Bass guitar Hi-Fi 55W

[andrew]

I have an old book, DiY  - between 1975,1983 fifth  edition, I think that issued by the Ei NIS tube factory.
Can someone explain this topology.
Is this schematics cool for Jazz blues guitar or even acoustic guitar.
I come from Slovenia, end book is Ex Yugoslavia language.
 
Thnx
Andrej 

[HotBluePlates]

It is a push-pull ultralinear EL34 amp. It uses a split-load phase inverter which is fixed-biased. Feedback from the output transformer is returned to the stage before the phase inverter.


Input 1 has more gain than Input 2. There are 2 gain stages (with a volume control between) then a cathode follower into the tone controls. Input 2 has a single gain stage before the tone controls.


The tone controls are a James-style circuit where flat response is given with each control set half-up. You control midrange indirectly by setting treble/bass higher or lower to set them relative to the fixed midrange.


The pair of ECC83 stages just after the tone circuit is a feedback amplifier based on a 47kΩ (R18) and a 1.2MΩ (R21), which sets gain at 1.2M/47k = ~25.5.

Is this schematics cool for Jazz blues guitar or even acoustic guitar.

It should be good for clean guitar. It may manage a little distortion near full volume. You have basically two and a half gain stages before the output section of the amp. Input 2 should be very low-gain.

[andrew]

HotBluePlates! Thank yo for the quick response, I will now  redraw this schematics.
And I asked you, at what point at the schematics is a good for fx loop and Preamp output  - and Power input .
 
Sorry eng. Language.
 
Andrej
 

[sluckey]

I would insert two jacks at the junction of C17, R24, and R25. The jacks could function as a passive FX loop or preamp out/power amp in.

[andrew]

Thank you ! sluckey, I must redraw this schematics, this days, to improve transparency.
Which is the better system for master volume, the end of the preamplifier or in the final stage (power amp).
 
Thank you
andrej

[HotBluePlates]

I don't think this amp is a good candidate for a master volume. The low-gain architecture means you'e not likely to achieve much with a master volume.


If you're wanting the master volume because of the effects loop, it would make more sense if it was an active effects loop, with a gain stage after the return jack. And such a volume control could be just for the effects return, rather than the whole amp.

[kagliostro]

May be an idea to convert the triode used in the low level channel in a gain stage for the other channel ?


K

[HotBluePlates]

I would suggest breadboarding first, to see if the overall amp sound is worth messing with, or if he should build a more conventional guitar amp.

Is this schematics cool for Jazz blues guitar ...

Asking about jazz and blues in the same sentence means we don't know enough about which flavor of jazz or blues he intends to play. I'd think cleaner for jazz and distorted for blues, but depending on which artist you're pursuing, there is a wide range of what works for each (even very distorted for jazz and dead-clean for blues).