[adam79]

Can anyone give me any information about this picture of an Amperex
Bugle Boy 7025: http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

Thanks,
-Adam

[Scott Dorsey]

adam79 wrote:
Can anyone give me any information about this picture of an Amperex
Bugle Boy 7025: http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

The V1 position of what, why?

You should know that the vast majority of "Amperex" and "Telefunken"
tubes for sale out there are forgeries these days, unfortunately.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On 11/20/2010 8:45 PM, adam79 wrote:

I'm thinking of buying this and putting it in the V1 position.

How much? It looks a bit like a rebrand to me. What makes
you think it might be better than what you have now? I guess
"V1 position" means the first stage of an amplifier. What
kind of amplifier? What's there now? What's wrong with
what's there now?

--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[adam79]

On 11/21/10 7:22 AM, Mike Rivers wrote:
On 11/20/2010 8:45 PM, adam79 wrote:

I'm thinking of buying this and putting it in the V1 position.

How much? It looks a bit like a rebrand to me. What makes you think it
might be better than what you have now? I guess "V1 position" means the
first stage of an amplifier. What kind of amplifier? What's there now?
What's wrong with what's there now?


$20. That's why I put the picture up; I've never seen a Bugle Boy that
looks like that. I have a 1990 Peavey VTM-120 that could use new preamp
tubes. V1 is the fist gain stage, V2 is the second gain stage, V3 is the
effects loop buffer and V4 is the Phase Inverter. The amp still has the
original stock tubes. The preamp tubes are labeled Peavey Super 7. Would
it be recommended to put in a low noise tube for the effects loop buffer?

Thanks,
-Adam

[Scott Dorsey]

adam79 wrote:

$20. That's why I put the picture up; I've never seen a Bugle Boy that
looks like that. I have a 1990 Peavey VTM-120 that could use new preamp
tubes. V1 is the fist gain stage, V2 is the second gain stage, V3 is the
effects loop buffer and V4 is the Phase Inverter. The amp still has the
original stock tubes. The preamp tubes are labeled Peavey Super 7. Would
it be recommended to put in a low noise tube for the effects loop buffer?

What makes you think it needs new preamp tubes after only 20 years of use?
Put them on a tester, check transconductance. If they are low, replace them
with legitimate tubes from a legitimate source. For that family of tubes,
the current JJ production is surprisingly good but there are plenty of others
out there.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[David Gravereaux]

On 11/20/2010 05:45 PM, adam79 wrote:
Can anyone give me any information about this picture of an Amperex
Bugle Boy 7025: http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

Adam,

A 7025 is a low-noise equivalent of a 12AX7A. How that specific tubes
in the picture measures, I can't say. Nor can I comment on your
application. I'm assuming this is for an application that is not a
guitar amp.

Personally, I've had good results with a J/J ECC803S (*not* the frame
grid tube though from the number you would think it is). There are a
great many 12AX7A brands and equivalents. Some are terrible, some aren't.

--



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[Jay Ts[_2_]]

Scott Dorsey wrote:
adam79 wrote:

$20. That's why I put the picture up; I've never seen a Bugle Boy that
looks like that. I have a 1990 Peavey VTM-120 that could use new preamp
tubes. V1 is the fist gain stage, V2 is the second gain stage, V3 is the
effects loop buffer and V4 is the Phase Inverter. The amp still has the
original stock tubes. The preamp tubes are labeled Peavey Super 7. Would
it be recommended to put in a low noise tube for the effects loop
buffer?

What makes you think it needs new preamp tubes after only 20 years of
use? Put them on a tester, check transconductance.

Often, tube guitar amps do not employ feedback in the preamp stage,
so it's not just the transconductance ("gain") that matters, but
the specific shape of the transfer curve. This varies from model
to model of tube, and different models of tubes can have distinctly
different sounds, depending on various factors. They add
different amounts of 2nd and other harmonics, and can behave
in slightly different ways.

IMO, 20 years is way too long to wait to replace preamp tubes
in tube guitar amps if the amp has been turned on for much of
that time. I don't have any scientifically-performed test to
show, but I did an informal test on my own (self-designed) tube
preamp, and left it on continuously for a year to see if I could
see and/or hear the amount of wear. After the year was up, the
tube looked different, and replacing it with a new tube resulted
in an obviously much better sound.

I don't know if any of this applies to the Peavey VTM-120.
I found a schematic online that claims to be for that amp,
but I don't have time to analyze it.

