Twin Tube GFX-1

[MarshallJMP]

Thanks Sparker!

[Iperfungus]

Ciao Riccardo!

Max from Italy (we can exchange private messages in italian  ).

The first GFX1 unit I put my hands on revealed an obvious issue: internal battery was dead.
Now the problem is that it's not so easy to find those damned 4.5V batteries around...but, after a very long quest, I ended to find them for a reasonable price from Amazon US:

https://www.amazon.com/gp/product/B00FED2M9K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

So, if you have a dead battery inside your Twin Tube (and I bet it is...), have a look there: that's the only place where you'll find the battery and get a shipment to Italy for a price that's not robbery.
Just to be sure...I bought 2! 

The second issue was a little more annoying: battery holder destroyed by acid leaking from the battery (shit).
After tons of blasphemies, I found another unit with issues (there's some broken component (a resistor, I bet) in the board that makes the unit smoke as a cigarette 10 seconds after being turned on...) sold for 30 euros with original pedalboard...and with a perfect battery holder!
So I bought it and now I'm going to put a full working unit together from the two.
Another reason why I bought the second unit was the display, since I noticed that first unit's display is a little hard to read...but...surprise! Also the second unit's display shows the same behavior....maybe all GFX1 units had bad displays?
It doesn't matter.

Anyway, I think I will sell the working unit after I'll complete the job (I collected too much stuff...).
If you're interested on what will remain of the second unit for spare parts...just let me know.
Let's keep in contact to see how it will end for both of us, mate.

Thanks for the schema, Sparker!

[Iperfungus]

Hi folks!

How are you doing, wherever you are?

Just a short update about the Digitech GFX1 Twin Tubes.
At the end, I succeeded in putting a 100% fully working unit together.
I picked up the battery holder from the other "broken" unit, removed the damaged holder, soldered the new one and installed the 4.5V battery: now everything works fine again.
I removed the 7025 Groove Tubes and replaced with common ECC83s JJs, since GT are too good for this thing and there's no difference in tone, whatever tubes one uses.
I've to say, to be honest, that I had better memories of these units, but I was wrong.

The overall tone is too compressed (even with compressor turned to off) and a bit too fizzy and fuzzy...
As a preamp, my MP1, JMP1 and PSA rip the Twin Tube in two very easily.
I placed in the MP1 a couple of Ei tubes that performs very well with no noise or microphonic and it plays awesome as I never heard it.

Digital effects? Well...no comparison with a Quadraverb or an Intellifex.

The only positive note is that the GFX1 is very quiet even with gain turned to max and the noise gate works really well (like the one on Quadraverb GT).

Now, the interesting note is that the unit that was intended to be "broken", looks not broken at all.
The previous owner changed one of the two transformers but he mounted the connector on the main board upside down.
Results: holy smoke!!! And smell, of course.
I reversed the connector and there's no smoke anymore, of course.
I anyway assume that some damage somewhere took place, because I start feeling a bad smell a few seconds after turning it on and the connector becomes hot very quickly.
Nothing strange seems to happen and the unit stays on...but I don't like that...the other one shows not these behaviors and it does not smell at all.
I will check and see if the unit can be repaired, but I think it can be.
I will then buy a new holder for the battery (I bought two) and most probably I will sell both the units and the original pedalboard.

It's funny to keep them alive, but I don't like them that much. 

[Iperfungus]

I just discovered another plus of the Twin Tube: it loves overdrive pedals a lot.
And it remains absolutely QUIET even with tons of insane added gain: truly remarkable.
This thing is dead silent: the quitest tube preamp I ever heard.

And it has some interesting hard rock and metal tones as well.
It is not so versatile, you cannot play jazz or blues with this unit, although clean and crunch tones aren't that bad (but there's a noticeable lack of dynamics...).
But if one wants some H/M from the 80s...

A BBE Sonic Maximizer will help, anyway.

