Steerpike said:
Yeah that's only dust
I'm still puzzled by the bass loss though. I've tried swapping input and output valves, giving nothing but flavour difference. I've replaced the powersupply rectifiers and electrolytic caps. Cleaned the heads.
Could it be the tape or misalignment of the heads ?
The heads look pretty good actually, just a good clean once in a while and a proper demagnetization is all that is required.
The answer to your poor bass response may lay in the unanswered question I asked a few days ago about the input impedance of your pre-amplifier - for good performance it must be at least 100K or you should replace the output coupling capacitors with larger ones - loads of much less than 47K on the outputs are to be avoided - the CF uses an ECC83 and can't provide the required signal current with good linearity.
Also for a huge improvement in performance connect your record inputs (radio/diode) directly to the record level controls - the existing input amplifier is superfluous in this age of high level digital sources, and in fact will overload quite badly with some cd players and dacs.
The answer to your poor bass response may lay in the unanswered question I asked a few days ago about the input impedance of your pre-amplifier - for good performance it must be at least 100K or you should replace the output coupling capacitors with larger ones - loads of much less than 47K on the outputs are to be avoided - the CF uses an ECC83 and can't provide the required signal current with good linearity.
Also for a huge improvement in performance connect your record inputs (radio/diode) directly to the record level controls - the existing input amplifier is superfluous in this age of high level digital sources, and in fact will overload quite badly with some cd players and dacs.
No, misalignment mainly effects the highs.
First check it if the bass loss is in both channels.
If is in both, than it is most likely impedance miss match to your amp. If it is only in one of the channels, than it is a fault in the playback amplifier. It could be a defective coupling capacitor ,or a dried out cathode by pass electrolyte. In a old machine like yours, all the electrolytes are good candidates for replacement.
First check it if the bass loss is in both channels.
If is in both, than it is most likely impedance miss match to your amp. If it is only in one of the channels, than it is a fault in the playback amplifier. It could be a defective coupling capacitor ,or a dried out cathode by pass electrolyte. In a old machine like yours, all the electrolytes are good candidates for replacement.
You are a lucky person, I never seen one in real life.
I see on the playback amps diagram 3 film capacitors in the signal path and one electrolyte (C41/50) in the first tube cathode circuit.
The film caps probably OK, but the two electrolytes possibly are dry. Also there are some correction switching for the two speeds (not related to the bass loss) , one switch is serving the playback head with an extra capacitance for the lower speed. When you replaced your PB head, I guess you had to change the value of those caps.
I see on the playback amps diagram 3 film capacitors in the signal path and one electrolyte (C41/50) in the first tube cathode circuit.
The film caps probably OK, but the two electrolytes possibly are dry. Also there are some correction switching for the two speeds (not related to the bass loss) , one switch is serving the playback head with an extra capacitance for the lower speed. When you replaced your PB head, I guess you had to change the value of those caps.
kevinkr said:
How strange that an external device would affect the perceived bass response of the unit. You are right none the less
It is hooked up to a Mackie 1402 vlz. I had it on the tape inputs before and have now swapped it to a couple of line inputs. Now the bass is pretty much equal to the source.
I ajusted the bias of the recording circuit and even with a pretty worn tape it sounds very decent. I'm sure that with a clean, demagnetised head and some good tape this will sound brilliant. It certainly makes digital recordings sound more glued and cohesive.
Where do you get quality tape ? What brand and from where ?
Thanks for helping
I use vintage BASF purchased mostly on eBay, RMGI in Holland currently produces a very near equivalent based on the original BASF LPR35 formulation, so I recommend looking for a local supplier.
Worst case you can get it here, but re-exporting it seems rather convoluted to say the least: http://usrecordingmedia-store.stores.yahoo.net/opreelrectap.html
Worst case you can get it here, but re-exporting it seems rather convoluted to say the least: http://usrecordingmedia-store.stores.yahoo.net/opreelrectap.html
Pew..
