ODS - any advice?

[martin manning]

The attenuator would just be a couple of resistors to get 90-95% signal reduction, say 910k and 47-100k to ground.

[Stephen1966]

Super! Thank you.

[Lothy]

Hi Stephen,

Silly question:
Why don't you try to get used to the standard loop? I have tried several reverb and delay pedals and have no issues. Works as a charme for me.
I have good results with a Boss RE-20 followed by a G-Lab Dual Reverb. Even reverb only works perfect (RE out of the chain, it has a adjustable buffer at front, if you think thats the point). When I play without my board, I use a DIY Belton Reverb Pedal, powered by the 12 V relais transformer. I made a 9 V. outlet on the bottom of the chassis for the reverb.

This article helped me to better understand what's going on:
https://online.berklee.edu/takenote/dum ... to-buffer/

What's the point with the "must have" of a Dumbleator?

Cheers
Gerhard

[talbany]

There is something to be said for having some space in your builds especially when constructing turret or eyelet board designs. Henry at Redplate amps used to post all kinds of cool layouts of various ODS designs and cram them in these smaller chassis. I've built several of them including D-Lators. These made for awesome little portable versatile amps however I ended up getting rid of them as I found not one sounded musical to me.They all had something weird going on with the OD section.Like the amp was harmonically congested or confused with not much sustain notes would die right off with very little note bloom regardless of my gain settings.. My theory was it could have been partly due to added noise even though it was not unbearable it was still there and I still think to this day that that little bit of added noise contributed to the harmonic structure of these amps.(Just my theory) This is not to say you cannot build a great sounding amp in a small package it's been done. I've never had any luck with cramming in ODS in a small chassis vs the bigger ones with everything spread out. In total I've built around a dozen or so of these smaller amps including a Musicman..Maybe someone here will have better luck!
I guess my point here is while your adding in other pre-amps be ready for the extra noise you could get and even if the noise may not be that bad or manageable it could still very well contaminate your signal changing the character of the amp's tone and performance slightly.
Anyway This is why I think Dumble put his Loop in a separate enclosure with it'sown isolated power supply and yes the master on the back is a pain in the ass!!
Space The Tonal Frontier
Tony

[Stephen1966]

Gerhard (Lothy) wrote

Why don't you try to get used to the standard loop? I have tried several reverb and delay pedals and have no issues. Works as a charme for me.

And Tony (talbany) wrote

while your adding in other pre-amps be ready for the extra noise you could get and even if the noise may not be that bad or manageable it could still very well contaminate your signal changing the character of the amp's tone and performance slightly.

Hmm... I read the article about buffered loops Gerhard had found, and I've been thinking about the issues of noise that seem probable from adding the FX loop to the chassis and I'm on the fence... Do I really need to reinvent the wheel? There are designs that work, and designs that present issues. I still think Martin's attenuator could go towards solving (if not eradicate it entirely) the problem of the master volume geography but as Marcus found, there is a real host of energetic... er, energies... milling around in that chassis, just waiting for you to make a mistake with a cable to rear their ugly little head and spoil your day. Maybe you're right, Gerhard, but having read the article it only seems to reinforce the idea of why the dumbleator is so cool. And with time based effects, it seems necessary if we aren't going to compromise the tone. If space was going to be an issue with added dumbleator, how much more would it be if we tried to add a reverb tank and so on and so forth...? But Tony (boldly going where no amphead has gone before) really presents a compelling case. I'm also really thinking hard about the combo situation as well. Separating the vibrating speaker cab from the head has the distinct advantage of isolating any microphonic sources of irritation from the sensitive electronics. Clearly, the wisdom here is that we shouldn't be inviting trouble by watering the Tribbles.

[FUCHSAUDIO]

Not sure what the issue(s) are with adding an onboard loop. I remember Grayson Stuckey tried it and failed. I never had many issues. Just making sure the nfb from the power amp or close proximity of the PI wiring to the loop return were safely shielded or routed right. As far as bypass, again, with the same relay precautions you use for an overdrive switch, they should be quiet.

The Two Rock Express clones were unstable because of the power amp phase and the power amp “talking” to the loop. Nobody could figure it out. I realized flipping the phase of the pi and output transformer primary fixed it.

[Stephen1966]

Not sure what the issue(s) are with adding an onboard loop. I remember Grayson Stuckey tried it and failed. I never had many issues. Just making sure the nfb from the power amp or close proximity of the PI wiring to the loop return were safely shielded or routed right. As far as bypass, again, with the same relay precautions you use for an overdrive switch, they should be quiet.

The Two Rock Express clones were unstable because of the power amp phase and the power amp “talking” to the loop. Nobody could figure it out. I realized flipping the phase of the pi and output transformer primary fixed it.

First, thank you Andy. I'm going to look at the layouts and try to visualize them in 3D. It's a start and can't really do justice to the physical under inspection and testing, but it's a start. It's a bit daunting to follow in footsteps as illustrious as yours but you give me confidence: it can be done. Lead dress, shielding and geography. I'm not sure I would have had the insight to realise flipping the phase could be so effective. It does sound like a solution that would transfer into other amp builds that exhibit similar problems though. I'll put a pin in that. This is repertoire building stuff - I owe you a beer.

