Air-Brake in an ODS

[RJ Guitars]

Hello Forum,

I've put a tweak of a different sort on my ODS... I built in an Air-Brake style attenuator. It works really well at knocking down the volume and also has made an improvement in the tone.

I tried my stand alone Air-Brake with the amp recently and was surprised that it did such good things for the tone. Following that discovery I decided just to build one in when I had the cabinet apart to change out the speaker.

I made it so that I can switch it in or out very easily... I am quite pleased with this result. Even now the amp starts getting pretty loud with the master on "3" ...and yes, this amp goes to "11".

rj

[Bob-I]

I'm surprised. The Dumble tone I've always read, was based on clean power amp and overdriven pre. Live and learn.

How's the Tonker lite? especally the bottom end? The specs make it look like it might be lacking a bit on the lows.

EDIT: Nevermind, I read the speakers thread.

[RJ Guitars]

I'm surprised. The Dumble tone I've always read, was based on clean power amp and overdriven pre. Live and learn.

Bob, Even with the attenuator on there I may not be driving the power amp into clipping. I just don't have anywhere to play where I need that kind of volume. So what the attenuator does for me is gets the tubes working a little bit, but still not pushing them. My resistors haven't even gotten hot yet. I'm getting really loud in my world when I have the master on three and the attenuator on... so I think I'm moving the power tubes to some place just above the point they start doing some labor.

Having said that, I think the OPT match changes with the attenuator and that may contribute to the tone as well. After messing with it last night I think the amp is brighter with no Air-Brake so there are probably several things happening.

Tonkerlite= mid-rangey and early breakup... https://tubeamparchive.com/viewtopic.php?t=4600

rj

[Stanz]

Has anybody put power scaling into a clone?

[Bob-I]

Bob, Even with the attenuator on there I may not be driving the power amp into clipping. I just don't have anywhere to play where I need that kind of volume. So what the attenuator does for me is gets the tubes working a little bit, but still not pushing them. My resistors haven't even gotten hot yet. I'm getting really loud in my world when I have the master on three and the attenuator on... so I think I'm moving the power tubes to some place just above the point they start doing some labor.

Having said that, I think the OPT match changes with the attenuator and that may contribute to the tone as well. After messing with it last night I think the amp is brighter with no Air-Brake so there are probably several things happening.

Tonkerlite= mid-rangey and early breakup... https://tubeamparchive.com/viewtopic.php?t=4600

rj

Hmmm... I'll have to give that a try. I have an airbrake and I also don't play loud at home. I have trouble getting the settings at low volumes so I understand what you're getting at.

[Tonegeek]

If I understand correctly the Airbrake removes some highs when it is in circuit. I need something to do the opposite. I get pretty good tone from my clone at bedroom volume with the exception that the highs are attenuated. I find myself cranking the presence to compensate, but there has got to be a better way. Ideally a bleeder on the master or someother pots should help, but it sounds like a bright switch when I have tried it and it still affects the highs at higher volumes (unless the pot is all the way up). I am sure others have this same issue but has anyone come up with a good solution? Sorry, I don't mean to get off topic.

[llemtt]

Has anybody put power scaling into a clone?

yes

all my ODSs are power scaled

teo

[groovtubin]

If I understand correctly the Airbrake removes some highs when it is in circuit. I need something to do the opposite. I get pretty good tone from my clone at bedroom volume with the exception that the highs are attenuated. I find myself cranking the presence to compensate, but there has got to be a better way. Ideally a bleeder on the master or someother pots should help, but it sounds like a bright switch when I have tried it and it still affects the highs at higher volumes (unless the pot is all the way up). I am sure others have this same issue but has anyone come up with a good solution? Sorry, I don't mean to get off topic.

Maybe try putting a higher value cap on the 470K in OD entrance..MUCH better than bright caps else where imho, i HATE bright caps on master`s!! Kinda like EJ`s tone , clear but warm as all get out..