Jay Ts

[Arny Krueger]

"Scott Dorsey" wrote in message

adam79 wrote:
Can anyone give me any information about this picture of
an Amperex Bugle Boy 7025:
http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

The V1 position of what, why?

You should know that the vast majority of "Amperex" and
"Telefunken" tubes for sale out there are forgeries these
days, unfortunately. --scott

Bad news, BTW. Word has it that resuscitation of the old Mullard factory in
Blackburn, England has failed and is being liquidated.

[Richard Kuschel]

On Nov 20, 7:45*pm, adam79 wrote:
Can anyone give me any information about this picture of an Amperex
Bugle Boy 7025:http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

Thanks,
-Adam

How would you know from a picture whether a tube is good or not?
I am assuming that you are going to use this in a guitar amp.
You can't even tell if a tube is good for that application by testing
it with a tube checker because it could check out just fine and still
be microphonic.

[Jay Ts[_2_]]

On Mon, 22 Nov 2010 09:36:30 -0500, Arny Krueger wrote:

"Scott Dorsey" wrote in message

adam79 wrote:
Can anyone give me any information about this picture of an Amperex
Bugle Boy 7025:
http://members.toast.net/adam79/7025.png. I'm thinking of buying this
and putting it in the V1 position.

The V1 position of what, why?

You should know that the vast majority of "Amperex" and "Telefunken"
tubes for sale out there are forgeries these days, unfortunately.
--scott

Bad news, BTW. Word has it that resuscitation of the old Mullard factory
in Blackburn, England has failed and is being liquidated.

Bummer.

Does anyone know exactly what happened to the Ei factory?
They were still in business through the Serbian war, but I heard
that they later shut down. I don't need any more right now, and
maybe not ever, but I'd like to see the supply of Ei tubes continue.

Jay Ts

[Scott Dorsey]

Arny Krueger wrote:
"Scott Dorsey" wrote in message

adam79 wrote:
Can anyone give me any information about this picture of
an Amperex Bugle Boy 7025:
http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

The V1 position of what, why?

You should know that the vast majority of "Amperex" and
"Telefunken" tubes for sale out there are forgeries these
days, unfortunately. --scott

Bad news, BTW. Word has it that resuscitation of the old Mullard factory in
Blackburn, England has failed and is being liquidated.

Yes, I wrote about that this summer in Recording magazine.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Jay Ts wrote:

Does anyone know exactly what happened to the Ei factory?
They were still in business through the Serbian war, but I heard
that they later shut down. I don't need any more right now, and
maybe not ever, but I'd like to see the supply of Ei tubes continue.

I believe their products are now sold through JJ.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[adam79]

On 11/22/10 9:41 AM, Richard Kuschel wrote:
On Nov 20, 7:45 pm, wrote:
Can anyone give me any information about this picture of an Amperex
Bugle Boy 7025:http://members.toast.net/adam79/7025.png. I'm thinking
of buying this and putting it in the V1 position.

Thanks,
-Adam

How would you know from a picture whether a tube is good or not?
I am assuming that you are going to use this in a guitar amp.
You can't even tell if a tube is good for that application by testing
it with a tube checker because it could check out just fine and still
be microphonic.


I wasn't asking if it was "good or not" by the picture! I had never seen
an Amperex Bugle Boy with the 7025 marking.

Thank you David for the info about the 7025 being a low noise tube.
That's not what I'm looking for in a V1 (first gain stage) preamp tube.

In response to Scott, I want to replace the Super 7 tubes because I'm
not a fan of their sound.

-Adam

[Scott Dorsey]

adam79 wrote:
I wasn't asking if it was "good or not" by the picture! I had never seen
an Amperex Bugle Boy with the 7025 marking.

Oh, there's all kinds of that stuff out there. You can buy Amperex 6550
tubes, even though Amperex never made or sold a 6550 when they were a
going concern.

Mind you this isn't a new thing. Back in the seventies you could buy
"12AT7" tubes from Radio Shack that were actually specialty computer
switching tubes that had the same pinout and a similar mu... someone
in Texas got a good deal on a bunch of them and stamped 12AT7 on them.

Thank you David for the info about the 7025 being a low noise tube.
That's not what I'm looking for in a V1 (first gain stage) preamp tube.

No? That would seem the first place to worry about noise.

In response to Scott, I want to replace the Super 7 tubes because I'm
not a fan of their sound.

Consider the JJ tubes before anything else. You may like them, you may
not, but if you don't like them in the guitar amp you can use them in
something else.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[adam79]

On 11/22/10 5:07 PM, Scott Dorsey wrote:
wrote:
I wasn't asking if it was "good or not" by the picture! I had never seen
an Amperex Bugle Boy with the 7025 marking.

Oh, there's all kinds of that stuff out there. You can buy Amperex 6550
tubes, even though Amperex never made or sold a 6550 when they were a
going concern.


Yeah, I've heard/read about tube forgery more times than I'd like to
count (if that would even be a possibility at this point!)

Mind you this isn't a new thing. Back in the seventies you could buy
"12AT7" tubes from Radio Shack that were actually specialty computer
switching tubes that had the same pinout and a similar mu... someone
in Texas got a good deal on a bunch of them and stamped 12AT7 on them.


Also, I've seen alot of deceiving descriptions (in internet
ads/auctions) hyping hi-fi tubes (ment for electronics) as great amp
tubes. These stick out like a sore thumb if you know what to look for..

Thank you David for the info about the 7025 being a low noise tube.
That's not what I'm looking for in a V1 (first gain stage) preamp tube.

No? That would seem the first place to worry about noise.


Are you referring to sub-par tubes that are naturally noisy due to bad
production? The VTM series is so gain heavy that a low noise tube might
help improve the amp's clean sound. While on the topic of low gain
tubes, are there any specific 12at7s that you guys like better than
others? I haven't tried many, but I've come to really like the NOS
Mullard 12at7wa (especially for the PI). Would a 12at7 (or other low
gain preamp tube) be recommended for the effects loop buffer?

Thanks for the help,
-Adam

[Mike Rivers]

On 11/22/2010 4:56 PM, adam79 wrote:

Thank you David for the info about the 7025 being a low
noise tube. That's not what I'm looking for in a V1 (first
gain stage) preamp tube.

I would think that this is the very place where you'd want a
low noise tube. What are guitar players thinking these days?
Or are they?


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Jay Ts[_2_]]

Scott Dorsey wrote:
Jay Ts wrote:

Does anyone know exactly what happened to the Ei factory? They were
still in business through the Serbian war, but I heard that they later
shut down. I don't need any more right now, and maybe not ever, but I'd
like to see the supply of Ei tubes continue.

I believe their products are now sold through JJ. --scott

Aha! Well, if that is true, I now understand
your recommendation for JJ. Out of the 12ax7's
I tried, Ei was by far my favorite.

Jay Ts

[Jay Ts[_2_]]

Mike Rivers wrote:
adam79 wrote:

Thank you David for the info about the 7025 being a low noise tube.
That's not what I'm looking for in a V1 (first gain stage) preamp tube.

I would think that this is the very place where you'd want a low noise
tube. What are guitar players thinking these days? Or are they?

In most live situations, there is far more noise from EMI-induced
pickup hum, so the noise of the vacuum tubes is relatively unimportant.

Really, vacuum tubes don't make that much noise. Take a look
at this spectrum from my tube preamp, which is just a single
stage inverting 12ax7 amplifier:

http://jayts.com/images/JayTs-TubePr...ctrum_1Khz.jpg

(This is a circuit that I designed 13 years ago, when I didn't
even have an oscilloscope or spectrum analyzer. I designed the
circuit with just a DMM and my ears for testing. Today, I could
probably do a little better. ;-)

Rather than focusing on noise, I think most guitarists prefer to
get a "good sound" from the harmonics induced by the non-negative
feedback circuit in the preamp. You can see that the 2nd harmonic
in my tube pre is at about -38 dB, and the 3rd is at about -60 dB.
(Peaks after the 5th harmonic are not significant, and are from
the sound card or other sources.)

Sometime, I may take the preamp out of the closet again and try
doing this test with other models of 12ax7 to see if the
differences show up in the spectral plot.

Jay Ts

[Mike Rivers]

On 11/23/2010 7:34 AM, Jay Ts wrote:

In most live situations, there is far more noise from EMI-induced
pickup hum, so the noise of the vacuum tubes is relatively unimportant.

Well, that sucks. But sometimes you really can get things
quiet, and for that you'll appreciate a quiet tube. The 7025
is "low noise" by design, but you might find a particularly
rugged 12AX7 that's more resistant to microphonics, and I
think that would be important in a high gain stage. Or you
could do what other guitar players do and either use the
"voodoo" tube that someone says is the greatest, just plug
in any tube and go for it, or get an assortment and select
your favorite.

