?ABC? Trimax Mic-Pres

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?ABC? Trimax Mic-Pres

Postby toby_72 » Mon Jun 27, 2005 2:38 pm

Hi There!
I was wondering if anyone could shed any light on some mic-pres that have been offered to me recently:-

They were apparently made for ABC (Australian Broadcasting Corp, I presume) - with I/O transformers from Trimax.

They've been described as 'warm and fat sounding' - but I hear that description so often with mic-pres and I've come to the conclusion that it means different things to different people imo - Soo...anyway - I wondered if anyone had used these mic-pres before- love to hear opinions.
How do they sound (in comparison to other better-known mic-pres eg V72/77/78, V76, Neve 1272/1073, API, etc.)?
What mics did you use them with? Condensers - solid state, valve?, Ribbon? (not sure if there's enough gain for ribbons actually) etc.
Recording what material? vocals, bass, guitars (acoustic, ampd?), drums etc.

Any and all info much appreciated. thanks.
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Postby Linear » Mon Jun 27, 2005 3:39 pm

HI,

Here's what limited information I know.

These were made for the ABC by various companies (Transmission Products, Ericsson-Trimax) for their broadcast division, similar to German Radio with the V-series tube gear.

Type 1 amplifiers are fixed 40dB gain amps, while Type 2 amps were adjustable 6.5dB line amps. Type 3 were distribution amplifiers and Type 4 were limiting amps.

The Type 1 amps can be easily modified with a pot to adjust gain. I've seen two types of enclosures too, one has a shell that hinges up for easy access, the other doesn't. Out of the two I mentioned, the Ericsson/Trimax cassette is good, the Transmission Products is not.

If you can get a rack with a power supply it is very worthwhile, in fact 3 amps + power supply in rack would be worth 6 type 1 cassettes without (IMHO).

I also have a V72, and they are quite similar. I wouldn't describe the sound as 'phat' but it is flattering as most good tube stuff is. I don't believe they came with phantom, so you would need to add that. you can get schematics for them here

http://www.retrovox.com.au

Cheers

Chris
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Postby toby_72 » Mon Jun 27, 2005 11:25 pm

Ah thankyou Chris - most helpful.

Yes the config that was offered to me was 2 x mic-pre (type 1) and 1 x line (type 2) + psu
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Tue Feb 14, 2012 11:54 pm

Hi guys.

Chris, hoping you can share some more thoughts on why you say the Transmission Products versions were no good?
- Are they just made from poorer quality components, bad design, or other..?

I have a couple of these on the way to me now, that came together with the T.P manufactured power supply module, as I am trying to put together a rack load for these, including one Trimax module that I have here, also.

I'd be keen to hear any experiences of the Transmission Products version, as I will have a couple of them, and wonder if it's worth putting a bit of effort into them, if they need any attention. And would the power supply be just as sufficient as the Trimax manufactured module?

Here's what I have, besides one (modified) Trimax TYPE "1A" module..
Image
Image
Image
Image

Thanks!
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Re: ?ABC? Trimax Mic-Pres

Postby Chris H » Wed Feb 15, 2012 2:22 pm

It might be worth considering not doing any mods to em. I have just been reading some opinions about fixed gain valve preamps by an experienced engineers on another forum.Here is a teaser :

Having a fixed gain usually means that the amp is working in it's ideal gain-range, although this is sometimes flexible

Higher gain almost always means lower global feedback, and in my experience this means better sound.

The less negative feedback, though, the more that the real sound of the amp comes out. For this reason good amps with low feedback are quite expensive to build.

The rest of the thread is here:

http://prorecordingworkshop.lefora.com/ ... =12#post12

I also think there is some merit in getting the phantom power from another source other than the mic pre if it isn't built in. An external phantom power supply can be very handy. All the Optro pre's I have don't have phantom and I use two custom built power supplies patched in between the pre and the mic. Each supply can power 4 mics so together with the valve mics with their own power supplies this is usually all I need.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Thu Feb 16, 2012 10:37 pm

Thanks for that information, Chris.
I was wondering about building (or sourcing) a separate phantom power supply to use with these old pre-amps.
I have a few old broadcast pre's, all lacking phantom power - so it'd be worth having a universal 48v supply to use inline with any of them, rather than trying to have it incorporated into each and every one.
If you'd post a pic of your units, I'd be curious to see them.

I can't get that link to work for me, for some reason.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Fri Feb 24, 2012 6:40 pm

Oh, yeah, I got to that link now - interesting reading!
I'm working away on these, and more-so on some other older AWA pre-amps the last week, with a friend.

Looking forward to trying them out - it had occurred to me that they may be especially good on drums.
Cool.
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Fri Feb 24, 2012 11:01 pm

I have had one of these old ABC racks under the bench for years and this thread has enthused me to see what was in it.

