From postmaste–(at)–riodeel.com Sun Nov 1 23:00:01 CST 1998
Article: 136270 of alt.guitar.amps
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From: postmaste–(at)–riodeel.com (Ned Carlson)
Newsgroups: alt.guitar.amps
Subject: Re: Deluxe Reverb-’70/’71 Several Questions Part II
Date: 1 Nov 1998 00:07:01 -0600
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On Sun, 01 Nov 1998 01:55:40 GMT, bogu–(at)–ogus.COM (JJman) wrote:
>2) The SS recifier is not a good idea (too much voltage). How
>about a GZ34? How many more volts will it put out over the stock
>5U4GB?
Not as much as you’d think, maybe 10-15 volts or so, because
a Deluxe Reverb doesn’t pull much current thru the rectifier tube.
See the chart at http://www.triodeel.com/5ar4_p4.gif
> beleive the GZ34 actaully pulls fewer amps from the power
>trans and was stock on the BFDR. I am not a big fan of major sag so I
>may want an option if I need it.
Part of the problem is that NOS GZ34 are expensive. Chinese
ones..which we sell ’cause no one (HEY! Svetlana! Tesla! You
listening?) wants to make new, decent GZ34, are useable but mainly
’cause a Deluxe only draws around 70 ma at idle. (GZ34 are rated
for 250 ma max).
But there’s other, better solutions:
5V4-G/GA: Good US ones aren’t too common, but aren’t too expensive,
either. Sovtek makes one that’s apparently good enough for Matchless.
It has a heater cathode like a 5AR4 & drops less voltage than
5U4. The current draw of a Deluxe is within spec for these tubes.
Used GZ34’s: Good old GZ34 normally outlast the power
tubes by a bunch, but often people replace the GZ34 anyway,
even tho it’s still got lotsa life left, so there’s a few floating
around for much cheaper than new.
CV378/GZ37: Looks like a tall, beefed up version of GZ34.
Sort of halfway between 5U4 and GZ34. They’re rated for
350 ma max, so ought to last eons in a Deluxe. Available
>from us or Angela for about $20, NOS.
Either way you cut it, I’d up the voltage rating of the filter caps
to 500V from 450. Considering normal parts tolerances,
and variation in line voltages, that’s probably a good idea anyway,
but adding another 10 or 15V to the power supply makes it even
more likely the voltage will go over the ratings…you do not want to
blow up your filter capacitors. It ain’t a pretty sight.
While you’re at it, replace that bias supply cap if someone hasn’t
done that already. Cheap insurance.
Then, if you do decide to use one of the lower voltage drop
rectifiers, go back and readjust the bias.
Now, guaranteed, somebody’s gonna say that the voltage
is gonna be too high for a 6V6.Book says so, right?
I say that if you’ve got *good* 6V6-GT or 6V6-GTA,
and make sure the bias is right…25 ma sounds about right, with
435V,that’s derating the plate dissipation by about 20%…OK.
Actually, I’ve tested 6V6-GT’s in amps running
up to 460V…this *may* sound insane, but take a look at some other
similarly sized tubes..like 7591-A, which is rated for 550V,
or 2E26 which is rated for 600V. OK, 7591A IS kind of
an insane tube, anyway.
I’d say stay away from Chinese or Russian 6V6, I doubt they’ll
last long enough for you to get the bias set.
>
>3) Pre-amp tube sheilds-WAZZUP? I’ve read that these rob tone.
Maybe someone was using Dr Stereo’s “Tone Swine Special”,
tone-sink tube shields?
I can’t imagine how this could be true, but perhaps someone could
enlighten me, I mean , if someone can hear it, I believe them,
but I’d sure like to hear why that might be true…after all, I
don’t play a guitar, so obviously I don’t know shit about this
anyway.
I will say, if the reason for this observed effect has to do with
the tube shield retaining heat, then, yes, there may be something to
it. Believe it or not, the military *did* (I bet Lord Valve has seen
some) use heat sinking black tube shields, with little phosphor
bronze accordion thingies to sink heat away from the glass.
I shit you not, they’re called IERC shields, and the military really
*did* do a study that showed that tube life could be measurably
extended by using them. (The military, unfortunately, did not
do any Tone Studies. I guess Col. Tone Hog had been decommisioned)
I suppose one *could* emulate this by painting one’s tube shields
black, then stuffing some aluminum foil in there to increase the
metal to glass contact.
