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Dynaco ST-70 Series 3 Tube Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 98 48.8%

  • 2. Not terrible (postman panther)

    Votes: 69 34.3%

  • 3. Fine (happy panther)

    Votes: 27 13.4%

  • 4. Great (golfing panther)

    Votes: 7 3.5%
  • Total voters
    201
Rottmannash said:
hope you don't want to take a corner at speed...
Click to expand...
I guess that you haven't seen most Harley Davidsons then, only the "Comfort Cruisers". Yep, even some "Off Roading"!
1720794751968.png

1720794832466.png

Smokey Mountain Harley-Davidson Scrambler ride​


Harley-Davidson Pan America review on Harley-Davidson Test Days 2023 in Slovakia!!!
 
tubesguy said:
It doesn't take much lean to cause the floorboards/foot rests to scrape. That can be unpleasant.
Click to expand...
I wore out the pegs on my beloved RD400…
 
levimax said:
I agree FR variations due to higher output impedance has the biggest potential for audibility. When I did a level matched blind test between an original ST-70 and a Neurochrome Mod 86 I could tell no difference but while I had everything set up I also measured the FR of the 2 amps and then added 0.9 Ohm resistance to the Neurochrome at which point the FR matched almost perfectly. See measurements below. For a push pull Hi-Fi tube amp like the original ST-70 the internal resistance is about 0.7 Ohms and even though it measurably changed the FR it was not audible to me (but may be to someone). A SET tube amp on the other hand can have ~5 ohms of internal resistance which rather than causing a fraction of a dB FR difference could cause 1 or 2 dB of FR difference which can be clearly audible in some cases depending of course on the speaker's impedance curve. Tube amps are not practical or cost effective (especially for higher power) but a Hi-Fi tube amp sounds fine. Many tube amps today are not Hi-Fi by today's standards or even by 1950's standards (They are effects boxes) which I think causes a lot of confusion. Rather than mess around with expensive tube amps or DSP tube emulators if you want to find out what your system would sound like with a "Hi-Fi" tube amp put a 1 Ohm resistor in series with the speakers to see what a SET would sound like use a 5 ohm resistor.

View attachment 380511
Click to expand...
Well I was using electrostats. Impedances of more than 32 ohms down low and barely an ohm at the other end.
 
Blumlein 88 said:
Same here only mine was an RD 350.
Click to expand...
My bud had a 74 rd350 at the same time I had the earlier r5 model. He had 3 hp more and 6 speeds so he'd get me on the straightaways. I had the lower center of gravity so I'd catch him in the corners. Expansion chambers with a rejet and a blueprinted motor with planed heads gave me the straightaway advantage later on. With the expansion chambers I was able to use a closer mounting system for the foot pegs which meant no more scraping in the corners no matter how I tried.
 
not too shabby ...if you are an old guy and still want to show off. putting this in a family room, etc... where it will be seen as a work of Art History, all the while its putting out acceptable sound for gatherings and parties would not hurt anyone.
 
Doodski said:
Dirt rides being 2 stroke is the best!
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After riding lawnmowers and other lawn equipment in the 60's (1967, I started my lawncare business & mechanicing at 10 years of age). In 1971 I was working at a shop and a mechanic for many local dirt bike machines that raced at a place called Chisolm Trails.
|Husqvarna, Bultaco & such were my trade before the Japanese motorcycles arrived. Then it was the Kawasaki hand grenades (so finely honed that if you went much further than the finish line, they'd likely blow up. They won a lot of races but Suzuki, Yamaha & Honda had a much better reliability record.
& then I would go home & get in my 80 HP V4 two stroke Johnson Outboard 15 ft boat.
Or the Go-Kart in the garage that had twin
McCulloch MAC-101's (each modified to be 15 HP at 13,500 RPM in 1971 [we managed to get ourselves in a bit of a pickle with the POLICE due to this creation of ours] {it seems that they did not like 13/14 year old teens running around in a Go-Kart that they said one of us was clocked by them on a public road at 133 MPH})
Naturally it could not be proven as to which one of us pre Hoonigan renegades was driving it at the time, which resulted in our parents making us disassemble the thing & sell the engines. I sold one to my older cousin & still have it.

Applications[edit]​

Aircraft

Specifications (MC-101B)[edit]​

Data from McCulloch Kart Engines, Bore and Stroke, MC101B Kart Engine Illustrated Parts List and Cliche[2][3][4]

General characteristics​

Components​

  • Fuel system: carburetor
  • Oil system: pre-mixed
  • Cooling system: air-cooled

Performance​

  • Power output: 12.5 hp (9 kW) at 9000 rpm

    TOO MUCH FUN WITH 2 STROKES, I guess.
 
