It is currently Mon Mar 16, 2020 4:08 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 26 posts ]  Go to page Previous  1, 2
Go to page Previous  1, 2
Author Message
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Mon May 30, 2016 11:43 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
I've never heard the Stephens True Sonic Speaker so I'll rely on your assessment once it's duly broken in. The previous Sheffield speaker sounded brittle and fizzy to my ears though one of my clients preferred it. The other opted for a vintage P15N and I was fortunate enough to locate a 4-ohm version on Ebay. That amp sounded marvelous once we swapped speakers.

Give us a sonic report in a couple of weeks.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Mon May 30, 2016 12:02 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Fri Nov 09, 2007 7:46 am
Posts: 1019
Location: State of Confusion
Will do.
regarding the P15N, don't you mean a 16 ohm version rather than a 4 ohm. The PVDB uses 16 ohms or 8 ohms for internal + external. I have always wondered why Peavey chose OTs for 16/8 (on all their classic series amps) and Fender 8/4 for most of their modern amps??????

_________________
The quintessential sound of 60/70's R&R:
Fender Tube Amps
Gibson Guitars


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Mon May 30, 2016 12:55 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
Ah, yes......sixteen ohms.

:oops:

(apologies for my second-rate stenographer)

:mrgreen:

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Tue May 31, 2016 8:17 am
Offline
Professional Musician
Professional Musician

Joined: Thu Aug 07, 2014 3:25 pm
Posts: 1023
Speaking to the original question, one important factor that hasn't been brought up is the hum cancellation resulting from a perfectly match set of output tubes.
There is seldom enough filtering to completely smooth the DC supply. Often there is significant ripple on the output transformer supply. The opposing poles of the primaries effectively cancels this ripple from reaching the secondary.
This is probably why Fenders went to bias balance rather than control in the SF redesigns. Its more important to cancel perfectly and have a quiet amp. A humming amp tended to stay on the showroom floor. The factory could install the right range tubes for proper tube bias, but killing that last little bit of hum required a balance control.
So yes, to say the same thing in three words. Match your tubes.


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Tue May 31, 2016 8:58 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Fri Nov 09, 2007 7:46 am
Posts: 1019
Location: State of Confusion
TimsAudio wrote:
Speaking to the original question, one important factor that hasn't been brought up is the hum cancellation resulting from a perfectly match set of output tubes.
There is seldom enough filtering to completely smooth the DC supply. Often there is significant ripple on the output transformer supply. The opposing poles of the primaries effectively cancels this ripple from reaching the secondary.
This is probably why Fenders went to bias balance rather than control in the SF redesigns. Its more important to cancel perfectly and have a quiet amp. A humming amp tended to stay on the showroom floor. The factory could install the right range tubes for proper tube bias, but killing that last little bit of hum required a balance control.
So yes, to say the same thing in three words. Match your tubes.

Yes, I didn't mention that possibility when I gave the results of my 'search' on the topic. So add the hum factor to "if the amp does not produce unwanted distortion and the tubes do not redplate". Mine did not hum either, so to say "match your tubes" still may not be necessary as many others contend. My sample of 1 would suggest that possibility. :| Then again, who's to say the matched pair I put in with the other two wasn't a close enough match? But that's the point, isn't it?

_________________
The quintessential sound of 60/70's R&R:
Fender Tube Amps
Gibson Guitars


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Fri Oct 21, 2016 9:28 am
Offline
Professional Musician
Professional Musician
User avatar

Joined: Fri Nov 09, 2007 7:46 am
Posts: 1019
Location: State of Confusion
Retroverbial wrote:
I've never heard the Stephens True Sonic Speaker so I'll rely on your assessment once it's duly broken in. The previous Sheffield speaker sounded brittle and fizzy to my ears though one of my clients preferred it. The other opted for a vintage P15N and I was fortunate enough to locate a 4-ohm version on Ebay. That amp sounded marvelous once we swapped speakers.

Give us a sonic report in a couple of weeks.

Arjay

Well, it's been certainly more than a couple of weeks, but the speaker is surely well broken-in by now. I'm far from an expert on speaker evaluation (one vs. another), especially on 15" speakers....I only have one other, an Eminence Legend 1518.

I can report that I'm very pleased with the Peavey Delta Blues' sound and have no intention on looking for a replacement speaker, so to me, the speaker is certainly satisfactory.

