Ampeg SVP-Pro Schematic Tutorial - Page 7

cableguy · #**121** 11-24-2012, 05:47 PM

Thanks JGR,

I hate being a tube newb, but dammit this pre sounded great for a while. I'm determined to get it back to that.

Count Bassie · #**122** 12-11-2012, 08:11 PM

I've taken my '96 SVP-Pro to my tech to see if he can get the noise to go away. So far I ain't too happy with it, which is a pity because the sounds that come from it otherwise are just great...

Cactoose · #**123** 12-31-2012, 07:51 AM

I've had an SVP Pro for a few months and resigned myself to the humming.

I was on the verge of getting rid of it.

I bought a cheap Behringer HD400 Hum Destroyer from Amazon, inserted in between the SVP and amp. It worked!

Totally quiet and I mean totally! Just thought I'd share this in case this helps anyone else.

I'm very, very happy today!

Count Bassie · #**124** 12-31-2012, 08:35 AM

Quote:

Originally Posted by Cactoose

I've had an SVP Pro for a few months and resigned myself to the humming.

I was on the verge of getting rid of it.

I bought a cheap Behringer HD400 Hum Destroyer from Amazon, inserted in between the SVP and amp. It worked!

Totally quiet and I mean totally! Just thought I'd share this in case this helps anyone else.

I'm very, very happy today!

Thanks for posting! I'm of to go find one, maybe there is redemption here. You find no degradation of signal at all?

Cactoose · #**125** 12-31-2012, 10:16 AM

No degradation at all, I'm absolutely delighted that £24.00 can sort this problem out! Quite a few different companies make them, I just went for the cheapest as it was an experiment and the Amazon reviews were terrific.

Steve Dallman · #**126** 12-31-2012, 10:46 AM

I have the Behringer as well. It is simply two transformers, which are used to create two TRS balanced, ground isolated inputs and outputs. It simply breaks the ground connection between two pieces of equipment. Noteworthy is the input and output impedance, which is 500 ohms (not K ohms) input and 600 ohms output. This means, low impedance in and out. Depending on the output impedance of the preamp, and the input impedance of the power amp, the low impedances of the HD400 may load down the signal, which could/would reduce high end. While not designed to combat hiss, it may do that if the preamp output impedance is much higher than 500 ohms.

The Behringer is a knockoff of a similar product made by Ebtech which is owned by Morley. The Behringer is around $25 and the Ebtech around $70. These devices can also be used to change a mono unbalanced signal to balanced or vice versa. I can find no info on the input and output impedances of the Ebtech HE-2. It's not on sales sites or in the manual.

When dealing with low impedance signals, my HD400 works very well. Even with high impedances, I've found it useful, if I can deal with signal loss which is dependent on the impedance.

Steve Dallman · #**127** 12-31-2012, 10:51 AM

That exposed "toroidal donut" should be the multi-tapped inductor used in the midrange circuit. Ampegs generally use an inductor/capacitor pair to create the midrange cut/boost and this active midrange circuit is in my mind, one of the keys to the "Ampeg" signature sound. Be it SVT, or PF500, it's there in most Ampegs.

Count Bassie · #**128** 12-31-2012, 11:21 AM

Quote:

Originally Posted by Steve Dallman

That exposed "toroidal donut" should be the multi-tapped inductor used in the midrange circuit. Ampegs generally use an inductor/capacitor pair to create the midrange cut/boost and this active midrange circuit is in my mind, one of the keys to the "Ampeg" signature sound. Be it SVT, or PF500, it's there in most Ampegs.

I get this- now are you saying that this would be compromised by the Behringer doo-dad? Not certain my question is off the mark, but it don't hurt to ask it!

Great info guys, thank you all very much!

vickde · #**129** 01-16-2013, 04:27 AM

Question: I'm tube rolling an SVP-PRO. From the looks of the schematic, the second half of v4 and V5 are cathode followers. I'm new at this - will someone who knows more about these things verify that?

