Valvecaster / TDA2030 Combo Problems

[teej]

I worked on this a bit Sunday night but am not getting any output. I'll get pin voltages posted as soon as I'm able.

The heatsink that came with the kit was too tall for the enclosure so I took the heatsink off an old computer GPU.

[teej]

Took voltage readings at the tube pins this morning:

Pin 1 @ 12.30 - 12.40 V
Pin 2 @ 4.8 - 4.9 mV
Pin 3 @ 3.6 - 3.7 mV
Pin 4 @ 4.5 - 4.7 mV
Pin 5 @ 12.74 - 12.78 V
Pin 6 @ 7.13 - 7.15 V
Pin 7 @ Neg. 0.572 - Neg. 0.591 V
Pin 8 @ 3.1 - 3.2 mV

I can't figure out why pin 1 shows 12 volts. Resistor R2 between pin 1 and pin 5 is 220k on the schematic and measured 208k on the DMM.

Also, the tube glows and heats up.

I didn't have the 5" Celeston (4 ohms - it was a new pull from a Trace Elliot cab) that I'll be using for this little combo, so I hooked up the 10" Eminence BP102 driver (also 4 ohms) from my bass cab. I took a video with my cell phone since my digital camera wasn't handy.

Click Below for the Video:

[duck_arse]

THIS is the circuit diagram; that was a layout ....


with power off, you need to test the resistance from the 12V line to pin 1 at the socket. then test the resistances to ground at pins 2, 3 and 4, just for fun and completeness. pin 6 voltage suggests that half is working.

[teej]

with power off, you need to test the resistance from the 12V line to pin 1 at the socket. then test the resistances to ground at pins 2, 3 and 4, just for fun and completeness. pin 6 voltage suggests that half is working.

Below are the resistance measurements between the +12V line at the switch and the socket pins:
Pin 1 = 214 k
Pin 2 = .795 M
Pin 3 = 44.4 k (started at .300 M and fell to 30 k but then climbed, appears steady now)
Pin 4 = 44.3 k (did the same thing as pin 3 but is now steady)
Pin 5 = 0 (as it should be)

[duck_arse]

resistance to ground from pin 3 should be rock-hard 50k max, 0R min.

[teej]

resistance to ground from pin 3 should be rock-hard 50k max, 0R min.

Oh! I was reading from the positive at the power jack, not from the negative (ground).

All pots set to min:
Pin 1 to ground  - Steadily climbs up from around 220 k and levels out around 262 k
Pin 2 to ground - Hovers around 0.912 M
Pin 3 to ground - 48.0 k

[teej]

I cleaned up the ground connections over the weekend and was able to get this working the best it has SO FAR.

- I've got more volume now -- enough that I was worried about waking the neighbors Saturday morning -- but I have to set the volume and gain to MAX. I really feel that just turning the volume up (without using the gain) all the way should get me plenty of volume.

- I'm getting lots of noise, especially when the volume is at MIN. The noise decreases as soon as I turn the volume up a little. If I turn the gain up, the noise comes back of course.

- Most dissatisfying is, once again, the last of crunchy, distorted goodness that I heard in pretty much every Valvecaster video on YouTube. I don't know if it's because the amp isn't putting out enough or what, but I've started building a Trotsky drive just in case. I'm playing around with the idea of installing it inside along with the Valvecaster and having a switch to toggle it between off, 1/2 drive and full drive.

I took two demo video clips but still need to upload those.

EDIT: I found a 12 V, 1.25 A switching power supply today at work. I wonder how that might affect the performance of this setup?

[teej]

Here's a video of what it's currently doing. The VC is such a commonly built circuit and the little TDA2030 amp appears simple enough. Maybe it's my experience, but I can't figure out why this isn't working like it should (or like I think it should ).



UPDATE: Here's another vid that I took after the first one. The camera is right next to the speaker so I hope it picks up what the amp is doing (or not doing).

[duck_arse]

videos? they are a bit beyond my reach here.

the switching supply may introduce some switching-hash as noise to your circuit. now know this, it won't be such a problem if it happens. if you look the valvecaster thread, all one million pages, you'll probably find methods of more gain getting from the second stage. do you get more volume with the tone control disconnected?

