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Thread: Why does my SS amp need to warm up?

  1. #1
    Suspended topspeed's Avatar
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    Why does my SS amp need to warm up?

    I recently replaced my PS Audio HCA2 (switching amp) with a Pass X150.5 and was hoping someone can explain to me why the sound of this solid state amp changes so much as it warms up? Tubes need to warm up, I get that...but solid state? When I first plugged it in, I was concerned I'd made a mistake, but helpful advice from Mr. P and others assured me that 24 hrs of feeding it juice would make all the difference, and it did. Now I leave it in stand-by, but even then I've got to give it a good half hour or so before she brings her big guns out to play. I've never encountered this before in a ss amp. The nerd in me wants to know why this happens

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    Shostakovich fan Feanor's Avatar
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    I'd like to know too. I also have a Pass X150.5 and agree that it takes a good 30-40 minutes to warm up close to potential from Stand-by. Maybe it's the transistors coming up to the temperature they need for stable operation, but that's only a guess. According to Pass, the X150.5 draws about 30 watts on Stand-by but 200 watts powered On but idle.

    But I note the may Class D Audio SDS-258 required a warm-up time to sound best; in its case it was only 10-15 minutes but even so.

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    Quote Originally Posted by Feanor View Post
    I'd like to know too. I also have a Pass X150.5 and agree that it takes a good 30-40 minutes to warm up close to potential from Stand-by. Maybe it's the transistors coming up to the temperature they need for stable operation, but that's only a guess. According to Pass, the X150.5 draws about 30 watts on Stand-by but 200 watts powered On but idle.

    But I note the may Class D Audio SDS-258 required a warm-up time to sound best; in its case it was only 10-15 minutes but even so.
    The PS Audio consumed so little power while idling, I simply never turned it off. Warm up? What warm up? Gotta love that Class D efficiency!

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    My X250 also sounded better after 30+ minutes of play time. I can't explain it but I believe it has to do with the Class A type topology Pass uses. Coincidentally, my 532h sounds better after some play time. Now I wonder if it's a solid state thing where you need high resolution system to hear it or if it's just the character of certain amps. The 532h is quite a bit different topology. The Pass warm up time was more apparent to me, just like when I had my CJ tube amps.

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    Don't big Caps need to be charged all the way before optimum performance?

    My Stratos amp as well as a Rotel Receiver both get louder and start sounding better after about 30 minutes.

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    Forum Regular blackraven's Avatar
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    Quote Originally Posted by Hyfi View Post
    Don't big Caps need to be charged all the way before optimum performance?

    My Stratos amp as well as a Rotel Receiver both get louder and start sounding better after about 30 minutes.
    Yes, caps need to charge up but that takes a second to do so. It probably has something to do with the temperature as well as polarization.

    TS, welcome to the Pass club. How do you like the amp? What are you using for a preamp?
    Pass Labs X250 amp, BAT Vk-51se Preamp,
    Thorens TD-145 TT, Bellari phono preamp, Nagaoka MP-200 Cartridge
    Magnepan QR1.6 speakers
    Luxman DA-06 DAC
    Van Alstine Ultra Plus Hybrid Tube DAC
    Dual Martin Logan Original Dynamo Subs
    Parasound A21 amp
    Vintage Luxman T-110 tuner
    Magnepan MMG's, Grant Fidelity DAC-11, Class D CDA254 amp
    Monitor Audio S1 speakers, PSB B6 speakers
    Vintage Technic's Integrated amp
    Music Hall 25.2 CDP
    Adcom GFR 700 AVR
    Cables- Cardas, Silnote, BJC
    Velodyne CHT 8 sub

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    Suspended topspeed's Avatar
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    Quote Originally Posted by blackraven View Post
    Yes, caps need to charge up but that takes a second to do so. It probably has something to do with the temperature as well as polarization.

    TS, welcome to the Pass club. How do you like the amp? What are you using for a preamp?
    Hi BR,

    I like the Pass quite a bit. I had never purchased an amp before without auditioning it, but knew Nelson Pass has the same JBL's for his own system, so it was safe to assume they would be a synergistic match, which they are. Once warmed up (which is key), the X150.5 has terrific grip and extension on the bottom end while the mid band and treble are both very smooth without the slightest hint of grain or glare. It isn't as fast in transient response as the HCA2 and the edges are softened in comparison, but its not a matter of better or worse, just different. While both are rated at 150wpc, the Pass seems to pull harder (car-guy parlance). The greatest attribute is the complete lack of fatigue. It just makes you want to turn it up, which the JBL's love! Once she's really cooking, the sound has meat on the bones and the dynamics simply bloom. I'll spin tunes for hour after hour. I went from Porcupine Tree to Stan Getz to The Eagles and relished every second of it.

    My pre-amp for now is a Marantz SR5010 used in Pure Direct with all room correction and audio/video processing shut down. Sometime down the road, I think I'll add a pre-amp/dac w/ theater bypass. Before I purchased the Pass, I was negotiating on a CODA CSX integrated that Mr. P spoke highly of, which would have saved me the trouble of finding a good line stage, but I've always wanted a Pass so that's what ended up in my room.

