I built my first amplifier, the Dynaco SCA-80Q kit back around 1976. It's still working in my basement. Apparently it's now worth more than double what I paid for it! There are all sorts of upgrade kits available for it. Amazing. I guess if you keep your junk long enough it becomes valuable again.

 

I guess if you keep your junk long enough it becomes valuable again.

I threw away dozens of perfectly good CRTs a few years ago. Now I regret it.

 

A few eons ago I build an Allied Knight-Kit tube integrated audio amplifier with preamp (here).

I build an earlier, walnut-case version of that for my parents. I still have the brass front panel as a memento.

ak

 

Probably they just tested it with a signal generator at 1kHz.

Still hard to believe that no designer ever listened to it and noticed the problem.

Was it built on tag-strip or on a pcb?

As I recall, it was tag strip with no PCB.

 

My A/V receivers are too modern and no longer have ports for phono input. I'm looking for a reasonable solution to get my turntable phono output up to line level.

My son-in-laws are both riding the vinyl trend and since I still have my turntable and vinyls, I'd like to put them to use so we can share that fun. My old vinyl LPs are certainly classics.

I thought finding a RIAA pre-amp would be easy but wow, it's quite a rabbit hole. There are tons of options and prices run from under $20 to goofy audiophiles offering products for hundreds of dollars. I'm sure the components included in older equipment got the job done for a few dollars or less. Maybe that's apples and oranges to those audiophiles but I'm skeptical that spending more than say $50 would give a noticeable improvement.

I'm looking hard at this one:
https://www.amazon.com/Pyle-Phono-Turntable-Preamp-Preamplifier/dp/B004HJ1TTQ

Do you have any experience or insight?

Background literature:
https://sound-au.com/project06.htm
https://www.andyc.diy-audio-engineering.org/phono-preamp/index.html

Hi there,

You can use filters such as the Reg Williamson filter or the Jung Lipshitz filter to mimic a phono cartridge, and that way you can test your preamp to see if you get a flat response. You can also test any RIAA filters you care to build yourself this way.
Those two are inverse RIAA filters, the first is very simple with just maybe 5 components, the second is more complex and unfortunately uses two inductors but it's more accurate and used as a standard. They are both passive filters though so a little easier to build than the op amp types.
The idea is to send a signal to the inverse filter, then send the output of that to the device to be tested such as preamp or home made RIAA filter. Since the input will be a signal generator with flat response over a test frequency range, if the output of the tested device is flat then that means it has a proper RIAA filter for use with real phonograph cartridges.

I don't think I have read or heard anyone talk about RIAA for probably 20 years. In the old days of the long-long ago, we'd talk about this from time to time because everyone had at least one phonograph. One of my girlfriends back then had a portable battery powered phonograph! She liked to take it in the car when we went somewhere so she could listen to LP records while I drove the car.

 

She liked to take it in the car when we went somewhere so she could listen to LP records while I drove the car.

It didn't skip from road bumps?

 

Still hard to believe that no designer ever listened to it and noticed the problem.
As I recall, it was tag strip with no PCB.

I can believe that. Easy to miss a capacitor off a piece of tagstrip that already has a one component between the two tags in question.
A production engineer will have written a test procedure. Time & Motion will have decided that a signal generator test would be quicker than playing a real record on a real turntable, and someone less skilled can test it if it just has to produce a signal of a stipulated amplitude. It depends on the skills of the production engineer. Did he think that if there is an output signal it means that everything is assembled correctly? An easy mistake to make if he didn't design it. A reverse RIAA network and a second test at 10kHz would have done it.

 

Easy to miss a capacitor off a piece of tagstrip that already has a one component between the two tags in question.

True.
But the capacitor was missing on the schematic that came with the amp, so it was a design error, not assembly.
Remember this was a kit that I assembled.
And I was thus both the assembly and test engineer.

 

Remember this was a kit that I assembled.

That point appears to have eluded me. Please accept my apologies for casting aspersions on your construction ability.
There is a possible explanation: The RIAA curve has not always been standard, there are a plethora of other curves, not all of which have a treble pre-emphasis which has to be removed in the preamp
https://www.tempoelectric.com/78_RPM_EQ_Settings_by_Label.pdf

 

The RIAA curve has not always been standard, there are a plethora of other curves, not all of which have a treble pre-emphasis which has to be removed in the preamp

Well, I bult the stereo amp circa 1960, and the RIAA equalization curve was standardized in the mid 1950's so I would think the amp should have been designed for that.

 

It didn't skip from road bumps?

Hi,

That's what I thought would happen, but it tracked very well. I'm not sure how it did that and I didn't check it out at the time which was more than 40 years ago. Maybe I'll look it up see what I can find.
She was quite a looker too if anyone saw her walking down the street they would certainly think she was a fashion model. Unfortunately, she had an attitude to match.
I thought it was kind of cute though that she loved her records so much she went through all that trouble, and I think it used D size batteries too.

LATER...
First one I found:
Amazon.com: Vinyl Record Player, 3 Speeds Suitcase Portable Record Player with Built-in Speakers, Vintage Belt Driven Turntable with RCA Output/Headphone/Aux in Jack/45 Adapter Blue : Electronics

It says it has a special suspension "isolation feet" which helps with vibrations. I guess the designers thought that would be a problem.
It could have been very similar to that one but I can't remember that much about it now.

I'm not sure if that one runs on batteries too but this one does:
Amazon.com: Victor Metro Plus Battery-Powered Bluetooth Suitcase Turntable | 3-Speed Vinyl Record Player with Built-in Stereo Speakers, Rechargeable Battery, RCA Output, Aux Input, and 45 RPM Adaptor, VSRP-850B : Electronics

I can imagine that they have the inside part isolated from the case itself so they can provide some shock absorbers or something.

 

it tracked very well. I'm not sure how it did that

If the tone arm is well balanced in both axes at the pivot point, then movement will not tend to cause the arm to move or skip.

She was quite a looker too if anyone saw her walking down the street they would certainly think she was a fashion model. Unfortunately, she had an attitude to match.

And when she lost her looks, she probably still had the attitude.

 

I am guessing that I missed the subject change somehow.
Portable record players did use balanced tone arms and much better bearings.

 

We stayed in an AirBnB in Idaho this spring. There was a record collection and a small portable record player. None of us had spun vinyl in years, so it was fun to give it a go. Sound quality was awful, unfortunately.

 

Sound quality was awful, unfortunately.

Mediocre sound was tolerated back when the standard was AM radio.

 

Mediocre sound was tolerated back when the standard was AM radio.

Didn't Bill Gates say something about no one needing more than 10 kHz?

ak

 

Didn't Bill Gates say something bout no one needing more than 10 kHz?

ak

He did say that no piece of software should need more than 640k of RAM.

 

Didn't Bill Gates say something bout no one needing more than 10 kHz?

If you are referring to AM radio, it's upper frequency range was limited to 5kHz.

 

He did say that no piece of software should need more than 640k of RAM.

That's interesting because I ran programs for years with just 64k of RAM. That's 64*1024 bytes or if you want to call it 64000 that's ok too. That was using a Z80 CPU and black and green graphics on a CRT screen.
It's the 'advance' in graphics I think that led to much higher memory use. If we had only 64k today, the computer would not even be able to start I bet. That, and developers get carried away with graphics instead of good functionality.

 

He did say that no piece of software should need more than 640k of RAM.

Did he?