Author Topic: My New Don Sachs Model 2 Preamp Unboxing  (Read 412 times)

Offline mresseguie

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #15 on: June 27, 2020, 08:42:59 PM »
Don,

There's probably not enough room in your listening room. I can take it off your hands during burn in. I'll treat it like my own.  :thumb:

No need to thank me. It's the least I can do.  8)

Pics! Pics! How does it sound?  :drool:
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Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #16 on: June 27, 2020, 09:51:18 PM »
Don,

There's probably not enough room in your listening room. I can take it off your hands during burn in. I'll treat it like my own.  :thumb:

No need to thank me. It's the least I can do.  8)

Pics! Pics! How does it sound?  :drool:

Oh, it sounds quite good.   I am giving it 10-20 hours before I really evaluate it, but it is better than the little 19 watt/ch prototype I built.  This one has that powerful sound you are used to.   More in a day or two.  Have to make a page for the website for it.

Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #17 on: July 03, 2020, 08:14:36 AM »
Update on the integrated amp.   I upped the bias a wee bit so that it is now at about 17.7 watts at idle.  The 6P3S-E is happier there and sounds amazing at about 50 hours.  Very holographic.  The amp makes about 33 watts/ch on the bench and does so all the way down to 20Hz with no trouble (both channels driven of course).   So we will call it a 30 wpc integrated that beats it spec by a bit.  17.7 watts is a good idle bias spot because that is right at 70% for the 25 watt rated tubes like the EL34 and KT66.  I tried some vintage Mullard EL34 tubes I have kept over the years.  They sound nice, but I prefer the 6P3S-E.   I have never really liked the EL34 types.  Nice mids, but a bit bright sounding.  Never understood the obsession with that tube type.   I would love to try a quad of good KT66, but they are $100 - $150 per quad and you can buy 6P3S-E for $45-60 per quad.  They don't need to be matched at all in my gear due to the auto biasing.  Amp just doesn't care.  That is good because if you buy a quad of most Russian power tubes on ebay you will find they are all over the map for current draw unless someone has matched them.

I will make a page on my site for the Valhalla this weekend as soon as I take some good photos.   It has exceeded my sonic expectations for the project and it is still not completely run in :)  This one is off to Clayton Shaw of Spatial Audio speaker fame for evaluation.  He has heard lots of amps so I am interested in his unbiased opinion of this one.
« Last Edit: July 03, 2020, 08:38:03 AM by dls123 »

Offline mresseguie

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #18 on: July 03, 2020, 10:21:15 AM »
Don,

Are you saying that KT66 tubes are interchangeable with the 6P3S-E tubes?

I have no experience with either tube - Is there a sonic difference?

Have you determined the Valhalla's weight (and also the shipping weight)?

I'm betting the Valhalla would be happier driving 88dB and higher speakers, but perhaps 83dB 2-way monitors in a small bedroom would work quite well as well?

"Valhalla"....mmm....it has a nice ring to it.  :beer:
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Offline P.I.

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #19 on: July 03, 2020, 03:09:42 PM »
I have no experience with either tube - Is there a sonic difference?
Michael.  Iím with Mr. Sachs on the EL34 thing.  Not my favorite tube for audio.  Great in Ďsomeí guitar amps. I much prefer the KT77 over the EL34 for audio.  It could be the tetrode vs pentode thing.  That extra grid gets in the way.  I like KT88ĎS better than 6550ís, too.

My favorite tube for 30 - 35 watt stereo amps are KT66ís.  They have always seemed to do every aspect of the sonic spectrum even handedly.  Iím finishing up a rebuild of a Dyna ST70 with a VTA input board.  Iím using the improved, high current power transformer.  It will handle the heater current those hungry KT66 draw.  Iíll be comparing KT77 and KT66 outputs.  Iím thinking that I already know...

I'll let you know my findings.