So if indeed this is true, I should avoid using Russian tubes with spiral filaments in these positions, right?

vickde · #**130** 01-16-2013, 05:29 PM

Bump.

dcocharro · #**131** 01-21-2013, 07:57 AM

Hello,

I love the sound of my spv-pro, but unfortunately is really noisy.
I already changed tubes, but i didn't notice any difference.
I was thinking, i notice creates a lot of noise, even creates vibrations in the chassis,
could this be a problem of the transformer? I replace it would this solve the problem of noise?
Another thing I notice, is that the DI out doesn't have ground lift, is this something easy to add?

thanks,
diogo

Count Bassie · #**132** 01-21-2013, 10:55 AM

Quote:

Originally Posted by dcocharro

Hello,

I love the sound of my spv-pro, but unfortunately is really noisy.
I already changed tubes, but i didn't notice any difference.
I was thinking, i notice creates a lot of noise, even creates vibrations in the chassis,
could this be a problem of the transformer? I replace it would this solve the problem of noise?
Another thing I notice, is that the DI out doesn't have ground lift, is this something easy to add?

thanks,
diogo

Scroll up 7 or 8 posts (post #123), and see what cactoose did to fix his noise problem...

Count Bassie · #**133** 01-28-2013, 07:24 PM

Sooo... I've just ordered a Behri HD-400 from Music-Cans' Friend, for use with that noisy SVP-Pro box O'mine. I will post a before/after set of clips from it after I've given it a fair shot, dialing-in, getting some settings together on the preamp.

Talk to youse guys end-of-week. By the way, it's $29.99 and free shipping (Standard Ground-type) at Music-Cans' Friend...

Count Bassie · #**134** 02-01-2013, 09:23 PM

I plugged the preamp into the Behringer HD-400, and then into the crown XLS-402. Pretty danged quiet, it is. I think the noise I'm hearing now is just the power amp. I can now use the SVP-Pro... sounded pretty good tonight at rehearsal. I'm quietly, satisfactorily psyched.

Count Bassie · #**135** 02-10-2013, 12:28 PM

Quote:

Originally Posted by Cactoose

I've had an SVP Pro for a few months and resigned myself to the humming.

I was on the verge of getting rid of it.

I bought a cheap Behringer HD400 Hum Destroyer from Amazon, inserted in between the SVP and amp. It worked!

Totally quiet and I mean totally! Just thought I'd share this in case this helps anyone else.

I'm very, very happy today!

Say Cactoose, how do you have your Behringer HD-400 hooked up to the preamp?

I have an older Crown XLS420 power amp, which has no 'Bridge' mode switch. After contacting a Crown tech phone-dude, I ran properly modded (wired out-of-phase) cables to each of the XLS420's inputs from the two Preamp Outs of the Ampeg. These are 1/4" TRS > XLR cables. So now, how do I properly use the HD-400 in this scenario?

Count Bassie · #**136** 02-13-2013, 05:40 AM

Ay, a little 'Bump' action ovah heah... Cactoose, you in earshot?

Count Bassie · #**137** 02-16-2013, 11:19 AM

Bump? Anyone still entertaining interest in this thread?

bgavin · #**138** 02-16-2013, 06:51 PM

I still watch it, but for new posts relevant to the SVP-Pro.

Count Bassie · #**139** 02-16-2013, 07:40 PM

Quote:

Originally Posted by bgavin

I still watch it, but for new posts relevant to the SVP-Pro.

I'm hooking up that HD-400 to the SVP-Pro, which I'm using with a Crown power amp...

Rippin' Robin · #**140** 04-25-2013, 02:06 AM

Are high-res pics of the 'older' blackface SVPs still wanted? Mine is TPPWI50033, i.e. worldwide model from May 1996. Happily humming and hissing away.

On a side note, during recording last year I found that I very much preferred the SVP into the power amp in of a new SVT-CL rather than use the SVT pre-amp section. Sounded much clearer, beefier and less 'muffled'