Probleme termice la amplificatoare

[adyy35]

pioneer n50a

[silviu2403]

Am si eu o intrebare, de ce sa faci un amplificator cu 0.5v pe intrare cand mai toate sursele au 2v? Chiar cd-ul Naim 5si vad ca are 2.1v pe iesire?

Acestea sunt spec amplificatorului:

Audio Inputs

Input Sensitivity

150mV

Input Impedance

20kΩ

Analogue Input

2 x DIN, 4 x RCA

Audio Outputs

Line Outputs Fixed (level)

150mV, 600Ω

Audio Outputs

Speakers, HDD

Other Outputs

Headphone, 1/4" jack

Speaker Outputs

Power Output

60W/channel, 8Ω

Transient

300VA

Connectivity

Remote Control

Infra Red (RC5)

User Control

Front Panel

Volume Control, four button matrix

Power

Mains Supply

100V, 115V, 230V; 50 or 60Hz

Power Consumption (max.)

300VA

Power Consumption (quiescent)

19VA

Physical

Dimensions (HxWxD)

70 x 432 x 301 mm

Weight

6.8 kg

Shipping Dimensions

200 x 590 x 500 mm

Shipping Weight

8.6 kg

Supplied with

NARCOM-4 Remote Control

[CPT]

Acum ceva ani buni standardul era de 775mV adica 0db. La japonezi erau 410mV iesirw linie la "liniile" Akai si 580mV la reducatoarele de zgomot Dolby.

Acum este un haos, fiecare face dupa stilul lui.

[Jack]

pioneer n50a

 

Dupa cum se vede in link http://global.rakuten.com/en/store/jism/item/4988028264931-35-25345-n/

Audio output level: 2.2 V

Naim Nait 5si : Input sensitivity : 0,15V https://www.naimaudio.com/product/nait-5si

Daca ai folosi o sursa cu 0,15V pe iseire, cu inregistrari corecte, ai putea sa dai potentiometrul la maxim fara probleme. Asa, intrind cu de mai mult decit 10X semnal, e firesc ca la u anumit moment resursele sa fie depasite. Chiar daca ai avea putere mai mare, toate amplificatoarele au o componenta in tensiune si una in curent. Au un voltaj si un amperaj maxim. Daca ai un GAIN de 35-40dB ( aprox 20x, nu stiu exact formula, dar cu siguranta un electronist ne poate spune ), inseamna ca daca intri cu un voltaj mai mare, amplificatorul se "satureaza" mai repede decit cu un voltaj mai mic, fireste ca invirtind mai putin de potentiometru.

Personal, nu stiu daca am ascultat vreodata orice NAIM sau chiar orice amplificator cu potentiometru similar la o cursa mai mare decit "ora12", dupa acest nivel intrind deja in domeniul distorsiunilor samd. Bineinteles, vorbesc de surse digitale moderne, cu aprox 2V output.

[Jack]

Am si eu o intrebare, de ce sa faci un amplificator cu 0.5v pe intrare cand mai toate sursele au 2v? Chiar cd-ul Naim 5si vad ca are 2.1v pe iesire?

Acestea sunt spec amplificatorului:

Audio Inputs

Input Sensitivity

150mV

Input Impedance

20kΩ

Analogue Input

2 x DIN, 4 x RCA

Audio Outputs

Line Outputs Fixed (level)

150mV, 600Ω

Audio Outputs

Speakers, HDD

Other Outputs

Headphone, 1/4" jack

Speaker Outputs

Power Output

60W/channel, 8Ω

Transient

300VA

Connectivity

Remote Control

Infra Red (RC5)

User Control

Front Panel

Volume Control, four button matrix

Power

Mains Supply

100V, 115V, 230V; 50 or 60Hz

Power Consumption (max.)

300VA

Power Consumption (quiescent)

19VA

Physical

Dimensions (HxWxD)

70 x 432 x 301 mm

Weight

6.8 kg

Shipping Dimensions

200 x 590 x 500 mm

Shipping Weight

8.6 kg

Supplied with

NARCOM-4 Remote Control

 

Probabil ca pentru a putea fi folosit cu surse mai vechi, care aveau output-ul mai mic, pentru eventuale phono-stage-uri , care fie au output mic, fie nu asigura suficient gain. Sunt doar niste speculatii, poate electronistii ne pot raspunde mai coerent. Mi-am pus si eu intrebarea, aceasta situatie nefiind specifica NAIM-ului, ci mai tuturor brand-urilor.

[Shibata]

Pare logic ce spune Jack.

In alta ordine de idei: pe vremuri nu cumparai sculele de la zece producatori, ci cumparai o linie audio, formata din scule din aceeasi serie. Fiecare producator avea la vanzare intr-un anumit moment o serie economica, una de mijloc si una de top. O serie cuprindea totul, de la acul pickupului pana la tweetere: Pickup, tuner, cass, amplif, boxe. Le cumparai impreuna, le puneai intr-un rack (unele peste altele) si aveai muzica. Ba mai mult, designul sculelor dintr-o serie era unul unitar (dispunerea butoanelor, dispunerea ledurilor, elementele decorative de pe panourile frontale, etc... Priveai rackul plin si iti bucura privirea, ca un tablou. Desigur ca nici nu se punea atunci problema de matching intre scule, totul fiind perfect calculat cap-coada. Erau vremuri frumoase daca aveai banii necesari.

[silviu2403]

Si acum sunt vremuri frumoase daca ai banii necesari. Si acum producatorii au grija ca sculele lor sa mearga bine impreuna, sau cel putin asa vreau sa cred.

Chestia cu volumul am observat-o si eu la amplificatoarele cu volum clasic cu potentiometru, majoritatea dupa ora 11-12 nu prea mai stau bine la capitolul distorsiuni. Ai impresia ca ai multa putere, incepe sa impinga difuzoarele repede, la ora 9-10 deja se simte bine muzica, insa se plafoneaza la 11-12. De ceva timp am in sistem un amplificator care are o altfel de abordare a volumului, pleaca de la -80db volumul si are si o scala de putere. La -20db furnizeaza doar 25% din puterea lui totala, urcand exponential de pe la -10db. In felul asta volumul este foarte fin si nu simti ca dai prea tare dintr-o data. Pe langa acest lucru, toate intrarile analogice au optiunea de a seta sensibilitatea intrarii pentru o potrivire cat mai buna cu sursa. Amplificatorul este cyrus 8a.

[Andi]

Nu e exact invers? Cu cât ai output mai mic la sursă, deci ai nevoie de gain mai mare, cu atât apar mai multe probleme în amplificator?

În fond, nu prea există surse cu output sub 1,8 V, doar entry-leveluri.

[Jack]

Si acum sunt vremuri frumoase daca ai banii necesari. Si acum producatorii au grija ca sculele lor sa mearga bine impreuna, sau cel putin asa vreau sa cred.

Chestia cu volumul am observat-o si eu la amplificatoarele cu volum clasic cu potentiometru, majoritatea dupa ora 11-12 nu prea mai stau bine la capitolul distorsiuni. Ai impresia ca ai multa putere, incepe sa impinga difuzoarele repede, la ora 9-10 deja se simte bine muzica, insa se plafoneaza la 11-12. De ceva timp am in sistem un amplificator care are o altfel de abordare a volumului, pleaca de la -80db volumul si are si o scala de putere. La -20db furnizeaza doar 25% din puterea lui totala, urcand exponential de pe la -10db. In felul asta volumul este foarte fin si nu simti ca dai prea tare dintr-o data. Pe langa acest lucru, toate intrarile analogice au optiunea de a seta sensibilitatea intrarii pentru o potrivire cat mai buna cu sursa. Amplificatorul este cyrus 8a.

 

nu e ceva iesit din comun, probabil e potentiometru digital. Lafel e si la Creek-urile noi, te poti apropia cu volumul de "0", mai ales cu gain unitar. DAR, ca in toate exista reversul medaliei, potentiometrele digitale, in ciuda unui mai bun control asupra nivelului, sunt foarte controversate dpdv al sunetului. E inutil sa spun ca potentiometrul de volum este o componenta cruciala pe calea semnalului, dpdv al calitatii acestuia, f. multe alterari se intimpla acolo.

Mai exista si solutia cu retea de rezistente si relee, dar e una exotica, scumpa, ma indoiesc ca la cyrus e cazul. E implementata in pre-urile de top de la VTL si altele

[CPT]

Daca exista o schema la acest Naim, se poate modifica foarte usor sensibilitatea (in sensul micsorarii ei), pentru a "adapta" aparatul la sursele moderne cu nivel de iesire mare.

