Vox and Orange Treble\Bass Boosters: Unity Gain?

[Mr.Kite]

Hi, I wanted to try on the breadboard these two circuits, let's start with the Vox...

I followed this schematic (http://www.luciferstrip.com/fuzz/vox-treble-bass-8041.jpg) and I also found this part list on ebay (https://www.ebay.com/p/Original-Vox-Treble-bass-Booster-V8401-Service-Information-Sheet/671333772), so same wiring but I used a 50k pot, 33k and 470k resistors, as in the part list...The value are confirmed in this pic of a rebranded JEN\Vox unit:



BC149B transistor, I used a BC109B (Hfe=286), it biases right at 1.75v at the collector (Vb=0.54v) with an healthy 9V battery. It sounds good too, it does what the name implies, it boosts bass and treble, or better, it scoops the mids, in fact I can hardly get above unity gain, it acts more as a "unity gain tone shaper" than an actual "volume\frequency boost" like an LPB-1 or a Rangemaster...my question is, is this normal? Is it by design? Or have I something funny going on?
Otherwise it seems a good sounding unit, but I don't have an original for comparison...

I should say that I tried first the "on board" version of some exotic Vox guitar\bass from the 60's (schematic found here https://www.acidfuzz.com/pages/vox-guitar-fx) but it was well below unity gain, although "perfectly" working and biased at 4.4v at the collector...

Next circuit, next schematic: http://www.geofex.com/FX_images/orngbst.gif

This one seems interesting...I tried an AC107 (Hfe=68, Leak=0.00mA) and an ASY80YTG (Hfe=62, Leak=0.04mA) and with stock resistors they both bias at about 5V, 5.3v and 4.9v IIRC, but I can get 7V or so by replacing the 80k with a 30k...anyway, it sounds good, it's a nice "Ge tone shaper" which works great with my "vintage modded" AC30, really great tones, as with the Vox, but again (as with the Vox) pretty much unity gain...is it right the bias for this unit? Are these units just "tone shapers" and are not supposed to "boost"?

Thanks for any help!

[PRR]

You have used the FTP linkage on your web-page links. This does not work form most of the Web.

You want HTTP .

I figured these:
http://www.geofex.com/FX_images/orngbst.gif
https://www.acidfuzz.com/pages/vox-guitar-fx

Both these should be reasonably high gain, though with lowish input impedance which may load-down some sources.

[Electric Warrior]

Hi, I wanted to try on the breadboard these two circuits, let's start with the Vox...

I followed this schematic (http://www.luciferstrip.com/fuzz/vox-treble-bass-8041.jpg) and I also found this part list on ebay (https://www.ebay.com/p/Original-Vox-Treble-bass-Booster-V8401-Service-Information-Sheet/671333772), so same wiring but I used a 50k pot, 33k and 470k resistors, as in the part list...The value are confirmed in this pic of a rebranded JEN\Vox unit:



BC149B transistor, I used a BC109B (Hfe=286), it biases right at 1.75v at the collector (Vb=0.54v) with an healthy 9V battery. It sounds good too, it does what the name implies, it boosts bass and treble, or better, it scoops the mids, in fact I can hardly get above unity gain, it acts more as a "unity gain tone shaper" than an actual "volume\frequency boost" like an LPB-1 or a Rangemaster...my question is, is this normal? Is it by design? Or have I something funny going on?
Otherwise it seems a good sounding unit, but I don't have an original for comparison...

I should say that I tried first the "on board" version of some exotic Vox guitar\bass from the 60's (schematic found here https://www.acidfuzz.com/pages/vox-guitar-fx) but it was well below unity gain, although "perfectly" working and biased at 4.4v at the collector...

Next circuit, next schematic: http://www.geofex.com/FX_images/orngbst.gif

This one seems interesting...I tried an AC107 (Hfe=68, Leak=0.00mA) and an ASY80YTG (Hfe=62, Leak=0.04mA) and with stock resistors they both bias at about 5V, 5.3v and 4.9v IIRC, but I can get 7V or so by replacing the 80k with a 30k...anyway, it sounds good, it's a nice "Ge tone shaper" which works great with my "vintage modded" AC30, really great tones, as with the Vox, but again (as with the Vox) pretty much unity gain...is it right the bias for this unit? Are these units just "tone shapers" and are not supposed to "boost"?

Thanks for any help!

My italian Jen treble and bass booster seems to be biased pretty close to your clone. Hardly any boost either. I guess that's just how they were set up.

[Mr.Kite]

Uh sorry!

Correct links:

- JEN\Vox v8401 Schematic: http://www.luciferstrip.com/fuzz/vox-treble-bass-8041.jpg

- JEN\Vox v8401 Part List: https://www.ebay.com/p/Original-Vox-Treble-bass-Booster-V8401-Service-Information-Sheet/671333772

- "On Board" Vox Guitar\Bass Treble\Bass Booster: https://www.acidfuzz.com/pages/vox-guitar-fx

- Orange Treble & Bass Booster Schematic: http://www.geofex.com/FX_images/orngbst.gif

Thanks Electric Warrior, I even found an old BC149B (Hfe=250) and the bias voltage seems pretty stable: Vc=1.78v, Vb=0.54v, 9.1V on the board, no major differences...

I played a little more with the two circuits and the Orange is definitely louder than the Vox, which is a nice tone shaper but not much "boost" to it...Both are one trick ponies, although, in stock form, the Vox is slightly more versatile than the Orange, that seems to have just one sweet spot and nothing more, but I noticed that by replacing the caps it can get much ballsier:

- Replace the 2.2nF input cap with a 10-22nF.

- the 47nF to ground with a 2.2-10nF.

- try a 10-47uF bypass cap and see what you like best.

- use a 10-100nF output cap.

It is louder and consequentelly distorts more, slamming harder the front end of the amp. The tone is more balanced and works better with a "normal" clean-ish tone: the stock circuit is a very trebly treble booster (lol) and works great with a very dark british amp (AC30 normal\EF86 channel, Marshall JTM Normal channel etc...) but it's harsh and ear piercing with a Vox TB channel or a Fender amp. With this mods acts more as a mid\full range boost, keeping the low end tight while boosting, and the 2.2-10nF input cap to ground is more than enough to tame the brittle high end without sacrifying too much gain...I like it a lot!

I decided to try a SFT353 (which IS an OC76) with Hfe=54 and Leak=0.19mA (probably a little weak) and it biases just under 5V at the collector. 5V also with an OC44 (Hfe=88, Leak=0.00mA) and an ASY80YTG (Hfe=62, Leak=0.04mA). 5V with an AC107 (Hfe=68, Leak=0.00mA) by replacing the 470k resistor with a 430k. It seems to bias "naturally" around 5V, and sounds good about there, so, if nobody ever traced and measured an original (if exists) my advice is to try Vc=~5V, Vb=~0.9v, Ve=~0.8v...

If anybody has any additional info is welcome...

Good luck if you decide to build these cool vintage circuits!