EJ3 said:
After riding lawnmowers and other lawn equipment in the 60's (1967, I started my lawncare business & mechanicing at 10 years of age). In 1971 I was working at a shop and a mechanic for many local dirt bike machines that raced at a place called Chisolm Trails.
|Husqvarna, Bultaco & such were my trade before the Japanese motorcycles arrived. Then it was the Kawasaki hand grenades (so finely honed that if you went much further than the finish line, they'd likely blow up. They won a lot of races but Suzuki, Yamaha & Honda had a much better reliability record.
& then I would go home & get in my 80 HP V4 two stroke Johnson Outboard 15 ft boat.
Or the Go-Kart in the garage that had twin
McCulloch MAC-101's (each modified to be 15 HP at 13,500 RPM in 1971 [we managed to get ourselves in a bit of a pickle with the POLICE due to this creation of ours] {it seems that they did not like 13/14 year old teens running around in a Go-Kart that they said one of us was clocked by them on a public road at 133 MPH})
Naturally it could not be proven as to which one of us pre Hoonigan renegades was driving it at the time, which resulted in our parents making us disassemble the thing & sell the engines. I sold one to my older cousin & still have it.

Applications[edit]​

Aircraft

Specifications (MC-101B)[edit]​

Data from McCulloch Kart Engines, Bore and Stroke, MC101B Kart Engine Illustrated Parts List and Cliche[2][3][4]

General characteristics​

Components​

  • Fuel system: carburetor
  • Oil system: pre-mixed
  • Cooling system: air-cooled

Performance​

  • Power output: 12.5 hp (9 kW) at 9000 rpm

    TOO MUCH FUN WITH 2 STROKES, I guess.
Click to expand...
You obviously had a similar teen session as I... LoL.
 
Doodski said:
You obviously had a similar teen session as I... LoL.
Click to expand...
It was while writing an apology letter to the police officers involved that we realized that we had taken them away from possibly catching REAL criminals and endangered their lives in their efforts to corral us.
So while we still were renegade Hoonigans, we did not do it on public roads anymore. (At least not until we got our drivers licenses at 15 and were using street legal equipment).
But then we decided to things that were not legal like driving on the beach in a 1974 Oldsmobile station wagon with one of us standing on the roof as both lookout for drunk, late night people on the beach & also so that person could act like he was surfing the car. This was after mid-night at speeds of perhaps 20 MPH. (not really endangering anyone but ourselves).
So yeah, we didn't stop it completely but we toned it down substantially.
I still think that there is something about 2 strokes in my blood:
At 32.03 you will see (for about 7 seconds) a McC 101 mounted on a chainsaw & the speed it can make through wood!!
(the rest of the video is cool too).
 
Oh about when I was old enough for a driver's license a local airport closed and moved. For a few years every weekend people would show up with go carts to race down that long runway. I took my cousins who were younger by there pretty often. Someone had a dual McCullough with one chainsaw motor on each rear wheel. It pretty much smoked all the other karts and some motorcycles that showed up. If people showed up with many motorcycles and cars the cops ran everyone away. Go carts they didn't care. That went on for several years. One fellow had a prop driven kart he had built. Don't remember the engine. It didn't accelerate that well, but it was different and would go something like 50 mph. Probably dangerous potentially, but no one ever was hurt by it.
 
SIY said:
That's because it doesn't exist. People who insist it does, upon whom burden of proof rests, have failed utterly. I was one of them, couldn't tell the difference once levels were matched and I couldn't peek. I am also unable to find rigorous demonstrations of the existence of elves.
Click to expand...

How do you account for something like my 300B SET, where it has the inverted loudness effect? That is ALL distortion, so it does fall into the category of amplifiers sound the same until you reach the limits of in the category of “that is a broken design”.

But to a lesser degree, now think about level matching a speaker that has a highly variable frequency response due to damping factor on a tube versus one that is linear. If you match to a 1 kHz test tone, it may not be accurate level matching at other frequencies.

So instead of tube vs solid state, it is one amp going into clipping versus not…
 
Blumlein 88 said:
Oh about when I was old enough for a driver's license a local airport closed and moved. For a few years every weekend people would show up with go carts to race down that long runway. I took my cousins who were younger by there pretty often. Someone had a dual McCullough with one chainsaw motor on each rear wheel. It pretty much smoked all the other karts and some motorcycles that showed up. If people showed up with many motorcycles and cars the cops ran everyone away. Go carts they didn't care. That went on for several years. One fellow had a prop driven kart he had built. Don't remember the engine. It didn't accelerate that well, but it was different and would go something like 50 mph. Probably dangerous potentially, but no one ever was hurt by it.
Click to expand...
The initial proof of concept test of our twin McCulloch 101 Go-Kart was against my new 1971 Honda CL 175 which topped out at an optimistic speedometer 88 MPH.
So we blocked the throttles on the Go-Kart so that they would only open to half throttle & the Go-Kart promptly passed me when I was at top speed on the Honda.
We were elated, of course!
 
That sounds like a great use for those early Mccullochs and Homelites as they weren't very good at cutting wood. If it wasn't for the pioneering efforts of the Swedes and Germans in the 80's their chainsaws would still be stuck in the 50's and 60's style. Heavy, loud, slow chain speed with soft bars and no roller nose or automatic oiler and normally broken down by noontime or before.
 
GXAlan said:
So instead of tube vs solid state, it is one amp going into clipping versus not…
Click to expand...
And source impedance. The single most important variable here. A speaker-dependent tone control which can't be switched off. The overload, source impedance, and rising distortion are all easier and cheaper to do using a single ended topology with transistors, they are not peculiar to the active device.

BTW, just for fun, I hooked up my main speakers (Quad 988 ESLs) to a 300B SET amp just to hear the effect. 1 out of 10: would not recommend.
 
motorstereo said:
That sounds like a great use for those early Mccullochs and Homelites as they weren't very good at cutting wood. If it wasn't for the pioneering efforts of the Swedes and Germans in the 80's their chainsaws would still be stuck in the 50's and 60's style. Heavy, loud, slow chain speed with soft bars and no roller nose or automatic oiler and normally broken down by noontime or before.
Click to expand...
This engine was never meant for a chainsaw, it was designed to be a racing Go-Kart engine (Sort of).
It was designed to be used in Ultra Light Aircraft (but to bring costs down, it needed to be sold as a Racing Go-Kart engine for volume production purposes):
Aircraft:
In order for it to be a chainsaw engine, one had to buy the largest McCulloch chainsaw available, remove the much lesser engine & install the 101.
Robert Paxton McCulloch was a bit of an interesting character (the following was mostly taken from Wikipedia):
Two years after he graduated from Stanford University, he married Barbra Ann Briggs, whose father was Stephen Foster Briggs of Briggs and Stratton. His first manufacturing endeavor was McCulloch Engineering Company, located in Milwaukee, Wisconsin. There he built racing engines and superchargers. In his early 30s, he sold the company to Borg-Warner Corporation for US$1 million.
McCulloch then started McCulloch Aviation; and, in 1946, he changed his company's name to McCulloch Motors Corporation.
In 1948 McCulloch's model 3-25 revolutionized the chainsaw market with the one-man light weight chainsaw.
McCulloch also developed a centrifugal supercharger for automotive use. At first, these were produced and sold under the McCulloch name. In 1956, the supercharger division was renamed Paxton Superchargers. Notable cars such as the 1954–1955 Kaiser Manhattan and the 1957 Studebaker Golden Hawk and Ford Thunderbird F-Type had a McCulloch/Paxton Supercharger. The supercharger was also used in CO2 scrubbers on Navy submarines. The division was sold in 1958, becoming Paxton Automotive, which remains in business.
In 1963, on the courthouse steps of Kingman, McCulloch purchased a 26-square-mile (67 km2) parcel of barren desert that would become the site for Lake Havasu City. At the time it was the largest single tract of state land ever sold in Arizona,[3] and the cost per acre was under US$75.
He purchased John Rennie's 1831"New" London Bridge (built in 1831)was gradually sinking into the River Thames in 1968 and moved it to Lake Havasu to promote the city.
The attraction was opened on October 10, 1971, with elaborate fanfare: Fireworks, a parade, entertainment, and celebrities, such as Bonanza's Lorne Greene and dignitaries such as the Lord Mayor of London.[3]
With the purchase of the bridge, McCulloch accelerated his development campaign, increasing the number of flights into the city. At the time, the airport was located on the island. The free flights to Lake Havasu lasted until 1978 and reportedly they totaled 2,702 flights, bringing in 37,000 prospective buyers.
He had set a couple of World Records:
McCulloch died February 25, 1977, in Los Angeles
 
Last edited:
I agree; Mcculloch motors had no business being on a saw. In my case I bought a brand new (3.7 ci) Mcculloch saw in 1989. One woodcutting bud had a Husky 266 and the other had a Stihl 056. Both their saws would throw rooster tails of sawdust while my Mcculloch would barely keep the sawdust out of the cut. After 40 hours of use the chain groove on the bar of my saw was so worn it would barely cut and would not cut straight. To the junkpile went the Mcculloch to be replaced with a Jonsered 625II which I still use to this day.
 
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