New old toys

Came back today

A very cool dude did some updating to two old Ampex preamps for me (sorry if the pictures are a bit big):

Glad those arrived safe and sound. Hope they still work…

Reseating the tubes would be a good idea. The one marked V4 (the output tube) will make the output crackly if it’s not in tight. Lemme know if you have problems…

Clava, they rock. Thank you.


Folks, Clava is responsible for the transformation of these preamps, one of which has been out in the weather behind a friend’s garage for ab couple of years, into some mighty fine vintage lusciousness.

SWEET!! Gooey, analog yummy-ness abounds at Tom’s house…


PS Nice job Clava. They look great! Bet they SOUND that way too.

Hi Tom and Clava, All:
I think they are Ampex 601/602 amplifiers… At least they look like them… You talked about them some time ago… Anything they made are Top Quality… I believe they are dated mid '50’s to mid '60’s… maybe later?

It used a huge mic input transformer in it that can’t be saturated…

Can you see? I’m Green-with Envy…


Those do look cool.

And in front of the Christmas tree - where they should be.

"To dad from dad"

Very cool.

You got it, Bill, Ampex of that family, although Clava discovered in the course of the restoration that one of them was sort of an oddball. You might like the fact that one of them was left outside, behind a friend’s garage, for a couple of years, and that friend gave it to me thinking it wasn’t worth messing with. Wonder what he will say now? I don’t think I will warn him. Just invite him over for a beer and a jam.

You guys have to admit that just the coolness factor would be enough, even if they didn’t sound good. :)


As long as you have a thing looking like those and the VU meters bouncing who cares about the rest ?

:D :D


I think they are Ampex 601/602 amplifiers

Yeah Bill, they’re 602’s…sort of… The Ampex 602 was generally a two track machine and had one amp as a “master” and one as a “slave”. It was made so you could have one of the tracks in “safe” mode while recording on the other. Not a true sel-sync system but getting close. The 601 was a mono machine. These amps are the 602 circuit (which is very different from the 601) but look like they were in mono decks. So I’m betting an early version of the 602. Find out when Ampex introduced the 602 and you’d have a good approximate construction date.

And while they have a fixed mic input transformer (unlike the 601, which had a plug in traffo like some of the Altec gear), it’s a tiny little guy. It is apparently a Beyerdynamic traffo and it clearly says “W. Germany”. Interesting that Ampex would go off shore for that one component. It was a good choice, in hindsight.

We tried these at the studio for a few days on a project that was going on. I think they’re worth having even amongst our arsenal of higher end gear. Certainly worth seeking out for an inexpensive rebuild. 'Course maybe I’m just crazy for the old equipment…I still record with this stuff called “tape”. MMMM…tape…nothing smells like a fresh reel of 456 being wound out for the first time. You don’t even have to see the machine, just walk into the control room and that smell hits you the face…

“Tape”? Whazzat? :D Sigh… I hear you Clav. You wanna know what is neat though? My 16 year-old, geetar wankin’ son gave me his Christmas “wishlist” the other day. Guess what was on top of the list? A TURNTABLE! A good ol’ vinyl spinning, wow and fluttering turntable! I almost fell over. This followed by a bunch of LP’s that I may have a hard time finding.

Maybe analog will be resurrected by our youth?



Maybe analog will be resurrected by our youth?

Could be. That’d be fine by me. Among certain circles, vinyl is still pretty big. My buddy’s band sold out their stock of vinyl copies of their new record in a few weeks. I don’t think it was more 2000 copies, but they got snapped up fast. Vinyl costs more per unit to manufacture, is harder to store and ship, and frequently has to sell at a lower price because of the diminishing user base. The margin is much lower for vinyl so lables avoid it. The only people making it work are the super niche bands/lables that know their market cold and can better predict what sales will be before manufacture. Lotta those people are young DIY-ers.

Tape is similar. Among die hards it never went away and never will. It’s not cheap or convenient for the occasional consumer anymore though; not like it was when Tom’s amps were built, or when the Walkman had it’s heyday, for that matter.

Good on yer boy, I say! Rediscovering the sound of the records I’ve been carting around for the past 30 years is always a fun evening…

A few months ago a bunch of us got together and did a comparison of some nice vinyl and CDs - e.g., Born to Run 1/2 speed mastered vs. the newly remastered CD - and there was no comparison - the record just sounded better.

We all are really waiting for the free plug in that really sounds like tape. I almost bought an 8 track reel to reel a while back at the local pawn shop, just to track drums and guitars…but can’t really justify that for what is a weekend hobby for me.