I wish I could swing one of Donís amps... but not right now  :(
« Last Edit: July 03, 2020, 03:12:16 PM by P.I. »
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Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #20 on: July 03, 2020, 05:42:46 PM »
I have no experience with either tube - Is there a sonic difference?
Michael.  Iím with Mr. Sachs on the EL34 thing.  Not my favorite tube for audio.  Great in Ďsomeí guitar amps. I much prefer the KT77 over the EL34 for audio.  It could be the tetrode vs pentode thing.  That extra grid gets in the way.  I like KT88ĎS better than 6550ís, too.

My favorite tube for 30 - 35 watt stereo amps are KT66ís.  They have always seemed to do every aspect of the sonic spectrum even handedly.  Iím finishing up a rebuild of a Dyna ST70 with a VTA input board.  Iím using the improved, high current power transformer.  It will handle the heater current those hungry KT66 draw.  Iíll be comparing KT77 and KT66 outputs.  Iím thinking that I already know...

I'll let you know my findings.

I wish I could swing one of Donís amps... but not right now  :(

Hi
So what bias point do you like the KT66 at?   It is a 25 watt tube, so 70% is about 17.5 watts at idle, but then the screens are a few percent, so really about 18 watts should be pretty good.  I may crank the bias a wee bit more by changing a resistor on the bias board and shoot for about 18 watts.   Any real 25 watt rated tube should take 18 watts all day long and have a very long life.    I saw a post by my old pal Jim McShane who said the 6P3S-E is really about as tough as a 6L6GC, which would be a 30 watt tube.   He said you could bias them at WELL over 20 watts with no problems.   You might try a quad of the 6P3S-E in your experiment.  As long as they are over 17 watts that seemed to be a sweet spot.   I will try them a bit hotter to around 18 watts.  They are an excellent tube even without the cheap price.   They take a good 50 hours to run in though or more.   I really should get a quad of KT66 to play with, but I have read reports from folks who said they thought the 6P3S-E sounded pretty much as good as their gold lion reissue kt66... so I haven't bothered.   So many tubes.... so little time:)

Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #21 on: July 03, 2020, 06:00:37 PM »
Don,

Are you saying that KT66 tubes are interchangeable with the 6P3S-E tubes?

I have no experience with either tube - Is there a sonic difference?

Have you determined the Valhalla's weight (and also the shipping weight)?

I'm betting the Valhalla would be happier driving 88dB and higher speakers, but perhaps 83dB 2-way monitors in a small bedroom would work quite well as well?

"Valhalla"....mmm....it has a nice ring to it.  :beer:

Hi Michael...
The Valhallas are the mountain range I look at out my window:)
The 6L6 types and the KT types all have the same pinout.  No connection on pin 6 and pin 1.   So, if you observe the rules about biasing and tube power ratings they are interchangeable.   You want to bias a tube in a push pull circuit at 65 to 75 % of its max plate dissipation usually.   So a KT88 is a 42 watt tube and should be biased at 28-32 watts or so, although some of the vintage amps would run them up to 35 watts.   The KT66 is a 25 watt tube, and I believe the kt77 is as well, so they are biased at more like 17-18 watts.   The EL34 has pin 1 connected to a suppressor grid.  That should be at the same potential as the cathode on pin 8, usually right around ground.   In my Valhalla pins 1 and 8 are separated by the cathode fuse and I am using pin 1 as a tie point.  However, since the fuse has only about 1 ohm of resistance it is just fine to put an EL34 in that circuit.   There are other circuits where people are using pin 1 as a tie point and it could have some high voltage on it.  You cannot put an EL34 in there.   So it depends on what people are doing with pin 1 in an amp that is designed for the 6L6 or one of the KT family, since they don't use pin 1.   It is very convenient to use pins 1 and 6 on an octal tube socket as tie points for wiring.  You cannot do that with the EL34.   Yet another reason not to use an EL34:)  It makes wiring harder..... and it sounds kind of bright to me.

30 watts/ch will drive many speakers, but it really depends on how difficult load a speaker is as well as the efficiency, yes.  That, and how loud you like things.   I had a guy years ago who had me rebuild one of the little Sherwood EL84 integrated amps for all of about 17 watts/ch.  He drove maggies in a small room and thought it was the best amp he ever heard.   So anything is possible I guess.   Anything well behaved above 89-90 dB should probably be OK, but 92 dB speakers would be much easier to drive and there are so many great choices like the whole spatial audio line, or the daedalus you like as I recall.  All are quite efficient, and that is really what this amp is aimed at.

Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #22 on: July 03, 2020, 08:01:04 PM »
I also forgot to state above that each tube can work best with a different transformer primary.   For example, in an ultralinear push pull circuit, both the EL34 and the 6L6 work very nicely with a 6.6K primary.  In other circuits or with other tubes the optimal primary will differ.   So it is really impossible to say what tubes will work well unless you know the bias point, the transformer primary, and the circuit.  Just because you can plug a certain tube in and it won't blow up doesn't mean it will sound good.  Also, you may prefer the KT77 in one circuit and the KT66 or 6L6 more in another.   So if you read that someone likes to bias their EL34 and 40 mA, it means absolutely nothing if you don't know the plate voltage or the circuit, or whether it is fixed or cathode bias or the transformer primary, etc...   In general, I don't really like the EL34, but maybe there is a circuit where I would like it more than anything else.....

Offline P.I.

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #23 on: July 03, 2020, 08:05:05 PM »
I have no experience with either tube - Is there a sonic difference?
Michael.  Iím with Mr. Sachs on the EL34 thing.  Not my favorite tube for audio.  Great in Ďsomeí guitar amps. I much prefer the KT77 over the EL34 for audio.  It could be the tetrode vs pentode thing.  That extra grid gets in the way.  I like KT88ĎS better than 6550ís, too.

My favorite tube for 30 - 35 watt stereo amps are KT66ís.  They have always seemed to do every aspect of the sonic spectrum even handedly.  Iím finishing up a rebuild of a Dyna ST70 with a VTA input board.  Iím using the improved, high current power transformer.  It will handle the heater current those hungry KT66 draw.  Iíll be comparing KT77 and KT66 outputs.  Iím thinking that I already know...

I'll let you know my findings.

I wish I could swing one of Donís amps... but not right now  :(

Hi
So what bias point do you like the KT66 at?   It is a 25 watt tube, so 70% is about 17.5 watts at idle, but then the screens are a few percent, so really about 18 watts should be pretty good.  I may crank the bias a wee bit more by changing a resistor on the bias board and shoot for about 18 watts.   Any real 25 watt rated tube should take 18 watts all day long and have a very long life.    I saw a post by my old pal Jim McShane who said the 6P3S-E is really about as tough as a 6L6GC, which would be a 30 watt tube.   He said you could bias them at WELL over 20 watts with no problems.   You might try a quad of the 6P3S-E in your experiment.  As long as they are over 17 watts that seemed to be a sweet spot.   I will try them a bit hotter to around 18 watts.  They are an excellent tube even without the cheap price.   They take a good 50 hours to run in though or more.   I really should get a quad of KT66 to play with, but I have read reports from folks who said they thought the 6P3S-E sounded pretty much as good as their gold lion reissue kt66... so I haven't bothered.   So many tubes.... so little time:)
Pretty much what you said.  IIRC my last ones in another amp weíre right at 17W for stereo use.  Iím VERY familiar with them in guitar amps.  They sing... see the Mayall Beano album and Claptonís tone.  Quintessential British blues. Sweeter than 6L6GC.

Iíll include the 6P3S-E in the trials.  At the price Iíd be kind of dumb not to do so!

Like you said: so many tubes... so little time!

« Last Edit: July 03, 2020, 08:10:33 PM by P.I. »
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Offline mresseguie

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #24 on: July 03, 2020, 09:35:26 PM »
Are you saying that KT66 tubes are interchangeable with the 6P3S-E tubes? Is there a sonic difference between KT-66 and 6P3S-E tubes?
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Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #25 on: July 04, 2020, 07:45:44 AM »
Are you saying that KT66 tubes are interchangeable with the 6P3S-E tubes? Is there a sonic difference between KT-66 and 6P3S-E tubes?

