That Reverb Thing. Keeping it simple.

[ivey]

Reverb.

It is an issue that stumps most persons that is getting into guitar amplifiers and music in general.

But it is simple really. Most of us old timers, pay little attention to it, because we have dealt with it for such a long time, and in many different ways.

Yet for the new comer, it is a problem or a puzzle that needs to be understood and conquered.

The best way; if not the easy way, to understand reverb. Is to look at it as a black box, which comes with many different input impedance and only two or three different output impedance.

The impedance that it use in yesterday's and today's guitar amplifiers, have not changed very much at all. Only the digital units are new. And most of them are small modular items with input, output, and voltage.

Spring Reverb Tanks used by most guitar amplifier makers and DIY persons. Are 8 ohms, 150-250 ohms, 310-800 ohm, 1450 or greater ohms.

I myself, recommend the 1450 or greater ohms. Because they are easier to drive. And the circuits that are used to drive them, are overly simple and the components needed for the circuits are everywhere. Even in your old transistor radio.

But more on that later.

Most person will come in contacted with these reverb units. The 8EB2C1B and the 8DB2C1D.

These units are the 310 and the 800 ohm impedance units that is used in today's Marshall and Fender amplifiers.

I have laid out a PCB board of the 8EB2C1B and the 8DB2C1D units; using Express PCB, which can be downloaded free from their web site.

So that if you do decide to use the posted file. It would be easy for you.

I have also posted the pdf on Spring Reverb Tanks, by Antique Electronics showing the circuit schematics.

I will post a laid out of the 1450 or greater units, next week. And the following week, I will post a laid of the 8 ohm unit, using solid state drive components, to be used in Fender's Super and Twin Reverb amplifiers.

Take Care

Ivey

[tubeswell]

Good topic ivey. What I have found from my own experiments with getting reverb into amps, is that the gain structure of the recovery side is important for the overall amount of reverb, but the driver stage is important for the 'wetness'. And that overall, 'clean' signals produce better results.

With respect to the commentary in the blurb on spring reverb tanks, AFAICT (which, as everybody knows, is Irish for 'a faict' ;-) , impedance matching is important for the input transducer (where getting a good supply of current is important), but for the output transducer, is not impedance bridging more important? (given that what one is trying to achieve at the pan output, is essentially voltage amplification). JM2CW

[ivey]

Yes, current is very important to the transducer. But it is pointed out by Ron on his site, that We will never get thee amount of current due. And if we do, we could burn or ruin the transducer before we do. So voltage is what we hope to obtain from our efforts.

The rise and fall of voltage will hopefully produce the current needed for the transducer, as its field expands and collapses.

On Ron's site, he posted a good discrete semiconductor drive circuits for reverbs tanks like the 8EB2C1B. An also, a very good one can be found on the Red Circuit site, only there it is use for a different purpose. These circuits give excellent current drive and voltage drive. The thing that most persons that view those circuits fail to understand is that the TO220 units shown are for low impedance output push pull. They configured for driving low impedance loads like speakers. While the GP TO92 or TO39 are configured for high impedance push pull circuits, like line drives or driving high capacitance loads.

Ron used the BC 639/640 transistors. They are expensive, if you are looking towards buying 10 or less. That's about 25 cents a copy. But 2N6517/6520 are better and the cost 8 cents a copy.

I know that you care a great deal about tube electronics. I do also, but tubes are going the way of a very rare wine. They have become too expensive for my taste.

I collect old Televisions from the 1970's to 1990's. I have thousands of salvaged transistors and other good parts. I tweak the hell out of my circuit designs until I get just the sound and tones I desire.

I use Standel's power amp design in my units. The output transistors are 2N3442 or MJ15015.

The 2N3442 are the best sounding. You Think my amp were tube amplifiers if you could hear them.

Standel used the SDT9203, which is a beef up 2N3055.

I can't wait to show you all the MOSFET designs I have to replace the tube circuits. The Tube Cad site gives me very good ideas on circuits to design and try out.

Take Care

Ivey

[ivey]

TA-17 Reverb (Heathkit)

What does Heathkit have in common with Ampeg, Mesa Boogie, Univox, and a host of other well known guitar amplifier builders. The 4FB3A1B reverb tank.

The 4FB3A1B, is a very useful reverb tank; for it allows the builder to do away with the coupling or matching transformer used in all vintage Fender guitar tube amplifiers designs. You will also find it use in the Gibson's solid state amplifers the G20, G30, G40, and their "A" variants.

Of all the circuits out there, the Gibson's solid state reverb circuits are the most desired for tube amplifier use. The problem is..., that most persons, including us "Old Timers" never took a look at it or even given it much thought.

If you are building a solid state guitar amplifier of about 50 watts, I recommend the TA-17 or the Univox UR65N reverb circuits.

They are very simple to build and to get working. And that is the most important factor.

