[Walterwalter]

Hi everybody. Any experience with tube Roberts and Akai M-6, M-7, M-8, 1710 machines? Also with tube Tandberg models 62, 64? I wonder how good was their sound, comparing with later transistor models? One more question: why those old Akai wow and flutter parameters, stated in manuals, are rather bad ( between 0,15-0,20), despite tape transport looks wery clever and solid made from the engeneering point of view (tape tension levers, inertia rollers, etc)?
Tandberg machines parameters are much better (actually, very close to professional standards), despite rather primitive mechanics, comparing to Akai... http://www.nrhf.no/nrhf-TB.html

[Bill Thomas]

The Akai decks of the period were made to "resemble" Ampex 600 series decks.  The Tandberg decks would probably be considered "Semi-Pro" today.  MANY Akai decks (and more commonly, their "Roberts"-branded siblings) found use at small market radio stations who couldn't afford an Ampex 602.  While Tandberg decks would *occasionally* be used at Radio Stations, they were a little expensive.  Not as much as an Ampex, but not all *that* far from it either.  The Tandbergs were used by either High-End Tape Enthusiasts of the day, or in more or less, "reference" applications.  (Courtroom recording, Educational Recording and the like.)

This is not a hard and fast rule by ANY means; just an "observation."

A GOOD tube deck can sound quite beautiful, but then, so can a good solid-state deck.

Bill

[doug s.]

all i know is the amps in the m-8 can be pulled, and make excellent ~5wpc set monoblocks.  wery clean detailed sound w/efficient speakers...

doug s.

[Figo]

I have a Tanberg 64.  It broke and it's nearly impossible to find parts/service for it.

Not recommended, extreme hassle and the SQ wasn't dramatically better than any SS decks.  I'd stick with the modern Revox decks, honestly.

The only real plus on the tandberg was that it was more gentle on my old pre-recorded tapes than the modern decks with the uber-FF/RW

[slbender]

The Akai 1700/1710 and the Roberts equivalents were later than the M-4, M-5, M-6, M-7, M-8.  The 1700/1710 incorporating a small 4 wpc single ended pair of stereo tube amps on one small chassis. The model 1700 and 1710 were similar but one had SS Diodes, the other had a tube rectifier. Great tube sound from either one using the built-in and rather efficient 5" x 8" stereo pair of speakers so don't expect much below 100 Hz. or large amounts of treble, just room filling sound. There may have been several different versions of the 1700/1710 as I believe some use 6AQ5, while others use the 6BQ5 as the output tube.

The earlier M-4, M-5, M-6, M-7, M-8 have a single top mounted mono 5" x 8" speaker, but wholly independent amplifier (monoblocks) each with a complete power transformer, choke based power supply, and tube rectifiers. These are weird.... the universal 100/110/200/220 voltage selector on the wood case is connected to a large external power isolation transformer which has primary voltages (if I recall correctly) of 100/110/200/220 and a single secondary of 100 Volts is external to the monoblocks chassis mounted transformer, which then powers the two more power transformers, one on each chassis which have a 100 Volt connected primary. There is also a 110 Volt (unused) Primary tap on each transformer on each monoblock chassis, which isn't too bad - at least this is true on the M-7, the only one I've dealt with.  With todays 125 Volt lines, tube voltages will be between 15% or 25% higher than nominal if the amps are removed and used connected to the 110 or 100 Volt primary.

The M-Series Amps are again in the 4 Watt range, being single-ended and 6BQ5 based, with an EF-86 input tube. Output transformers are slightly larger than those present in the 1700 series and sound better in the bass.

Back in the day, the wow and flutter of 1950's Studio Ampex Tube based machines, and their clones such as the Akai M-4,5,6,7,8 etc. were rather high figures, and sometimes wow or flutter was audible. Forty-five to fifty years later, those machines would would be worse, not better, so expect high levels of audible defects. The early single motor Akai, Roberts, and Tandberg RTR machines were rather dependent on a long winding belt and crude bearings so they are worse transports than machines of the 1970's and 80's no doubt.

