Tube Amp Newbie

J

jsmd

New Member
Owner of several working DYNACO solid state pre-amps (PAT4, PAT 5), solid state amps (ST120, ST150, ST400) and speakers (A25 and A35), I got recently a Dynaco PAS3 in excellent condition (mint, no mods and sounds good to me when hooked to the mint ST120 it came with).

This is my first valve/tube preamp.

I don't want to purchase a $600.00 Dynaco ST70 amp to start with. I would prefer to hook the PAS3 to a small (budget) valve/lamp amp to hear whether I hear a sound difference before keeping or selling it.

I was looking at something like Gemtune APPJ PA1501A mini tube amplifier ($180) or similar budget and small-footprint better amp

Any advice, reviews, discussions?
 
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You were smart to start here before purchasing; there are many knowledgeable people on this board. I hate to be the first one to burst your bubble, but purchasing a Gemtune to see what tube audio is all about is like buying Vino Fino to see what wine is all about.

I would start by ensuring that the PAS has been fully rebuilt before putting it into service. Read some posts here on Audiokarma to understand how important it is to updated the unit with new capacitors throughout. If a power supply capacitor fails it can take the power transformer with it. The PAS isn't even fused, so that can lead to a fire. No, that's not overly dramatic: it happened to me.

So, first things first. Spend the $180 to make the PAS reliable, pair it with the solid state amps to get a feel for the tube sound and save your money for a decent amp.
 
I would agree with Pal that putting the PAS into service without having checked out can be a disaster. It may turn out good but unless you know when it was last used for a long time, not just on to check that the tubes are lit. Especially a vintage unit that is in excellent cosmetic shape it would be better to have it checked out first. Don't be too eager to try it out. Your patience will be rewarded.
 
as my signature shows, we're dealing with PAS preamps all the time. It is all very well to try and keep something 'original' but the facts are that at the very least, the electro caps will more than likely have to be replaced. At 40+ years old, those old caps are like a time bomb and at best have shifted in value by quite a lot.
Other areas that should be checked are the conditions of the potentiometers, as over the years the carbon would have worn down by a lot. It may well sound good to you, but you will be pleasantly surprised how much better it will sound with some work and upgrades.
Also, do note, that pretty much most Dynaco units, although not bad designs, were designed and built on a budget and corners were cut to save some $, this applies to both their tube and solid state lines.
Of course, in the end, it is up to you if you want to at least make sure all is good with your PAS and at the very least breath some new life into the all-important power supply.
 
Palustris said:
You were smart to start here before purchasing; there are many knowledgeable people on this board. I hate to be the first one to burst your bubble, but purchasing a Gemtune to see what tube audio is all about is like buying Vino Fino to see what wine is all about.

I would start by ensuring that the PAS has been fully rebuilt before putting it into service. Read some posts here on Audiokarma to understand how important it is to updated the unit with new capacitors throughout. If a power supply capacitor fails it can take the power transformer with it. The PAS isn't even fused, so that can lead to a fire. No, that's not overly dramatic: it happened to me.

So, first things first. Spend the $180 to make the PAS reliable, pair it with the solid state amps to get a feel for the tube sound and save your money for a decent amp.
Click to expand...
NO! You can't do this. The PAS is designed to drive the ST70 which has a 470k Ohm input impedance. If you try it on a SS amp, you will lose a lot of Bass.
I would sell the PAT4 and 5 and get a Dynaco amp.
 
triode17 said:
NO! You can't do this. The PAS is designed to drive the ST70 which has a 470k Ohm input impedance. If you try it on a SS amp, you will lose a lot of Bass.
I would sell the PAT4 and 5 and get a Dynaco amp.
Click to expand...

"NO" might be a bit dramatic. Yes, the PAS was designed to be used with tube amps, but can, of course, be connected to solid state amps. Not a perfect match for sure, but will be quite OK with most solid state amps. It is good enough to check and test it, but for the best results, connecting the PAS to a tube amp will give you the best results.
 
Erhard-Audio said:
"NO" might be a bit dramatic. Yes, the PAS was designed to be used with tube amps, but can, of course, be connected to solid state amps. Not a perfect match for sure, but will be quite OK with most solid state amps. It is good enough to check and test it, but for the best results, connecting the PAS to a tube amp will give you the best results.
Click to expand...
OK, a bit dramatic for a reason. When I first got the PAS3x, I borrowed a set of Beatles Master Recordings to transfer to CD. Well, I did the whole thing driving my Tascam CD recorder with the phono stage of the PAS. Then afterwards I realized that the Bass seemed very low. It was because the Tascam has a 20k Ohm input impedance and the between the PAS output cap and that impedance, it formed a low cut filter at 80 Hz. So, to drive a SS amp. with this preamp may sound underwhelming.
 
You're going to want some very sensitive speakers to be able to use that amp, though I'd suggest getting a kit and assembling that. The Gemtune BL-02 really is about as far down as you want to go.

This would be a really sweet sounding little amp:

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/253432340671

Personally I'd rather assemble one of the Audionote Kondo KSL-M77 kits and pair it with a JLH 1969 Hood amp. Would give amazing sound on a budget ;)
 
triode17 said:
OK, a bit dramatic for a reason. When I first got the PAS3x, I borrowed a set of Beatles Master Recordings to transfer to CD. Well, I did the whole thing driving my Tascam CD recorder with the phono stage of the PAS. Then afterwards I realized that the Bass seemed very low. It was because the Tascam has a 20k Ohm input impedance and the between the PAS output cap and that impedance, it formed a low cut filter at 80 Hz. So, to drive a SS amp. with this preamp may sound underwhelming.
Click to expand...

What am I missing here? I would suspect that anytime you attempt to drive a line source using a phono stage, it will yield way less than good sound quality, not only in the bass frequency. Was this a typo or did you actually run a cd player through the phono stage?
 
nelsress said:
What am I missing here? I would suspect that anytime you attempt to drive a line source using a phono stage, it will yield way less than good sound quality, not only in the bass frequency. Was this a typo or did you actually run a cd player through the phono stage?
Click to expand...
No, I ran the phono stage into the CD recorder to do a transfer. I have since built a stand alone PAS phono stage but added an Aikido output buffer which alleviated the problem. Sounds great, full Bass.
 
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