[Stephen1966]

So, I'm making some progress here. I still haven't decided upon a final configuration but I have decided to go with the 1988 ODS with the Skyliner EQ. It seems to be a popular choice with builders for a reason. Everyone says it sounds awesome. Your comments here have certainly informed my choices and I will never tire of saying it, I really appreciate all your words of wisdom.

Currently, I'm studying the circuit from the 'Dumble Overdrive special Complete Layout 52010.jpg' layout https://ampgarage.com/forum/viewtopic.php?f=5&t=5719 along with the accompanying '#124 Schematic_1988_Skyliner.pdf' schematic .

I'm planning to make all but the relay boards myself, Hoffman Amps do nice relay boards along with all the necessary small parts (thanks for the tip ~Phil) but for the remainder I will make eyelet boards using Martin Manning's most recent layouts https://ampgarage.com/forum/viewtopic.php?f=5&t=29630. Thanks again to Martin for putting so much work into them... and into so much else here.

As I study the circuit and put together my BOM I'm curious about the difference between the Full Wave Doubler and the Full Wave Bridge, relay/LED supplies. Or what the benefits of using the FWB could be. Reading around, I learned that the FWB offers a better regulation performance but a higher diode drop because we have more diodes in series, but that was in relation to transformers and I'm not sure of the application here. I'm not sure either, if the FWB is an experimental prototype or if builders have used it and found any improvements compared to the FWD. The '88 #124 seems to call for a FWD, it doesn't seem feasible that HAD didn't consider a FWB but who knows what he was thinking! Do you think the guy ever reads this stuff!?

[norburybrook]

So, I'm making some progress here. I still haven't decided upon a final configuration but I have decided to go with the 1988 ODS with the Skyliner EQ. It seems to be a popular choice with builders for a reason. Everyone says it sounds awesome. Your comments here have certainly informed my choices and I will never tire of saying it, I really appreciate all your words of wisdom.

Currently, I'm studying the circuit from the 'Dumble Overdrive special Complete Layout 52010.jpg' layout https://ampgarage.com/forum/viewtopic.php?f=5&t=5719 along with the accompanying '#124 Schematic_1988_Skyliner.pdf' schematic .

I'm planning to make all but the relay boards myself, Hoffman Amps do nice relay boards along with all the necessary small parts (thanks for the tip ~Phil) but for the remainder I will make eyelet boards using Martin Manning's most recent layouts https://ampgarage.com/forum/viewtopic.php?f=5&t=29630. Thanks again to Martin for putting so much work into them... and into so much else here.

As I study the circuit and put together my BOM I'm curious about the difference between the Full Wave Doubler and the Full Wave Bridge, relay/LED supplies. Or what the benefits of using the FWB could be. Reading around, I learned that the FWB offers a better regulation performance but a higher diode drop because we have more diodes in series, but that was in relation to transformers and I'm not sure of the application here. I'm not sure either, if the FWB is an experimental prototype or if builders have used it and found any improvements compared to the FWD. The '88 #124 seems to call for a FWD, it doesn't seem feasible that HAD didn't consider a FWB but who knows what he was thinking! Do you think the guy ever reads this stuff!?

the relay board rectification is down to the voltage you need for your relays. If you're using 12v then I think with the transformer used on the original it needs to be doubled. If you were using 5/6v relays it doesn't matter as the regulator will drop it to the required voltage regardless of the the extra voltage input. I tended to use 5/6v relays for this reason before I understood what was going on properly


M

[Lothy]

and the Full Wave Bridge, relay/LED supplies.

As you are from Europe, here is what I use:
I use a 12V DC kit for the relay support. Plus it gives me extra power for a stomp box reverb and an overdrive routed via the footswitch cable. It fits perfectly behind the PT.

https://www.tube-town.net/ttstore/tt-ki ... -12-v.html

Cheers
Gerhard

[norburybrook]

and the Full Wave Bridge, relay/LED supplies.

As you are from Europe, here is what I use:
I use a 12V DC kit for the relay support. Plus it gives me extra power for a stomp box reverb and an overdrive routed via the footswitch cable. It fits perfectly behind the PT.

https://www.tube-town.net/ttstore/tt-ki ... -12-v.html

Cheers
Gerhard

wow, never seen this before, that's a great bit of kit if you don't have an extra secondary on your PT.

Thanks for the heads up

Also good you mention being able to add an extra 9v pedal supply. I've done this and it's very useful. Bear in mind you have to leave the ground floating though or you'll get hum.


M

[martin manning]

I agree, nice compact board. Read the spec sheet to see max current draw vs. chosen output voltage, though.

[norburybrook]

Introduction
Universal kit for an extra power supply which can be used for i.e. channel switching tasks,
relays, optocoupler, LEDs, etc.. Available as 6, 9 or 12 Volt version.
Specification
• Input Voltage: 230 VAC
• Output Voltage: 6 VDC (kit-gl6), 9VDC (kit-gl9) or 12VDC (kit-gl12)
• Maximum Output Current: 333 mA (kit-gl6), 222 mA (kit-gl9), 166 mA (kit-gl12)



M

[didit]

Hello --

That 12V supply would be more than adequate for half dozen relays of the type I prefer. Unclear what the concerns are that you have Martin.

Best .. Ian

[Stephen1966]

Hello --

That 12V supply would be more than adequate for half dozen relays of the type I prefer. Unclear what the concerns are that you have Martin.

Best .. Ian

Hi Ian, what are the type you prefer?

I also found this https://grangeramp.com/product/3-relay- ... d-ver-2-2/