[teej]

videos? they are a bit beyond my reach here.

the switching supply may introduce some switching-hash as noise to your circuit. now know this, it won't be such a problem if it happens. if you look the valvecaster thread, all one million pages, you'll probably find methods of more gain getting from the second stage. do you get more volume with the tone control disconnected?

Meaning with the tone pot bypassed (C4 straight to ground)? I haven't tried that yet, but with the tone at MAX or MIN, it doesn't sound like it affects the volume any.

[teej]

Before work this morning, I mostly worked on a Trotsky drive tomake up for the NoiseBox's (that's a TDA2030 amp with a Valvecaster pre for those who are just tuning in) current lack of metal. However, I did test out that switching power supply mentioned in a previous post.

WOW! What a difference! If it weren't for the subtle pop when I flipped the switch and the LED lighting up, I wouldn't have known the amp was on. This amp is now silent except for the expected "buzz" when plugging in an instrument. For this morning's test purposes, I used my P-bass and not my wife's Strat. Perhaps the different pickups are the reason for the lack of hum/buzz now. I wasn't able to turn the volume up much since my lovely lady was still asleep (it was 6:30 AM on her off day).

[teej]

UPDATE: Even the Strat and it's single-coil pickups is silent. There is still, however, no crunchy distorted fuzzy metally goodness coming out.

This is what I'm aiming for: http://www.youtube.com/watch?v=3cMqYlhSQ8c

[alpine]

12AU7 is the lowest gain of the trio, have you tried with a 12AT7 or 12AX7 (12AX7 is the highest gain)?

[teej]

12AU7 is the lowest gain of the trio, have you tried with a 12AT7 or 12AX7 (12AX7 is the highest gain)?

I haven't but if it will get me what I'm hearing in the videos I've seen, I might give it a try.

Over the weekend, I tested the Trotsky I put together but I don't think it's working right either. I got slight fuzz/distortion but again it wasn't what I heard in the videos. I'm wondering if it's the driver. Perhaps it's too small? Or perhaps the TDA2030 isn't outputting enough?

[duck_arse]

it might be an idea to disconnect the valvecaster temporarily, and drive the tda2030 thing with something else, just to see if the amp will provide what you are wanting. what do you have pedalwise you might use as drive? and maybe do the same with the valvecaster, run that into a guitar amp, see what drive it will provide.

[edit :] C4 on the amplifier circuit baffles me. does it really connect the input signal to the 22k divider string? what happens if you lift this cap?

[teej]

it might be an idea to disconnect the valvecaster temporarily, and drive the tda2030 thing with something else, just to see if the amp will provide what you are wanting. what do you have pedalwise you might use as drive? and maybe do the same with the valvecaster, run that into a guitar amp, see what drive it will provide.

[edit :] C4 on the amplifier circuit baffles me. does it really connect the input signal to the 22k divider string? what happens if you lift this cap?

Pedal-wise, I have none. I used to have a Korg Pandora PX2 and PX4-B but sold those long ago. Amp-wise, I only have my Hartke 1400 (bass amp).

[teej]

I ordered a handful (5 to be exact - they were sold as a set) of MPF102s off eBay. They arrived yesterday. I took the buffer section from the Noisy Cricket schematic and put it between the Valvecaster's output and the input of the TDA2030 amp. I meant to take a photo but I didn't, so this crudely Photoshopped image will have to do.

I tapped the drain into the 12 volts going to pin 5 of the tube. For ground, I connected the resistors to pin 4. The output from the volume pot goes to the input of the buffer and then out from the buffer to the TDA2030.

I haven't had a chance to test it yet. That will come later tonight after work.

[duck_arse]

C4, C4, C4. did I mention C4? have you tried lifting that yet? have you? yet? C4?

[teej]

C4, C4, C4. did I mention C4? have you tried lifting that yet? have you? yet? C4?

Ah, no I haven't. I'll do that tonight during my testing and post the results on Monday.

[teej]

C4, C4, C4. did I mention C4? have you tried lifting that yet? have you? yet? C4?

It generated a tone once the volume or gain (I don't remember which) were increased beyond a certain point and that tone changed as I turned the tone knob. Basically, the results weren't pretty.