I've to spend some more time with GFX1 programming (and, to be honest, it is not a pain in the ass to program...very user friendly).

[Dante]

I hooked mine up the other day, with my BOSS GX-700 & it reminds me of my MP-2...alot.

The tones are dark and wooly, not high and shrill, when you get them overly saturated. The picking dynamics, as stated, are not easy. I'll try some pedals in front of it, thanks for the tip!

[Iperfungus]

I never owned a MP2, but the Twin Tube is as you just described it.

I've to admit it's not that bad, but comparing it to an MP1 is far away from reality a lot.

In any case, if you put a simple booster or overdrive in front of it, you will be pleased by tone and silence: it opens a bit and stays quiet.

Nothing esoteric: something like a good, old Boss DS-1 with low gain will work fine there.

I will pass it through the Quadraverb, before BBE and Intellifex. It will improve everything, as usual.

[Iperfungus]

Ok guys.

Having played with this toy for quite a while now, I've to say that's not bad at all.
You've to adjust the eq in the right way and the Twin Tube can provide interesting overdrive and distortion sounds.
The clean sound that can be obtained by turning off tubes is absolutely nice!

On board effects are not bad, even if not so usable like the ones in other units like the Quadraverb or the Intellifex.

Now that I found good tones from the preamp, I'm gonna modify some patches on the Intellifex to add a little bit of chorus and delay.

What about yours, Dante?
Did you manage to make it ROAR???

The best feature of this unit it's the SILENCE.
I repeat: the quietest tube preamp I ever heard.

[Iperfungus]

I had some time to do tubes rolling and I had to change my mind once again, about this unit.
I was wrong when I stated that it doesn't matter which tubes you use, because the Twin Tube will always sound the same way.
No, it doesn't.

I tested some different tubes there and the winners are....the original long plates 7025 Groove Tubes.
They remind me of the Ei I've put in the MP1, in many ways: they have the best balance between gain and tone.
I start to assume that Twin Tubes voicings are designed around THESE tubes, to get the best results.

The worst result? Standard ECC83s JJs: they have gain, yes...but the Twin Tubes sounds too much compressed, dark and fizzy.
And, in any case, they have the same gain amount of the GTs or just a little more.

Other tested tubes:

1) TAD 7025s Highgrade (V1) and 7025 Highgrade (V2): very nice tone, but less gain. Good results pushing tubes with an external overdrive (a Boss DS-1 is always good).
2) Ruby JJ ECC83s HG+ (V1) and Ruby JJ ECC83s HG (V2): very different from standard JJs! Good gain (but a little less than GTs) and very nice tone (a little better than with the TADS...more round and punchy). Not compressed nor fizzy sound.

I didn't test with mixed tubes, but I'm curious to try the HG+ JJ in V1 and a GT in V2.

Since I decided to keep this unit (I like it more than the Rocktron Chameleon, now that I learned how to use it), I will repair and sell the other one.
And I will keep the GTs!

[Dante]

Thanks for the tube rolling!! That helps immensely

I can get good tones out of my unit..if I shut off the FX. I don't need that thing muddling up my signal chain, I have the Boss GX700 for that. As long as I use it for a preamp only...it works. Great little backup...I'm not fond of the direct sound, but I'm toying with it...possibly get a GCS to tame the fizz.

[Iperfungus]

Hey Dante!  :wave:

Next tubes test: original chinese ADA MP1 tubes! The ones with the 12AX7A red logo only.
Now the Ei tubes are in the MP1 and I forgot its original tubes: they worth a try in the Twin Tube, just to hear...

At the moment, GTs 7025 are the winners.
Otherwise, I would go for Ruby JJs ECC83s HG+ and HG.

I will let you know soon.

About effects, to be honest, I found chorus and flanger quite useless.
But I like that kind of 3D delay, even if it's not so present in the mix and it's short: most of the times, I hear the repeats all around the room, coming from different directions!
Something I never experienced with other delay units.