N-as vrea sa fiu rau, insa poate la Naim, sensibilitatea mica necesarra la intrare ca nivel (150mV din cite am citit in acest topic), a fost ca o strategie pentru comparatia amplificatoarelor de catre cei mai putin stiutori, adica, domne Naim-ul asta cu potentiometrul de volum la ora 10, suna "mai tare" decit ampliful X cu potentiometrul la ora 13.

Iti dai seama "ce scula e"? Volum mai mic deci si zgomot de fond mai mic (nestiind ca o amplificare mai mare), obligatioriu are si un zgomot de fond mai mare...

Intelegeti voi mai bine ce vreau sa subliniez.

[audio]

Totusi cati ani are amp-ul asta, al meu are vre-o 6 ani si are 3.8v pe single ended si 7.8v pe balansat, si sensitivity de 0.5v si 1v balansat. Nu am observat diferente intre surse si nu am reglat gainul pe intrare la vre -un canal,se poate face acest lucru din meniu, merge volumul pana in capat si nu pierde nimic peste ora 12, cred ca e potentiometru digital, butonul merge usor (in gol).

[brainsmartman]

pioneer n50a

 

Dupa cum se vede in link http://global.rakuten.com/en/store/jism/item/4988028264931-35-25345-n/

Audio output level: 2.2 V

Naim Nait 5si : Input sensitivity : 0' date='15V https://www.naimaudio.com/product/nait-5si

Daca ai folosi o sursa cu 0,15V pe iseire, cu inregistrari corecte, ai putea sa dai potentiometrul la maxim fara probleme. Asa, intrind cu de mai mult decit 10X semnal, e firesc ca la u anumit moment resursele sa fie depasite. Chiar daca ai avea putere mai mare, toate amplificatoarele au o componenta in tensiune si una in curent. Au un voltaj si un amperaj maxim. Daca ai un GAIN de 35-40dB ( aprox 20x, nu stiu exact formula, dar cu siguranta un electronist ne poate spune ), inseamna ca daca intri cu un voltaj mai mare, amplificatorul se "satureaza" mai repede decit cu un voltaj mai mic, fireste ca invirtind mai putin de potentiometru.

Personal, nu stiu daca am ascultat vreodata orice NAIM sau chiar orice amplificator cu potentiometru similar la o cursa mai mare decit "ora12", dupa acest nivel intrind deja in domeniul distorsiunilor samd. Bineinteles, vorbesc de surse digitale moderne, cu aprox 2V output.[/quote']

 

Uite aici o discutie facuta de un nene de meserie, plictisit de atatea intrebari despre "ora" volumului:

"Time for one of those long, boring semi-technical posts that no one here reads... :boring:

There have been various posts from people who have just acquired a "new" vintage amplifier, have connected it up to their speakers and fed it with a nice clean signal from a (relatively) modern CD player, and have commented along the lines of "I only turned the volume up to 10 o'clock and the whole house was shaking - boy that amp is powerful".

They never seem to consider that their amplifier might well be producing near to full output power even though the volume control is nowhere near maximum - a consequence of the sensitivity mis-match between vintage and modern equipment.

It seemed to me that it would be useful to go over a few basics regarding the decibel (dB) scale and how it relates to the sensitivity of the inputs on vintage amplifiers.

First a few basics about the dB scale (and a little bit of math - but nothing too difficult ) :

1. The decibel is a relative rather than an absolute measurement, i.e. it is used to measure the ratio of one signal to another. I am sure everyone is most familiar with it's use in representing the signal to noise ratio of equipment.

2. Positive dB values mean that a signal is greater than the reference value (ratio greater than 1), negative dB values that it is less than the reference (ratio less than 1).

3. If a signal passes through a number of amplification (+dB) or attenuation (-dB) stages, then the overall gain is found by simply adding up the dB values of each stage. For example, assume a signal passes through components with the following typical gain : phono amplifier +60dB, pre amp -20dB, power amp +30dB : The overall gain is therefore +70dB.

4. To convert the ratio between two voltages, V1 & V2, to decibels we use the formula : dB = 20 * log(V1 / V2)

A doubling of voltage = +6dB.

Conversely, to convert a dB value to the ratio between two voltages use the formula : Voltage Ratio = 10^(dB value / 20)

(The symbol "^" means "to the power of").

5. To convert the ratio between two powers, P1 & P2 to decibels we use the formula : dB = 10 * log(P1 / P2)

A doubling of power = +3dB.

Conversely, to convert a dB value to the ratio between two powers use the formula : Power Ratio = 10^(dB value / 10)

So back to the original question : Just how far do we have to turn up the volume to get maximum output power from our amplifier?

