JTM-1

[Thereminator]

http://www.handmades.com.br/forum/index ... pic=5841.0

[federerer]

W temacie jest, że jednak JTM-1. Ale i tak miło pooglądać. Sprzężenie zwrotne na siatkę inwertera, ciekawie - nigdy nie testowałem takiego sposobu.

[o-----c]

http://i24.photobucket.com/albums/c38/j ... G_8968.jpg


http://i24.photobucket.com/albums/c38/j ... G_8969.jpg

[szugon]

Jaką rolę pełnią elementy C23, R35, R36 oraz C2, D5,D6?

[Krzysiek16]

Ustalają potencjał chassis. C2 stanowi zwarcie dla w.cz., natomiast diody nie pozwalają na pojawienie się na chassis napięcia większego niż +/-0.6V w stosunku do bolca uziemiającego.

[Thereminator]

Trochę info o serii bezpośrednio od projektanta:

http://www.ax84.com/bbs/dm.php?thread=460389

Here's the skinny on the 1 watts.

The 5 models were designed by three engineers here. I did the 60s and the 80s, the 70s was by another engineer, Steve and the 90s and 00s were by Santiago.

All the amps are push pull ECC82/12AU7 except the 70s which is single ended ECC81/12AT7.

The 60s and 80s are both 3 gain stages with cathodyne PI as has been correctly suspected. The 90s and 00s use a long tail pair.

The 60s has an input stage that has a cathode r/rc network designed to imitate the frequency response of a jumpered input with a little more bright than normal volume level, then gain then anode follower then the tone stack from a JTM45 - 56k slope and 220p treble. Only the treble control is fitted as a tone control. Then there is another anode follower to the PI. There is about 6dB of NFB into the grid of the PI.

The 80s has the expected 2k7 680n cathode arrangement followed by the preamp volume then a clipper stage (works like a 10k but has a bit more gain) then the expected 820R biased stage and a LND150 follower. I experimented with omitting the MOSFET, but it was my opinion that the improvement in tone and feel was worth it. Then there is a cathodyne and the output. The NFB is similar to the 60s. The boost button changes the clipper stage to be effectively a mid biased stage and brings in the bridge and led clipper used in the Jubilee amps.

The 70s is a bit of a strange beast. The circuit has changed a couple of times and I have not kept up to date with it.

The 90s and the 00s are essentially the preamps from the amps of the period (DSL and JVM) with the ltp push pull power amps. Interestingly, Santiago and I did not agree on the OT impedance and they are quite different with mine quite a bit lower.

The low power mode was set in my house. While the family were in another room watching the TV, I turned up the power until I got a complaint and set it a little lower. In this mode, the OT is fully loaded and I have used 1 watt amps driving the effects loop of a bigger amp. This is particularly effective when there is an event where there are several bands and the backline is supplied. I could get my tone with the minimum of fuss.

I hope this answers a few questions.

James
=0^0=