For other stuff, I prefer the Intellifex a lot.
I didn't test the Digitech with the Quadraverb yet.

Anyway, I share your point of view: very good backup unit.

[Iperfungus]

Jesus Christ!!!

The original MP1 tubes are MONSTERS!
They deliver TONS of gain...

If I want to use the external overdrive with these, I've to lower the gain and/or set the noise gate threshold at higher level.
But, to be honest, you don't need an overdrive with these tubes: just crank the Input Level and that's it!
Wow....f**king, brutal, shreddy tones!

The GTs have a slightly better overall tone, but the anonymous chinese tubes have the highest gain level I ever experienced: with these tubes, I've to set tubes gain and saturation at 9.6 or 10 to get the same gain I've with the GTs at 11 for both saturation and gain, with the same Input Level.
And the tone is very good, anyway.

After some A/B testing, I ended up leaving the original GT tubes inside the preamp, because they have the best definition and clarity, even with insane amounts of gain.
And I like to use an external overdrive.

The little chinese tubes have a lot of gain, but I don't need ALL that gain... 
And, when pushed to the limit, they tend to loose definition.

I really think that those 7025s are the best tubes for the GFX-1, for both gain and tone.

Definitely, tubes rolling makes sense with the Twin Tube.
I was totally wrong!

Dante, for your reference, I'm using "MAIN METAL SOLO" patch (#1 or #61) with modified EQ (more mids and mid-highs).

[Dante]

I used that #1 patch for my 'modern gain' setting (no FX)

[Chip Roberts]

This is a very enlightening thread.  I've seen these units pop up on the used market every now and again and always wondered if they could work as a backup.  It sounds like Iperfungus was able to get some pretty usable sounds out of them (after some fiddling and experimentation  ;) ) I'll definitely check one of these out next time they pop up in my searches.

[Iperfungus]

Hey Chip!

Yes, I found interesting tones playing with the Twin Tube.
You've to spend some time adjusting the eq and delay settings and this thing will start making you smile.
Many of the presets are ridiculously ugly, but you have to never trust presets! 

If you'll find one at reasonable price, give it a chance: it worth a try!
Just remember that most probably battery will be dead and you'll have to replace it.
Have a look here to buy a 100% compatible battery, but in the US it's very easy to find a replacement:

https://www.amazon.com/gp/product/B00FED2M9K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

If you'll find that the battery holder is damaged by acid from battery, just buy a Keystone NO 139 from Mouser or DigiKey, but be careful and buy one with lugs good to be soldered to the board.

This one:

https://www.amazon.com/Battery-Holder-Keystone-modified-terminals/dp/B00SXBGN7M

Just prepare yourself for a long and funny work: to remove the old holder and install the new one, I had to completely disassemble the unit to have access to bottom of main board (there's no a removable bottom lid here, as in the MP1, unfortunately) and do a clean work.
The easy part is that daughter board can be easily removed: it's connected to the main board by 5 connectors and some screws.
Just be careful with the tubes board: it's connected to daughter board with some cables and you've to remove them together, before removing the main board.
Anyway, that's a lot more easy to do the job than describe it: I've done it so many times, that now I can disassemble the Twin Tube and assemble it back in 5 minutes. Blindfolded. 

Where are you from, mate?
There's one for sale here in Italy for 50 euros:

https://www.mercatinomusicale.com/mm/a_digitech-twin-tube-gfx1-guitar-preamp_id6434339.html

You could contact the seller to see if an international shipment could be arranged, but it could cost more than the preamp.

[bunkyloo]

Thanks Iperfungus I just grabbed one with the controller (no cords or cables ) fairly cheap but rattling nuts a loose tube board crappy tubes and a destroyed battery holder and custom graphics  . I fixed with hot glue but  I wouldn't trust it. I just found another one I purchased and I will build the best of two like you did.
Thanks for the info.
Steve
I do agree with everyone though the tone is ok the effects are almost not there.