This is my first post other than my intro post and I’m unsure if this is the right forum for it, so please correct me if it should be elsewhere.
I recently acquired a very nice Dynaco ST-150 which I’m going to refurb, but which works well at present. I wanted to try it with a Topping D50s dac. The chain looks like qobuz->roon->topping d50s(usb)->dynaco st-150->elac dbr speakers.
This is in a small den. The dac ouput is 2v at 0db and the st-150 is rated 75w rms into 8 ohms at 1v in.
To achieve 75db at my listening position, With roon dsp volume at 0db, I have to lower the output on the dac to -10 to -15db depending on source material.
So my question. Setting the dac at -6db, I should be getting about 1v out with roon at 0db.
Is it best to vary the rest of the volume with roon’s 64 bit dsp volume control or is it better to leave roon at 0db and vary all volume with the topping d50s volume control?
My apologies in advance if this is a stupid question.
I recently acquired a very nice Dynaco ST-150 which I’m going to refurb, but which works well at present. I wanted to try it with a Topping D50s dac. The chain looks like qobuz->roon->topping d50s(usb)->dynaco st-150->elac dbr speakers.
This is in a small den. The dac ouput is 2v at 0db and the st-150 is rated 75w rms into 8 ohms at 1v in.
To achieve 75db at my listening position, With roon dsp volume at 0db, I have to lower the output on the dac to -10 to -15db depending on source material.
So my question. Setting the dac at -6db, I should be getting about 1v out with roon at 0db.
Is it best to vary the rest of the volume with roon’s 64 bit dsp volume control or is it better to leave roon at 0db and vary all volume with the topping d50s volume control?
My apologies in advance if this is a stupid question.
Stereo 150
Consider DC protection for your speakers.
At the Dinaco input, you can put a 2: 1 voltage divider from resistors.
Decide where to adjust the volume for convenience and a good signal-to-noise ratio.
Please note that ELAC Debut Reference DBR62 120W\6 Om and Dinaco 150W\8 Om
Consider DC protection for your speakers.
At the Dinaco input, you can put a 2: 1 voltage divider from resistors.
Decide where to adjust the volume for convenience and a good signal-to-noise ratio.
Please note that ELAC Debut Reference DBR62 120W\6 Om and Dinaco 150W\8 Om
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Definitely try various volume control settings on both boxes to minimize hum and hiss. With digital source, might also be some high frequency howl.
What kind of music do you listen to? Crest values very from 3 db on electro-house music, to ~60 db on classical music.
I set my system to run at 1.0 vpp on 8 ohm 101 db 1w1m speakers on very soft passages. Then when they set the cannon off in 1812 overture, my 72 watt amp can put out 72 watts, to really thrill me.
Your speakers probably are not as sensitive, and other sorts of music or program sources are somewhere in the middle on crest factor. But I doubt if you will enjoy the performance with the wattage set to maximum value all the time. Having some experience with a predecessor dynaco ST120, I would expect your unit to melt the output transistors if it runs near 75 w/ch very often, unless heat loss system is re-engineered. I put 2 PCAT fans blowing on the heat sinks of my ST120, running continuously.
Note direct connected shorted transistors can burn your speaker driver coils or rip the surround. Why the OLDdiy comment previous about adding some sort of speaker protection board is important, if your speakers cost more than $3 from the charity resale shop. Lots of speaker protection threads on this forum. Many boards for sale on e-bay have too small relay contacts to provide much protection. Welded contacts are a serious risk with DC currents caused by shorted output transistors.
What kind of music do you listen to? Crest values very from 3 db on electro-house music, to ~60 db on classical music.
I set my system to run at 1.0 vpp on 8 ohm 101 db 1w1m speakers on very soft passages. Then when they set the cannon off in 1812 overture, my 72 watt amp can put out 72 watts, to really thrill me.
Your speakers probably are not as sensitive, and other sorts of music or program sources are somewhere in the middle on crest factor. But I doubt if you will enjoy the performance with the wattage set to maximum value all the time. Having some experience with a predecessor dynaco ST120, I would expect your unit to melt the output transistors if it runs near 75 w/ch very often, unless heat loss system is re-engineered. I put 2 PCAT fans blowing on the heat sinks of my ST120, running continuously.
Note direct connected shorted transistors can burn your speaker driver coils or rip the surround. Why the OLDdiy comment previous about adding some sort of speaker protection board is important, if your speakers cost more than $3 from the charity resale shop. Lots of speaker protection threads on this forum. Many boards for sale on e-bay have too small relay contacts to provide much protection. Welded contacts are a serious risk with DC currents caused by shorted output transistors.
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Indianjo, I listen to mostly jazz, some classical and some rock. Funny you mention 1812 as I was listening to it yesterday specifically for the canons. Not great on the elacs. Much better on Naim S-400’s in my living room.
I have been listening at 75db at my listening position which is 7 feet from the speakers. Peaks according to a calibrated mic on REW thrn run up to 90db on some material. This listening level requires closer to -15db but the amp is not even remotely warm. Almost oddly cool. I even lowered the speaker fuses from the original 3A to 1A quick blo.
I have been listening at 75db at my listening position which is 7 feet from the speakers. Peaks according to a calibrated mic on REW thrn run up to 90db on some material. This listening level requires closer to -15db but the amp is not even remotely warm. Almost oddly cool. I even lowered the speaker fuses from the original 3A to 1A quick blo.
