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 Post subject: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Mon 26, 2018 11:00 pm 
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Location: Hamilton, Ontario, Canada. L8R 3H4
Stromberg Carlson AU-36 Mono Amplifier
9 tubes
50W (max @ less than 5% harmonic distortion?)
Weight: 35 lbs
Frequency response: 50 Hz to 12kHz (0 to -3 db) Is this the usual response for an antique amp of this age?

Stats courtesy of:
https://www.radiomuseum.org/r/stromberg_amplifier_au_36.html

Video (not from this seller; it's just the same model):
https://www.youtube.com/watch?v=XssRfGSvyjo

Looks quite nice, and the top cage can come off for an exposed view. Sadly, it's not stereo. The seller wants $200 for it. A big issue for me is the distance. It would take a 3 hr bus ride to pick it up. And, another 3 hrs to go back. Good thing I like to read... :?

Is it worth it?


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Last edited by bedtime on Nov Mon 26, 2018 11:06 pm, edited 1 time in total.
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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Mon 26, 2018 11:06 pm 
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Location: Sunnyvale CA
bedtime wrote:
9 tubes
50W (max @ less than 5% harmonic distortion?)
Weight: 35 lbs
Frequency response: 50 Hz to 12kHz (0 to -3 db) Is this the usual response for an antique amp of this age?
Looks quite nice, and the top cage can come off for an exposed view. Sadly, it's not stereo. The seller wants $200 for it. A big issue for me is the distance. It would take a 3 hr bus ride to pick it up. And, another 3 hrs to go back. Good thing I like to read... :?

Is it worth it?


That is pretty typical for a PA amplifier. I probably wouldn't pay $200 for it unless I collected such things. The output transformer is probably not up to using it for a hi-fi conversion. But, to each his own, I know there are people who are interested in that sort of thing.


Brett


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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Mon 26, 2018 11:17 pm 
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Brett_Buck wrote:
...

That is pretty typical for a PA amplifier. I probably wouldn't pay $200 for it unless I collected such things. The output transformer is probably not up to using it for a hi-fi conversion. But, to each his own, I know there are people who are interested in that sort of thing.


Brett

If it's a PA amp, then I'm not interested. I would want to use this for my living room on a 12"-15" speaker and some tweeters. If all this is amp is good for is amplifying 1kHz...

In any event, I'm just 'browsing' and seeing what's out there. I couldn't afford the $200 until at least the new year, and I'm not sure I'd be comfortable paying more than $150 at that time, anyways.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Mon 26, 2018 11:36 pm 
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It's been hacked with added inputs. The fact it has a microphone pot implies PA, not hi fi. A hi fi amp of the 50s or 60s would have something like several selectable inputs for stuff like, phono, tuner, and Aux. That has phono but obviously for an old fashioned crystal or ceramic pickup. The value is in the transformers and the tubes. Any hacking otherwise could be reversed electrically if not cosmetically. But that should keep the price down. If you were gonna use a big vintage speaker and play 78s it would be fine for that. Might not sound too terrible despite the high freq rolloff. Depends on program material.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 12:36 am 
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wazz wrote:
It's been hacked with added inputs.

Yes, noticed that. Though they might come in handy, so I don't mind.

Quote:
The value is in the transformers and the tubes. Any hacking otherwise could be reversed electrically if not cosmetically. But that should keep the price down. If you were gonna use a big vintage speaker and play 78s it would be fine for that. Might not sound too terrible despite the high freq rolloff. Depends on program material.

I'm not sure how to tell if the transformer is capable of amplifying the highs and lows. The transformer looked quite big, so I assumed it was capable of delivering...

This is not sounding too attractive anymore.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 1:34 am 
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Frequency response, 50 CPS to 12,000 CPS is not really HiFi. 20-20 is more like it. And as mentioned above, the output transformer is probably not up to HiFI standards...

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 6:25 am 
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There is more to an output transformer than the size. For high quality performance the way it is wound matters. You can't tell that without taking it apart, which of course, leaves you without the transformer.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 10:54 am 
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Jim Mueller wrote:
There is more to an output transformer than the size. For high quality performance the way it is wound matters. You can't tell that without taking it apart, which of course, leaves you without the transformer.

Exactly, Jim. But a small output transformer is sure to be a "choke" point. (no pun intended)

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 2:02 pm 
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Don Cavey wrote:
Frequency response, 50 CPS to 12,000 CPS is not really HiFi. 20-20 is more like it. And as mentioned above, the output transformer is probably not up to HiFI standards...

Quote:
There is more to an output transformer than the size. For high quality performance the way it is wound matters. You can't tell that without taking it apart, which of course, leaves you without the transformer.

Okay, so basically, it's the transformer that is bottleneck here. Were most audio amps of the 50's like this? Are there any amps that do the 20Hz - 20kHz from this time? I plan to run a 15" speaker and a 3" tweeter on it.

