Well......... If the hiss doesn't bother you then its normal. If it does, then it is not normal. But, I would say that most folks (including me) do not usually care for it and do our best to get rid of.
Marantz, McIntosh, Tannoy and Thorens find of a lifetime
- Thread starter mikemurph6
- Start date
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Justin Credible
Some "hiss" is to be expected, especially with that many carbon composition resistors in the gear. Congratulations regarding your find.
doctor fuse
Super Member
Wow...just, wow. But very very happy for you.
Thank you all for your reply’s, I think the hiss is abnormal just based on reading back to other threads about the preamp on these forums. I can hear the hiss from 10 feet away even with volume down to about one quarter. The hiss is very loud when volume is over half (however if I played music at that level it would be deafening, most of the time I am listening at about quarter volume). Would it be worth switching the tube locations to see if that makes a difference before I buy all new tubes? Also any recommendations on what tubes to purchase? Sorry for all the questions, I appreciate everyone’s help!
Have forgotten............ is it one channel or both? If both, then swapping tubes will tell you little.
Were me, I would purchase a new set in any event. If one does go completely then you're down until the new one arrives. At least one of each flavor your gear uses. However, decent small tubes are relatively inexpensive (each of us has their own threshold on cost). I've had good luck with the new Tung-Sol and others say the new Mullard or EH or JJ. Buy from one our 'known-good' sellers like Jim McShane or the Tube Store (there are others). Tell them what preamp you have and let them suggest a tube-set for you. McShane and Jon at the Tube Store are both very knowledgeable and won't steer you wrong. And both respond to e-mail.
Interesting that the Model 7 was called a "console preamp". Must have been designed specifically for the console, which is great. Whatever it takes, it is really a great piece to get going well. One step at a time, but a Dual 1219 would be perfect in there (if it fits).
Were me, I would purchase a new set in any event. If one does go completely then you're down until the new one arrives. At least one of each flavor your gear uses. However, decent small tubes are relatively inexpensive (each of us has their own threshold on cost). I've had good luck with the new Tung-Sol and others say the new Mullard or EH or JJ. Buy from one our 'known-good' sellers like Jim McShane or the Tube Store (there are others). Tell them what preamp you have and let them suggest a tube-set for you. McShane and Jon at the Tube Store are both very knowledgeable and won't steer you wrong. And both respond to e-mail.
Interesting that the Model 7 was called a "console preamp". Must have been designed specifically for the console, which is great. Whatever it takes, it is really a great piece to get going well. One step at a time, but a Dual 1219 would be perfect in there (if it fits).
both channels have the same hiss. It also doesn’t change when I remove all inputs.
Based on that, I would guess it is a power supply problem since it is common to both channels and tubes tested good. Did your tech replace the original selenium rectifiers? Recap the power supply? Those are the two first places I would go if the tubes are good.
It looks like V1, V2 & V3 are the line stage with the other tubes being the phono stage. You might try swapping V6 with V4 or V5 and see if that changes anything.
It looks like V1, V2 & V3 are the line stage with the other tubes being the phono stage. You might try swapping V6 with V4 or V5 and see if that changes anything.
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yes my tech replaced the selenium rectifier and recapped anything out of spec. Doesn’t specifically say he recapped the power supply but just that all caps that needed replacing were replaced.
You could try the tube swap above as V6 is common to both channels. Since the Model 7 uses all 12AX7 you only need one good one to test by rotating thru each position. Though the common problem would lead one to believe it is the power supply.
i have a 7C and 8B both restored and ive never heard a hiss even when pairing with my Fortes which are very sensitive so i wouldnt think it is normal to hiss. i didnt hear one before they were restored either. i agree with swapping or changing the tubes and see if anything changes.
Dandy
Addicted Member
Can you begin to isolate where the hiss is, but testing the power amp separately, e.g. with a passive preamp (pot in a box), or even a SS preamp? I've never experienced Marantz tube gear, but I would guess the hiss is coming from the preamp. Otherwise, I would suspect older carbon comp resistors, even if they measure correctly. I doubt if replacing the tubes will change anything, but I once had problems with a faulty 12AX7.
Congratulations on your find and good wishes for its full restoration from a fellow TD135 owner.
Congratulations on your find and good wishes for its full restoration from a fellow TD135 owner.
ILikeRecords
New Member
Cool to read that finds like this are still out there. Great one for sure!
Great thanks everyone for the advice, I’ll try using another preamp to see if the problem is the power amp. I’ll also try a different pair of speakers. Then if the problem still seems to be the preamp I’ll swap v4 or v5 with v6 and see if that makes a difference. I’m working long hours for the next couple days but I’ll report back Tuesday or Wednesday! Thanks again!
So using a modern Denon receiver as a preamp I did notice a lower amount of hiss however the gain was significantly lower than the 7 so it was difficult to make an accurate comparison. However when both preamps were turned down to 0 the hiss was definitely louder on the 7.
I also switched to some 8ohm Advent/1s which didn’t makes huge difference in the hiss.
Lastly I swapped around the tube positions. All the tubes are original Tele’s except V3 which is an amperex bugle boy ECC83. All of the tubes made just about the same hiss however most of the tubes (v1-4) when when switched into position V6 made a burst of 10 soft taps which were very quick (300 bpm or so), these bursts occurred about once a minute or so. They seemed to get less frequent the longer the system was running. I do have a video of those clicks and the hiss if that would help.
I’m kind of at a loss and switched the tubes back to their original position. I reached out to my tech who said the hiss is likely normal but with the preamp set at a volume of 0 and no inputs even plugged in I shouldn’t hear a hiss from several feet away from the speakers, correct?
Dswankey
Lunatic Member
What sources are connected to the pre? CDP, tuner, TT
Do you have any other electrical devices near the unit possibly picking up magnetic fields.
This might be of useful info for you (No affiliation)
https://www.psaudio.com/ps_how/how-to-find-and-fix-hum-extended/
Thank you for that link, the hiss occurs even with no inputs attached to the preamp. Also I just tested the system with my TV and soundbar which are above the console on the wall and didn’t notice any change, but thanks for that thought!
I just made another video and noticed that when I put the high frequency filter on 5kc on the preamp that the hiss is noticeably reduced but not eliminated. I don’t know if that helps narrow things down.
I reached out to Jim McShane and plan on ordering a new set of tubes to see if that helps.
Dswankey
Lunatic Member
My tech has a piece of equipment that can trace the hum, my guess is it's a relatively standard piece of equipment for audio techs maybe check with your tech.
Do you have a lot wiring, plugs, cable etc all grouped together near the amps?
FWIW I'm not technical but in the past when I had hum and or hiss issues with tube gear these were the kind of questions my tech would ask.
Do you have a lot wiring, plugs, cable etc all grouped together near the amps?
FWIW I'm not technical but in the past when I had hum and or hiss issues with tube gear these were the kind of questions my tech would ask.
So somehow this gift keeps on giving. I had left my number at the store because they said the tubes maybe lying around somewhere for the 8B and that they happen to find them they would give me a call. Today I just picked up the tubes (missing one of the RCA 6CG7) AND all of the original receipts, manuals, warranty cards etc. for each component (other than the Tannoy’s). Additionally he must have owned a high end Fisher stereo console and those documents are included as well as some other random things.
I’ll upload some pictures but I’m especially excited to read through all the Marantz literature.
I’ll upload some pictures but I’m especially excited to read through all the Marantz literature.
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