Thursday, September 2, 2021

Short Review: Dynaco A-25 VW loudspeakers

 

The Dynaco A-25 is a 2-way bass-reflex loaded speaker sporting a 10" woofer and a soft dome tweeter.  I picked up this pair at a half-off day estate sale.  I wasn't, however, expecting much since my experience with vintage speakers has been mixed.

To my surprise, the A-25s really capture the midrange in a nice and pleasing manner.  Yes my (larger) KEF R500s can pump out more bass & treble, do dynamics better, and throw a deeper soundstage; but still these old Dynacos have a certain magic that is hard for me to put my finger on.  Perhaps it is the nice all tubed front end I have, but these vintage speakers are just relaxing to listen to.  They do jazz really, really well; hard rock not as nicely due to their dynamic limitations.

So if you see a pair of A-25s for a good price, check them out.  They would be great in a small system with a low-powered tube or Class A solid-state amp; along with a suitable preamplifier.  They don't do all of the hi-fi tricks of something more exotic, but, like the Dynaco PAS and Stereo 70, capture the midrange depth and bloom a lot better than many, many modern budget components.

Thursday, March 11, 2021

Turntable Basics and Buyers Guide


 Here is a short video I made about buying turntables; geared toward beginners or anyone looking to upgrade to a new record player.

Friday, February 26, 2021

Review: a Frankenstein Eico ST-70 tube amplifier

 I bought this strange modified amplifier on Ebay. It looks as if someone took a stock integrated and modified it to be a basic power amp. Gone is the normal set of controls on the front plate, replaced with a generic black panel and power indicator light.


[​IMG] 
A peek on top of the grille - what is inside?

[​IMG]

Of course you know - you read the title of this post! Someone took an Eico ST-70, removed the preamplifier portion and converted it to use 5881s instead of the stock 7591s.

[​IMG]

Since I didn't have any 5881s on hand, I modified this amplifier to use the military 6AR6. Since the 6AR6 has a completely different pinout (and bias points!) it took an entire rewire of the output stage, along with more negative bias than the stock circuit.

[​IMG]

I also changed the power supply with new electrolytic capacitors for the main bucket, 6SN7 phase-splitters, and 12AX7 input tube. I also added a little 1.5H Dynaco choke to reduce the B+ ripple. After a little troubleshooting, and bias modifications, I finally got this amp to work; with 40mA per output tube. 

So how does this pentode output Frankenstein weird output tube sound? Even with old Russian 6N8S tubes, surprisingly good. Bass extension - with the large output transformers - is really deep. And there is the old tube midrange and smooth treble thing happening. Maybe it's been too long with an SS (Aleph J clone) amplifier, but this little push-pull tube amp is quite magical.

Chet Baker Sings, for example, really is holographic - for a mono recording - with his voice and trumpet sounding natural and forward. Compared to the Aleph J solid-state amplifier, music is more relaxed but, at the same time, more dynamic. The tube amplifier sounds way more powerful than its approximate 30 or 35Ws per channel.

I'm surprised that the KEF R500s work so well with this vintage Frankenstein; you never really know what you are going to get with modern speakers.

Once I get over the excitement of having a new amplifier, I plug in some old Zenith 6SN7s that I have on hand. Maybe things will get even better-better.

 

 

Thursday, January 28, 2021

Short Review: a Hafler SE-120 amplifier

 


This is a Rockford Corp era amplifier good for 60WPC; made to be _not_ user friendly versus the kit amps of yore. This one looks to have been around the block though some face plate cleaning helped to remove a bit of yellowing.

The amp sounded a little tired so I went in and replace the main electrolytic capacitors, the input caps, and two of the smaller power supply rail caps. Needless to say getting to the underside was very frustrating with the number of screws, removing the output mosfets from the heatsink, and pinching the nylon standoffs to free the PCB. In the end I also checked the bias, cleaned the RCAs and speaker jacks.

After my work: Overall it is a nice sounding budget amp - to my ears a little warmer than something like an Adcom 535. Good bass, and more of a rock 'n' roll sound than say the Musical Fidelity. My Aleph J clone is a bit more refined with a touch more detail and "space" around the instruments. Though all three amps are "warm" none of them exactly sound like a tube amp. An old Frankenstein Eico ST70 - modified to be a power amp with 6AR6 output tubes - I have kicking around has a presence and sense of dynamics that I just don't hear with these (admittedly low powered) SS amps. Nonetheless I could live with the Hafler if I really needed a compact amplifier.

