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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 22nd Sep 2019, 7:13 pm   #1
Paulus.d
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Default New amplifier for reel to reel

Has anyone thought of , or designed a new amplifier for an existing reel to reel deck?
Im thinking that a newly designed amp circuit to replace the one out of a tape recorder may be a good idea, using off the shelf parts....
Regards Paul
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Old 22nd Sep 2019, 7:19 pm   #2
Electronpusher0
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Default Re: New amplifier for reel to reel

If you want to go the valve route look in the Mullard book.
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Old 22nd Sep 2019, 7:21 pm   #3
Paulus.d
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Default Re: New amplifier for reel to reel

I was thinking more modern.....
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Old 22nd Sep 2019, 7:46 pm   #4
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Default Re: New amplifier for reel to reel

There's a (later) Mullard book for that

There are lots and lots of transistor amp designs. But you primarily choose a power amp to drive the speaker and you've not said what is being driven or how much power.

Lots of articles are collected on Douglas Self's website.

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Old 22nd Sep 2019, 10:53 pm   #5
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Default Re: New amplifier for reel to reel

Here's the expensive ready-made end of the market!

https://merrillaudio.net/tape-head-preamplifier/

These and other similar units always tend to be playback only as this is pretty easy compared to recording when intimate knowledge of the heads in use is required.

In the past I designed my own full function stereo machine based around Brenell mechanics and my own solid state electronics. It was quite a challenge!
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Old 22nd Sep 2019, 11:22 pm   #6
jamesperrett
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Default Re: New amplifier for reel to reel

When I was first starting out I used a Mullard transistor circuit as the basis for a playback amplifier for my old Brennel MkV. More recently I've been tempted to build something that I can use to replace failing electronics in various mulitrack machines - but it is usually easier to fix the existing cards than build something new.
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Old 23rd Sep 2019, 12:06 am   #7
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Default Re: New amplifier for reel to reel

Cards used in high end tape recorders will be designed to compliment the heads and other requirements ie, speeds eq etc.

Unless you can come up with a better solution than the original manufacturers then in most cases you'd be best repairing the original cards.
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Old 23rd Sep 2019, 1:15 am   #8
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Default Re: New amplifier for reel to reel

Sometime in the very late 1960s or early 1970s, Wireless World published a series of articles by A J Stuart on the construction of a high-quality tape recording pre-amplifier. It was designed specifically for the Brenell tape deck with its Bogen heads. I built this system, and it gave excellent quality. The circuits are simple and use off-the-shelf components (with the exception of the various inductors, for which full construction details are given). I had considerable problems with oscillator stability when switching from mono to stereo recording, which can be a problem with any stereo record amplifier (I eventually solved it by adopting the Revox technique of using a dummy inductor wound to replicate the erase head's properties to replace one erase winding when switched to mono recording).

These circuits might be worth a look at, even if you only needed some of them - they can be built as individual modules. They are very good indeed (IMHO).

Mike

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Old 23rd Sep 2019, 5:55 am   #9
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Default Re: New amplifier for reel to reel

Confusion here. Did you mean power amp or preamp here Paulus?
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Old 23rd Sep 2019, 8:06 am   #10
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Default Re: New amplifier for reel to reel

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Sometime in the very late 1960s or early 1970s, Wireless World published a series of articles by A J Stuart on the construction of a high-quality tape recording pre-amplifier.
Mike
I built the stereo playback board to this design and still use it from time to time. I believe the RCA ICs at its heart are now obsolete though someone may have some NOS, I haven't looked on ebay.
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Old 23rd Sep 2019, 9:17 am   #11
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Default Re: New amplifier for reel to reel

I think that the attached article might be that at interest. It ran in WW 1970 November, December and 1971 January.

Note that at the end of the article, discrete alternative circuits were given for the audio opamps (RCA CA3048 and CA3052) used in the primary circuit. (I think that these were amongst the first “audio” opamps, along with the Motorola MC1303.) Possibly the same basic circuit would be amenable to non-major adjustment to use say the NE5534 family?


Cheers,
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Old 23rd Sep 2019, 9:33 am   #12
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Default Re: New amplifier for reel to reel

I think the CA3048 and CA 3052 disappeared from suppliers sometime in the 1980s. As Synchrodyne points out, Stuart provides the circuit for a discrete component version using only three bog standard transistors per stereo channel.
I also built a version (stereo) using four standard high-quality low noise single op amp chips - can't offhand remember which ones, but TLO72 or something better spec'd. Either of these methods actually gives more flexibility in power supply arrangements, since there's no way of decoupling power supply line to op amps on the same chip that share a common + rail. But actually, if you look at the fully discrete component circuit in Part 3 of the articles, it's so simple that dual or quad op amps seem to offer little additional economy or space saving, and Stuart says that there is no discernible difference in performance.

