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Post by mikeyb on May 20, 2020 14:01:22 GMT
My Herron Audio VTSP-2a Pre Amp with Electro Harmonix 6922 valves ( 6 in total ) was starting to sound a little hissy on one side. So having read up on EH 6922s I found out that some can go a bit noisy after 200 hours or so. These were fitted by the seller not long before I bought the amp so I thought I'd be as well replacing them and rather than trying to work out which one of the 6 was noisy I replaced them all. Ok I could have swapped them 1 by 1 but you need to unplug the power for 30 minutes before swapping valves and I couldn't be bothered potentially doing that 6 times 🤔 So in went 6 matched Matsushita 7DJ8s from Watford Valves. Result - no more hiss 😊 Ironically I bought the 7DJ8s a day before some EH 6922s came up for sale on the Art of Sound Forum, typical!      |
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Post by antonio on May 20, 2020 14:04:13 GMT
Always good when you can solve the problem yourself.
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Post by mikeyb on May 20, 2020 14:06:34 GMT
Always good when you can solve the problem yourself. Definitely, I was hopeful when I switched it on and wouldn't have been surprised it was actually my power amp causing the issue lol. |
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Post by jandl100 on May 20, 2020 14:27:15 GMT
Very nice pre, that. I really enjoyed the time I had with mine.
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Post by firebottle on May 20, 2020 15:40:43 GMT
Is it meant to have 6922's (6.3V heaters) or 7DJ8 (7V heaters)? What does the manual say?
Also though marked 7DJ8/PCC88 a true PCC88 has 7.6V heaters.
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Post by mikeyb on May 20, 2020 17:39:11 GMT
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Post by jandl100 on May 21, 2020 7:53:47 GMT
I rolled the valves a fair bit in mine, and after a while I was on the point of selling the pre as I'd got a bit bored with the sound - but I came across the advice to stay with EH. Back in they went and KERZAM the magic came back, too. I kept it for a good 6 months longer. In my opinion the pre has defo been optimised for EH. YMMV  |
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Post by mikeyb on May 25, 2020 11:09:26 GMT
Well my joy was short lived, it started hissing on the left channel again shortly after I posted that it was cured.
So I swapped the pre out and replaced it with a Marantz av amp for pre duties. Totally silent so it's definitely the Herron pre that's the issue.
So, this morning before work I thought I'd swap the valves from one side to the other to see if the hiss would switch from left channel to the right one, now bear in mind these are brand new matched valves so should be perfect. So swap done 3 from one side of the amp to the other, assuming that one side is left channel and the other is right channel.
Guess what the be hiss swapped over too, hissing loudly on the right as it did on the left before I swapped them over???
What the heck, so tonight what I plan to do is swap each valve one by one as I have a spare to match the 7DJ8s that are currently in it.
Issue with that is that you're supposed to power down the pre amp for 30 minutes before swapping valves over, so it could be a long night.
But how the heck could this happen with the almost new EH6922s that it came fitted with AND the brand new 7DJ8s I've just fitted?
I did suspect that it might be a transistor causing the hiss as I've read that can happen, but surely the fact that the hiss swapped sides this morning would rule a transistor out?
Stuck at work just now and stumped would be a fair assessment ☹️
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Post by antonio on May 25, 2020 11:15:54 GMT
Swapping the valves over was a good plan, and I like the idea of using a spare and swapping, so let's hope you find the problem valve tonight.
"How the heck can this happen with new valves" - You could say the same about anything electrical that doesn't work perfectly when purchased new.
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Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,399
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Post by Bigman80 on May 25, 2020 12:17:21 GMT
I bought 4 Tesla valves. All NOS from the same seller
2 were perfect .. 2 were Sh#t
That's the name of the game with valves...its a minefield
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Post by mikeyb on May 25, 2020 13:00:45 GMT
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Post by firebottle on May 25, 2020 13:52:51 GMT
The 30 minute advice will be so that all the stored energy (high voltage - ouch) has had time to fall to zero. If you don't touch anything other than the valve you should be able to swap over in a shorter time. Advice given for use only when accompanied by common sense  |
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Post by jandl100 on May 25, 2020 14:40:51 GMT
So that rules out Mikey, then. That's a bummer with the valves - that's the trouble with having 6 of the buggers, reasonable chance at least one will be duff. I had to play the same valve swap game when I did some valve rolling with the Herron. Grrrr. Drove me crazy, the duff one was the 5th. Typical. I just let them cool off for 2 or 3 minutes between each swap and wore a cotton glove. |
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Post by mikeyb on May 25, 2020 16:30:29 GMT
So that rules out Mikey, then. That's a bummer with the valves - that's the trouble with having 6 of the buggers, reasonable chance at least one will be duff. I had to play the same valve swap game when I did some valve rolling with the Herron. Grrrr. Drove me crazy, the duff one was the 5th. Typical. I just let them cool off for 2 or 3 minutes between each swap and wore a cotton glove. Oi ! I resemble that remark 😂 I'll try and work out which side is left and start there, bound to be wrong lol |
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Post by mikeyb on May 26, 2020 6:51:12 GMT
Didn't get time to look at the valves last night.
