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I have found the holy grail.

 
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vojtasTS29
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Joined: 03 Aug 2015
Posts: 313
Location: Prague

PostPosted: Sun Jan 03, 2016 4:47 pm    Post subject: I have found the holy grail. Reply with quote



So i have probably found the best gigging amp ever made.

This thing is absolutely insane. It is a roland solid state preamp into two 7591 tubes(rare af) with a ECC81 phase inverter. Mine had the speaker changed out for a Jensen from a deluxe or something. those very rare 7591s make 30Watts of the sweetest tube saturated sound i have ever heard and once again, along with the super champ tell me, that the power amp is the main thing affecting the sound color.

It also has a super over the top spring reverb, that gives you LSD trips when it is set to 1... 10 is basically noise music levels. It is kind of lightweight, has two channels, an fx loop, somewhat emulated headphone out and a reverb input(no idea about the purpose). And yeah, it is loud. And i am talking insanely bluesbreaker kind of loud. Here in my room, i am having the volume on 1 Very Happy I am in love with that amp.

And guess what. This thing had cost me exactly 5600,- CZK... (220 bucks). I also found out that the 30Watt variant is actually very rare and collectible.
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Bacchus
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Joined: 20 Apr 2006
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PostPosted: Sun Jan 03, 2016 5:04 pm    Post subject: Reply with quote

Nice! Kind of weird and cool!

I also think it's funny that the craze about ten years ago was to have a preamp with a tube in it going into a solo state power amp, and this is the opposite of that.
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vojtasTS29
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Joined: 03 Aug 2015
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PostPosted: Sun Jan 03, 2016 5:08 pm    Post subject: Reply with quote

I think the craze with the single 12AX7 in everything will never go away. Look at taurus amps. They copied the valvestate technology and advertise those amps as a tube amp... They don't sound too bad, but that is so false advertising i don't even.
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vojtasTS29
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Joined: 03 Aug 2015
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PostPosted: Sun Jan 03, 2016 7:07 pm    Post subject: Reply with quote

Schematic. For anybody interested.
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Nick
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Joined: 20 Apr 2006
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Location: Albany, NY

PostPosted: Sun Jan 03, 2016 7:30 pm    Post subject: Reply with quote

Bacchus wrote:
Nice! Kind of weird and cool!

I also think it's funny that the craze about ten years ago was to have a preamp with a tube in it going into a solo state power amp, and this is the opposite of that.


Musicman amps were also like this (tube power section) and those sound amazing. Will never be the norm because "all tube" is one of those buzzwords that guitarists fall for.
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vojtasTS29
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Joined: 03 Aug 2015
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PostPosted: Sun Jan 03, 2016 8:41 pm    Post subject: Reply with quote

Had an eye on the 112RD-65 musicman for a while, too Smile But this was way cheaper and i like the sound even more, i don't think i would use its whole 65 Watts, too. I think Around 30-40 is the sweet spot where you can play even over a hard hitting drummer and not destroy your back...
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Gabriel
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PostPosted: Mon Jan 04, 2016 1:10 am    Post subject: Reply with quote

My little 65 Ampeg jet uses 7591S valves and it sounds awesome. Although it only puts out around 12 watts from the two valves.

That sure is an interesting looking amplifier!
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Fakir Mustache
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PostPosted: Mon Jan 04, 2016 10:14 am    Post subject: Reply with quote

Also interesting the phase inverter is valve.
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vojtasTS29
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Joined: 03 Aug 2015
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PostPosted: Mon Jan 04, 2016 11:49 am    Post subject: Reply with quote

i think that came from the roland philosophy, where they had a lot of sucessful solid-state preamps, but wanted to make the amp valve in the actual amp section.
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NickS
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Joined: 14 Jan 2008
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PostPosted: Mon Jan 04, 2016 3:46 pm    Post subject: Reply with quote