Mike
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Old 23rd Sep 2019, 11:11 am   #13
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Default Re: New amplifier for reel to reel

It depends what R2R your talking about. If an old Ferrograph or Brennel, then the valve amps in these are a large part of how it sounds, and thus the reason why a lot of folk like them. If a Revox or similar pro R2R, I don't see that you can do much better than the designed amp, they knew what they were doing. Changing a few trannies for better quality low noise parts might result in lower S/N.

However, to a point, a different amp for consumer or similar R2R like an Akai or whatever might be worth looking at, but really as others have pointed out you have to look at the hole signal path including heads and probably a great contributor of signal degradation, the tape transport.It really depends on what your trying to achieve.

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Old 23rd Sep 2019, 1:06 pm   #14
Paulus.d
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Default Re: New amplifier for reel to reel

I actually thought like a board to replace the single pcb valve ones in typical BSR reel to reels...… like new versions of Tandberg circuits...
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Old 23rd Sep 2019, 1:29 pm   #15
Michael Maurice
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Default Re: New amplifier for reel to reel

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Originally Posted by Paulus.d View Post
I actually thought like a board to replace the single pcb valve ones in typical BSR reel to reels...… like new versions of Tandberg circuits...

Am in the only one thinking what would be the point?


You'll need to replace the power transformer as well. If it was me, I'd repair the original amplifier.
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Old 23rd Sep 2019, 2:05 pm   #16
Ted Kendall
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Default Re: New amplifier for reel to reel

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Am in the only one thinking what would be the point?
No, as a matter of fact. The only machinery worthy of the trouble would be Revox or Studer, and it's much better to fix what's there than re-invent the wheel. Mind you, Decca did transistorise their C37s in the late 1960s...
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Old 23rd Sep 2019, 3:25 pm   #17
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Default Re: New amplifier for reel to reel

I agree - if there's an existing amplifier there then fix it. The BSR isn't an ambitious deck, and just about anything that works will probably do it justice.

The OP hasn't been very clear about things. Is it an existing tape recorder that he's aiming to upgrade? Is it just a "bare" deck without any electronics? Is he aiming for mono or stereo? Does he know anything about the heads? (I'm not sure whether BSR just fitted "standard" heads or offered a selection. Either way it might be very difficult to establish what they are, and at least an existing amplifier should have been designed for them.)

Whatever he does, he's going to come right up against the pretty low quality ceiling of 3.75 i.p.s. and the mechanical limitations of the heads and deck, and just about any of the circuits that are around will be more than adequate for that.

Mike
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Old 23rd Sep 2019, 5:12 pm   #18
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Default Re: New amplifier for reel to reel

Quote:
Originally Posted by Ted Kendall View Post
Quote:
Originally Posted by Michael Maurice View Post
Am in the only one thinking what would be the point?
No, as a matter of fact. The only machinery worthy of the trouble would be Revox or Studer, and it's much better to fix what's there than re-invent the wheel. Mind you, Decca did transistorise their C37s in the late 1960s...
I didn`t know that - was it a sucess?

I seem to remember the BBC exercise to transistorise and stereoify the BTR2 in the early seventies was not very successful.
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Old 23rd Sep 2019, 5:50 pm   #19
Ted Kendall
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Default Re: New amplifier for reel to reel

I think they worked all right, but were fairly swiftly superseded by A80s anyway. The electronics were designed by Kerr or McCosh - can't remember which offhand - and were sold off through Jackson's in the late 70s.

The BBC RD4/4, to give it its official title, was a dreadful mess. Not content with putting stereo heads and transistor electronics on the BTR2 transport, some bright spark put in an unsuitable Papst capstan motor and a left-handed copy of the C37 tension sensor. The resulting speed drift made the unit notorious among studio staff - and maintenance staff, come to that. And the mod noise...! Still, it hurried up the scheme which brought A80s into Radio in large numbers.

One project which is worth a read for its entertainment value, if nothing else, is Mike Skeet's conversion of a Fi-Cord 1A to record stereo - two parts in Tape Recorder around 1969.

Going back further, Alan Watling built mono and stereo versions of his own amplifier design around Wearite decks, the stereo unit being built into a Stag dressing table! Hi Fi News, 1958/9-ish.

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Old 23rd Sep 2019, 11:01 pm   #20
jamesperrett
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Default Re: New amplifier for reel to reel

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Unless you can come up with a better solution than the original manufacturers then in most cases you'd be best repairing the original cards.
My thought was prompted by the fact that I need another 8 cards for the MTR90 now that I have a 24 track playback head for it. Used working cards seem to go for around £100 each but my machine is an early Mk1 which is slightly different to the later Mk1s and Mk2s so anything I buy would need to be modified anyway.
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