I have posted the PCB layout of the TA-17 reverb circuit. Both drive and recovery circuits. You will only require two transistors. But here is the catch, because there is always a catch. You will need PN3565 transistors. And they are not every where. But Digi-Key and Mouser do have them at about $00.25 to $00.50 each. You can also use the PN3566 as well. So as you can see, they are pricey items, when compared to a PN2222A, which cost $00.04 each.

So why must you use those transistors.

Because of the current, wattage, and gain that they provide. And there are very few transistors that meet those spec's today.

Most BC and 2SC transistors are 50 to 200ma at best. The PN3565 is 500ma @ 500mw, with a gain of 100-600hfe.

You should be able to find the TA-17 schematic on this forum. I will draw up a schematic of the circuits and post it as soon as I can.

If you do not like to use the TA-17 (Heathkits) reverb design. I will post both the Univox and the Gibson's reverb circuit which uses a total of four transistors. Making the use of medium power small signal transistor use..., possible.

If you are wondering as to why the Gibson solid state reverb circuit is a good bet for tube amplifier builders to use; it is because you can use the grid bias voltage to power the circuit. And transistors will last longer and cost less than tubes.

[ivey]

Ta-17 parts placement pdf

Sorry gentlemen;

I am an old engineer and feel that every one are on the same level as I. Sometimes I forget. I must listen to my wife more.

Take Care

Ivey

[ivey]

Also I realized I never posted the parts placement for the first set of PCB's

Here the the ones for the Fender and the Marshall Reverb PCB parts layouts.

All of these parts can be obtained from Radio Shack. Use any fet input dual opamp IC. LM353, TL072, TL082, for best results. Use 4558, NE5532, LM1458, biploar input.

good luck

Take Care

Ivey

[custom_amp_30]

Back in 1962 Zenith produced a Model FV20 which was illustrated in Sam's Photo-facts, Set Number 563, folder 17. Rated at 28 Watts, .27 amp. It uses 6BA8A, 6X4, and 12AX7A. Well thats about all the information that I can give without posting the circuit.

https://www.samswebsite.com/en/photo...&submit=Search

[ivey]

Custom...,

You lost me in the exchange. I went to the site you posted, and they require a purchase.

Are you requesting that I purchase that drawing? And if so, for what purpose?

Take Care

Ivey

[custom_amp_30]

No, That was the only reference that I could post to the actual drawing. Sorry, I'm still not sure what can or cannot be reproduced in order to display someone else's work. (Too many years in the military, sorry) But at least you have the specific drawing number reference and you may know someone with a good stash of Sam' Photo Facts. Oh and about the idea that some information actually be purchased, well, that depends on the honesty of that individual.

http://cgi.ebay.com/ZENITH-FV20-REVE...#ht_500wt_1156

I included this as a alternative Reverb circuit that can be incorporated into any system as it was used back in 1962, sort of like plugging in a stomp box. Its and easy build from items you may already have laying around. (16 RESISTORS AN 7 CAPACITORS) (Transformer is only Primary: 117 V@ .2A Sec: 620 VCT @.030 A Sec 2: 6.3 VCT @1.5A)

Just because it doesn't wear the Fender or Marshall badge doesn't mean that its not a tested design from a once great company. I collect oddball source info and if it can create a bit of interest, why not share... I'm off of my soapbox.

[ivey]

O.K., Custom: it is all clear to me now.

Zenith, produce reverb unit for organ makers, from the 1950's to the 1970's. Many of those organ makers have since gone out of business or were purchase by other organ and musical equipment makers.

Unlike Panasonic and Sansui, Zenith never made a stand alone reverb unit for the audio equipment it made.

The unit you are looking at is a leslie speaker reverb unit. Lowery was one of Zenith customers. As was Stanford Pianos and Organ Co, once of Portland, Or.

Hammond made and had made for them similar units.

Take Care

Ivey

[custom_amp_30]

Thanks for the historic account, I did not know any of that information. I have been staring at this circuit and have most of what's required except the main tube: 6BA8A. Thanks, Just thought I would try and add something different.

[ivey]

You do not need that tube to get the design to work properly. The 6u8, 6hg8, 6an8, or the 6aw8, will work perfect in that circuit.

Zenith, GE, and RCA; design around tube blocks. They seldom design around just one tube.

Take Care

Ivey

[Krwkka]

I'm a little late reading this, but thanks for all that, Ivey. That info is going to come in very handy for me.

[ivey]

Your are very welcome.

I have not been on the site, because I have been designing and testing reverb circuits for using the reverb unit mention above.

I am designing simple transistor amplifier units for driving them. As well as other units.

I want to post designs of simple high powered transistor guitar combo amps, in the range of 50 to 100 watts. While getting most of ones parts from the local Radio Shack store. In fact, if a person can get their hands on just four old transistor TV's, I can tell them how to use 80% of their salvaged parts to build a 30 watt guitar amp, with tremolo and reverb.

There are simple designs that can be modulated together to create powerful guitars amps.

I will post on the site in the future, three designs of homemade heat sinks, that can be used up to 70 watts of output power

Take Care

Ivey