Turtlerock Forum

by **anguswoodhead** » Fri Sep 25, 2009 2:55 pm

Greetings Turtlerockers.
Just thought I would share my joy.
Rob has just finished racking a Trimax A55 Line Amp for me.
I bought it off Myles a while back.
Very keen to see how she will sound.
Ruler flat from 100Hz to 10KHz and extends up to around 30 or 40 before dropping off sharply.
Should be nice and open / extended.
Looks like he found me a nice vintage vu meter too. :D
(Photos by Pro Harmonic)

by **mylesgm** » Fri Sep 25, 2009 3:06 pm

Hey that's pretty sweet! So update us on how it sounds...
M

by **Kurt** » Fri Sep 25, 2009 3:27 pm

Excuse my ignorance, but what exactly is a line amp for? If a signal is at "line level", why does it need to be amplified? (apart from by a poweramp to drive speakers?)

by **Gian** » Fri Sep 25, 2009 4:28 pm

Kurt wrote:Excuse my ignorance, but what exactly is a line amp for? If a signal is at "line level", why does it need to be amplified? (apart from by a poweramp to drive speakers?)

I've wondered the same thing.

Hey Angus, do you have a schematic for the circuit of the A55. I have had a bit of a search in google and cant find it.

by **Gian** » Fri Sep 25, 2009 4:30 pm

Rob, if you are there, what do you use to screen print on the front panels?

by **rob** » Fri Sep 25, 2009 6:59 pm

like many "univeral amps" from the early broadcast era these were designed for a max of around 50dB of gain. Some of the similar RCAs ran at 70+dB. They could thus be used as line amps, makeup amps or mic preamps. The required gain was set by the use of pads. Whilst this is not the best way to achieve optimal signal to noise ratios, for AM radio broadcast it was fine. These Trimaxs had the adjustable pad network after the input transformer and before the fixed tube amp stage. Reincarnated in these units the gain control has been brought to the front panel ( originally it was set with screwdriver ajusts on the rear of the unit ) and an output attenuator added for fine gain trim and taking advantage of the max +32dBu output level that these units can give.

I have the schematic...can't recall where it came from! These units had all been modified .. badly and were restored to the original bar one change that made sense. The power supply requirements were demanding using a -24V and +130V supplies plus +48V for the phantom and DI module.
They also have an unusual tube set of 2 x 6AU6 and 2 x 6AM6

The artwork is laser engraved to the black anodised panel

by **anguswoodhead** » Fri Sep 25, 2009 10:58 pm

Schematic, Specs and what it looked like before Rob worked his magic.

by **heathen** » Sat Sep 26, 2009 7:04 am

Top job there, seems almost a total rebuild. Looks like it's totally busted in the before pics. Is there anything Rob casn't fix. :)

Ahhh just waiting for my pair of telefunken pre's Rob racked last week for me, I really like the laser etching too, real pro. Very keen to give them a test run.

by **anguswoodhead** » Sat Sep 26, 2009 7:08 am

Looks cool Heathen.
My next project with Rob is a 4 Ch Neve Mic Pre using vintage BA183 Amp cards and new Carnhill trannies. :D

by **heathen** » Sat Sep 26, 2009 8:22 am

anguswoodhead wrote:Looks cool Heathen.
My next project with Rob is a 4 Ch Neve Mic Pre using vintage BA183 Amp cards and new Carnhill trannies. :D

Nice!

by **Kurt** » Mon Sep 28, 2009 1:19 am

Looks like Gian and I will never know the mystical purpose of the line-amp.
At least if we don't know what it's for we won't need to spend money on buying/building/fixing them!

by **anguswoodhead** » Mon Sep 28, 2009 7:01 am

The V72 and Trimax Line Amps that I own have been converted by Rob into Mic Pre's.
They now have 48v phantom, DI input etc.

A line amp can be a reverb return or Aux send - the signal gets amplified but not to the same extent as a mic pre.
I am no tech - someone else should be able to explain it better.

by **SteveL** » Mon Sep 28, 2009 8:32 am

Kurt wrote:Looks like Gian and I will never know the mystical purpose of the line-amp.

Like the continuum transfunctioner, they are very mysterious and powerful devices whose mystery is exceeded only by their power........

by **rob** » Mon Sep 28, 2009 8:39 am

umm... I thought i explained the "line amp" concept pretty well

lets try again: like many "univeral amps" from the early broadcast era these were designed for a max of around 50dB of gain. Some of the similar RCAs ran at 70+dB. They could thus be used as line amps, makeup amps or mic preamps. The required gain was set by the use of pads. Whilst this is not the best way to achieve optimal signal to noise ratios, for AM radio broadcast it was fine

consider that we are dealing here with an example of one of these "universal amps" ( my term ) and can equate to the "line amp" concept ( your term )

by **Kurt** » Mon Sep 28, 2009 9:08 am

Haha, sorry Rob, missed your post!

So it's basically a generic pre, without phantom power, which can be added by clever people like you.

by **anguswoodhead** » Mon Sep 28, 2009 2:22 pm

I must say this for Rob - he knows how to pack an item so it doesn't get damaged in transit.
Also he always answers his phone and returns e-mails mostly same day.
Unlike some other Aussie manufacturers. :x

by **rob** » Mon Sep 28, 2009 4:20 pm

thanks Angus...not sure about the packing items bit...I've had a couple of units damaged in transit

although i'm learing all the ways that couriers find to trash a carton and where the weak links are!

by **Gian** » Mon Sep 28, 2009 4:53 pm

hey Rob,

What are the turns ratio on the input and output transformer in this unit? and/or what would work well?

thanks

by **rob** » Mon Sep 28, 2009 5:08 pm

dunno...lifes too short to puzzle this sort of stuff out...I just concentrated on making them work as designed.

by **mylesgm** » Mon Sep 28, 2009 5:38 pm

As regards the transformers, I can't remember off hand but its written on the tx's so Angus could have a look or if its important I can look when I get the others I have...
Myles

Turtlerock Forum

Some more Rob Squire Magic - Trimax A55

Some more Rob Squire Magic - Trimax A55

Who is online