99.999% of modern consumer audio amps have direct connected output transistors, that can burn a speaker if they short. This is a stupid design IMHO, but 1000000s of units that way have been sold. Many got great reviews in magazines. Predecessor dynaco ST120 had a short proof speaker cap, but magazine reviewers hated that feature. You have to get up to $999 PA amps to have serious relay output protection, like my CS800s. There are lower priced amps that have a speaker relay, but most have problem with sound dropout at 20-30 years of age due to dirty contacts. More short risk on a stage, that the players or roadies will pull out a 1/4" phone plug part way and short the amp output blowing it up. But I've tripped over my speaker cables at home yanking them loose. Fortunately on a vacuum tube amp that was not sensitive to speaker disconnect.
The ST120 had serious sound deficiencies, but it wasn't the speaker cap. It was inadequate output transistor idle bias current. With a djoffe bias control circuit, my caps in & out ST120 sounds just like (@ 1w) the cs800s which can be direct connected in & out.
The ST150 was a much more modern design - that can burn out speakers like all the competitors.
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Ok so I have the following to do’s
1. Voltage divider at input to deal with the 2v output of the dac and the 1v sensitivity of the ST-150
2. Relay speaker protection
In the short term should I try replacing the 1A quick blo with .5A on the output?
Also re s/n is the best situation to have the dac at 0db essestially bypassing the preamp in it thus outputting 2v, then reduced to 1v with the voltage divider I will add to the ST-150
Or simply set the dac at -6db outputting 1v and controlling the volume with roon’s 64 bit dsp volume control? This still leaves the dac preamp in the circuit.
If the dac is at 0db and I set the roon dsp volume at -6db does that really reduce the dac output to 1v?
1. Voltage divider at input to deal with the 2v output of the dac and the 1v sensitivity of the ST-150
2. Relay speaker protection
In the short term should I try replacing the 1A quick blo with .5A on the output?
Also re s/n is the best situation to have the dac at 0db essestially bypassing the preamp in it thus outputting 2v, then reduced to 1v with the voltage divider I will add to the ST-150
Or simply set the dac at -6db outputting 1v and controlling the volume with roon’s 64 bit dsp volume control? This still leaves the dac preamp in the circuit.
If the dac is at 0db and I set the roon dsp volume at -6db does that really reduce the dac output to 1v?
If you have a scope or analog VOM you can measure the output of your DAC. I use a simpson 266-XLPM VOM that has no e-caps in it to die of old age. I use alligator clip leads on the RCA plug of the cable.
Instead of putting resistors exterior to the ST-150 you could change the ratio of R301 & R2 inside the chassis to reduce sensitivity. Also, if you get digital whine, you can increase the value of C2. My 1986 Ensoniq EPS keyboard had digital whine, about 50 db down without measuring it. I had to increase the input bypass cap of my ST120 with 3 m RCA cables: it was picking up AM radio.
Reference your listening habits, you are likely not putting out more than 1 or 2 v pp (multiply by .7 to get average) from the amp at 75 db in your room. Ie not stressing the amp. Measure it with the clip leads & meter again.
Instead of putting resistors exterior to the ST-150 you could change the ratio of R301 & R2 inside the chassis to reduce sensitivity. Also, if you get digital whine, you can increase the value of C2. My 1986 Ensoniq EPS keyboard had digital whine, about 50 db down without measuring it. I had to increase the input bypass cap of my ST120 with 3 m RCA cables: it was picking up AM radio.
Reference your listening habits, you are likely not putting out more than 1 or 2 v pp (multiply by .7 to get average) from the amp at 75 db in your room. Ie not stressing the amp. Measure it with the clip leads & meter again.
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My speakers are worth $500 each, $600 new + freight. None available all month ebay closer than 3000 miles (LA), since my SP2-XT were stolen in September. My CS800s amp cost $251 with freight & tax. My ST120 amp cost $50 blown, $80 parts & 500 hours to repair/upgrade it. Enzo said the CS800s relay system reliably protects the speaker. The $600 SP2g speaker has HD 20 db down 54-15000 hz @ 1W1m, and it sounds like a real piano. Anybody else specifying HD? Klipsch LaScala are running $10500 ea plus freight, the alleged competition.
6 db down is allegedly half the voltage, but I may remember wrong. I'd really suggest measuring it if you have a scope. Relative measurements you can use the peak to peak value for both, but if you convert to average voltage (sort of RMS but not as scientific) the Vav value is .7 Vpp.
You acoustic db meter measures power, not voltage. I think db voltage squared is db power, but all my college texts were stirred around or stolen, so I can't look it up now.
Anyway there is no substitute for trying several things and seeing which sounds better.
I don't own any unprotected amps so no knowledge if the fuses are fast enough to protect the speaker or not. Crowbar DC protection just burned the triac lands off the PCB in my PV-1.3k, big design failure. Supposed to blow the main breaker, not burn the PCB.
After the burglar cleaned me out of electronics & musical instruments, I bought a couple of $5 speakers at Salvation army, Marked down to $2.50. 3 ways with 6" woofers. Those I wouldn't mind connecting to an unprotected amp. Sound like ****.
You acoustic db meter measures power, not voltage. I think db voltage squared is db power, but all my college texts were stirred around or stolen, so I can't look it up now.
Anyway there is no substitute for trying several things and seeing which sounds better.
I don't own any unprotected amps so no knowledge if the fuses are fast enough to protect the speaker or not. Crowbar DC protection just burned the triac lands off the PCB in my PV-1.3k, big design failure. Supposed to blow the main breaker, not burn the PCB.
After the burglar cleaned me out of electronics & musical instruments, I bought a couple of $5 speakers at Salvation army, Marked down to $2.50. 3 ways with 6" woofers. Those I wouldn't mind connecting to an unprotected amp. Sound like ****.
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