Flickinger 351-1 Program Equalizer

[pulse_divider]

Anyone else have any of these? I can't find much info on the net.
It's a 2 space rackmount solid state Pultec-type design with parametric mid. Unbalanced ins and outs with big discrete op-amp on the circuit board.
Just wondering what the value is on these and whether anyone has any further info about them or their history.
I absolutely love the pair I have but need to fund a console purchase and am wondering if they are valuable enough to get rid of, or whether I should just hang on to them.
Thanks.
---Ben

[gevermil]

got some pics ?

[pulse_divider]

I'll post some tomorrow. I thought I had some on my laptop but apparently they must be at home on my desktop.
BTW, before anyone asks. they're not for sale. I'm just interested in tracking down more info right now.
Thanks.

[pulse_divider]

Here's what they look like.

[pulse_divider]

Nobody knows anything about these?

[Silvertone]

Originally Posted by pulse_divider

Nobody knows anything about these?

It's hard to find information about Daniel Flickinger. I use to own one of his 281 8x2 consoles and tried for over two years to find out info about Dan. This was in the early days of the internet. Since then I've had colleagues of his contact me trying to find him. Supposedly he lives in the the bay area somewhere.

Flickinger consoles were famous for starting on fire because 2 different consoles delivered in Nashville actually burst into flames during sessions. Class A consoles run very, very hot!!! I myself never had this problem. In that 281 console Dan had actually use Spectrasonic EQ's.

You are probably not going to find any info on these as just about everything he did was a one off.

What you have is very, very rare. Flickinger probably copied what looks to be a Pultec EQP1A3. I also probably has op-amps for the make-up gain (if it makes up the gain-loss at all).

I myself would not sell this EQ (I really regret selling that 281 console). If it sounds like a Pultec with it's historic build quality (Flickinger built stuff physically really well and component wise as well), I would say it has the same value or close to the same value as the solid state EQP1A3 which Fletcher told me in the past is about 3 to 4K each depending on condition.

Good find! Plug it in, use it and report back. If you ever want to A/B it with the pultec's and happen to live near upstate NY just let me know. I'd love to hear how these things sound.

Have fun!!!

[pulse_divider]

Thanks for the info.
I wasn't planning on selling them, it's just nice to know the value of my studio's high ticket items in case I'm ever in a serious financial bind.
But yeah, they sound amazing and I kind of figured that they were pretty rare. I didn't realize that he did a bunch of one-off stuff, so I guess it's possible that there aren't many or any others.
They do use a big discrete op-amp for make-up gain. Other than that, there isn't really a whole lot on the PC board. And they are unbalanced ins and outs, so no transformers.

[paultools]

I got interested in these when I heard there was one at United Sound in Detroit. There were some previous threads here about the Flickinger consoles.
Also check the REP forum.

[channelcat]

Originally Posted by paultools

I got interested in these when I heard there was one at United Sound in Detroit. There were some previous threads here about the Flickinger consoles.
Also check the REP forum.

Also check Electrical Audio's forum. I remember reading a few threads about Flickinger over there too.

[gevermil]

These people have a console , maybe they could help . http://www.keyclubrecording.com/
You should post an inside pic

[jomo1234]

Ben:

Check with Kevin Coral over at Endless Summer Studios in Kent. I believe he has some Flickenger gear and has some info on Dan.

[sloaneamps]

Hello,

I found this thread while searching for the Daniel Flickinger 351-1. I happen to have one of these. I plan on getting some pics up in the next day or two. I bought from an estate of an audio engineer. This came along with along with several other pieces of vintage equipment about one year ago. I sold several pieces of equipment and have kept some. I do not have a studio and don't foresee having one in the near future. I am more of a guitar amp builder and realize it is pretty rare but I am willing to sell it. Any feed back or advice on how I can get the best price for it?

[electronaut]

I reverse-engineered one of these a while back for another company that was interested in re-issuing it, and designed an updated version of it (new power supply, XLR connectors instead of Jones-type connectors, etc.) Unfortunately, the project never happened.

The circuit is basically a replica of the Pultec EQP-1R, with a couple of minor alterations, and a standard Flickinger op-amp circuit as the make-up gain amplifier. The op-amp doesn't contribute significantly to the sound of the EQ, and in reality any make-up gain stage could be used here, like a 990 or even a tube circuit.

I suppose it could be argued that the Flickinger op-amp and Flickinger (Utrad) input and output transformers do contribute to the sound, but I think the vast majority of the character comes from from the passive filter section and the old 50 mH and 100 mH inductors.

The ones I worked on had been modified to be unbalanced input, if I recall correctly, resulting in one less transformer in the signal path. I wonder if yours is wired the same way?

