I posted this on the basics newsgroup yesterday. Even though this is a
repair group I hope nobody minds if this a little off topic. But who
knows? The amp I get will probably need some sort of repair soon
enough. Anyway, the post is below. Thanks for reading.
All-
I have always like exposed tube equipment. Since I was a little
kid. So I have been thinking about getting a small stereo tube amp for
the living room to replace the typical modern amp we have. That no
longer works.
All the modern small amps have outputs of several tens of watts.
But all of the small tube amps I see and remember only have outputs of
less than ten watts. Is there something sneaky about the how the
output of modern amps is rated? I know there is gonna be some puffing
up of numbers but it seems drastic. And if the modern amps have hugely
inflated numbers does that mean a tube amp rated at 5 watts is really
only a watt or so?
There are a couple amps I have some interest in and would like
opinions on them if anybody here has the time to check out the links.
Here's the first:
https://www.ebay.com/itm/Stereo-6P1-...dd9b%7Ciid%3A1

Sorry about the mile long link. Does this amp look any good for the
money? Can someone even tell from looking at the description? I'd buy
an older used amp with exposed tubes if I could find one that I knew
worked and wasn't really expensive. I want something that sounds OK. I
am by no means an audiophile, my ears aren't that good and I know it.
But I can still hear hum and hiss.

Here's the second amp link:
https://www.ebay.com/p/APPJ-Assemble...10 0010.m2109

Another long link. There's probably enough info in that link to
describe the position of every particle in the universe. Anyway, I was
just interested in the power tube, the FU32. I have never seen a tube
like that. Is it actually just two tubes in one glass envelope?
Sharing some pins I assume? Anyway, are these types of tubes common?

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?
Thanks,
Eric

A few things:

a) To the extent possible, avoid Chinese equipment. Yes, the prices are attractive as compared to US or Euro equipment of similar ilk, but the build-quality (and the tube quality) is pretty wretched. That is not to suggest that you might not get a 'good' one, but the operative word is "might".

b) There are any number of sources of very high quality present-production US-made-and-sourced tube equipment for those who do not wish to purchase used and do their own restorations. Some links follow:

http://www.tubes4hifi.com/bob.htm

https://www.dynakitparts.com/shop/st-35-kit-120-vac/

There are others, but I am linking you to Dyna-based products as they have been around since the 50s in one form or another and are very well supported in the after-market.

c) Understand that tubes are quite different in how they behave when "seeing" speakers. Those used to solid-state equipment understand that as speaker impedance drops, wattage into those speakers increases. So an amp that puts 60 watts into an 8-ohm speaker may put 100 - 120 watts into a 4-ohm speaker. Solid-state devices also tend to clip badly. Tube amps, or at least those with output transformers (very nearly all of them) provide the same wattage irrespective of impedance - within limits. And tube amps tend to clip softly.

In my office at this very minute, I am running an OEM Dynaco ST35 into AR Athena speakers. The room is 11 x 15, and it does quite well. That is a clean 17 wpc/rms provided by a pair of 6BQ5 tubes in PP. Output wattage is a function of tube type, transformer design, and internal configuration.

A bit on tube design: the 12AX/AU/AVX types are twin-triodes - that is two triode tubes in one envelope. A 7199 is a pentode/triode. 6SN7 is an octal dual-triode and so forth. Those Chinese tubes you are looking at are eyewash - a way to make a cheaper amplifier tube - as well as lock you into *that* tube from *that* source. Avoid them like the plague they are. Yes, that is an actual tube type actually produced for the US military - but the Military had a need for a compact special-purpose tube. You do not.

Look for a reliable tube amp from a local (US) source such that if you need help/advice/service, it would be available. Bob Latino at VTA is every bit of that. And Dynakit Parts is another.

