Bottlehead Forum
Bottlehead Kits => Stereomour II => Topic started by: abaloghtesla on August 01, 2020, 09:07:14 AM
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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?
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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.
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.
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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.
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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?????
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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?
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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
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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.
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"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.
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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
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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.
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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
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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
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Thanks alot---I will try the other option--Thanks so much!!
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Hey Paul----I'm back!!!! While I was gone, I purchased a pair of Marlins from Blumenstein Audio. There was a little increase in output but none that I would write home to mom about. I did take your advise earlier, and ran output of Pat-4 into the input of Stereomore, and WOW!!!I had no idea that those little speakers could put out such music. It appears that the reduction amp is not driving the stereomore enough, so I bought the upgrade kit and I wonder if its worthwhile in stalling it , since it does not give you the gain I'm looking for. Am I right or wrong---or do I need another amp between the phono and stereomore
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The upgrade will increase the gain in the phono preamp, which will make the output of the Stereomour louder.
An Eros would give you even more output.
A Moreplay between the Reduction and Stereomour would also provide more gain.
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Let me try to get this through my thick scull. Even though I do the upgrade ,the gain will still be less than what the Moreplay would give you.
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whats the best route? Do an upgrade with my kit on the way or look for a moreply??
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Start with the Integration upgrade. It will give you more gain and improve the dynamics and bass a bit.
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Paul---Thank you again. Will do the upgrade
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Also, you can modify the Stereomour balance control to increase the gain. I'll do the calculation, but you should get around 3dB from this and 4dB from the Reduction C4S. I'll do some calculations ...
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Paul-this is in reply to the upgrade, I finished the shunt regulator. here are my voltage measurements. On metal tab assoc with 1A I get 109.5 v.(110 to 120v) . the second metal tab assoc with 1B, I get 109.0 v(110v to 120v) and with terminal56 I get 128.5 v(130v). With these voltages should I proceed with the rest of the up-grade? Art
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Paul--was not sure if you got my last post---if so, then dis-regard.
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Those seem OK.
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Thanks--Will proceed forward!
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Upgrade finished but there was a slight gain in volume but not what I'm looking for.I need some kind of amp that can drive that stereomore to full potential( like PAT 4 driving it). Maybe I'm reaching too far this pre-amp. I'm lost.
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You could put a Moreplay between the Stereomour and the Reduction.
If you had a Stereomour II, there would be another mod or two to increase gain a bit, but gain is pretty high on the Stereomour I already.
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Not to be disrespectful of any who works for Bottlehead, for all you people have given your best, but if I had to build one more kit at this time, I would burst
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I went through the whole thread (again), and I downloaded the PAT-4 manual as well - and I am still not 100% confident that we are working the right problem. We have been working a 5-10dB problem but your descriptions seem to indicate a 15-20dB problem. Language is not precise enough to be sure what the real problem is. Here are some questions I still have:
* Is this a Stereomour I or a Stereomour II? Both have appeared in the posts, at different times. (S.II has a balance control; S.I does not.) As PB noted, that makes a difference in what adjustments might be made.
* When you took output from the Reduction to Stereomour to speakers, where did you set the PAT-4 volume control to get an acceptable loudness? Did you use
--1-- turntable to Pat4 phono input, PAT-4 output to Stereomour input, Stereomour output to speakers, or
--2-- turntable to Reduction input, Reduction output to PAT-4 high-level input, PAT-4 output to Stereomour, input, Stereomour output to speakers?
This will help us guess the magnitude of the problem, but if it doesn't help enough there is more that can be done. I am aware that this is getting to be a long slog, but don't lose faith yet!
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I am confused by this persistent problem. It shouldn't really exist in the first place. Please correct my calculations, if I'm getting this wrong.
OP has a cartridge that is listed as 5.5mV - 5cm/sec. Reduction gain is 36dB @ 1kHz. Stereomour needs 0.4V at the input for full power.
5.5mV * 63V/V = 346.5mV. The Stereomour is just about 1.25dB below full output with that ... and 5.5mV is by no means the maximum voltage that's ever going to come out of the cartridge. The PAT-4 can't possibly be playing much louder than that through the Stereomour.