Thursday, January 21, 2021

Short Review: the Musical Fidelity A1 integrated amplifier

Musical Fidelity A1
This is one of those little amplifiers that I've always wanted to hear for years but didn't get a chance until today.  You probably know the history: designed by Tim de Paravicini, may he rest in peace, this integrated was very popular in the mid-80s and very hot running, but providing that Class A magic for a relative bargain.  It was apparently Musical Fidelity's biggest seller.  It wasn't without its well-documented issues with noisy volume controls and switching, but this particular unit seemed to have held up quite well over the years.

How does it sound?  Like my Aleph J clone, very Class A.  But also very British polite.  I would say the phono stage doesn't quite stack up to my (much more expensive) tubed Audio Research SP8, but the amplification portion was a real surprise.  In my small/medium sized listening room it had no problem driving the 88dB efficinet KEF R500 towers.  Lower bass, like on my UK pressing of the Bee Gees - Trafalgar - was deep and controlled.  The midrange is quite magical, but the sense of dynamics work better with Chet Baker jazz albums then say something like AC/DC.  There is a distinct lack of glare and edge in the treble, the overall sound hewing further to the warmer side than neutral.

So overall a nice little integrated - that runs so hot that after an hour of use I can only hold my hand on top for a half a second before I fear getting burned.  Not a good napping place for those with cats, or children with curious hands!  Nonetheless, back in the past I would have been very happy with this amplifier since it images quite well and does a very good job with vocals.  And it is the sort of sound that makes me search through my stack of records and pull out some old favorites.  Very much a music lover's amp than audiophile-extremis.
This is one of those little amplifiers that I've always wanted to hear for years but didn't get a chance until today.  You probably know the history: designed by Tim de Paravicini, may he rest in peace, this integrated was very popular in the mid-80s and very hot running, but providing that Class A magic for a relative bargain.  It was apparently Musical Fidelity's biggest seller.  It wasn't without its well-documented issues with noisy volume controls and switching, but this particular unit seemed to have held up quite well over the years.

How does it sound?  Like my Aleph J clone, very Class A.  But also very British polite.  I would say the phono stage doesn't quite stack up to my (much more expensive) tubed Audio Research SP8, but the amplification portion was a real surprise.  In my small/medium sized listening room it had no problem driving the 88dB efficinet KEF R500 towers.  Lower bass, like on my UK pressing of the Bee Gees - Trafalgar - was deep and controlled.  The midrange is quite magical, but the sense of dynamics work better with Chet Baker jazz albums then say something like AC/DC.  There is a distinct lack of glare and edge in the treble, the overall sound hewing further to the warmer side than neutral.

So overall a nice little integrated - that runs so hot that after an hour of use I can only hold my hand on top for a half a second before I fear getting burned.  Not a good napping place for those with cats, or children with curious hands!  Nonetheless, back in the past I would have been very happy with this amplifier since it images quite well and does a very good job with vocals.  And it is the sort of sound that makes me search through my stack of records and pull out some old favorites.  Very much a music lover's amp than audiophile-extremis.

 

This is one of those little amplifiers that I've always wanted to hear for years but didn't get a chance until today. You probably know the history: designed by Tim de Paravicini, may he rest in peace, this integrated was very popular in the mid-80s and very hot running, but providing that Class A magic for a relative bargain. It was apparently Musical Fidelity's biggest seller. It wasn't without its well-documented issues with noisy volume controls and switching, but this particular unit seemed to have held up quite well over the years.

How does it sound? Like my Aleph J clone, very Class A. But also very British polite. I would say the phono stage doesn't quite stack up to my (much more expensive) tubed Audio Research SP8, but the amplification portion was a real surprise. In my small/medium sized listening room it had no problem driving the 88dB efficient KEF R500 towers. Lower bass, like on my UK pressing of the Bee Gees - Trafalgar - was deep and controlled. The midrange is quite magical, but the sense of dynamics work better with Chet Baker jazz albums then say something like AC/DC. There is a distinct lack of glare and edge in the treble, the overall sound hewing further to the warmer side than neutral.

So overall a nice little integrated - that runs so hot that after an hour of use I can only hold my hand on top for a half a second before I fear getting burned. Not a good napping place for those with cats, or children with curious hands! Nonetheless, back in the past I would have been very happy with this amplifier since it images quite well and does a very good job with vocals. And it is the sort of sound that makes me search through my stack of records and pull out some old favorites. Very much a music lover's amp than audiophile-extremis.

Review System:
Thorens TD-309 turntable with Ortofon 2M Bronze
Cardas Iridium interconnects
KEF R500 speakers with Cardas Twinlink speaker cable