I asked Dan Flickinger about this EQ a while back, and he immediately laughed, saying it wasn't his idea! Apparently the first one was a special request from a customer, and they made another dozen or so just to make some extra money at the time. Dan is very proud of his achievements in terms of the actual concepts he pioneered in audio, and rightfully so! I think the fact that this EQ is a clone of another design is not something he's particularly proud of. Regardless, it's a great sounding unit and probably will hold its value due to having his name on it, despite the pretty terrible build quality.

Here's a schematic of the design I did, which as stated earlier, is identical to the 351-1 except for the power supply and input and output XLRs.

351-2

[sloaneamps]

Thanks for the reply! As I said, I will post some pics soon. Your post said it is most likely a copy of the Pultec EQP-1R and another states is a copy of the Pultec EQP-1A3. Are these Pultec's pretty similar?

[electronaut]

If I recall correctly, the EQP1R is a sort of "poor man's" version of the EQP1A, but it only makes a difference in the mid to high frequencies where the inductors are in the circuit.

One of the design goals of a passive EQ like this is to present the same impedance to the source signal at every frequency setting, while altering the corner frequency using different inductor/capacitor combinations. This is expensive because it requires a separate inductance value for every frequency, which means a big custom inductor with many taps at specific values. This is how the A version is made.

The R version compromises by using only two standard inductor values (50 mH and 100 mH) in order to get three values (the third being the two in series = 150 mH). With three values of inductance and a range of capacitors, you can get pretty close to the design goal if you give up a little in terms of maintaining the same impedance at all settings. This is a bummer for theoretical circuit-design nerds, but in the real world the difference is probably negligible for most things.

[sloaneamps]

Ok, so I see that the Flickinger 351-1 has been compared to:
1)Pultec EQP-1A3
2)Pultec EQP-1R
3)Pultec EQP-1A

What I have is not tube. It is solid state. From what I can see is that the 1A3 is tube, the EQP-1A is tube, and EQP-1R is tube. So is it safe to say that the this is a solid state copy/clone of the Pultec models?

[electronaut]

No, because the Flickinger 351-1 is not really a "clone" of anything. It is a one-off (or, dozen-off) equalizer that borrows the filter circuit idea from the Pultec EQP-1R, adds a few more frequencies, and inserts a discrete Flickinger solid-state op-amp as the make up gain amplifier in place of whatever Pultec used.

The important thing here is the filter circuit, which I described above.

If you consider the historical context of this, it makes sense: If you had a studio in the early seventies and already had a rack with a bipolar 24 V power supply (or, Flickinger console), adding this outboard EQ with an op-amp would be a lot more economical than a Pultec. In fact, you could easily add 8 or more channels without loading down a power supply too badly, and that would be a HELL of a lot cheaper than 8 units with tube gain make-up amps, or 8 Pultecs of any flavor.

If you'd like to see the EQP-1R circuit and compare the two, here it is.

If I had to guess, I'd say the reason Dan opted for the EQP-1R circuit over the 1A is because the 1A used a proprietary, custom-wound and potted multi-tapped inductor, which would have been a lot harder to find than the standard 50 mH and 100 mH parts used in the EQP-1R.

But who cares about all this shit?? It's an EQ, built by a legendary audio designer, and it sounds GREAT and it's RARE.

Does yours work? How does it sound?

[sloaneamps]

Electronaut,

Again, thanks for all the info. I do not know how it sounds as I bought it from an estate of an electrical engineer and have no way to test it. I don't have a studio. Some info about me would help understand how I accumulated this piece of equipment.

I am basically a guy who tinkers with building and modding guitar tube amps and once in a while, solid state pedals. I play a little bit of guitar but thats about it. I am not even a technical person as far as education and career but I love music and sound. Always wanted to be an audio/recording engineer but life took another road. A neighbor of mine was aware that I was in to tube electronics and audio. He introduced me to the widow of the man who has all this equipment. I ended up buying everything for a lump some. I was mostly interested in keeping the testing equipment, tubes and anything that I could use for amp building. I right away sold the Neumann mics, which were the sweetest part of the score.

I friend of mine came over recently to help be with the Studer B67 and see if it worked. He has asked me about the Flickinger 351-1 and I told him I did not know much about it. He did not know anything about it either but said that I may want to Google it because it may be rare. He was right! Google took me right to this thread and so that is how I arrived here.

So since this is a great and rare piece of equipment I would like to sell it for what it is worth. I would love to be able to test it and see if it works but that may or not be feasible. I know it may be "sacrilegious" to sell something like this but I don't have a use for it now and most likely will not in the near future. It makes more sense to sell it to a person who wants it and can use it now.

