بين آمپلي فايرهاي ترانزيستوري و هيبريد (خروجي SS) كمترين فيدبك رو برندهاي زير دارند :

Vitus , Ayre , Ypsilon , Dartzeel , Firstwatt J2 , Dan Dagostino , Hovland, Naim

بين آمپلي فايرهاي Tube كمترين فيدبك رو برندهاي زير دارند :

Audiopax , Audio Note , Border Patrol , Wavelength Audio , Leben , Lamm ML3 , PrimaLuna , Sophia Electric , Wavac , Antique Sound Lab

بین مدلهای Lamm فقط مدل Lamm ML3 فیدبک نداره. مدل های جدید Airtight فیدبک منفی دارند.

من نظرم اينه نداشتن فيدبك منفي شرط لازم براي صداي خوب هست و نه كافي و با ديدن اين ليست اول اونايي كه تو ليست فيدبك منفي بالايي دارند رو حذف ميكنم و بعد اونايي كه فيدبك منفي كمي دارند رو سعي ميكنم بشنوم ببينم صداشون چطوره.
لازم به توضيح هست توپولوژي هاي مختلف رو نبايد با هم مقايسه كنيد واسه همين من لامپي رو از ساليد استيت جدا كردم و بين ساليد استيت ها هم اونايي كه ترانس خروجي دارن وضعيتشون متفاوته.

A Future Without Feedback?
When Black proposed negative feedback in 1927, he was trying to solve a specific problem: the deep cascading of imperfect, transformer-coupled tube amplifiers. But has anyone explored the implications of negative feedback for reproduced sound quality in the absolute sense?

Based on my experience of the pairing of a zero-loop-feedback preamplifier and amplifier, and supported by the evidence that amplifier designers consciously or unconsciously attempt to reduce negative feedback to improve subjective quality—even if this means worsening the measured performance—we need to reconsider the subject.

It is possible that engineers need to rethink how audio systems should be designed. Before the introduction of transistors limited to low voltages, which forced the speaker industry down to 8 and 4 ohm impedances, speakers were typically 8 to 16 ohms, did not need thick cable to wire them up, achieved maximum electromagnetic utilization at good efficiency, and were well matched to tube amplifiers. Higher efficiency spells better dynamics, reduced thermal compression, and the potential of using smaller, more perfect power amplification. But if speakers were designed to have smooth impedance curves, to be relatively uncritical of amplifier or cable matching, and to offer higher sensitivity, we would have greater freedom to examine the feedback question and the validity of the low-power, short-path, zero-feedback approach.

We still have much to learn about the art of sound reproduction; ultimately, our responsibility is to our ears, not to established precepts.