Peter Wieck
Melrose Park, PA

On Friday, 2 November 2018 00:39:41 UTC, wrote:

I posted this on the basics newsgroup yesterday. Even though this is a
repair group I hope nobody minds if this a little off topic. But who
knows? The amp I get will probably need some sort of repair soon
enough. Anyway, the post is below. Thanks for reading.
All-
I have always like exposed tube equipment. Since I was a little
kid. So I have been thinking about getting a small stereo tube amp for
the living room to replace the typical modern amp we have. That no
longer works.
All the modern small amps have outputs of several tens of watts.
But all of the small tube amps I see and remember only have outputs of
less than ten watts. Is there something sneaky about the how the
output of modern amps is rated? I know there is gonna be some puffing
up of numbers but it seems drastic. And if the modern amps have hugely
inflated numbers does that mean a tube amp rated at 5 watts is really
only a watt or so?
There are a couple amps I have some interest in and would like
opinions on them if anybody here has the time to check out the links.
Here's the first:
https://www.ebay.com/itm/Stereo-6P1-...dd9b%7Ciid%3A1

Sorry about the mile long link. Does this amp look any good for the
money? Can someone even tell from looking at the description? I'd buy
an older used amp with exposed tubes if I could find one that I knew
worked and wasn't really expensive. I want something that sounds OK. I
am by no means an audiophile, my ears aren't that good and I know it.
But I can still hear hum and hiss.

Here's the second amp link:
https://www.ebay.com/p/APPJ-Assemble...10 0010.m2109

Another long link. There's probably enough info in that link to
describe the position of every particle in the universe. Anyway, I was
just interested in the power tube, the FU32. I have never seen a tube
like that. Is it actually just two tubes in one glass envelope?
Sharing some pins I assume? Anyway, are these types of tubes common?

The last thing I was wondering about was what determines the output
power of an amp. Is it just the tubes? Transformers? Or a combination
of tubes and transformers?
Thanks,
Eric

What has changed is speakers. The modern fashion is for much lower efficiency speakers, hence hifis have gone from circa 10w to several 10s, sometimes more.

Both those amps give nowhere near enough specs to make any decision on sound quality - other than to infer that it won't be great due to them not even offering specs. The 2nd one I didn't see any specs on at all!

Valves you want to stick to popular types, or as the years roll by you'll be out of luck. That double monster is anything but popular afaik.

What determines output power? PSU, valves, transformers mainly.


NT

On Fri, 2 Nov 2018 04:47:06 -0700 (PDT), "
wrote:

A few things:

a) To the extent possible, avoid Chinese equipment. Yes, the prices are attractive as compared to US or Euro equipment of similar ilk, but the build-quality (and the tube quality) is pretty wretched. That is not to suggest that you might not get a 'good' one, but the operative word is "might".

b) There are any number of sources of very high quality present-production US-made-and-sourced tube equipment for those who do not wish to purchase used and do their own restorations. Some links follow:

http://www.tubes4hifi.com/bob.htm

https://www.dynakitparts.com/shop/st-35-kit-120-vac/

There are others, but I am linking you to Dyna-based products as they have been around since the 50s in one form or another and are very well supported in the after-market.

c) Understand that tubes are quite different in how they behave when "seeing" speakers. Those used to solid-state equipment understand that as speaker impedance drops, wattage into those speakers increases. So an amp that puts 60 watts into an 8-ohm speaker may put 100 - 120 watts into a 4-ohm speaker. Solid-state devices also tend to clip badly. Tube amps, or at least those with output transformers (very nearly all of them) provide the same wattage irrespective of impedance - within limits. And tube amps tend to clip softly.

In my office at this very minute, I am running an OEM Dynaco ST35 into AR Athena speakers. The room is 11 x 15, and it does quite well. That is a clean 17 wpc/rms provided by a pair of 6BQ5 tubes in PP. Output wattage is a function of tube type, transformer design, and internal configuration.

A bit on tube design: the 12AX/AU/AVX types are twin-triodes - that is two triode tubes in one envelope. A 7199 is a pentode/triode. 6SN7 is an octal dual-triode and so forth. Those Chinese tubes you are looking at are eyewash - a way to make a cheaper amplifier tube - as well as lock you into *that* tube from *that* source. Avoid them like the plague they are. Yes, that is an actual tube type actually produced for the US military - but the Military had a need for a compact special-purpose tube. You do not.

