My beautiful R to R

[graffias79]

This category was bare so I thought I would start it off by showing off my first R to R machine. My new-old Roberts 770x. Now to find more tape for it! *reelspin**reelspin*

http://i26.photobucket.com/albums/c108/graffias79/r770x.jpg

[Des-Lab]

Cool. Isn't Roberts a precursor to Akai? Looking at the faceplate, it definitely reminds me of some older Akai models. That one is definitely clean looking. Especially considering its vintage. That's a true nostalgic piece ya got there!

So that's a tube deck. How do they sound? What kind(s) of tape have you used in the past to get good sound out of it?

[Rex Everything]

Actually Akai built Roberts. They just re-branded them Roberts. This model is essentially the same as the Akai M8

That's a very cool little deck. I was gonna post up in here looking for the Akai M7/M8's and the Roberts 770's and other models like it as I dig the little mono block tube amps in them.

Thanks for the pic and the post.

[Scorpion8]

Gorgeous looking piece of vintage audio. I'll bet she sounds nice too, being tubeified.

[graffias79]

Thanks. It sounds fantastic to be honest. Much better than I thought it would when I picked it up. It records very well. The transport runs like a dream. Smooth as silk, the brakes work perfectly when it stops fast winding as well. The tube section has a uniquely warm rich sound to it, even when simply record-monitoring.

This is my first R to R machine. I never realized how mesmerizing it was to watch the reels (same feeling I get watching vinyl spin I guess lol) The only good tape I have for it is a Maxell UD 135 (?) I think - the box is still packed and in the hallway from the move. Gray and black box design. It is the reel pictured there. I also have a lot of pre-recorded 3 3/4 ips tapes, and some really nasty sounding tapes mostly concertone or white box ones dated from the early 70s that sound cruddy or have dropouts. I also have a couple of scotch ones that I won't play because they are sick with the SSS.

I like to experiment, so I gutted an 8-track (don't worry it was some symphony playing broadway songs) by cutting the splice out, feeding it through a slit in the cartridge and onto a reel. It is Waaay more hassle than it is worth! Oddly, it sounds really nice. Way nicer than any 8-track player I have ever heard (of course 8 tracks have, um, 8 tracks crammed into the same tape width) The only thing is that the 8-track tape seems to be a bit midrange-loud. The Maxell sounds so very much better. Good sound from the whole spectrum.

I was thinking of buying some of these (http://usrecordingmedia-store.stores.yahoo.net/fma1hiouopre.html) to try out. They are not unreasonable, I would be supporting the new sponsor and lets face it, a guy needs more than one viable reel of tape!

I would like to find a couple of extra empty reels as well. Perhaps I will post in the wanted to buy section.

[BroonsBane]

Beautiful deck, congratulations!

[graffias79]

Whoops, sorry.. the tape that I have for it is a Maxell UD 35-90 1800ft. 1.5 mil

[utahusker]

That's a wonderful looking deck. It would of looked good with my Scott 299.

[graffias79]

Here are some more pictures of it in action. You can't see the reels moving in the pictures, though. If there is something that I am not, it is a photographer!

My spot in my new mancave:
http://i26.photobucket.com/albums/c108/graffias79/r770x_np2.jpg

The stately 770x:
http://i26.photobucket.com/albums/c108/graffias79/r770x_np3.jpg

The tape path:
http://i26.photobucket.com/albums/c108/graffias79/r770x_np1.jpg

The tube glow:
http://i26.photobucket.com/albums/c108/graffias79/tubeglow.jpg

[Acoustic]

Lookin' good! :-)<- Is she working OK? Looks like on the right side you have a line out or speaker out... is it hooked up to your main amp? Or are you just running it to speakers?? Inquiring minds.....:D

[graffias79]

Right now it is running from the headphone-out to the receiver on the top (my Realistic STA-2280) and i'm listening through headphones.. it is rockin'! o-o:-)

The "Line" on the left side is for line input. I have it set up as Tape 2 on my receiver. I haven't gotten any speakers to hook directly to it yet.

[Acoustic]

Right now it is running from the headphone-out to the receiver on the top (my Realistic STA-2280) and i'm listening through headphones.. it is rockin'! o-o:-)

The "Line" on the left side is for line input. I have it set up as Tape 2 on my receiver. I haven't gotten any speakers to hook directly to it yet.

Probably like you have it, its better running to your receiver than just to speakers. Just have to get the levels correct and you most likely are getting some tube characteristics in the sound.

[niklasthedolphin]

I love the looks of that Roberts 770X!!!

"dolph"

[gamve]

Sweet looking deck, very retro. Bet the tubes give a glorious sound. BTW what are the valves?

