ampex 602
« on: December 09, 2004, 04:23:27 AM »
any ideas on chilling one of these these out a bit other than the conventional pad. i like the volume it just peaks too fast. i was thinking of using a 12at7 or 12au7.
has anyone else here messed with one of thes little beasts? its actually alot quieter than i expected. i didn't even use a variac, since the guy at the junk shop already plugged it in to see if it worked.
i'm going to remove the two bundles of wires coming out of it to interface with the tape section. it sounds quite nice already.

Thank you for your time.

ampex 602
« Reply #1 on: December 10, 2004, 03:32:33 PM »
Not looking at the 602 schemo at the moment, but on the 601 there's a pot on the back for record calibration, fiddle with that before you start swapping tubes.  That's where you pick off the mic pre btw.

Okay, 602 manual is there, and so am I now.  You can ashcan valve 2B and and the bias oscillatorvalve 5.  OR try strapping the pentode section as triode and rewire for mixer gain stage out with attenuator/gain pot ala G9.  V2A is mixing stage for line/mic.  You can go in at the play head for another in. If you have the plug in transformer consider yourself lucky, the equivalent would have been UTC A-11,  I have UTC A-10 w/switchable input impedance, will try Cinemag's CM9955-T w/interstage to get it up to 50K secondary to the grid of V1; OEP could be pressed into service here too for little $$$.  Don't forget to rewire the mic XLR to modern pin 2 Hi, as it is 3 is Hi.   W/the dummy plug in the octal socket a dynamic mic will work fine. Valve 4 is the line amp, give's you some flex on outs.  On 601 I have a tone stack where the playhead used to be w/instrument pup in; output jack is 600 ohm unbalanced, direct to board, headphone jack can be xfrmr coupled for modern 'phones if you want headphone monitoring of line in or mic in; don't know the z of the 602 headphone jack as-is, should be around 1K.  I xfrmr coupled the mic out just before Rec EQ pot and snipped everything after the EQ.  Replace plastic paper caps, they should be leaking real good by now.  Leave the Cornell D. mica caps in place and reuse them if they're in abandoned circuitry.  CHeck your B+ for ripple and replace the 'lytics in the filament supply.  One of the reasons it's so quiet is because of the rectified dc filaments voltage.  Much quieter than a 960 deck used for the same purpose.  Final suggestion:  Offer the transport, Jones plugs & suitcase for free or little $$$ to guys on the Ampex list as penance for making a phat toob mic pre from the electronics, and as a favor to yourself don't mention you did so on that list, the controversy will consume bandwidth for days.  I like these better than the Albini 351 mod, I made up panels for the sides to mount in 19" rack and moved pots and in/outs up front.  Put two channels in portable rackcase with stereo tone stack and pack it with guitar splitter and ribbon mic splitter--makes both DI and real time M/S recording channels to mixer.  Want to eventually put an output jack to a guitar amp from the old playback head circuit, self contained M/S stereo acoustic string preamp.  A little bulky but so what?  Check out 601 schematic, very deluxe EF86s and 12AY7, sound is very nice w/distance mic'ing.  Handsome too, like the look of the 600 series electronics.

"The pen is mightier than a flamin' bag of poop."  --Dr. Bartholomew Simpson

ampex 602
« Reply #2 on: December 11, 2004, 11:38:34 AM »
More good reasons to use these electronics in front of your recording rig, DAW or otherwise (reference to Carnegie is in fact and indeed Carnegie Hall:)

**********Date: Wed, 8 Dec 2004 13:58:00 EST
From: <>
Subject: [AMPEX] 15-ips 600

Question arose if Sarser, recording at Carnegie on a 600, ran it
at 7.5 or 15 ips. I'm sure he will confirm 7.5, to the surprise of

In the several years when I decided what audio specials we would
make and which we would not, 15 ips on 600s was forbidden.
Ross Snyder**********

Yes Ross you are right.
The Toscanini Memorial Concert was recorded at 7.5 ips. As I remember, it
was not a 602 but a stereo 600 that I ordered before the stereo version of
the 600 was put into production. I believe it had a type number of  S
followed by 4 digits.
I never asked you for a 15ips 600 but did modify one myself by having a
motor pulley made by Bob Marshal. It was the 600 that Colonel Ranger
installed a sync head on for me. It was the modified 600 that I took to
Puerto Rico to record Casals. I also used it to record the sound on the film
for Amoco at Sebring in 1958.