>4) I know how to bias by installing 1 ohm resistors on the
>cathodes but please explain the “transformer shunt method.”
Hook one lead to the transformer center tap, the other to
*one* of the tubes at Pin 3. Turn on the amp, let it get nice & warm,
turn on the standby.Read meter, adjust bias, then turn the POWER
switch off, not the standby (this will let the tubes drain off most of
the B+ while cooling down). Then wait for a minute or two.
Switch the lead to pin 3 of the other 6V6. Turn the standby off,
then turn the power on. Again, let ‘er warm up then hit the standby.
Read the other side. If the tubes are properly matched, the reading
will be within 2 ma of the other side.
>I do have a high quality meter (Fluke 21)
I’ve got an IBM meter made by Fluke, and it never works
for this. (I dunno why. Of course, I don’t play guitar, so I
can’t be expected to know shit about these things)
I use a godawful antique Simpson 260.
(This earns me a honorary Dr Stereo flame)
>and I know to switch the red
>wire to the milliamps prong for this method. I guess all I need to
>know is where to put each connection? ( I am very aware of the lethal
>voltages and where they are.) It will read the actual idle
>current-no?
The plate current. Reading the cathode gives you plate AND
screen current together. The screen accounts for roughly 2 ma.
>ill it show me the total of both power tubes?
No, just the one you are checking.
>6) Tone robbing grid>ground caps. Schem shows 1200pf.
>Mine are .001u (=1000pf close enough). Has anyone ever tried a lower
>value cap to avoid oscillation yet preserve tone? After all isn’t
>this oscillation “ultra sonic” (very high frequency) and wouldn’t a
>lower value cap increase tone while still eliminating
>oscillation?
So far, I don’t recall anyone on this NG relating any
horror stories about what happened when they just snipped
out those grid-resistor bypass caps.
If there are any, I’d like to hear ’em.
>From what I’ve seen, amp manufacturers will do stuff like drop
those caps in, even if only a tiny fraction of the amplifiers
they made had some kind of oscillation problem, even if
it only happened under certain rare conditions, (say , for example, it
only happened with a certain combination of tubes & speakers)
probably because engineers hate getting called on the
carpet for that kind of shit..
I suspect that the problem was Fender buying cheaper output xfmrs..
But OTOH, I have seen Fenders that only oscillated
*without a load*. This is going to be very rare for the average person
to see, because old Fenders have shorting output jacks.
However, here’s a totally unscientific wild ass guess:
Say people were using combo to play cabinets instead,
or people with heads, either way, accidentally left the
speaker end of the cable disconnected..dumb, but it could
happen..and the tubes melted down due to oscillation.
Customers bitch to dealers, dealers bitch to reps, reps
bitch to management, management bitches to engineering.
Engineering stuffs in 1200 pf caps to get ’em all to shut up
& quit bitching.
A Rube Goldberg scenario, but the electronics industry is full of
Rube Goldberg scenarios. Hell, let’s talk about Windows 98..
The problem with the oscillation, is that the easiest ways to detect
it, is seeing it on a ‘scope (which most folks don’t have), or
watching your tube plates turn red as a beet. There may be..
I’m sure there is..audible effects, too, *if* the speaker’s
plugged in when it’s oscillating, and you’re playing thru it.
Ned Carlson Triode Electronics “where da tubes are!”
2225 W Roscoe Chicago, IL, 60618 USA
ph 773-871-7459 fax 773-871-7938
12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun
http://www.triodeel.com
Your Start Page for Tube and Tube Amp info on the net…
http://www.triodeel.com/tlinks.htm
From detritu–(at)–x.netcom.com Sun Nov 1 23:02:31 CST 1998
Article: 136311 of alt.guitar.amps
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From: detritu–(at)–x.netcom.com(Lord Valve)
Newsgroups: alt.guitar.amps
Subject: Re: Deluxe Reverb-’70/’71 Several Questions Part II
Date: 1 Nov 1998 09:49:05 GMT
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In <363bdafb.34341811--(at)--ews1.newscene.com> postmaste–(at)–riodeel.com (Ned
Carlson) writes:
>
>On Sun, 01 Nov 1998 01:55:40 GMT, bogu–(at)–ogus.COM (JJman) wrote:
(snip)
>Part of the problem is that NOS GZ34 are expensive. Chinese
>ones..which we sell ’cause no one (HEY! Svetlana! Tesla! You
>listening?) wants to make new, decent GZ34, are useable but mainly
>’cause a Deluxe only draws around 70 ma at idle. (GZ34 are rated
>for 250 ma max).
