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Author Topic: Viking Mono Preamps  (Read 9098 times)

Offline andy_p

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Viking Mono Preamps
« on: June 21, 2010, 06:50:10 PM »
I had this in my garage (I was looking through the old tube things I had around hoping to find something to use as a tube tape head preamp).  I was able to get them working with a cd player going into the high level input.  My guess is the low level input is for a mic.  There are 3 rca terminated cables coming out of the back of each chasis that would I assume connect to the transport.  I am hoping that there is a tape head preamp installed (I hope there is but I haven't looked at the circuit closely enough and have never seen the transport).  There are two trim pots accessible through the tops labelled "adjusted for 1/4 track heads". 
« Last Edit: June 21, 2010, 07:28:42 PM by andy_p »
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

Offline andy_p

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Re: Viking Tube Tape Head Mono Preamps
« Reply #1 on: June 21, 2010, 06:51:08 PM »
 a few more pics
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

Offline andy_p

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Re: Viking Tube Tape Head Mono Preamps
« Reply #2 on: June 21, 2010, 06:52:15 PM »
and a few more
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

Offline andy_p

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Re: Viking Mono Preamps
« Reply #3 on: June 22, 2010, 07:05:32 PM »
I tried selecting "play" and found the active rca terminated cable, a regular line level source overloads the input (like a phono stage) so I am guessing it has a tape head pre.  I tried to access the heads on the otari mx5050mkii (I got a weak output, I was doing this very quickly trying wire jumpers from the plugs at the end of the wire bundles coming from the heads, so I have no idea if I was doing this properly or if it is some sort of output/input mismatch).  I'll probably try the rs1500 via the plug at the end of the head wire bundle next.  While I enjoy doing this because it is free I also am starting to feel anxious to get a TP tape or two and some proper playback electronics (I have the otari mx5050mkii and tascam br-20 which can do it stock so might have to settle on that for now), I regret missing out on the Oistrakh tape. I just picked up lp reissues of burrell/coltrane and sonny rollings colossus so might have to get on board with an order soon to see what I am missing.
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

Offline steveidosound

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Re: Viking Mono Preamps
« Reply #4 on: June 22, 2010, 10:39:02 PM »
These were typically made as outboard electronics for a bare tape transport around 1960. Like others, they probably have line in, line out, unbalanced high impedance mic. in and jacks (or in your case cables) for the record /play heads, and one for an erase head. You used 2 for a stereo configuration and one for mono. It's function was to drive the record head with signal and bias from line or mic. input, drive the erase head with bias, and pre-amplify /eq the tape playback head to normal line out level.
« Last Edit: June 22, 2010, 10:43:00 PM by steveidosound »
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Offline ironbut

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Re: Viking Mono Preamps
« Reply #5 on: June 23, 2010, 02:59:02 AM »
One of the reasons that you're having a problem with gain with those preamps is the change over the years in head design. The early heads, particularly full track mono, were big. So big in fact that when they first introduced 2 track mono and then 2 track stereo, the heads wouldn't fit side by side and still place the gaps in the right place. If you've ever noticed, the early 2 track tapes were specified as "in line". That was opposed to staggered heads where two heads played back the tracks from a different location (staggered) on the tape. You can imagine the problems encountered at that time with each company championing a different standard and today, archivists either have to adjust the location of two heads or record each track digitally and "drag" one track to line up with the other.
Oops,.. that was a little tangent but back to the gain issue, one of the reasons for the size of these heads was to get as much output as possible to meet the demands of the tube electronics of that era.
So, the head needs to meet the needs of the electronics or vise versa.
In general, mating these early repro amps with a more modern head doesn't work very well. I think that even if you were to set up the ideal ratio of input and output impedances, you still wouldn't have very good performance.
It is possible to have heads installed that are more "tube friendly" but that's a little far to go to see if those amps have potential.
steve koto
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Offline steveidosound