David Sarser
"The pen is mightier than a flamin' bag of poop."  --Dr. Bartholomew Simpson


ampex 602
« Reply #3 on: December 11, 2004, 05:44:32 PM »
thank you for the reply. my unit does have the accessory transformer. i was thinking the same thing about donating the tape section, too.
i'll post my progress.

Thank you for your time.


ampex 602
« Reply #4 on: December 11, 2004, 06:02:32 PM »
What a shame that these old decks are getting hacked up for their amplifiers. I wish I could find a complete and working 602... to use as a tape deck! (What a concept).

ampex 602
« Reply #5 on: December 11, 2004, 06:15:39 PM »
That is one way to think of it Dave.  I've got a 354 and 4 960's and a 350/3200 (3200 14" reel transport modified to use with stereo 350 channels and heads, heavy braced casting under the transport cover plate, very stiff transport, with Tentrols it can move tape w/decent precision.)  I know there's a lot of love lost for folks who chop the big decks up over on the Ampex list but the 600 series has an equal amount of fans and detractors there.  Something about chopping up bras to make unobtanium belts...  I keep the circuits as the are in the various stages and just add or delete certain chunks  to keep the sound sig Ampex designed.  And I do use them to record, so, I am actually using an Ampex for its intended purpose but just jumping past the old transport which really isn't so good for any kind of critical work.  Even the 350/351/354 is questionable for recording given it's flexi transport plates.  The dumpster dive days are over tho, and I could never vote yes on chopping up a big deck for pre's, like you could without guilt when radio stations were tossing these in the garbage right and left.  So to a degree I agree; but to reproduce the circuit in terms of $$$ would be, mmmm, silly.  Unless it was a repro of the 351 circuit, which seems to have garnered quite a huge fan base, then one might be able to sell outboard repro 351 pre's.  I don't think enuf people know what the other decks sound like so it would be tuff selling a scratch built 601 mic pre circuit.  IMO
"The pen is mightier than a flamin' bag of poop."  --Dr. Bartholomew Simpson


ampex 602
« Reply #6 on: December 11, 2004, 06:43:04 PM »
Do your 960s work? I've got three or four of them, and none of them work. All need belts, and my understanding is that the correct belts are not obtainable. (The nearest equivalents are the wrong thickness and cause the deck to run off-speed). I'm good with electronics, but mechanicals are not really my thing. I'll probably have to call in an expert to get these running.

ampex 602
« Reply #7 on: December 11, 2004, 07:16:37 PM »
Two of the 960's work with belts that had to have been replaced before I acquired them.  Two of them have melted belt goo all over the place.  Lee Hazen on the Ampex list has the skinny on replacements, he knows the right numbers for the proper thickness belts, and I believe he repairs them.  Y're right finding the belts are a challenge but I think it can be done.  Vern Sauer used to have the replacement belts you mention that are just off speed, but he sold off his stock and retired, that was just mentioned on list I don't recall the guys name, Armstrong I think, I'll dig it up for you.  These aren't all that hard to get running at all, way easier than, say, a sewing machine.  I've got a 900 series manual if you need it (no longer copyright protected  :? )  I guess Buddy Holly had a mono version, 920 or 930 or something, that he recorded demos on at home in NYC.  I've bias'd them up to Ampex 632 tape, they record well too, I record the radio with them.  I think that's what they were made for anyway, back when stereo was broadcast on both an FM and an AM station simultaneously.  The Ampex home console preamps can play FM on one channel and AM on another, funky!  The owner's manual has instruction for slap echo, sound on sound and recording on one track while monitoring on the other, like old foreign language tape lab tapes.  See, you can do your homework with them too!
"The pen is mightier than a flamin' bag of poop."  --Dr. Bartholomew Simpson


ampex 602
« Reply #8 on: December 11, 2004, 07:21:23 PM »
I recognize some of those names, because I used to be on the Ampex list, too.