[TheReeler]

If you are asking about the meaning of "valves":

Valves = Tubes

In american english is normal to call them tubes and in british english is normal to call them valves.

[graffias79]

Ok I removed the panels to have a look and here's what I found:

LEFT block: 6267, 12AD7, 6X4, 6BQ5, 6AR5
RIGHT block: 6267, 12AD7, (socket missing), 6BQ5, 6AR5

[graffias79]

Probably like you have it, its better running to your receiver than just to speakers. Just have to get the levels correct and you most likely are getting some tube characteristics in the sound.

Actually it does sound quite nice when I have my headphones plugged directly into the headphone jack :-) They are not the best ones around but they are the best ones that I have: AKG K-220M

[gamve]

Ok I removed the panels to have a look and here's what I found:

LEFT block: 6267, 12AD7, 6X4, 6BQ5, 6AR5
RIGHT block: 6267, 12AD7, (socket missing), 6BQ5, 6AR5

Oh Very sweet. Looks like 6x4 valve rectified EL84 (6BQ5) push pull circuit. Should sound very nice.

[Rex Everything]

I'm going to look at and possibly buy a set of amps out of one of these units tomorrow evening. They make sweet little mono amps. Apparently they can be converted into very nice mic pre amps also.

[stuwee]

J, very nice! You got your dedicated room too! *check**Hi5* Great pics as well. The move seems to have went smoothly and fast .

stuwee

[Jay Pemberton]

Oh Very sweet. Looks like 6x4 valve rectified EL84 (6BQ5) push pull circuit. Should sound very nice.

Not push-pull. They're single-ended outputs.

I have a 770X as well. I also have my Xerox copy of the Sams Photofact servicing data to hand. Here's which valves perform which functions:

EF86/6267: Preamp input pentode. Receives signal from R/P head for tape playback or receives signal from external moving magnet phono cartridge via 'phono playback input' jack.
12AD7 (often has a 12AX7 in the socket): One section of this twin triode receives the signal from the EF86 in play mode, or signals from the microphone or line input jacks when in record mode; this stage feeds the volume control. The other section feeds the EL84/6BQ5 output.
EL84/6BQ5: power output pentode which feeds the output transformer for coupling to the loudspeaker, VU meter and headphone jack. This also supplies the equalised audio signal to the R/P head for recording.
6X4: HT full-wave valve rectifier (aka B+ supply).

Each of the two amplifier chassis contains one each of the above valves. The upper chassis, for the left channel, also contains the 6AR5, a 7 pin miniature beam tetrode, which serves as the bias oscillator, which feeds the erase and cross-field heads when the machine is in record mode.

Other peculiar bits and pieces of info regarding this machine: The aforementioned phono playback input jacks only work when the deck is in playback mode, interrupting the signals from the R/P head when something's plugged into them! Unfortunately, they do NOT make possible direct recording to tape from a turntable equipped with a magnetic cartridge.

Also, the preamp output jacks interrupt the signal just after the volume controls, and before the remainder of each channel's circuitry. Therefore, DO NOT have anything plugged into them when you want to make a recording with the 770X. You will hear the signal going into the inputs via these jacks, but it will not make it any further than them, if anything's plugged into them when this machine is in record mode. You will see no levels on the VU meters, and you will not get any signal to tape either.

One last thing I've seen in those excellent pictures*: Note that Graffias79 is in Wisconsin. Here in the US, where the AC mains frequency is 60 Hz. Look closely at that small screwdriver-adjustment that says OUT 50 ~ -- IN 60 ~. It's in the 'out' position. Therefore, in this position, it should be running on a 50 Hz source to give the correct speed. In other words, the way it's set, with 60 Hz being fed into the machine, everything recorded or played back will be very far off speed to anything recorded on any other machine, on the order of 20%.

This may be changed (do this ONLY when the machine is running) by placing a flat blade screwdriver into the slot, rotating it counterclockwise until it stops, then pushing it in until it stops, then rotating it clockwise to lock it into the inner position.

*: I first saw these pictures on AK quite a few months ago, so it's quite likely Graffias79 saw my postings to the above effect there, and made the appropriate change to the machine.

[gamve]

Not push-pull. They're single-ended outputs.

I have a 770X as well. I also have my Xerox copy of the Sams Photofact servicing data to hand. Here's which valves perform which functions:

EF86/6267: Preamp input pentode. Receives signal from R/P head for tape playback or receives signal from external moving magnet phono cartridge via 'phono playback input' jack.
12AD7 (often has a 12AX7 in the socket): One section of this twin triode receives the signal from the EF86 in play mode, or signals from the microphone or line input jacks when in record mode; this stage feeds the volume control. The other section feeds the EL84/6BQ5 output.
EL84/6BQ5: power output pentode which feeds the output transformer for coupling to the loudspeaker, VU meter and headphone jack. This also supplies the equalised audio signal to the R/P head for recording.
6X4: HT full-wave valve rectifier (aka B+ supply).