[Silvertone]

Originally Posted by sloaneamps

Ok, so I see that the Flickinger 351-1 has been compared to:
1)Pultec EQP-1A3
2)Pultec EQP-1R
3)Pultec EQP-1A

What I have is not tube. It is solid state. From what I can see is that the 1A3 is tube, the EQP-1A is tube, and EQP-1R is tube. So is it safe to say that the this is a solid state copy/clone of the Pultec models?

Pultec EQP-1A3's can be tube or solid state for the make-up gain. Mine were solid state.

This is not a clone of a Pultec or a Lang... (as already stated).

Dan was a funny guy with some of his designs... some were top notch and others were kind of cheap using other companies parts.

I think it's more of a sin for gear like this to sit around and not be used or to just be "collected" because of rarity. In the audio world Flickinger doesn't have quite the name as say Neve or API... nor will it fetch as much (and it shouldn't) as I know this from first hand experience.

That said, selling an EQ that no one has really heard is a bit of a crap shoot. Could be great, could be OK, could be noisy as hell, could possibly not work (if the op-amps have problems, you aren't going to find Flickinger ones to replace them with). So if someone buys on looks alone they could be disappointed. That is the chance you take when you buy "old" rare, "not tested" gear.

Good luck with the sale of this EQ.

[sloaneamps]

Thanks Silvertone,

I just contacted Pulse_Divider who is on Akron OH, which i about 45 minutes south of me. He invited me to test them out. According to this thread, he has two of these. So hopefully they will be "tested" and "working." They are certainly not pristine at this time. I agree it is a crap shoot selling something rare or "one off" thanks to all the recent replies, I am making some headway on how to proceed. Getting them tested and see if they are working would be the first step.

[Silvertone]

Sorry Sloane... she ain't no Pultec. Where are all the inductors? Looks like a pretty face plate.

A power one amp? Never saw one of those on Dans designs.

Looks like some DBX / Innovonics type op-amps for make up gain in there, might be some of Dans custom ones.

Cool looking EQ.

[sloaneamps]

Originally Posted by Silvertone

Sorry Sloane... she ain't no Pultec. Where are all the inductors? Looks like a pretty face plate.

A power one amp? Never saw one of those on Dans designs.

Looks like some DBX / Innovonics type op-amps for make up gain in there, might be some of Dans custom ones.

Cool looking EQ.

No not it's not a Pultec, It is a Flickenger I am not sure what components are the op amps but there are UTC and UTRAD components inside. May be more or better pics would help identify the parts. My guess is the inductors are the big square black box like things on the board. If those are, they are UTRAD. If those silver rectangle things are op amps they are UTC's.

[sloaneamps]

Ok, I took some better pics. Does this help tell me what I have?

[electronaut]

Originally Posted by Silvertone

Sorry Sloane... she ain't no Pultec. Where are all the inductors?

As stated above, it is an EQP-1R type filter circuit (uses only two inductors) with a Flickinger op-amp as the make-up gain amp. The inductors are the two gray UTC cans. One is 50 mH, and the other is 100 mH. (See the schematic I posted above.)

Originally Posted by Silvertone

A power one amp? Never saw one of those on Dans designs.

This is an aftermarket bipolar power supply that someone added later. The unit itself probably didn't come with a power supply, and it certainly wouldn't come with a bipolar 15V supply, since the Flickinger op-amp was designed to run on a bipolar 24V supply. It will work okay on the lower voltage, but you will lose headroom and output drive. (The Flickinger can't drive low-impedance loads with only +/- 15V.)

Originally Posted by Silvertone

Looks like some DBX / Innovonics type op-amps for make up gain in there, might be some of Dans custom ones.

The 351-1 EQ was built with an early version of the Flickinger 535 op amp. It had some components that were omitted in later designs, like trimmer resistors, etc., and was designed into the circuit board instead of the daughter-card modular version found in later Flickinger consoles.

The interesting thing about these two EQs is that they have the modular 535 op-amps hanging in there, in addition to the ones on the circuit boards. By the looks of it, I'd guess that the op-amps on the circuit boards died at some point, and someone just soldered in replacement modular 535's that they had lying around. (Perhaps the original owner also owned a Flickinger console, and had spares on hand.)

Originally Posted by sloaneamps

My guess is the inductors are the big square black box like things on the board.

The black boxes are the transformers. Yours has both input and output transformers, which is nice, so it's balanced in and out, unlike the ones I worked on which had been modified to be unbalanced in. Those are the original Flickinger toroidal 1:1 transformers built by Utrad, also found in later consoles. (They're referred to on Flickinger schematics as "BMFT", or "big mother****ing transformer", as opposed to the smaller 1:2 input transformer used in the mic preamps, affectionately referred to as "LMFT".)