Bloody confusing that the reverb driver op-amp is labelled "1/2 IC2" instead of "1/2 IC1".
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vojtasTS29
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Joined: 03 Aug 2015
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PostPosted: Tue Jan 05, 2016 5:56 pm    Post subject: Reply with quote

Ehh. A little update. THe speaker is actually eminence. Assumed Fender special design meant Jensen, but didn't read the word eminence underneath. Very Happy The tubes are held by really cool spring system with a cap on the tubes head, so they won't get damaged or fall out during transport. The reverb is funny. It is not inside a tank, it is just two springs behind the tubes in the chassis, but sounds really nice nonetheless. The phase inverter tube is actually a standard 12AX7, not the AT7, but i bought it from a guy who repaired amps and don't have a manual, so it is probably right.

And now the controls...
Gainy channel has two volumes for two gain stages and a master labeled knob, which is actually just a loudness control of the preamp and does not affect the power stage... Clean channel has just a single volume knob.
Then you get to your standard 3-Band eq and the reverb knob, which, as i said is fucking insanely verby. Very Happy
Then of course your standby, on/off switch and a pilot light.

You have two input jacks, Hi and Low, which to me means no pedals and pedals, i am finding the hi inputs clean tone kind of nicer however.
You have two FTSW jacks, labeled overdrive and reverb... no explanation needed... Next to them is a front panel acessed FX loop, which i find kind of convenient and nice. Thel last jack is the headphone out.

On the back you get an 1 amp fuse screw in slot, two 8 ohm speaker jacks(but i think they are paralleled, so you have to go 2x16 ohms if you want two speakers and a line output.

Lots of things this little combo can do. It really was the rolands answer to the Mark II. Smile Very Happy
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71Smallbox
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Joined: 04 Jan 2011
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PostPosted: Tue Jan 05, 2016 6:01 pm    Post subject: Reply with quote

How does the dirty channel sound? Roland never seems to get that part right in amps(JC series).
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vojtasTS29
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Joined: 03 Aug 2015
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PostPosted: Tue Jan 05, 2016 7:12 pm    Post subject: Reply with quote

Not too bad, but not very dirty at all. Kinda like the blues drive until you crank the amp really hard and then you get power valve saturation.
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NickS
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Joined: 14 Jan 2008
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Location: Nr. Basinggrad, UK

PostPosted: Wed Jan 06, 2016 2:09 pm    Post subject: Reply with quote

vojtasTS29 wrote:
You have two input jacks, Hi and Low, which to me means no pedals and pedals, i am finding the hi inputs clean tone kind of nicer however.

The Hi input goes straight (well, through 3.3k) to the input transistor with three 1 meg resistors in parallel - input impedance around 330k.

The Low input, when there's nothing in the Hi input, feeds into a divider that drops your input signal to about 1/3rd of its original value and gives an input impedance of around 100K. I would guess that's more for active pickups.

If for some reason you had something plugged into the Hi input at the same time, R101 would be disconnected and the volume/tone could be affected by whatever's connected in its place (like when we couldn't afford an amp each and plugged both guitars into the amp... happy days.

Nerdy stuff:
Overdrive jack/SW1 selects between clean (straight from the input buffer) and the additional gain stage which has the VOL1 control and diode clipping. It also has some roll-off of treble due to C3 and C6. Super nerdy stuff:
Hidden: 
(why put in C6 when there's already C3 I don't know). R12/C3 give a corner (-3dB) frequency of around 3.4 kHz, anything above that will be reduced at 6dB/octave. I can't say what the effect of C6 is since I can't find a data sheet for the 2SK233 FET to assess the gain (Miller effect means the effective capacitance of C6 is 250 pF x gain).
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vojtasTS29
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Joined: 03 Aug 2015
Posts: 313
Location: Prague

PostPosted: Wed Jan 06, 2016 4:18 pm    Post subject: Reply with quote

I am actually glad for people like you who know their stuff Smile I would kind of like to know much more about amps at the schematic level. I mean, thats one of the thing that got me into electric guitar.
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