Hey, Clava, here’s a question. What’s the best way to get the signal into my Aardvark Q10? It has dual function inputs, balanced and un, but balanced it goes through the Aardvark preamps, and if I go in either way and turn the trim all the way down I still can’t turn up the Ampex enough to maximize signal to noise - and there is enough noise in the ampex units that it sort of makes a difference. The first 4 channels have inserts - is that the thing to use?

Anyway, I just recorded a vocal with an Audix om-5 into the Ampex, and it sounds ballsy. Very ballsy. These are going to be great for rock singers.

Well, I got to play with these things for most of the day, recording stuff for our family holiday CD. It made my wife’s flute sound great (through a Rode nt3). Also fun for drum overheads. These really are great, Clava.

More info (if you guys want it! :) ). My NTK tube mic does not sound all that great through the Ampex pres. Too much tubularity I suppose. The Rode NT3, a medium condensor, sounds very nice, as does the RCA 77, but the preamps seem to like plain jane dynamics the best, at least to my more-or-less untrained ears. I’ve tried a 57 and an Audix om-5, and both sound great.

A DI bass (an active J-bass) produced a very interesting tone, one that would need supplementing with a mic on an amp, or perhaps another DI through a different preamp - the Ampex added quite a bit of tube-y-ness, and curiously enough did not do so well with the low end. I have to verify that when I have more time. :)


and curiously enough did not do so well with the low end.

The record EQ point is after the connection between the mic input stage and the output stage. It only affects the signal going into the pentode half of the triode/pentode bottle (V2), and you’re not using that half. The repro EQ point is between halves of the dual triode V3, but that tube isn’t even installed. Those EQ points are really to set the emphasis/de-emphasis characteristic for the tape machine heads, not so much like an equalizer type EQ. Also, tape at slower speeds generally has a greater emphasis on the low end naturally, because of how the process works. It’s called “head bump” and all machines exhibit it in one form or another. On my MCI 2" it’s around 85Hz, on the Studer 1/4" it’s around 90Hz, the Scully 1/4" is about 95Hz, and the 3M 2" runs from about 85-100Hz 'cause the heads are so old and worn…super dark machine, the 3M.

All that is a long way of saying those amps weren’t designed to have a huge bass response, since they were designed to work in a system that had it’s own inherent bass response…

Hi TomS:
Do you think it might be what you’re hearing is something that you didn’t expect to hear or that the tracks are void of any colouration? The tracks that you have now are open to add or subtract any signature you want to include with them… My bet is that you have tracks that technically pristine…


Well, Bill, not exactly pristine. There is a lot of colouration, as far as I can tell a whole lot of it from the output transformer. I really have no expectations for these, since I have so little experience with this sort of equipment. :) But the resulting recorded sounds can be EQed with better results than doing the same thing with the sounds recorded just through the Aardvark preamps. That was very interesting to me. I have used n-Track’s EQ reluctantly in the past, because the resulting sounds always sounded a bit off to me. E.g., I tested the Ampex with the RCA 77, and it EQed really easily, without destroying the sound. The same thing was not true when the 77 was recorded either through the Aardvark preamps or my Symetrix 202 - both of which are very, very clean. Does that make sense to you guys?

Clava, I knew about head bump, in an academic sort of way, but I never really thought about what would have to be done to correct for it in the recording and playback electronics - although it is obvious now you mention it. Just like LPs. I guess I was really hearing what I thought I was hearing. The resulting sound on the DI j-bass is fairly aggressive, sort of appropriate for a New Order recording. I like New Order. :D

That other thing about this - I clearly have to pay a lot more attention to gain structure than I have in the past. The Aardvark all-in-one thing makes gain structure really easy to deal with. I’m kind of lazy…

Hi Gents:
I’m looking at your recent reply… Interesting… ???

What comes to mind…

Is there anyway of finding out what the secondary/output impedance of that output transformer is??

If the transformer is not loaded with a corresponding load resistor/network then the primary of that transformer will not reflect to right primary impedance to the plate of that drive tube… and the output level may not be right… Just something to consider here… If you load the preamp’s output into the Ardvark’s input you may not be loading the Ampex’s output properly… If the Ampeg’s load is rated at say 600 ohms… then it might be worth a try to terminate the Ampex’s line-out with a 600 resistor… or resistive network that reflects 600 ohms back into the Ampex’s output transformer… Do you think?

A “T Pad” or an “H Pad” resistive network attenuating some standard level might be what is in order there… If it is… Something to attenuate in the order of maybe 20 db of energy could be needed…

Just a thought… Gents…


Well, I’m in over my head on this technical stuff, but I do have to turn the trim all the way down on the balanced line in on the Aardvark.

Could I use a simple 10 or 20 db pad like is used on mics? One of these in-line things, like this: