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+4

peterh

Dale Stevens

audio ken

Bob Latino

8 posters

Preamp for ST70

jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°1

Preamp for ST70

by jeffjmr Fri Sep 11, 2020 8:32 pm

I think I have my ST70 dialed in now and would like to add a preamp. While it doesn’t HAVE to be a Dynaco, I like the affordability and I like to tinker so they seem to be a good choice.

What I can’t seem to determine is the practical differences between the PAT4, PAS4, PAT5 etc. I don’t think I want another tube device like the PAS3 but I am open to suggestions if it makes a significantly better match for the ST70. I like the upgrades readily available for the PAT4.

Any and all input will be appreciated.
Jeff

Dale Stevens: Posts : 206
Join date : 2014-07-06
Age : 75
Location : Loris, SC

Post n°2

Re: Preamp for ST70

by Dale Stevens Sun Sep 13, 2020 1:48 pm

Jeff, may depend on your speakers; What are they? Dale

jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°3

Re: Preamp for ST70

by jeffjmr Sun Sep 13, 2020 2:04 pm

Dale Stevens wrote:Jeff, may depend on your speakers; What are they? Dale

Thanks Dale. For a little while the ST70 is driving a pair of B&W DM605S2, which are 8 ohm nominal with a self-powered bass section. But the ST70 was purchased specifically to drive a pair of 16+ ohm Altec Lansing A5Xs which are nearing restoration completion.

The ST70 is a “factory” built unit from Triode USA with a few insurance mods like the “yellow paper” diode mod to the rectifier tube and an inrush current limiter. All tubes are relatively new JJs. Since my house voltage averages 120 and on some days 123 I’ll be building a bucking transformer. Otherwise no additional mods are being considered until I actually hear the Altecs with this setup. I don’t care for the consumer grade Mitsubishi or Yamaha receivers I have with the ST70. Direct driving from an Apple Airport and a Sony Walkman are sounding better thus my interest in a standalone preamp.

Thanks for any light you can shed on the subject.
Jeff

Guest: Guest

Post n°4

Re: Preamp for ST70

by Guest Sun Sep 13, 2020 5:39 pm

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Last edited by PeterCapo on Mon Nov 30, 2020 4:51 pm; edited 1 time in total

jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°5

Preamp

by jeffjmr Mon Sep 14, 2020 10:58 pm

I am sensitive to the highly subjective nature of audio system sound. A clear picture has not emerged. I was looking more for some comments about glaring issues and reliability, and any technical differences between the models that might be considered important. From what I have read so far, the PAT4 looks like the way to go, but would love to hear from folks who may have experience with more models.

Thanks,
Jeff

peterh: Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden

Post n°6

Re: Preamp for ST70

by peterh Tue Sep 15, 2020 2:41 am

jeffjmr wrote:I am sensitive to the highly subjective nature of audio system sound. A clear picture has not emerged. I was looking more for some comments about glaring issues and reliability, and any technical differences between the models that might be considered important. From what I have read so far, the PAT4 looks like the way to go, but would love to hear from folks who may have experience with more models.

Thanks,
Jeff

An unmolested PAS3/3X is the preffered way. A PAT4 should have the final
transistor replaced before considering. PAT4 is easiest to find in unmolested form.

Guest: Guest

Post n°7

Re: Preamp for ST70

by Guest Tue Sep 15, 2020 4:40 am

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Last edited by PeterCapo on Mon Nov 30, 2020 4:51 pm; edited 1 time in total

Bob Latino: Admin; Posts : 3274
Join date : 2008-11-26
Location : Massachusetts

Post n°8

Re: Preamp for ST70

by Bob Latino Tue Sep 15, 2020 8:27 am

jeffjmr wrote:I think I have my ST70 dialed in now and would like to add a preamp. While it doesn’t HAVE to be a Dynaco, I like the affordability and I like to tinker so they seem to be a good choice.

What I can’t seem to determine is the practical differences between the PAT4, PAS4, PAT5 etc. I don’t think I want another tube device like the PAS3 but I am open to suggestions if it makes a significantly better match for the ST70. I like the upgrades readily available for the PAT4.

Any and all input will be appreciated.
Jeff

Check out Roy Mottram's VTA SP14 preamp (kit or wired) at the link below. This preamp can run with preamps costing in the $4K - $5K range .. Link below ..

VTA SP14 preamp

Bob

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jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°9

Re: Preamp for ST70

by jeffjmr Tue Sep 15, 2020 10:42 pm

Thank you Bob.

That looks like a top notch unit, but is above my budget at the moment.

Also, thanks for this great forum. It has been most informative and helpful.

Jeff

heianshodan likes this post

Dale Stevens: Posts : 206
Join date : 2014-07-06
Age : 75
Location : Loris, SC

Post n°10

Re: Preamp for ST70

by Dale Stevens Wed Sep 16, 2020 10:35 am

Jeff, very nice speakers with high efficiency. If you don't want a tube pre then here's what I have;
A Dynaco PAT5 , solid state, with all new boards and jack strips from UPDATEMYDYNACO. Input to the pre is a dedicated Dell laptop running windows 10 and Spotify then out at the usb port to a Dragon Fly red Dac. The Pat5 is then driving a VTA ST-120 to Klipsch horns. Amazing sound. The laptop also serves as cd player. I'm satisfied so much with this system that no further upgrades are being considered ( at this time , of course ) Dale

Guest: Guest

Post n°11

Re: Preamp for ST70

by Guest Wed Sep 16, 2020 1:30 pm

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Last edited by PeterCapo on Mon Nov 30, 2020 4:51 pm; edited 1 time in total

jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°12

Pat4

by jeffjmr Wed Sep 16, 2020 2:43 pm

PeterCapo wrote:PAT-4 needs to see 100KΩ or higher amplifier load. If it drops below that, the bass progressively rolls off. PAS can also be load sensitive, but the Audio Regenesis documents explain how to address it. Their tone control potentiometers may not be replaceable, so bypassing them may be the best option. If there are issues with their selector switches, then you've got a pretty significant problem to overcome. These are all old age issues, by the way, not design flaws.

If you go with an aftermarket circuit replacement for them, then you've got an altogether different preamp.

Thanks, Peter.

Definitely not interested in any bass rolloff. Already a bit worried that I’m gonna need a sub with the Altecs. Loving my B&Ws with their built-in sub in my bedroom which is significantly smaller than the family room which is where the Altecs are going to be.

So will the ST70 provide the appropriate load to a PAT4? Will installing most or all of the suggested mods to the PAT4 or the PAS3 address that issue? Also, not sure I won’t wish I had tone control in the larger room.

Coincidentally I had seen the Akitika and like it. A bit more even in kit form than I think a fully modded/updated PAS3 or PAT4 would run but intriguing nonetheless.

Jeff

jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°13

Re: Preamp for ST70

by jeffjmr Wed Sep 16, 2020 2:58 pm

peterh wrote:
An unmolested PAS3/3X is the preffered way. A PAT4 should have the final
transistor replaced before considering. PAT4 is easiest to find in unmolested form.

Hmmm. Unmolested PAS3s are not plentiful. Does that mean you suggest no upgrades to the original?

Same question for PAT4, which are easier to find.

Jeff

Guest: Guest

Post n°14

Re: Preamp for ST70

by Guest Wed Sep 16, 2020 3:20 pm

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Last edited by PeterCapo on Mon Nov 30, 2020 5:53 pm; edited 1 time in total

peterh: Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden

Post n°15

Re: Preamp for ST70

by peterh Wed Sep 16, 2020 3:33 pm

jeffjmr wrote:

peterh wrote:
An unmolested PAS3/3X is the preffered way. A PAT4 should have the final
transistor replaced before considering. PAT4 is easiest to find in unmolested form.

Hmmm. Unmolested PAS3s are not plentiful. Does that mean you suggest no upgrades to the original?

Same question for PAT4, which are easier to find.

Jeff

By unmolested i mean needed replacements ( tubes pots etc, possibly power supply)
Observe that heavily modified PAS might be upgraded to original configuration
as boards are available that conforms to the original schematic.

Both PAS3 and PAT4/5 will be perfectly fine to use for a ST70.

audio ken: Posts : 13
Join date : 2020-09-08

Post n°16

Re: Preamp for ST70

by audio ken Fri Oct 02, 2020 5:16 pm

I have my st70 hooked up to an Akitika preamp with phono board and remote and its exceptional for its price and also fun to build. Dan is a nice guy and is keen to talk live and troubleshoot.
Soundstage is huge and detailed but not analytical. Also has bass and treble to adjust to your ears.

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Dale Stevens: Posts : 206
Join date : 2014-07-06
Age : 75
Location : Loris, SC

Post n°17

Re: Preamp for ST70

by Dale Stevens Sat Oct 03, 2020 1:16 pm

Jeff, two things; Are you gonna run a phono pre section? And I'm not clear if you're talking bout the PAT 4 solid state? or PAT 4 tube ?

Those Altecs you will be pushing is going to give you all base you want. Also, the Akitika upgrdes I did to a PAT 5 brought the sound stage out maybe 1-2 feet. Amazing. Dale

peterh: Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden

Post n°18

Re: Preamp for ST70

by peterh Sat Oct 03, 2020 1:21 pm

Dale Stevens wrote:Jeff, two things; Are you gonna run a phono pre section? And I'm not clear if you're talking bout the PAT 4 solid state? or PAT 4 tube ?

Those Altecs you will be pushing is going to give you all base you want. Also, the Akitika upgrdes I did to a PAT 5 brought the sound stage out maybe 1-2 feet. Amazing. Dale

Dynaco PAT 4 is solid state. PAS 4 is tubed ( and rare)
My view of the PAT 4 riaa stage is good, nothing to fear.

ttownscott: Posts : 40
Join date : 2018-07-31
Age : 60
Location : Tacoma, WA

Post n°19

Re: Preamp for ST70

by ttownscott Wed Oct 07, 2020 6:53 pm

vinylb wrote:I have my st70 hooked up to an Akitika preamp with phono board and remote and its exceptional for its price and also fun to build. Dan is a nice guy and is keen to talk live and troubleshoot.
Soundstage is huge and detailed but not analytical. Also has bass and treble to adjust to your ears.

I second this. I have this exact same setup for a while. Now my ST-70 pre-amp is just an amazon echo link for steaming in the living room. But I still use the Akitika in my listening room. What is nice about it beyond what vinylb said is that it also has switchable outputs, so I can choose between my Dynaco ST-150 or my VTA driver MK-III's.
Oh, and the bass/trebel is defeatable if you want.

Enjoy the journey!

I'm building a Bruce Rozenblit Transcendent Sound "The Slider" but it's taking my a while to finish it up so I don't know how it sounds yet.

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Hops: Posts : 87
Join date : 2019-09-21
Location : South Detroit, Michigan

Post n°20

Re: Preamp for ST70

by Hops Wed Oct 07, 2020 8:02 pm

""I'm building a Bruce Rozenblit Transcendent Sound "The Slider" but it's taking my a while to finish it up so I don't know how it sounds yet". [/quote]

Let us know how the Slider sounds. The Transcendent Sound writeup sounds interesting. I don't need a preamp, but in a few years i may convince myself I do...

heianshodan likes this post

jeffjmr: Posts : 44
Join date : 2020-08-22

Post n°21

Preamp

by jeffjmr Tue Oct 13, 2020 11:52 pm

Dale Stevens wrote:Jeff, two things; Are you gonna run a phono pre section? And I'm not clear if you're talking bout the PAT 4 solid state? or PAT 4 tube ?

Those Altecs you will be pushing is going to give you all base you want. Also, the Akitika upgrdes I did to a PAT 5 brought the sound stage out maybe 1-2 feet. Amazing. Dale

Thanks Dale.

I do have a turntable, but not much vinyl that I haven’t also got on CD (don’t roast me, I know there are a few dupes that the CD can’t hold a candle to the vinyl). So I wouldn’t mind having a phono option.

I listen to a lot of pipe organ music. My B&W 605S2s will reproduce C1 (33hz) albeit down a few db, and even have a hint of C0 on the few recordings that have it. I remain hopeful the VOTTs will get close but my understanding is quite a steep rolloff starting at 40hz. I have tested the ST70 and it is quite good to almost 10hz, so I am delighted with the purchase. Coupled with the B&Ws with their built in sub, I’m in organ nirvana.

I learned something recently that minimizes the urgency for a preamp. I was using a Walkman for a CD player temporarily until the ST70 moves from my bedroom to the family room where the VOTTs will reside. Playing through my Mitsubishi DA-R35 as a preamp only there was no punch. Blamed it on the DA-R35 until I learned how inferior the DACs are on the Walkmans; built in compression apparently since they are designed for headphones. Played my Flim & the BBs on a REAL CD player and all was good. Supposedly my Yamaha receiver in the family room will perform even better as a preamp so I will be waiting until the VOTTs are ready to roll with the ST70 before I make any moves. Other than the bass question, since the VOTTs are even more efficient than the B&Ws, I suspect the ST70 will do just fine.

Jeff

Roy Mottram: Admin; Posts : 1839
Join date : 2008-11-30

Post n°22

Re: Preamp for ST70

by Roy Mottram Mon Oct 19, 2020 10:59 pm

if you're open to a tube preamp, you can't beat the Tubes4HiFi SP8 for either price or performance.
For about the same money, get a PAT4 and do ALL of the UpdateMyDynaco mods, or buy an AKITAKA PR-102 ready to go.

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Re: Preamp for ST70

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