Look for a reliable tube amp from a local (US) source such that if you need help/advice/service, it would be available. Bob Latino at VTA is every bit of that. And Dynakit Parts is another.

Peter Wieck
Melrose Park, PA
Greetings Peter,
I took your suggestion and looked at the links provided. I spoke
with my son about what I wanted to do and he mentioned that he sees
tube equipment fairly regularly at thrift stores and estate sales and
the like. So he is gonna look for some used equipment that can be
rebuilt.
Looking at YouTube I found several videos about fixing old amps,
how replacing certain caps is really important in old equipment. How
you don't even power them up before changing out all suspect caps. But
since it's all pretty open inside and point to point it looks like
something I will have no problems with.
Since it seems like most of the small amps will be low wattage
devices sensitive speakers will be needed. I think I need speakers
rated at 90 dB or better. I have no idea what used speakers to buy if
I come across any, but maybe a little research will turn up some specs
on some of the older speakers. New speakers are probably what I'll end
up with.
Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.
Thanks,
Eric

In article ,
says...
Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.



Most NOS tubes I have dealt with seem to be fine. I have some tubes
that are very old and no problem with them. Many can be bought for a
few dollars if you look around.
I have a ham amplifier that has the origional tubes in it from aound
1975 or older. They still put out the rated power.

On Friday, 9 November 2018 23:05:29 UTC, Ralph Mowery wrote:
In article ,
says...

Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.



Most NOS tubes I have dealt with seem to be fine. I have some tubes
that are very old and no problem with them. Many can be bought for a
few dollars if you look around.
I have a ham amplifier that has the origional tubes in it from aound
1975 or older. They still put out the rated power.

I have 1930s tubes still in occasional service.

If buying old, there are plenty of crap tube amps to choose from. And some good ones. And some major winners.

As for power, speakers have gotten less sensitive for good reasons. If you're sure you need a ton of volume, look for (1960s) domestic speakers in big cabinets & try tem out. Don't touch large pre-war ex-cinema stuff, fidelity still had a long way to go.

If you buy modern, look for large woofers & cabinets, horns for mid-range. I'd also look for piezo tweeters but not everyone likes them. Those 4 features are as efficient as they get (with reasonable equipment).


NT

On Fri, 9 Nov 2018 17:06:12 -0800 (PST), wrote:

On Friday, 9 November 2018 23:05:29 UTC, Ralph Mowery wrote:
In article ,
says...

Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.



Most NOS tubes I have dealt with seem to be fine. I have some tubes
that are very old and no problem with them. Many can be bought for a
few dollars if you look around.
I have a ham amplifier that has the origional tubes in it from aound
1975 or older. They still put out the rated power.

I have 1930s tubes still in occasional service.

If buying old, there are plenty of crap tube amps to choose from. And some good ones. And some major winners.

As for power, speakers have gotten less sensitive for good reasons. If you're sure you need a ton of volume, look for (1960s) domestic speakers in big cabinets & try tem out. Don't touch large pre-war ex-cinema stuff, fidelity still had a long way to go.

If you buy modern, look for large woofers & cabinets, horns for mid-range. I'd also look for piezo tweeters but not everyone likes them. Those 4 features are as efficient as they get (with reasonable equipment).


NT
The only speaker that I know of that had piezo tweeters that sounds
good is the Dahlquist DQ10. Dahlquist put an 8 ohm resistor in
parallel with the tweeter and crossed it over above 10 khz. The normal
way of hooking the tweeters directly to the speaker input results in
horrible distortion.

On Friday, November 9, 2018 at 1:56:53 PM UTC-5, wrote:

Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.

