HornsRus Posted June 17, 2001 Share Posted June 17, 2001 Well i finally received my amp that i won off of Ebay and have a question.The amp gets warm if left on without any kind of signal.This perplexes me for it does'nt get warm during loud playback what gives? Quote Link to comment Share on other sites More sharing options...
WMcD Posted June 17, 2001 Share Posted June 17, 2001 I don't know if you want a discussion of the technical complexities in a general sense. What amp is this, I recall someone was waiting for a shipment. One thing is that there a several different types of circuits and components in the amp, all of which can create heat. One overall "problem" is that most discrete semi-conductors must have an overall 0.7 volt drop across them to even get turned on. Most of the semiconductors are "biased" "on" even without an input. Even with no input, they are not turned off. There is another phenomenon which is too complicated to go into here (meaning I can't explain it either). The semi-conductors, act as "valves" to allow the flow of current where it is wanted. In some designs, this means it is switching current either (1) to the speaker, or (2) to an internal circuit. Therefore, when the speaker is driven, the energy goes to the speaker. When the speaker is not driven, the energy is seen as heating of components within the amp. Transformers, even under low load, have some losses which will cause some heating. Gil Quote Link to comment Share on other sites More sharing options...
HornsRus Posted June 18, 2001 Author Share Posted June 18, 2001 Carver TFM 35x 250 wpc I just read feedback on this amp @AudioReview and found the same problem.Thanks for the reply. Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted June 18, 2001 Share Posted June 18, 2001 If you do a search on this board for "class a" and "class ab", you'll find several discussions regarding different approaches to designing amps that you might find interesting. To skip the technical bits and reasons why, amplifiers constantly run some current through the output transistors (or tubes) whether they're putting out a signal or not. Some folks believe that the best way to get the most accurate signal out of an amp is to run the full rated current through the transistors at all times, whether there's a music signal or not. When there's no signal, this current basically flows from source to ground, and does nothing but generate heat. When there is a signal, some of the current is "tapped off" and routed through the speakers. Theory is that by running a constant amount of current through the outputs and simply directing more or less of it to the speakers as the signal demands, the transistors (or tubes) don't have to switch "on and off" at all; they're fully on all the time. In this extreme case, the amp may be hottest when there's no signal at all, and the more power you direct to the speakers, the less you waste as heat, so the amp actually gets cooler when you're playing music loudly. This exteme case (it would be referred to as "fully biased into Class A") not only produces a lot of heat, it consumes enormous amounts of electricity for the power it produces. The old, original Mark Levinson Model 2 amps, for example, put out 25 watts per side, but sucked in hundreds of watts continuously. The other extreme is to have the outputs totally off unless there's a signal present, and then switch the outputs on only long enough to amplify the part of the signal they're responsible for, then switch 'em back off again. This is very efficient, and results in very little wasted power, but tends to sound really awful. Most amps are somewhere in between these two extremes. Your Carver sounds like it's fairly heavily biased towards the Class A side. I think the TFM series was built around the mutli-level power supply thingie he invented, where the power supply only puts out as much power as the load demands. This being the case, to get the best sound, the low power idle state may be biased heavily into class A, so that at low power levels you get the best possible sound. Then again, I work for a dot com. What do I know. Ray ------------------ Music is art Audio is engineering Quote Link to comment Share on other sites More sharing options...
Mighty Favog Posted June 18, 2001 Share Posted June 18, 2001 HornsRus- If you want I can scan in and email you the pages from Carver's product catalog from about 1984. It explains your power supply amp pretty well. My recently purchased Rotel amp gets rather hot as well when it's idling. Althought Rotel couldn't tell me at what power output Class A ends and Class A/B begins. RB-1080 with 200wpc consuming 500 watts; doesn't sound like too bad of a mismatch (I think . ------------------ Tom KLF-20 Mahogany McIntosh C33 (In the Hospital) Rotel RB-1080 Yamaha PF-800 Turntable/ Sure V15 Type V Cartridge Ortofon VMS-30 Cartridge Stanton 999SS Cartridge Carver TL-3100 CD Yamaha K-1020 Cassette (maybe being mothballed) dbx 1231 EQ H.H. Scott 830z Analyzer Monster Interlink 400mk II Monster Interlink 300 mk II Studio Tech U-48RW Cabinet Original 12ga. Monster Cable Enough boxes for a fire hazard! This message has been edited by tblasing on 06-18-2001 at 05:35 PM Quote Link to comment Share on other sites More sharing options...