>But there’s other, better solutions:
LV: The Chinese aren’t that bad. The Sovteks were better,
but they’re really hard to find now.
>5V4-G/GA: Good US ones aren’t too common, but aren’t too expensive,
>either. Sovtek makes one that’s apparently good enough for Matchless.
>It has a heater cathode like a 5AR4 & drops less voltage than
>5U4. The current draw of a Deluxe is within spec for these tubes.
LV: I’ve used the Sovtek, too. It’s good.
>
>Either way you cut it, I’d up the voltage rating of the filter caps
>to 500V from 450. Considering normal parts tolerances,
>and variation in line voltages, that’s probably a good idea anyway,
>but adding another 10 or 15V to the power supply makes it even
>more likely the voltage will go over the ratings…you do not want to
>blow up your filter capacitors. It ain’t a pretty sight.
>While you’re at it, replace that bias supply cap if someone hasn’t
>done that already. Cheap insurance.
LV: Use a bigger value for the bias cap, at least double
the capacitance of the original. You’d be surprised
how much hum is due to bias ripple. As for voltage,
I’d go for twice whatever the bias is…100V for 50-volt
range, etc.
>
>Then, if you do decide to use one of the lower voltage drop
>rectifiers, go back and readjust the bias.
>
>Now, guaranteed, somebody’s gonna say that the voltage
>is gonna be too high for a 6V6.Book says so, right?
>I say that if you’ve got *good* 6V6-GT or 6V6-GTA,
>and make sure the bias is right…25 ma sounds about right, with
>435V,that’s derating the plate dissipation by about 20%…OK.
>Actually, I’ve tested 6V6-GT’s in amps running
>up to 460V…this *may* sound insane, but take a look at some other
>similarly sized tubes..like 7591-A, which is rated for 550V,
>or 2E26 which is rated for 600V. OK, 7591A IS kind of
>an insane tube, anyway.
>I’d say stay away from Chinese or Russian 6V6, I doubt they’ll
>last long enough for you to get the bias set.
LV: If you use the Chinese 6V6s, wear goggles so you don’t
get any glass in your eyes when they explode. The Sovteks
are only slightly better. ANY 6V6 will benefit from changing
the screen resistor to 1K/5W, however.
>
>>
>>3) Pre-amp tube sheilds-WAZZUP? I’ve read that these rob tone.
>
>Maybe someone was using Dr Stereo’s “Tone Swine Special”,
>tone-sink tube shields?
>
>I can’t imagine how this could be true, but perhaps someone could
>enlighten me, I mean , if someone can hear it, I believe them,
>but I’d sure like to hear why that might be true…after all, I
>don’t play a guitar, so obviously I don’t know shit about this
>anyway.
LV: I read something about capacitance from the shields causing
HF rolloff, but I can’t see how it could be significant
at any frequency within the passband of a typical guitar
rig. Most guitar speakers crap out around 6KHz, and that’s
gotta be way lower than anything a tube shield would dump.
>
>I will say, if the reason for this observed effect has to do with
>the tube shield retaining heat, then, yes, there may be something to
>it. Believe it or not, the military *did* (I bet Lord Valve has seen
>some) use heat sinking black tube shields, with little phosphor
>bronze accordion thingies to sink heat away from the glass.
>I shit you not, they’re called IERC shields, and the military really
>*did* do a study that showed that tube life could be measurably
>extended by using them. (The military, unfortunately, did not
>do any Tone Studies. I guess Col. Tone Hog had been decommisioned)
>I suppose one *could* emulate this by painting one’s tube shields
>black, then stuffing some aluminum foil in there to increase the
>metal to glass contact.
LV: Yeah, I’ve seen those…I have a pile of ’em, in fact. They
are pretty hard to remove if they’ve been on for a long time,
though.
>
>>4) I know how to bias by installing 1 ohm resistors on the
>>cathodes but please explain the “transformer shunt method.”
>
>Hook one lead to the transformer center tap, the other to
>*one* of the tubes at Pin 3. Turn on the amp, let it get nice & warm,
>turn on the standby.Read meter, adjust bias, then turn the POWER
>switch off, not the standby (this will let the tubes drain off most of
>
>the B+ while cooling down). Then wait for a minute or two.
>Switch the lead to pin 3 of the other 6V6. Turn the standby off,
>then turn the power on. Again, let ‘er warm up then hit the standby.
