[AVAILABLE] TTSH V4 Build Thread

[KSS]

@sduck
Nice!

I can't tell from the photo if yours does or doeesn't, but you can make these so they transition from round circle at the speaker face to an oval at the panel. Which looks little more like the originals and uses more of the panel holes for potentially better sound. Build with circle on 3DP base and there are no 'overhang' issues.

To be truly effective these need a seal between them and the speaker and moreso with the panel. Auto parts store gasket goops work well.

[sduck]

Yes, when I ramp up my cad skills that might happen.

The speakers i've used in the past have a pretty nice soft rubber seal around the inner edge, so at least there's that. The speakers that came with the current TTSH kit aren't quite so nice - while they have a "seal" sort of gasket, it'll require some assistance to actually work right. I'm not sure I'm going to use them.

And of course there's the bigger question of "how much difference does all this malarkey make? Not much, right?" I don't know, all the ones I've built have had them. There was the one time I visited a local friend who had one that i had built, and while it was on his kitchen counter he started messing with it, getting some great sounds, cranked all the way up through the speakers. After a while we noticed a new sort of buzzing sound that wouldn't go away - ah, the sound of a blown speaker! At least that's an easy fix.

[makers]

I’m going to try something with the speakers used in this project:

viewtopic.php?f=17&t=236602

The built in radiator and speaker box are intriguing but they are 4 Ohm

[fuzzbass]

I’m going to try something with the speakers used in this project:

viewtopic.php?f=17&t=236602

The built in radiator and speaker box are intriguing but they are 4 Ohm

There are some problems with running the on-board amps with 8 ohm loads (Peerless speakers), so 4 ohms may make things worse, but it also may not, depending on how much power these speakers need for drive, and whether their design is effective as a baffle or sealed (or ported) enclosure. What happens with the 8 ohm peerless speakers: when you crank the volume up high, and with low frequency content, the speakers bottom out. This is somewhat a factor of how much power is going in, but another factor in this is that there is no effective baffle or enclosure that would resist/suppress this behavior. When they go to maximum excursion, they rebound (get pulled back to center). When that happens, inductive spikes are generated in the speaker coils. These spikes make their way onto the power rails - affecting other parts of the synth. I have seen these spikes triggering pulses in the electronic clock, and creating sync-like effects for the VCOs.

If you have a pair of these drivers to experiment with, and they otherwise fit, I'm curious how they might work.

[KSS]

Going back to the original PWR AMP design and using even 8ohm speakers is a bad choice. 4 would not improve it. Unless you *also* go back to the very original design and use impedance matchng transformers. The circuit is designed for 45ohm speakers. In the originals this also means less piwer supply current draw,compared to TTSH's which use speakers of lower impedance.

Either way, what fuzzbass is saying about the spikes should be paid attention to!

[makers]

Thanks for the tips. I read the similar posts in earlier build threads. I have really enjoyed working with this synth as a standalone instrument and using the internal speakers. I thought the low-fi quality of the 45 Ohm speakers that came with my kit would be appropriate for the context. But now I'd like to try something else.

I understand the power spikes and will certainly keep an eye out for that. But I was also worried about overheating the built in amplifiers. I planned to install the 4 Ohm speakers as is and gradually ease up the levels, checking the heat on the LM301's.

I have ordered 40 Ohm 20 Watt resistors to try in line with the speakers as well as the HW-711 amp used in the project I linked before. I spent too much time looking for matching transformers and gave up on that solution.

[Jim the Oldbie]

My TTSH build has been on hold for awhile, so I haven't had a chance to actually try this yet, but here's my plan:

I also opted for better speakers, namely these Peerless speakers from Parts Express. (They're very similar to the optional ones described in the BOM except the surrounds are innies instead of outies.) To me, it seems kinda pointless to try driving "normal" speakers like these with the TTSH speaker amps for reasons already discussed, so I intend to mount this little Class D amp board (also from P.E.) in an aluminum box inside the synth case. I'll connect its inputs to the back side of the headphone jack NC switch contacts, using a stereo 1K pot in between for level trim, maybe screwdriver-adjustable from the rear panel. The amp runs on the same voltage as the TTSH, so I'll just need a bigger wall wart for the extra current draw.

With this done, I hope to optimize the original TTSH speaker amp circuits for use simply as a headphone driver; they seem fairly well suited for this actually. I'm hoping all I'll need is a simple voltage divider on each output; something like 33 ohms in series followed by 6.8 ohms to ground, with the output taken from the junction to feed the headphone jack. This should accomplish several things:

1. Provide a reasonable load resistance (39.8 ohms) to the TTSH speaker amp circuits
2. Reduce output voltage (& noise) by about 15 dB to a more suitable range for headphones
(remember that this gain will be restored downstream by the second power amp to drive the speakers)
3. Provide an output impedance to the headphone jack of <6.8 ohms (a bit high these days, but not too bad)
4. The 33 ohm series resistance will provide short-circuit protection for the TTSH speaker amps (for events such as a mono 1/4" plug in the headphone jack).

What do you think, sirs?

[makers]

I installed the Tang Band speakers
http://tb-speaker.com/products/t2-2136sa

They fit well and sound good but the 4 Ohm impedance is almost certainly causing power problems. If I push them too hard I get some pitch tracking problems

Update: I installed this miniature Class D amp to power the speakers. I increased the AC to DC power supply to 3 amps. Now it's rockin!

https://www.parts-express.com/tpa3116d2 ... l--320-699

[FrogStar]

Hi all, Having trouble with the Internal Clock. It does not generate a pulse. The slider is only lit solid on power up if both trim pots are maxed, but eventually goes dark within several minutes if not touched. If raised more that 3/4 it always goes dark. Lit or dark it doesn't pulse. The S&H is working great when tested with an external clock. I've confirmed Cap/diode orientation, and looked at all the resister values in that section. Any idea where I should look next?

[d-pal]

Hi folks, great thread!

I've reached main board stage 2 on ttsh V4 Rev8, and (hope you don't mind a stupid question) don't see any indications on the board (or in the instrucs) as to where the 2 pin amphenols go. There are a few likely spots, but they're umarked for the most part. Is there a diagram or image of the assembled board somewhere?

Thanks!
dp

[d-pal]

ah, think i found them, was thrown by a photo of an older model that used the red connectors in the e.g....anyway, assuming they are the amp L/R, eg gate/trig, and ext cv in?

[KSS]

I've confirmed Cap/diode orientation, and looked at all the resister values in that section. Any idea where I should look next?

Is this purchased kit or self sourced parts?

Which unijunction transistor did you use? 4870? 4871? Something else? And where did it come from? Are its legs matched to the PCB correctly?
Also want to confirm the pins of the transistor or transistors feeding the unijunction.<--ARP used two different designs with one or two transistors here and I don't know which version was used for the TTSHv4.

Kit parts I'd assume will not have these issues, but self-sourced may have different pinouts. The unijumction tranny is getting harder to find and even kit parts 'could' have a problem.