[Tonegeek]

If I understand correctly the Airbrake removes some highs when it is in circuit. I need something to do the opposite. I get pretty good tone from my clone at bedroom volume with the exception that the highs are attenuated. I find myself cranking the presence to compensate, but there has got to be a better way. Ideally a bleeder on the master or someother pots should help, but it sounds like a bright switch when I have tried it and it still affects the highs at higher volumes (unless the pot is all the way up). I am sure others have this same issue but has anyone come up with a good solution? Sorry, I don't mean to get off topic.

Maybe try putting a higher value cap on the 470K in OD entrance..MUCH better than bright caps else where imho, i HATE bright caps on master`s!! Kinda like EJ`s tone , clear but warm as all get out..

Jim,
I could do that but then it would be too much when cranked. I need it to vary with the volume - typically that is done with caps from wiper to output on a pot but I agree with you that I don't like it. I am not quite sure what causes this effect but I have heard it using other amps too. I am thinking that when you turn down a volume control that it lowers the knee of the low pass filtering going on in the circuit due to Miller capacitance resulting in less highs. Or it could be the uneven response of the human ear to certain frequencies at different volumes -hence the "Midnight" control on your home stereo which basically scoops the mids at low volume. It may be that my speakers are part of the problem. I am using 2- 30 watt speakers and they may just be adding some nastiness to the high end when cranked. Fortunately most of my playing is done at higher volumes for which my amp is tweaked adequately.

[JimiB]

so what resistors are those? mouser part #?
Do they come with the aluminum tabs on the end or did you do that?

[RJ Guitars]

so what resistors are those? mouser part #?
Do they come with the aluminum tabs on the end or did you do that?

JimiB - I got those big resistors at a salvage place, so I don't even know if they are still in production... but here is a picture if that helps...

If you look at that thread on the DIY air-brake (TrainWreck Discussion) I think they provide a mouser part number for a similar resistor. Probably any wire-wound high current inductive resistor would serve for this job.

rj

[Luthierwnc]

RJ;

When I lived in Santa Fe there used to be a used electronic component shop in Albuquerque. I don't know if it is still there or if you are ever north. They had bins of big resistors pulled from obsolete equipment. I got a few as my dummy loads. The Black Hole in Los Alamos had a bunch of stuff from the lab. Be prepared to haggle if they are still in business.

Skip

[greiswig]

RJ;

When I lived in Santa Fe there used to be a used electronic component shop in Albuquerque. I don't know if it is still there or if you are ever north. They had bins of big resistors pulled from obsolete equipment. I got a few as my dummy loads. The Black Hole in Los Alamos had a bunch of stuff from the lab. Be prepared to haggle if they are still in business.

Skip

Wasn't that Ed Grothus' store? Heck, I bought a 15kV DC power supply from him to build my first laser when I was a kid living in Lost Almost. He's a character...still alive?

I wonder what kind of amp HAD would have come up with if he got his parts from the Zia Salvage yard or from Grothus.

[RJ Guitars]

Funny thing to get these last two posts - I just got back from a run up to the Black Hole - Ed Grothus' salvage yard... wow what a collection of stuff!

Yes Ed is still alive, 85 years old, deaf as a rock and an avid activist of anything that goes against the grain... and yes he wants too much for everything! But he has got one of everything too.

He's got: tubes, NOS tube sockets, caps, chassis, transformers, and big bins of resistors. I got all my airbrake parts there. The worst part is that you have to sort through a mountain of junk... but it's also kinda cool to get lots of retro stuff.

rj

[Luthierwnc]

Another thing to be prepared for in that store is the cold.

For the uninitiated, the Black Hole is a leaky, unheated old supermarket full of yesterday's technology from the Los Alamos weapons lab. A friend once said it would be the ideal supply store if "Dr. Wierdo" was setting up a new shop. There are racks upon racks of test equipment, parts, hoses, incubators, you-name-it going back to the '50's -- all the very best quality your money could buy. Of course for obsolete tech guys like us, there are all sorts of gizmo's that never existed anywhere else.

If you can get his attention, Ed could give you the history of most things in the store but he seems very proud of them. You can get the price down if you play a little stupid. Be sure to use cash and put it in several pockets so you can slowly count the contents of one cache and come up short. sh