They pretty much should be, yes.  Not the 6P3S, but only the 6P3S-E because it appears to have a power rating far above the 20.5 watts or so that is in the spec sheet.  As McShane noted, it really is 25-30 watts.   As for the sonic difference, I have not played with KT66 tubes, but they are supposed to be excellent.  From what I could glean, the Chinese KT66 (Valve Art, TAD, Shuguang, etc...) are all Shuguang tubes and sound best when biased at 70% of max rating.  The JJ is supposed to be a good tube, and the Russian Gold Lion reissue as well, which is the most expensive.  You can get Chinese ones for about $100 per quad.  I think there is a black treasure version which is expensive. 

It is just that the 6P3S-E sounds very good and if you buy them 12 at a time you can get them for a little over $10 per tube, well maybe $12 or so with shipping.  Of course the shipping from Russia now is 3 months......  So I had little motivation to pay $150 for a quad of gold lion kt66, but I probably should....   My guess is that the 6P3S-E is in the same league though for 30-40% of the price.  At some point things are just way more than good enough to enjoy:)

Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #26 on: July 04, 2020, 07:47:32 AM »
I have no experience with either tube - Is there a sonic difference?
Michael.  Iím with Mr. Sachs on the EL34 thing.  Not my favorite tube for audio.  Great in Ďsomeí guitar amps. I much prefer the KT77 over the EL34 for audio.  It could be the tetrode vs pentode thing.  That extra grid gets in the way.  I like KT88ĎS better than 6550ís, too.

My favorite tube for 30 - 35 watt stereo amps are KT66ís.  They have always seemed to do every aspect of the sonic spectrum even handedly.  Iím finishing up a rebuild of a Dyna ST70 with a VTA input board.  Iím using the improved, high current power transformer.  It will handle the heater current those hungry KT66 draw.  Iíll be comparing KT77 and KT66 outputs.  Iím thinking that I already know...

I'll let you know my findings.

I wish I could swing one of Donís amps... but not right now  :(

Hi
So what bias point do you like the KT66 at?   It is a 25 watt tube, so 70% is about 17.5 watts at idle, but then the screens are a few percent, so really about 18 watts should be pretty good.  I may crank the bias a wee bit more by changing a resistor on the bias board and shoot for about 18 watts.   Any real 25 watt rated tube should take 18 watts all day long and have a very long life.    I saw a post by my old pal Jim McShane who said the 6P3S-E is really about as tough as a 6L6GC, which would be a 30 watt tube.   He said you could bias them at WELL over 20 watts with no problems.   You might try a quad of the 6P3S-E in your experiment.  As long as they are over 17 watts that seemed to be a sweet spot.   I will try them a bit hotter to around 18 watts.  They are an excellent tube even without the cheap price.   They take a good 50 hours to run in though or more.   I really should get a quad of KT66 to play with, but I have read reports from folks who said they thought the 6P3S-E sounded pretty much as good as their gold lion reissue kt66... so I haven't bothered.   So many tubes.... so little time:)
Pretty much what you said.  IIRC my last ones in another amp weíre right at 17W for stereo use.  Iím VERY familiar with them in guitar amps.  They sing... see the Mayall Beano album and Claptonís tone.  Quintessential British blues. Sweeter than 6L6GC.

Iíll include the 6P3S-E in the trials.  At the price Iíd be kind of dumb not to do so!

Like you said: so many tubes... so little time!

That would be really interesting.  Please post your results.  The more data points the better!  This is in an ST-70 clone?  Octal front end or small tubes?

Offline toobluvr

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #27 on: July 04, 2020, 11:59:47 AM »
This Russian lettering system always confuses me........
Is this 6P3S-E tube you guys are discussing the same as this Russian 6N3C-E in this article?

https://jeffsplace.positive-feedback.com/6n3ce-vacuum-tubes/

I use this power tube in my Will Vincent Baldwin organ amp, as it is the one that Will recommends.  Can't compare as I haven't tried any other 6L6 varieties,  but it sounds real good to me.

I ask because my understanding is that both are replacements for 6L6 tubes, and I thought they might be the same tube.








