TRAVIS RITE AMPLIFIER

[TIMBO]

Hi guys, Another local builder from the late 60's early 70's

An interesting circuit that I can't say I've seen this phase inverter used too many times.

I have redrawn from a tracing that was done 1973, so again I can only believe that it is correct to the original circuit.

http://www.ozvalveamps.org/rite.htm
The band https://en.wikipedia.org/wiki/Travis_Wellington_Hedge

[kagliostro]

Ciao TIMBO

Strange Phase Inverter (or, at least, it is strange to me)

it remember a Floating Parahase, but isn't exactly the same



Franco

[PRR]

It is a floating paraphase, but wired different so the negative bias on the output tubes does not upset the driver tube.

Otherwise simple copy-cat of Fender.

http://www.r-type.org/articles/art-097.htm

[purpletele]

It is a floating paraphase, but wired different so the negative bias on the output tubes does not upset the driver tube.

Otherwise simple copy-cat of Fender.

http://www.r-type.org/articles/art-097.htm

That was an impressive response with great documentation!!!

[TIMBO]

Thanks guys, Is there a particular fender model that it is similar to.

[sluckey]

All of the 5B? and 5C? models (except Champ) use a common paraphase inverter. I don't think any use the floating paraphase inverter though.

[PRR]

> a particular fender

"All"?

Bitsa this and bitsa that?

It is not a copy of any particular model. But somebody knew a lot of Fenders and did it similar. The Floating Paraphase bit maybe came out of the latest issue of whatever electronics magazine was popular.

[TIMBO]

Thanks PRR, Comparing to the ones sluckey mention the 5D5/8 looks close.
The preamp looks to be drawn wrong but looks like its also a standard fender TMB/volume.

[TIMBO]

Hi guys, Some progress on this one.

With the PT and OT I have a modified circuit was needed.

Voltages look good and close to the original amp.




There is a low hum and I'm thinking it's because the OT is close to the input stage. I'll try a metal shield around the OT.

The OT and PT came from the "type 3 amplifier"


http://www.oneillassociates.com.au/~poneill/Centre_Industries_Amp.shtml
The amp is putting out a low volume and I'm not sure why.

[terminalgs]

Hi guys, Some progress on this one.

On that schematic you drew: the union of two 1M R's between plates of V2a and V2b is what feeds signal to V2b grid.  won't this be 0vac signal? with two 1M's?  would it need to be 920K/1M or 800K/1M  to feed V2b a signal of approximate amplitude of the input signal of V2a?

[PRR]

> would it need to be 920K/1M

Since we aim for unity inverting, with tube gain around 50, there's around a 2% error. As you say, fiddling the resistor ratio can "improve" this. However the math is very tedious (even with PC help), the improvement is small, and maybe not pure improvement for a guitar amp.

Build it and throw 10Meg-22Meg across one of the 1Meg and see if you like it better. I suspect it is not worth the bother.

[pompeiisneaks]

I've been seeing a lot more of this from photobucket and it sucks:

~Phil

[TIMBO]

Hey Phil, I would think I would have over a 1000 photo's that I have posted, all gone 

[pompeiisneaks]

I think you could get them out, but you can't link them externally like that, so maybe see if you can download them, and upload to some other thing that's not crappy :P  imgur, google photos etc.

~Phil

[PRR]

Yes, the owner can download the entire PhotoBelch collection and re-link them elsewhere. That's a pain in two steps (re-uploading elsewhere, and finding all your posts and auctions and editing the links.)

I am told that strangers "can" grab the URL, open a new browser, open just the image link, and see it. You have to let PB think you are "not" finding the image *through* an external site, but on its own. However PB has always been awkward for me, and I'd almost never hoop-jump like that.

[DummyLoad]

I've been seeing a lot more of this from photobucket and it sucks:

~Phil

yeah, they think they're dropbox. a good friend was one of the photobucket founders. sad to see what he built go down the trash chute.


personally, i now have a dropbox subscription. not that they're the best by any stretch, it's just convenient because a couple of our hardware vendors use them as well.


--pete 

[TIMBO]

Hi guys, Investigating the low output.
The little I know about the Oscope, with a 1v input @ 1k and the volume at max the waveform at throughout the circuit is clean all the way, with no clipping.

[shooter]

with a 1v input

I would think 1V would clip at the 1st gain stage.  I typically use ~100-200mV

what are your signal readings for each stage?  Vin, Vout

[TIMBO]

Hey shooter, Found the low output problem 

I recycled some new pots that I had used in some other builds and seems that one of the solder tags may have broken inside the housing.
It would pass signal but at a reduced amount, touching the tag with a chopstick would increase volume.

When I get some new pots i'll post the new voltages.

It had a low hum, that is now gone.

[DummyLoad]

Hey shooter, Found the low output problem 

  


nice work btw,


--pete

[shooter]

I recycled some new pots

I had a very similar problem on my hybrid, used pot, broke solder post.  glad you're moving fwd

[TIMBO]

Hi guys, New parts ordered and some more info on the original schematic has got this one sounding awesome.
Updated schematic

Voltages

The PI voltages are a little lower than the original by about 20v but I doubt that it will make much difference to the overall sound.

[TIMBO]

A few pics....