Eric:

Yes, tubes are a whole 'nuther' thing - but at the same time, they are remarkably simple in their behavior. A few cautions:
a) Tube based equipment runs at much higher operating voltages than transistor-based equipment, most of the time. So you choose to use tubes, and you choose to do your own servicing, restoration and repairs (again and remember - these are mostly simple beasts), you will have to include an order-of-magnitude level higher in bench precautions and care. An isolation transformer is a mandate, as well as the correct understanding of its use. And so forth.
b) Whereas tubes are quite simple, they can fail in the most spectacular manner such that a certain amount of basic understanding of whatever is being repaired is required. Otherwise, the destruction of a transformer or worse could result - and that could be expensive, fatal (to the equipment) or both.

Thrift-shop/Estate-Sale equipment: I would not hesitate to purchase equipment from such sources, but only those items that are supported in the after-market. Name brands such as Fisher, Scott, Sherwood, Dynaco, McIntosh, even Stromberg-Carlson and, rarely tube Marantz are all fair game. But, some of the off-brands or large name-brands such as RCA, Zenith, and such would be problematic (but not impossible), and likely take more effort than they are worth at the end of the process. Those of us with a fairly large inventory of tubes, parts and pieces have a much different attitude than those starting off in this aspect of the hobby, where everything is a 'search'. Keep that in mind.

On tubes: Back in the day, makers such as RCA, Sylvania and others would turn out more tubes in a week than worldwide present production likely turns out in a year, and equally likely, reject the equivalent of present production monthly. I have active power-pentodes with tens of thousands of hours on them that still test well and hold bias quite nicely. I am hearing that getting 4,000 hours out of a present-day tube is 'good'.

NOS/Legacy tubes are not hard to get. Were it not for hoarding, I doubt there would be any shortage of any tube for any reason. I have (hiding somewhere) about 15 7199s, and no less than 16 1L6 tubes. All acquired over the years from garage sales, hamfests, and box-O-tubes auction purchases. Similarly, Euro and exotic tubes. Point being that I would not avoid anything for that reason, unless you are looking for a 50, or a 6T5.

On speakers: This is a function of efficiency, nature of the speaker, room size and other physical parameters. For my entire audio life, I have kept AR speakers, and at-present run 5 pairs of ARs, one pair of Maggies and one pair of Dynaco speakers. Of those eight pairs, three (all AR) are driven by tubes, including a pair AR3a speakers in a moderate room driven by a Scott LK150. Then the office system (AR Athena, Dynaco ST35) and work-room system (AR4x, Dynaco ST70). But for the Maggies, I use a brute-force solid-state device as even the big Scott would not be able to manage them in the room they are in. Point being that if you are not into ear-bleed volumes, and you are not listening in a very large room, most speakers would be just fine with most decent tube amps.

Amp Power & Clipping: A few brute facts. My most efficient speaker is 87dB at 1 watt at 1 meter.

97dB (twice as loud) would need 10 watts. This is a 10dB peak-to-average - about what is used by, at the two extremes, heavy metal and Gregorian Chant..
107dB (Twice as loud again) would need 100 watts. This is a 20dB peak-to-average, about that of well-recorded orchestral music as well as some classic rock, folk and bluegrass.
117dB - you get the picture. 1,000 watts. I have a couple of recordings that go here - the Saint-Saens Organ Symphony is one (1).

My solid-state brute-force amp is entirely capable of a 1,000 watt peak, as well as 200 sustained watts - and my speakers are perfectly happy with the former, but not the latter. However!! Solid-state amps (some, even most) if driven to clipping too much, do not 'play nice' with most speakers. A tube amp clips softly - much less chance of speaker damage. Bottom line, most situations, most speakers, most amps and if the user is reasonable, everything will be fine. It is at the edges where one moves into risky territory.

If you are going to "do legacy", I would focus on Dynaco, Sherwood/Scott/Fisher), and then everything else in that order. All of those names are well-supported, parts are available, and there is nothing exotic about any of them.

New, I would focus on VTA (tubes4hifi) first and foremost.

Best of luck.

Peter Wieck
Melrose Park, PA

On Mon, 12 Nov 2018 05:27:23 -0800 (PST), "
wrote:

On Friday, November 9, 2018 at 1:56:53 PM UTC-5, wrote:

Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.