>Read the other side. If the tubes are properly matched, the reading
>will be within 2 ma of the other side.
LV: This is the candy-ass method for newbies. You’d do well to
follow Ned’s advice, since once the meter is connected to
the center-tap, the other probe will become live with the
meter set to a current range. Myself, I enjoy the sparks…
>
>>I do have a high quality meter (Fluke 21)
>
>I’ve got an IBM meter made by Fluke, and it never works
>for this. (I dunno why. Of course, I don’t play guitar, so I
>can’t be expected to know shit about these things)
>I use a godawful antique Simpson 260.
>(This earns me a honorary Dr Stereo flame)
LV: No problems with my Fluke bench meter. 8050A, I believe
it is.
>
>>and I know to switch the red
>>wire to the milliamps prong for this method. I guess all I need to
>>know is where to put each connection? ( I am very aware of the lethal
>>voltages and where they are.) It will read the actual idle
>>current-no?
>
>The plate current. Reading the cathode gives you plate AND
>screen current together. The screen accounts for roughly 2 ma.
LV: I like the cathode resistor method…it’s less scary, and
it’ll result in a more conservative setting. I think it’s
the way to go for hobbyists and newbies.
>
>>ill it show me the total of both power tubes?
>
>No, just the one you are checking.
>
>>6) Tone robbing grid>ground caps. Schem shows 1200pf.
>>Mine are .001u (=1000pf close enough). Has anyone ever tried a lower
>>value cap to avoid oscillation yet preserve tone? After all isn’t
>>this oscillation “ultra sonic” (very high frequency) and wouldn’t a
>>lower value cap increase tone while still eliminating
>>oscillation?
>
>So far, I don’t recall anyone on this NG relating any
>horror stories about what happened when they just snipped
>out those grid-resistor bypass caps.
>If there are any, I’d like to hear ’em.
LV: I just cut ’em off. Never had a problem yet.
>
>(snip)
>The problem with the oscillation, is that the easiest ways to detect
>it, is seeing it on a ‘scope (which most folks don’t have), or
>watching your tube plates turn red as a beet. There may be..
>I’m sure there is..audible effects, too, *if* the speaker’s
>plugged in when it’s oscillating, and you’re playing thru it.
LV: You can use a dog (or cat) and a piezo-tweeter. (You can get
a piezo from any Radio Shack.) Leave your speaker hooked up,
and put the piezo-tweeter in parallel with the output; point
it at Fido (or Garfield). If he/she takes a powder, your
shit be oscillatin’. (This might sound wierd, but I guarantee
you it works.)
Lord Valve
Visit my website: http://www.freeyellow.com/members2/lord-valve/
Good tube FAQ for newbies. Click the e-mail link and request a
tube catalog. I specialize in top quality HAND-SELECTED NOS and
current-production vacuum tubes. Good prices, fast service.
TONS of gear and parts in stock…let’s DEAL!
“If you voted for Clinton in the last election, you can’t take a
dump here. Your asshole is in Washington.”
(Seen on the men’s room wall, Outback Steakhouse, Tacoma,Washington)
>
>
>
>Ned Carlson Triode Electronics “where da tubes are!”
>2225 W Roscoe Chicago, IL, 60618 USA
>ph 773-871-7459 fax 773-871-7938
>12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun
>http://www.triodeel.com
>Your Start Page for Tube and Tube Amp info on the net…
>http://www.triodeel.com/tlinks.htm
>
From Waldo–(at)–y-dejanews.com Sun Nov 1 23:02:44 CST 1998
Article: 136359 of alt.guitar.amps
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From: Waldo–(at)–y-dejanews.com
Newsgroups: alt.guitar.amps
Subject: Re: Deluxe Reverb-’70/’71 Several Questions Part II
Date: Sun, 01 Nov 1998 15:47:26 GMT
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In article <363bdafb.34341811--(at)--ews1.newscene.com>,
postmaste–(at)–riodeel.com wrote:
[snip..]
>
> So far, I don’t recall anyone on this NG relating any
> horror stories about what happened when they just snipped
> out those grid-resistor bypass caps.
> If there are any, I’d like to hear ’em.
Ask and you shall receive. I cut them out of my ’70 DR and suddenly found out
exactly what they were used to suppress. It was like a crappy fuzz pedal was
mixed into my dry signal. Sounded awful. I know it was the caps since I then
put them back in and it went away. I ended up redoing the lead dress (what a
pain) in order to get rid of the problem for good.
WP
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