Look at your amplifier's manual and find the sensitivity value for the input you are using. The value it gives is the input voltage required in order to produce maximum rated power when the volume control is set to maximum. If the input signal you are feeding to the amplifier is greater than the sensitivity value, then maximum output power will be produced before full volume on the control.

Let's work through a real example to make things easier to follow (using data for my Pioneer SX-1250 receiver and Marantz CD-65SE CD player - typical of many vintage amp / modern CD player combinations) :

Input sensitivity of SX-1250 "Aux" (and "Tape") inputs : 150mV

Output voltage from CD-65SE at maximum signal level : 2000mV (2V)

So the CD player output signal is 20 * log(2000 / 150) = +22dB higher than that required for full output power from the SX-1250.

What this means is that the receiver's full power of 160 watts will be produced with the volume control set to -22dB (referenced to maximum = 0dB). Fortunately, in common with much high-end equipment, the SX-1250 has a volume control marked in -dB, making it easy to see where this occurs.

Perhaps the most "surprising" thing to come out of this calculation is just how little the volume needs to be turned up to get full output : -22dB on the SX-1250 corresponds to somewhere between the 11 and 12 o'clock positions.

So the next time someone tells you how loud their system is even at low "volume" settings (and implying that it would be ten times louder if turned up fully), just pause for a minute before you get too impressed and instead consider if they may have an amplifier/source sensitivity "mis-match". :scratch2:

Finally, we can apply the same calculations to the use of graphic equalizers and bass / treble / loudness controls. If +3dB of boost is applied at some frequency, then the power required at that frequency is doubled. If +10dB of boost is applied, then the power required increases by a factor of 10. So applying high levels of equalization (for example to compensate for the falling bass response of a speaker) massively increases both the power requirements of the amplifier and the handling capacity of the speakers."

Calculati si voi si vedeti cum sta treaba....

Si un alt sfat de la Oaktreevintage:

"ssue: At higher volumes, my sound, especially the bass, seems to distort, especially the bass and / or I get a 'sharp pop or snap' from my speakers...

A: All receivers / amplifiers have a limit to the power / volume they can safely produce. Most are going to 'red line' at approx 1:00 or 1:30 PM (looking at a 'rotary' volume control as a clock face) on the volume knob. Generally much past that does not result in any more power or actual volume, but simply an increase in distortion or amplifier clipping. I say "generally", as while there are some exceptions to this rule, they are VERY rare (Barney Oliver amplifiers and a Kenwood KA-6105 are the only two that immediately come to mind). Don't increase the volume past 1:00 or 1:30 (again, think of the 'rotary' volume control as a 'clock face', with 'straight up' being 12:00 Noon or 50% of it's rotation. If your unit has a 'linear-fader' style volume, then think of it as a percentage of it's total 'throw', so 55-60% would generally be max). Now there are many variables that affect those limits such as amplifier design, build-quality, speaker loads, designs and impedances, but again, the above 'rules' are generally applicable.

Also, Reduce 'Bass' and any of the lower bands of an EQ, either built-in or external EQ, proportionally as volume is increased past 10:00 AM.

Discontinue utilizing 'Loudness' control past approx 10:00 AM on volume control.

I've heard many people ask, "well why does my volume control go to 'ten' or all the way if I can't turn it all the way up? Well, it just does. Your accelerator goes all the way to the floor, your tachometer goes to 8 or 10k and your speed-o-meter probably goes to 120 or 130 MPH, but you don't generally want to go driving around that way for a lot of reasons. The same basic principle applies to the volume control and EQ on a receiver / amplifier."

Asta legat de nivele de 2 sau peste 2v la input pre de 150mV, da' la care tre' sa "merge" neaparat volumu' pan'la blana frate, ca d-aia e pus acolo... Ca nu-i normal sa nu merge!

Jack, +10!