So, finaly i have replaced my PSU on the G36. Lots of trouble and moving from an appartment to a house in the mittle of it all has left me sweeting.
I think in the whole the machine is back in working order now. Ofcourse all of my tapes has been packed in to some box and moved ( I´m still living in the appartment untill the 1 of april ) so i can´t do a run test before somewhere in april 
, but everything seems to work... ( and no odd smoke or poppin fuses in either machine or building mains ). I have taken some photos that i will upload as soon as i have figured out how , and try to explain what i did. The whole Mains transformer has been replaced with a "new"- ( Old part), and the three rectifiers replaced with diode bridges and resistors, making sure the 230V here in DK got changed corectly. I think that when i get settled in the new place, i will try and go through the whole machine and check up on everything... but a working machine is allright for now I thank you all for your help in here 
So, finaly i have replaced my PSU on the G36. Lots of trouble and moving from an appartment to a house in the mittle of it all has left me sweeting.
I think in the whole the machine is back in working order now. Ofcourse all of my tapes has been packed in to some box and moved ( I´m still living in the appartment untill the 1 of april ) so i can´t do a run test before somewhere in april , but everything seems to work... ( and no odd smoke or poppin fuses in either machine or building mains ). I have taken some photos that i will upload as soon as i have figured out how , and try to explain what i did. The whole Mains transformer has been replaced with a "new"- ( Old part), and the three rectifiers replaced with diode bridges and resistors, making sure the 230V here in DK got changed corectly. I think that when i get settled in the new place, i will try and go through the whole machine and check up on everything... but a working machine is allright for now I thank you all for your help in here Hi.
I got one of these a while back on ebay. I love it. Seems I got lucky. Mine is immaculate. Like a time warp back to 1967. I have all the original paper work. Even the label denoting the model is still on the handle.
I have a little knowledge about valve amps etc and have fixed some other gear but my G36 just seems perfect as is. Probably it could do with some work being so old. I just love the tone of this machine.
Some eye candy:
I got one of these a while back on ebay. I love it. Seems I got lucky. Mine is immaculate. Like a time warp back to 1967. I have all the original paper work. Even the label denoting the model is still on the handle.
I have a little knowledge about valve amps etc and have fixed some other gear but my G36 just seems perfect as is. Probably it could do with some work being so old. I just love the tone of this machine.
Some eye candy:
An externally hosted image should be here but it was not working when we last tested it.
I really like mine, and like yours it is mostly original with a few changes to make it compatible with my high output level digital sources as well as the Nortronics head I installed. It's quite good even by today's standards. I have all of the original manuals and paper work for mine as well. (Or did) I am actually only the second owner. (Amazing after 40yrs)
Mine is a MKIII with the electronic tape path sensor, what version is yours?
Mine is a MKIII with the electronic tape path sensor, what version is yours?
I'm not actually sure what Mark mine is. It has the electronic tape sensor. I had assumed it was later so mark III. When I saw that ebay add (linked to here) I couldn't believe it. Do those earlier ones go for more money? Not that I ever want to sell it.
Mine is in incredibly good condition. The ebay add was very badly done but I could see enough to know it was OK. It turned out even better than OK. Even the box and lid are very nice. There was an issue with the tape counter but I fixed it.
One thing I would love would be if you could run things through the mic preamps without going to tape but I see no way of doing this. I assume it is not possible.
I know you can do stuff to these, biasing etc but my prime purpose for this is to get a valve/tape sound effect rather than highest possible fidelity. I've just left it the way it is. Seems to sound superb to my ears without doing anything.
What is the best tape to use on these machines or is this purely subjective or dependent on how you bias things? I understand some about valve gear but not so much about tape.
The tone of this thing has actually ruined my recording a bit because stuff sent through my computer set up loses tone. I have a good sound interface but nothing sounds as good as this G36.
