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August 10, 2020, 01:54:45 AM

Author Topic: help  (Read 163 times)

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Offline abaloghtesla

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help
« on: August 01, 2020, 09:07:14 AM »
I have a fluance turntable with a 5.5 mv cartridge in it, a reduction 11 pre amp and a stereomore 1 poweramp-----I throw a record on and all appears ok except for the fact that i have the volume set all the way up and it sounds as lound as two people talking in the room. I have two A25Dynaco speakers . I think this power amp has enough ooph to drive them. what am i doing wrong?

Offline Natural Sound

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Re: help
« Reply #1 on: August 01, 2020, 09:19:26 AM »
Those speakers need more power than the Stereomour can produce. The spec says they need 15 watts minimum. It could work in a near field application but not for filling a large room with music.

Quote
Dynaco A-25 loudspeaker Specifications
Description: Two-way, dynamic bookshelf loudspeaker with aperiodic woofer loading. Impedance: 8 ohms. Power ratings: minimum amplifier 15Wpc continuous sinewave watts; maximum 70W program.

Offline bernieclub

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Re: help
« Reply #2 on: August 01, 2020, 09:32:24 AM »
If the sound is not distorted, it sounds like the Reduction may not be driving the Stereomore to full output.  You may need an active preamp.   Or you have a large, damped room and need more power.
Bernie Zitomer

Offline abaloghtesla

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Re: help
« Reply #3 on: August 01, 2020, 10:22:55 AM »
I wish I would have known this before I bought this equip. I think I'll just run output of the stereo 11 power
  amp into the input to my dynaco 80 power amp---I know that has more than enough power for those speakers----or maybe this?--What kind of speakers are compatible with this amp?????

Offline Paul Joppa

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Re: help
« Reply #4 on: August 01, 2020, 12:23:28 PM »
The Reduction with a 5mV cartridge should be able to drive the Stereomour beyond full power on loud passages with most recordings. Some recordings may have been made at a lower level, though - so try a few different recordings if you haven't, just to be sure.

This will still be only moderately loud. The A25 is 92dB/watt, so with Stereomour's max output of 3.5 watts per channel you will get peaks of 97dB - about 5dB less than the THX standard minimum loudness for movies. Normal conversation is about 60dB, shouting is about 80dB. It should be adequate unless you need rock-concert levels.

We can walk you through testing the gain. The first step would be to check the voltages of both amps as described in the manuals, to be sure the tubes are operating correctly. Is the Stereomour wired for 8-ohm loads? Does the Reduction have the C4S plate loads?

Paul Joppa

Offline abaloghtesla

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Re: help
« Reply #5 on: August 01, 2020, 01:52:15 PM »
i was trying to listen to Donna Summers Disco music and it seemed like it did not have get up and go. Yes all my voltage on both my kits were very close to what was published.I just need a speaker system that is compatible with this power amp to play Disco and then some long haired stuff. I like all kinds of music

Offline abaloghtesla

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Re: help
« Reply #6 on: August 01, 2020, 03:14:28 PM »
Yes, the stereomore11 was set up for 8 ohm output but I do not know what c4s plate load is for the reduction amp is.

Offline Paul Joppa

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Re: help
« Reply #7 on: August 01, 2020, 07:36:32 PM »
"Integration" is the upgrade kit for Reduction:

https://bottlehead.com/product/integration-upgrade-for-reduction-phono-preamp/

I asked because it increases the gain of the Reduction (among other things). It's not a big increase - just from 36dB to 40dB, about the same as going from 4 ohm to 8 ohm output. I just wanted to understand what your gain structure was.

My recollection of disco is that it makes pretty heavy demands on bass power, so that may be part of the problem. If you have some string quartets, or cool jazz (not big band!) you might give that a listen.  If small acoustic group music sounds "right," then it might be that disco is too demanding for a 2A3 amp with those speakers. But if even that sort of music is weak, then it's always possible something else is going on - that's why I mentioned the voltage checks.

It's a slim chance, but double-check the output transformer impedance wiring (p.21 of the manual) to be sure it's actually set for 8 ohms.