Eric:

Yes, tubes are a whole 'nuther' thing - but at the same time, they are remarkably simple in their behavior. A few cautions:
a) Tube based equipment runs at much higher operating voltages than transistor-based equipment, most of the time. So you choose to use tubes, and you choose to do your own servicing, restoration and repairs (again and remember - these are mostly simple beasts), you will have to include an order-of-magnitude level higher in bench precautions and care. An isolation transformer is a mandate, as well as the correct understanding of its use. And so forth.
b) Whereas tubes are quite simple, they can fail in the most spectacular manner such that a certain amount of basic understanding of whatever is being repaired is required. Otherwise, the destruction of a transformer or worse could result - and that could be expensive, fatal (to the equipment) or both.

Thrift-shop/Estate-Sale equipment: I would not hesitate to purchase equipment from such sources, but only those items that are supported in the after-market. Name brands such as Fisher, Scott, Sherwood, Dynaco, McIntosh, even Stromberg-Carlson and, rarely tube Marantz are all fair game. But, some of the off-brands or large name-brands such as RCA, Zenith, and such would be problematic (but not impossible), and likely take more effort than they are worth at the end of the process. Those of us with a fairly large inventory of tubes, parts and pieces have a much different attitude than those starting off in this aspect of the hobby, where everything is a 'search'. Keep that in mind.

On tubes: Back in the day, makers such as RCA, Sylvania and others would turn out more tubes in a week than worldwide present production likely turns out in a year, and equally likely, reject the equivalent of present production monthly. I have active power-pentodes with tens of thousands of hours on them that still test well and hold bias quite nicely. I am hearing that getting 4,000 hours out of a present-day tube is 'good'.

NOS/Legacy tubes are not hard to get. Were it not for hoarding, I doubt there would be any shortage of any tube for any reason. I have (hiding somewhere) about 15 7199s, and no less than 16 1L6 tubes. All acquired over the years from garage sales, hamfests, and box-O-tubes auction purchases. Similarly, Euro and exotic tubes. Point being that I would not avoid anything for that reason, unless you are looking for a 50, or a 6T5.

On speakers: This is a function of efficiency, nature of the speaker, room size and other physical parameters. For my entire audio life, I have kept AR speakers, and at-present run 5 pairs of ARs, one pair of Maggies and one pair of Dynaco speakers. Of those eight pairs, three (all AR) are driven by tubes, including a pair AR3a speakers in a moderate room driven by a Scott LK150. Then the office system (AR Athena, Dynaco ST35) and work-room system (AR4x, Dynaco ST70). But for the Maggies, I use a brute-force solid-state device as even the big Scott would not be able to manage them in the room they are in. Point being that if you are not into ear-bleed volumes, and you are not listening in a very large room, most speakers would be just fine with most decent tube amps.

Amp Power & Clipping: A few brute facts. My most efficient speaker is 87dB at 1 watt at 1 meter.

97dB (twice as loud) would need 10 watts. This is a 10dB peak-to-average - about what is used by, at the two extremes, heavy metal and Gregorian Chant.
107dB (Twice as loud again) would need 100 watts. This is a 20dB peak-to-average, about that of well-recorded orchestral music as well as some classic rock, folk and bluegrass.
117dB - you get the picture. 1,000 watts. I have a couple of recordings that go here - the Saint-Saens Organ Symphony is one (1).

My solid-state brute-force amp is entirely capable of a 1,000 watt peak, as well as 200 sustained watts - and my speakers are perfectly happy with the former, but not the latter. However!! Solid-state amps (some, even most) if driven to clipping too much, do not 'play nice' with most speakers. A tube amp clips softly - much less chance of speaker damage. Bottom line, most situations, most speakers, most amps and if the user is reasonable, everything will be fine. It is at the edges where one moves into risky territory.

If you are going to "do legacy", I would focus on Dynaco, Sherwood/Scott/Fisher), and then everything else in that order. All of those names are well-supported, parts are available, and there is nothing exotic about any of them.