Mine is in incredibly good condition. The ebay add was very badly done but I could see enough to know it was OK. It turned out even better than OK. Even the box and lid are very nice. There was an issue with the tape counter but I fixed it.
One thing I would love would be if you could run things through the mic preamps without going to tape but I see no way of doing this. I assume it is not possible.
I know you can do stuff to these, biasing etc but my prime purpose for this is to get a valve/tape sound effect rather than highest possible fidelity. I've just left it the way it is. Seems to sound superb to my ears without doing anything.
What is the best tape to use on these machines or is this purely subjective or dependent on how you bias things? I understand some about valve gear but not so much about tape.
The tone of this thing has actually ruined my recording a bit because stuff sent through my computer set up loses tone. I have a good sound interface but nothing sounds as good as this G36.
To tell you the truth I've even become a bit nervous to even use the thing given the condition. Maybe a beaten up one would make me less precious about it. The heads look like they've never seen tape before. I'm making the assumption it's 100% original. I even have the guarantee card that was never sent off. I have one piece of paper with frequency readout from one service it had (probably a very long time ago). I think it had one owner before the person who sold it on ebay. It came from the Czech Republic.
I'd say these are bargains even if you have to do some work. Maybe a really nice one could cost a lot but fixing one up is definitely worth it if you can do it.
I have a valve hifi amp here and the G36 through that is mind blowing. It really makes you wonder about digital gear. Sure, it's great what you can do with computers now especially in combination with this old gear. Digital is a necessary evil for sound production but the sound is lacking character.
I'd say these are bargains even if you have to do some work. Maybe a really nice one could cost a lot but fixing one up is definitely worth it if you can do it.
I have a valve hifi amp here and the G36 through that is mind blowing. It really makes you wonder about digital gear. Sure, it's great what you can do with computers now especially in combination with this old gear. Digital is a necessary evil for sound production but the sound is lacking character.
efflux said:
I still listen to a lot of analog - mostly LP, some tape and FM. (not necessarily of analog origin unfortunately.) In the digital domain I try to purchase SACDs whenever possible, these I play on my heavily modified Sony SCD-777ES.
IMNSHO there probably has not been much real improvement in sound quality at the high end of the market for at least 4 decades. My system is built almost entirely around hardware quite similar to much of what was available in the mid to late 1960s.. All DIY I could not afford to purchase comparable performance ready made.
I would just use and enjoy that deck, and be glad that it was well cared for in prior years, they are not nearly as popular as they once were at least over here. Parts are readily available in USA for these machines, and they are not too expensive to maintain. The primary objection to them is that they are a bit rough on tape which is now stratospherically expensive.
There aren't too many choices for modern recording tape, currently to my knowledge the only producer is RMGi which is based in the Netherlands and makes versions of the old BASF LPR 35, amongst others. (I use vintage BASF LPR 35 and Professional, both give very good results with this deck.) Quantegy teases us from time to time with claims that they are getting back into the business, but under the current economic malaise I would be surprised if they did.
kevinkr said:
I agree with this. Even more recent gear like analog synths or hardware samplers such as EMUs are still far superior to anything you get on computers.
I tried Emtec SM 468 tape but the deck had some old Scotch (forgot the exact type) that came with it which sounded nice. This tape was old and unusable though - too worn and damaged but it saturated very nicely. The Emtec doesn't have that cool saturation. It gets more nasty when it saturates.
I suppose the type of tape will also depend on what you use the deck for. I might try mastering to it.
Depending on the input impedance of the device you are connecting your ReVox to all you may need to do is replace the output coupling caps with larger capacitance values. This should be ok if the input impedance is 47K or greater.
In the case where you are talking about 10K then your simplest recourse is a unity gain buffer using either an op-amp or a tube based cathode follower using something like a 5687. One other possibility would be to revise the CF in the ReVox's playback amplifier to use a 12AT7A and run that at a few mA higher than the stock 12AX7A in order to get the drive for low impedance loads. Note that if you do that the extra current has to come from somewhere, and the best place to get it is by deleting the speaker amplifier or the first two stages of the record amplifier. I've done both as I find neither particularly useful in this day and age - and those extra 2 stages ahead of the record level pots clip like crazy with modern digital sources. In addition the additional circuitry reduces transparency and is completely unnecessary with any modern source unless you plan to use dynamic mics with this deck, which I don't.