Early Tandberg tube sets The Model 1, 2, 3, 4, 5, 6x, 62x, 64x, etc. had similar transports, a single motor and one long belt, and some were tube or hybrid sets with permalloy heads. Later TB sets were mostly transistor and single or three motor decks without amplifiers or speakers. The transistor decks 3000x, 3300x, 3400x, 6000x, were single motor and the 9000x, 9100x, 9200x, 10X were three motor with some Ferrite heads.

Almost all later machines using three motors were solid state and decks, so its difficult to compare the tube/single motor sets with tube amplifiers, against  transistor three-motor sets sans amplifiers, since later three motor tube sets didn't exist unless some Crown Series 724's or something else having tubes (but usually lacking power amps) could be found.  And while some transistor sets in the 1970's have permalloy heads, many companies later switched to harder Ferrite based heads, which have better wear attributes, but other problems such as gap widening due to edge chipping over time. Attempts to make better long-lasting heads differed from Mfg to Mfg. It might be that permalloy still sounds better in some ways than various versions of Ferrite, Glass covered Ferrite, Diamond, or Molybdenum surfaced heads, even though the former have poor wear attributes and the latter have superior wear but different sonic properties.


-Steven

Hi everybody. Any experience with tube Roberts and Akai M-6, M-7, M-8, 1710 machines? Also with tube Tandberg models 62, 64? I wonder how good was their sound, comparing with later transistor models? One more question: why those old Akai wow and flutter parameters, stated in manuals, are rather bad ( between 0,15-0,20), despite tape transport looks wery clever and solid made from the engeneering point of view (tape tension levers, inertia rollers, etc)?
Tandberg machines parameters are much better (actually, very close to professional standards), despite rather primitive mechanics, comparing to Akai... http://www.nrhf.no/nrhf-TB.html

[Whitese]

have you considered a Revox G36? 

I have a Sony Superscope 555-A that is all tubed and love it, but when I had a Technics RS-1506, sound was quite better even though my Sony had been rebuilt.

Unless your going to drive the speakers with the R2R internal amp, I fail now to see the advantages of the tubed R2R unless your set on one particular model for other reasons.

I heard a G36 driving some Tannoys and it was exquisite.

[doug s.]

...The earlier M-4, M-5, M-6, M-7, M-8 have a single top mounted mono 5" x 8" speaker, but wholly independent amplifier (monoblocks) each with a complete power transformer, choke based power supply, and tube rectifiers. These are weird.... the universal 100/110/200/220 voltage selector on the wood case is connected to a large external power isolation transformer which has primary voltages (if I recall correctly) of 100/110/200/220 and a single secondary of 100 Volts is external to the monoblocks chassis mounted transformer, which then powers the two more power transformers, one on each chassis which have a 100 Volt connected primary. There is also a 110 Volt (unused) Primary tap on each transformer on each monoblock chassis, which isn't too bad - at least this is true on the M-7, the only one I've dealt with.  With todays 125 Volt lines, tube voltages will be between 15% or 25% higher than nominal if the amps are removed and used connected to the 110 or 100 Volt primary.

The M-Series Amps are again in the 4 Watt range, being single-ended and 6BQ5 based, with an EF-86 input tube. Output transformers are slightly larger than those present in the 1700 series and sound better in the bass...

my m8 monoblocs are connected to the outside world via the external isolation transformer you mentioned. these really are some sweet sounding amps- dynamic and detailed, not at all overly "tubey".  find an old m7/m8/etc tapedeck and you can set up these amps for excellent audio on a budget...   

doug s.

[Walterwalter]

 Steven and Doug, many thanks for detailed info. Actually, I'm thinking about trying to connect  something like Akai M-serie  amps, connected to much more advanced tape transport of later 3-motor machines. Of course, there will be some problems with adjustments, and tape-source monitor function will not be operational, however I hope such a project may be of some interest sonically...
  Considering one motor tape transport, I'm still disappointed with what I hear about the early Akai. Once I've used German made Uher Royal De Luxe  recorder, and despite one motor idle roller drive, it's mechanics delivered 0,04%DIN wow and flutter(better than Revox A-77, B-77). The only thing lacking was that sweet tube sound.

[slbender]

Hi Doug,

I'm considering pulling the M-7 Amps to have another small pair of power amps, but they have to be rewired, since they have built-in Tape EQ, so to make them have a flat frequency response for power amp use. So, did you rework or rewire them? Are you using the EF-86 or have you pulled that tube?  Got a schematic of how it came out - which you are using?