Rather than focusing on noise, I think most guitarists prefer to
get a "good sound" from the harmonics induced by the non-negative
feedback circuit in the preamp.

Probably so, and I don't think there's anything about
published tube characteristics that would predict that. Tube
characteristic curves are like microphone frequency response
curves - generic.



--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Jay Ts[_2_]]

Mike Rivers wrote:
Jay Ts wrote:

In most live situations, there is far more noise from EMI-induced
pickup hum, so the noise of the vacuum tubes is relatively unimportant.

Well, that sucks. But sometimes you really can get things quiet, and for
that you'll appreciate a quiet tube. The 7025 is "low noise" by design,
but you might find a particularly rugged 12AX7 that's more resistant to
microphonics,

I'm laughing at that because my favorite 12ax7 is horribly microphonic!
Tapping on the preamp's case causes a the tube to produce a ringing
sound that last for a fraction of a second.

I think it adds character. Somewhat like the "boink" sound from
a real spring reverb. In practice, it doesn't bother me because
the preamp is not on top of the speakers, and I am not playing
loud enough to cause any noticeable problems.

Anyway, you have a good point, and I should try a 7025 the next
time I'm working with vacuum tubes. I might like it.

But right now, I'm more interested in getting a JJ tube to
see if they are the same as my Ei's. I hope so, and if I don't
get microphonics from them, I will actually be disappointed.
(Not because I like microphonic tubes, but because I love
the Ei 12ax7, which is known for being very microphonic.)

Rather than focusing on noise, I think most guitarists prefer to get a
"good sound" from the harmonics induced by the non-negative feedback
circuit in the preamp.

Probably so, and I don't think there's anything about published tube
characteristics that would predict that. Tube characteristic curves are
like microphone frequency response curves - generic.

One of the most important things I've learned in electronics
is how to read a manufacturer's datasheet. That is, what to
take seriously, and which parts to take with a kilo of salt.

Often, the curves shown in datasheets are as much art as engineering.

In the circuits I'm working on, I use them only for comparisons
to other products, and not for circuit design. I also can't use
Spice, because the Spice models are just as bad. So I measure
the characteristics of real devices to learn how they work.

Jay Ts

[Mike Rivers]

On 11/24/2010 6:25 AM, Jay Ts wrote:

But right now, I'm more interested in getting a JJ tube to
see if they are the same as my Ei's.

You think you'll be able to tell that a new JJ tube is the
same as your old EI tubes? Or are you going on physical
appearance? Just don't let the vacuum out. g

http://www.weirdlinks.org/images/upl...acuumtubes.jpg

Often, the curves shown in datasheets are as much art as engineering.

In the circuits I'm working on, I use them only for comparisons
to other products, and not for circuit design.

The characteristic curves are useful for telling you where
to set the operating point for best linearity. When dealing
with a guitar amplifier, however, you might not want to do
that.


--
"Today's production equipment is IT based and cannot be
operated without a passing knowledge of computing, although
it seems that it can be operated without a passing knowledge
of audio." - John Watkinson

http://mikeriversaudio.wordpress.com - useful and
interesting audio stuff

[Jay Ts[_2_]]

Mike Rivers wrote:
Jay Ts wrote:

But right now, I'm more interested in getting a JJ tube to see if they
are the same as my Ei's.

You think you'll be able to tell that a new JJ tube is the same as your
old EI tubes?

I can't tell if they are exactly the same, from the Ei factory,
but I can tell by listening if they have the "Ei sound" that
I'm familiar with.

Or are you going on physical appearance? Just don't let
the vacuum out. g

I will look at the physical appearance too, for certain!

I might even sacrifice one of my used Ei tubes and break
open a new JJ to take a peek at the internals. It's kind
of fun, actually, to break open vacuum tubes -- my first
experiences doing that was when I was about 10, with old
radios and other things I found in my parents' basement.

My limited understanding (?) is that different manufacturers'
12ax7's have different physical design and construction, and
that it plays a big part. At least, different companies make/made
12ax7's differently, and you can see the differences.

(But no, it's not the diamond on the bottom of Telefunken
tubes that made them sound better.

If Ei and JJ 12ax7's appear exactly the same, it would suggest
that they were made in the same manner, by the same factory.
I'm just applying archaeological thinking here. ;-) Anyway,
if I can't tell the difference in the sound, that's good
enough for me!

Jay Ts