors; independent high temperature cut-outs on each channel, which are mounted directly on the output transistors to assure maximum sensitivity; over square inches of radiating area for the mammoth heat sink; provision for accessory fan cooling with optimum efficiency; delayed turn-on to eliminate loudspeaker thumping; relay protection against DC signals at the output; load speaker protection fuses accessible on the front panel; input level controls to reduce sensitivity; input filters to control the bandwidth; and the exclusive Dynaguard adjustable dynamic power limiting circuit to protect the speaker load.

Dynaco stereo 400 amp

The Stereo was engineered to accommodate a wide range of specialized needs in studio, laboratory and industrial applications, as well as in the home. It has been designed as two independent watt at 8 ohms amplifying channels with a common power supply having a high degree of inherent regulation. For special requirements, a technician can easily convert it to a monophonic watt at 8 ohms output.

Accessory provisions for mounting on a standard 19 inch rack, an alternative front panel which includes two output meters, a cooling fan, and an alternative power transformer for international AC line voltages are available at additional cost. If you have any problems opening files please read the download FAQ. All files are provided under strict licence and reproduction without prior permission or for financial gain is strictly prohibited.

If you have additional documentation please consider donating a copy to our free archive. Login or register to post reviews. Reviewed Jan 12th, by novy I had this amplifier for many years. Also Dynaco preamplifier and Dynaco loudspeakers and Dual record player. Very good sound. There were two fusions on the front. I think I had fusions of size 2 amp. To protect the loudspeakers when I blasted Pavarotti. I want to thank who ever contributed this information.

I just purchased this amp, and find this information Very helpful. Thanks again, moduck. Erno Borbely. These amplifiers have a very nice sound and powerful performance. Jim Bongiorno had a hand in the design of the Stereoas well. That seemed to be a significant sound improvement.Free Shipping on All Orders! Contact Account Shopping Cart.

July in Electronics. Hi polks Should I pull the trigger? The amp has faulty lefty, likely a known bad soldering with this amp. Any 2cents is appreciated. July I bought a basket case for fifty bucks and had it recapped. New front fuse holders. F1nut Posts: 44, Buy something that you know works.

Political Correctness' July edited July They -- require a fair amount of TLC to be brought to a functional state. I've got one sitting in the basement. I have plenty of spare time -- and I still don't have the inclination to look into it in any way, shape or form. Hardy runs the corner to chase the lob! Aaand gives an underhanded slapback to his opponent! Brilliant strategy! The was, in a very literal way, the progenitor of the Ampzilla I think if one were looking for a vintage watt soiled solid state amplifier, the would be a better choice than the The 's pretty crude.