One other thing - SET tube amps tend to sound a bit tinny at first; it usually takes 50-100 hours of break-in for them to open up.
Paul Joppa

Offline abaloghtesla

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Re: help
« Reply #8 on: August 08, 2020, 11:06:57 AM »
Paul, you do an excellent job in what you do! I am just a sinking raft in a sea of audiophile lingo. Let me tell you what I did  do. I hooked the output  from the stereomore to the input of my  Dynaco Pat4 and except for a little hum , it played grate!. I probably was awaiting for everything to blow up, but everything worked for a couple of hours before I turned it off. What I need to know is what kind of speaker do you use with an amp for only 3.5 watt output or do I need some kind of amp after the stereomore and before the speakers or better yet, a speaker with its own power amp
 

Offline Paul Joppa

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Re: help
« Reply #9 on: August 08, 2020, 01:11:29 PM »
When SETs first began to be known in the USA, there was widespread awareness the you needed very efficient speakers. As it became more popular, this point has been less emphasized, but it's still true.

A couple decades ago I compiled some statistics from my back issues of Stereophile magazine, and concluded that they consistently recommended a certain loudness level capability when they reviewed a speaker. For a 3.5 watt amplifier, that corresponds to a speaker sensitivity of 97dB. I usually say that means it will satisfy "most audiophiles, most of the time." However, there is a wide variation, depending on the room, the music, and the listener, so this estimate is not always an accurate guide.

Most modern speakers run 85-90dB sensitivity, and would want 50-15 watts per channel respectively. Your A-25s are 90dB, and would want 16 watts by this calculation. Speakers from the golden age of tube audio - say, 1950-1970 - however often were 95-100dB, which is ten times as sensitive. These tend to be quite large, and often use horn tweeters. Classic examples are Altec A-7s and Klipsch Cornwalls, both of which have long been associated with SET amplifiers. The other fairly widely popular approach is the fullrange single driver crowd, with Lowther and Fostex being iconic examples. These days there is more variety available, but speakers for use with SETs are still a very small minority.

So, that's the story (or at least, my version of it) on speakers.

If you were to keep your A-25s, it's possible that a bit more gain would make it loud enough, but it is equally possible that it would overload the amp, creating too much distortion. For that reason I can't recommend spending a lot on that possibility until you test it. The easy test would be to connect the PAT-4 outputs to the Stereomour inputs. You can use either the PAT-4 phono stage or the Reduction as input to the PAT-4. This should give you enough gain to drive the Stereomour to and beyond its linear range, so you can see the effect of greater drive.
Paul Joppa

Offline abaloghtesla

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Re: help
« Reply #10 on: August 08, 2020, 02:49:14 PM »
Like always---I like your inputs. But, i must admit that I was in error in my last reply. It should have read that I used the output of the stereomore and connected it the input of the dynaco 80 power amp(40watss per chan). It played with alot of power to spare ,but like I said, I wasn't sure if I was hurting anything? What I understood ( I may be wrong), that I should try using the output to the pat 4 into the input of the stereomore. if all fails I guess to try the upgrade kit to the reduction and try out a new set of speakers. but, I wanted to know what brand of speakers are very compatible with this amp. If you cannot promote a brand that ok--I understand

Offline Paul Joppa

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Re: help
« Reply #11 on: August 08, 2020, 04:19:04 PM »
You won't hurt anything with the setup you described.

With that setup, you have established that 40 watts is more than enough, so the question is whether 3.5 watts is enough. Your understanding is correct - connect the PAT-4 output to the Stereomour input (and turn the Stereomour volume control all the way up), connecting the speakers to the Stereomour. Then listen to some music, using the PAT-4 to control the volume and see if it will get loud enough without sounding distorted. If it does not get loud enough, then you need more efficient speakers. If it can get loud enough, then we can discuss ways to increase the gain.

There is another Bottlehead sub-forum discussing speakers, and I see there are two threads on the first page of that forum specific to the Stereomour. That's probably the best way to get some ideas on speakers. Here's a link:

https://forum.bottlehead.com/index.php?board=12.0
Paul Joppa

Offline abaloghtesla

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Re: help
« Reply #12 on: August 08, 2020, 04:57:34 PM »
Thanks alot---I will try the other option--Thanks so much!!