Puzzled
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Later on today I will hook up my PAT4 to see what my settings are. But I did have it set up to #1---I do have a stereomore 11 Current set up is Fluance turntable with blue cartridge into the reduc tion pre-amp, into the stereomore11 into blumenstein marlin speakers. I have volume control all the way up on stereomore11 and I can sit 3 feet from the speakers and listen to them comfortably. When i use the output of turntable, into PAT4, into stereomore11---yes, Ican pump so music out, that I have to turn down the volume of stereomore11. Right now I just need to hook up everything eliminating the reduction amp and replacing it with the PAT4, and seeing where my controls are placed on both units.
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Great! Now, when you find where the controls are set, leave them there and swap in the Reduction - turntable to reduction input, reduction output to PAT-4 high level input (Radio for instance) and see if it is louder or not.
If I read the PAT-4 specs correctly, it should be louder with Reduction. (PAT-4 phono stage is 34dB gain, Reduction with upgrade is 40dB.) If it is louder as expected, then we'll know the Reduction is working correctly and we can interpret the control settings to determine how much more gain you need.
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to Paul Joppa: Finally got to look at my set up. All control knobs are centered. With the reduction in is is a little louder but not that much. I can turn volume control all way max and I still can listen to this record. I can increase volume on PAT4 and I cannot max it, cause its so loud.
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Forget the last sentence or so--it sounded jibber-ish When the reduction amp is in the ckt with PAT4 , it was louder but not by very much. Not enough to right home about.
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Its late now in pittsburgh--I'm signing off.
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That's great - I know it's slow but we've made a lot of progress and we're nearly there.
* We knew going in that you need more loudness capability
* We've determined that the Stereomour is able to drive your speakers to adequate loudness, provided it gets enough input signal - so it's worth the effort to look for more gain
* With this last experiment, we've determined that the Reduction is working correctly.
* We know from the specs that the PAT-4 line section gain is 20dB, and you have reported that it is more than enough - so you need more than zero extra gain, and less than 20dB.
Now we just need to determine how much more gain you need:
With the Reduction in the system with the PAT-4, turn the PAT-4 volume control all the way up. Adjust the volume with the Stereomour control until it's "loud enough", and post back where that volume control is set. It will be more than 12 o'clock (straight up) and less than 5:00 (the maximum). Be as exact as you can - the control is most sensitive between about 12:00 and 2:00 and I expect that's where you will end up.
[Note that I have assumed you have attached the volume knob so that its range is from 5:00 to 11:00, so that 12:00 straight up is exactly the midpoint of the rotation.]
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Ok The phono is hooked up to input of reduction and its output is hooked up to Tuner input of PAT4. Volume control of PAT4 is turned fully clockwise. Volume control of stereomore rotates from approx. 7:00 to 5:00 and 12:00 approx. center. As I move volume from 7:00 to 9:00 there is as significant increase in volume(very loud) At this point, if I turned the volume contol to midpoint, I would not have any windows in this house.
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Well THAT was unexpected!
I must have made an assumption that was not true. I am now wondering whether there might be an issue with the Stereomour volume controls. Let's try repeating the same test, but with Stereomour volume all the way up, and use the PAT-4 volume control to find the "adequately loud" point. If that falls in the 12:00 to 2:00 range, then there is an issue with the Stereomour after all. If it turns out to be 9:00 then I am perplexed and we'll need to get more methodical, which I have been trying to avoid.
While you're at it, check whether both channels are equally loud with the Stereomour balance control centered, or if you need to set it a little off center.
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Also triple check that you have 12AT7s in the Stereomour and not something else.
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Back again: yes I have 12 AT7 in there. I had a little tbl with the left chan tube on the reduction and after playing with it, I got it to stay on. I re-ckt position of all knobs to see if they were all equi-distant of my marks.Yes, the right chan seems alittle stronger that the left, but by not much ------The second test has same results as first. You start getting comfortable"Tea" music at 0900 and it gets gradually "loud" at 1200 and beyond that, I can audition for Woodstock. Now, I tried it backand forth for at least 5 times and both ways have approx. the same results.
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Thanks, that's a help.
You got loud with the Stereomour control at 9:00 and with the PAT-4 at 12:00. Everything I know says they should have been the same, so I suspect you may have switched the tone and balance potentiometers - that would explain the difference. We can check that further by just measuring the input resistance of the Stereomour with the tone control centered and at each extreme. I think this is worth pursuing, just to be sure the amp is working correctly.
