Differences between Leslie 147 and 122

[kikedeolivos]

Hi guys,

 

What are the differences between both Leslies regarding "the sound" and how those differences are achieved?

 

(one thing I noticed is that switching speeds on the 147 are very fast, maybe too fast)

 

 

Thank you.

[Bones]

Hey K,

 

Far as I know the 147 is the universal version (suitable for wurlitzers, etc. - uses th 6W pin out) of the 122. The 122 was designed so that its connection fit the hammond 5 pin spec used in hammond tone cabinets. They are the same Leslie otherwise.

[kikedeolivos]

 

Hey K, Far as I know the 147 is the universal version (suitable for wurlitzers, etc. - uses th 6W pin out) of the 122. The 122 was designed so that its connection fit the hammond 5 pin spec used in hammond tone cabinets. They are the same Leslie otherwise.

 

 

Hey Bones,

 

I knew that but I was asking if there's any difference sound wise, given the fact that the 122 has a different amp.

 

Thanks for your input.

[eric]

I forget the technical difference, something about the 122 having balanced power leads vs. the 147 being unbalanced. So the relay is noisier in a 147. I don't think that the amps sound any different, though there is a longstanding folklore that 147s are for rock and 122s for jazz. I have owned and played both and not seen much difference in terms of the way they sound.

[mate_stubb]

Yes, there is a slight difference. The 147 is a little brighter, due to the different input circuitry relating to speed switching.

 

122 has a balanced input, and is designed to mate directly with the balanced outputs of the Hammond console preamp.

 

Speed switching is done by imposing a DC offset signal onto the balanced signal itself, then filtering it out at the leslie amp and controlling a DC coil relay.

 

A 147 has an unbalanced input and as mentioned earlier is designed to pick its signal off of any speaker terminal of any brand organ besides a Hammond console.

 

It sends a switched 115V AC signal down the line to control an AC coil relay. This can be susceptable to clicks and pops when switching speeds.

 

122s and 147s do NOT have different ramp up and ramp down times. This is entirely a function of how the motors are adjusted, and the condition of the belt.

 

However, the 122 does have a DELAY before responding to your switch change. This is because that DC signal I was talking about discharges through a capacitor and takes a second or so to trip the relay.

[kikedeolivos]

Thank you guys.

[Musicale]

I have one of each. I am in the process of turning the 145 into a 122 balanced line input so that it is easier to run off my organ. The 122's are designed specifically for the Hammond world , while the 147's are more "generic". I would think coming directly off a power amp (via speaker connection) would be a different input quality (impedance etc) to the Leslie. The balanced connection is also nice if you have long runs from the organ to the speakers, Supposed to minimize hum. To my ear they are pretty much the same "sound.

Regards,

[Colour]

Anyone have info on the 142 and 145 models? Apparently the 142 is the same as a 122, except in a shorter cabinet, and the 145 is a short 147. Any other differences? The only difference I'm aware of is that the 142 and 145 supposedly don't have as deep of bass due to the smaller cabinet size.

 

I'm looking a Leslie to go with my M3 and I'm considering a 142 (assuming I can locate one). Thoughts, opinions?

[eric]

 

Anyone have info on the 142 and 145 models? Apparently the 142 is the same as a 122, except in a shorter cabinet, and the 145 is a short 147. Any other differences? The only difference I'm aware of is that the 142 and 145 supposedly don't have as deep of bass due to the smaller cabinet size. I'm looking a Leslie to go with my M3 and I'm considering a 142 (assuming I can locate one). Thoughts, opinions?

 

 

Identical to their bigger brothers other than cabinet size and some minor loss of bass response, but this is to their benefit in certain settings if you are staying out of the way of the bass player. Not as good for kicking bass on the Hammond.

[mate_stubb]

 

Anyone have info on the 142 and 145 models? Apparently the 142 is the same as a 122, except in a shorter cabinet, and the 145 is a short 147. Any other differences? The only difference I'm aware of is that the 142 and 145 supposedly don't have as deep of bass due to the smaller cabinet size.

 

 

This is correct.

