Red Iron T-Rex

fusionbear · Post by **fusionbear** » Mon Mar 30, 2015 4:49 am

Hello gents!

Any of you familiar with the Red Iron T-Rex? It is very TW Express like but with octal tubes and a "James" tone stack. I really like this amp! I have looked under the hood, but am hesitant to post any pics out of respect for the builder. The amp is easy to play , but never falls apart even when maxed out. It is also Cathode biased. This one has a Tone Stack bypass mod as well as a cross line MV which actually works quite well...

Here it is:

[IMG

768]http://i169.photobucket.com/albums/u223/fusionbear/IMG_0048_zpsilnibmgd.jpg[/img]

[IMG

768]http://i169.photobucket.com/albums/u223/fusionbear/IMG_0024_zpskc0j0iyi.jpg[/img]

Clip:

https://www.youtube.com/watch?v=DmI-sND ... ilU6OaRURA

M Fowler · Post by **M Fowler** » Mon Mar 30, 2015 5:37 am

Each one is a little differently built from what I've seen but PTP wired.

I have gut shots of 3 different amps.

WRC34 · Post by **WRC34** » Tue Mar 31, 2015 3:41 pm

Beautiful looking amp!

I listened to the sound clip/YouTube vid. Wow you weren't kidding, it really stays tight all the way through the volume spectrum. Seems like there's some kind of voodoo at work to get this level of performance out of a cathode biased amp. Any hints at what they've done w/the circuit to achieve this...without creating any enemies @ Red Iron? A cathode biased 6CA7 TW or is there more/less to it?

fusionbear · Post by **fusionbear** » Wed Apr 01, 2015 1:00 pm

The power supply is very robust with a total of 6 B+ drops. And yet, the amp is really easy to play. The design is brilliant IMO...

The B+ goes first to a huge choke first and then continues to the usual B+/Cap set up.

Blackburn · Post by **Blackburn** » Thu Apr 02, 2015 9:18 pm

fusionbear wrote:The power supply is very robust with a total of 6 B+ drops. And yet, the amp is really easy to play. The design is brilliant IMO...

The B+ goes first to a huge choke first and then continues to the usual B+/Cap set up.

Do you mean to say that the amp uses a choke input as it's initial filter, rather than an electrolytic cap? Very interesting, if that's the case.

That clip is very good btw. I listened a couple times and really dig it.

shane · Post by **shane** » Thu Apr 02, 2015 10:13 pm

Anyone looked at the schematic of an Allessandro Redbone? might ring a few bells here

Cheers
Shane

M Fowler · Post by **M Fowler** » Fri Apr 03, 2015 2:07 am

Here are some gut shots.

fusionbear · Post by **fusionbear** » Fri Apr 03, 2015 5:51 am

Blackburn wrote:
fusionbear wrote:The power supply is very robust with a total of 6 B+ drops. And yet, the amp is really easy to play. The design is brilliant IMO...

The B+ goes first to a huge choke first and then continues to the usual B+/Cap set up.
Do you mean to say that the amp uses a choke input as it's initial filter, rather than an electrolytic cap? Very interesting, if that's the case.

That clip is very good btw. I listened a couple times and really dig it.

Yes, you are correct. A big giant, sealed Choke, then to the OT primary.

WRC34 · Post by **WRC34** » Fri Apr 03, 2015 9:51 am

Choke input filter - bingo, that's the voodoo* I was looking for

This is cool because it drops much more voltage from the PT's HV secondary than a cap input filter, and as such I'd imagine would allow the builder to use a bigger, more powerful PT with a high mA rating on its HV secondary without having too high B+ or running into a large expense of having custom transformers wound.

*voodoo = something not commonly found/used in guitar amp designs and therefore the knowledge and opinions of the characteristics of its implementation are limited, murky, mysterious, unknown...chicken bones!

shane · Post by **shane** » Fri Apr 03, 2015 10:55 am

Doesn't necessarily have to be a choke input filter. could be a Pi filter like the Allesandro.

Masco · Post by **Masco** » Fri Apr 03, 2015 1:45 pm

What's the metal can at left w/ cap mounted on top?

fusionbear · Post by **fusionbear** » Fri Apr 03, 2015 3:13 pm

Masco wrote:What's the metal can at left w/ cap mounted on top?

It is CDE 1Mfd Cap. The part number seemed to have been scratched off. It measured 1Mfd.

fusionbear · Post by **fusionbear** » Fri Apr 03, 2015 3:15 pm

shane wrote:Doesn't necessarily have to be a choke input filter. could be a Pi filter like the Allesandro.

One big difference is that the Allesandro's that have been on my bench fall apart as you crank them. They get too squishy and have ghosting that I don't care for.

WRC34 · Post by **WRC34** » Fri Apr 03, 2015 5:21 pm

I think the only catch w/a choke input filter is that the choke has to be rated to handle the full current pulled throughout the entire amp, whereas w/cap input filter circuits that have a choke feeding the screens the mA rating of the choke can be almost anything to taste. Am I thinking about this/seeing this correctly?

Tube Amp Archive

Red Iron T-Rex

Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex

Re: Red Iron T-Rex