« Last Edit: July 04, 2020, 12:08:06 PM by toobluvr »
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Offline P.I.

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #28 on: July 04, 2020, 12:17:02 PM »
I have no experience with either tube - Is there a sonic difference?
Michael.  Iím with Mr. Sachs on the EL34 thing.  Not my favorite tube for audio.  Great in Ďsomeí guitar amps. I much prefer the KT77 over the EL34 for audio.  It could be the tetrode vs pentode thing.  That extra grid gets in the way.  I like KT88ĎS better than 6550ís, too.

My favorite tube for 30 - 35 watt stereo amps are KT66ís.  They have always seemed to do every aspect of the sonic spectrum even handedly.  Iím finishing up a rebuild of a Dyna ST70 with a VTA input board.  Iím using the improved, high current power transformer.  It will handle the heater current those hungry KT66 draw.  Iíll be comparing KT77 and KT66 outputs.  Iím thinking that I already know...

I'll let you know my findings.

I wish I could swing one of Donís amps... but not right now  :(

Hi
So what bias point do you like the KT66 at?   It is a 25 watt tube, so 70% is about 17.5 watts at idle, but then the screens are a few percent, so really about 18 watts should be pretty good.  I may crank the bias a wee bit more by changing a resistor on the bias board and shoot for about 18 watts.   Any real 25 watt rated tube should take 18 watts all day long and have a very long life.    I saw a post by my old pal Jim McShane who said the 6P3S-E is really about as tough as a 6L6GC, which would be a 30 watt tube.   He said you could bias them at WELL over 20 watts with no problems.   You might try a quad of the 6P3S-E in your experiment.  As long as they are over 17 watts that seemed to be a sweet spot.   I will try them a bit hotter to around 18 watts.  They are an excellent tube even without the cheap price.   They take a good 50 hours to run in though or more.   I really should get a quad of KT66 to play with, but I have read reports from folks who said they thought the 6P3S-E sounded pretty much as good as their gold lion reissue kt66... so I haven't bothered.   So many tubes.... so little time:)
Pretty much what you said.  IIRC my last ones in another amp weíre right at 17W for stereo use.  Iím VERY familiar with them in guitar amps.  They sing... see the Mayall Beano album and Claptonís tone.  Quintessential British blues. Sweeter than 6L6GC.

Iíll include the 6P3S-E in the trials.  At the price Iíd be kind of dumb not to do so!

Like you said: so many tubes... so little time!

That would be really interesting.  Please post your results.  The more data points the better!  This is in an ST-70 clone?  Octal front end or small tubes?
VTA 12AU7 input board. 

http://www.tubes4hifi.com/VTAcover02.jpg

I have Mullard CV4024 and some 12BH7ís to try along with the 12AU7ís.  I used a combination of Takman metal and carbon film resistors with some 20ppm wirewounds for higher current applications.  Coupling caps are a combo of PIO and Myflex.  Power supply is 630V polypropylene for The primary supply along with the electrolytics resident on the board.  The power TX is the beefier one available from Tubes fo HiFiZine and Triode electronics:

http://www.triodeelectronics.com/mq060.html

Choke is a higher inductance and current Hammond.  I have NOS Mullard 5AR4ís and a rectifier I built from Hexfreds.  Iíll try them both.  All that left of the original is the chassis and output transformers.  I cryoed everything since that is what I do 😁.  I need time to get it all together hopefully this month.  Business is good  :thumb:

When I get back to Albuquerque next week Iíll post some pics.

I have another ST 70 that I want to build the octal front end for to compare with this one.  Like tubes:  so many projects, so little time!
"A man with an experience is never at the mercy of a man with an argument." - Hilmar von Campe

Offline dls123

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Re: My New Don Sachs Model 2 Preamp Unboxing
« Reply #29 on: July 04, 2020, 12:41:53 PM »
I have no experience with either tube - Is there a sonic difference?
Michael.  Iím with Mr. Sachs on the EL34 thing.  Not my favorite tube for audio.  Great in Ďsomeí guitar amps. I much prefer the KT77 over the EL34 for audio.  It could be the tetrode vs pentode thing.  That extra grid gets in the way.  I like KT88ĎS better than 6550ís, too.