It is the original rack with:

One Power Converterr (Power Supply ?) Transmission Products 50mA

One Power Converter, (also a Power Supply ?) Ericson/Trimax 60mA

One Amplifier Type 1 Trimax

One Amplifier Type 1 Transmission Products

The rack has input/ouput conectors on the rear for three amplifiers, 50 ohm and 600 ohm inputs and a 600 ohm output for each one, I'm not sure what the connectors are, they could be just 'banana plugs'. It has a standard three pin mains plug.

I had a look at the Retrovox link, but I couldn't see the schematic for the Type 1 Amplifier.

Now I have to decide what to do with it now, decisions, decisions.
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Sat Feb 25, 2012 8:15 pm

Further to the above, I read that the racks were originally intended to house three amplifiers and a power supply. So, I probably have a spare power supply. I would ideally like two Trimax Type 1 amplifiers so I would be interested in swapping the Transmission Products Power Converter and the Transmission Products Type 1 Amplifier for a Trimax Type 1 Amplifier. Anyone interested? At this time none of the amplifiers or power converters have been powered up, so they are "As Is".

Also, does the Power Converter have to go in a particular location in the rack?
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Sun Feb 26, 2012 1:13 am

I don't think it matters where the power converter goes, but somewhere in the literature I have I'm pretty sure it says the PSU module would normally go in the right hand side. Don't know why.

It'd be great to see some images of the rack unit you have there, and how the connectors work!

Cheers,
Evan.
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Sun Feb 26, 2012 12:13 pm

I'll take some photos this week and post them here.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Sun Feb 26, 2012 12:18 pm

Great!

If anyone has one of these rack units for sale, I'm keen!
I have some modules, but slotting them into the rack would be much easier than mounting and wiring up my own custom build.

Cheers!
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Re: ?ABC? Trimax Mic-Pres

Postby Barney Loveland » Sun Feb 26, 2012 2:41 pm

I have one of the racks i'll probably not end up using. It already has pig tails on one of the slots. Let me think about it.

Has anyone compared the Trimax/Ericsson side by side to the Transmission Products Sydney units?

I have one TPS module but am yet to listen to it. Differences? Preference?
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Sun Feb 26, 2012 3:33 pm

Barney Loveland wrote:I have one of the racks i'll probably not end up using.


I'm keen, Barney.
(~:
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Mon Feb 27, 2012 12:25 am

I would also be interested to hear peoples opinions of the Trimax vs Transmission Products, Type 1 amplifier. There was a comment preferring the Trimax earlier in the thread but I think that was to do with mechanical rather than audio performance.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Mon Feb 27, 2012 12:38 am

Yep, the only reference I've seen - comparing the two - is from "Linear" Chris, in 2005? (above in this post)

I'm hoping the TP products are actually decent, but I can imagine either the design, or components, (or a bit of both) may be different enough to give better or worse results from one manufacturer to the other.

Chris, can you clarify? Could provide a good insight for the rest of us who haven't had the chance to A/B compare.
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Re: ?ABC? Trimax Mic-Pres

Postby mylesgm » Mon Feb 27, 2012 8:00 am

I believe that the trimax and transmission products are essentially the same when they are designated the same (ie type 1 or type 54) as these were designs created specifically for the ABC with a specified circuit and specified quality. Other non-similar numbered products will be different though may be very similar depending on use. I've seen two vu measurement units that had different product numbers built by either trimax or transmission products for different companies (office of the PMG and ABC) but very similar design both cosmetically and internally. Not sure why the transmission products is considered less quality than Trimax as I haven't ever heard units side by side from either company but the build quality is similar.
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Re: ?ABC? Trimax Mic-Pres

Postby GlennS » Mon Feb 27, 2012 10:23 am

I have one of the type 1 Transmission Products amplifiers sitting around for ages. I would really like to get it powered up one day, even just to use it as a 40dB gain block. If anybody has a spare power supply they are willing to part with, or advice on how to otherwise supply power to it, please let me know. At this stage I don't want to throw a heap of money into it, but I have this idea that putting it in front of my LA-4 with an external phantom power supply would be a really nice set up. I have fond memories of using the ones that the big studio gear hire mob that used to be around in Sydney years ago (can't remember their name, based out of Q Studios) had. I think, if my memory serves me correctly, they were Trimax ones not TP though. They just had 3 type 1's in a customs rack with the PS. The rack had phantom & a pad built into it for each of the 3 amps & no gain adjustment. I had variable input on my MTR at the time (Otari MX5050 mkIII) so it worked just fine. They sounded great on drums.
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Re: ?ABC? Trimax Mic-Pres

Postby mylesgm » Mon Feb 27, 2012 10:38 am

Here are some things that will help:

http://www.oneillassociates.com.au/~pon ... /TT_T1.pdf

posting.php?mode=reply&f=1&t=110

Seems like you will need a 275v HT and 6.3v heater. Fairly standard valve power requirements so I'm sure if you aren't able to build one there will be someone local who can. Second link has some ideas about simple mods to the circuit too.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Mon Feb 27, 2012 11:12 am

Thanks Myles - interesting comments, and yes, that's where to get the handbook info from, covering the units from both manufacturers in depth.
The two designs must be quite similar as they are built to achieve the same requirements, and you can apparently swap the modules from each manufacturer, in the same rack, running off the same power supplies - or so the data handbooks tell us.
I can tell you they differ in circuit design, though - at least in some details - and whilst the Trimax TYPE 1 "A63" module utilizes an EF86 & a 12AT7, the TP's unit utilizes an EF86 & a 6AQ5 tube.
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Re: ?ABC? Trimax Mic-Pres

Postby mylesgm » Mon Feb 27, 2012 11:23 am

Ah, is that a revision or the way the Trimax design was from the start? Odd replacement too as the 12AT7 and the 6AQ5 are used for different roles usually.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Mon Feb 27, 2012 11:42 am

Weird, I know! I thought they were totally different tubes - and that's why it got me wondering how different these designs actually are. The Transmission Products one uses the 6AQ5. It's in the circuit data from that link above, and sure enough, in my T.P TYPE 1 amps.
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Re: ?ABC? Trimax Mic-Pres

Postby mylesgm » Mon Feb 27, 2012 12:21 pm

and I wouldn't have thought they were pin compatible either (but I haven't checked) odd though that the modules themselves are interchangeable.
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Re: ?ABC? Trimax Mic-Pres

Postby EvLoutonian » Mon Feb 27, 2012 12:47 pm

If this was just a weird design choice from the Transmission Products team, that could explain Linear Chris' comment about those modules being inferior to the mighty Trimax offerings?
Shall PM Chris to see what he has to throw in to the mix.
(~:
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Re: ?ABC? Trimax Mic-Pres

Postby Alastair Reynolds » Mon Feb 27, 2012 3:30 pm

Guys, like the V72s there were many companies who built Type 1, Type2 etc amps. Trimax, TP, Centre Industries. Some radio stations made their own versions. I have the circuits (Original Blueprints) for 2UE's version
Each approached it in a slightly different way that they thought best , maybe from a cost point of view, fidelity or any number of reasons. Trimax used a paralleled 12AT7 Dual triode to drive the output, TP use a 6AQ5 which is a Beam Power Tetrode (Essentially a 6V6 crammed into a tiny bottle with a 7 pin base instead of an Octal). They'll sound a little different as you would expect, but each would have met the spec for a type 1 amplifier.
Note for 6AQ5...they get real hot. That is probably why Trimax chose the paralleled 12AT7. Performance may have been down but tube life, heat etc may have been better.
That said, don't try and stick a 12AT7 into a TP device or a 6AQ5 into a trimax, It will end in tears.

Wiring to the Multipin plug would have been standard, as were the dimensions so you could plug and play, like your 500 series racks.
Best thing to do is if you have one of each, see which one sounds best.
Last edited by Alastair Reynolds on Tue Feb 28, 2012 8:41 am, edited 1 time in total.
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Mon Feb 27, 2012 8:02 pm

Here are the photos of my rack and modules, they are a bit grubby, like I said, they have literally been under the bench for years.......

Trimax Power Converter
Image

Trimax Type 1
Image

TP Power Converter
Image

TP Type 1
Image

Populated Rack (Trimax Type 1 and Power Conv., TP Type 1 and Power Conv.
Image

Unpopulated Rack
Image

Poulated Rack with the Lid Lifted
Image

Unpopulated Rack with the Lid Lifted
Image

Rack Rear showing external connectors
Image

Internal Rack/Module Connector
Image

TP Type 1 on Left, Trimax Type 1 on Right showing 6AQ5 vs 12AT7
Image

I hope this helps, if you want other shots please let me know.
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Mon Feb 27, 2012 8:07 pm

That said, don't try and stick a 12AT7 into a TP device or a 6AQ5 into a trimax, It will end in tears.


Especially since the 12AT7 is a 9 pin and the 6AQ5 is a 7 pin................
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Re: ?ABC? Trimax Mic-Pres

Postby Alastair Reynolds » Tue Feb 28, 2012 8:42 am

That too :)
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Re: ?ABC? Trimax Mic-Pres

Postby GlennS » Tue Feb 28, 2012 9:08 am

Bob, why do you have 2 power converters in the rack?... and if you're interested in selling one please let me know!
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Re: ?ABC? Trimax Mic-Pres

Postby stosostu » Tue Feb 28, 2012 9:25 am

Glenn, There are 2 power converters because that was what was in the rack when I bought it years ago. My prefernce right now would be to swap the TP Power Converter and the TP Type 1 amplifier for another Trimax Type 1 amplifier, to give me a stereo pair of Trimax amps and a Trimax Power Converter.
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