What is a harpamp?

Monopoly Fender

There are also other great guitar amps, why do the player, hobbyists and manufacturers always use fender circuits?
Guitar combos were available in the United States from around 1930 and were produced by companies like Kay, Rickenbacher and Gibson. They mostly corresponded to the power amps from larger tube radios and amplified acoustic guitars and lapsteel. But they were not very widespread.

At that time, Leo Fender was an ambitioned hobbyist and opened his music store in 1939. The fender company was established in 1946, after moving to larger rooms. His success is based on the fact, that he was the first that offered solid body guitars and purist amplifiers. For that he was smiled at first, but a short time later his products were sold in large quantities and soon became dominant on the second-hand market.
His sound was the "singing cowboy", who could play his Tele/Strat out loud. The distortion was an unwanted side effect that got established as "Sound" by chronicly turned up amplifiers, because it offered new opportunities.
In the 50s, Fender was copied a lot. Only in the 60s other companies startet the development of more complicated circuits with accessible distortion. Leo remained faithful to the clean sound. And here ends the interesting time window for us.

At that time, a Fender product was still prohibitive and you could hardly get one in Europe.

The harp player just took, what was there. Simple Fender amplifiers and similar contemporary products, small PA systems for example by Masco and surely all kinds of handcrafted and converted. The process for the development of the "electric sound" has undergone faster with the harp, founded by the overtone-rich sound. Also the guitar already made it acceptable.

A provocative topic, everyone has an opinion and taste, also depending on experience and knowledge, as well as the situation in which you find yourself. At a concert, you are probably in a "good mood", also a reference is missing... my senses often deceived me.

The next problem is that the player has immense influence on the sound, and not only because of the technique but also the dealing with the amplification equipment. A common saying: "bass and distortion comes from the player", but not everyone needs bass and distortion for his style. I am talking about the problem cases, which also use a good amp.

Not to forget: sound can hardly be described in words! This might work, if you know each other and have common experiences: "the amp sounds as compressed as your fender concert at song 7 on the "Ducktales".

And last but not least, a recording is influenced by the recording technique. But even in recordings with modern technology I could not hear what I heard in real. Therefore, I believe that it's risky to attach much importance to sound files. And especially in times of tablets and smartphones, the technique should also be reasonable, in high quality and even linear.

If "the harp sound" cannot be described, perhaps you get an impression with examples of "good sound" and "quirky sound". It's always about the sound of the recording, not about the sound of the instrument/amplifier.