_________________
The quintessential sound of 60/70's R&R:
Fender Tube Amps
Gibson Guitars


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Wed Feb 01, 2017 3:07 pm
Offline
Hobbyist
Hobbyist

Joined: Thu Aug 30, 2012 12:29 pm
Posts: 3
IM4Tone wrote:
Just bought a Peavey Delta Blues II 115. it sounded pretty good except the "drive" was a bit harsh, and some static sounds when pushed hard. I was considering some options for different preamp tubes to smooth out the "drive", so I decided to look at what was involved in accessing the tubes by removing the cage.

Much to my surprise, the V5 power tube had a white powdery substance where the others had the black/silver mirror-like look. When I touched the V5 tube, an EL84 (power off and cooled) the bottle fell off. Apparently a circumferential crack existed in the glass. I'm amazed the sound wasn't that bad!

Image

I damaged the innards of the tube removing it from the socket which didn't matter since it wasn't any good anyway. I can only suspect that the glass bottle was faulty????

So as I contemplated what to do, I did a lot of searches about mismatched power tubes and found quite a few (seemingly knowledgable...but how can one be sure?) people saying that there is no damage to be done if the amp does not produce unwanted distortion and the tubes do not redplate. In fact a couple of sources even claimed there could be an improvement of desirable harmonics. The claims were that it takes significant mismatch to cause one of the tubes to wear faster than another???

I had a matched pair, not quad (which is in the PVDB), so I put the two in V5 and V6 (the two innermost power tubes). Also, I do not have the wherewithal to bias a fixed biased amp. Also read on the websites of a couple of major tube suppliers, that it should be OK to do so with the same brand (JJ) and especially with EL 84's.

Gave it a quick test and all seems well so far....more testing today.

Am I flirting with disaster or is it a case of "no red plating and good sound" means it's fine? Appreciate any feedback, and sorry for the long post.


Confused about the above highlighted quote n red.
The Peavey Delta Blues is a 'non-adjustable' "fixed bias" amp, from what i see.
How or why would you, or can you, go about doing a bias on this type of amp ?
Thanks for any clarification...


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Wed Feb 01, 2017 5:11 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
Prolly need to play with R64 (near BIAS label in PSU) value. That 22mfd/25VDC bias filter cap, C44, is cutting it close. Esp during cold starts. I'd replace it with a 25mfd/50VDC or 50/50 lytic.

http://bmamps.com/Schematics/Peavey/Pea ... ematic.pdf

BTW... the damage to that EL84 is common amongst newly made 9-pin output tube amps. The cinch tangs are so tight in these new issued Chinese made sockets, that tube insertion and removal or even heat expansion & cooling contractions often cause hairline cracks and loss of vacuum. A good contact cleaner/lubricant may help. Esp to prevent damage when inserting or removing tubes. Caig Deoxit GN-100 is great to lube clean contacts. Just a little on the tube pins and socket receptors


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Thu Feb 02, 2017 2:27 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
BMW2002Ti wrote:
A good contact cleaner/lubricant may help. Esp to prevent damage when inserting or removing tubes. Caig Deoxit GN-100 is great to lube clean contacts. Just a little on the tube pins and socket receptors


As well, maximum caution should be exercised when seating or unseating tubes (any tubes). A gentle oscillating motion is preferable to the strong-arm tactic of simply yanking them free like King Kong.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Fri Feb 03, 2017 9:38 am
Offline
Professional Musician
Professional Musician

Joined: Wed Dec 15, 2010 7:06 am
Posts: 1662
Retroverbial wrote:
BMW2002Ti wrote:
A good contact cleaner/lubricant may help. Esp to prevent damage when inserting or removing tubes. Caig Deoxit GN-100 is great to lube clean contacts. Just a little on the tube pins and socket receptors


As well, maximum caution should be exercised when seating or unseating tubes (any tubes). A gentle oscillating motion is preferable to the strong-arm tactic of simply yanking them free like King Kong.

Arjay


a big +1 on the oscillating motion, and yanking them free like King Kong LMAO :lol:
mud


Top
Profile
Post subject: Re: Unmatched 6L6GC's in push pull
Posted: Fri Feb 03, 2017 10:46 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
mud wrote:
...and yanking them free like King Kong LMAO


Techs like that should seek an alternate career......

Like neurosurgery or watch repair.

:lol:

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 26 posts ]  Go to page Previous  1, 2
Go to page Previous  1, 2

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: