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Post by ehmokey on Feb 4, 2019 19:59:38 GMT -5
Looking for advice. My tube preamp and subwoofer aren't getting along.
At low volumes there is very little bass from my PSA S1500. The sub's plate amp 27K kohms input impedance is too low and too hard to drive for the pre (ARC LS28). The sub only has line level inputs, it does not have High Level inputs.
As a test, I connected my cheap sub (MTX SW10) to my XPA 1-Ls via it's high level inputs and voila! huge bass output.
Short of replacing the PSA S1500, what options do I have? Are there home audio High Low converters (like the ones used un car audio)? Or perhaps an input impedance buffer to go between the preamp and the sub?
Many thanks for your input.
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Post by adaboy on Feb 4, 2019 21:40:30 GMT -5
 You need something like this. Line level amplifier. |
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Post by garbulky on Feb 4, 2019 22:57:51 GMT -5
^^^ Pretty much this. novisnick should be able to tell you more as he uses PSA and uses something similar |
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Post by novisnick on Feb 4, 2019 23:04:51 GMT -5
You need something like this. Line level amplifier. adaboy is correct! I use one of these on each of my subs. Works great, just be careful not to turn it up and the plate amp up too much. |
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Post by musicfan on Feb 5, 2019 6:55:33 GMT -5
Why not use and rca splitter and input to both left and right inputs on the plate amp. This doubles the signal the inputs receive
Much cheaper and should work
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DYohn
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Post by DYohn on Feb 5, 2019 9:08:55 GMT -5
That preamp has standard voltage line outs. How are you connecting the subwoofer?
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KeithL
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Post by KeithL on Feb 5, 2019 9:49:34 GMT -5
A buffer would seem to be the obvious answer.
However, the LS28 seems to be rated to be able to drive loads well below 28k, and has a rated 600 Ohm output impedance, so it doesn't seem like it should have trouble driving your subs. Looking for advice. My tube preamp and subwoofer aren't getting along. At low volumes there is very little bass from my PSA S1500. The sub's plate amp 27K kohms input impedance is too low and too hard to drive for the pre (ARC LS28). The sub only has line level inputs, it does not have High Level inputs. As a test, I connected my cheap sub (MTX SW10) to my XPA 1-Ls via it's high level inputs and voila! huge bass output. Short of replacing the PSA S1500, what options do I have? Are there home audio High Low converters (like the ones used un car audio)? Or perhaps an input impedance buffer to go between the preamp and the sub? Many thanks for your input. |
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Post by ehmokey on Feb 5, 2019 20:17:47 GMT -5
DYohn . My connections are as follows: Pre to monoblocks via XLR Pre to Sub via RCA to Sub - both Right and Left to each input of the sub. When I spoke to Tom Vodhanel from PSA, his thought was that at 27 kohms input impedance, the ARC would have no problem driving the subwoofer. But after much research I found the following document The Thorny Math of Impedance.pdf (http://www.audioresearch.com/ContentsFiles/The%20Thorny%20Math%20of%20Impedance(0).pdf) The LS28 has the same output impedance specs as the Ref5 SE mentioned in the document. I am not an electrical engineer by any sorts; however when I connected a different subwoofer via High Level inputs, thus removing the preamp from the equation, the output of the sub was leagues above that of the PSA. The MTX has a plate amp of 150 watts vs the PSA's 725 watts RMS. However, I do not want to give up the quality of the PSA. @ novisnick do you use the identical line level amp that Adaboy mentions? @keythl - Are there any impedance buffers that you recommend? (or is the line amplifier the same thing as an impedance buffer?) And to garbulky, adaboy and musicfan...thank you for your comments, recommendations and ideas. Percy.
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Post by novisnick on Feb 5, 2019 21:25:26 GMT -5
ehmokey , yes sir, works great for over a year now! Not one problem. Enjoy the music! 🎶🎶🎶🎶🎶
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KeithL
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Post by KeithL on Feb 6, 2019 9:59:42 GMT -5
From the numbers I really wouldn't expect the A.R.C. to be having trouble. However, to be honest, since most solid state preamps have no trouble driving much lower loads, a lot of solid state equipment has an input impedance in the 10k range..... Therefore, especially in combination, this can sometimes be a drive problem for certain tube gear.
An impedance buffer is simply a line amplifier that has one input, one output, and a fixed gain of 1 . (A "buffer" is just simpler because it omits the controls.)
Unfortunately I haven't kept up on who is making them lately - so I can't personally recommend any of them. (I have heard that the little one made by Schiit Audio is decent... but I haven't personally tried one.)
DYohn . My connections are as follows: Pre to monoblocks via XLR Pre to Sub via RCA to Sub - both Right and Left to each input of the sub. When I spoke to Tom Vodhanel from PSA, his thought was that at 27 kohms input impedance, the ARC would have no problem driving the subwoofer. But after much research I found the following document The Thorny Math of Impedance.pdf (http://www.audioresearch.com/ContentsFiles/The%20Thorny%20Math%20of%20Impedance(0).pdf) The LS28 has the same output impedance specs as the Ref5 SE mentioned in the document. I am not an electrical engineer by any sorts; however when I connected a different subwoofer via High Level inputs, thus removing the preamp from the equation, the output of the sub was leagues above that of the PSA. The MTX has a plate amp of 150 watts vs the PSA's 725 watts RMS. However, I do not want to give up the quality of the PSA. @ novisnick do you use the identical line level amp that Adaboy mentions? @keythl - Are there any impedance buffers that you recommend? (or is the line amplifier the same thing as an impedance buffer?) And to garbulky , adaboy and musicfan ...thank you for your comments, recommendations and ideas. Percy. |
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Post by donh50 on Feb 6, 2019 10:00:04 GMT -5
The large difference in volume is more likely due to differences in subwoofer gain and frequency response than the output loading on the preamp. You may like a lot of bass boost; impossible to really tell without some sort of SPL measurements. You cannot turn up the level on the PSA? It's also possible the line out of the ARC or amp in the PSA is defective...
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DYohn
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Post by DYohn on Feb 6, 2019 10:18:02 GMT -5
My guess is the level on the sub amp is not set correctly. The preamp should have no trouble whatever driving the amp properly. Since it has no bass control make sure it is connected to the second set of line outs.
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Post by ehmokey on Feb 6, 2019 18:43:00 GMT -5
The PSA Sub level is set to max. Interesting to note that for the current connection to the MTX sub, the volume pot is at less than half and it produces way more output than the PSA.
I will test the SPL levels by reconnecting the Sub to the pre amp and measuring the output level at a specific volume setting on the preamp. then I will connect the MTX to the amps via high level input at the same volume level and note the two measurements.
Additionally, I will bring out my Yamaha AVR and perform the same test and perform the identical test.
thank you.
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DYohn
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Post by DYohn on Feb 6, 2019 18:52:02 GMT -5
The PSA Sub level is set to max. Interesting to note that for the current connection to the MTX sub, the volume pot is at less than half and it produces way more output than the PSA. I will test the SPL levels by reconnecting the Sub to the pre amp and measuring the output level at a specific volume setting on the preamp. then I will connect the MTX to the amps via high level input at the same volume level and note the two measurements. Additionally, I will bring out my Yamaha AVR and perform the same test and perform the identical test. thank you. Smells like a defective subwoofer amp... |
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Post by ehmokey on Feb 6, 2019 23:57:20 GMT -5
I performed several tests and tried as best I can to keep everything else constant including interconnects, source, measurement distance at the woofer, and measuring device. The Yamaha AVR was reset to factory levels and the PEQ equalizer was turned off. I used the same subwoofer cable for the line level connection between the pre and the subwoofer. the only notable difference is that I can connect two cables (left and right) from the ARC to both subs, but only one cable from the Yamaha. To keep most things equal I only connected one RCA cable to the LFE Line Level RCA Jack of each sub. I made sure the monitors measured 79 db/spl without the sub for each Preamp (ARC volume =10 ; Yamaha volume = -33) I looped the first 30 seconds of Lorde's Buzzcut Season, which is a bass heavy song from the get go. Test begins MTX Sub / ARC LS28 High Level Connection from XPA1L amps to sub first I measured the MTX sub using the ARC pre and connecting via High Level input in the sub from the XPA-1L. The MTX plate amp was set to 1/3 volume and provided a read out at the woofer of 80 db/spl. this was an almost perfect match. MTX Sub / ARC LS28 Pre Line level Then, using the ARC pre and connecting the sub via Line Level at 1/3 volume on the MTX Sub plate amp the output was 66 db/spl. A 14 db drop. Using the same connection but turning the plate amp volume pot to full provided 75 db/spl. not quite a level match to the satellite speakers. PSA S1500 / ARC LS28 Line level connection and 1/3 volume at plate amp provided 65 db/spl. Virtually the same as the MTX sub Same connection at full volume on the plate amp provided 75 db/spl. MTX Sub / Yamaha Pre Line Level connection at 1/3 volume provided 65 db/spl. At full volume the same connection provided 75 db/spl PSA Sub / Yamaha Pre Line Level connection at 1/3 volume on the plate amp provided 68 db/spl at the woofer. At full volume on the plate amp pot provided 72 db/spl. from the above I surmise the plate amps of both subs are working as intended and there are no issues with either input Jack's since the line level measurements were very close. Same can be said for the both preamps and their output jacks. However, I was able to prove that with my equipment I can only match the volume of the satellite speakers by using high level inputs. If I want to match the satellite speakers I have to either use a subwoofer that has High Level inputs or, a subwoofer with higher input impedance of at least 45 k ohms, or purchase a line level amplification device as adaboy, garbulky and novisnick have suggested. I look forward to your comments P. |
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Post by novisnick on Feb 7, 2019 0:52:37 GMT -5
Purchase the line level amp and be done with it. I too was running a Yamaha, the 3020. Once installed and dialed in I had great JOY!
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Post by garbulky on Feb 7, 2019 0:59:21 GMT -5
Purchased the line level amp and be done with it. I too was running a Yamaha, the 3020. Once installed and dialed in I had great JOY! Yeah I'm not mistaken B'zilla had the same issue with PSA subs and the fix was your method |
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Post by ehmokey on Feb 11, 2019 11:28:35 GMT -5
Gents. I purchased the line amplifier as suggested. All is copacetic now and I am very satisfied.
Thank you all.
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Post by krauley on Mar 17, 2019 20:21:39 GMT -5
I have the 1801v myself and i know about the situation that you PSA users are talking about. What i did was turn up the output of my prepro to get a higher (?) signal so that the sub wouldnt time out at lower volumes but i still get the click on and off at very low volumes. I connected a rca splitter so that i have both the lfe/left and a right rca input is connected so i will get a signal to keep the timeout but i still get them like i said.
All that typing to ask how you are hooking up the line level amp and how do you adjust it while running your room correction software?
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