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Messages - slideman82

Amplifier Discussion / Re: Ampeg VH-70
August 19, 2012, 01:28:29 PM
Mmmm I don't think so, it's more like a bass speaker, has a lot of punch and compression, but not enough volume... plugged it to my 1x12 Eminence V128 cabinet and a wall of rock appeared! Too much treble and volume difference.
Amplifier Discussion / Ampeg VH-70
August 08, 2012, 05:16:51 PM
Any info about this amp? A friend of mine's got one of these, made in USA, and it hasn't any Celestion speaker but an Ampeg Special Designed one (or something like that) that sounds quite like a Celestion, but I think it's not the original one because it's supposed to be Celestion equiiped (there's a plastic label that afirms that). It seems it's a newer version of the SS-70, but I think it has the same circuitry (I've seen a guts pic and looks the same)
Tubes and Hybrids / Re: My new tube preamp design hums!
February 05, 2011, 12:23:04 AM
hahahaha! Thanks! But don't worryl, zeners are just fine, it's all under calculations, this zeners also feed other preamp, a ss one, down to dual 24V supply, they're quite cool (and I used 2 47V zeners in parallel). I didn't have time to fix it, I think I'll try it tomorrow or may be Sunday.

BTW, I made a mistake in the schematic with vol and master pots! They're wired ok.
Tubes and Hybrids / Re: My new tube preamp design hums!
February 03, 2011, 09:09:00 AM
I've never seen a schematic so badly drawn!
Tubes and Hybrids / Re: My new tube preamp design hums!
February 02, 2011, 07:31:24 PM
I always do star ground, SS preamp doesn't hum or anything, and sounds great! Even with Fets! No IC's! I think zeners I'm using to regulate dual tube supply aren't doing their job, have to recalculate some things... heaters supply is DC, when it was AC was center tapped with a 500 ohms pot I had around there. I think I had less hum with AC heater supply. This hum increases a bit when I turn the volume more than 50% and when I hit the strings, with no signal, almost dissapears. Also have to try shielding tubes, they are a bit close to the power transformer (that's shielded).

Thanks for all these tips!

PS: I'm a bit lazy, that's why I haven't posted the schematic! I'll try to draw it.
Tubes and Hybrids / My new tube preamp design hums!
February 01, 2011, 08:03:14 PM
Hi! Well, I decided to use low voltage tubes in a fenderish style preamp with my all-mosfet power amp. I chose a couple of ECC189, they run really well with about 90V DC. In fact, I used dual 45V DC taken from a couple of zeners (power amp uses dual 50V supply), with 1000uF caps filtering for both lines. It's basically a 3 stage Fender preamp, with a cathode follower after first stage, and before tonestack. Every cathode goes to a resistor to -45V DC, and tonestack and volume and master pots are referred to 0V. I placed a small resistor and a 470uF cap as LPF for first tube (that's first stage and cathode follower) B+ (that's about 44VDC), but didn't make this LPF in negative supply after 2nd tube (2nd and 3rd stage). The fact is when I turn vol pot (right after tonestack, before 3rd stage) a bit of hum appears, so, it must got to do with first stage. I already changed from filament AC to DC supply, 6V regulated. Probably I'll place some small inductors in the tubes supply for better filtering. How does it sounds? Pretty cool!

Any more ideas or comments?

Amplifier Discussion / Re: Fender M80 (bass) problem
November 01, 2010, 09:21:31 AM
Thanks for all! That looks good! I have to try this and some other stuff just to see if it works!
Amplifier Discussion / Re: Fender M80 (bass) problem
October 27, 2010, 11:10:08 PM
Yup, the best tool could be a scope! But I don't have any! I'm from La Plata. I will defeat this problem, it can't beat me! Thanks for all!
Amplifier Discussion / Re: Fender M80 (bass) problem
October 23, 2010, 11:35:29 AM
The output stage works well, bit certainly there's something wrong with the preamp related with increasing temperature... The speakers are alright too, I have some different cabinets... I thought could be a bad zener, but voltage still works ok.

Should we talk in Spanish? Ja!
Amplifier Discussion / Fender M80 (bass) problem
October 20, 2010, 12:03:09 AM
Well, the fact is when I played for some time, when it heats up, the preamp starts to sound like unbiassed, it has no problem with the PA, I plugged the bass directly to the PA and sounded ok. I also installed a couple of cooler fans pointing directly to the OT transistors, but I'm going to disconnect them and see what happens. Any ideas, any similar trouble like this?

Amplifier Discussion / Re: Vintage SS Guitar Amps
March 29, 2010, 11:44:46 PM
Eeeeer... I'm looking for Tube Works 7200 Mos Valve schematic... 100W bass amp... sounded great! But FET-Tube switch wasn't working, I think
Tubes and Hybrids / Re: VOX AD50 problems and mods!
February 26, 2010, 11:21:21 AM
Thanks, anyway! I'll improve filtering. and probably add other cooler. Heatsink it's not quite big, and maybe I'll change it later...

This amp is what I call  a "toy amp". It has some noise gate effect that't can't be switched off, and this removes some of the amp's dynamics (not too much sustain).

I'll see what I can do, I already have a AD30 schematic, it's the same but with dual 30V DC supply instead of 40.
Tubes and Hybrids / VOX AD50 problems and mods!
February 23, 2010, 11:15:51 PM
Hi! I want to fix a problem in a friend's Vox AD 50, it seems that oscillates with distorted amplifier emulations at max gain, master volume and PA gain pot... also sound gets noisy after a few minutes of hard playing. Can I do anything to solve this? Maybe changing output IC? A power amp schematic would help me a lot!

MODS? Pretty easy... just replace 12AX7 for a high quality NOS 12AU7 and 2200 uF caps for 4700... tone improvement! Really awesome!
GREAT TIP! In fact, I already know that, but never done it! Uhm, I remember I changed those ultra fast diodes for others, a bit less fast than the original... but I'm gonna find the orginal ones for better.
Could be that, it doesn't do it till a couple of minutes, and this thing heats up quite much! I thought adding other pair of Tip, so they'd work less hard.