-Steven

my m8 monoblocs are connected to the outside world via the external isolation transformer you mentioned. these really are some sweet sounding amps- dynamic and detailed, not at all overly "tubey".  find an old m7/m8/etc tapedeck and you can set up these amps for excellent audio on a budget...   

doug s.

[doug s.]

hi steven,

i bought a service manual for the m8; i'd get you a copy, but to be honest, it really is poor qualiity and extremely difficult to read - i had a hell of a time.  since then, i have seen pristine copies awailable on the web.     anyways, i didn't do any mods whatsoever - all i needed to do was figure out how to connect the wiring from the main isolation transformer to the two amps.  (if i wanted to do mods, i am not sure my manual is legible enough.)  i didn't pull any tubes or anything; the thing seems so overbuilt, i am not sure that lightening the load by removing unused stuff would matter much

there's a couple folks out there that are wery familiar w/these - one guy refurbs them for use as mic amps.  anyways, i emailed the guy re: what i should do w/mine for use as audio amps, & he told me how to run them w/no tape eq so they have a flat frequency response.  (he also said he thinks they are 8wpc; i think he's a bit off; i don't see how an el84 run set could put out any more than 5wpc.  in any ewent, they are really nice sounding, and were a bargain for me; i have ~$80 into them, which included the shipping and the serwice manual...  the guy (donn tarris) said i really don't need to do much, if anything, to make it sound better, if all the parts are ok.  he said i could replace all the p/s caps, clean the contacts/pots/etc...  this guy should know, check out his site. (link below.)  i will email you direct, the emails he sent me re: my m8's, for using them as regular amps...

http://www.vintageaudio.org/home.html
(amp set up as mic preamp):


doug s.

Hi Doug,

I'm considering pulling the M-7 Amps to have another small pair of power amps, but they have to be rewired, since they have built-in Tape EQ, so to make them have a flat frequency response for power amp use. So, did you rework or rewire them? Are you using the EF-86 or have you pulled that tube?  Got a schematic of how it came out - which you are using?

-Steven

my m8 monoblocs are connected to the outside world via the external isolation transformer you mentioned. these really are some sweet sounding amps- dynamic and detailed, not at all overly "tubey".  find an old m7/m8/etc tapedeck and you can set up these amps for excellent audio on a budget...   

doug s.

[PangCat]

         I am looking for some more details about tube Roberts and Akai M-6, M-7, M-8, 1710 machines.., Is there anybody in this thread knows more about this thing .,I really want to know.,

_________________
Tool & Die

[bdwatkins2001]

I have an akai 1700 with the strangest problem, the VU meter works correctly for recording but barely moves during playback even though playback volume is normal. Also does anyone know where to find the following parts circled in the photo, I am looking for the faceplate for the meter, ff/rr lever and speed selector switch.

Thanks in advance

[Aqualung]

Hi Everyone,

I am a new member, from Cape Town, South Africa.
I am interested in getting a pair of AKAI M8 monoblock valve amps going for personal use - love the look, and by all accounts, the sound will be great!
I am struggling with figuring out how to power them up. I have come across this: "all i needed to do was figure out how to connect the wiring from the main isolation transformer to the two amps" by Doug Sedon, and wonder if Doug or anyone else can point me in the right direction.
We have 220v AC mains in SA (actually measuring at about 234v, usually), but my M8 has the 2 monoblocks, with their 100v input power transformers, and in the box was a "main" switchable input power transformer that can accept 220v or 110 v (and more). I have this transformer.
Before I dismantled everything, (and stupidly did not take enough notes about how things were connected) I saw it being plugged into 220v mains, and both 100v monoblocks switched on, and all valves glowed.
Now I cannot seem to figure out how to even measure the output from this main power transformer, nor how to connect up and power up the two 100v monoblocks.
Using a multimeter set to 2000v AV, all the live wires coming FROM the main power transformer show 234v - there are no 100v wires? What am I doing wrong?
Please also see this: http://www.avforums.co.za/index.php/topic,42978.0.html

Many thanks for any advice!
Kind regards,
Johan