But that will have only a small effect on loudness. Everything I know says that the gain of the PAT-4 with the volume set to the midpoint is 1.0, or 0dB. Which says you don't need more gain. But you do! We can pursue that issue by making real gain measurements on both Reduction and Stereomour. Usually PB recommends using your cellphone as a signal generator, and making voltage measurements at various places including some internal to the amps.
However, it will take a while to get through this exercise. And I completely understand if you need to take a break from this and just get some tunes playing - in which case, you still need some gain, unless you keep the PAT-4 in the circuit. So I'll suggest that you could purchase an inexpensive preamp to get things going - for example, the Schiit Modi [edit - Magni is what I meant] is a $99 headphone amp that works as a preamp as well, and provides 15dB of gain. I have no direct experience with it, but they are well regarded.
We'll keep working on either or both issues as long as you are wish. We're not going anywhere, so if you want to take a break and pick it up again in a couple months, that's fine too.
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I may have said this wrong but this is what I meant: both test that you suggested me to do were almost identical in outcome. I'll check the amp out. Goodnight
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Sorry to bother you again. Looking into schitts products and already I am confused. They have two products for 99$. The modi 1 is actually modi 3 DACS. The headphone amp is either the magni3+ or the magni heresy headphone amp? Need help again
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He probably meant the Magni. The Modi is a DAC and not an amp. I think the Magni and the Magni Heresy both have 15 dB of gain, so you should look at both and see which you might prefer. Schiit has specs for both on the same page.
You could also just buy both and return the one you don’t like within the return window. They charge a 15% restocking fee, I think.
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I wouldn't be adding a preamp quite yet. I would go through the tests to be sure the S2 is working. After that we have two modifications to suggest that will raise the gain more.
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Yes, Magni was what I meant - i apologize for my confusion. I have edited my post.
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Thanks OQUIN for the input, its well appreciated.
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Ok, I'mback again---I installed the Magi by SCHITT and it works great! It's leave it as it is, or search for that elusive gain tbl.????? what do you say?
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i haven't heard anything back from Paul joppa or Paul Birkeland. I hope they are ok.
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What’s the question? If you should keep trying new things? If you like what you’re hearing keep what you have. Or tinker around. It’s personal preference.
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We're OK, PB has just been a little pre-occupied with getting the revised B-Pre out, and I've been puzzling over what you mean by "tbl.?????". I'm old, and often don't get the abbreviations used these days. :^)
Nothing wrong with leaving it as is, other than having an extra box in the system. I'm very glad to hear it is working for you now! If there's any possibility of squeezing out enough gain without the Magni, we'll need to know what gain settings you are using with it.
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I"m glad I got every one's input. I just need to know one thing: Could I have possibly wired something wrong in the reduction 11 or st2 to give the low volume output, or there was no problem at all and it was my old ears failing at an exponential rate. Anyway, I'm content with the MAGI, and until I can come up with something new, I leave it as such. Thanks to everyone for all their help
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I think the only remaining question is the last one I posted:
"... I suspect you may have switched the tone and balance potentiometers - that would explain the difference. We can check that further by just measuring the input resistance of the Stereomour with the tone control centered and at each extreme. I think this is worth pursuing, just to be sure the amp is working correctly. "
You can access the inputs most easily from the cable connecting the Magni to the Stereomour. Just pull the RCA hacks from the Magni, leaving them connected to the Stereomour. With the balance control centered, measure the resistance between the center pin and the outer shield of the jack, on both channels. Repeat for the balance control all the way clockwise, and again with it all the way counter-clockwise.
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This is what I have, to the nearest whole number: center position of pot( left chan 51 k ohms), (right chan,50 k ohms)------------Pot turned all the way counterclockwise:( left chan 24.5 k ohms), (right chan 45.5 k ohms----------------pot turned all the clockwise:(left chan 45.5 k ohms:(right chan 24.5 k ohms
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Excellent! Your controls are correctly wired and your Stereomour is functioning normally. Thanks for bearing with us through the complicated analysis; we'll do our best to learn from this exercise to prevent future issues.