A Matamp for 1/3 of the price

parker_knoll

So I picked up this crazy Hayden that was round the corner from me and had been sitting on ebay forever. They're real unicorns these; no one wants 'em

As I suspected it's basically a Matamp with the voice/filter/FAC knob they usually have, which is a variable low pass filter. Also the Master defeat which is common their models. More unusual is the variable Class A, Class A/B knob. It doesn't do a huge amount. Class A is quieter, of course. AB sounds a bit richer to my ears.

Clean sound is very pokey, and not great (my opinion: i always found them too lower middy and lacking sparkle), but a really glorious high gain sound and masses of gain on tap, plus pentode/triode mode (doesn't sound good on triode) and high and low inputs. It's also plenty bright if you want it to be which has been a problem for me with big Oranges, for example. 

It's tube rectified (5AR4) which is not normal for Matamps. On the old marketing material I managed to dig up they suggest swapping power valves so I guess it's cathode biased.

Some oddities:

- the reverb circuit is badly placed, so that if you turn the master down the reverb basically disappears. Not a big deal as it's a small tank and Matamp reverb never sounded great

- what's the 6V6 doing in there? driving the reverb tank?

- it's advertised as 8W or 28W but running 4 x EL34 it must be putting out much more than that, surely? 

So I guess we have 4 x 12AX7 for the preamp (running a 12AT7 in one slot to tame it a bit), 6V6 for reverb, another 12AX7 phase inverter and 5AR4 rectifier then into the power section. Two massive Dagnell transformers complete the picture. It runs very quiet, especially for how much gain it has. 

It looks like handwired on PCBs on a huge square chassis. The head itself is on 22" wide but very deep. 

Would it be hard to stick a passive preamp out/power amp in so I can run it into and out of a mixer?

Final note - the front panel is ugly as sin, as is the badge. I think Hayden really let themselves down with their aesthetics which perhaps is why they never really took off. These things matter. If I keep it I might put a steel grill on there or recover it black tolex or sparkly grill cloth. 

exocet

I have a Matamp 1224 that uses a 6V6 to drive the reverb.
The EL-34s may well be configured in Class A mode i.e. 4 valves opertating in parallel in Class A mode which would lower the power output to 28watts or 7 watts if running one valve only in class A

parker_knoll

Same designer for the 1224. This one is variable class A/AB. There's a pot on the front for it.

3 preamp valves just for gain stages in a single channel. That's up to six gain stages. No wonder it's so filthy 

ecc83

I found a schematic  but it uses a Si bridge rect and defo fixed bias. I would bet they drive just one EL34 in "class A" cathode biased* as this will give about 8 watts, if the HT were higher the book says 11W at 10%THD. 

For a 'pre out/PA in' (aka "FX loop?) you could use one of Merlin Blencowe's circuits for an FX loop? 

*Would not want it fixed bias. Thermal runaway and to keep the DC balance and low hum, the other three 34s have to be passing the same anode current...LOT of lekky for eight watts! 

Dave.

parker_knoll

ecc83 said:

I found a schematic  but it uses a Si bridge rect and defo fixed bias. I would bet they drive just one EL34 in "class A" cathode biased* as this will give about 8 watts, if the HT were higher the book says 11W at 10%THD. 

For a 'pre out/PA in' (aka "FX loop?) you could use one of Merlin Blencowe's circuits for an FX loop? 

*Would not want it fixed bias. Thermal runaway and to keep the DC balance and low hum, the other three 34s have to be passing the same anode current...LOT of lekky for eight watts! 

Dave.

Confusingly there's two versions. I think the later version might have had two channels with shared EQ and definitely ditched the recto tube. Would you mind sharing the schematic via DM?

For the loop, I don't really need buffering as it's going to a DI box and coming back at line level. It's to run it through a mixer rather than pedals or anything else. 

ecc83

https://el34world.com/charts/Schematics/files/_miscellaneous/Matamp1973gt_120schematic.gif

There you go P' I am not understanding your "DI box and mixer" hook up? Where in the amp circuitry would you insert that? BTW that schematic shows a concertina PI. If you get 'farting out' type distortion at (very!) high drive levels try increasing the value of the grid stoppers to the EL34s. 100k is NOT silly!

Dave.

parker_knoll

I mean just a simple passive loop. I have one on my Burman. 

victorludorum

Does this amp really have the same wiring as a GT120? 

lustycourtier

Decent amps. I bought one off Richard from Embrace about 10 years ago for about £200. Itd been his live go to amp fopr years and was ace.

ecc83

parker_knoll said:

I mean just a simple passive loop. I have one on my Burman. 

Yus, but where do you "break in"?

Dave.

parker_knoll

ecc83 said:

parker_knoll said:

I mean just a simple passive loop. I have one on my Burman. 

Yus, but where do you "break in"?

Dave.

isn't it usually directly before the PI? That's where it is on the Burman according to my schematic

parker_knoll

victorludorum said:

Does this amp really have the same wiring as a GT120? 

no it doesn't. The designer and builder of this, Dave Green, was Matamp's chief designer before jumping ship and this amp bears a lot of Matamp hallmarks like the Voice filter plus the build quality. However, I think the GT120 is an early 70s design. This has more similarity with the higher preamp gain models like GT1. However, I'm not sure any Matamp model has as much preamp gain as this, though I could be wrong. 

andyman

The only question that really matters is: "Does it doom?"

ecc83

parker_knoll said:

ecc83 said:

parker_knoll said:

I mean just a simple passive loop. I have one on my Burman. 

Yus, but where do you "break in"?

Dave.

isn't it usually directly before the PI? That's where it is on the Burman according to my schematic

Can I see that? The grid circuit of V2A is high resistance but then I am not familiar with Pre outs/PA  ins in valve amps, just FX loops with buffers and make up amps. Beer into water with solid state of course, e.g the Bandit 112 love affair! 

Dave.

strtdv

andyman said:

The only question that really matters is: "Does it doom?"

It's a bit of an odd one, if the rated power is 28 watts and it's cathode biased class A there's a fair chance the answer might be no

ecc83

strtdv said:

andyman said:

The only question that really matters is: "Does it doom?"

It's a bit of an odd one, if the rated power is 28 watts and it's cathode biased class A there's a fair chance the answer might be no

Only if the HT is 'king low! The old Mullard 5-20 would kick out over 30W from just two EL34s. 20W was for 0.1% THD IIRC. 

Dave.

parker_knoll

strtdv said:

andyman said:

The only question that really matters is: "Does it doom?"

It's a bit of an odd one, if the rated power is 28 watts and it's cathode biased class A there's a fair chance the answer might be no

Switchable Class A to AB

parker_knoll

andyman said:

The only question that really matters is: "Does it doom?"

Yes it does. It has the low end thickness and the voice/filter/boost (depending on amp) control that let's you dial it to taste. 

I had a choice between a used GT1 and this at literally a third of the price so I thought I'd give it a punt 

guitargeek62

lustycourtier said:

Decent amps. I bought one off Richard from Embrace about 10 years ago for about £200. Itd been his live go to amp fopr years and was ace.

Nice! I saw them play with these (or the Ashdown predecessor, perhaps?) and his tones were stellar all night

andyman

Curious to know your opinion after 6 months of use?