[TheB3Nut]

There is one other difference circuit-wise between the 122 and 147 amplifiers aside from the input circuit/motor switching schemes. The output stage of the 147 amplifier incorporates a local negative-feedback loop from the output transformer secondary through the cathodes of the 6550's. Each 6550 cathode connects to one leg of the output transformer secondary, and the output stage bias resistor/bypass capacitor is connected between a center-tap in the secondary and ground. In the 122 amplifier, the 6550 cathodes are tied together and connected directly to the bias resistor and bypass cap. The negative feedback gives it a harder sound as you approach overdrive since the feedback loop is attempting to correct for the increasing distortion. The 122 lacks any such correction and has a somewhat more gradual transition from clean to dirty.

[Colour]

 

Identical to their bigger brothers other than cabinet size and some minor loss of bass response, but this is to their benefit in certain settings if you are staying out of the way of the bass player. Not as good for kicking bass on the Hammond.

 

 

Excellent, thank you for the info.

[Musicale]

B3 Nut:

 

Can you explain the characteristics of the negative feedback loop ?

 

Is this a voltage or current applied to the cathode and how does it affect the signal?

[TheB3Nut]

Negative feedback is an out-of-phase voltage applied to the input of an amplifier stage - the thinking being that any distortion components present will be cancelled out when re-introduced into the stage. It works very well, and is an essential ingredient in the design of hi-fi amplifiers. In the case of the 47/147 output circuit the out-of-phase signal is introduced at the cathode (most such loops feed back to the grids of the tubes or bases/gates of the transistors/FETs in the case of solid-state). I'm not sure why Don Leslie elected to take that route, but it is effective and was simple to implement (and simple to remove, if desired.) The fed-back signal could be thought of as an "error" signal and when fed back into the output stage corrects the errors, until the overdrive is so great that the ability of the feedback loop to correct the errors breaks down. This, incidentally, is why many Fender guitar amps sound the way they do versus amps like the Vox AC-30 which lacks any negative feedback around the output stage. The AC-30, lacking any feedback, transitions gradually from clean to dirty, while the Fender seems to break up more abruptly.

 

Clear as mud?

[Musicale]

Interesting. I see that the center tap of the output transformer got directly to ground in the 122 vs a 25 volt to ground through a resistor/capacitor in a network. The feedback signal comes off each leg of the output transformer and is returned to the cathode. Does the push pull aspect of the amplifier stage result in the out of phase signal ?

 

The amount of feedbak applied must then be proportional to the input to the 6550 pair.

 

This I guess means that the 147 is "cleaner" up to a point then the 122 but when really pushed the 147 gets dirtier quicker ?

 

Why doe these amps not have a bias/balance pot in them. Seems that it would be a nice feature to balance the output stage. I suspect that these are built to have a fixed resistor rather than a pot.

 

 

Thanks for the tutoring.

 

Regards,

[TheB3Nut]

Leslie amps have always been fixed-bias, Mr. Leslie liked basic, simple amplifier designs. For the most part he was on the right track as the design has stood the test of time and has proven to be superbly reliable. Being self-biased new output tubes are plug-and-play, making in-the-field service easier.

 

And yes, the feedback loop is essentially "push-pull" like the output. And yes, it's a little cleaner up to a point, then gets quite dirty quickly, with a bit more edginess.

[pianisten]

The Leslies 122 and 147 : 122 is with so called balanced input, i.e. quite immune to noise from the environment. The Leslie speed control is done by adding a "phantom" voltage to the balanced input lines, similar to a balanced mic cable used for condenser mics. They can be connected to Hammond organs by the balanced output transformer, and the grounded midpoint here must be released and added the phantom voltage here for speed shift, it is a quite simple operation. A more independent kit can be built in, but is in fact not necessary.The relay is pulled by a tube(in fact ½ dual tube), and the voltage for the shift is supplied from the 122 itself.

The Leslie 147 is with a single input and is often used by Hammonds with output amplifier, and hence the more agressive sound. It is nice as the 122 until the input is distorted, and in many ways this is a wanted effect.The speed shift control relay is high voltage operated directly by shorting two pins in the connector.

Hope this clarifies some of the confusions as to "tube amplifier Leslies".

 

[Outkaster]

The Leslie 147 is a cabinet that a lot of rock guys preferred.

[moogerfooger]

ding ding ding -- we have winner!

[wesg]

The aggressive sound of the 147 has less to do with the input type, and more to do with the extra stage of negative feedback as compared to the 122. This gives the amp more clean headroom, but when you run out of it, it really starts to distort quickly.

 

From the operator's POV, we must also remember that the 122 switches a little slower than the 147.