[Jack]

pioneer n50a

 

Dupa cum se vede in link http://global.rakuten.com/en/store/jism/item/4988028264931-35-25345-n/

Audio output level: 2.2 V

Naim Nait 5si : Input sensitivity : 0' date='15V https://www.naimaudio.com/product/nait-5si

Daca ai folosi o sursa cu 0,15V pe iseire, cu inregistrari corecte, ai putea sa dai potentiometrul la maxim fara probleme. Asa, intrind cu de mai mult decit 10X semnal, e firesc ca la u anumit moment resursele sa fie depasite. Chiar daca ai avea putere mai mare, toate amplificatoarele au o componenta in tensiune si una in curent. Au un voltaj si un amperaj maxim. Daca ai un GAIN de 35-40dB ( aprox 20x, nu stiu exact formula, dar cu siguranta un electronist ne poate spune ), inseamna ca daca intri cu un voltaj mai mare, amplificatorul se "satureaza" mai repede decit cu un voltaj mai mic, fireste ca invirtind mai putin de potentiometru.

Personal, nu stiu daca am ascultat vreodata orice NAIM sau chiar orice amplificator cu potentiometru similar la o cursa mai mare decit "ora12", dupa acest nivel intrind deja in domeniul distorsiunilor samd. Bineinteles, vorbesc de surse digitale moderne, cu aprox 2V output.[/quote']

 

Uite aici o discutie facuta de un nene de meserie, plictisit de atatea intrebari despre "ora" volumului:

"Time for one of those long, boring semi-technical posts that no one here reads... :boring:

There have been various posts from people who have just acquired a "new" vintage amplifier, have connected it up to their speakers and fed it with a nice clean signal from a (relatively) modern CD player, and have commented along the lines of "I only turned the volume up to 10 o'clock and the whole house was shaking - boy that amp is powerful".

They never seem to consider that their amplifier might well be producing near to full output power even though the volume control is nowhere near maximum - a consequence of the sensitivity mis-match between vintage and modern equipment.

It seemed to me that it would be useful to go over a few basics regarding the decibel (dB) scale and how it relates to the sensitivity of the inputs on vintage amplifiers.

First a few basics about the dB scale (and a little bit of math - but nothing too difficult ) :

1. The decibel is a relative rather than an absolute measurement, i.e. it is used to measure the ratio of one signal to another. I am sure everyone is most familiar with it's use in representing the signal to noise ratio of equipment.

2. Positive dB values mean that a signal is greater than the reference value (ratio greater than 1), negative dB values that it is less than the reference (ratio less than 1).

3. If a signal passes through a number of amplification (+dB) or attenuation (-dB) stages, then the overall gain is found by simply adding up the dB values of each stage. For example, assume a signal passes through components with the following typical gain : phono amplifier +60dB, pre amp -20dB, power amp +30dB : The overall gain is therefore +70dB.

4. To convert the ratio between two voltages, V1 & V2, to decibels we use the formula : dB = 20 * log(V1 / V2)

A doubling of voltage = +6dB.

Conversely, to convert a dB value to the ratio between two voltages use the formula : Voltage Ratio = 10^(dB value / 20)

(The symbol "^" means "to the power of").

5. To convert the ratio between two powers, P1 & P2 to decibels we use the formula : dB = 10 * log(P1 / P2)

A doubling of power = +3dB.

Conversely, to convert a dB value to the ratio between two powers use the formula : Power Ratio = 10^(dB value / 10)

So back to the original question : Just how far do we have to turn up the volume to get maximum output power from our amplifier?

Look at your amplifier's manual and find the sensitivity value for the input you are using. The value it gives is the input voltage required in order to produce maximum rated power when the volume control is set to maximum. If the input signal you are feeding to the amplifier is greater than the sensitivity value, then maximum output power will be produced before full volume on the control.

Let's work through a real example to make things easier to follow (using data for my Pioneer SX-1250 receiver and Marantz CD-65SE CD player - typical of many vintage amp / modern CD player combinations) :

Input sensitivity of SX-1250 "Aux" (and "Tape") inputs : 150mV

Output voltage from CD-65SE at maximum signal level : 2000mV (2V)

So the CD player output signal is 20 * log(2000 / 150) = +22dB higher than that required for full output power from the SX-1250.

What this means is that the receiver's full power of 160 watts will be produced with the volume control set to -22dB (referenced to maximum = 0dB). Fortunately, in common with much high-end equipment, the SX-1250 has a volume control marked in -dB, making it easy to see where this occurs.

Perhaps the most "surprising" thing to come out of this calculation is just how little the volume needs to be turned up to get full output : -22dB on the SX-1250 corresponds to somewhere between the 11 and 12 o'clock positions.