  8. #8
    Forum Regular blackraven's Avatar
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    Congrats on the Pass. You described the sound perfectly. My X250 has a soft top end but tremendous grip and bass extension. I find transients are very fast but I am using a BAT VK-51se preamp which is just an explosively dynamic preamp.
    topspeed likes this.
    Pass Labs X250 amp, BAT Vk-51se Preamp,
    Thorens TD-145 TT, Bellari phono preamp, Nagaoka MP-200 Cartridge
    Magnepan QR1.6 speakers
    Luxman DA-06 DAC
    Van Alstine Ultra Plus Hybrid Tube DAC
    Dual Martin Logan Original Dynamo Subs
    Parasound A21 amp
    Vintage Luxman T-110 tuner
    Magnepan MMG's, Grant Fidelity DAC-11, Class D CDA254 amp
    Monitor Audio S1 speakers, PSB B6 speakers
    Vintage Technic's Integrated amp
    Music Hall 25.2 CDP
    Adcom GFR 700 AVR
    Cables- Cardas, Silnote, BJC
    Velodyne CHT 8 sub

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    What I notice after some play time the sound seems to have less of a glare and opens up more, warmer sound. The Pass just gets into a more relaxed character and more open.

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    Suspended topspeed's Avatar
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    Quote Originally Posted by Mr Peabody View Post
    What I notice after some play time the sound seems to have less of a glare and opens up more, warmer sound. The Pass just gets into a more relaxed character and more open.
    The only time I've experienced anything resembling glare on the JBL's was when I had the Rotel inserted, which was a horrible match in my rig. With the Pass, after 30-45 minutes, the bass is a lot fuller while the mids come forward and, like you said, open up more. The difference, especially in the bass, is not subtle.

    We need more nerds on this site! There has to be a technical explanation for why this solid state amp does this.

  11. #11
    Forum Regular blackraven's Avatar
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    Quote Originally Posted by topspeed View Post
    The only time I've experienced anything resembling glare on the JBL's was when I had the Rotel inserted, which was a horrible match in my rig. With the Pass, after 30-45 minutes, the bass is a lot fuller while the mids come forward and, like you said, open up more. The difference, especially in the bass, is not subtle.

    We need more nerds on this site! There has to be a technical explanation for why this solid state amp does this.
    Send an Email to Pass Labs and ask them.
    Pass Labs X250 amp, BAT Vk-51se Preamp,
    Thorens TD-145 TT, Bellari phono preamp, Nagaoka MP-200 Cartridge
    Magnepan QR1.6 speakers
    Luxman DA-06 DAC
    Van Alstine Ultra Plus Hybrid Tube DAC
    Dual Martin Logan Original Dynamo Subs
    Parasound A21 amp
    Vintage Luxman T-110 tuner
    Magnepan MMG's, Grant Fidelity DAC-11, Class D CDA254 amp
    Monitor Audio S1 speakers, PSB B6 speakers
    Vintage Technic's Integrated amp
    Music Hall 25.2 CDP
    Adcom GFR 700 AVR
    Cables- Cardas, Silnote, BJC
    Velodyne CHT 8 sub

  12. #12
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    Maybe glare wasn't the right word, when first turned on the sound has just a coolness more so than compared to the sound after warming up. I say glare because after warm up it's more inviting to the ears, not that at first it isn't good, it just gets better.

  13. #13
    Suspended topspeed's Avatar
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    So I just talked to Pass Labs and he said the reason the amp sounds better is simple: Heat. The caps reach full capacitance quickly but the mylar needs heat to sound best. As the current and bias come up, the radiant heat affects everything in the amp... obviously in a good way. He mentioned that they can actually put a dead cold amp on the 'scope and watch the distortion curve deepen and then decrease as the amp warms up, which is why final tuning isn't done until the amps are at full boil. We both found it ironic that 30 years ago, you could fry a semiconductor if you got too close with a soldering iron, yet some of the chips today don't reach full potential until they've got 400 degrees of heat in them.

    So there you go boys, the answer is heat.
    blackraven, Feanor and Mr Peabody like this.

  14. #14
    Forum Regular blackraven's Avatar
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    It is what I suspected.
    Pass Labs X250 amp, BAT Vk-51se Preamp,
    Thorens TD-145 TT, Bellari phono preamp, Nagaoka MP-200 Cartridge
    Magnepan QR1.6 speakers
    Luxman DA-06 DAC
    Van Alstine Ultra Plus Hybrid Tube DAC
    Dual Martin Logan Original Dynamo Subs
    Parasound A21 amp
    Vintage Luxman T-110 tuner
    Magnepan MMG's, Grant Fidelity DAC-11, Class D CDA254 amp
    Monitor Audio S1 speakers, PSB B6 speakers
    Vintage Technic's Integrated amp
    Music Hall 25.2 CDP
    Adcom GFR 700 AVR
    Cables- Cardas, Silnote, BJC
    Velodyne CHT 8 sub

  15. #15
    Forum Regular harley .guy07's Avatar
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    Well I jokingly tell people when they come over that I have a very good $6,000 space heater that doubles as a unit that makes my speakers sound good. I really love my Pass and have always wanted one even back in the Aleph days when they were a weird square. I have always loved Nelsons work even the Adcom designs in the 90's that were very affordable and good even though not a shade of good compared to Pass Labs. I know that the newer class D stuff is getting better especially designs based on the Pascal architecture that has been the newest thing which I heard is really good but I just can't get past the Pass sound.

    Marantz SR5008(HT)
    Nu Force P8 Preamp (2 channel)
    Pass Labs X150.5(2 channel)
    Adcom 545 mk2 power amp(rear channel amp)
    Spatial Audio M3 Turbo S Mains Speakers
    Dayton 8" HO custom sealed subwoofer(2 channel)
    Yamaha NS-c444 center channel
    Emotiva ERD-1 surround speakers
    JBL e250p subwoofer highly modified
    Samsung 46" LED TV
    OPPO BDP-83 blue ray/multi format player
    ps-audio NuWave dac (2 channel)
    Dell I660 music server running fidelizer windows 8 audio optimizer
    PS Audio Quintet power center



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