New, I would focus on VTA (tubes4hifi) first and foremost.

Best of luck.

Peter Wieck
Melrose Park, PA

Greetings Peter,
Thanks for the reply and advice. I have no issues working with high
voltages. I have a ton of respect for them. In my machine shop, which
I wired myself, I have 500 volts running to one machine. I get a
little nervous whenever I have to open the high voltage cabinet on
that mill. My hands don't shake or anything but I do get super
cautious. I make sure everything is off and check for power everwhere
before I start poking my digits around high voltage.
I have a nice isolated variac that has enough ampacity to run any
tube equipment I'll be likely to buy so I have the isolation xmfr
covered.
I just ordered some Klipsch bookshelf speakers that are rated at
90dB at 1 watt at 1 meter so speakers should not be a problem now. And
I don't blast music in the house anyway so they should be fine.
Cheers,
Eric

On Monday, 12 November 2018 16:38:04 UTC, wrote:
On Mon, 12 Nov 2018 05:27:23 -0800 (PST), "
wrote:

On Friday, November 9, 2018 at 1:56:53 PM UTC-5, wrote:

Tubes are a whole 'nuther thing. It looks like there is a lot to
learn about tubes. How specific types work, which can be substituted
for which, etc. Which are best in new production because NOS tubes may
not be any good. And are often more expensive anyway.
Any more advice and suggestions are welcome.

Eric:

Yes, tubes are a whole 'nuther' thing - but at the same time, they are remarkably simple in their behavior. A few cautions:
a) Tube based equipment runs at much higher operating voltages than transistor-based equipment, most of the time. So you choose to use tubes, and you choose to do your own servicing, restoration and repairs (again and remember - these are mostly simple beasts), you will have to include an order-of-magnitude level higher in bench precautions and care. An isolation transformer is a mandate, as well as the correct understanding of its use. And so forth.
b) Whereas tubes are quite simple, they can fail in the most spectacular manner such that a certain amount of basic understanding of whatever is being repaired is required. Otherwise, the destruction of a transformer or worse could result - and that could be expensive, fatal (to the equipment) or both.

Thrift-shop/Estate-Sale equipment: I would not hesitate to purchase equipment from such sources, but only those items that are supported in the after-market. Name brands such as Fisher, Scott, Sherwood, Dynaco, McIntosh, even Stromberg-Carlson and, rarely tube Marantz are all fair game. But, some of the off-brands or large name-brands such as RCA, Zenith, and such would be problematic (but not impossible), and likely take more effort than they are worth at the end of the process. Those of us with a fairly large inventory of tubes, parts and pieces have a much different attitude than those starting off in this aspect of the hobby, where everything is a 'search'. Keep that in mind.

On tubes: Back in the day, makers such as RCA, Sylvania and others would turn out more tubes in a week than worldwide present production likely turns out in a year, and equally likely, reject the equivalent of present production monthly. I have active power-pentodes with tens of thousands of hours on them that still test well and hold bias quite nicely. I am hearing that getting 4,000 hours out of a present-day tube is 'good'.

NOS/Legacy tubes are not hard to get. Were it not for hoarding, I doubt there would be any shortage of any tube for any reason. I have (hiding somewhere) about 15 7199s, and no less than 16 1L6 tubes. All acquired over the years from garage sales, hamfests, and box-O-tubes auction purchases. Similarly, Euro and exotic tubes. Point being that I would not avoid anything for that reason, unless you are looking for a 50, or a 6T5.

On speakers: This is a function of efficiency, nature of the speaker, room size and other physical parameters. For my entire audio life, I have kept AR speakers, and at-present run 5 pairs of ARs, one pair of Maggies and one pair of Dynaco speakers. Of those eight pairs, three (all AR) are driven by tubes, including a pair AR3a speakers in a moderate room driven by a Scott LK150. Then the office system (AR Athena, Dynaco ST35) and work-room system (AR4x, Dynaco ST70). But for the Maggies, I use a brute-force solid-state device as even the big Scott would not be able to manage them in the room they are in. Point being that if you are not into ear-bleed volumes, and you are not listening in a very large room, most speakers would be just fine with most decent tube amps.