So the next time someone tells you how loud their system is even at low "volume" settings (and implying that it would be ten times louder if turned up fully), just pause for a minute before you get too impressed and instead consider if they may have an amplifier/source sensitivity "mis-match". :scratch2:

Finally, we can apply the same calculations to the use of graphic equalizers and bass / treble / loudness controls. If +3dB of boost is applied at some frequency, then the power required at that frequency is doubled. If +10dB of boost is applied, then the power required increases by a factor of 10. So applying high levels of equalization (for example to compensate for the falling bass response of a speaker) massively increases both the power requirements of the amplifier and the handling capacity of the speakers."

Calculati si voi si vedeti cum sta treaba....

Si un alt sfat de la Oaktreevintage:

"ssue: At higher volumes, my sound, especially the bass, seems to distort, especially the bass and / or I get a 'sharp pop or snap' from my speakers...

A: All receivers / amplifiers have a limit to the power / volume they can safely produce. Most are going to 'red line' at approx 1:00 or 1:30 PM (looking at a 'rotary' volume control as a clock face) on the volume knob. Generally much past that does not result in any more power or actual volume, but simply an increase in distortion or amplifier clipping. I say "generally", as while there are some exceptions to this rule, they are VERY rare (Barney Oliver amplifiers and a Kenwood KA-6105 are the only two that immediately come to mind). Don't increase the volume past 1:00 or 1:30 (again, think of the 'rotary' volume control as a 'clock face', with 'straight up' being 12:00 Noon or 50% of it's rotation. If your unit has a 'linear-fader' style volume, then think of it as a percentage of it's total 'throw', so 55-60% would generally be max). Now there are many variables that affect those limits such as amplifier design, build-quality, speaker loads, designs and impedances, but again, the above 'rules' are generally applicable.

Also, Reduce 'Bass' and any of the lower bands of an EQ, either built-in or external EQ, proportionally as volume is increased past 10:00 AM.

Discontinue utilizing 'Loudness' control past approx 10:00 AM on volume control.

I've heard many people ask, "well why does my volume control go to 'ten' or all the way if I can't turn it all the way up? Well, it just does. Your accelerator goes all the way to the floor, your tachometer goes to 8 or 10k and your speed-o-meter probably goes to 120 or 130 MPH, but you don't generally want to go driving around that way for a lot of reasons. The same basic principle applies to the volume control and EQ on a receiver / amplifier."

Asta legat de nivele de 2 sau peste 2v la input pre de 150mV, da' la care tre' sa "merge" neaparat volumu' pan'la blana frate, ca d-aia e pus acolo... Ca nu-i normal sa nu merge!

Jack, +10!

 

Thx, Brain!

Ca o paranteza, o alta gresala incetatenita, faptul ca un amplificator cu cit e mai puternic, cu atit se aude mai tare. Partial adevarat, dar "cit de tare se aude" tine de GAIN-ul amplificatorului, astfel ca, putem asista la "paradoxuri" ca un amplificator de 200W ( de exemplu ) sa se auda mai incet decit unul de 40W ( aleator) in full power. Atsa presupunind ca (aceleasi) boxe sunt o sarcina usoara pentru a nu baga amplificatorul "mic" in clipping. Ca o paranteza la paranteza, acel "full power" nu are nici o legatura cu cursa potentiometrului, full power-ul poate fi atins la orice "ora" , functie de semnalul de intrare. Puterea mai mare, adica excursia in curent ( la acelasi gain ) isi va spune cuvintul in sustinerea sarcinilor dificile ale unor boxe, niste paramtrii superiori ai auditiei ( in special dinamica,dar si distorsiuni mai mici, separatie, etc. ). Putem traduce ca , de exemplu niste amplificatoare ale aceluiasi producator, din aceeasi serie, cel mai puternic va avea o separatie si dinamica mai buna pe pasajele aglomerate ( pe aceleasi boxe) decit cel mai slab.

In alta ordine de idei, faptul ca un amp. are o sensibilitate de intrare mica, nu e un lucru rau, cel putin nu relevant. Multi producatori dau un alt "parametru", "max. input level before clip " sau ceva de genul. Acesta in general e mai mare de 5-6 V la majoritatea amplificatoarelor moderne pe SE . O singura data mi s-a intimplat sa depasesc acest prag, cu o sursa digitala cu output cu lampi, folosind experimental niste tuburi "high gain" . Nu puteam asculta la niciun nivel, totul era o distorsiune. Am revenit la tuburi normale si totul a fost OK.

[camiloiu]

Eu am sesizat ca amplificatorul meu este mai cald atunci cand este pornit si sta degeaba decat atunci cand ascult la el