Each of the two amplifier chassis contains one each of the above valves. The upper chassis, for the left channel, also contains the 6AR5, a 7 pin miniature beam tetrode, which serves as the bias oscillator, which feeds the erase and cross-field heads when the machine is in record mode.

Other peculiar bits and pieces of info regarding this machine: The aforementioned phono playback input jacks only work when the deck is in playback mode, interrupting the signals from the R/P head when something's plugged into them! Unfortunately, they do NOT make possible direct recording to tape from a turntable equipped with a magnetic cartridge.

Also, the preamp output jacks interrupt the signal just after the volume controls, and before the remainder of each channel's circuitry. Therefore, DO NOT have anything plugged into them when you want to make a recording with the 770X. You will hear the signal going into the inputs via these jacks, but it will not make it any further than them, if anything's plugged into them when this machine is in record mode. You will see no levels on the VU meters, and you will not get any signal to tape either.

Jay, I know just how sweet the EL84 (6BQ5) is in triode mode. The valve pre I am using uses this setup as well. I just assumed your deck was push pull topography as I could not account for the extra valves. Thanks for your explination above. I would love to hear your machine in full flight, Jeez R2R with triode single ended output should be very sweeeeeeeeet.

Try and get some of the earlier Mullard EL84 tubes. The right ones are easy to spot. They usually look sooty/smokey inside the glass and have a prominent hole you cant miss in the plates. I have treid literally dozens of different match pairs in my pre and the Mullards were easily the best. They generaly go for over $100 a matched pair but they are are a hardy valve that will last for years and they sound beautiful.

[graffias79]

Hi Jay,

Actually it is changed now. The reason it was set at 50Hz turned out to be that for some reason, the capstan sleeve needed 50Hz mode for the correct speed. Since the sleeve caused so much flutter I removed it, and have since changed the Hz setting back to 60. I can tell that it is a belt setting when I change it as it feels rubbery to do so. Thanks for the tip by the way!


One last thing I've seen in those excellent pictures*: Note that Graffias79 is in Wisconsin. Here in the US, where the AC mains frequency is 60 Hz. Look closely at that small screwdriver-adjustment that says OUT 50 ~ -- IN 60 ~. It's in the 'out' position. Therefore, in this position, it should be running on a 50 Hz source to give the correct speed. In other words, the way it's set, with 60 Hz being fed into the machine, everything recorded or played back will be very far off speed to anything recorded on any other machine, on the order of 20%.

This may be changed (do this ONLY when the machine is running) by placing a flat blade screwdriver into the slot, rotating it counterclockwise until it stops, then pushing it in until it stops, then rotating it clockwise to lock it into the inner position.

*: I first saw these pictures on AK quite a few months ago, so it's quite likely Graffias79 saw my postings to the above effect there, and made the appropriate change to the machine.

[Jay Pemberton]

Jay, I know just how sweet the EL84 (6BQ5) is in triode mode. The valve pre I am using uses this setup as well. I just assumed your deck was push pull topography as I could not account for the extra valves. Thanks for your explination above. I would love to hear your machine in full flight, Jeez R2R with triode single ended output should be very sweeeeeeeeet.

Try and get some of the earlier Mullard EL84 tubes. The right ones are easy to spot. They usually look sooty/smokey inside the glass and have a prominent hole you cant miss in the plates. I have treid literally dozens of different match pairs in my pre and the Mullards were easily the best. They generaly go for over $100 a matched pair but they are are a hardy valve that will last for years and they sound beautiful.

You get to hear that single ended output as it is, just by plugging those headphones into the stereo headphone jack.

Almost 20 years ago I gutted a really screwed up Sears Silvertone stereo receiver that had single ended EL84 outputs; I used the output transformers to make a stereo headphone amp. It delivered 1 watt per channel with them triode-wired. It drove anything 8 ohms or higher--at ease with anything from Grado SR 225 cans to Altec Lansing A7-500 speakers. Eventually I added a 6SN7 for a front-end gain stage using each of its triode sections for one of the channels. I never did sort out how to make a proper enclosure for the whole thing so it was always a huge pile of wayward blobs, parts and wires. I've never had the money to track down those Mullards, but the best sounding EL84s I came across were a pair of Sylvania 7189s I found in a box of old tubes someone gave me. I used the amp up until about 6 years ago. I still have it, it's in storage somewhere likely drowning in a sea of cobwebs. I ought to dig it up sometime to see if it still works, and if I can sort out finishing the job off after all this time.