Quote:
Exactly, Jim. But a small output transformer is sure to be a "choke" point. (no pun intended)

The smaller transformers act as chokes sometimes? That would make sense why the lower end would be weak.

Could another transformer of equal impedance but better quality be substituted in that amp?

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 2:56 pm 
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Tubes are some value, but the rest pass on. No shortage of amplifiers in the world and priced right, take your time.


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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 5:22 pm 
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hoffies2 wrote:
Tubes are some value, but the rest pass on. No shortage of amplifiers in the world and priced right, take your time.

Thank you. Sometimes I just need to hear it. I get caught up in it.

Gonna pass on it. If I had not asked you guys, I would likely have wanted to buy it.

Thank goodness for ARF! :)

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 5:52 pm 
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What you want is a unit that was designed and sold as a high fidelity amplifier. You don't want a PA amp like the one being discussed. While there are some similarities between the two, it takes more work than it's worth to make a high fidelity amplifier out of a PA amplifier.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 8:42 pm 
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The price is way too high for a PA amp. These were built mainly for amplifying microphones and possibly record players at the local high school/ sock hop. I've restored a few PA amps and some actually sound rather nice. This one probably sounds decent. Just not $200 decent. $50 max is all I would spend on something like this.


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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 10:16 pm 
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Mr. Detrola wrote:
What you want is a unit that was designed and sold as a high fidelity amplifier. You don't want a PA amp like the one being discussed. While there are some similarities between the two, it takes more work than it's worth to make a high fidelity amplifier out of a PA amplifier.

This amp is no longer under consideration. Seems like it just won't do what I need it to.

Quote:
The price is way too high for a PA amp. These were built mainly for amplifying microphones and possibly record players at the local high school/ sock hop. I've restored a few PA amps and some actually sound rather nice. This one probably sounds decent. Just not $200 decent. $50 max is all I would spend on something like this.

Perhaps, but I've yet to see them much lower in Canada.

...

How about an amp like this:

https://www.ebay.ca/itm/DIY-kit-6n9p-EL34-B-class-A-vacuum-tube-amplifier-tube-AMP-13W-13W/122543185964?hash=item1c8824a02c:g:cEQAAOSw-89ZPQBQ:rk:13:pf:0

The big thing about it that bothers me is that it is made in Asia; the English is horrible: "Note: this kit default is not include the input AC cable." And it seems to be this way on just about every Asian amp on Ebay—I've even seen selling mistakes on the amp itself (e.g., 'In put' for input)! :shock: You'd think they'd take the time to get someone who is native born English to correct it. It's shortcuts like this that really concern me; where else did they take shortcuts? This is very obvious and they missed it...

What does the manual look like? I don't even wanna know. :roll:

Another thing that is on my mind is if the amp was well designed. Some of these amps don't even have model numbers on them; yet they claim to have 20Hz - 20kHz response and such and such distortion. I highly doubt they actually tested it.

*Sigh* So much crap to dig through. My budget is about $225 USD if anyone has any ideas for a stereo amp.

Would be great if I could find a Dynaco st-70, but they seem way beyond my budget.
Thoughts?

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Tue 27, 2018 10:31 pm 
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If mono reproduction is all that you want, how about the Eico HF-20? It's a great little amp, with a mag phono preamp and a huge ultra-linear output transformer.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Wed 28, 2018 1:38 am 
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Tim Tress wrote:
If mono reproduction is all that you want, how about the Eico HF-20? It's a great little amp, with a mag phono preamp and a huge ultra-linear output transformer.

This looks to be right up my alley! Great specs and a decent price too!

Here are the specs: https://www.manualslib.com/manual/13082 ... e=2#manual

Power Response (20W):
+0, -1 db 20Hz to 20kHz
+0, -3 db 10Hz to 40kHz

Distortion 60 & 6000 Hz @ 20W: 1.3%

Very good boost:
15 dB bass (50Hz) control (nice and low bass)
15 dB treble (10Hz) control

Has a very bizarre bass and treble wiring in schematics: https://www.manualslib.com/manual/1308294/Eico-Hf-20.html?page=24#manual. A little bit confusing to me.

Looks like they might go for around $200 USD. :)

Might put up a WTB in the forum when I get a chance and see what comes up.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Wed 28, 2018 2:50 am 
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bedtime wrote:
...Has a very bizarre bass and treble wiring in schematics: https://www.manualslib.com/manual/1308294/Eico-Hf-20.html?page=24#manual. A little bit confusing to me.....
That's a standard Baxandall tone stack.


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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Wed 28, 2018 4:41 am 
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Location: Sunnyvale CA
bedtime wrote:
Brett_Buck wrote:
...

That is pretty typical for a PA amplifier. I probably wouldn't pay $200 for it unless I collected such things. The output transformer is probably not up to using it for a hi-fi conversion. But, to each his own, I know there are people who are interested in that sort of thing.