Transformers aren't really on for this application because the required impedances are high enough that the use of most affordable transformers will result in a loss of transparency, both leakage inductance and stray capacitance are major issues at this impedance. (Reflecting a 100K load impedance to the deck is non-trivial at these signal levels.)
In the case where you are talking about 10K then your simplest recourse is a unity gain buffer using either an op-amp or a tube based cathode follower using something like a 5687. One other possibility would be to revise the CF in the ReVox's playback amplifier to use a 12AT7A and run that at a few mA higher than the stock 12AX7A in order to get the drive for low impedance loads. Note that if you do that the extra current has to come from somewhere, and the best place to get it is by deleting the speaker amplifier or the first two stages of the record amplifier. I've done both as I find neither particularly useful in this day and age - and those extra 2 stages ahead of the record level pots clip like crazy with modern digital sources. In addition the additional circuitry reduces transparency and is completely unnecessary with any modern source unless you plan to use dynamic mics with this deck, which I don't.
Transformers aren't really on for this application because the required impedances are high enough that the use of most affordable transformers will result in a loss of transparency, both leakage inductance and stray capacitance are major issues at this impedance. (Reflecting a 100K load impedance to the deck is non-trivial at these signal levels.)
Hi, I am also in throes of restoring a G36 and just stumbled on this thread - very interesting. I am only 2nd owner. The machine had a hard life doing the clubs in UK in the seventies, and has mostly been in storage since. It had replacemnt heads fitted in 1973. I found some minor pitting on the heads but not actually in the tape contact zone. Worse was some pitting on the capstan shaft. I bought a new shaft from Jack at JMT and fitted it.
However now I seem to have excessive end play - can anyone tell me what this is supposed to be, and is one supposed to shim it out? The manual doesnt go into any detail.
A further question I have is regards grounding. I was surprised to find the G36 is just like the B77 and has no chassis ground connection. It gets an earth reference when a RCA cable is attached to an amplifier, but what happens when one is recording, with no output connected? The B77 doesnt worry me too much (meets the Euro C standard I guess) but not sure I am so happy about fully floating HT valve gear. Is one supposed to attach a ground in this situation? I dont see anything in the manual - yet the G36 is obviouosly intended to be portable.
Thanks for any advice.
Martin
However now I seem to have excessive end play - can anyone tell me what this is supposed to be, and is one supposed to shim it out? The manual doesnt go into any detail.
A further question I have is regards grounding. I was surprised to find the G36 is just like the B77 and has no chassis ground connection. It gets an earth reference when a RCA cable is attached to an amplifier, but what happens when one is recording, with no output connected? The B77 doesnt worry me too much (meets the Euro C standard I guess) but not sure I am so happy about fully floating HT valve gear. Is one supposed to attach a ground in this situation? I dont see anything in the manual - yet the G36 is obviouosly intended to be portable.
Thanks for any advice.
Martin
Hi kevinkr
Unfortunatelly I do not have such a deck.
But gaining from my experience in restoring old (european) radios manufactured from 1940 to 1970, I would advice you to replace all the paper capacitors (if they are any in your deck).
They are affected by moisture and their value becomes 2X to 10X their nominal value.
Ceramics (tubulars) are more robust but I have encountered two cases where these capacitors failed . And they fail short.
If they are connected to ground at one end, they develop a short (fire hazard).
Electrolytics are the usual suspects, they dry out, especially when they are close to heat source (e.g. tubes).
Old tubes most often operate well.
Old, good equipment deserve - an internal at least - restoring.
Try hard not to modify them.
They belong to another era.
Regards
George