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Re: Viking Mono Preamps
« Reply #6 on: June 23, 2010, 07:29:58 AM »
A picture of a slightly later version of the transport that went with your electronics after they started integrating the electronics and transport into a full recorder can be found here -
http://reel2reeltexas.com/vinListU.html.
These were sold under various kit names as well. Heathkit, Allied Radio and I believe Eico all carried versions.
I have a later transport from Allied.
Viking combined with Telex and eventually Magnecord.
This is a factory photo of an early Heathkit version -
http://reel2reeltexas.com/vinAd58HeathKit..jpg
Steve Williams

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Offline andy_p

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Re: Viking Mono Preamps
« Reply #7 on: June 23, 2010, 10:00:25 AM »
Thanks for the information.  I had wondered what the inline heads markings meant on some of my tape boxes.  In any case it is hard to say what the results would have yeilded sonically, it would be interesting to try with some mc sut's but the end result might be dubious.  I was curious about the ampex 350's, they seem to be a similiar vintage but must somehow be an exception?
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

Offline ironbut

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Re: Viking Mono Preamps
« Reply #8 on: June 23, 2010, 12:03:09 PM »
If you have a pair of SUT's laying around, it certainly couldn't do any harm to try using them.
Maybe I didn't make myself clear (nothing new there) but the info regarding staggered vs inline heads was just to give you a bit of background on the evolution of head design. I think the universal switch to solid state electronics allowed the use of lower output heads such as the ones that came stock on your Otari.  In other words, if you didn't do your homework and installed a modern head on most tube based machines, you'd find that the gain would be to low unless you modified the electronics. That might very well involve changing the signal transformers to a higher ratio.
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
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Offline andy_p

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Re: Viking Mono Preamps
« Reply #9 on: June 23, 2010, 12:13:05 PM »
Thanks for further clarification Steve.  I guess I had wondered why there wasn't much discussion about vintage tape head preamps and that pretty much answers it.  The Eros seems to be the best entry point for me pricewise.
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

Offline ironbut

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Re: Viking Mono Preamps
« Reply #10 on: June 23, 2010, 12:27:29 PM »
I agree Andy. The Eros far exceeds it's price when it comes to performance.
Like all of the Bottlehead kits, the manuals and support are second to none. All you really need to bring to the table are decent soldering skills and a handful of tools. The Bottlehead forum is a great place to do any troubleshooting my might need but more importantly (at least to me) is the experience that can be gleaned from other folks who've already built a particular kit and upgrade paths that you might wish to take in the future.

http://www.bottlehead.com/smf/index.php
steve koto
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Offline ironbut

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Re: Viking Mono Preamps
« Reply #11 on: June 23, 2010, 12:32:44 PM »
BTW, I should mention that the Tape Project tapes are the biggest upgrade of all. I know several subscribers who are using stock electronics and are happy as clams doing so.
So, if you have a machine like your Otari that can play these tapes correctly, and you need to decide whether to upgrade your electronics or start buying these tapes,.. no doubt about it, buy the tapes. They're what make all this trouble worth it.
steve koto
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Offline andy_p

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Re: Viking Mono Preamps
« Reply #12 on: June 23, 2010, 12:35:33 PM »
Thanks for the encouragement.  I was just typing that I wanted to get the burrell/coltrane tape before it sold out (listened to an lp reissue last night and it is a must have for me).  Might start by getting at least one tape.
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home

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Re: Viking Mono Preamps
« Reply #13 on: June 30, 2010, 05:00:49 PM »
Andy-try this.  Take the output of your Otari from the normal XLR output jacks and run it straight into the Vikings and then into your preamp.  It shouldn't overload them and you just might be surprised.

Mark

Offline andy_p

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Re: Viking Mono Preamps
« Reply #14 on: June 30, 2010, 07:57:13 PM »
Thanks for the suggestion Mark, I will give that a try.  I have been using a passive tvc for a pre so adding the vikings as a preamp should be interesting. 
Andrew Petty
VPI Aries/SDS, MCI JH 110, technics rs1500, otari mx5050 mkii, tascam br-20, creek cd60, wright sound phono ag, wright sound wpp-100c, promitheus tvc, ARC dual 75, klh model nine, quad esl 57, sonus faber concerto home