Matamp Minimat mk 1

PaulBrewer

Hi,

I just bought a secondhand Matamp Minimat mk1.
I've replace the one pre and one power amp tubes with JJs and have burned it in for a couple of days.

It sounds grand, but nothing special.

Does anyone know where I might find some simple mods to try?

On first glance it all looks point to point but there's what looks like an op-amp on the input jack connectors board.

An experienced advice would be very welcome.

punchdrunk

have you tried different cabs with it?

Dord

What are you trying to mod it to do?

PaulBrewer

punchdrunk wrote: »

have you tried different cabs with it?

I haven't since I put in the valves.
I bought it with a 1 x12 openback cab which sounds great with another head.

I did run the Amp through a 4x12 pre valve change and was equally unimpressed.

PaulBrewer

Dord wrote: »

What are you trying to mod it to do?

To sound 'better', whatever that might be! Not to radically change everything, just make an 'improvement'

I've not studied it in-depth yet but on first glance it looks like the Op-Amp is the first thing the signal hits.

From then on it's hand-wired valveness

I thought perhaps the Op-Amp might be the source of it's averageness.

Does anyone else own one?

Paolo_M

Haven't used or worked on one before but from the user manual the low input goes direct to the pre amp and high goes via the "booster" which I presume is the op-amp that you're refering to.

Do you still get the same "meh-ness" in tone via that input?

Is it the amount of gain that's letting you down?
The amp only has one pre amp valve which will only generate a small amount of overdrive, as you will notice from the low input. I've tried moding a similar set up amp with only one preamp valve (Harley Benton GA5), pushed it as far as it would go and still could only get to AC/DC levels before it started turning to mush and loosing definition.
The "booster" circuit is there to give the preamp a bit of help but is also probably responsible for the crappy overdrive tones you're getting.

The only mod I can think of for more/better gain is to take out the op-amp and fit another 12AX7 but the chassis looks pretty small and cramped already so it probably wouldn't be a realistic option.

If it's the tone itself, too much trebs, thin low end, not enough definition etc. then you can probably do something about that. Cant find a schematic for it though, so I don't know what values it currently uses.

If you can define what's lacking a bit better we can probably help.

I think there's one of the guys here with one, he seemed happy with his.

PaulBrewer

Ah, that's what I was wondering.

I thought perhaps as the input tube was described as a 'matched triode JJ ECC83S' that it was using 1 'side' of a ECC83 for the normal and both for the boost ?

Paolo_M

No, I don't know for sure, but usually in an amp like this the boost function decreases the voltage divider between the two stages or alters the bias level/s of the stage/s. A single ECC83 stage would barely be able to produce enough signal to drive the power amp to full output on it's own.

Those matched 12AX7s are a load of balls IMO. Each gain stage involves at least two resistors which have a stated accuracy of +/-1% at best. Not much point in a matched valve when the circuit it's in is not matched in the first place.

PaulBrewer

Paolo_M wrote: »

Do you still get the same "meh-ness" in tone via that input?

Is it the amount of gain that's letting you down?

The tone is reasonable enough on a clean sound but has a barky unmusical character with the boost.

I have an 18 watt head, also with JJs and on plugging it in the guitars feel very 'alive' as opposed to the Matamp.

I know it's comparing an apple to a pear but there's no feeling of quality, in my opinion.

However I guess it may be I just don't like what they do?

PaulBrewer

Paolo_M wrote: »

Those matched 12AX7s are a load of balls IMO. Each gain stage involves at least two resistors which have a stated accuracy of +/-1% at best. Not much point in a matched valve when the circuit it's in is not matched in the first place.

Indeed!

So the likelihood is that they're in series as it is for 'normal' use? And the op amp just whacks the first stage harder?

PaulBrewer

Perhaps if I go for the most Hi-Fi Op Amp. It's a plug in one so should be easy to sort.

Would a photo of the guts clarify anything I wonder ?

Paolo_M

PaulBrewer wrote: »

So the likelihood is that they're in series as it is for 'normal' use? And the op amp just whacks the first stage harder?

Yep, that'd be my best guess.

Would a photo of the guts clarify anything I wonder ?

I love a bit of amp porn, not sure if it will help, but throw a few gut shots up anyway.

punchdrunk

i'd go to smallbear and get a socket for the op-amp,then buy a few similar spec op-amps from different brands and swap them out

could it be that the lower wattage of the minimat isn't driving the speaker as hard as the 18w clone is?

is the matamp fixed bias? could it be that the valves are being run too cold buy the value installed?

PaulBrewer

The op amp is already socketed and that's exactly what I was thinking of doing.
It's just a standard 741 in there, what's a posh 741?

I suppose the lower power issue is a possibility, I don't suppose the fact it's a Matamp cab will change that.
Even at 2 watts clean it's quite loud.

I have a 1 x 10 cab I might try.

The guy at Eurotubes from whom I got the JJs thinks it's fixed bias.

Paolo_M

NE5535A, NE5534AP and TL071 are replacements for the 741 chip. The LM308is also a possibility if you can get one. I found those from a Wiki article on the old RAT pedal, as I was interested myself.

If I was guessing I'd say the amp is cathode biased. It's single ended and is only putting out 2 Watts. The circuitry, including the "attenuator", would be a lot easier and more compact to build if it was cathode biased.
Fixed bias only really becomes relevent if you're trying to maximise clean headroom and looking for higher power output levels.
I've yet to see a fixed biased, single ended amp but hey, the worlds full of suprises!!

I should be able to say for certain by looking at the gut shot if you can post it.

The guy at Eurotubes from whom I got the JJs thinks it's fixed bias.

Excellent grammar

PaulBrewer

Paolo_M wrote: »

Excellent grammar

http://www.grammarbook.com/grammar/whoVwhom.asp

PaulBrewer

Bob at EuroTubes says -

"There is no bias adjustment on these amps because they are truly a single ended class A amps."

I'm taking him at his word, I suppose.

boycey

You guys obviously know your tecchy stuff, but if you had any queries Paul I'd give the factory a call - they are an exceptionally helpful bunch when it comes to their product. Customer service at its best in my book.

Theres a few lads on the Matamp forum too who know their Matamps inside out (literally!) - might be a good spot for any modding tips & suggestions.

PaulBrewer

boycey wrote: »

You guys obviously know your tecchy stuff, but if you had any queries Paul I'd give the factory a call - they are an exceptionally helpful bunch when it comes to their product. Customer service at its best in my book.

Theres a few lads on the Matamp forum too who know their Matamps inside out (literally!) - might be a good spot for any modding tips & suggestions.

Good Idea, I've emailed them before but didn't get a reply.

I was unaware there was a Matamp Forum. I Googled 'Matamp Mods' but got nowhere.
Cheers.

Paolo_M

PaulBrewer wrote: »

Bob at EuroTubes says -

"There is no bias adjustment on these amps because they are truly a single ended class A amps."

I'm taking him at his word, I suppose.

Yup, that pretty much confirms that the amp is cathode biased. Cathode bias is often refered to as "self biasing" and requires no adjustment.
Fixed bias, however, usually (though not always, Mesa, 5150 etc) requires adjusting.

boyceys suggestion is a good one, don't know that forum but if it's as good as the plexi palace or metro amp forums then it's definitley worth a shot.

Now where's our gut shot!!

PaulBrewer

boycey wrote: »

Theres a few lads on the Matamp forum too who know their Matamps inside out (literally!)

Holy Feck there are some right ole Train Spotters on the Matamp Forum, I can only imagine the relentless Blues played out in their garages ! .... but little info use found apart from the fact that the Minimats don't seem to be known for being bright.

So we've established she don't need no bias adjusted anyway. I'll give the factory a call tomorrow I think.

Quattroste

boycey wrote: »

You guys obviously know your tecchy stuff, but if you had any queries Paul I'd give the factory a call - they are an exceptionally helpful bunch when it comes to their product. Customer service at its best in my book.

Theres a few lads on the Matamp forum too who know their Matamps inside out (literally!) - might be a good spot for any modding tips & suggestions.

+1 but call them. Their email goes to a receptionist and she vets them.

http://officialmatampownersclub.yuku.com/ This is the forum.

Seziertisch

It might be a case of matching it to the right speaker. Ultimately it is probably only intended for home usage, you can't expect too much at 2 watts. Hooking it up to a 4 x 12 is not going to do it justice.

I know that the Celestion speaker that comes as standard in the 1x12 cabs is not particularly highly regarded. I'd have a shop around for reasonably low wattage 10- or 12-inch speakers and see what turns up. Contact Teb Weber and see what he has to say. Also talk to the guys in the factory and see what they say. I am sure some of them use the Minimat themselves.

Also see what kind of results it produces when you put a mic on it, you might be surprised how it sounds.