Gaussmarkov's Boss BD-2 clone: problems and questions

[gigimarga]

Sometime ago I've built a clone of a Boss BD-2 (one of my favourite pedals) using Gaussmarkov's project (thanks a lot Paul for your fabulous projects!): http://gaussmarkov.net/layouts/bd2/bd2-project.pdf

It sounds good, but it doesn't sound as the original (I had two in the past!) which is clearer (let's say transparent) and have more gain.

I used 2N5457 for FETs, 2N3904/2N3906 for BJTs and NE5532 for the opamp (I'd built the vref opamp version).

So, my questions are:

1. It's possible that the missing buffers from Boss to make this difference?
2. How can I increase the gain?

Thx all!

[cctsim]

The BD-2 has a common-basis transistor (Q2) that drops the supply voltage for the discrete discrete op-amps to 8V and the reference voltage to 4V.

This is missing in the gaussmarkov BD-2 clone, which will make the sound different from the original.

[gigimarga]

Thx cctsim for your answer!
I've built the 8V version according to this paragraoh from the site: "We have removed the input and output buffers and the switching circuitry. The power supply is also simpler. Our version runs at 9 volts, whereas the original runs at 8 volts. Nevertheless, we are providing two versions: one with, and one without, an op amp buffer for the the voltage reference supply that appears in the original Boss schematic"

[cctsim]

What kind of jfets did you use ? This may be critical.

I built mine with 2N5458s and it sounds very similar to the stock BD-2. I tried to find ones that were closely matched though.

I have also used separate gain controls so that I can adjust the pre/post clipping gain individually.

[gigimarga]

Thx cctsim!

I used some 2N5457 with no match. I will try to wire two independent gain pots and to see what's happening

[aziltz]

did you get a lot more useable sounds out of two gain pots?

[gigimarga]

did you get a lot more useable sounds out of two gain pots?

I was out of my home this weekend, so I didn't have time to make this mod yet

[aziltz]

What about a mod/knob or toggle that switches the supply from 9v down to 8v, i think that would be pretty kick ass if they're are good sounds at both levels...

[gigimarga]

What about a mod/knob or toggle that switches the supply from 9v down to 8v, i think that would be pretty kick ass if they're are good sounds at both levels...

I will test all my batteries and I'm sure I will find one at 8V

[gigimarga]

Anyone knows which type are the FETs used in the original Boss BD-2?
All the schematics that I found are unclear...it seems to me to be 2SK1840, but I am not sure!

[gigimarga]

Nobody knows?

[cctsim]

The right type is 2SK184-GR. The same type is used also on OD-3 and DS-2 in a similar type of discrete opamp circuit.

[gigimarga]

The right type is 2SK184-GR. The same type is used also on OD-3 and DS-2 in a similar type of discrete opamp circuit.

Thx a lot cctsim
Have you any ideea if BF245 or BF244 are OK to substitute 2SK184?

[cctsim]

The right type is 2SK184-GR. The same type is used also on OD-3 and DS-2 in a similar type of discrete opamp circuit.

Thx a lot cctsim
Have you any ideea if BF245 or BF244 are OK to substitute 2SK184?

The BF245A and BF244A models are the closest substitute.

The B and C models have a Vgs min/max range that has no overlap with the 2SK184.

[gigimarga]

The right type is 2SK184-GR. The same type is used also on OD-3 and DS-2 in a similar type of discrete opamp circuit.

Thx a lot cctsim
Have you any ideea if BF245 or BF244 are OK to substitute 2SK184?

The BF245A and BF244A models are the closest substitute.

The B and C models have a Vgs min/max range that has no overlap with the 2SK184.

Thx a lot again cctsim!

I've just looked at the datasheets and you're right about the VGS min/max and the IDSS min/max ranges:
1) 2SK184-GR: -0.2/-1.5 V and 2.6/6.5 mA
2) BF245A   : -0.4/-2.2 V and 2.0/6.5 mA   
3) 2N5457   : -0.5/-6.0 V and 1.0/5.0 mA

So, it seems to me that BF245A is a better susbstitute for 2SK184-GR than 2N5457!

I will try to change the 2N5457s to BF245A and to drop the power supply from 9V to 8.2V using a Zenner diode

[gigimarga]

I replaced 2N5457 with two pairs of matched BF245A (first at -0.7V and second at -0.9V), i replaced D7 with a 8.2V Zenner, I powered it thorough a 33 ohms resistor (I hope that I calculated it right for the Zenner) and I replaced the two 18nF from the tonestack (C14/C15) with 33nF/22nF.

It sounds a little better (more gain), but still far away from the original .

I tried to add a 100k pot in series with R11(15K from the fixed tonestack) to control the mids, but it oscillates very quickly (after 10-20K).

[gigimarga]

Somebody has the right voltages?

[oomnelson]

Hi!, what happened at last?, did you find the same tone as the original?...

I made the project using 2SK117 as jfets. It works better than the BF245 for my taste.
The IC I use is the 4559, which is a direct replace for the M5218AL, which is the Boss BD-2 original IC.
And after all, I applied to my project all the Keeley mods.
I can´t compare it side by side with the original BD-2 yet, but I will do. Moreover, I find it works perfect, the sound is great.