Brett

If it's a PA amp, then I'm not interested. I would want to use this for my living room on a 12"-15" speaker and some tweeters. If all this is amp is good for is amplifying 1kHz...

In any event, I'm just 'browsing' and seeing what's out there. I couldn't afford the $200 until at least the new year, and I'm not sure I'd be comfortable paying more than $150 at that time, anyways.


If you really want a hi-fi amplifier from that era, you can certainly do better than this one. There are a lot of pretty good mono amps from the mid-late 50's like the Dynaco Mk III or MK IV, and decent performers from Heathkit, Eico, Scott. The less-good versions might fall into your price range as long as you are willing to work on refurbishing them. A quick survey of that auction site indicates several pretty good Heathkits that would serve your purposes and are under $200.

I would however note that there are many much better stereo amplifiers routinely available for about the same price or less. The Dynaco ST-120 can usually be found for under $100 and reworking it to be reliable is quite inexpensive, and the performance is far better than any 50's mono tube amp. I saw a couple of ST-150s, supposedly working, for under $200, and that is likely to be better than almost all tube amps of any age or cost.

Brett


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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Wed 28, 2018 8:06 am 
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Quote:
Okay, so basically, it's the transformer that is bottleneck here. Were most audio amps of the 50's like this? Are there any amps that do the 20Hz - 20kHz from this time?

There are amplifiers for many purposes, each tweaked for that particular use. There are PA amps, guitar amps, servo amps, juke box amps, amplifiers for console and smaller mass market record players, high fidelity amplifiers, transmitter modulators, and probably others. Many of them look more or less similar. They also come in varying performance quality levels. You have to get one that suits your purpose. The best bet is to look it up on the Internet and ask here about the particular model; but, then again, you already know that.

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 Post subject: Re: 50W Stromberg Carlson Amp. Is it worth it?
PostPosted: Nov Wed 28, 2018 9:11 pm 
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Flipperhome wrote:
bedtime wrote:
...Has a very bizarre bass and treble wiring in schematics: https://www.manualslib.com/manual/1308294/Eico-Hf-20.html?page=24#manual. A little bit confusing to me.....
That's a standard Baxandall tone stack.

Thanks. I know now. :)

Quote:
If you really want a hi-fi amplifier from that era, you can certainly do better than this one. There are a lot of pretty good mono amps from the mid-late 50's like the Dynaco Mk III or MK IV, and decent performers from Heathkit, Eico, Scott. The less-good versions might fall into your price range as long as you are willing to work on refurbishing them. A quick survey of that auction site indicates several pretty good Heathkits that would serve your purposes and are under $200.

I would however note that there are many much better stereo amplifiers routinely available for about the same price or less. The Dynaco ST-120 can usually be found for under $100 and reworking it to be reliable is quite inexpensive, and the performance is far better than any 50's mono tube amp. I saw a couple of ST-150s, supposedly working, for under $200, and that is likely to be better than almost all tube amps of any age or cost.

Brett

I took at look at the specs of the Dynaco ST-120 (Freq. Resp. 5Hz to 100,000Hz, SNR 95dB, THD .5), and they are amazing. Though, I was really hoping to get a tube amp. I do like the Dynaco ST-70, but only if it is within my price range, and I've yet to see that.

A big buying factor for me is the look of the amp, as it will be going in my living room Yes, it's superficial, but this is something I want to have for the rest of my life, so I'll have to look at it for a long time. Might as well be something that I find attractive. So far, I really like the look of all the Dynacos, and I like the look of some of the Eico amps, especially the ones with the brass faceplates.

I'm not thinking of purchasing any time before the new year. I'm just gathering information so I can keep an eye out daily if anything comes up for a really good price. After talking to you guys, I have a much better idea of what I want.

Quote:
There are amplifiers for many purposes, each tweaked for that particular use. There are PA amps, guitar amps, servo amps, juke box amps, amplifiers for console and smaller mass market record players, high fidelity amplifiers, transmitter modulators, and probably others.

You forgot organ amps... :P

Quote:
They also come in varying performance quality levels. You have to get one that suits your purpose. The best bet is to look it up on the Internet and ask here about the particular model; but, then again, you already know that.

Yes, I look up each model and find the specs for it. If I'm still interested, I look up reviews online and on YouTube. If still interested, I post here.

Is it me or are the sellers on Ebay selling at inflated prices? Seems that they think they're sitting on goldmines.

*** EDIT ***

Found another potential:

Bogen MX60A Tube Amplifier:

https://www.ebay.ca/itm/Vintage-Bogen-MX60A-Tube-Amplifier/153278981251?hash=item23b023a483:g:vYEAAOSwUWtb~GrG

https://www.manualslib.com/manual/1000182/Bogen-Mx60a.html?page=2#manual

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57' Heathkit EA-2 Amplifier
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