REDDI DI

[Jim50hertz]

Thanks Ian 8)

 

[dirty1_1garry]

Here is what I've got at this moment!))

I done my tube di pcb based on schematics in this thread with minor changes. But when unit was build I found couple mistakes on pcb, so now it's in recast. As there was a mistake on that version of pcb, so I just make a signal circuit p2p separately and use pcb as power supply only.

Output transformer is a custom made and sounds very very close to the huge 2kilogram edcor CXSE25-600-5K that I used in my first build.

 

[ruffrecords]

Very professional looking build Garry. Well done.

Cheers

Ian

 

[diggy fresh]

Good job guys!

Very interested in this and pcbs!

 

[guy_4]

" Very interested in this and pcbs! "

Me too ! 
Guy

 

[Winetree]

I'd like to build a stereo unit.

 

[dirty1_1garry]

Will let you know asap)

 

[raydee]

Very interested in this and pcbs!

Me too  (is this an allowed first post?)

 

[SirCVH]

Garry do you still plan on making up pcb's for this project?  I was planning on making up some of my own for myself as I want to learn eagle anyways, but will learn on a different project if you are going to make them.

Thanks!

 

[critterkllr]

Any thoughts on adding an Ampeg B15N tone stack to the DI?  Perhaps making it switchable? I haven't seen something like that on a DI, so I'm wondering if this isn't the right place in the signal chain for a tone stack.

 

[CJ]

a simple yet effective tone control is to put a switch on the cathode bypass cap,

switched in for bass
switched out for guitar

 

[critterkllr]

Hmm, not a bad idea. Or perhaps a 25uF cap like a lot of other guitar amps? I'm just looking for another step closer to a B15 tone. I'm considering building this PTP. The parts cost to add the tone stack won't be much. I just wonder if there will be too much signal loss by putting it in this circuit.

 

[abbey road d enfer]

Hmm, not a bad idea. Or perhaps a 25uF cap like a lot of other guitar amps? I'm just looking for another step closer to a B15 tone.

90% of the B15 tone is in the loudspeaker.

 

[critterkllr]

Hmm, not a bad idea. Or perhaps a 25uF cap like a lot of other guitar amps? I'm just looking for another step closer to a B15 tone.

90% of the B15 tone is in the loudspeaker.

Gotcha. Thanks for chiming in. I guess I still need to get a B15...

 

[SirCVH]

a simple yet effective tone control is to put a switch on the cathode bypass cap,

switched in for bass
switched out for guitar

I have been looking into adding a cathode bypass adjustment as I am currently building this project.  I am going to add a pot to both bypass cap circuits, and was wondering if there is a way to calculate the best value for the variable pot, best meaning a full tone sweep between no capacitance and full capacitance on the 470uf cap with minimal wasted turn space on the pot.  Would you just start at a 1m pot and work your way down?  Pardon my sketch:

Thanks for any help

 

[abbey road d enfer]

a simple yet effective tone control is to put a switch on the cathode bypass cap,

switched in for bass
switched out for guitar

I have been looking into adding a cathode bypass adjustment as I am currently building this project.  I am going to add a pot to both bypass cap circuits, and was wondering if there is a way to calculate the best value for the variable pot, best meaning a full tone sweep between no capacitance and full capacitance on the 470uf cap with minimal wasted turn space on the pot.  Would you just start at a 1m pot and work your way down?  Pardon my sketch:

Thanks for any help

The main effect of modifying the cathode bypass is changing the gain. Don't expect any spectacular change in tone. Using a pot in this position is very subtle. For a typical 12AX7 input stage, the variation would be about 5dB.
That may be different with a much lower value of the capacitor (0.047-1uF), the minimum resistance position of the pot giving a significant HF rise.
With a 220r cath res, a 1Meg pot will behave exactly like a switch, nothing for 99% of the rotation and a rather moderate change on the remaining 1%.
I would use a pot value about 5-10 times the cath res. A rev Log taper would be recommended (or a standard log taper, but the maximum effect will be in the CCW position). Lin taper will definitely be cramped at one end.

 

[SirCVH]

The main effect of modifying the cathode bypass is changing the gain. Don't expect any spectacular change in tone. Using a pot in this position is very subtle. For a typical 12AX7 input stage, the variation would be about 5dB.
That may be different with a much lower value of the capacitor (0.047-1uF), the minimum resistance position of the pot giving a significant HF rise.
With a 220r cath res, a 1Meg pot will behave exactly like a switch, nothing for 99% of the rotation and a rather moderate change on the remaining 1%.
I would use a pot value about 5-10 times the cath res. A rev Log taper would be recommended (or a standard log taper, but the maximum effect will be in the CCW position). Lin taper will definitely be cramped at one end.

I see, thank you for your feedback, I really appreciate it.  If the impact is this subtle in this application, I will probably just stick with a switch and call it good.  Thanks!

 

[CJ]

you can combine both cathode caps into one big one, and use a single cathode resistor

makes wiring the cathode circuit easier and installing the switch easier also,

divide cathode resistor by 2 if using one resistor,

you can really hear the difference with the switch in or out at the low freqs,

 

[abbey road d enfer]

you can really hear the difference with the switch in or out at the low freqs,

That would be tha case if the capacitor had a much lower value. With 470uF, as shown on the schemo, the variation of frequency response would appear below 1Hz.

 

[CJ]

build one yourself and try it out,