Is that 960 manual the same one "Mr. T" scanned? If it is, I already have it. If not, it might be something I don't have.

Do your 960s have the original felt holdback pads? I know that you're not supposed to use backcoated tape with them because you don't get proper "drag" against the felt.

Damn, my 960s sounded great before the belts crapped out. I hope I can get them running someday. (Too many projects, not enough time!).

ampex 602
« Reply #9 on: December 11, 2004, 07:33:40 PM »
Yeah, Mr. "I pity the fool" T., the same.  Felt pads, yes.  632's polished on the back side.  Isn't on eBone as often as 631 but it shows up from time to time.  631's good too but kinda hissy.  But it's not like you're going to be bouncing tracks, so.  I actually bought an 7 1/2 ips alignment tape for the 632 tape, nuts!
"The pen is mightier than a flamin' bag of poop."  --Dr. Bartholomew Simpson

ampex 602
« Reply #10 on: December 12, 2004, 04:21:49 AM »
Funny you should mention this.

I am also trying to get my 351 preamps restored to be used with a tape transport. I know that the transports of the 35x series do not have beefy plates, but surely this is not a significant problem, right? I mean weren't many masters made with these transports? Anyway, I was hoping to get a AG-350 stereo trasnport and utilize it with my 351 pres, if possible. I don't know if the AG-350's plate is beefier than the 35x transports. I would think it is as it's somewhat well-regarded by some on the Ampex list.

Anyway, I have a page on my 351 pres here.
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

ampex 602
« Reply #11 on: December 12, 2004, 05:58:22 AM »
Hey fazeka, don't know anything about the AG-350 transport but it may have a control box so different it won't work without a lot of fiddling.  If it's more closely related to the 440's then go for the 350.  I don't think the heads on the AG 350 will work with the 351 channels, wrong impedance; but don't take my word for it you might be able to wire them backwards and get them to work.   The 300 had a big casting under the plates called the 'banjo' it provides great stiffness but the 300 transport's big drawback is it wierd shuttle mode lever.  It also has a tire driven capstan; I like it but not everybody does, they claim increased flutter.  I have a 14" 300 that's been modified to 350 style controls w/an edit switch and 350 channels that got skunked big time by genius engineers at Capitol.  The electronics are a HUGE mess!  It has a certain potential as a mastering deck but would require an awful lot of work.  Keep in mind these guys can't bias up past 406, certainly not 456 without some major fiddling; and they won't fully erase 456 either.  The 3200 duplicators are basically the same transport as the 300, but they've got duplicator heads of course.  All these machines are forced tape guidance transports, Studer and AEG went way into precision tape driving mechanism that would not have to rely upon forced guides, again more flutter with forced guidance.  If digital's problems are about sampling rate and dither, analog problems are about flutter and wow.  Good motors and staright as an arrow tape path, no wow.  Resonances in the tape path cause flutter, so if the tensions are off on the machine, or if the guides or heads are dirty or if the reel idler is worn to the point of becoming another tape guide the tape itself will scrape along these mechanical obstacles and start to vibrate, like a violin string and bingo you've got flutter.  Digital seems to have sent a precedent for super precision time base, tape is way less than  precise in duplicating time.  Personally I don't know why time is so important.  Anyway, you're right, these machines produced lots of masters, but your question is sort of like asking "Didn't Mercedes win alot of races in 1951?"  A short but interesting thread on the Ampex list this week revealed there are NO video producers who have even the slightest nostalgiac fondness of tube based video recorders, digital is where it's at and nobody's looking back.  Until, as also mentioned, somebody needs a old 2" Quad tape transfered to digital video.

That said, I'd say yeah, turn it back into a full on 351, it'll certainly have more collector value that way, & it will make suprisingly pleasing recordings, but it will never record like a late model Studer 24 track or an ATR.
"The pen is mightier than a flamin' bag of poop."  --Dr. Bartholomew Simpson


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