maxg Posted June 19, 2001 Share Posted June 19, 2001 "My recently purchased Rotel amp gets rather hot as well when it's idling. Althought Rotel couldn't tell me at what power output Class A ends and Class A/B begins. RB-1080 with 200wpc consuming 500 watts; doesn't sound like too bad of a mismatch (I think " hmmm - that is odd. I had the same unit and never noticed it running even warm. May be a problem brewing there for you - mine was on 24*7. Quote Link to comment Share on other sites More sharing options...
stormin Posted June 19, 2001 Share Posted June 19, 2001 I talked with the tech wizards at Adcom today and they informed me that the Adcom GFA 555 mkII that i have runs class A for the first 20 watts then class AB from there on out. So i guess since i have the chorus II's with 101/1 watt/1 meter that i probably never leave class A. Cause at 16 watts i am at 113 db's which is run you out of the room loud. But on the other hand i have heard from some BB members that adcom wasnt a good match for them so go figure. Maybe some actually like class AB better than class A. Cause there are some SS amps that only run class AB. Just put me down as another seeker of the audio truth. Quote Link to comment Share on other sites More sharing options...
Guest polymon Posted June 21, 2001 Share Posted June 21, 2001 A couple of thoughts: The "TFM" stands for "Transfer Function Modified". Bob was once challenged by some folks to prove his claim that he could virtually duplicate the characteristic sound of any amplifier. Big Claim! He locked himself in a motel room for 24 hours and emerged with a Carver amp with a Magnetic field power supply (the theoretic precurser of Sunfires'tracking downconverter) that had been tweaked to match a tube amp (a CJ, if memory serves me correctly). All who listened to the two amps agreed that he had come pretty close to matching the tube amp's timbre, but it didn't have the exact same sound. He later built an amp called the Silver Seven, a mono-block tube amp, whose sound he used as a reference for all the Carver "TFM" amps. Your amp is probably one of the off-shore, non-THX certified versions. If that's the case, this amp has the bizzare trait of running cooler the louder you play it. This is due to the fact that he DOES have the outputs biased heavily towards class a (outputs always have voltage)when idle and for the first few watts of output.as you start getting on it, the amp draws more voltage from the wall as needed and operates very much like a class AB amp with a "digital" power supply. Klipsch uses an amp design in the KSW 15 and upcoming RSW-15/12/10 called a BASH amp, or digital hybrid amp. The difference between this and the MFPS is that the Craver has a lot of current on the rails at idle, which is why it runs hot. The BASH implemntation uses voltage/current only when there is a signal at the inputs and ramps the supply up according to the signal's modulation and amplitude. Sounds like an ideal amp! Unfortunately this and "class-D" amps sound pretty awful above the third octave because of the amount of switching and power supply modulation used. TFM-35 amp was always a great value, with lots of bang for the buck, and it has great sound quality. The only real difference on the on-shore THX version is a stiffer power supply which was required to meet the continuous full-bandwitdh output requirement for THX approval. I'll shut up now. Go enjoy your new amp! ------------------ Polymon Quote Link to comment Share on other sites More sharing options...
Guest polymon Posted June 21, 2001 Share Posted June 21, 2001 OOPS! You DID say TFM35x, so you have the THX version....Nice amp ------------------ Polymon Quote Link to comment Share on other sites More sharing options...
HornsRus Posted June 21, 2001 Author Share Posted June 21, 2001 Yes its the THX version.Thanks again Tblasing for the information.Thanks again for the replies. This message has been edited by HornsRus on 06-21-2001 at 05:20 PM Quote Link to comment Share on other sites More sharing options...
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