My favorite tube for 30 - 35 watt stereo amps are KT66ís.  They have always seemed to do every aspect of the sonic spectrum even handedly.  Iím finishing up a rebuild of a Dyna ST70 with a VTA input board.  Iím using the improved, high current power transformer.  It will handle the heater current those hungry KT66 draw.  Iíll be comparing KT77 and KT66 outputs.  Iím thinking that I already know...

I'll let you know my findings.

I wish I could swing one of Donís amps... but not right now  :(

Hi
So what bias point do you like the KT66 at?   It is a 25 watt tube, so 70% is about 17.5 watts at idle, but then the screens are a few percent, so really about 18 watts should be pretty good.  I may crank the bias a wee bit more by changing a resistor on the bias board and shoot for about 18 watts.   Any real 25 watt rated tube should take 18 watts all day long and have a very long life.    I saw a post by my old pal Jim McShane who said the 6P3S-E is really about as tough as a 6L6GC, which would be a 30 watt tube.   He said you could bias them at WELL over 20 watts with no problems.   You might try a quad of the 6P3S-E in your experiment.  As long as they are over 17 watts that seemed to be a sweet spot.   I will try them a bit hotter to around 18 watts.  They are an excellent tube even without the cheap price.   They take a good 50 hours to run in though or more.   I really should get a quad of KT66 to play with, but I have read reports from folks who said they thought the 6P3S-E sounded pretty much as good as their gold lion reissue kt66... so I haven't bothered.   So many tubes.... so little time:)
Pretty much what you said.  IIRC my last ones in another amp weíre right at 17W for stereo use.  Iím VERY familiar with them in guitar amps.  They sing... see the Mayall Beano album and Claptonís tone.  Quintessential British blues. Sweeter than 6L6GC.

Iíll include the 6P3S-E in the trials.  At the price Iíd be kind of dumb not to do so!

Like you said: so many tubes... so little time!

That would be really interesting.  Please post your results.  The more data points the better!  This is in an ST-70 clone?  Octal front end or small tubes?
VTA 12AU7 input board. 

http://www.tubes4hifi.com/VTAcover02.jpg

I have Mullard CV4024 and some 12BH7ís to try along with the 12AU7ís.  I used a combination of Takman metal and carbon film resistors with some 20ppm wirewounds for higher current applications.  Coupling caps are a combo of PIO and Myflex.  Power supply is 630V polypropylene for The primary supply along with the electrolytics resident on the board.  The power TX is the beefier one available from Tubes fo HiFiZine and Triode electronics:

http://www.triodeelectronics.com/mq060.html

Choke is a higher inductance and current Hammond.  I have NOS Mullard 5AR4ís and a rectifier I built from Hexfreds.  Iíll try them both.  All that left of the original is the chassis and output transformers.  I cryoed everything since that is what I do 😁.  I need time to get it all together hopefully this month.  Business is good  :thumb:

When I get back to Albuquerque next week Iíll post some pics.

I have another ST 70 that I want to build the octal front end for to compare with this one.  Like tubes:  so many projects, so little time!

Cool.  The octal one will sound better:)   Do all your tricks, but use the octal front end.   Problem with the ST70 is that it is power supply limited.  The original version also had a poor driver circuit, but all the replacement boards solve that.  You can only fit so much in that chassis though.   I did one for a guy years ago with the octal front end and it was a nice little amp as long as you didn't push it hard.   I have moved completely away from conventional power supplies, but that is because I decided that I didn't care what things cost.  I would just build it and price it based on what it costs to build and only sell a few of things.   I did build a version of the kt88 amps with full film cap power supplies, dual independent with a choke on each channel and mundorf tube caps.   It was really good.  That said, it cannot carry the lunch of the current version, but you could never fit all of that in the st 70 chassis.   But, all of that said, a souped up st70 is a very nice little musical amp that would give you years of enjoyment with the right speakers.  I bet the 12bh7 will sound better than any 12au7 too.....