PT2399 as a reverb on an hybrid amplifier

hozone · Post by **hozone** » 05 Mar 2015, 22:30

Hello,
I'm building an hybrid guitar amplifier.
The preamp stage it's built on a 12ax7, it has, gain, tone control, and volume control, It's based on the AX84 P1 board.
The amplifier board it's a LM3886, taken apart from a behringer amp.
It sounds pretty good, but now I would like to add a reverb on it.
After this preamp stage i would like to add a PT2399 as a reverb.
Preamp is loaded with 200V DC, opamp used on the reverb with +15V 0 -15V DC for the , +5V for the PT2339 board, and also +28 0 -28 on the amplifier board.
At present I'm playing around the Small Time delay with tails.
I'm using TL072 as pre and post gain for the reverb.
My first question is, what's the gain that you suggest for those pre and post opamp? What's the suggested configuration mode (I'm trying with non inverting amplifier) ?
Suggestions?

Thank you!

mictester · Post by **mictester** » 06 Mar 2015, 07:16

Unfortunately your question is rather like "what size shoes should I buy?" without telling us the size of your feet!

You need to tell us the levels that come out of your preamplifier stage, and the sensitivity of the power amplifier!

The 2399 isn't a great way of getting reverb on its own - take a look at the internals of a Belton "brick": Three 2399s in parallel with differing delays and a complicated feedback arrangement to echo the echoes... With a bit of noise reduction, this approach gives fairly good reverb, but not as good as you get from a real spring-line.

hozone · Post by **hozone** » 06 Mar 2015, 18:09

You are right.
Given gain and vol MAX.

Sine input: 250hz/00mV, give and output of 8.9V, so 89X gain.

Yes i know spring-line sound better, but i haven't got any sping box. Also I've read about the Belton "brick".. but I just would like to try with a single PT2399, before buying something new

Thank you!

Nocentelli · Post by **Nocentelli** » 06 Mar 2015, 18:44

I'm not sure a single pt2399 can do convincing reverb, but it can easily do a fairly clean short delay (<300m) which can add space a similar way to reverb: bjf's deep blue delay/madbean's sea urchin is a nice simple circuit to try out.

hozone · Post by **hozone** » 06 Apr 2015, 21:30

Hello,
I've finally complete this circuit. The final effect sounds like a delay / echo more than a reverb, but i like how it sounds for my hybrid amplifier.

hozone wrote:My first question is, what's the gain that you suggest for those pre and post opamp? What's the suggested configuration mode (I'm trying with non inverting amplifier) ?

I'm answering to this after an investigation on "Small Time delay" and "Sea Urchin" circuit, or similar. I hope that what i'm writing here it's right.
To me, the input and output gain of the opamp stage is set up in order to manatin a 1x gain between the input signal and the ouput mixed (wet) or not mixed (dry) signal.

Said this, my reverb circuit looks like the one attached here. I take +-15V power output from the amplifier power board i'm mounting this circuit on. A1 is the input from the preamplifier, A2 is the output to the amplifier stage.
I will post as soon as possible the complete circuit of the hybrid amplifier.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 07 Apr 2015, 07:04

Ofcourse it sounds like a delay. You would have known if you cared to read this thread.

~arph · Post by **~arph** » 07 Apr 2015, 11:02

Why don't you just get a belton brick

hozone · Post by **hozone** » 07 Apr 2015, 17:12

Dirk_Hendrik wrote:Ofcourse it sounds like a delay. You would have known if you cared to read this thread.

I've read this thread, I care about feedback on user post, expecially on my questions. Also I've ear same sample on youtube, I just would like to experiment on this IC too

~arph wrote:Why don't you just get a belton brick

I've some PT2399 lying around and i would like to use experiment on this IC

hozone · Post by **hozone** » 01 Apr 2016, 12:02

I've finally post on this blog the amplifier that contains this reverb emulation board:

http://davidegironi.blogspot.it/2016/04 ... -tube.html

Schematics and video sampled on that page.