I'm just thinking though, what are the chances of swapping 6 valves with brand new tested, matched ones and STILL getting a faulty one installed on the same side as the hiss from the old ones?
I'm not convinced it's a valve fault.
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Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,399
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Post by Bigman80 on May 26, 2020 8:01:45 GMT
Didn't get time to look at the valves last night. I'm just thinking though, what are the chances of swapping 6 valves with brand new tested, matched ones and STILL getting a faulty one installed on the same side as the hiss from the old ones? I'm not convinced it's a valve fault. It swapped sides when you swapped the valves. Have you cleaned the pins? May do nothing or something....just dont know |
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Post by mikeyb on May 26, 2020 8:47:56 GMT
Didn't get time to look at the valves last night. I'm just thinking though, what are the chances of swapping 6 valves with brand new tested, matched ones and STILL getting a faulty one installed on the same side as the hiss from the old ones? I'm not convinced it's a valve fault. It swapped sides when you swapped the valves. Have you cleaned the pins? May do nothing or something....just dont know That's true, hopefully get a look tonight |
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Post by jandl100 on May 27, 2020 9:07:11 GMT
the fault did swap sides when you swapped them over, makes it seem likely to be a valve fault
-- oops, Oli's reply saying the same was on the next page and I didn't notice
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Post by mikeyb on May 27, 2020 9:13:16 GMT
the fault did swap sides when you swapped them over, makes it seem likely to be a valve fault -- oops, Oli's reply saying the same was on the next page and I didn't notice Yeah, I must be getting auld as I'd forgotten I'd said that doh! Well would you believe it, first bloomin' valve I swapped last night was the culprit, free replacement on its way from Watford Valves so that's great customer service from them. I tried that valve first as it had a different build number to all the others and my hunch was right, problem solved 😊 Jeez l soon be able to call myself a technical engineer or something and charge the appropriate consultation fees, by appointment only of course 😂😂😂 |
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Post by antonio on May 27, 2020 9:48:47 GMT
Great news and a big plus to Watford Valves.
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Bigman80
Grandmaster
The HiFi Bear/Audioaddicts/Bigbottle Owner
Posts: 16,399
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Post by Bigman80 on May 27, 2020 11:01:59 GMT
the fault did swap sides when you swapped them over, makes it seem likely to be a valve fault -- oops, Oli's reply saying the same was on the next page and I didn't notice Yeah, I must be getting auld as I'd forgotten I'd said that doh! Well would you believe it, first bloomin' valve I swapped last night was the culprit, free replacement on its way from Watford Valves so that's great customer service from them. I tried that valve first as it had a different build number to all the others and my hunch was right, problem solved 😊 Jeez l soon be able to call myself a technical engineer or something and charge the appropriate consultation fees, by appointment only of course 😂😂😂 Fantastic stuff Glad you've found the culprit. Valves are terribly fickle things. |
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Post by mikeyb on May 27, 2020 11:08:43 GMT
Great news and a big plus to Watford Valves. Definitely, bought from them a couple of times now and been good service. |
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Post by mikeyb on May 27, 2020 11:09:10 GMT
Yeah, I must be getting auld as I'd forgotten I'd said that doh! Well would you believe it, first bloomin' valve I swapped last night was the culprit, free replacement on its way from Watford Valves so that's great customer service from them. I tried that valve first as it had a different build number to all the others and my hunch was right, problem solved 😊 Jeez l soon be able to call myself a technical engineer or something and charge the appropriate consultation fees, by appointment only of course 😂😂😂 Fantastic stuff Glad you've found the culprit. Valves are terribly fickle things. Happy Bunny here for sure 😊 |
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