Amp Power & Clipping: A few brute facts. My most efficient speaker is 87dB at 1 watt at 1 meter.

97dB (twice as loud) would need 10 watts. This is a 10dB peak-to-average - about what is used by, at the two extremes, heavy metal and Gregorian Chant.
107dB (Twice as loud again) would need 100 watts. This is a 20dB peak-to-average, about that of well-recorded orchestral music as well as some classic rock, folk and bluegrass.
117dB - you get the picture. 1,000 watts. I have a couple of recordings that go here - the Saint-Saens Organ Symphony is one (1).

My solid-state brute-force amp is entirely capable of a 1,000 watt peak, as well as 200 sustained watts - and my speakers are perfectly happy with the former, but not the latter. However!! Solid-state amps (some, even most) if driven to clipping too much, do not 'play nice' with most speakers. A tube amp clips softly - much less chance of speaker damage. Bottom line, most situations, most speakers, most amps and if the user is reasonable, everything will be fine. It is at the edges where one moves into risky territory.

If you are going to "do legacy", I would focus on Dynaco, Sherwood/Scott/Fisher), and then everything else in that order. All of those names are well-supported, parts are available, and there is nothing exotic about any of them.

New, I would focus on VTA (tubes4hifi) first and foremost.

Best of luck.

Peter Wieck
Melrose Park, PA

Greetings Peter,
Thanks for the reply and advice. I have no issues working with high
voltages. I have a ton of respect for them. In my machine shop, which
I wired myself, I have 500 volts running to one machine. I get a
little nervous whenever I have to open the high voltage cabinet on
that mill. My hands don't shake or anything but I do get super
cautious. I make sure everything is off and check for power everwhere
before I start poking my digits around high voltage.
I have a nice isolated variac that has enough ampacity to run any
tube equipment I'll be likely to buy so I have the isolation xmfr
covered.
I just ordered some Klipsch bookshelf speakers that are rated at
90dB at 1 watt at 1 meter so speakers should not be a problem now. And
I don't blast music in the house anyway so they should be fine.
Cheers,
Eric

don't think I've ever seen an isolated variac.

Modern speakers are fine on valve amps really. Unless you want excessive volume, or the amp has all of 3W available.


NT

There are plenty of isolated variacs.

I own a VIZ ISO-V-AC II WP-30. Nice unit.




don't think I've ever seen an isolated variac.

Modern speakers are fine on valve amps really. Unless you want excessive volume, or the amp has all of 3W available.


NT

On Monday, November 12, 2018 at 4:55:24 PM UTC-5, Terry Schwartz wrote:
There are plenty of isolated variacs.

I own a VIZ ISO-V-AC II WP-30. Nice unit.


Very nice. My buddy has a Sencore isolated variac that is similar to your VIZ.

I've got an RCA isotap II in my shop (WP-27A).

https://community.klipsch.com/upload...9308189164.jpg

Bought it new back in the 70s and use it every work day. No gauges, but it has a tap for monitoring the output. Just meat and potatoes.






don't think I've ever seen an isolated variac.

Modern speakers are fine on valve amps really. Unless you want excessive volume, or the amp has all of 3W available.


NT

On Monday, November 12, 2018 at 4:26:13 PM UTC-5, wrote:


don't think I've ever seen an isolated variac.

Modern speakers are fine on valve amps really. Unless you want excessive volume, or the amp has all of 3W available.

http://www.byan-roper.org/steve/stev...-variable.html

I keep two of these. One in the travel kit, one permanently on the bench. The link shows the innards as well.

Most of the VIZ & Sencore units have leakage testing as well. By the way, VIZ, a Philadelphia company was a jobber for RCA, making many of their test equipment under either name.

Peter Wieck
Melrose Park, PA