Tonepad Tubescreamer

[The Captain]

Hi- fab site Tonepad, alas the tubescreamer just finished seems to not have enough volume. The only changes I made were 2x 1uf electros instead of the Nps, & 2x 220n polys instead of tants (unable to find either). Any ideas? generally sound is in the right ballpark, just even at max vol its still lower than when switched off.

[tele_guitarist]

what diodes do you have in there? You may be better off using either 1n4001's or connecting two diodes in series for each "side" of the normal clipping diode location.

bw

[petemoore]

yes

I just wrote another debug style page...
First check grounds all from past as many connections as possible.
Check for a shorted power supply, if shorted, fix that before..
Adding power and taking voltage measurements between all the active pins and ground [clip a lead to ground, test pin V's].
That should at least get you started, Aron's is down right now, so post voltages.

[Mark Hammer]

I've made a couple and found that a) the pedal is not a volume monster to begin with, and b) the choice of transistor on the output stage can make a difference in max volume level. Try and pick one with a higher hfe. The Tonepad site indicates usign a 2N3904. This is certainly acceptable, but you may have a little more oomph on the output with a 2N5089 or an MPSA18.

[David Schwab]

Are the polarized caps installed the right way?

I have an old BlueTube pedal which depending on what I plug it into, doesn't have much output because its output impedance is too high, and it's easily loaded down. Plugging it into another pedal fixes that.

Something to look into.

[bubba_b]

Volume issue here, too.

I'm having a volume issue with my TS as well. I've checked and re-checked every component in the circuit and they're all good. Replaced nearly everything with no change. Voltages are all normal. Level and Drive controls work as they should, but the Tone control (using the 20k "W" REV-LOG type) is cutting the volume even more unless it's all the way up. Overall, the pedal sounds good, but it cuts my volume in half or more when engaged and is lacking a bit of high end. Any ideas? Using the following parts:

• 2N3904 transistors
• JRC4558 IC
• .22u TANT caps
• 1u NP caps
• .1u poly caps
• 3 - 1N4003 diodes for asymmetrical clipping

At my wits end trying to figure this out! Here's a few pics if it helps.

[Mark Hammer]

2N3904 are fine units for a lot of purposes, but in this case not so much. You'll likely be more satisfied with MPSA18 or 2N5088/5089. Stock TS9s come with 2SC1815 transistors which tend to be higher hfe than 3904s, though not quite as high as the A18s or 508Xs. Now, just like op-amps, transistor gain is not given by the device itself (the way it is by plunking in a 12AX7 instead of a 12AT7 or AY7), but rather by the passive components and supply voltage surrounding it. That being said, in this context, you can get a little more juice by a mere tranny swap.

You might also consider sticking in a slightly larger value of feedback resistor in the tone stage. Right now, you'll see a 1k resistor there. If you stick in a 2k2 unit, you'll get more output.

Diode swaps is tricky. The sound people want the TS for is a mixture of filtering and clipping parameters that yields a smoother distortion sound. Change the diodes out and, yes, you can achieve a louder sound, but at the cost of clipping. A reasonable compromise is to use 1 silicon and 1 germanium in series in each "direction". This will give only a bit less clipping than stock, with a little more dynamic headroom, and more audible output as a result.

Ultimately, you are best served by reading the "Technology of the Tube Screamer" document over at New Page 1.

[bubba_b]

Thanks, I'll try that. May be awhile, though since I'll have to order parts.