See what I mean about the build quality? No top or bottom covers, and the entire circuit board is mounted by the solder joints on the Jones connector!! (No other screws hold the circuit board in place, which is just insane to me, but hey... they still work after 35 years!)

[sloaneamps]

Thanks again for the analysis Electronaut, your info seems to be very reliable. I am getting some conflicting info on this thread and from emails (or maybe I am just confused) about what I have. Here is an email i got from someone after I sent them the first round of bad pics. Not sure if he saw the new pics.:

"Took a look at what you sent me and the inside shots on gearslutz.
To be honest I was kind of disappointed!

What you have going on with these is not much really.
You have 4 transformers, which are the 2 grey UTCs and the 2 square black Utran made by Triad.
Other than that you have some simple transistors making up an gain stage for either input or output and capacitors and resistors for the selectable freq. bands.
The Power One supply is not original but not a problem. It's suppling the 12 or 15 volts for the units to work.

I was expecting to see some tubes or inductors at least. This is very similar to a lot of passive EQ designs of that era."

So are the two UTC's inductors or transformers? Or transformers being used as an inductor?
I am wondering if this email an Silvertone are basing this off the first round of bad pics?

[electronaut]

Originally Posted by sloaneamps

So are the two UTC's inductors or transformers?

Jeeze, they're inductors!!!!!

Inductance is measured in Henries, or milliHenries. ("MHY" in the old days, "mH" these days) Look at the photo of the two UTC cans. You can see the spec, measured as 50 MHY, printed on the can. The other one (not shown in the photo) says 100 MHY, right? You can also see the winding schematic, printed right there on the can, showing ONE winding. You can't have a transformer with only one winding!

For what it's worth, I spent a lot of time studying this thing, doing research, discovering the similarities between this and the EQP-1R, etc. I've also worked on a bunch of other Flickinger projects, including rebuilding console preamps, EQ's, 535 op-amps, etc., and I've had the good fortune to chat with Dr. Flickinger himself a few times, picking his brain about his designs and hearing his insane stories. There is a ton I don't know about Flickinger's legacy but I do have a general familiarity with many of the designs, as well as the myths.

The only thing I might be wrong about is the exact op-amp circuit on the original circuit board. I believe it's the early 535, but there were other Flickinger op-amps that predated the 535, and it could be one of those. It hardly matters though, since the 535 daughtercards have been wired in there, in place of the other op-amp, which is good because the 535 is a bad-ass op-amp. (But, like I stated earlier, it's supposed to be running off +/- 24V.)

What else do you need to know?

[sloaneamps]

Well that is what I thought, they are inductors! and again I thank you for all your accurate knowledge.

I am a little confused about some of the posts, (not yours), despite the first bad set of pics.
"Where are all the inductors?"


or being told:
"I was expecting to see some tubes or inductors at least."
"You have 4 transformers, which are the 2 grey UTCs and the 2 square black Utran made by Triad"
"Sorry Sloane,....she ain't no Pultec".
"Other than that you have some simple transistors making up an gain stage"

From all you info electronaut, these appear to be fairly typical of how Flickinger made the 351-1?

[electronaut]

I think everyone's just trying to help you out, and the first set of pics didn't show very much, so it's no surprise that some of the guesses didn't turn out to be correct.

The only reason I knew there were inductors in there was because I've been up close and personal with these things in the past. There just aren't that many of these things in the world, so people are drawing from their experience either with Flickinger stuff or other designs of that era. On top of that, there is no shortage of bad information floating around about Flickinger -- myths, falsehoods, embellishments, etc. The fact that Dan designed some of the best stuff of the era, then totally vanished, makes his legacy ripe for reinterpretation.

–*–*–*–*–*

As far as I know, the only tube based design that Dan Flickinger ever put out was the 226 compressor. (Golden Gate Studios in San Francisco has a PAIR of them!) It was basically a Fairchild-style vari-mu, but with an updated and more convenient set of controls. (Continuously variable attack & release, a link to control two units, etc.). As often happens in audio, Dan had a Fairchild of his own and thought of a few ways to improve it, so he did.

Originally Posted by sloaneamps

From all you info electronaut, these appear to be fairly typical of how Flickinger made the 351-1?

How do you define "typical" when there were only a handful of these made? Yours appears to have dead op-amps, with replacements jumpered in, and a third-party power supply with the wrong voltages. How typical can that be?

I'm sure there are die-hard Flickinger fans out there who might want these just to have them, but I couldn't begin to guess what they're actually worth.

[sloaneamps]

ok, fair enough, I meant typical from what you seen. Assuming these work, (which is a big assumption) would it be worth at least getting op amps soldered in? or if it works sell it as is?

[electronaut]

I would just sell them as is. Chances are, anyone interested in buying them would either know how to work on them, or be willing to pay someone to work on them.